/*
 *  Authenticator.java
 *
 *  $Revision$ $Date$ 
 * 
 *  (c) Copyright 2001, 2002 Motorola, Inc.  ALL RIGHTS RESERVED.
 */
package javax.obex;

import java.lang.*;
/**
 * This interface provides a way to respond to authentication challenge and
 * authentication response headers.  When a client or server receives an
 * authentication challenge or authentication response header, the
 * <code>onAuthenticationChallenge()</code> or
 * <code>onAuthenticationResponse()</code> will be called, respectively, by
 * the implementation.
 * <P>
 * For more information on how the authentication procedure works in OBEX,
 * please review the IrOBEX specification at
 * <A HREF="http://www.irda.org">http://www.irda.org</A>.
 * <P>
 * <STRONG>Authentication Challenges</STRONG>
 * <P>
 * When a client or server receives an authentication challenge header, the
 * <code>onAuthenticationChallenge()</code> method will be invoked by the
 * OBEX API implementation.  The application will then return the user name
 * (if needed) and password via a <code>PasswordAuthentication</code> object.
 * The password in this object is not sent in the authentication response.
 * Instead, the 16-byte challenge received in the authentication challenge is
 * combined with the password returned from the
 * <code>onAuthenticationChallenge()</code> method and passed through the MD5
 * hash algorithm.  The resulting value is sent in the authentication response
 * along with the user name if it was provided.
 * <P>
 * <STRONG>Authentication Responses</STRONG>
 * <P>
 * When a client or server receives an authentication response header, the
 * <code>onAuthenticationResponse()</code> method is invoked by the API
 * implementation with the user name received in the authentication response
 * header.  (The user name will be <code>null</code> if no user name was
 * provided in the authentication response header.)  The application must
 * determine the correct password.  This value should be returned from the
 * <code>onAuthenticationResponse()</code> method.  If the authentication
 * request should fail without the implementation checking the password,
 * <code>null</code> should
 * be returned by the application.  (This is needed for reasons like not
 * recognizing the user name, etc.)  If the returned value is not
 * <code>null</code>, the OBEX API implementation will combine the password
 * returned from the <code>onAuthenticationResponse()</code> method and
 * challenge sent via the authentication challenge, apply the MD5 hash
 * algorithm, and compare the result to the response hash received in the
 * authentication response header.  If the values are not equal, an
 * <code>IOException</code> will be thrown if the client requested authentication.
 * If the server requested authentication, the
 * <code>onAuthenticationFailure()</code> method will be called on the
 * <code>ServerRequestHandler</code> that failed authentication.  The
 * connection is <B>not</B> closed if authentication failed.
 *
 * @version 1.0 February 11, 2002
 */
public interface Authenticator {

    /**
     * Called when a client or a server receives an authentication challenge
     * header. It should respond to the challenge with a
     * <code>PasswordAuthentication</code> that contains the correct user name
     * and password for the challenge.
     *
     * @param description the description of which user name and password
     * should be used; if no description is provided in the authentication
     * challenge or the description is encoded in an encoding scheme that is
     * not supported, an empty string will be provided
     *
     * @param isUserIdRequired <code>true</code> if the user ID is required;
     * <code>false</code> if the user ID is not required
     *
     * @param isFullAccess <code>true</code> if full access to the server
     * will be granted; <code>false</code> if read only access will be
     * granted
     *
     * @return a <code>PasswordAuthentication</code> object containing the
     * user name and password used for authentication
     */
    public PasswordAuthentication onAuthenticationChallenge(String description,
        boolean isUserIdRequired, boolean isFullAccess);

    /**
     * Called when a client or server receives an authentication response
     * header.  This method will provide the user name and expect the correct
     * password to be returned.
     *
     * @param userName the user name provided in the authentication response;
     * may be <code>null</code>
     *
     * @return the correct password for the user name provided; if
     * <code>null</code> is returned then the authentication request failed
     */
    public byte[] onAuthenticationResponse(byte[] userName);
}