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The following rules cover about 95% of the decisions that application
developers and deployers must make about where to place class and resource
files to make them available to web applications:
- For classes and resources specific to a particular web application,
place unpacked classes and resources under
/WEB-INF/classe
of your web application archive, or place JAR files containing those
classes and resources under /WEB-INF/lib of your web
application archive.
- For classes and resources that must be shared across all web applications,
place unpacked classes and resources under
$CATALINA_HOME/classes , or place JAR files containing those
classes and resources under $CATALINA_HOME/lib .
|
Overview |
Like many server applications, Tomcat 4 installs a variety of class loaders
(that is, classes that implement java.lang.ClassLoader ) to allow
different portions of the container, and the web applications running on the
container, to have access to different repositories of available classes and
resources. This mechanism is used to provide the functionality defined in the
Servlet Specification, version 2.3 -- in particular, Sections 9.4 and 9.6.
In a Java 2 (that is, JDK 1.2 or later) environment, class loaders are
arranged in a parent-child tree. Normally, when a class loader is asked to
load a particular class or resource, it delegates the request to a parent
class loader first, and then looks in its own repositories only if the parent
class loader(s) cannot find the requested class or resource. The model for
web application class loaders differs slightly from this, as discussed below,
but the main principles are the same.
When Tomcat 4 is started, it creates a set of class loaders that are
organized into the following parent-child relationships, where the parent
class loader is above the child class loader:
, Section 12. For a more introductory level
document for web application developers as well as administrators, see
(FIXME - link to backgrounder on container managed security
to be provided).
For information about utilizing the Single Sign On feature of
Tomcat 4 (allowing a user to authenticate themselves once across the entire
set of web applications associated with a virtual host), see
here.
A Realm is a "database" of usernames and passwords that
identify valid users of a web application (or set of web applications), plus
an enumeration of the list of roles associated with each valid user.
You can think of roles as similar to groups in Unix-like operating
systems, because access to specific web application resources is granted to
all users possessing a particular role (rather than enumerating the list of
associated usernames). A particular user can have any number of roles
associated with their username.
Although the Servlet Specification describes a portable mechanism for
applications to declare their security requirements (in the
web.xml deployment descriptor), there is no portable API
defining the interface between a servlet container and the associated user
and role information. In many cases, however, it is desireable to "connect"
a servlet container to some existing authentication database or mechanism
that already exists in the production environment. Therefore, Tomcat 4
defines a Java interface (org.apache.catalina.Realm) that
can be implemented by "plug in" components to establish this connection.
Three standard plug-ins are provided, supporting connection to three different
sources of authentication information:
JDBCRealm - Accesses authentication information
stored in a relational database, accessed via a JDBC driver.
JNDIRealm - Accesses authentication information
stored in an LDAP based directory server, accessed via a JNDI provider.
MemoryRealm - Accesses authentication
information stored in an in-memory object collection, which is initialized
from an XML document (conf/tomcat-users.xml).
It is also possible to write your own Realm implementation,
and integrate it with Tomcat 4. However, doing this is beyond the scope of
this document. See (FIXME - reference to developer stuff)
for more information.
Before getting into the details of the standard Realm implementations, it is
important to understand, in general terms, how a Realm is configured. In
general, you will be adding an XML element to your conf/server.xml
configuration file, that looks something like this:
<Realm className="... class name for this implementation"
... other attributes for this implementation .../>
The <Realm> element can be nested inside one of three
different elements, which has a direct impact on the "scope" of that Realm
(i.e. which web applications will share the same authentication information):
Inside an <Engine> element - This Realm will be shared
across ALL web applications on ALL virtual hosts, UNLESS it is overridden
by a Realm element nested inside a subordinate <Host>
or <Context> element.
Inside a <Host> element - This Realm will be shared across
ALL web applications for THIS virtual host, UNLESS it is overridden
by a Realm element nested inside a subordinate <Context>
element.
Inside a <Context> element - This Realm will be used ONLY
for THIS web application.
Introduction
JDBCRealm is an implementation of the Tomcat 4
Realm interface that looks up users in a relational database
accessed via a JDBC driver. There is substantial configuration flexibility
that lets you adapt to existing table and column names, as long as your
database structure conforms to the following requirements:
There must be a table, referenced below as the users table,
that contains one row for every valid user that this Realm
should recognize.
The users table must contain at least two columns (it may
contain more if your existing applications required it):
Username to be recognized by Tomcat when the user logs in.
Password to be recognized by Tomcat when the user logs in.
This value may in cleartext or digested - see below for more
information.
There must be a table, referenced below as the user roles table,
that contains one row for every valid role that is assigned to a
particular user. It is legal for a user to have zero, one, or more than
one valid role.
The user roles table must contain at least two columns (it may
contain more if your existing applications required it):
Username to be recognized by Tomcat (same value as is specified
in the users table).
Role name of a valid role associated with this user.
Quick Start
To set up Tomcat to use JDBCRealm, you will need to follow these steps:
If you have not yet done so, create tables and columns in your database
that conform to the requirements described above.
Configure a database username and password for use by Tomcat, that has
at least read only access to the tables described above. (Tomcat will
never attempt to write to these tables.)
Place a copy of the JDBC driver you will be using inside the
$CATALINA_HOME/server/lib directory (if you do not need it
visible to web applications) or $CATALINA_HOME/common/lib
(if it will be used both by Tomcat 4 and by your apps).
Note that only JAR files are recognized!
Set up a <Realm> element, as described below, in your
$CATALINA_HOME/conf/server.xml file.
Restart Tomcat 4 if it is already running.
Realm Element Attributes
To configure JDBCRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.JDBCRealm" here.
The database username used to establish a JDBC connection.
The database password used to establish a JDBC connection.
The database URL used to establish a JDBC connection.
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
The fully qualified Java class name of the JDBC driver to be used.
Consult the documentation for your JDBC driver for the appropriate
value.
The name of the column, in the user roles table, that
contains the name of a role assigned to this user.
The name of the column, in the users table, that contains
the password for this user (either in clear text, or digested if the
digest attribute is set).
The name of the column, in the users and user roles
tables, that contains the username of this user.
The name of the table that contains one row for each role
assigned to a particular username. This table must include at
least the columns named by the userNameCol and
roleNameCol attributes.
The name of the table that contains one row for each username
to be recognized by Tomcat. This table must include at least the columns
named by the userNameCol and userCredCol
attributes.
Example
An example SQL script to create the needed tables might look something
like this (adapt the syntax as required for your particular database):
create table users (
user_name varchar(15) not null primary key,
user_pass varchar(15) not null
);
create table user_roles (
user_name varchar(15) not null,
role_name varchar(15) not null,
primary key (user_name, role_name)
);
Example Realm elements are included (commented out) in the
default $CATALINA_HOME/conf/server.xml file. Here's an example
for using a MySQL database called "authority", configured with the tables
described above, and accessed with username "dbuser" and password "dbpass":
<Realm className="org.apache.catalina.realm.JDBCRealm" debug="99"
driverName="org.gjt.mm.mysql.Driver"
connectionURL="jdbc:mysql://localhost/authority?user=dbuser;password=dbpass"
userTable="users" userNameCol="user_name" userCredCol="user_pass"
userRoleTable="user_roles" roleNameCol="role_name"/>
Additional Notes
JDBCRealm operates according to the following rules:
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm. Thus, any changes you have made to the database
directly (new users, changed passwords or roles, etc.) will be immediately
reflected.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser). Any changes to the database information for an
already authenticated user will not be reflected until
the next time that user logs on again.
Administering the information in the users and user roles
table is the responsibility of your own applications. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
Introduction
JNDIRealm is an implementation of the Tomcat 4
Realm interface that looks up users in a directory server
accessed by a JNDI provider (typically, the standard LDAP provider that
is available with the JNDI API classes). There is substantial configuration
flexibility that lets you adapt to the existing schema inside your directory
server, as long as it conforms to the following requirements:
Each user that can be authenticated is represented by an individual
element in the top level DirContext that is accessed
via the connectionURL attribute.
The user element must have the following characteristics:
The distinguished name (dn) attribute of this element
contains the username that is presented for authentication.
There must be an attribute (identified by the userPassword
attribute of our Realm element) that contains the user's
password, either in clear text or digested (see below for more info).
Each group of users that has been assigned a particular role is
represented by an individual element in the top level
DirContext that is accessed via the
connectionURL attribute.
The user group element must have the following characteristics:
The set of all possible groups of interest can be selected by an LDAP
search pattern configured by the roleSearch attribute
of our Realm element.
The roleSearch pattern optionally includes pattern
replacements "{0}" for the distinguished name, and/or "{1} for the
username, of the authenticated user for which roles will be
retrieved.
The roleBase attribute can be set to the element that
is the base of the search for matching roles. If not specified,
the entire directory context will be searched.
The roleSubtree attribute can be set to true
if you wish to search the entire subtree of the directory context.
The default value of false requests a search of only the
current level.
The element includes an attribute (whose name is configured by the
roleName attribute of our Realm element)
containing the name of the role represented by this element.
There must be an administrator username and password that Tomcat can
use to establish a connection to the directory server, with at least
read-only access to the information described above. A future
version of Tomcat will support an option to use the user's username and
password to attempt this connection.
Quick Start
To set up Tomcat to use JNDIRealm, you will need to follow these steps:
Make sure your directory server is configured with a schema that matches
the requirements listed above.
Configure a username and password for use by Tomcat, that has
at least read only access to the information described above. (Tomcat will
never attempt to modify this information.)
Place a copy of the JNDI driver you will be using (typically
ldap.jar available with JNDI) inside the
$CATALINA_HOME/server/lib directory (if you do not need it
visible to web applications) or $CATALINA_HOME/common/lib
(if it will be used both by Tomcat 4 and by your apps).
Set up a <Realm> element, as described below, in your
$CATALINA_HOME/conf/server.xml file.
Restart Tomcat 4 if it is already running.
Realm Element Attributes
To configure JNDIRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.JDBCRealm" here.
The directory server username used to establish a JNDI connection.
The directory server password used to establish a JNDI connection.
The directory server URL used to establish a JNDI connection.
The fully qualified Java class name of the JNDI context factory to be
used for this connection. By default, the standard JNDI LDAP provider
is used (com.sun.jndi.ldap.LdapCtxFactory).
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
The base element for role searches. If not specified, the top level
element in the directory context will be used.
The name of the directory server attribute containing the role name.
An LDAP search pattern for selecting roles in this Realm, following the
syntax supported by the java.text.MessageFormat class. Use
{0} to substitute in the distinguished name of the user you
want roles for, and/or {1} to substitute in the username of
the user you want roles for.
Set to true if you want role searches to search subtrees
of the element selected by roleBase. The default value of
false causes only the top level element to be searched.
The name of the directory server attribute (in the user element) that
contains the cleartext or digested user password (depending on the setting
of the digest attribute).
An LDAP search pattern for selecting users in this Realm, following the
syntax supported by the java.text.MessageFormat class. Use
{0} to substitute in the distinguished name of the user you
want to select.
Example
Creation of the appropriate schema in your directory server is beyond the
scope of this document, because it is unique to each directory server
implementation. In the examples below, we will assume that you are using a
distribution of the OpenLDAP directory server (version 2.0.11 or later), which
can be downloaded from
http://www.openldap.org. Assume that
your slapd.conf file contains the following settings
(among others):
database ldbm
suffix dc="mycompany",dc="com"
rootdn "cn=Manager,dc=mycompany,dc=com"
rootpw secret
These settings help us identify values for the values to be specified for
connectionName, and connectionPassword, and we
will assume for connectionURL that the directory server runs on
the same machine as Tomcat. See
http://java.sun.com/products/jndi/docs.html
for more information about configuring and using the JNDI LDAP provider.
Next, assume that this directory server has been populated with elements
as shown below (in LDIF format), which define the same users and roles
as the default $CATALINA_HOME/conf/tomcat-users.xml does for
MemoryRealm:
# Define a user named 'tomcat'
dn: cn=tomcat,dc=mycompany,dc=com
cn: tomcat
userPassword: tomcat
sn: Tomcat User
objectClass: person
# Define a user named 'role1'
dn: cn=role1,dc=mycompany,dc=com
cn: role1
userPassword: tomcat
sn: Role1 User
objectClass: person
# Define a user named 'both'
dn: cn=both,dc=mycompany,dc=com
cn: both
userPassword: tomcat
sn: Both User
objectClass: person
# Define an entry to base role searches on
dn: dc=roles,dc=mycompany,dc=com
cn: roles
objectClass: person
sn: Roles Entry
# Define all members of the 'tomcat' role
dn: cn=tomcat,dc=roles,dc=mycompany,dc=com
cn: tomcat
objectClass: groupOfUniqueNames
uniqueMember: cn=tomcat,dc=mycompany,dc=com
uniqueMember: cn=both,dc=mycompany,dc=com
# Define all members of the 'role1' role
dn: cn=role1,dc=roles,dc=mycompany,dc=com
cn: role1
objectClass: groupOfUniqueNames
uniqueMember: cn=role1,dc=mycompany,dc=com
uniqueMember: cn=both,dc=mycompany,dc=com
An example Realm element for the OpenLDAP directory server
configured as described above might look like this:
<Realm className="org.apache.catalina.realm.JNDIRealm" debug="99"
connectionName="cn=Manager,dc=mycompany,dc=com"
connectionPassword="secret"
connectionURL="ldap://localhost:389"
roleBase="dc=roles,dc=mcclan,dc=net"
roleName="cn"
roleSearch="(uniqueMember={0})"
roleSubtree="false"
userPassword="userPassword"
userPattern="cn={0},dc=mycompany,dc=com"
/>
Additional Notes
JNDIRealm operates according to the following rules:
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm. Thus, any changes you have made to the database
directly (new users, changed passwords or roles, etc.) will be immediately
reflected.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser). Any changes to the database information for an
already authenticated user will not be reflected until
the next time that user logs on again.
Administering the information in the directory server
is the responsibility of your own applications. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
Introduction
MemoryRealm is a simple demonstration implementation of the
Tomcat 4 Realm interface. It is not designed for production use.
At startup time, MemoryRealm loads information about all users, and their
corresponding roles, from an XML document (by default, this document is loaded from $CATALINA_HOME/conf/tomcat-users.xml). Changes to the data
in this file are not recognized until Tomcat is restarted.
Realm Element Attributes
To configure MemoryRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.MemoryRealm" here.
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
Absolute or relative (to $CATALINA_HOME) pathname of the XML document
containing our valid usernames, passwords, and roles. See below for more
information on the format of this file. If not specified, the value
conf/tomcat-users.xml is used.
User File Format
The users file (by default, conf/tomcat-users.xml must be an
XML document, with a root element <tomcat-users>. Nested
inside the root element will be a <user> element for each
valid user, consisting of the following attributes:
name - Username this user must log on with.
password - Password this user must log on with (in
clear text if the digest attribute was not set on the
<Realm> element, or digested appropriately as
described here otherwise).
roles - Comma-delimited list of the role names
associated with this user.
Example
The default installation of Tomcat 4 is configured with a MemoryRealm
nested inside the <Engine> element, so that it applies
to all virtual hosts and web applications. The default contents of the
conf/tomcat-users.xml file is:
<tomcat-users>
<user name="tomcat" password="tomcat" roles="tomcat" />
<user name="role1" password="tomcat" roles="role1" />
<user name="both" password="tomcat" roles="tomcat,role1" />
</tomcat-users>
Additional Notes
MemoryRealm operates according to the following rules:
When Tomcat first starts up, it loads all defined users and their
associated information from the users file. Changes to the data in
this file will not be recognized until Tomcat is
restarted.
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser).
Administering the information in the users file is the responsibility
of your application. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
For each of the standard Realm implementations, the user's
password (by default) is stored in clear text. In many environments, this is
undesireable because casual observers of the authentication data can collect
enough information to log on successfully, and impersonate other users.
To avoid this problem, the standard implementations support the concept of
digesting user passwords. This causes the stored version of the
passwords to be encoded (in a form that is not easily reversible), but that
the Realm implementation can still utilize for authentication.
Digested passwords are selected by specifying the digest
attribute on your <Realm> element. The value for this
attribute must be one of the digest algorithms supported by the
java.security.MessageDigest class (SHA, MD2, or MD5). When you
select this option, the contents of the password that is stored in the
Realm must be the cleartext version of the password, as digested
by the specified algorithm.
When the authenticate() method of the Realm is called, the
(cleartext) password specified by the user is itself digested by the same
algorithm, and the result is compared with the value returned by the
Realm. An equal match implies that the cleartext version of the
original password is the same as the one presented by the user, so that this
user should be authorized.
To calculate the digested value of a cleartext password, two convenience
techniques are supported:
If you are writing an application that needs to calculate digested
passowrds dynamically, call the static Digest() method of the
org.apache.catalina.realm.RealmBase class, passing the
cleartext password and the digest algorithm name as arguments. This
method will return the digested password.
If you want to execute a command line utility to calculate the digested
password, simply execute
java org.apache.catalina.realm.RealmBase \
-a {algorithm} {cleartext-password}
and the digested version of this cleartext password will be returned to
standard output.
To use either of the above techniques, the
$CATALINA_HOME/server/lib/catalina.jar file will need to be
on your class path to make the RealmBase class available.
The example application shipped with Tomcat 4 includes an area that is
protected by a security constraint, utilizing form-based login. To access it,
point your browser at
http://localhost:8080/examples/jsp/security/protected/
and log on with one of the usernames and passwords described for the default
MemoryRealm.
If you wish to use the Manager Application
to deploy and undeploy applications in a running Tomcat 4 installation, you
MUST add the "manager" role to at least one username in your selected Realm
implementation. This is because the manager web application itself uses a
security constraint that requires role "manager" to access ANY request URI
within that application.
