| A Configuration object is responsible for specifying which LoginModules
should be used for a particular application, and in what order the
LoginModules should be invoked.
A login configuration contains the following information.
Note that this example only represents the default syntax for the
Configuration. Subclass implementations of this class
may implement alternative syntaxes and may retrieve the
Configuration from any source such as files, databases,
or servers.
Name {
ModuleClass Flag ModuleOptions;
ModuleClass Flag ModuleOptions;
ModuleClass Flag ModuleOptions;
};
Name {
ModuleClass Flag ModuleOptions;
ModuleClass Flag ModuleOptions;
};
other {
ModuleClass Flag ModuleOptions;
ModuleClass Flag ModuleOptions;
};
Each entry in the Configuration is indexed via an
application name, Name, and contains a list of
LoginModules configured for that application. Each LoginModule
is specified via its fully qualified class name.
Authentication proceeds down the module list in the exact order specified.
If an application does not have specific entry,
it defaults to the specific entry for "other".
The Flag value controls the overall behavior as authentication
proceeds down the stack. The following represents a description of the
valid values for Flag and their respective semantics:
1) Required - The LoginModule is required to succeed.
If it succeeds or fails, authentication still continues
to proceed down the LoginModule list.
2) Requisite - The LoginModule is required to succeed.
If it succeeds, authentication continues down the
LoginModule list. If it fails,
control immediately returns to the application
(authentication does not proceed down the
LoginModule list).
3) Sufficient - The LoginModule is not required to
succeed. If it does succeed, control immediately
returns to the application (authentication does not
proceed down the LoginModule list).
If it fails, authentication continues down the
LoginModule list.
4) Optional - The LoginModule is not required to
succeed. If it succeeds or fails,
authentication still continues to proceed down the
LoginModule list.
The overall authentication succeeds only if all Required and
Requisite LoginModules succeed. If a Sufficient
LoginModule is configured and succeeds,
then only the Required and Requisite LoginModules prior to
that Sufficient LoginModule need to have succeeded for
the overall authentication to succeed. If no Required or
Requisite LoginModules are configured for an application,
then at least one Sufficient or Optional
LoginModule must succeed.
ModuleOptions is a space separated list of
LoginModule-specific values which are passed directly to
the underlying LoginModules. Options are defined by the
LoginModule itself, and control the behavior within it.
For example, a LoginModule may define options to support
debugging/testing capabilities. The correct way to specify options in the
Configuration is by using the following key-value pairing:
debug="true". The key and value should be separated by an
'equals' symbol, and the value should be surrounded by double quotes.
If a String in the form, ${system.property}, occurs in the value,
it will be expanded to the value of the system property.
Note that there is no limit to the number of
options a LoginModule may define.
The following represents an example Configuration entry
based on the syntax above:
Login {
com.sun.security.auth.module.UnixLoginModule required;
com.sun.security.auth.module.Krb5LoginModule optional
useTicketCache="true"
ticketCache="${user.home}${/}tickets";
};
This Configuration specifies that an application named,
"Login", requires users to first authenticate to the
com.sun.security.auth.module.UnixLoginModule, which is
required to succeed. Even if the UnixLoginModule
authentication fails, the
com.sun.security.auth.module.Krb5LoginModule
still gets invoked. This helps hide the source of failure.
Since the Krb5LoginModule is Optional, the overall
authentication succeeds only if the UnixLoginModule
(Required) succeeds.
Also note that the LoginModule-specific options,
useTicketCache="true" and
ticketCache=${user.home}${/}tickets",
are passed to the Krb5LoginModule.
These options instruct the Krb5LoginModule to
use the ticket cache at the specified location.
The system properties, user.home and /
(file.separator), are expanded to their respective values.
There is only one Configuration object installed in the runtime at any
given time. A Configuration object can be installed by calling the
setConfiguration method. The installed Configuration object
can be obtained by calling the getConfiguration method.
If no Configuration object has been installed in the runtime, a call to
getConfiguration installs an instance of the default
Configuration implementation (a default subclass implementation of this
abstract class).
The default Configuration implementation can be changed by setting the value
of the "login.configuration.provider" security property (in the Java
security properties file) to the fully qualified name of the desired
Configuration subclass implementation. The Java security properties file
is located in the file named <JAVA_HOME>/lib/security/java.security.
<JAVA_HOME> refers to the value of the java.home system property,
and specifies the directory where the JRE is installed.
Application code can directly subclass Configuration to provide a custom
implementation. In addition, an instance of a Configuration object can be
constructed by invoking one of the getInstance factory methods
with a standard type. The default policy type is "JavaLoginConfig".
See Appendix A in the
Java Cryptography Architecture API Specification & Reference
for a list of standard Configuration types. | 