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package javax.security.sasl;

/**

 * Performs SASL authentication as a client.

 *<p>

 * A protocol library such as one for LDAP gets an instance of this

 * class in order to perform authentication defined by a specific SASL

 * mechanism. Invoking methods on the {@code SaslClient} instance

 * process challenges and create responses according to the SASL

 * mechanism implemented by the {@code SaslClient}.

 * As the authentication proceeds, the instance

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

 *<p>

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

 * It first gets an instance of a {@code SaslClient}:

 *<blockquote><pre>{@code

 * SaslClient sc = Sasl.createSaslClient(mechanisms,

 *     authorizationId, protocol, serverName, props, callbackHandler);

 *}</pre></blockquote>

 * It can then proceed to use the client for authentication.

 * For example, an LDAP library might use the client as follows:

 *<blockquote><pre>{@code

 * // Get initial response and send to server

 * byte[] response = (sc.hasInitialResponse() ? sc.evaluateChallenge(new byte[0]) :

 *     null);

 * LdapResult res = ldap.sendBindRequest(dn, sc.getName(), response);

 * while (!sc.isComplete() &&

 *     (res.status == SASL_BIND_IN_PROGRESS || res.status == SUCCESS)) {

 *     response = sc.evaluateChallenge(res.getBytes());

 *     if (res.status == SUCCESS) {

 *         // we're done; don't expect to send another BIND

 *         if (response != null) {

 *             throw new SaslException(

 *                 "Protocol error: attempting to send response after completion");

 *         }

 *         break;

 *     }

 *     res = ldap.sendBindRequest(dn, sc.getName(), response);

 * }

 * if (sc.isComplete() && res.status == SUCCESS) {

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

 *    if (qop != null

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

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

 *

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

 *      // communication with server

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

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

 *    }

 * }

 *}</pre></blockquote>

 *

 * If the mechanism has an initial response, the library invokes

 * {@code evaluateChallenge()} with an empty

 * challenge and to get initial response.

 * Protocols such as IMAP4, which do not include an initial response with

 * their first authentication command to the server, initiates the

 * authentication without first calling {@code hasInitialResponse()}

 * or {@code evaluateChallenge()}.

 * When the server responds to the command, it sends an initial challenge.

 * For a SASL mechanism in which the client sends data first, the server should

 * have issued a challenge with no data. This will then result in a call

 * (on the client) to {@code evaluateChallenge()} with an empty challenge.

 *

 * @since 1.5

 *

 * @see Sasl

 * @see SaslClientFactory

 *

 * @author Rosanna Lee

 * @author Rob Weltman

 */

public abstract interface SaslClient {

    /**

     * Returns the IANA-registered mechanism name of this SASL client.

     * (e.g. "CRAM-MD5", "GSSAPI").

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

     */

    public abstract String getMechanismName();

    /**

     * Determines whether this mechanism has an optional initial response.

     * If true, caller should call {@code evaluateChallenge()} with an

     * empty array to get the initial response.

     *

     * @return true if this mechanism has an initial response.

     */

    public abstract boolean hasInitialResponse();

    /**

     * Evaluates the challenge data and generates a response.

     * If a challenge is received from the server during the authentication

     * process, this method is called to prepare an appropriate next

     * response to submit to the server.

     *

     * @param challenge The non-null challenge sent from the server.

     * The challenge array may have zero length.

     *

     * @return The possibly null response to send to the server.

     * It is null if the challenge accompanied a "SUCCESS" status and the challenge

     * only contains data for the client to update its state and no response

     * needs to be sent to the server. The response is a zero-length byte

     * array if the client is to send a response with no data.

     * @exception SaslException If an error occurred while processing

     * the challenge or generating a response.

     */

    public abstract byte[] evaluateChallenge(byte[] challenge)

        throws SaslException;

    /**

      * Determines whether the authentication exchange has completed.

      * This method may be called at any time, but typically, it

      * will not be called until the caller has received indication

      * from the server

      * (in a protocol-specific manner) that the exchange has completed.

      *

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

      */

    public abstract boolean isComplete();

    /**

     * Unwraps a byte array received from the server.

     * 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 server.

     * @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 server.

     * 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>

     * 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 non-null property name.

     * @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 SaslClient might be using. Invoking this method invalidates

      * the SaslClient instance. This method is idempotent.

      * @throws SaslException If a problem was encountered while disposing

      * the resources.

      */

    public abstract void dispose() throws SaslException;

}