For security reasons, no username in the default Realm (i.e. using
conf/tomcat-users.xml is assigned the "manager" role. Therfore,
no one will be able to utilize the features of this application until the
Tomcat administrator specifically assigns this role to one or more users.
/images/void.gif) | , Section 12. For a more introductory level
document for web application developers as well as administrators, see
(FIXME - link to backgrounder on container managed security
to be provided).
For information about utilizing the Single Sign On feature of
Tomcat 4 (allowing a user to authenticate themselves once across the entire
set of web applications associated with a virtual host), see
here.
A Realm is a "database" of usernames and passwords that
identify valid users of a web application (or set of web applications), plus
an enumeration of the list of roles associated with each valid user.
You can think of roles as similar to groups in Unix-like operating
systems, because access to specific web application resources is granted to
all users possessing a particular role (rather than enumerating the list of
associated usernames). A particular user can have any number of roles
associated with their username.
Although the Servlet Specification describes a portable mechanism for
applications to declare their security requirements (in the
web.xml deployment descriptor), there is no portable API
defining the interface between a servlet container and the associated user
and role information. In many cases, however, it is desireable to "connect"
a servlet container to some existing authentication database or mechanism
that already exists in the production environment. Therefore, Tomcat 4
defines a Java interface (org.apache.catalina.Realm) that
can be implemented by "plug in" components to establish this connection.
Three standard plug-ins are provided, supporting connection to three different
sources of authentication information:
JDBCRealm - Accesses authentication information
stored in a relational database, accessed via a JDBC driver.
JNDIRealm - Accesses authentication information
stored in an LDAP based directory server, accessed via a JNDI provider.
MemoryRealm - Accesses authentication
information stored in an in-memory object collection, which is initialized
from an XML document (conf/tomcat-users.xml).
It is also possible to write your own Realm implementation,
and integrate it with Tomcat 4. However, doing this is beyond the scope of
this document. See (FIXME - reference to developer stuff)
for more information.
Before getting into the details of the standard Realm implementations, it is
important to understand, in general terms, how a Realm is configured. In
general, you will be adding an XML element to your conf/server.xml
configuration file, that looks something like this:
<Realm className="... class name for this implementation"
... other attributes for this implementation .../>
The <Realm> element can be nested inside one of three
different elements, which has a direct impact on the "scope" of that Realm
(i.e. which web applications will share the same authentication information):
Inside an <Engine> element - This Realm will be shared
across ALL web applications on ALL virtual hosts, UNLESS it is overridden
by a Realm element nested inside a subordinate <Host>
or <Context> element.
Inside a <Host> element - This Realm will be shared across
ALL web applications for THIS virtual host, UNLESS it is overridden
by a Realm element nested inside a subordinate <Context>
element.
Inside a <Context> element - This Realm will be used ONLY
for THIS web application.
Introduction
JDBCRealm is an implementation of the Tomcat 4
Realm interface that looks up users in a relational database
accessed via a JDBC driver. There is substantial configuration flexibility
that lets you adapt to existing table and column names, as long as your
database structure conforms to the following requirements:
There must be a table, referenced below as the users table,
that contains one row for every valid user that this Realm
should recognize.
The users table must contain at least two columns (it may
contain more if your existing applications required it):
Username to be recognized by Tomcat when the user logs in.
Password to be recognized by Tomcat when the user logs in.
This value may in cleartext or digested - see below for more
information.
There must be a table, referenced below as the user roles table,
that contains one row for every valid role that is assigned to a
particular user. It is legal for a user to have zero, one, or more than
one valid role.
The user roles table must contain at least two columns (it may
contain more if your existing applications required it):
Username to be recognized by Tomcat (same value as is specified
in the users table).
Role name of a valid role associated with this user.
Quick Start
To set up Tomcat to use JDBCRealm, you will need to follow these steps:
If you have not yet done so, create tables and columns in your database
that conform to the requirements described above.
Configure a database username and password for use by Tomcat, that has
at least read only access to the tables described above. (Tomcat will
never attempt to write to these tables.)
Place a copy of the JDBC driver you will be using inside the
$CATALINA_HOME/server/lib directory (if you do not need it
visible to web applications) or $CATALINA_HOME/common/lib
(if it will be used both by Tomcat 4 and by your apps).
Note that only JAR files are recognized!
Set up a <Realm> element, as described below, in your
$CATALINA_HOME/conf/server.xml file.
Restart Tomcat 4 if it is already running.
Realm Element Attributes
To configure JDBCRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.JDBCRealm" here.
The database username used to establish a JDBC connection.
The database password used to establish a JDBC connection.
The database URL used to establish a JDBC connection.
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
The fully qualified Java class name of the JDBC driver to be used.
Consult the documentation for your JDBC driver for the appropriate
value.
The name of the column, in the user roles table, that
contains the name of a role assigned to this user.
The name of the column, in the users table, that contains
the password for this user (either in clear text, or digested if the
digest attribute is set).
The name of the column, in the users and user roles
tables, that contains the username of this user.
The name of the table that contains one row for each role
assigned to a particular username. This table must include at
least the columns named by the userNameCol and
roleNameCol attributes.
The name of the table that contains one row for each username
to be recognized by Tomcat. This table must include at least the columns
named by the userNameCol and userCredCol
attributes.
Example
An example SQL script to create the needed tables might look something
like this (adapt the syntax as required for your particular database):
create table users (
user_name varchar(15) not null primary key,
user_pass varchar(15) not null
);
create table user_roles (
user_name varchar(15) not null,
role_name varchar(15) not null,
primary key (user_name, role_name)
);
Example Realm elements are included (commented out) in the
default $CATALINA_HOME/conf/server.xml file. Here's an example
for using a MySQL database called "authority", configured with the tables
described above, and accessed with username "dbuser" and password "dbpass":
<Realm className="org.apache.catalina.realm.JDBCRealm" debug="99"
driverName="org.gjt.mm.mysql.Driver"
connectionURL="jdbc:mysql://localhost/authority?user=dbuser;password=dbpass"
userTable="users" userNameCol="user_name" userCredCol="user_pass"
userRoleTable="user_roles" roleNameCol="role_name"/>
Additional Notes
JDBCRealm operates according to the following rules:
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm. Thus, any changes you have made to the database
directly (new users, changed passwords or roles, etc.) will be immediately
reflected.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser). Any changes to the database information for an
already authenticated user will not be reflected until
the next time that user logs on again.
Administering the information in the users and user roles
table is the responsibility of your own applications. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
Introduction
JNDIRealm is an implementation of the Tomcat 4
Realm interface that looks up users in a directory server
accessed by a JNDI provider (typically, the standard LDAP provider that
is available with the JNDI API classes). There is substantial configuration
flexibility that lets you adapt to the existing schema inside your directory
server, as long as it conforms to the following requirements:
Each user that can be authenticated is represented by an individual
element in the top level DirContext that is accessed
via the connectionURL attribute.
The user element must have the following characteristics:
The distinguished name (dn) attribute of this element
contains the username that is presented for authentication.
There must be an attribute (identified by the userPassword
attribute of our Realm element) that contains the user's
password, either in clear text or digested (see below for more info).
Each group of users that has been assigned a particular role is
represented by an individual element in the top level
DirContext that is accessed via the
connectionURL attribute.
The user group element must have the following characteristics:
The set of all possible groups of interest can be selected by an LDAP
search pattern configured by the roleSearch attribute
of our Realm element.
The roleSearch pattern optionally includes pattern
replacements "{0}" for the distinguished name, and/or "{1} for the
username, of the authenticated user for which roles will be
retrieved.
The roleBase attribute can be set to the element that
is the base of the search for matching roles. If not specified,
the entire directory context will be searched.
The roleSubtree attribute can be set to true
if you wish to search the entire subtree of the directory context.
The default value of false requests a search of only the
current level.
The element includes an attribute (whose name is configured by the
roleName attribute of our Realm element)
containing the name of the role represented by this element.
There must be an administrator username and password that Tomcat can
use to establish a connection to the directory server, with at least
read-only access to the information described above. A future
version of Tomcat will support an option to use the user's username and
password to attempt this connection.
Quick Start
To set up Tomcat to use JNDIRealm, you will need to follow these steps:
Make sure your directory server is configured with a schema that matches
the requirements listed above.
Configure a username and password for use by Tomcat, that has
at least read only access to the information described above. (Tomcat will
never attempt to modify this information.)
Place a copy of the JNDI driver you will be using (typically
ldap.jar available with JNDI) inside the
$CATALINA_HOME/server/lib directory (if you do not need it
visible to web applications) or $CATALINA_HOME/common/lib
(if it will be used both by Tomcat 4 and by your apps).
Set up a <Realm> element, as described below, in your
$CATALINA_HOME/conf/server.xml file.
Restart Tomcat 4 if it is already running.
Realm Element Attributes
To configure JNDIRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.JDBCRealm" here.
The directory server username used to establish a JNDI connection.
The directory server password used to establish a JNDI connection.
The directory server URL used to establish a JNDI connection.
The fully qualified Java class name of the JNDI context factory to be
used for this connection. By default, the standard JNDI LDAP provider
is used (com.sun.jndi.ldap.LdapCtxFactory).
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
The base element for role searches. If not specified, the top level
element in the directory context will be used.
The name of the directory server attribute containing the role name.
An LDAP search pattern for selecting roles in this Realm, following the
syntax supported by the java.text.MessageFormat class. Use
{0} to substitute in the distinguished name of the user you
want roles for, and/or {1} to substitute in the username of
the user you want roles for.
Set to true if you want role searches to search subtrees
of the element selected by roleBase. The default value of
false causes only the top level element to be searched.
The name of the directory server attribute (in the user element) that
contains the cleartext or digested user password (depending on the setting
of the digest attribute).
An LDAP search pattern for selecting users in this Realm, following the
syntax supported by the java.text.MessageFormat class. Use
{0} to substitute in the distinguished name of the user you
want to select.
Example
Creation of the appropriate schema in your directory server is beyond the
scope of this document, because it is unique to each directory server
implementation. In the examples below, we will assume that you are using a
distribution of the OpenLDAP directory server (version 2.0.11 or later), which
can be downloaded from
http://www.openldap.org. Assume that
your slapd.conf file contains the following settings
(among others):
database ldbm
suffix dc="mycompany",dc="com"
rootdn "cn=Manager,dc=mycompany,dc=com"
rootpw secret
These settings help us identify values for the values to be specified for
connectionName, and connectionPassword, and we
will assume for connectionURL that the directory server runs on
the same machine as Tomcat. See
http://java.sun.com/products/jndi/docs.html
for more information about configuring and using the JNDI LDAP provider.
Next, assume that this directory server has been populated with elements
as shown below (in LDIF format), which define the same users and roles
as the default $CATALINA_HOME/conf/tomcat-users.xml does for
MemoryRealm:
# Define a user named 'tomcat'
dn: cn=tomcat,dc=mycompany,dc=com
cn: tomcat
userPassword: tomcat
sn: Tomcat User
objectClass: person
# Define a user named 'role1'
dn: cn=role1,dc=mycompany,dc=com
cn: role1
userPassword: tomcat
sn: Role1 User
objectClass: person
# Define a user named 'both'
dn: cn=both,dc=mycompany,dc=com
cn: both
userPassword: tomcat
sn: Both User
objectClass: person
# Define an entry to base role searches on
dn: dc=roles,dc=mycompany,dc=com
cn: roles
objectClass: person
sn: Roles Entry
# Define all members of the 'tomcat' role
dn: cn=tomcat,dc=roles,dc=mycompany,dc=com
cn: tomcat
objectClass: groupOfUniqueNames
uniqueMember: cn=tomcat,dc=mycompany,dc=com
uniqueMember: cn=both,dc=mycompany,dc=com
# Define all members of the 'role1' role
dn: cn=role1,dc=roles,dc=mycompany,dc=com
cn: role1
objectClass: groupOfUniqueNames
uniqueMember: cn=role1,dc=mycompany,dc=com
uniqueMember: cn=both,dc=mycompany,dc=com
An example Realm element for the OpenLDAP directory server
configured as described above might look like this:
<Realm className="org.apache.catalina.realm.JNDIRealm" debug="99"
connectionName="cn=Manager,dc=mycompany,dc=com"
connectionPassword="secret"
connectionURL="ldap://localhost:389"
roleBase="dc=roles,dc=mcclan,dc=net"
roleName="cn"
roleSearch="(uniqueMember={0})"
roleSubtree="false"
userPassword="userPassword"
userPattern="cn={0},dc=mycompany,dc=com"
/>
Additional Notes
JNDIRealm operates according to the following rules:
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm. Thus, any changes you have made to the database
directly (new users, changed passwords or roles, etc.) will be immediately
reflected.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser). Any changes to the database information for an
already authenticated user will not be reflected until
the next time that user logs on again.
Administering the information in the directory server
is the responsibility of your own applications. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
Introduction
MemoryRealm is a simple demonstration implementation of the
Tomcat 4 Realm interface. It is not designed for production use.
At startup time, MemoryRealm loads information about all users, and their
corresponding roles, from an XML document (by default, this document is loaded from $CATALINA_HOME/conf/tomcat-users.xml). Changes to the data
in this file are not recognized until Tomcat is restarted.
Realm Element Attributes
To configure MemoryRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.MemoryRealm" here.
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
Absolute or relative (to $CATALINA_HOME) pathname of the XML document
containing our valid usernames, passwords, and roles. See below for more
information on the format of this file. If not specified, the value
conf/tomcat-users.xml is used.
User File Format
The users file (by default, conf/tomcat-users.xml must be an
XML document, with a root element <tomcat-users>. Nested
inside the root element will be a <user> element for each
valid user, consisting of the following attributes:
name - Username this user must log on with.
password - Password this user must log on with (in
clear text if the digest attribute was not set on the
<Realm> element, or digested appropriately as
described here otherwise).
roles - Comma-delimited list of the role names
associated with this user.
Example
The default installation of Tomcat 4 is configured with a MemoryRealm
nested inside the <Engine> element, so that it applies
to all virtual hosts and web applications. The default contents of the
conf/tomcat-users.xml file is:
<tomcat-users>
<user name="tomcat" password="tomcat" roles="tomcat" />
<user name="role1" password="tomcat" roles="role1" />
<user name="both" password="tomcat" roles="tomcat,role1" />
</tomcat-users>
Additional Notes
MemoryRealm operates according to the following rules:
When Tomcat first starts up, it loads all defined users and their
associated information from the users file. Changes to the data in
this file will not be recognized until Tomcat is
restarted.
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser).
Administering the information in the users file is the responsibility
of your application. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
For each of the standard Realm implementations, the user's
password (by default) is stored in clear text. In many environments, this is
undesireable because casual observers of the authentication data can collect
enough information to log on successfully, and impersonate other users.
To avoid this problem, the standard implementations support the concept of
digesting user passwords. This causes the stored version of the
passwords to be encoded (in a form that is not easily reversible), but that
the Realm implementation can still utilize for authentication.
Digested passwords are selected by specifying the digest
attribute on your <Realm> element. The value for this
attribute must be one of the digest algorithms supported by the
java.security.MessageDigest class (SHA, MD2, or MD5). When you
select this option, the contents of the password that is stored in the
Realm must be the cleartext version of the password, as digested
by the specified algorithm.
When the authenticate() method of the Realm is called, the
(cleartext) password specified by the user is itself digested by the same
algorithm, and the result is compared with the value returned by the
Realm. An equal match implies that the cleartext version of the
original password is the same as the one presented by the user, so that this
user should be authorized.
To calculate the digested value of a cleartext password, two convenience
techniques are supported:
If you are writing an application that needs to calculate digested
passowrds dynamically, call the static Digest() method of the
org.apache.catalina.realm.RealmBase class, passing the
cleartext password and the digest algorithm name as arguments. This
method will return the digested password.
If you want to execute a command line utility to calculate the digested
password, simply execute
java org.apache.catalina.realm.RealmBase \
-a {algorithm} {cleartext-password}
and the digested version of this cleartext password will be returned to
standard output.
To use either of the above techniques, the
$CATALINA_HOME/server/lib/catalina.jar file will need to be
on your class path to make the RealmBase class available.
The example application shipped with Tomcat 4 includes an area that is
protected by a security constraint, utilizing form-based login. To access it,
point your browser at
http://localhost:8080/examples/jsp/security/protected/
and log on with one of the usernames and passwords described for the default
MemoryRealm.
If you wish to use the Manager Application
to deploy and undeploy applications in a running Tomcat 4 installation, you
MUST add the "manager" role to at least one username in your selected Realm
implementation. This is because the manager web application itself uses a
security constraint that requires role "manager" to access ANY request URI
within that application.
For security reasons, no username in the default Realm (i.e. using
conf/tomcat-users.xml is assigned the "manager" role. Therfore,
no one will be able to utilize the features of this application until the
Tomcat administrator specifically assigns this role to one or more users.
/images/void.gif) | , Section 12. For a more introductory level
document for web application developers as well as administrators, see
(FIXME - link to backgrounder on container managed security
to be provided).
For information about utilizing the Single Sign On feature of
Tomcat 4 (allowing a user to authenticate themselves once across the entire
set of web applications associated with a virtual host), see
here.
A Realm is a "database" of usernames and passwords that
identify valid users of a web application (or set of web applications), plus
an enumeration of the list of roles associated with each valid user.
You can think of roles as similar to groups in Unix-like operating
systems, because access to specific web application resources is granted to
all users possessing a particular role (rather than enumerating the list of
associated usernames). A particular user can have any number of roles
associated with their username.
