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This package presents a framework that allows application developers to
make use of security services like authentication, data integrity and
data confidentiality from a variety of underlying security mechanisms
like Kerberos, using a unified API. The security mechanisms that an
application can
chose to use are identified with unique object identifiers. One example
of such a mechanism is the Kerberos v5 GSS-API mechanism (object
identifier 1.2.840.113554.1.2.2). This mechanism is available through
the default instance of the GSSManager class.<p>
The GSS-API is defined in a language independent way in
language bindings are defined in
An application starts out by instantiating a <code>GSSManager</code>
which then serves as a factory for a security context. An application
can use specific principal names and credentials that are also created
using the GSSManager; or it can instantiate a
context with system defaults. It then goes through a context
establishment loop. Once a context is established with the
peer, authentication is complete. Data protection such as integrity
and confidentiality can then be obtained from this context.<p>
The GSS-API does not perform any communication with the peer. It merely
produces tokens that the application must somehow transport to the
other end.<p>
<h3>Credential Acquisition</h3>
<a name=useSubjectCredsOnly>
The GSS-API itself does not dictate how an underlying mechanism
obtains the credentials that are needed for authentication. It is
assumed that prior to calling the GSS-API, these credentials are
obtained and stored in a location that the mechanism provider is
aware of. However, the default model in the Java platform will be
that mechanism providers must obtain credentials only from the private
or public credential sets associated with the
current access control context. The Kerberos v5
mechanism will search for the required INITIATE and ACCEPT credentials
the private credential set where as some other mechanism might look
in the public set or in both. If the desired credential is not
present in the appropriate sets of the current Subject, the GSS-API
call must fail.<p>
This model has the advantage that credential management
is simple and predictable from the applications point of view. An
application, given the right permissions, can purge the credentials in
the Subject or renew them using standard Java API's. If it purged
the credentials, it would be sure that the JGSS mechanism would fail,
or if it renewed a time based credential it would be sure that a JGSS
mechanism would succeed.<p>
This model does require that a {@link
javax.security.auth.login JAAS login} be performed in order to
authenticate and populate a Subject that the JGSS mechnanism can later
utilize. However, applications have the ability to relax this
restiction by means of a system property:
this system property will be assumed to be <code>true</code> (even when
it is unset) indicating that providers must only use the credentials
that are present in the current Subject. However, if this property is
explicitly set to false by the application, then it indicates that
the provider is free to use any credentials cache of its choice. Such
a credential cache might be a disk cache, an in-memory cache, or even
just the current Subject itself.
</a>
<h2>Related Documentation</h2>
<p>
For an online tutorial on using Java GSS-API, please see
<a href="/technotes/guides/security/jgss/tutorials/index.html">Introduction to JAAS and Java GSS-API</a>.
</p>
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@since 1.4
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