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title	In progress...

Work in progress...

This page documents how to write a CAS3 AuthenticationHandler. If you already have a CAS2 PasswordHandler or TrustHandler, you can just use it in CAS3 without writing any new code and there is documentation intended specifically for explaining how to convert a CAS2 PasswordHandler to the CAS3 APIs. This page is intended to document CAS3 AuthenticationHandler implementation outside the context of CAS2.

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Before we discuss actual APIs and code, it may be helpful to review the concepts of CAS authentication.

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Credentials

Credentials are what someone presents to CAS as evidence on the basis of which they may be authenticated. A username, password pair is a Credentials, as is a cryptographic certificate, etc.

Principal

A Principal is an entity that is authenticated.

Core interfaces

The core interface to implement for your authentication-handling plugin is AuthenticationHandler.

Code Block

title	AuthenticationHandler

/**
 * Validate Credentials support for AuthenticationManagerImpl.
 * 
 * Determines that Credentials are valid. Password-based credentials may be
 * tested against an external LDAP, Kerberos, JDBC source. Certificates may be
 * checked against a list of CA's and do the usual chain validation.
 * Implementations must be parameterized with their sources of information.
 * 
 * Callers to this class should first call supports to determine if the
 * AuthenticationHandler can authenticate the credentials provided.
 *
 * @version $Revision: 1.11 $ $Date: 2005/06/17 13:24:38 $
 */
public interface AuthenticationHandler {

    /**
     * Method to determine if the credentials supplied are valid.
     * 
     * @param credentials The credentials to validate.
     * @return true if valid, return false otherwise.
     * @throws AuthenticationException An AuthenticationException can contain
     * details about why a particular authentication request failed.
     */
    boolean authenticate(Credentials credentials)
        throws AuthenticationException;

    /**
     * Method to check if the handler knows how to handle the credentials
     * provided. It may be a simple check of the Credentials class or something
     * more complicated such as scanning the information contained in the
     * Credentials object.
     * 
     * @param credentials The credentials to check.
     * @return true if the handler supports the Credentials, false othewrise.
     */
    boolean supports(Credentials credentials);
}

You can code directly to this interface, or you can extend AbstractUsernamePasswordAuthenticationHandler if you're dealing with usernames and passwords.

Code Block

title	AbstractUsernamePasswordAuthenticationHandler


/**
 * Abstract class to override supports so that we don't need to duplicate the
 * check for UsernamePasswordCredentials.
 * 
 * @version $Revision: 1.12 $ $Date: 2005/06/20 18:15:36 $
 */
public abstract class AbstractUsernamePasswordAuthenticationHandler implements
    AuthenticationHandler, InitializingBean {

    /**
     * PasswordEncoder to be used by subclasses to encode passwords for
     * comparing against a resource.
     */
    private PasswordEncoder passwordEncoder;

    /** Instance of logging for subclasses. */
    private Log log = LogFactory.getLog(this.getClass());

    /**
     * Method automatically handles conversion to UsernamePasswordCredentials
     * and delegates to abstract authenticateUsernamePasswordInternal so
     * subclasses do not need to cast.
     */
    public final boolean authenticate(final Credentials credentials)
        throws AuthenticationException {
        return authenticateUsernamePasswordInternal((UsernamePasswordCredentials) credentials);
    }

    /**
     * Abstract convenience method that assumes the credentials passed in are a
     * subclass of UsernamePasswordCredentials.
     * 
     * @param credentials the credentials representing the Username and Password
     * presented to CAS
     * @return true if the credentials are authentic, false otherwise.
     * @throws AuthenticationException if authenticity cannot be determined.
     */
    protected abstract boolean authenticateUsernamePasswordInternal(
        final UsernamePasswordCredentials credentials)
        throws AuthenticationException;

    public final void afterPropertiesSet() throws Exception {
        if (this.passwordEncoder == null) {
            this.passwordEncoder = new PlainTextPasswordEncoder();
            getLog().info(
                "No PasswordEncoder set.  Using default: "
                    + this.passwordEncoder.getClass().getName());
        }
        afterPropertiesSetInternal();
    }

    /**
     * Method designed to be overwritten subclasses that need to do additional
     * properties checking.
     * 
     * @throws Exception if there is an error checking the properties.
     */
    protected void afterPropertiesSetInternal() throws Exception {
        // this is designed to be overwritten
    }

    /**
     * Method to return the PasswordEncoder to be used to encode passwords.
     * 
     * @return the PasswordEncoder associated with this class.
     */
    public final PasswordEncoder getPasswordEncoder() {
        return this.passwordEncoder;
    }

    /**
     * Method to return the log instance in order for subclasses to have access
     * to the log object.
     * 
     * @return the logging instance for this class.
     */
    public final Log getLog() {
        return this.log;
    }

    /**
     * Sets the PasswordEncoder to be used with this class.
     * 
     * @param passwordEncoder the PasswordEncoder to use when encoding
     * passwords.
     */
    public final void setPasswordEncoder(final PasswordEncoder passwordEncoder) {
        this.passwordEncoder = passwordEncoder;
    }

    /**
     * @return true if the credentials are not null and the credentials class is
     * assignable from UsernamePasswordCredentials.
     */
    public final boolean supports(final Credentials credentials) {
        return credentials != null
            && UsernamePasswordCredentials.class.isAssignableFrom(credentials
                .getClass());
    }
}

Versions Compared

Old Version 6

New Version 7

Key

Credentials

Principal

Core interfaces