Although the Servlet Specification describes a portable mechanism for
applications to declare their security requirements (in the
web.xml deployment descriptor), there is no portable API
defining the interface between a servlet container and the associated user
and role information. In many cases, however, it is desireable to "connect"
a servlet container to some existing authentication database or mechanism
that already exists in the production environment. Therefore, Tomcat 4
defines a Java interface (org.apache.catalina.Realm) that
can be implemented by "plug in" components to establish this connection.
Three standard plug-ins are provided, supporting connection to three different
sources of authentication information:
JDBCRealm - Accesses authentication information
stored in a relational database, accessed via a JDBC driver.
JNDIRealm - Accesses authentication information
stored in an LDAP based directory server, accessed via a JNDI provider.
MemoryRealm - Accesses authentication
information stored in an in-memory object collection, which is initialized
from an XML document (conf/tomcat-users.xml).
It is also possible to write your own Realm implementation,
and integrate it with Tomcat 4. However, doing this is beyond the scope of
this document. See (FIXME - reference to developer stuff)
for more information.
Before getting into the details of the standard Realm implementations, it is
important to understand, in general terms, how a Realm is configured. In
general, you will be adding an XML element to your conf/server.xml
configuration file, that looks something like this:
<Realm className="... class name for this implementation"
... other attributes for this implementation .../>
The <Realm> element can be nested inside one of three
different elements, which has a direct impact on the "scope" of that Realm
(i.e. which web applications will share the same authentication information):
Inside an <Engine> element - This Realm will be shared
across ALL web applications on ALL virtual hosts, UNLESS it is overridden
by a Realm element nested inside a subordinate <Host>
or <Context> element.
Inside a <Host> element - This Realm will be shared across
ALL web applications for THIS virtual host, UNLESS it is overridden
by a Realm element nested inside a subordinate <Context>
element.
Inside a <Context> element - This Realm will be used ONLY
for THIS web application.
Introduction
JDBCRealm is an implementation of the Tomcat 4
Realm interface that looks up users in a relational database
accessed via a JDBC driver. There is substantial configuration flexibility
that lets you adapt to existing table and column names, as long as your
database structure conforms to the following requirements:
There must be a table, referenced below as the users table,
that contains one row for every valid user that this Realm
should recognize.
The users table must contain at least two columns (it may
contain more if your existing applications required it):
Username to be recognized by Tomcat when the user logs in.
Password to be recognized by Tomcat when the user logs in.
This value may in cleartext or digested - see below for more
information.
There must be a table, referenced below as the user roles table,
that contains one row for every valid role that is assigned to a
particular user. It is legal for a user to have zero, one, or more than
one valid role.
The user roles table must contain at least two columns (it may
contain more if your existing applications required it):
Username to be recognized by Tomcat (same value as is specified
in the users table).
Role name of a valid role associated with this user.
Quick Start
To set up Tomcat to use JDBCRealm, you will need to follow these steps:
If you have not yet done so, create tables and columns in your database
that conform to the requirements described above.
Configure a database username and password for use by Tomcat, that has
at least read only access to the tables described above. (Tomcat will
never attempt to write to these tables.)
Place a copy of the JDBC driver you will be using inside the
$CATALINA_HOME/server/lib directory (if you do not need it
visible to web applications) or $CATALINA_HOME/common/lib
(if it will be used both by Tomcat 4 and by your apps).
Note that only JAR files are recognized!
Set up a <Realm> element, as described below, in your
$CATALINA_HOME/conf/server.xml file.
Restart Tomcat 4 if it is already running.
Realm Element Attributes
To configure JDBCRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.JDBCRealm" here.
The database username used to establish a JDBC connection.
The database password used to establish a JDBC connection.
The database URL used to establish a JDBC connection.
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
The fully qualified Java class name of the JDBC driver to be used.
Consult the documentation for your JDBC driver for the appropriate
value.
The name of the column, in the user roles table, that
contains the name of a role assigned to this user.
The name of the column, in the users table, that contains
the password for this user (either in clear text, or digested if the
digest attribute is set).
The name of the column, in the users and user roles
tables, that contains the username of this user.
The name of the table that contains one row for each role
assigned to a particular username. This table must include at
least the columns named by the userNameCol and
roleNameCol attributes.
The name of the table that contains one row for each username
to be recognized by Tomcat. This table must include at least the columns
named by the userNameCol and userCredCol
attributes.
Example
An example SQL script to create the needed tables might look something
like this (adapt the syntax as required for your particular database):
create table users (
user_name varchar(15) not null primary key,
user_pass varchar(15) not null
);
create table user_roles (
user_name varchar(15) not null,
role_name varchar(15) not null,
primary key (user_name, role_name)
);
Example Realm elements are included (commented out) in the
default $CATALINA_HOME/conf/server.xml file. Here's an example
for using a MySQL database called "authority", configured with the tables
described above, and accessed with username "dbuser" and password "dbpass":
<Realm className="org.apache.catalina.realm.JDBCRealm" debug="99"
driverName="org.gjt.mm.mysql.Driver"
connectionURL="jdbc:mysql://localhost/authority?user=dbuser;password=dbpass"
userTable="users" userNameCol="user_name" userCredCol="user_pass"
userRoleTable="user_roles" roleNameCol="role_name"/>
Additional Notes
JDBCRealm operates according to the following rules:
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm. Thus, any changes you have made to the database
directly (new users, changed passwords or roles, etc.) will be immediately
reflected.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser). Any changes to the database information for an
already authenticated user will not be reflected until
the next time that user logs on again.
Administering the information in the users and user roles
table is the responsibility of your own applications. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
Introduction
JNDIRealm is an implementation of the Tomcat 4
Realm interface that looks up users in a directory server
accessed by a JNDI provider (typically, the standard LDAP provider that
is available with the JNDI API classes). There is substantial configuration
flexibility that lets you adapt to the existing schema inside your directory
server, as long as it conforms to the following requirements:
Each user that can be authenticated is represented by an individual
element in the top level DirContext that is accessed
via the connectionURL attribute.
The user element must have the following characteristics:
The distinguished name (dn) attribute of this element
contains the username that is presented for authentication.
There must be an attribute (identified by the userPassword
attribute of our Realm element) that contains the user's
password, either in clear text or digested (see below for more info).
Each group of users that has been assigned a particular role is
represented by an individual element in the top level
DirContext that is accessed via the
connectionURL attribute.
The user group element must have the following characteristics:
The set of all possible groups of interest can be selected by an LDAP
search pattern configured by the roleSearch attribute
of our Realm element.
The roleSearch pattern optionally includes pattern
replacements "{0}" for the distinguished name, and/or "{1} for the
username, of the authenticated user for which roles will be
retrieved.
The roleBase attribute can be set to the element that
is the base of the search for matching roles. If not specified,
the entire directory context will be searched.
The roleSubtree attribute can be set to true
if you wish to search the entire subtree of the directory context.
The default value of false requests a search of only the
current level.
The element includes an attribute (whose name is configured by the
roleName attribute of our Realm element)
containing the name of the role represented by this element.
There must be an administrator username and password that Tomcat can
use to establish a connection to the directory server, with at least
read-only access to the information described above. A future
version of Tomcat will support an option to use the user's username and
password to attempt this connection.
Quick Start
To set up Tomcat to use JNDIRealm, you will need to follow these steps:
Make sure your directory server is configured with a schema that matches
the requirements listed above.
Configure a username and password for use by Tomcat, that has
at least read only access to the information described above. (Tomcat will
never attempt to modify this information.)
Place a copy of the JNDI driver you will be using (typically
ldap.jar available with JNDI) inside the
$CATALINA_HOME/server/lib directory (if you do not need it
visible to web applications) or $CATALINA_HOME/common/lib
(if it will be used both by Tomcat 4 and by your apps).
Set up a <Realm> element, as described below, in your
$CATALINA_HOME/conf/server.xml file.
Restart Tomcat 4 if it is already running.
Realm Element Attributes
To configure JNDIRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.JDBCRealm" here.
The directory server username used to establish a JNDI connection.
The directory server password used to establish a JNDI connection.
The directory server URL used to establish a JNDI connection.
The fully qualified Java class name of the JNDI context factory to be
used for this connection. By default, the standard JNDI LDAP provider
is used (com.sun.jndi.ldap.LdapCtxFactory).
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
The base element for role searches. If not specified, the top level
element in the directory context will be used.
The name of the directory server attribute containing the role name.
An LDAP search pattern for selecting roles in this Realm, following the
syntax supported by the java.text.MessageFormat class. Use
{0} to substitute in the distinguished name of the user you
want roles for, and/or {1} to substitute in the username of
the user you want roles for.
Set to true if you want role searches to search subtrees
of the element selected by roleBase. The default value of
false causes only the top level element to be searched.
The name of the directory server attribute (in the user element) that
contains the cleartext or digested user password (depending on the setting
of the digest attribute).
An LDAP search pattern for selecting users in this Realm, following the
syntax supported by the java.text.MessageFormat class. Use
{0} to substitute in the distinguished name of the user you
want to select.
Example
Creation of the appropriate schema in your directory server is beyond the
scope of this document, because it is unique to each directory server
implementation. In the examples below, we will assume that you are using a
distribution of the OpenLDAP directory server (version 2.0.11 or later), which
can be downloaded from
http://www.openldap.org. Assume that
your slapd.conf file contains the following settings
(among others):
database ldbm
suffix dc="mycompany",dc="com"
rootdn "cn=Manager,dc=mycompany,dc=com"
rootpw secret
These settings help us identify values for the values to be specified for
connectionName, and connectionPassword, and we
will assume for connectionURL that the directory server runs on
the same machine as Tomcat. See
http://java.sun.com/products/jndi/docs.html
for more information about configuring and using the JNDI LDAP provider.
Next, assume that this directory server has been populated with elements
as shown below (in LDIF format), which define the same users and roles
as the default $CATALINA_HOME/conf/tomcat-users.xml does for
MemoryRealm:
# Define a user named 'tomcat'
dn: cn=tomcat,dc=mycompany,dc=com
cn: tomcat
userPassword: tomcat
sn: Tomcat User
objectClass: person
# Define a user named 'role1'
dn: cn=role1,dc=mycompany,dc=com
cn: role1
userPassword: tomcat
sn: Role1 User
objectClass: person
# Define a user named 'both'
dn: cn=both,dc=mycompany,dc=com
cn: both
userPassword: tomcat
sn: Both User
objectClass: person
# Define an entry to base role searches on
dn: dc=roles,dc=mycompany,dc=com
cn: roles
objectClass: person
sn: Roles Entry
# Define all members of the 'tomcat' role
dn: cn=tomcat,dc=roles,dc=mycompany,dc=com
cn: tomcat
objectClass: groupOfUniqueNames
uniqueMember: cn=tomcat,dc=mycompany,dc=com
uniqueMember: cn=both,dc=mycompany,dc=com
# Define all members of the 'role1' role
dn: cn=role1,dc=roles,dc=mycompany,dc=com
cn: role1
objectClass: groupOfUniqueNames
uniqueMember: cn=role1,dc=mycompany,dc=com
uniqueMember: cn=both,dc=mycompany,dc=com
An example Realm element for the OpenLDAP directory server
configured as described above might look like this:
<Realm className="org.apache.catalina.realm.JNDIRealm" debug="99"
connectionName="cn=Manager,dc=mycompany,dc=com"
connectionPassword="secret"
connectionURL="ldap://localhost:389"
roleBase="dc=roles,dc=mcclan,dc=net"
roleName="cn"
roleSearch="(uniqueMember={0})"
roleSubtree="false"
userPassword="userPassword"
userPattern="cn={0},dc=mycompany,dc=com"
/>
Additional Notes
JNDIRealm operates according to the following rules:
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm. Thus, any changes you have made to the database
directly (new users, changed passwords or roles, etc.) will be immediately
reflected.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser). Any changes to the database information for an
already authenticated user will not be reflected until
the next time that user logs on again.
Administering the information in the directory server
is the responsibility of your own applications. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
Introduction
MemoryRealm is a simple demonstration implementation of the
Tomcat 4 Realm interface. It is not designed for production use.
At startup time, MemoryRealm loads information about all users, and their
corresponding roles, from an XML document (by default, this document is loaded from $CATALINA_HOME/conf/tomcat-users.xml). Changes to the data
in this file are not recognized until Tomcat is restarted.
Realm Element Attributes
To configure MemoryRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.MemoryRealm" here.
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
Absolute or relative (to $CATALINA_HOME) pathname of the XML document
containing our valid usernames, passwords, and roles. See below for more
information on the format of this file. If not specified, the value
conf/tomcat-users.xml is used.
User File Format
The users file (by default, conf/tomcat-users.xml must be an
XML document, with a root element <tomcat-users>. Nested
inside the root element will be a <user> element for each
valid user, consisting of the following attributes:
name - Username this user must log on with.
password - Password this user must log on with (in
clear text if the digest attribute was not set on the
<Realm> element, or digested appropriately as
described here otherwise).
roles - Comma-delimited list of the role names
associated with this user.
Example
The default installation of Tomcat 4 is configured with a MemoryRealm
nested inside the <Engine> element, so that it applies
to all virtual hosts and web applications. The default contents of the
conf/tomcat-users.xml file is:
<tomcat-users>
<user name="tomcat" password="tomcat" roles="tomcat" />
<user name="role1" password="tomcat" roles="role1" />
<user name="both" password="tomcat" roles="tomcat,role1" />
</tomcat-users>
Additional Notes
MemoryRealm operates according to the following rules:
When Tomcat first starts up, it loads all defined users and their
associated information from the users file. Changes to the data in
this file will not be recognized until Tomcat is
restarted.
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser).
Administering the information in the users file is the responsibility
of your application. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
For each of the standard Realm implementations, the user's
password (by default) is stored in clear text. In many environments, this is
undesireable because casual observers of the authentication data can collect
enough information to log on successfully, and impersonate other users.
To avoid this problem, the standard implementations support the concept of
digesting user passwords. This causes the stored version of the
passwords to be encoded (in a form that is not easily reversible), but that
the Realm implementation can still utilize for authentication.
Digested passwords are selected by specifying the digest
attribute on your <Realm> element. The value for this
attribute must be one of the digest algorithms supported by the
java.security.MessageDigest class (SHA, MD2, or MD5). When you
select this option, the contents of the password that is stored in the
Realm must be the cleartext version of the password, as digested
by the specified algorithm.
When the authenticate() method of the Realm is called, the
(cleartext) password specified by the user is itself digested by the same
algorithm, and the result is compared with the value returned by the
Realm. An equal match implies that the cleartext version of the
original password is the same as the one presented by the user, so that this
user should be authorized.
To calculate the digested value of a cleartext password, two convenience
techniques are supported:
If you are writing an application that needs to calculate digested
passowrds dynamically, call the static Digest() method of the
org.apache.catalina.realm.RealmBase class, passing the
cleartext password and the digest algorithm name as arguments. This
method will return the digested password.
If you want to execute a command line utility to calculate the digested
password, simply execute
java org.apache.catalina.realm.RealmBase \
-a {algorithm} {cleartext-password}
and the digested version of this cleartext password will be returned to
standard output.
To use either of the above techniques, the
$CATALINA_HOME/server/lib/catalina.jar file will need to be
on your class path to make the RealmBase class available.
The example application shipped with Tomcat 4 includes an area that is
protected by a security constraint, utilizing form-based login. To access it,
point your browser at
http://localhost:8080/examples/jsp/security/protected/
and log on with one of the usernames and passwords described for the default
MemoryRealm.
If you wish to use the Manager Application
to deploy and undeploy applications in a running Tomcat 4 installation, you
MUST add the "manager" role to at least one username in your selected Realm
implementation. This is because the manager web application itself uses a
security constraint that requires role "manager" to access ANY request URI
within that application.
For security reasons, no username in the default Realm (i.e. using
conf/tomcat-users.xml is assigned the "manager" role. Therfore,
no one will be able to utilize the features of this application until the
Tomcat administrator specifically assigns this role to one or more users.
/images/void.gif) | , Section 12. For a more introductory level
document for web application developers as well as administrators, see
(FIXME - link to backgrounder on container managed security
to be provided).
For information about utilizing the Single Sign On feature of
Tomcat 4 (allowing a user to authenticate themselves once across the entire
set of web applications associated with a virtual host), see
here.
A Realm is a "database" of usernames and passwords that
identify valid users of a web application (or set of web applications), plus
an enumeration of the list of roles associated with each valid user.
You can think of roles as similar to groups in Unix-like operating
systems, because access to specific web application resources is granted to
all users possessing a particular role (rather than enumerating the list of
associated usernames). A particular user can have any number of roles
associated with their username.
Although the Servlet Specification describes a portable mechanism for
applications to declare their security requirements (in the
web.xml deployment descriptor), there is no portable API
defining the interface between a servlet container and the associated user
and role information. In many cases, however, it is desireable to "connect"
a servlet container to some existing authentication database or mechanism
that already exists in the production environment. Therefore, Tomcat 4
defines a Java interface (org.apache.catalina.Realm) that
can be implemented by "plug in" components to establish this connection.
Three standard plug-ins are provided, supporting connection to three different
sources of authentication information:
JDBCRealm - Accesses authentication information
stored in a relational database, accessed via a JDBC driver.
JNDIRealm - Accesses authentication information
stored in an LDAP based directory server, accessed via a JNDI provider.
MemoryRealm - Accesses authentication
information stored in an in-memory object collection, which is initialized
from an XML document (conf/tomcat-users.xml).
It is also possible to write your own Realm implementation,
and integrate it with Tomcat 4. However, doing this is beyond the scope of
this document. See (FIXME - reference to developer stuff)
for more information.
