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/* SaslServer.java

   Copyright (C) 2003, 2005, Free Software Foundation, Inc.

This file is part of GNU Classpath.

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it under the terms of the GNU General Public License as published by

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permission to link this library with independent modules to produce an

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package javax.security.sasl;

/**

 * <p>Performs SASL authentication as a server.</p>

 *

 * <p>A server such as an LDAP server gets an instance of this class in order to

 * perform authentication defined by a specific SASL mechanism. Invoking methods

 * on the <code>SaslServer</code> instance generates challenges corresponding to

 * the SASL mechanism implemented by the <code>SaslServer</code> instance. As

 * the authentication proceeds, the instance encapsulates the state of a SASL

 * server's authentication exchange.</p>

 *

 * <p>Here's an example of how an LDAP server might use a <code>SaslServer</code>

 * instance. It first gets an instance of a <code>SaslServer</code> for the SASL

 * mechanism requested by the client:</p>

 *

 * <pre>

 *SaslServer ss =

 *      Sasl.createSaslServer(mechanism, "ldap", myFQDN, props, callbackHandler);

 * </pre>

 *

 * <p>It can then proceed to use the server for authentication. For example,

 * suppose the LDAP server received an LDAP BIND request containing the name of

 * the SASL mechanism and an (optional) initial response. It then might use the

 * server as follows:</p>

 *

 * <pre>

 *while (!ss.isComplete()) {

 *   try {

 *      byte[] challenge = ss.evaluateResponse(response);

 *      if (ss.isComplete()) {

 *         status = ldap.sendBindResponse(mechanism, challenge, SUCCESS);

 *      } else {

 *         status = ldap.sendBindResponse(mechanism, challenge, SASL_BIND_IN_PROGRESS);

 *         response = ldap.readBindRequest();

 *      }

 *   } catch (SaslException x) {

 *      status = ldap.sendErrorResponse(x);

 *      break;

 *   }

 *}

 *if (ss.isComplete() && (status == SUCCESS)) {

 *   String qop = (String) sc.getNegotiatedProperty(Sasl.QOP);

 *   if (qop != null

 *         && (qop.equalsIgnoreCase("auth-int")

 *            || qop.equalsIgnoreCase("auth-conf"))) {

 *      // Use SaslServer.wrap() and SaslServer.unwrap() for future

 *      // communication with client

 *      ldap.in = new SecureInputStream(ss, ldap.in);

 *      ldap.out = new SecureOutputStream(ss, ldap.out);

 *   }

 *}

 * </pre>

 *

 * @see Sasl

 * @see SaslServerFactory

 *

 * @since 1.5

 */

public interface SaslServer

{

  /**

   * Returns the IANA-registered mechanism name of this SASL server (e.g.

   * "CRAM-MD5", "GSSAPI").

   *

   * @return a non-null string representing the IANA-registered mechanism name.

   */

  String getMechanismName();

  /**

   * Evaluates the response data and generates a challenge. If a response is

   * received from the client during the authentication process, this method is

   * called to prepare an appropriate next challenge to submit to the client.

   * The challenge is <code>null</code> if the authentication has succeeded and

   * no more challenge data is to be sent to the client. It is non-null if the

   * authentication must be continued by sending a challenge to the client, or

   * if the authentication has succeeded but challenge data needs to be

   * processed by the client. {@link #isComplete()} should be called after each

   * call to <code>evaluateResponse()</code>,to determine if any further

   * response is needed from the client.

   *

   * @param response the non-null (but possibly empty) response sent by the

   * client.

   * @return the possibly <code>null</code> challenge to send to the client.

   * It is <code>null</code> if the authentication has succeeded and there is

   * no more challenge data to be sent to the client.

   * @throws SaslException if an error occurred while processing the response

   * or generating a challenge.

   */

  byte[] evaluateResponse(byte[] response) throws SaslException;

  /**

   * Determines if the authentication exchange has completed. This method is

   * typically called after each invocation of {@link #evaluateResponse(byte[])}

   * to determine whether the authentication has completed successfully or

   * should be continued.

   *

   * @return <code>true</code> if the authentication exchange has completed;

   * <code>false</code> otherwise.

   */

  boolean isComplete();

  /**

   * Reports the authorization ID in effect for the client of this session This

   * method can only be called if {@link #isComplete()} returns <code>true</code>.

   *

   * @return the authorization ID of the client.

   * @throws IllegalStateException if this authentication session has not

   * completed.

   */

  String getAuthorizationID();

  /**

   * <p>Unwraps a byte array received from the client. This method can be called

   * only after the authentication exchange has completed (i.e., when

   * {@link #isComplete()} returns <code>true</code>) and only if the

   * authentication exchange has negotiated integrity and/or privacy as the

   * quality of protection; otherwise, an {@link IllegalStateException} is

   * thrown.</p>

   *

   * <p><code>incoming</code> is the contents of the SASL buffer as defined in

   * RFC 2222 without the leading four octet field that represents the length.

   * <code>offset</code> and <code>len</code> specify the portion of incoming

   * to use.</p>

   *

   * @param incoming a non-null byte array containing the encoded bytes from

   * the client.

   * @param offset the starting position at <code>incoming</code> of the bytes

   * to use.

   * @param len the number of bytes from <code>incoming</code> to use.

   * @return a non-null byte array containing the decoded bytes.

   * @throws SaslException if <code>incoming</code> cannot be successfully

   * unwrapped.

   * @throws IllegalStateException if the authentication exchange has not

   * completed, or if the negotiated quality of protection has neither

   * integrity nor privacy.

   */

  byte[] unwrap(byte[] incoming, int offset, int len) throws SaslException;

  /**

   * <p>Wraps a byte array to be sent to the client. This method can be called

   * only after the authentication exchange has completed (i.e., when

   * {@link #isComplete()} returns <code>true</code>) and only if the

   * authentication exchange has negotiated integrity and/or privacy as the

   * quality of protection; otherwise, an {@link IllegalStateException} is

   * thrown.</p>

   *

   * <p>The result of this method will make up the contents of the SASL buffer

   * as defined in RFC 2222 without the leading four octet field that

   * represents the length. <code>offset</code> and <code>len</code> specify

   * the portion of <code>outgoing</code> to use.

   *

   * @param outgoing a non-null byte array containing the bytes to encode.

   * @param offset the starting position at <code>outgoing</code> of the bytes

   * to use.

   * @param len the number of bytes from <code>outgoing</code> to use.

   * @return a non-null byte array containing the encoded bytes.

   * @throws SaslException if <code>outgoing</code> cannot be successfully

   * wrapped.

   * @throws IllegalStateException if the authentication exchange has not

   * completed, or if the negotiated quality of protection has neither

   * integrity nor privacy.

   */

  byte[] wrap(byte[] outgoing, int offset, int len) throws SaslException;

  /**

   * Retrieves the negotiated property. This method can be called only after

   * the authentication exchange has completed (i.e., when

   * {@link #isComplete()} returns <code>true</code>); otherwise, an

   * {@link IllegalStateException} is thrown.

   *

   * @return the value of the negotiated property. If <code>null</code>, the

   * property was not negotiated or is not applicable to this mechanism.

   * @throws IllegalStateException if this authentication exchange has not

   * completed.

   */

  Object getNegotiatedProperty(String propName);

  /**

   * Disposes of any system resources or security-sensitive information the

   * <code>SaslServer</code> might be using. Invoking this method invalidates

   * the <code>SaslServer</code> instance. This method is idempotent.

   *

   * @throws SaslException if a problem was encountered while disposing of the

   * resources.

   */

  void dispose() throws SaslException;

}