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package javax.security.sasl;

/**

 * Performs SASL authentication as a server.

 *<p>

 * A server such 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} instance

 * generates challenges according to the SASL

 * mechanism implemented by the {@code SaslServer}.

 * As the authentication proceeds, the instance

 * encapsulates the state of a SASL server's authentication exchange.

 *<p>

 * Here's an example of how an LDAP server might use a {@code SaslServer}.

 * It first gets an instance of a {@code SaslServer} for the SASL mechanism

 * requested by the client:

 *<blockquote><pre>

 * SaslServer ss = Sasl.createSaslServer(mechanism,

 *     "ldap", myFQDN, props, callbackHandler);

 *</pre></blockquote>

 * 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:

 *<blockquote><pre>{@code

 * 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 e) {

 *          status = ldap.sendErrorResponse(e);

 *          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></blockquote>

 *

 * @since 1.5

 *

 * @see Sasl

 * @see SaslServerFactory

 *

 * @author Rosanna Lee

 * @author Rob Weltman

 */

public abstract 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.

     */

    public abstract 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 null 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.

     * {@code isComplete()} should be called

     * after each call to {@code evaluateResponse()},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 null challenge to send to the client.

     * It is null if the authentication has succeeded and there is

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

     * @exception SaslException If an error occurred while processing

     * the response or generating a challenge.

     */

    public abstract byte[] evaluateResponse(byte[] response)

        throws SaslException;

    /**

      * Determines whether the authentication exchange has completed.

      * This method is typically called after each invocation of

      * {@code evaluateResponse()} to determine whether the

      * authentication has completed successfully or should be continued.

      * @return true if the authentication exchange has completed; false otherwise.

      */

    public abstract boolean isComplete();

    /**

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

     * session.

     * This method can only be called if isComplete() returns true.

     * @return The authorization ID of the client.

     * @exception IllegalStateException if this authentication session has not completed

     */

    public String getAuthorizationID();

    /**

     * Unwraps a byte array received from the client.

     * This method can be called only after the authentication exchange has

     * completed (i.e., when {@code isComplete()} returns true) and only if

     * the authentication exchange has negotiated integrity and/or privacy

     * as the quality of protection; otherwise,

     * an {@code IllegalStateException} is thrown.

     *<p>

     * {@code incoming} is the contents of the SASL buffer as defined in RFC 2222

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

     * {@code offset} and {@code len} specify the portion of {@code incoming}

     * to use.

     *

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

     *                from the client.

     * @param offset The starting position at {@code incoming} of the bytes to use.

     * @param len The number of bytes from {@code incoming} to use.

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

     * @exception SaslException if {@code incoming} cannot be successfully

     * unwrapped.

     * @exception IllegalStateException if the authentication exchange has

     * not completed, or if the negotiated quality of protection

     * has neither integrity nor privacy

     */

    public abstract byte[] unwrap(byte[] incoming, int offset, int len)

        throws SaslException;

    /**

     * 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 {@code isComplete()} returns true) and only if

     * the authentication exchange has negotiated integrity and/or privacy

     * as the quality of protection; otherwise, a {@code SaslException} is thrown.

     *<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} and {@code len} specify the portion of {@code outgoing}

     * to use.

     *

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

     * @param offset The starting position at {@code outgoing} of the bytes to use.

     * @param len The number of bytes from {@code outgoing} to use.

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

     * @exception SaslException if {@code outgoing} cannot be successfully

     * wrapped.

     * @exception IllegalStateException if the authentication exchange has

     * not completed, or if the negotiated quality of protection has

     * neither integrity nor privacy.

     */

    public abstract 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 {@code isComplete()} returns true); otherwise, an

     * {@code IllegalStateException} is thrown.

     * <p>

     * The {@link Sasl} class includes several well-known property names

     * (For example, {@link Sasl#QOP}). A SASL provider can support other

     * properties which are specific to the vendor and/or a mechanism.

     *

     * @param propName the property

     * @return The value of the negotiated property. If null, the property was

     * not negotiated or is not applicable to this mechanism.

     * @exception IllegalStateException if this authentication exchange has not completed

     */

    public abstract Object getNegotiatedProperty(String propName);

     /**

      * Disposes of any system resources or security-sensitive information

      * the SaslServer might be using. Invoking this method invalidates

      * the SaslServer instance. This method is idempotent.

      * @throws SaslException If a problem was encountered while disposing

      * the resources.

      */

    public abstract void dispose() throws SaslException;

}