Before getting into the details of the standard Realm implementations, it is
important to understand, in general terms, how a Realm is configured. In
general, you will be adding an XML element to your conf/server.xml
configuration file, that looks something like this:
<Realm className="... class name for this implementation"
... other attributes for this implementation .../>
The <Realm> element can be nested inside one of three
different elements, which has a direct impact on the "scope" of that Realm
(i.e. which web applications will share the same authentication information):
Inside an <Engine> element - This Realm will be shared
across ALL web applications on ALL virtual hosts, UNLESS it is overridden
by a Realm element nested inside a subordinate <Host>
or <Context> element.
Inside a <Host> element - This Realm will be shared across
ALL web applications for THIS virtual host, UNLESS it is overridden
by a Realm element nested inside a subordinate <Context>
element.
Inside a <Context> element - This Realm will be used ONLY
for THIS web application.
Introduction
JDBCRealm is an implementation of the Tomcat 4
Realm interface that looks up users in a relational database
accessed via a JDBC driver. There is substantial configuration flexibility
that lets you adapt to existing table and column names, as long as your
database structure conforms to the following requirements:
There must be a table, referenced below as the users table,
that contains one row for every valid user that this Realm
should recognize.
The users table must contain at least two columns (it may
contain more if your existing applications required it):
Username to be recognized by Tomcat when the user logs in.
Password to be recognized by Tomcat when the user logs in.
This value may in cleartext or digested - see below for more
information.
There must be a table, referenced below as the user roles table,
that contains one row for every valid role that is assigned to a
particular user. It is legal for a user to have zero, one, or more than
one valid role.
The user roles table must contain at least two columns (it may
contain more if your existing applications required it):
Username to be recognized by Tomcat (same value as is specified
in the users table).
Role name of a valid role associated with this user.
Quick Start
To set up Tomcat to use JDBCRealm, you will need to follow these steps:
If you have not yet done so, create tables and columns in your database
that conform to the requirements described above.
Configure a database username and password for use by Tomcat, that has
at least read only access to the tables described above. (Tomcat will
never attempt to write to these tables.)
Place a copy of the JDBC driver you will be using inside the
$CATALINA_HOME/server/lib directory (if you do not need it
visible to web applications) or $CATALINA_HOME/common/lib
(if it will be used both by Tomcat 4 and by your apps).
Note that only JAR files are recognized!
Set up a <Realm> element, as described below, in your
$CATALINA_HOME/conf/server.xml file.
Restart Tomcat 4 if it is already running.
Realm Element Attributes
To configure JDBCRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.JDBCRealm" here.
The database username used to establish a JDBC connection.
The database password used to establish a JDBC connection.
The database URL used to establish a JDBC connection.
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
The fully qualified Java class name of the JDBC driver to be used.
Consult the documentation for your JDBC driver for the appropriate
value.
The name of the column, in the user roles table, that
contains the name of a role assigned to this user.
The name of the column, in the users table, that contains
the password for this user (either in clear text, or digested if the
digest attribute is set).
The name of the column, in the users and user roles
tables, that contains the username of this user.
The name of the table that contains one row for each role
assigned to a particular username. This table must include at
least the columns named by the userNameCol and
roleNameCol attributes.
The name of the table that contains one row for each username
to be recognized by Tomcat. This table must include at least the columns
named by the userNameCol and userCredCol
attributes.
Example
An example SQL script to create the needed tables might look something
like this (adapt the syntax as required for your particular database):
create table users (
user_name varchar(15) not null primary key,
user_pass varchar(15) not null
);
create table user_roles (
user_name varchar(15) not null,
role_name varchar(15) not null,
primary key (user_name, role_name)
);
Example Realm elements are included (commented out) in the
default $CATALINA_HOME/conf/server.xml file. Here's an example
for using a MySQL database called "authority", configured with the tables
described above, and accessed with username "dbuser" and password "dbpass":
<Realm className="org.apache.catalina.realm.JDBCRealm" debug="99"
driverName="org.gjt.mm.mysql.Driver"
connectionURL="jdbc:mysql://localhost/authority?user=dbuser;password=dbpass"
userTable="users" userNameCol="user_name" userCredCol="user_pass"
userRoleTable="user_roles" roleNameCol="role_name"/>
Additional Notes
JDBCRealm operates according to the following rules:
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm. Thus, any changes you have made to the database
directly (new users, changed passwords or roles, etc.) will be immediately
reflected.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser). Any changes to the database information for an
already authenticated user will not be reflected until
the next time that user logs on again.
Administering the information in the users and user roles
table is the responsibility of your own applications. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
Introduction
JNDIRealm is an implementation of the Tomcat 4
Realm interface that looks up users in a directory server
accessed by a JNDI provider (typically, the standard LDAP provider that
is available with the JNDI API classes). There is substantial configuration
flexibility that lets you adapt to the existing schema inside your directory
server, as long as it conforms to the following requirements:
Each user that can be authenticated is represented by an individual
element in the top level DirContext that is accessed
via the connectionURL attribute.
The user element must have the following characteristics:
The distinguished name (dn) attribute of this element
contains the username that is presented for authentication.
There must be an attribute (identified by the userPassword
attribute of our Realm element) that contains the user's
password, either in clear text or digested (see below for more info).
Each group of users that has been assigned a particular role is
represented by an individual element in the top level
DirContext that is accessed via the
connectionURL attribute.
The user group element must have the following characteristics:
The set of all possible groups of interest can be selected by an LDAP
search pattern configured by the roleSearch attribute
of our Realm element.
The roleSearch pattern optionally includes pattern
replacements "{0}" for the distinguished name, and/or "{1} for the
username, of the authenticated user for which roles will be
retrieved.
The roleBase attribute can be set to the element that
is the base of the search for matching roles. If not specified,
the entire directory context will be searched.
The roleSubtree attribute can be set to true
if you wish to search the entire subtree of the directory context.
The default value of false requests a search of only the
current level.
The element includes an attribute (whose name is configured by the
roleName attribute of our Realm element)
containing the name of the role represented by this element.
There must be an administrator username and password that Tomcat can
use to establish a connection to the directory server, with at least
read-only access to the information described above. A future
version of Tomcat will support an option to use the user's username and
password to attempt this connection.
Quick Start
To set up Tomcat to use JNDIRealm, you will need to follow these steps:
Make sure your directory server is configured with a schema that matches
the requirements listed above.
Configure a username and password for use by Tomcat, that has
at least read only access to the information described above. (Tomcat will
never attempt to modify this information.)
Place a copy of the JNDI driver you will be using (typically
ldap.jar available with JNDI) inside the
$CATALINA_HOME/server/lib directory (if you do not need it
visible to web applications) or $CATALINA_HOME/common/lib
(if it will be used both by Tomcat 4 and by your apps).
Set up a <Realm> element, as described below, in your
$CATALINA_HOME/conf/server.xml file.
Restart Tomcat 4 if it is already running.
Realm Element Attributes
To configure JNDIRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.JDBCRealm" here.
The directory server username used to establish a JNDI connection.
The directory server password used to establish a JNDI connection.
The directory server URL used to establish a JNDI connection.
The fully qualified Java class name of the JNDI context factory to be
used for this connection. By default, the standard JNDI LDAP provider
is used (com.sun.jndi.ldap.LdapCtxFactory).
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
The base element for role searches. If not specified, the top level
element in the directory context will be used.
The name of the directory server attribute containing the role name.
An LDAP search pattern for selecting roles in this Realm, following the
syntax supported by the java.text.MessageFormat class. Use
{0} to substitute in the distinguished name of the user you
want roles for, and/or {1} to substitute in the username of
the user you want roles for.
Set to true if you want role searches to search subtrees
of the element selected by roleBase. The default value of
false causes only the top level element to be searched.
The name of the directory server attribute (in the user element) that
contains the cleartext or digested user password (depending on the setting
of the digest attribute).
An LDAP search pattern for selecting users in this Realm, following the
syntax supported by the java.text.MessageFormat class. Use
{0} to substitute in the distinguished name of the user you
want to select.
Example
Creation of the appropriate schema in your directory server is beyond the
scope of this document, because it is unique to each directory server
implementation. In the examples below, we will assume that you are using a
distribution of the OpenLDAP directory server (version 2.0.11 or later), which
can be downloaded from
http://www.openldap.org. Assume that
your slapd.conf file contains the following settings
(among others):
database ldbm
suffix dc="mycompany",dc="com"
rootdn "cn=Manager,dc=mycompany,dc=com"
rootpw secret
These settings help us identify values for the values to be specified for
connectionName, and connectionPassword, and we
will assume for connectionURL that the directory server runs on
the same machine as Tomcat. See
http://java.sun.com/products/jndi/docs.html
for more information about configuring and using the JNDI LDAP provider.
Next, assume that this directory server has been populated with elements
as shown below (in LDIF format), which define the same users and roles
as the default $CATALINA_HOME/conf/tomcat-users.xml does for
MemoryRealm:
# Define a user named 'tomcat'
dn: cn=tomcat,dc=mycompany,dc=com
cn: tomcat
userPassword: tomcat
sn: Tomcat User
objectClass: person
# Define a user named 'role1'
dn: cn=role1,dc=mycompany,dc=com
cn: role1
userPassword: tomcat
sn: Role1 User
objectClass: person
# Define a user named 'both'
dn: cn=both,dc=mycompany,dc=com
cn: both
userPassword: tomcat
sn: Both User
objectClass: person
# Define an entry to base role searches on
dn: dc=roles,dc=mycompany,dc=com
cn: roles
objectClass: person
sn: Roles Entry
# Define all members of the 'tomcat' role
dn: cn=tomcat,dc=roles,dc=mycompany,dc=com
cn: tomcat
objectClass: groupOfUniqueNames
uniqueMember: cn=tomcat,dc=mycompany,dc=com
uniqueMember: cn=both,dc=mycompany,dc=com
# Define all members of the 'role1' role
dn: cn=role1,dc=roles,dc=mycompany,dc=com
cn: role1
objectClass: groupOfUniqueNames
uniqueMember: cn=role1,dc=mycompany,dc=com
uniqueMember: cn=both,dc=mycompany,dc=com
An example Realm element for the OpenLDAP directory server
configured as described above might look like this:
<Realm className="org.apache.catalina.realm.JNDIRealm" debug="99"
connectionName="cn=Manager,dc=mycompany,dc=com"
connectionPassword="secret"
connectionURL="ldap://localhost:389"
roleBase="dc=roles,dc=mcclan,dc=net"
roleName="cn"
roleSearch="(uniqueMember={0})"
roleSubtree="false"
userPassword="userPassword"
userPattern="cn={0},dc=mycompany,dc=com"
/>
Additional Notes
JNDIRealm operates according to the following rules:
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm. Thus, any changes you have made to the database
directly (new users, changed passwords or roles, etc.) will be immediately
reflected.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser). Any changes to the database information for an
already authenticated user will not be reflected until
the next time that user logs on again.
Administering the information in the directory server
is the responsibility of your own applications. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
Introduction
MemoryRealm is a simple demonstration implementation of the
Tomcat 4 Realm interface. It is not designed for production use.
At startup time, MemoryRealm loads information about all users, and their
corresponding roles, from an XML document (by default, this document is loaded from $CATALINA_HOME/conf/tomcat-users.xml). Changes to the data
in this file are not recognized until Tomcat is restarted.
Realm Element Attributes
To configure MemoryRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.MemoryRealm" here.
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
Absolute or relative (to $CATALINA_HOME) pathname of the XML document
containing our valid usernames, passwords, and roles. See below for more
information on the format of this file. If not specified, the value
conf/tomcat-users.xml is used.
User File Format
The users file (by default, conf/tomcat-users.xml must be an
XML document, with a root element <tomcat-users>. Nested
inside the root element will be a <user> element for each
valid user, consisting of the following attributes:
name - Username this user must log on with.
password - Password this user must log on with (in
clear text if the digest attribute was not set on the
<Realm> element, or digested appropriately as
described here otherwise).
roles - Comma-delimited list of the role names
associated with this user.
Example
The default installation of Tomcat 4 is configured with a MemoryRealm
nested inside the <Engine> element, so that it applies
to all virtual hosts and web applications. The default contents of the
conf/tomcat-users.xml file is:
<tomcat-users>
<user name="tomcat" password="tomcat" roles="tomcat" />
<user name="role1" password="tomcat" roles="role1" />
<user name="both" password="tomcat" roles="tomcat,role1" />
</tomcat-users>
Additional Notes
MemoryRealm operates according to the following rules:
When Tomcat first starts up, it loads all defined users and their
associated information from the users file. Changes to the data in
this file will not be recognized until Tomcat is
restarted.
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser).
Administering the information in the users file is the responsibility
of your application. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
For each of the standard Realm implementations, the user's
password (by default) is stored in clear text. In many environments, this is
undesireable because casual observers of the authentication data can collect
enough information to log on successfully, and impersonate other users.
To avoid this problem, the standard implementations support the concept of
digesting user passwords. This causes the stored version of the
passwords to be encoded (in a form that is not easily reversible), but that
the Realm implementation can still utilize for authentication.
Digested passwords are selected by specifying the digest
attribute on your <Realm> element. The value for this
attribute must be one of the digest algorithms supported by the
java.security.MessageDigest class (SHA, MD2, or MD5). When you
select this option, the contents of the password that is stored in the
Realm must be the cleartext version of the password, as digested
by the specified algorithm.
When the authenticate() method of the Realm is called, the
(cleartext) password specified by the user is itself digested by the same
algorithm, and the result is compared with the value returned by the
Realm. An equal match implies that the cleartext version of the
original password is the same as the one presented by the user, so that this
user should be authorized.
To calculate the digested value of a cleartext password, two convenience
techniques are supported:
If you are writing an application that needs to calculate digested
passowrds dynamically, call the static Digest() method of the
org.apache.catalina.realm.RealmBase class, passing the
cleartext password and the digest algorithm name as arguments. This
method will return the digested password.
If you want to execute a command line utility to calculate the digested
password, simply execute
java org.apache.catalina.realm.RealmBase \
-a {algorithm} {cleartext-password}
and the digested version of this cleartext password will be returned to
standard output.
To use either of the above techniques, the
$CATALINA_HOME/server/lib/catalina.jar file will need to be
on your class path to make the RealmBase class available.
The example application shipped with Tomcat 4 includes an area that is
protected by a security constraint, utilizing form-based login. To access it,
point your browser at
http://localhost:8080/examples/jsp/security/protected/
and log on with one of the usernames and passwords described for the default
MemoryRealm.
If you wish to use the Manager Application
to deploy and undeploy applications in a running Tomcat 4 installation, you
MUST add the "manager" role to at least one username in your selected Realm
implementation. This is because the manager web application itself uses a
security constraint that requires role "manager" to access ANY request URI
within that application.
For security reasons, no username in the default Realm (i.e. using
conf/tomcat-users.xml is assigned the "manager" role. Therfore,
no one will be able to utilize the features of this application until the
Tomcat administrator specifically assigns this role to one or more users.
/images/void.gif) |
Bootstrap
|
System
|
Common
/ \
Catalina Shared
/ \
Webapp1 Webapp2 ...
| , Section 12. For a more introductory level
document for web application developers as well as administrators, see
(FIXME - link to backgrounder on container managed security
to be provided).
For information about utilizing the Single Sign On feature of
Tomcat 4 (allowing a user to authenticate themselves once across the entire
set of web applications associated with a virtual host), see
here.
A Realm is a "database" of usernames and passwords that
identify valid users of a web application (or set of web applications), plus
an enumeration of the list of roles associated with each valid user.
You can think of roles as similar to groups in Unix-like operating
systems, because access to specific web application resources is granted to
all users possessing a particular role (rather than enumerating the list of
associated usernames). A particular user can have any number of roles
associated with their username.
Although the Servlet Specification describes a portable mechanism for
applications to declare their security requirements (in the
web.xml deployment descriptor), there is no portable API
defining the interface between a servlet container and the associated user
and role information. In many cases, however, it is desireable to "connect"
a servlet container to some existing authentication database or mechanism
that already exists in the production environment. Therefore, Tomcat 4
defines a Java interface (org.apache.catalina.Realm) that
can be implemented by "plug in" components to establish this connection.
Three standard plug-ins are provided, supporting connection to three different
sources of authentication information:
JDBCRealm - Accesses authentication information
stored in a relational database, accessed via a JDBC driver.
JNDIRealm - Accesses authentication information
stored in an LDAP based directory server, accessed via a JNDI provider.
MemoryRealm - Accesses authentication
information stored in an in-memory object collection, which is initialized
from an XML document (conf/tomcat-users.xml).
It is also possible to write your own Realm implementation,
and integrate it with Tomcat 4. However, doing this is beyond the scope of
this document. See (FIXME - reference to developer stuff)
for more information.
Before getting into the details of the standard Realm implementations, it is
important to understand, in general terms, how a Realm is configured. In
general, you will be adding an XML element to your conf/server.xml
configuration file, that looks something like this:
<Realm className="... class name for this implementation"
... other attributes for this implementation .../>
The <Realm> element can be nested inside one of three
different elements, which has a direct impact on the "scope" of that Realm
(i.e. which web applications will share the same authentication information):
Inside an <Engine> element - This Realm will be shared
across ALL web applications on ALL virtual hosts, UNLESS it is overridden
by a Realm element nested inside a subordinate <Host>
or <Context> element.
Inside a <Host> element - This Realm will be shared across
ALL web applications for THIS virtual host, UNLESS it is overridden
by a Realm element nested inside a subordinate <Context>
element.
Inside a <Context> element - This Realm will be used ONLY
for THIS web application.
Introduction
JDBCRealm is an implementation of the Tomcat 4
Realm interface that looks up users in a relational database
accessed via a JDBC driver. There is substantial configuration flexibility
that lets you adapt to existing table and column names, as long as your
database structure conforms to the following requirements:
There must be a table, referenced below as the users table,
that contains one row for every valid user that this Realm
should recognize.
The users table must contain at least two columns (it may
contain more if your existing applications required it):
Username to be recognized by Tomcat when the user logs in.
Password to be recognized by Tomcat when the user logs in.
This value may in cleartext or digested - see below for more
information.
There must be a table, referenced below as the user roles table,
that contains one row for every valid role that is assigned to a
particular user. It is legal for a user to have zero, one, or more than
one valid role.
The user roles table must contain at least two columns (it may
contain more if your existing applications required it):
Username to be recognized by Tomcat (same value as is specified
in the users table).
Role name of a valid role associated with this user.
Quick Start
To set up Tomcat to use JDBCRealm, you will need to follow these steps:
If you have not yet done so, create tables and columns in your database
that conform to the requirements described above.
Configure a database username and password for use by Tomcat, that has
at least read only access to the tables described above. (Tomcat will
never attempt to write to these tables.)
Place a copy of the JDBC driver you will be using inside the
$CATALINA_HOME/server/lib directory (if you do not need it
visible to web applications) or $CATALINA_HOME/common/lib
(if it will be used both by Tomcat 4 and by your apps).
Note that only JAR files are recognized!
Set up a <Realm> element, as described below, in your
$CATALINA_HOME/conf/server.xml file.
Restart Tomcat 4 if it is already running.
Realm Element Attributes
To configure JDBCRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.JDBCRealm" here.
The database username used to establish a JDBC connection.
The database password used to establish a JDBC connection.
The database URL used to establish a JDBC connection.
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
The fully qualified Java class name of the JDBC driver to be used.
Consult the documentation for your JDBC driver for the appropriate
value.
The name of the column, in the user roles table, that
contains the name of a role assigned to this user.
The name of the column, in the users table, that contains
the password for this user (either in clear text, or digested if the
digest attribute is set).
The name of the column, in the users and user roles
tables, that contains the username of this user.
The name of the table that contains one row for each role
assigned to a particular username. This table must include at
least the columns named by the userNameCol and
roleNameCol attributes.
The name of the table that contains one row for each username
to be recognized by Tomcat. This table must include at least the columns
named by the userNameCol and userCredCol
attributes.
Example
An example SQL script to create the needed tables might look something
like this (adapt the syntax as required for your particular database):
create table users (
user_name varchar(15) not null primary key,
user_pass varchar(15) not null
);
create table user_roles (
user_name varchar(15) not null,
role_name varchar(15) not null,
primary key (user_name, role_name)
);
Example Realm elements are included (commented out) in the
default $CATALINA_HOME/conf/server.xml file. Here's an example
for using a MySQL database called "authority", configured with the tables
described above, and accessed with username "dbuser" and password "dbpass":
<Realm className="org.apache.catalina.realm.JDBCRealm" debug="99"
driverName="org.gjt.mm.mysql.Driver"
connectionURL="jdbc:mysql://localhost/authority?user=dbuser;password=dbpass"
userTable="users" userNameCol="user_name" userCredCol="user_pass"
userRoleTable="user_roles" roleNameCol="role_name"/>
Additional Notes
JDBCRealm operates according to the following rules:
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm. Thus, any changes you have made to the database
directly (new users, changed passwords or roles, etc.) will be immediately
reflected.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser). Any changes to the database information for an
already authenticated user will not be reflected until
the next time that user logs on again.
Administering the information in the users and user roles
table is the responsibility of your own applications. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
Introduction
JNDIRealm is an implementation of the Tomcat 4
Realm interface that looks up users in a directory server
accessed by a JNDI provider (typically, the standard LDAP provider that
is available with the JNDI API classes). There is substantial configuration
flexibility that lets you adapt to the existing schema inside your directory
server, as long as it conforms to the following requirements:
Each user that can be authenticated is represented by an individual
element in the top level DirContext that is accessed
via the connectionURL attribute.
The user element must have the following characteristics:
The distinguished name (dn) attribute of this element
contains the username that is presented for authentication.
There must be an attribute (identified by the userPassword
attribute of our Realm element) that contains the user's
password, either in clear text or digested (see below for more info).
Each group of users that has been assigned a particular role is
represented by an individual element in the top level
DirContext that is accessed via the
connectionURL attribute.
The user group element must have the following characteristics:
The set of all possible groups of interest can be selected by an LDAP
search pattern configured by the roleSearch attribute
of our Realm element.
The roleSearch pattern optionally includes pattern
replacements "{0}" for the distinguished name, and/or "{1} for the
username, of the authenticated user for which roles will be
retrieved.
The roleBase attribute can be set to the element that
is the base of the search for matching roles. If not specified,
the entire directory context will be searched.
The roleSubtree attribute can be set to true
if you wish to search the entire subtree of the directory context.
The default value of false requests a search of only the
current level.
The element includes an attribute (whose name is configured by the
roleName attribute of our Realm element)
containing the name of the role represented by this element.
There must be an administrator username and password that Tomcat can
use to establish a connection to the directory server, with at least
read-only access to the information described above. A future
version of Tomcat will support an option to use the user's username and
password to attempt this connection.
Quick Start
To set up Tomcat to use JNDIRealm, you will need to follow these steps:
Make sure your directory server is configured with a schema that matches
the requirements listed above.
Configure a username and password for use by Tomcat, that has
at least read only access to the information described above. (Tomcat will
never attempt to modify this information.)
Place a copy of the JNDI driver you will be using (typically
ldap.jar available with JNDI) inside the
$CATALINA_HOME/server/lib directory (if you do not need it
visible to web applications) or $CATALINA_HOME/common/lib
(if it will be used both by Tomcat 4 and by your apps).
Set up a <Realm> element, as described below, in your
$CATALINA_HOME/conf/server.xml file.
Restart Tomcat 4 if it is already running.
Realm Element Attributes
To configure JNDIRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.JDBCRealm" here.
The directory server username used to establish a JNDI connection.
The directory server password used to establish a JNDI connection.
The directory server URL used to establish a JNDI connection.
The fully qualified Java class name of the JNDI context factory to be
used for this connection. By default, the standard JNDI LDAP provider
is used (com.sun.jndi.ldap.LdapCtxFactory).
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
The base element for role searches. If not specified, the top level
element in the directory context will be used.
The name of the directory server attribute containing the role name.
An LDAP search pattern for selecting roles in this Realm, following the
syntax supported by the java.text.MessageFormat class. Use
{0} to substitute in the distinguished name of the user you
want roles for, and/or {1} to substitute in the username of
the user you want roles for.
Set to true if you want role searches to search subtrees
of the element selected by roleBase. The default value of
false causes only the top level element to be searched.
The name of the directory server attribute (in the user element) that
contains the cleartext or digested user password (depending on the setting
of the digest attribute).
An LDAP search pattern for selecting users in this Realm, following the
syntax supported by the java.text.MessageFormat class. Use
{0} to substitute in the distinguished name of the user you
want to select.
Example
Creation of the appropriate schema in your directory server is beyond the
scope of this document, because it is unique to each directory server
implementation. In the examples below, we will assume that you are using a
distribution of the OpenLDAP directory server (version 2.0.11 or later), which
can be downloaded from
http://www.openldap.org. Assume that
your slapd.conf file contains the following settings
(among others):
database ldbm
suffix dc="mycompany",dc="com"
rootdn "cn=Manager,dc=mycompany,dc=com"
rootpw secret
These settings help us identify values for the values to be specified for
connectionName, and connectionPassword, and we
will assume for connectionURL that the directory server runs on
the same machine as Tomcat. See
http://java.sun.com/products/jndi/docs.html
for more information about configuring and using the JNDI LDAP provider.
Next, assume that this directory server has been populated with elements
as shown below (in LDIF format), which define the same users and roles
as the default $CATALINA_HOME/conf/tomcat-users.xml does for
MemoryRealm:
# Define a user named 'tomcat'
dn: cn=tomcat,dc=mycompany,dc=com
cn: tomcat
userPassword: tomcat
sn: Tomcat User
objectClass: person
# Define a user named 'role1'
dn: cn=role1,dc=mycompany,dc=com
cn: role1
userPassword: tomcat
sn: Role1 User
objectClass: person
# Define a user named 'both'
dn: cn=both,dc=mycompany,dc=com
cn: both
userPassword: tomcat
sn: Both User
objectClass: person
# Define an entry to base role searches on
dn: dc=roles,dc=mycompany,dc=com
cn: roles
objectClass: person
sn: Roles Entry
# Define all members of the 'tomcat' role
dn: cn=tomcat,dc=roles,dc=mycompany,dc=com
cn: tomcat
objectClass: groupOfUniqueNames
uniqueMember: cn=tomcat,dc=mycompany,dc=com
uniqueMember: cn=both,dc=mycompany,dc=com
# Define all members of the 'role1' role
dn: cn=role1,dc=roles,dc=mycompany,dc=com
cn: role1
objectClass: groupOfUniqueNames
uniqueMember: cn=role1,dc=mycompany,dc=com
uniqueMember: cn=both,dc=mycompany,dc=com
An example Realm element for the OpenLDAP directory server
configured as described above might look like this:
<Realm className="org.apache.catalina.realm.JNDIRealm" debug="99"
connectionName="cn=Manager,dc=mycompany,dc=com"
connectionPassword="secret"
connectionURL="ldap://localhost:389"
roleBase="dc=roles,dc=mcclan,dc=net"
roleName="cn"
roleSearch="(uniqueMember={0})"
roleSubtree="false"
userPassword="userPassword"
userPattern="cn={0},dc=mycompany,dc=com"
/>
Additional Notes
JNDIRealm operates according to the following rules:
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm. Thus, any changes you have made to the database
directly (new users, changed passwords or roles, etc.) will be immediately
reflected.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser). Any changes to the database information for an
already authenticated user will not be reflected until
the next time that user logs on again.
Administering the information in the directory server
is the responsibility of your own applications. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
Introduction
MemoryRealm is a simple demonstration implementation of the
Tomcat 4 Realm interface. It is not designed for production use.
At startup time, MemoryRealm loads information about all users, and their
corresponding roles, from an XML document (by default, this document is loaded from $CATALINA_HOME/conf/tomcat-users.xml). Changes to the data
in this file are not recognized until Tomcat is restarted.
Realm Element Attributes
To configure MemoryRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.MemoryRealm" here.
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
Absolute or relative (to $CATALINA_HOME) pathname of the XML document
containing our valid usernames, passwords, and roles. See below for more
information on the format of this file. If not specified, the value
conf/tomcat-users.xml is used.
User File Format
The users file (by default, conf/tomcat-users.xml must be an
XML document, with a root element <tomcat-users>. Nested
inside the root element will be a <user> element for each
valid user, consisting of the following attributes:
name - Username this user must log on with.
password - Password this user must log on with (in
clear text if the digest attribute was not set on the
<Realm> element, or digested appropriately as
described here otherwise).
roles - Comma-delimited list of the role names
associated with this user.
Example
The default installation of Tomcat 4 is configured with a MemoryRealm
nested inside the <Engine> element, so that it applies
to all virtual hosts and web applications. The default contents of the
conf/tomcat-users.xml file is:
<tomcat-users>
<user name="tomcat" password="tomcat" roles="tomcat" />
<user name="role1" password="tomcat" roles="role1" />
<user name="both" password="tomcat" roles="tomcat,role1" />
</tomcat-users>
Additional Notes
MemoryRealm operates according to the following rules:
When Tomcat first starts up, it loads all defined users and their
associated information from the users file. Changes to the data in
this file will not be recognized until Tomcat is
restarted.
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser).
Administering the information in the users file is the responsibility
of your application. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
For each of the standard Realm implementations, the user's
password (by default) is stored in clear text. In many environments, this is
undesireable because casual observers of the authentication data can collect
enough information to log on successfully, and impersonate other users.
To avoid this problem, the standard implementations support the concept of
digesting user passwords. This causes the stored version of the
passwords to be encoded (in a form that is not easily reversible), but that
the Realm implementation can still utilize for authentication.
Digested passwords are selected by specifying the digest
attribute on your <Realm> element. The value for this
attribute must be one of the digest algorithms supported by the
java.security.MessageDigest class (SHA, MD2, or MD5). When you
select this option, the contents of the password that is stored in the
Realm must be the cleartext version of the password, as digested
by the specified algorithm.
When the authenticate() method of the Realm is called, the
(cleartext) password specified by the user is itself digested by the same
algorithm, and the result is compared with the value returned by the
Realm. An equal match implies that the cleartext version of the
original password is the same as the one presented by the user, so that this
user should be authorized.
To calculate the digested value of a cleartext password, two convenience
techniques are supported:
If you are writing an application that needs to calculate digested
passowrds dynamically, call the static Digest() method of the
org.apache.catalina.realm.RealmBase class, passing the
cleartext password and the digest algorithm name as arguments. This
method will return the digested password.
If you want to execute a command line utility to calculate the digested
password, simply execute
java org.apache.catalina.realm.RealmBase \
-a {algorithm} {cleartext-password}
and the digested version of this cleartext password will be returned to
standard output.
To use either of the above techniques, the
$CATALINA_HOME/server/lib/catalina.jar file will need to be
on your class path to make the RealmBase class available.
The example application shipped with Tomcat 4 includes an area that is
protected by a security constraint, utilizing form-based login. To access it,
point your browser at
http://localhost:8080/examples/jsp/security/protected/
and log on with one of the usernames and passwords described for the default
MemoryRealm.
If you wish to use the Manager Application
to deploy and undeploy applications in a running Tomcat 4 installation, you
MUST add the "manager" role to at least one username in your selected Realm
implementation. This is because the manager web application itself uses a
security constraint that requires role "manager" to access ANY request URI
within that application.
For security reasons, no username in the default Realm (i.e. using
conf/tomcat-users.xml is assigned the "manager" role. Therfore,
no one will be able to utilize the features of this application until the
Tomcat administrator specifically assigns this role to one or more users.
/images/void.gif) | , Section 12. For a more introductory level
document for web application developers as well as administrators, see
(FIXME - link to backgrounder on container managed security
to be provided).
For information about utilizing the Single Sign On feature of
Tomcat 4 (allowing a user to authenticate themselves once across the entire
set of web applications associated with a virtual host), see
here.
A Realm is a "database" of usernames and passwords that
identify valid users of a web application (or set of web applications), plus
an enumeration of the list of roles associated with each valid user.
You can think of roles as similar to groups in Unix-like operating
systems, because access to specific web application resources is granted to
all users possessing a particular role (rather than enumerating the list of
associated usernames). A particular user can have any number of roles
associated with their username.
Although the Servlet Specification describes a portable mechanism for
applications to declare their security requirements (in the
web.xml deployment descriptor), there is no portable API
defining the interface between a servlet container and the associated user
and role information. In many cases, however, it is desireable to "connect"
a servlet container to some existing authentication database or mechanism
that already exists in the production environment. Therefore, Tomcat 4
defines a Java interface (org.apache.catalina.Realm) that
can be implemented by "plug in" components to establish this connection.
Three standard plug-ins are provided, supporting connection to three different
sources of authentication information:
JDBCRealm - Accesses authentication information
stored in a relational database, accessed via a JDBC driver.
JNDIRealm - Accesses authentication information
stored in an LDAP based directory server, accessed via a JNDI provider.
MemoryRealm - Accesses authentication
information stored in an in-memory object collection, which is initialized
from an XML document (conf/tomcat-users.xml).
It is also possible to write your own Realm implementation,
and integrate it with Tomcat 4. However, doing this is beyond the scope of
this document. See (FIXME - reference to developer stuff)
for more information.
Before getting into the details of the standard Realm implementations, it is
important to understand, in general terms, how a Realm is configured. In
general, you will be adding an XML element to your conf/server.xml
configuration file, that looks something like this:
<Realm className="... class name for this implementation"
... other attributes for this implementation .../>
The <Realm> element can be nested inside one of three
different elements, which has a direct impact on the "scope" of that Realm
(i.e. which web applications will share the same authentication information):
Inside an <Engine> element - This Realm will be shared
across ALL web applications on ALL virtual hosts, UNLESS it is overridden
by a Realm element nested inside a subordinate <Host>
or <Context> element.
Inside a <Host> element - This Realm will be shared across
ALL web applications for THIS virtual host, UNLESS it is overridden
by a Realm element nested inside a subordinate <Context>
element.
Inside a <Context> element - This Realm will be used ONLY
for THIS web application.
Introduction
JDBCRealm is an implementation of the Tomcat 4
Realm interface that looks up users in a relational database
accessed via a JDBC driver. There is substantial configuration flexibility
that lets you adapt to existing table and column names, as long as your
database structure conforms to the following requirements:
There must be a table, referenced below as the users table,
that contains one row for every valid user that this Realm
should recognize.
The users table must contain at least two columns (it may
contain more if your existing applications required it):
Username to be recognized by Tomcat when the user logs in.
Password to be recognized by Tomcat when the user logs in.
This value may in cleartext or digested - see below for more
information.
There must be a table, referenced below as the user roles table,
that contains one row for every valid role that is assigned to a
particular user. It is legal for a user to have zero, one, or more than
one valid role.
The user roles table must contain at least two columns (it may
contain more if your existing applications required it):
Username to be recognized by Tomcat (same value as is specified
in the users table).
Role name of a valid role associated with this user.
Quick Start
To set up Tomcat to use JDBCRealm, you will need to follow these steps:
If you have not yet done so, create tables and columns in your database
that conform to the requirements described above.
Configure a database username and password for use by Tomcat, that has
at least read only access to the tables described above. (Tomcat will
never attempt to write to these tables.)
Place a copy of the JDBC driver you will be using inside the
$CATALINA_HOME/server/lib directory (if you do not need it
visible to web applications) or $CATALINA_HOME/common/lib
(if it will be used both by Tomcat 4 and by your apps).
Note that only JAR files are recognized!
Set up a <Realm> element, as described below, in your
$CATALINA_HOME/conf/server.xml file.
Restart Tomcat 4 if it is already running.
Realm Element Attributes
To configure JDBCRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.JDBCRealm" here.
The database username used to establish a JDBC connection.
The database password used to establish a JDBC connection.
The database URL used to establish a JDBC connection.
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
The fully qualified Java class name of the JDBC driver to be used.
Consult the documentation for your JDBC driver for the appropriate
value.
The name of the column, in the user roles table, that
contains the name of a role assigned to this user.
The name of the column, in the users table, that contains
the password for this user (either in clear text, or digested if the
digest attribute is set).
The name of the column, in the users and user roles
tables, that contains the username of this user.
The name of the table that contains one row for each role
assigned to a particular username. This table must include at
least the columns named by the userNameCol and
roleNameCol attributes.
The name of the table that contains one row for each username
to be recognized by Tomcat. This table must include at least the columns
named by the userNameCol and userCredCol
attributes.
Example
An example SQL script to create the needed tables might look something
like this (adapt the syntax as required for your particular database):
create table users (
user_name varchar(15) not null primary key,
user_pass varchar(15) not null
);
create table user_roles (
user_name varchar(15) not null,
role_name varchar(15) not null,
primary key (user_name, role_name)
);
Example Realm elements are included (commented out) in the
default $CATALINA_HOME/conf/server.xml file. Here's an example
for using a MySQL database called "authority", configured with the tables
described above, and accessed with username "dbuser" and password "dbpass":
<Realm className="org.apache.catalina.realm.JDBCRealm" debug="99"
driverName="org.gjt.mm.mysql.Driver"
connectionURL="jdbc:mysql://localhost/authority?user=dbuser;password=dbpass"
userTable="users" userNameCol="user_name" userCredCol="user_pass"
userRoleTable="user_roles" roleNameCol="role_name"/>
Additional Notes
JDBCRealm operates according to the following rules:
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm. Thus, any changes you have made to the database
directly (new users, changed passwords or roles, etc.) will be immediately
reflected.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser). Any changes to the database information for an
already authenticated user will not be reflected until
the next time that user logs on again.
Administering the information in the users and user roles
table is the responsibility of your own applications. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
Introduction
JNDIRealm is an implementation of the Tomcat 4
Realm interface that looks up users in a directory server
accessed by a JNDI provider (typically, the standard LDAP provider that
is available with the JNDI API classes). There is substantial configuration
flexibility that lets you adapt to the existing schema inside your directory
server, as long as it conforms to the following requirements:
Each user that can be authenticated is represented by an individual
element in the top level DirContext that is accessed
via the connectionURL attribute.
The user element must have the following characteristics:
The distinguished name (dn) attribute of this element
contains the username that is presented for authentication.
There must be an attribute (identified by the userPassword
attribute of our Realm element) that contains the user's
password, either in clear text or digested (see below for more info).
Each group of users that has been assigned a particular role is
represented by an individual element in the top level
DirContext that is accessed via the
connectionURL attribute.
The user group element must have the following characteristics:
The set of all possible groups of interest can be selected by an LDAP
search pattern configured by the roleSearch attribute
of our Realm element.
The roleSearch pattern optionally includes pattern
replacements "{0}" for the distinguished name, and/or "{1} for the
username, of the authenticated user for which roles will be
retrieved.
The roleBase attribute can be set to the element that
is the base of the search for matching roles. If not specified,
the entire directory context will be searched.
The roleSubtree attribute can be set to true
if you wish to search the entire subtree of the directory context.
The default value of false requests a search of only the
current level.
The element includes an attribute (whose name is configured by the
roleName attribute of our Realm element)
containing the name of the role represented by this element.
There must be an administrator username and password that Tomcat can
use to establish a connection to the directory server, with at least
read-only access to the information described above. A future
version of Tomcat will support an option to use the user's username and
password to attempt this connection.
Quick Start
To set up Tomcat to use JNDIRealm, you will need to follow these steps:
Make sure your directory server is configured with a schema that matches
the requirements listed above.
Configure a username and password for use by Tomcat, that has
at least read only access to the information described above. (Tomcat will
never attempt to modify this information.)
Place a copy of the JNDI driver you will be using (typically
ldap.jar available with JNDI) inside the
$CATALINA_HOME/server/lib directory (if you do not need it
visible to web applications) or $CATALINA_HOME/common/lib
(if it will be used both by Tomcat 4 and by your apps).
Set up a <Realm> element, as described below, in your
$CATALINA_HOME/conf/server.xml file.
Restart Tomcat 4 if it is already running.
Realm Element Attributes
To configure JNDIRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.JDBCRealm" here.
The directory server username used to establish a JNDI connection.
The directory server password used to establish a JNDI connection.
The directory server URL used to establish a JNDI connection.
The fully qualified Java class name of the JNDI context factory to be
used for this connection. By default, the standard JNDI LDAP provider
is used (com.sun.jndi.ldap.LdapCtxFactory).
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
The base element for role searches. If not specified, the top level
element in the directory context will be used.
The name of the directory server attribute containing the role name.
An LDAP search pattern for selecting roles in this Realm, following the
syntax supported by the java.text.MessageFormat class. Use
{0} to substitute in the distinguished name of the user you
want roles for, and/or {1} to substitute in the username of
the user you want roles for.
Set to true if you want role searches to search subtrees
of the element selected by roleBase. The default value of
false causes only the top level element to be searched.
The name of the directory server attribute (in the user element) that
contains the cleartext or digested user password (depending on the setting
of the digest attribute).
An LDAP search pattern for selecting users in this Realm, following the
syntax supported by the java.text.MessageFormat class. Use
{0} to substitute in the distinguished name of the user you
want to select.
Example
Creation of the appropriate schema in your directory server is beyond the
scope of this document, because it is unique to each directory server
implementation. In the examples below, we will assume that you are using a
distribution of the OpenLDAP directory server (version 2.0.11 or later), which
can be downloaded from
http://www.openldap.org. Assume that
your slapd.conf file contains the following settings
(among others):
database ldbm
suffix dc="mycompany",dc="com"
rootdn "cn=Manager,dc=mycompany,dc=com"
rootpw secret
These settings help us identify values for the values to be specified for
connectionName, and connectionPassword, and we
will assume for connectionURL that the directory server runs on
the same machine as Tomcat. See
http://java.sun.com/products/jndi/docs.html
for more information about configuring and using the JNDI LDAP provider.
Next, assume that this directory server has been populated with elements
as shown below (in LDIF format), which define the same users and roles
as the default $CATALINA_HOME/conf/tomcat-users.xml does for
MemoryRealm:
# Define a user named 'tomcat'
dn: cn=tomcat,dc=mycompany,dc=com
cn: tomcat
userPassword: tomcat
sn: Tomcat User
objectClass: person
# Define a user named 'role1'
dn: cn=role1,dc=mycompany,dc=com
cn: role1
userPassword: tomcat
sn: Role1 User
objectClass: person
# Define a user named 'both'
dn: cn=both,dc=mycompany,dc=com
cn: both
userPassword: tomcat
sn: Both User
objectClass: person
# Define an entry to base role searches on
dn: dc=roles,dc=mycompany,dc=com
cn: roles
objectClass: person
sn: Roles Entry
# Define all members of the 'tomcat' role
dn: cn=tomcat,dc=roles,dc=mycompany,dc=com
cn: tomcat
objectClass: groupOfUniqueNames
uniqueMember: cn=tomcat,dc=mycompany,dc=com
uniqueMember: cn=both,dc=mycompany,dc=com
# Define all members of the 'role1' role
dn: cn=role1,dc=roles,dc=mycompany,dc=com
cn: role1
objectClass: groupOfUniqueNames
uniqueMember: cn=role1,dc=mycompany,dc=com
uniqueMember: cn=both,dc=mycompany,dc=com
An example Realm element for the OpenLDAP directory server
configured as described above might look like this:
<Realm className="org.apache.catalina.realm.JNDIRealm" debug="99"
connectionName="cn=Manager,dc=mycompany,dc=com"
connectionPassword="secret"
connectionURL="ldap://localhost:389"
roleBase="dc=roles,dc=mcclan,dc=net"
roleName="cn"
roleSearch="(uniqueMember={0})"
roleSubtree="false"
userPassword="userPassword"
userPattern="cn={0},dc=mycompany,dc=com"
/>
Additional Notes
JNDIRealm operates according to the following rules:
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm. Thus, any changes you have made to the database
directly (new users, changed passwords or roles, etc.) will be immediately
reflected.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser). Any changes to the database information for an
already authenticated user will not be reflected until
the next time that user logs on again.
Administering the information in the directory server
is the responsibility of your own applications. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
Introduction
MemoryRealm is a simple demonstration implementation of the
Tomcat 4 Realm interface. It is not designed for production use.
At startup time, MemoryRealm loads information about all users, and their
corresponding roles, from an XML document (by default, this document is loaded from $CATALINA_HOME/conf/tomcat-users.xml). Changes to the data
in this file are not recognized until Tomcat is restarted.
Realm Element Attributes
To configure MemoryRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.MemoryRealm" here.
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
Absolute or relative (to $CATALINA_HOME) pathname of the XML document
containing our valid usernames, passwords, and roles. See below for more
information on the format of this file. If not specified, the value
conf/tomcat-users.xml is used.
User File Format
The users file (by default, conf/tomcat-users.xml must be an
XML document, with a root element <tomcat-users>. Nested
inside the root element will be a <user> element for each
valid user, consisting of the following attributes:
name - Username this user must log on with.
password - Password this user must log on with (in
clear text if the digest attribute was not set on the
<Realm> element, or digested appropriately as
described here otherwise).
roles - Comma-delimited list of the role names
associated with this user.
Example
The default installation of Tomcat 4 is configured with a MemoryRealm
nested inside the <Engine> element, so that it applies
to all virtual hosts and web applications. The default contents of the
conf/tomcat-users.xml file is:
<tomcat-users>
<user name="tomcat" password="tomcat" roles="tomcat" />
<user name="role1" password="tomcat" roles="role1" />
<user name="both" password="tomcat" roles="tomcat,role1" />
</tomcat-users>
Additional Notes
MemoryRealm operates according to the following rules:
When Tomcat first starts up, it loads all defined users and their
associated information from the users file. Changes to the data in
this file will not be recognized until Tomcat is
restarted.
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser).
Administering the information in the users file is the responsibility
of your application. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
For each of the standard Realm implementations, the user's
password (by default) is stored in clear text. In many environments, this is
undesireable because casual observers of the authentication data can collect
enough information to log on successfully, and impersonate other users.
To avoid this problem, the standard implementations support the concept of
digesting user passwords. This causes the stored version of the
passwords to be encoded (in a form that is not easily reversible), but that
the Realm implementation can still utilize for authentication.
Digested passwords are selected by specifying the digest
attribute on your <Realm> element. The value for this
attribute must be one of the digest algorithms supported by the
java.security.MessageDigest class (SHA, MD2, or MD5). When you
select this option, the contents of the password that is stored in the
Realm must be the cleartext version of the password, as digested
by the specified algorithm.
When the authenticate() method of the Realm is called, the
(cleartext) password specified by the user is itself digested by the same
algorithm, and the result is compared with the value returned by the
Realm. An equal match implies that the cleartext version of the
original password is the same as the one presented by the user, so that this
user should be authorized.
To calculate the digested value of a cleartext password, two convenience
techniques are supported:
If you are writing an application that needs to calculate digested
passowrds dynamically, call the static Digest() method of the
org.apache.catalina.realm.RealmBase class, passing the
cleartext password and the digest algorithm name as arguments. This
method will return the digested password.
If you want to execute a command line utility to calculate the digested
password, simply execute
java org.apache.catalina.realm.RealmBase \
-a {algorithm} {cleartext-password}
and the digested version of this cleartext password will be returned to
standard output.
To use either of the above techniques, the
$CATALINA_HOME/server/lib/catalina.jar file will need to be
on your class path to make the RealmBase class available.
The example application shipped with Tomcat 4 includes an area that is
protected by a security constraint, utilizing form-based login. To access it,
point your browser at
http://localhost:8080/examples/jsp/security/protected/
and log on with one of the usernames and passwords described for the default
MemoryRealm.
If you wish to use the Manager Application
to deploy and undeploy applications in a running Tomcat 4 installation, you
MUST add the "manager" role to at least one username in your selected Realm
implementation. This is because the manager web application itself uses a
security constraint that requires role "manager" to access ANY request URI
within that application.
For security reasons, no username in the default Realm (i.e. using
conf/tomcat-users.xml is assigned the "manager" role. Therfore,
no one will be able to utilize the features of this application until the
Tomcat administrator specifically assigns this role to one or more users.
/images/void.gif) | , Section 12. For a more introductory level
document for web application developers as well as administrators, see
(FIXME - link to backgrounder on container managed security
to be provided).
For information about utilizing the Single Sign On feature of
Tomcat 4 (allowing a user to authenticate themselves once across the entire
set of web applications associated with a virtual host), see
here.
A Realm is a "database" of usernames and passwords that
identify valid users of a web application (or set of web applications), plus
an enumeration of the list of roles associated with each valid user.
You can think of roles as similar to groups in Unix-like operating
systems, because access to specific web application resources is granted to
all users possessing a particular role (rather than enumerating the list of
associated usernames). A particular user can have any number of roles
associated with their username.
Although the Servlet Specification describes a portable mechanism for
applications to declare their security requirements (in the
web.xml deployment descriptor), there is no portable API
defining the interface between a servlet container and the associated user
and role information. In many cases, however, it is desireable to "connect"
a servlet container to some existing authentication database or mechanism
that already exists in the production environment. Therefore, Tomcat 4
defines a Java interface (org.apache.catalina.Realm) that
can be implemented by "plug in" components to establish this connection.
Three standard plug-ins are provided, supporting connection to three different
sources of authentication information:
JDBCRealm - Accesses authentication information
stored in a relational database, accessed via a JDBC driver.
JNDIRealm - Accesses authentication information
stored in an LDAP based directory server, accessed via a JNDI provider.
MemoryRealm - Accesses authentication
information stored in an in-memory object collection, which is initialized
from an XML document (conf/tomcat-users.xml).
It is also possible to write your own Realm implementation,
and integrate it with Tomcat 4. However, doing this is beyond the scope of
this document. See (FIXME - reference to developer stuff)
for more information.
Before getting into the details of the standard Realm implementations, it is
important to understand, in general terms, how a Realm is configured. In
general, you will be adding an XML element to your conf/server.xml
configuration file, that looks something like this:
<Realm className="... class name for this implementation"
... other attributes for this implementation .../>
The <Realm> element can be nested inside one of three
different elements, which has a direct impact on the "scope" of that Realm
(i.e. which web applications will share the same authentication information):
Inside an <Engine> element - This Realm will be shared
across ALL web applications on ALL virtual hosts, UNLESS it is overridden
by a Realm element nested inside a subordinate <Host>
or <Context> element.
Inside a <Host> element - This Realm will be shared across
ALL web applications for THIS virtual host, UNLESS it is overridden
by a Realm element nested inside a subordinate <Context>
element.
Inside a <Context> element - This Realm will be used ONLY
for THIS web application.
Introduction
JDBCRealm is an implementation of the Tomcat 4
Realm interface that looks up users in a relational database
accessed via a JDBC driver. There is substantial configuration flexibility
that lets you adapt to existing table and column names, as long as your
database structure conforms to the following requirements:
There must be a table, referenced below as the users table,
that contains one row for every valid user that this Realm
should recognize.
The users table must contain at least two columns (it may
contain more if your existing applications required it):
Username to be recognized by Tomcat when the user logs in.
Password to be recognized by Tomcat when the user logs in.
This value may in cleartext or digested - see below for more
information.
There must be a table, referenced below as the user roles table,
that contains one row for every valid role that is assigned to a
particular user. It is legal for a user to have zero, one, or more than
one valid role.
The user roles table must contain at least two columns (it may
contain more if your existing applications required it):
Username to be recognized by Tomcat (same value as is specified
in the users table).
Role name of a valid role associated with this user.
Quick Start
To set up Tomcat to use JDBCRealm, you will need to follow these steps:
If you have not yet done so, create tables and columns in your database
that conform to the requirements described above.
Configure a database username and password for use by Tomcat, that has
at least read only access to the tables described above. (Tomcat will
never attempt to write to these tables.)
Place a copy of the JDBC driver you will be using inside the
$CATALINA_HOME/server/lib directory (if you do not need it
visible to web applications) or $CATALINA_HOME/common/lib
(if it will be used both by Tomcat 4 and by your apps).
Note that only JAR files are recognized!
Set up a <Realm> element, as described below, in your
$CATALINA_HOME/conf/server.xml file.
Restart Tomcat 4 if it is already running.
Realm Element Attributes
To configure JDBCRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.JDBCRealm" here.
The database username used to establish a JDBC connection.
The database password used to establish a JDBC connection.
The database URL used to establish a JDBC connection.
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
The fully qualified Java class name of the JDBC driver to be used.
Consult the documentation for your JDBC driver for the appropriate
value.
The name of the column, in the user roles table, that
contains the name of a role assigned to this user.
The name of the column, in the users table, that contains
the password for this user (either in clear text, or digested if the
digest attribute is set).
The name of the column, in the users and user roles
tables, that contains the username of this user.
The name of the table that contains one row for each role
assigned to a particular username. This table must include at
least the columns named by the userNameCol and
roleNameCol attributes.
The name of the table that contains one row for each username
to be recognized by Tomcat. This table must include at least the columns
named by the userNameCol and userCredCol
attributes.
Example
An example SQL script to create the needed tables might look something
like this (adapt the syntax as required for your particular database):
create table users (
user_name varchar(15) not null primary key,
user_pass varchar(15) not null
);
create table user_roles (
user_name varchar(15) not null,
role_name varchar(15) not null,
primary key (user_name, role_name)
);
Example Realm elements are included (commented out) in the
default $CATALINA_HOME/conf/server.xml file. Here's an example
for using a MySQL database called "authority", configured with the tables
described above, and accessed with username "dbuser" and password "dbpass":
<Realm className="org.apache.catalina.realm.JDBCRealm" debug="99"
driverName="org.gjt.mm.mysql.Driver"
connectionURL="jdbc:mysql://localhost/authority?user=dbuser;password=dbpass"
userTable="users" userNameCol="user_name" userCredCol="user_pass"
userRoleTable="user_roles" roleNameCol="role_name"/>
Additional Notes
JDBCRealm operates according to the following rules:
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm. Thus, any changes you have made to the database
directly (new users, changed passwords or roles, etc.) will be immediately
reflected.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser). Any changes to the database information for an
already authenticated user will not be reflected until
the next time that user logs on again.
Administering the information in the users and user roles
table is the responsibility of your own applications. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
Introduction
JNDIRealm is an implementation of the Tomcat 4
Realm interface that looks up users in a directory server
accessed by a JNDI provider (typically, the standard LDAP provider that
is available with the JNDI API classes). There is substantial configuration
flexibility that lets you adapt to the existing schema inside your directory
server, as long as it conforms to the following requirements:
Each user that can be authenticated is represented by an individual
element in the top level DirContext that is accessed
via the connectionURL attribute.
The user element must have the following characteristics:
The distinguished name (dn) attribute of this element
contains the username that is presented for authentication.
There must be an attribute (identified by the userPassword
attribute of our Realm element) that contains the user's
password, either in clear text or digested (see below for more info).
Each group of users that has been assigned a particular role is
represented by an individual element in the top level
DirContext that is accessed via the
connectionURL attribute.
The user group element must have the following characteristics:
The set of all possible groups of interest can be selected by an LDAP
search pattern configured by the roleSearch attribute
of our Realm element.
The roleSearch pattern optionally includes pattern
replacements "{0}" for the distinguished name, and/or "{1} for the
username, of the authenticated user for which roles will be
retrieved.
The roleBase attribute can be set to the element that
is the base of the search for matching roles. If not specified,
the entire directory context will be searched.
The roleSubtree attribute can be set to true
if you wish to search the entire subtree of the directory context.
The default value of false requests a search of only the
current level.
The element includes an attribute (whose name is configured by the
roleName attribute of our Realm element)
containing the name of the role represented by this element.
There must be an administrator username and password that Tomcat can
use to establish a connection to the directory server, with at least
read-only access to the information described above. A future
version of Tomcat will support an option to use the user's username and
password to attempt this connection.
Quick Start
To set up Tomcat to use JNDIRealm, you will need to follow these steps:
Make sure your directory server is configured with a schema that matches
the requirements listed above.
Configure a username and password for use by Tomcat, that has
at least read only access to the information described above. (Tomcat will
never attempt to modify this information.)
Place a copy of the JNDI driver you will be using (typically
ldap.jar available with JNDI) inside the
$CATALINA_HOME/server/lib directory (if you do not need it
visible to web applications) or $CATALINA_HOME/common/lib
(if it will be used both by Tomcat 4 and by your apps).
Set up a <Realm> element, as described below, in your
$CATALINA_HOME/conf/server.xml file.
Restart Tomcat 4 if it is already running.
Realm Element Attributes
To configure JNDIRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.JDBCRealm" here.
The directory server username used to establish a JNDI connection.
The directory server password used to establish a JNDI connection.
The directory server URL used to establish a JNDI connection.
The fully qualified Java class name of the JNDI context factory to be
used for this connection. By default, the standard JNDI LDAP provider
is used (com.sun.jndi.ldap.LdapCtxFactory).
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
The base element for role searches. If not specified, the top level
element in the directory context will be used.
The name of the directory server attribute containing the role name.
An LDAP search pattern for selecting roles in this Realm, following the
syntax supported by the java.text.MessageFormat class. Use
{0} to substitute in the distinguished name of the user you
want roles for, and/or {1} to substitute in the username of
the user you want roles for.
Set to true if you want role searches to search subtrees
of the element selected by roleBase. The default value of
false causes only the top level element to be searched.
The name of the directory server attribute (in the user element) that
contains the cleartext or digested user password (depending on the setting
of the digest attribute).
An LDAP search pattern for selecting users in this Realm, following the
syntax supported by the java.text.MessageFormat class. Use
{0} to substitute in the distinguished name of the user you
want to select.
Example
Creation of the appropriate schema in your directory server is beyond the
scope of this document, because it is unique to each directory server
implementation. In the examples below, we will assume that you are using a
distribution of the OpenLDAP directory server (version 2.0.11 or later), which
can be downloaded from
http://www.openldap.org. Assume that
your slapd.conf file contains the following settings
(among others):
database ldbm
suffix dc="mycompany",dc="com"
rootdn "cn=Manager,dc=mycompany,dc=com"
rootpw secret
These settings help us identify values for the values to be specified for
connectionName, and connectionPassword, and we
will assume for connectionURL that the directory server runs on
the same machine as Tomcat. See
http://java.sun.com/products/jndi/docs.html
for more information about configuring and using the JNDI LDAP provider.
Next, assume that this directory server has been populated with elements
as shown below (in LDIF format), which define the same users and roles
as the default $CATALINA_HOME/conf/tomcat-users.xml does for
MemoryRealm:
# Define a user named 'tomcat'
dn: cn=tomcat,dc=mycompany,dc=com
cn: tomcat
userPassword: tomcat
sn: Tomcat User
objectClass: person
# Define a user named 'role1'
dn: cn=role1,dc=mycompany,dc=com
cn: role1
userPassword: tomcat
sn: Role1 User
objectClass: person
# Define a user named 'both'
dn: cn=both,dc=mycompany,dc=com
cn: both
userPassword: tomcat
sn: Both User
objectClass: person
# Define an entry to base role searches on
dn: dc=roles,dc=mycompany,dc=com
cn: roles
objectClass: person
sn: Roles Entry
# Define all members of the 'tomcat' role
dn: cn=tomcat,dc=roles,dc=mycompany,dc=com
cn: tomcat
objectClass: groupOfUniqueNames
uniqueMember: cn=tomcat,dc=mycompany,dc=com
uniqueMember: cn=both,dc=mycompany,dc=com
# Define all members of the 'role1' role
dn: cn=role1,dc=roles,dc=mycompany,dc=com
cn: role1
objectClass: groupOfUniqueNames
uniqueMember: cn=role1,dc=mycompany,dc=com
uniqueMember: cn=both,dc=mycompany,dc=com
An example Realm element for the OpenLDAP directory server
configured as described above might look like this:
<Realm className="org.apache.catalina.realm.JNDIRealm" debug="99"
connectionName="cn=Manager,dc=mycompany,dc=com"
connectionPassword="secret"
connectionURL="ldap://localhost:389"
roleBase="dc=roles,dc=mcclan,dc=net"
roleName="cn"
roleSearch="(uniqueMember={0})"
roleSubtree="false"
userPassword="userPassword"
userPattern="cn={0},dc=mycompany,dc=com"
/>
Additional Notes
JNDIRealm operates according to the following rules:
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm. Thus, any changes you have made to the database
directly (new users, changed passwords or roles, etc.) will be immediately
reflected.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser). Any changes to the database information for an
already authenticated user will not be reflected until
the next time that user logs on again.
Administering the information in the directory server
is the responsibility of your own applications. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
Introduction
MemoryRealm is a simple demonstration implementation of the
Tomcat 4 Realm interface. It is not designed for production use.
At startup time, MemoryRealm loads information about all users, and their
corresponding roles, from an XML document (by default, this document is loaded from $CATALINA_HOME/conf/tomcat-users.xml). Changes to the data
in this file are not recognized until Tomcat is restarted.
Realm Element Attributes
To configure MemoryRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.MemoryRealm" here.
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
Absolute or relative (to $CATALINA_HOME) pathname of the XML document
containing our valid usernames, passwords, and roles. See below for more
information on the format of this file. If not specified, the value
conf/tomcat-users.xml is used.
User File Format
The users file (by default, conf/tomcat-users.xml must be an
XML document, with a root element <tomcat-users>. Nested
inside the root element will be a <user> element for each
valid user, consisting of the following attributes:
name - Username this user must log on with.
password - Password this user must log on with (in
clear text if the digest attribute was not set on the
<Realm> element, or digested appropriately as
described here otherwise).
roles - Comma-delimited list of the role names
associated with this user.
Example
The default installation of Tomcat 4 is configured with a MemoryRealm
nested inside the <Engine> element, so that it applies
to all virtual hosts and web applications. The default contents of the
conf/tomcat-users.xml file is:
<tomcat-users>
<user name="tomcat" password="tomcat" roles="tomcat" />
<user name="role1" password="tomcat" roles="role1" />
<user name="both" password="tomcat" roles="tomcat,role1" />
</tomcat-users>
Additional Notes
MemoryRealm operates according to the following rules:
When Tomcat first starts up, it loads all defined users and their
associated information from the users file. Changes to the data in
this file will not be recognized until Tomcat is
restarted.
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser).
Administering the information in the users file is the responsibility
of your application. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
For each of the standard Realm implementations, the user's
password (by default) is stored in clear text. In many environments, this is
undesireable because casual observers of the authentication data can collect
enough information to log on successfully, and impersonate other users.
To avoid this problem, the standard implementations support the concept of
digesting user passwords. This causes the stored version of the
passwords to be encoded (in a form that is not easily reversible), but that
the Realm implementation can still utilize for authentication.
Digested passwords are selected by specifying the digest
attribute on your <Realm> element. The value for this
attribute must be one of the digest algorithms supported by the
java.security.MessageDigest class (SHA, MD2, or MD5). When you
select this option, the contents of the password that is stored in the
Realm must be the cleartext version of the password, as digested
by the specified algorithm.
When the authenticate() method of the Realm is called, the
(cleartext) password specified by the user is itself digested by the same
algorithm, and the result is compared with the value returned by the
Realm. An equal match implies that the cleartext version of the
original password is the same as the one presented by the user, so that this
user should be authorized.
To calculate the digested value of a cleartext password, two convenience
techniques are supported:
If you are writing an application that needs to calculate digested
passowrds dynamically, call the static Digest() method of the
org.apache.catalina.realm.RealmBase class, passing the
cleartext password and the digest algorithm name as arguments. This
method will return the digested password.
If you want to execute a command line utility to calculate the digested
password, simply execute
java org.apache.catalina.realm.RealmBase \
-a {algorithm} {cleartext-password}
and the digested version of this cleartext password will be returned to
standard output.
To use either of the above techniques, the
$CATALINA_HOME/server/lib/catalina.jar file will need to be
on your class path to make the RealmBase class available.
The example application shipped with Tomcat 4 includes an area that is
protected by a security constraint, utilizing form-based login. To access it,
point your browser at
http://localhost:8080/examples/jsp/security/protected/
and log on with one of the usernames and passwords described for the default
MemoryRealm.
If you wish to use the Manager Application
to deploy and undeploy applications in a running Tomcat 4 installation, you
MUST add the "manager" role to at least one username in your selected Realm
implementation. This is because the manager web application itself uses a
security constraint that requires role "manager" to access ANY request URI
within that application.
For security reasons, no username in the default Realm (i.e. using
conf/tomcat-users.xml is assigned the "manager" role. Therfore,
no one will be able to utilize the features of this application until the
Tomcat administrator specifically assigns this role to one or more users.
/images/void.gif) | , Section 12. For a more introductory level
document for web application developers as well as administrators, see
(FIXME - link to backgrounder on container managed security
to be provided).
For information about utilizing the Single Sign On feature of
Tomcat 4 (allowing a user to authenticate themselves once across the entire
set of web applications associated with a virtual host), see
here.
A Realm is a "database" of usernames and passwords that
identify valid users of a web application (or set of web applications), plus
an enumeration of the list of roles associated with each valid user.
You can think of roles as similar to groups in Unix-like operating
systems, because access to specific web application resources is granted to
all users possessing a particular role (rather than enumerating the list of
associated usernames). A particular user can have any number of roles
associated with their username.
Although the Servlet Specification describes a portable mechanism for
applications to declare their security requirements (in the
web.xml deployment descriptor), there is no portable API
defining the interface between a servlet container and the associated user
and role information. In many cases, however, it is desireable to "connect"
a servlet container to some existing authentication database or mechanism
that already exists in the production environment. Therefore, Tomcat 4
defines a Java interface (org.apache.catalina.Realm) that
can be implemented by "plug in" components to establish this connection.
Three standard plug-ins are provided, supporting connection to three different
sources of authentication information:
JDBCRealm - Accesses authentication information
stored in a relational database, accessed via a JDBC driver.
JNDIRealm - Accesses authentication information
stored in an LDAP based directory server, accessed via a JNDI provider.
MemoryRealm - Accesses authentication
information stored in an in-memory object collection, which is initialized
from an XML document (conf/tomcat-users.xml).
It is also possible to write your own Realm implementation,
and integrate it with Tomcat 4. However, doing this is beyond the scope of
this document. See (FIXME - reference to developer stuff)
for more information.
Before getting into the details of the standard Realm implementations, it is
important to understand, in general terms, how a Realm is configured. In
general, you will be adding an XML element to your conf/server.xml
configuration file, that looks something like this:
<Realm className="... class name for this implementation"
... other attributes for this implementation .../>
The <Realm> element can be nested inside one of three
different elements, which has a direct impact on the "scope" of that Realm
(i.e. which web applications will share the same authentication information):
Inside an <Engine> element - This Realm will be shared
across ALL web applications on ALL virtual hosts, UNLESS it is overridden
by a Realm element nested inside a subordinate <Host>
or <Context> element.
Inside a <Host> element - This Realm will be shared across
ALL web applications for THIS virtual host, UNLESS it is overridden
by a Realm element nested inside a subordinate <Context>
element.
Inside a <Context> element - This Realm will be used ONLY
for THIS web application.
Introduction
JDBCRealm is an implementation of the Tomcat 4
Realm interface that looks up users in a relational database
accessed via a JDBC driver. There is substantial configuration flexibility
that lets you adapt to existing table and column names, as long as your
database structure conforms to the following requirements:
There must be a table, referenced below as the users table,
that contains one row for every valid user that this Realm
should recognize.
The users table must contain at least two columns (it may
contain more if your existing applications required it):
Username to be recognized by Tomcat when the user logs in.
Password to be recognized by Tomcat when the user logs in.
This value may in cleartext or digested - see below for more
information.
There must be a table, referenced below as the user roles table,
that contains one row for every valid role that is assigned to a
particular user. It is legal for a user to have zero, one, or more than
one valid role.
The user roles table must contain at least two columns (it may
contain more if your existing applications required it):
Username to be recognized by Tomcat (same value as is specified
in the users table).
Role name of a valid role associated with this user.
Quick Start
To set up Tomcat to use JDBCRealm, you will need to follow these steps:
If you have not yet done so, create tables and columns in your database
that conform to the requirements described above.
Configure a database username and password for use by Tomcat, that has
at least read only access to the tables described above. (Tomcat will
never attempt to write to these tables.)
Place a copy of the JDBC driver you will be using inside the
$CATALINA_HOME/server/lib directory (if you do not need it
visible to web applications) or $CATALINA_HOME/common/lib
(if it will be used both by Tomcat 4 and by your apps).
Note that only JAR files are recognized!
Set up a <Realm> element, as described below, in your
$CATALINA_HOME/conf/server.xml file.
Restart Tomcat 4 if it is already running.
Realm Element Attributes
To configure JDBCRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.JDBCRealm" here.
The database username used to establish a JDBC connection.
The database password used to establish a JDBC connection.
The database URL used to establish a JDBC connection.
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
The fully qualified Java class name of the JDBC driver to be used.
Consult the documentation for your JDBC driver for the appropriate
value.
The name of the column, in the user roles table, that
contains the name of a role assigned to this user.
The name of the column, in the users table, that contains
the password for this user (either in clear text, or digested if the
digest attribute is set).
The name of the column, in the users and user roles
tables, that contains the username of this user.
The name of the table that contains one row for each role
assigned to a particular username. This table must include at
least the columns named by the userNameCol and
roleNameCol attributes.
The name of the table that contains one row for each username
to be recognized by Tomcat. This table must include at least the columns
named by the userNameCol and userCredCol
attributes.
Example
An example SQL script to create the needed tables might look something
like this (adapt the syntax as required for your particular database):
create table users (
user_name varchar(15) not null primary key,
user_pass varchar(15) not null
);
create table user_roles (
user_name varchar(15) not null,
role_name varchar(15) not null,
primary key (user_name, role_name)
);
Example Realm elements are included (commented out) in the
default $CATALINA_HOME/conf/server.xml file. Here's an example
for using a MySQL database called "authority", configured with the tables
described above, and accessed with username "dbuser" and password "dbpass":
<Realm className="org.apache.catalina.realm.JDBCRealm" debug="99"
driverName="org.gjt.mm.mysql.Driver"
connectionURL="jdbc:mysql://localhost/authority?user=dbuser;password=dbpass"
userTable="users" userNameCol="user_name" userCredCol="user_pass"
userRoleTable="user_roles" roleNameCol="role_name"/>
Additional Notes
JDBCRealm operates according to the following rules:
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm. Thus, any changes you have made to the database
directly (new users, changed passwords or roles, etc.) will be immediately
reflected.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser). Any changes to the database information for an
already authenticated user will not be reflected until
the next time that user logs on again.
Administering the information in the users and user roles
table is the responsibility of your own applications. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
Introduction
JNDIRealm is an implementation of the Tomcat 4
Realm interface that looks up users in a directory server
accessed by a JNDI provider (typically, the standard LDAP provider that
is available with the JNDI API classes). There is substantial configuration
flexibility that lets you adapt to the existing schema inside your directory
server, as long as it conforms to the following requirements:
Each user that can be authenticated is represented by an individual
element in the top level DirContext that is accessed
via the connectionURL attribute.
The user element must have the following characteristics:
The distinguished name (dn) attribute of this element
contains the username that is presented for authentication.
There must be an attribute (identified by the userPassword
attribute of our Realm element) that contains the user's
password, either in clear text or digested (see below for more info).
Each group of users that has been assigned a particular role is
represented by an individual element in the top level
DirContext that is accessed via the
connectionURL attribute.
The user group element must have the following characteristics:
The set of all possible groups of interest can be selected by an LDAP
search pattern configured by the roleSearch attribute
of our Realm element.
The roleSearch pattern optionally includes pattern
replacements "{0}" for the distinguished name, and/or "{1} for the
username, of the authenticated user for which roles will be
retrieved.
The roleBase attribute can be set to the element that
is the base of the search for matching roles. If not specified,
the entire directory context will be searched.
The roleSubtree attribute can be set to true
if you wish to search the entire subtree of the directory context.
The default value of false requests a search of only the
current level.
The element includes an attribute (whose name is configured by the
roleName attribute of our Realm element)
containing the name of the role represented by this element.
There must be an administrator username and password that Tomcat can
use to establish a connection to the directory server, with at least
read-only access to the information described above. A future
version of Tomcat will support an option to use the user's username and
password to attempt this connection.
Quick Start
To set up Tomcat to use JNDIRealm, you will need to follow these steps:
Make sure your directory server is configured with a schema that matches
the requirements listed above.
Configure a username and password for use by Tomcat, that has
at least read only access to the information described above. (Tomcat will
never attempt to modify this information.)
Place a copy of the JNDI driver you will be using (typically
ldap.jar available with JNDI) inside the
$CATALINA_HOME/server/lib directory (if you do not need it
visible to web applications) or $CATALINA_HOME/common/lib
(if it will be used both by Tomcat 4 and by your apps).
Set up a <Realm> element, as described below, in your
$CATALINA_HOME/conf/server.xml file.
Restart Tomcat 4 if it is already running.
Realm Element Attributes
To configure JNDIRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.JDBCRealm" here.
The directory server username used to establish a JNDI connection.
The directory server password used to establish a JNDI connection.
The directory server URL used to establish a JNDI connection.
The fully qualified Java class name of the JNDI context factory to be
used for this connection. By default, the standard JNDI LDAP provider
is used (com.sun.jndi.ldap.LdapCtxFactory).
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
The base element for role searches. If not specified, the top level
element in the directory context will be used.
The name of the directory server attribute containing the role name.
An LDAP search pattern for selecting roles in this Realm, following the
syntax supported by the java.text.MessageFormat class. Use
{0} to substitute in the distinguished name of the user you
want roles for, and/or {1} to substitute in the username of
the user you want roles for.
Set to true if you want role searches to search subtrees
of the element selected by roleBase. The default value of
false causes only the top level element to be searched.
The name of the directory server attribute (in the user element) that
contains the cleartext or digested user password (depending on the setting
of the digest attribute).
An LDAP search pattern for selecting users in this Realm, following the
syntax supported by the java.text.MessageFormat class. Use
{0} to substitute in the distinguished name of the user you
want to select.
Example
Creation of the appropriate schema in your directory server is beyond the
scope of this document, because it is unique to each directory server
implementation. In the examples below, we will assume that you are using a
distribution of the OpenLDAP directory server (version 2.0.11 or later), which
can be downloaded from
http://www.openldap.org. Assume that
your slapd.conf file contains the following settings
(among others):
database ldbm
suffix dc="mycompany",dc="com"
rootdn "cn=Manager,dc=mycompany,dc=com"
rootpw secret
These settings help us identify values for the values to be specified for
connectionName, and connectionPassword, and we
will assume for connectionURL that the directory server runs on
the same machine as Tomcat. See
http://java.sun.com/products/jndi/docs.html
for more information about configuring and using the JNDI LDAP provider.
Next, assume that this directory server has been populated with elements
as shown below (in LDIF format), which define the same users and roles
as the default $CATALINA_HOME/conf/tomcat-users.xml does for
MemoryRealm:
# Define a user named 'tomcat'
dn: cn=tomcat,dc=mycompany,dc=com
cn: tomcat
userPassword: tomcat
sn: Tomcat User
objectClass: person
# Define a user named 'role1'
dn: cn=role1,dc=mycompany,dc=com
cn: role1
userPassword: tomcat
sn: Role1 User
objectClass: person
# Define a user named 'both'
dn: cn=both,dc=mycompany,dc=com
cn: both
userPassword: tomcat
sn: Both User
objectClass: person
# Define an entry to base role searches on
dn: dc=roles,dc=mycompany,dc=com
cn: roles
objectClass: person
sn: Roles Entry
# Define all members of the 'tomcat' role
dn: cn=tomcat,dc=roles,dc=mycompany,dc=com
cn: tomcat
objectClass: groupOfUniqueNames
uniqueMember: cn=tomcat,dc=mycompany,dc=com
uniqueMember: cn=both,dc=mycompany,dc=com
# Define all members of the 'role1' role
dn: cn=role1,dc=roles,dc=mycompany,dc=com
cn: role1
objectClass: groupOfUniqueNames
uniqueMember: cn=role1,dc=mycompany,dc=com
uniqueMember: cn=both,dc=mycompany,dc=com
An example Realm element for the OpenLDAP directory server
configured as described above might look like this:
<Realm className="org.apache.catalina.realm.JNDIRealm" debug="99"
connectionName="cn=Manager,dc=mycompany,dc=com"
connectionPassword="secret"
connectionURL="ldap://localhost:389"
roleBase="dc=roles,dc=mcclan,dc=net"
roleName="cn"
roleSearch="(uniqueMember={0})"
roleSubtree="false"
userPassword="userPassword"
userPattern="cn={0},dc=mycompany,dc=com"
/>
Additional Notes
JNDIRealm operates according to the following rules:
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm. Thus, any changes you have made to the database
directly (new users, changed passwords or roles, etc.) will be immediately
reflected.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser). Any changes to the database information for an
already authenticated user will not be reflected until
the next time that user logs on again.
Administering the information in the directory server
is the responsibility of your own applications. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
Introduction
MemoryRealm is a simple demonstration implementation of the
Tomcat 4 Realm interface. It is not designed for production use.
At startup time, MemoryRealm loads information about all users, and their
corresponding roles, from an XML document (by default, this document is loaded from $CATALINA_HOME/conf/tomcat-users.xml). Changes to the data
in this file are not recognized until Tomcat is restarted.
Realm Element Attributes
To configure MemoryRealm, you will create a <Realm>
element and nest it in your $CATALINA_HOME/conf/server.xml file,
as described above. The following
attributes are supported by this implementation:
The fully qualified Java class name of this Realm implementation.
You MUST specify the value
"org.apache.catalina.realm.MemoryRealm" here.
The level of debugging detail logged by this Realm
to the associated Logger. Higher numbers
generate more detailed output. If not specified, the default
debugging detail level is zero (0).
The digest algorithm used to store passwords in non-plaintext formats.
Valid values are those accepted for the algorithm name by the
java.security.MessageDigest class. See
Digested Passwords for more
information. If not specified, passwords are stored in clear text.
Absolute or relative (to $CATALINA_HOME) pathname of the XML document
containing our valid usernames, passwords, and roles. See below for more
information on the format of this file. If not specified, the value
conf/tomcat-users.xml is used.
User File Format
The users file (by default, conf/tomcat-users.xml must be an
XML document, with a root element <tomcat-users>. Nested
inside the root element will be a <user> element for each
valid user, consisting of the following attributes:
name - Username this user must log on with.
password - Password this user must log on with (in
clear text if the digest attribute was not set on the
<Realm> element, or digested appropriately as
described here otherwise).
roles - Comma-delimited list of the role names
associated with this user.
Example
The default installation of Tomcat 4 is configured with a MemoryRealm
nested inside the <Engine> element, so that it applies
to all virtual hosts and web applications. The default contents of the
conf/tomcat-users.xml file is:
<tomcat-users>
<user name="tomcat" password="tomcat" roles="tomcat" />
<user name="role1" password="tomcat" roles="role1" />
<user name="both" password="tomcat" roles="tomcat,role1" />
</tomcat-users>
Additional Notes
MemoryRealm operates according to the following rules:
When Tomcat first starts up, it loads all defined users and their
associated information from the users file. Changes to the data in
this file will not be recognized until Tomcat is
restarted.
When a user attempts to access a protected resource for the first time,
Tomcat 4 will call the authenticate() method of this
Realm.
Once a user has been authenticated, the user (and his or her associated
roles) are cached within Tomcat for the duration of the user's login.
(For FORM-based authentication, that means until the session times out or
is invalidated; for BASIC authentication, that means until the user
closes their browser).
Administering the information in the users file is the responsibility
of your application. Tomcat does not
provide any built-in capabilities to maintain users and roles.
Debugging and exception messages logged by this Realm will
be recorded by the Logger that is associated with our
surrounding Context, Host, or
Engine. By default, the corresponding Logger will create a
log file in the $CATALINA_HOME/logs directory.
For each of the standard Realm implementations, the user's
password (by default) is stored in clear text. In many environments, this is
undesireable because casual observers of the authentication data can collect
enough information to log on successfully, and impersonate other users.
To avoid this problem, the standard implementations support the concept of
digesting user passwords. This causes the stored version of the
passwords to be encoded (in a form that is not easily reversible), but that
the Realm implementation can still utilize for authentication.
Digested passwords are selected by specifying the digest
attribute on your <Realm> element. The value for this
attribute must be one of the digest algorithms supported by the
java.security.MessageDigest class (SHA, MD2, or MD5). When you
select this option, the contents of the password that is stored in the
Realm must be the cleartext version of the password, as digested
by the specified algorithm.
When the authenticate() method of the Realm is called, the
(cleartext) password specified by the user is itself digested by the same
algorithm, and the result is compared with the value returned by the
Realm. An equal match implies that the cleartext version of the
original password is the same as the one presented by the user, so that this
user should be authorized.
To calculate the digested value of a cleartext password, two convenience
techniques are supported:
If you are writing an application that needs to calculate digested
passowrds dynamically, call the static Digest() method of the
org.apache.catalina.realm.RealmBase class, passing the
cleartext password and the digest algorithm name as arguments. This
method will return the digested password.
If you want to execute a command line utility to calculate the digested
password, simply execute
java org.apache.catalina.realm.RealmBase \
-a {algorithm} {cleartext-password}
and the digested version of this cleartext password will be returned to
standard output.
To use either of the above techniques, the
$CATALINA_HOME/server/lib/catalina.jar file will need to be
on your class path to make the RealmBase class available.
The example application shipped with Tomcat 4 includes an area that is
protected by a security constraint, utilizing form-based login. To access it,
point your browser at
http://localhost:8080/examples/jsp/security/protected/
and log on with one of the usernames and passwords described for the default
MemoryRealm.
If you wish to use the Manager Application
to deploy and undeploy applications in a running Tomcat 4 installation, you
MUST add the "manager" role to at least one username in your selected Realm
implementation. This is because the manager web application itself uses a
security constraint that requires role "manager" to access ANY request URI
within that application.
For security reasons, no username in the default Realm (i.e. using
conf/tomcat-users.xml is assigned the "manager" role. Therfore,
no one will be able to utilize the features of this application until the
Tomcat administrator specifically assigns this role to one or more users.
/images/void.gif) |
The characteristics of each of these class loaders, including the source
of classes and resources that they make visible, are discussed in detail in
the following section.
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Class Loader Definitions |
As indicated in the diagram above, Tomcat 4 creates the following class
loaders as it is initialized:
- Bootstrap - This class loader contains the basic runtime
classes provided by the Java Virtual Machine, plus any classes from JAR
files present in the System Extensions directory
(
$JAVA_HOME/jre/lib/ext ). NOTE - Some JVMs may
implement this as more than one class loader, or it may not be visible
(as a class loader) at all.
- System - This class loader is normally initialized from
the contents of the
CLASSPATH environment variable. All such
classes are visible to both Tomcat internal classes, and to web
applications. However, the standard Tomcat 4 startup scripts
($CATALINA_HOME/bin/catalina.sh or
%CATALINA_HOME%\bin\catalina.bat ) totally ignore the contents
of the CLASSPATH environment variable itself, and instead
build the System class loader from the following repositories:
- $CATALINA_HOME/bin/bootstrap.jar - Contains the main()
method that is used to initialize the Tomcat 4 server, and
the class loader implementation classes it depends on.
- $JAVA_HOME/lib/tools.jar - Contains the "javac"
compiler used to convert JSP pages into servlet classes.
- Common - This class loader contains additional classes
that are made visible to both Tomcat internal classes and to all web
applications. Normally, application classes should NOT
be placed here. All unpacked classes and resources in
$CATALINA_HOME/common/classes , as well as classes and
resources in JAR files under
$CATALINA_HOME/common/lib , are made visible through this
class loader. By default, that includes the following:
- activation.jar - The Java activation framework.
- jdbc2_0-stdext.jar - JDBC 2.0 standard extension
(included as a standard part of JDBC 3.0).
- jndi.jar - The Java Naming and Directory Interface API
classes (loaded ONLY on a JDK 1.2 system, because
they are included automatically on JDK 1.3 and later).
- jta-spec.jar - The Java Transaction API interfaces.
- mail.jar - Java Mail.
- naming-common.jar - The JNDI implementation used
by Tomcat 4 to represent the default JNDI naming context provided
to web applications.
- naming-resources.jar - JNDI Directory Context
implementations which are used to abstract access to the static
resources of a web application.
- servlet.jar - The Servlet and JSP API classes.
- tyrex-0.9.7.jar - JTA/JTS/OTS compliant transaction
manager and DataSource connection pool implementation.
- xerces.jar - The Xerces 1.x XML parser (also includes the
JAXP 1.1 interfaces).
- Catalina - This class loader is initialized to include
all classes and resources required to implement Tomcat 4 itself. These
classes and resources are TOTALLY invisible to web
applications. All unpacked classes and resources in
$CATALINA_HOME/server/classes , as well as classes and
resources in JAR files under
$CATALINA_HOME/server/lib , are made visible through
this class loader. By default, that includes the following:
- catalina.jar - Implementation of the Catalina servlet
container portion of Tomcat 4.
- jakarta-regexp-X.Y.jar - The binary distribution of the
Jakarta Regexp
regular expression processing library, used in the implementation of
request filters.
- servlets-xxxx.jar - The standard suite of servlets
which provide basic services, like static page serving, WebDAV support,
CGI, SSI, and more.
- tomcat-util.jar - Utility components used by modules from
the jakarta-tomcat-connectors subproject.
- tomcat-ajp.jar - The Java portion of the AJP 1.x connector
(also know as the JK connector), which provides support for
connecting native webservers, and load balancing between multiple
Tomcat instances.
- warp.jar - Classes for the Java portion of the
mod_webapp web server connector, which allows Tomcat to
run behind web servers such as Apache and iPlanet iAS and iWS.
- Shared - This class loader is the place to put classes
and resources that you wish to share across ALL
web applications (unless Tomcat internal classes also need access, which
is an unusual case). All unpacked classes and resources in
$CATALINA_HOME/classes , as well as classes and resources
in JAR files under $CATALINA_HOME/lib , are made visible
through this class loader. By default, that includes the following:
- jasper-compiler.jar - The Jasper JSP page compiler.
- jasper-runtime.jar - The runtime support classes required
to execute JSP pages that have already been translated into Java
servlets and then compiled.
- naming-factory.jar - JNDI object factories for resources
supported by the default JNDI naming context provided to web
applications.
- WebappX - A class loader is created for each web
application that is deployed in a single Tomcat 4 instance. All unpacked
classes and resources in the
/WEB-INF/classes directory of
your web application archive, plus classes and resources in JAR files
under the /WEB-INF/lib directory of your web application
archive, are made visible to the containing web application, but to
no others.
As mentioned above, the web application class loader diverges from the
default Java 2 delegation model (in accordance with the recommendations in the
Servlet Specification, version 2.3, section 9.6). When a request to load a
class from the web application's WebappX class loader is processed,
this class loader will look in the local repositories first,
instead of delegating before looking. All other class loaders in Tomcat 4
follow the usual delegation pattern.
Therefore, from the perspective of a web application, class or resource
loading looks in the following repositories, in this order:
- /WEB-INF/classes of your web application
- /WEB-INF/lib/*.jar of your web application
- Bootstrap classes of your JVM
- System class loader classses (described above)
- $CATALINA_HOME/common/classes
- $CATALINA_HOME/common/lib/*.jar
- $CATALINA_HOME/classes
- $CATALINA_HOME/lib/*.jar
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