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## javax.security.sasl
Interface SaslClient

All Known Implementing Classes:
  AnonymousClient, ClientMechanism, CramMD5Client, PlainClient, SRPClient

public interface SaslClient

Performs SASL authentication as a client.

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 `SaslClient` instance process challenges and create responses according to the SASL mechanism implemented by the `SaslClient`. As the authentication proceeds, the instance encapsulates the state of a SASL client's authentication exchange.

Here's an example of how an LDAP library might use a `SaslClient`. It first gets an instance of a SaslClient:

    SaslClient sc =
          Sasl.createSaslClient(mechanisms, authorizationID, protocol,
                                serverName, props, callbackHandler);

It can then proceed to use the client for authentication. For example, an LDAP library might use the client as follows:

     // 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);
       }
    }

If the mechanism has an initial response, the library invokes `evaluateChallenge(byte[])` with an empty challenge to get the initial response. Protocols such as IMAP4, which do not include an initial response with their first authentication command to the server, initiate the authentication without first calling `hasInitialResponse()` or `evaluateChallenge(byte[])`. 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 `evaluateChallenge(byte[])` with an empty challenge.

See Also:
  `Sasl`, `SaslClientFactory`

Method Summary
`void` `dispose()` Disposes of any system resources or security-sensitive information the `SaslClient` might be using.
`byte[]` `evaluateChallenge(byte[] challenge)` Evaluates the challenge data and generates a response.
`java.lang.String` `getMechanismName()` Returns the IANA-registered mechanism name of this SASL client.
`java.lang.Object` `getNegotiatedProperty(java.lang.String propName)` Retrieves the negotiated property.
`boolean` `hasInitialResponse()` Determines if this mechanism has an optional initial response.
`boolean` `isComplete()` Determines if the authentication exchange has completed.
`byte[]` `unwrap(byte[] incoming, int offset, int len)` Unwraps a byte array received from the server.
`byte[]` `wrap(byte[] outgoing, int offset, int len)` Wraps a byte array to be sent to the server.

Method Detail

### getMechanismName

    public java.lang.String getMechanismName()

  Returns the IANA-registered mechanism name of this SASL client. (e.g. "CRAM-MD5", "GSSAPI").

  Returns:
    a non-null string representing the IANA-registered mechanism name.

### hasInitialResponse

    public boolean hasInitialResponse()

  Determines if this mechanism has an optional initial response. If `true`, caller should call `evaluateChallenge(byte[])` with an empty array to get the initial response.

  Returns:
    `true` if this mechanism has an initial response.

### evaluateChallenge

    public byte[] evaluateChallenge(byte[] challenge)
                             throws SaslException

  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.

  Parameters:
    `challenge` - the non-null challenge sent from the server. The challenge array may have zero length.
  Returns:
    the possibly `null` reponse 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.
  Throws:
    `SaslException` - if an error occurred while processing the challenge or generating a response.

### isComplete

    public boolean isComplete()

  Determines if 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.

  Returns:
    `true` if the authentication exchange has completed; `false` otherwise.

### unwrap

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

  Unwraps a byte array received from the server. This method can be called only after the authentication exchange has completed (i.e., when `isComplete()` returns `true`) and only if the authentication exchange has negotiated integrity and/or privacy as the quality of protection; otherwise, an `IllegalStateException` is thrown.

  `incoming` is the contents of the SASL buffer as defined in RFC 2222 without the leading four octet field that represents the length. `offset` and `len` specify the portion of incoming to use.

  Parameters:
    `incoming` - a non-null byte array containing the encoded bytes from the server.
    `offset` - the starting position at `incoming` of the bytes to use.
    `len` - the number of bytes from `incoming` to use.
  Returns:
    a non-null byte array containing the decoded bytes.
  Throws:
    `SaslException` - if `incoming` cannot be successfully unwrapped.
    `java.lang.IllegalStateException` - if the authentication exchange has not completed, or if the negotiated quality of protection has neither integrity nor privacy.

### wrap

    public byte[] wrap(byte[] outgoing,
                       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 `isComplete()` returns `true`) and only if the authentication exchange has negotiated integrity and/or privacy as the quality of protection; otherwise, an `IllegalStateException` is thrown.

  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. `offset` and `len` specify the portion of `outgoing` to use.

  Parameters:
    `outgoing` - a non-null byte array containing the bytes to encode.
    `offset` - the starting position at `outgoing` of the bytes to use.
    `len` - the number of bytes from `outgoing` to use.
  Returns:
    a non-null byte array containing the encoded bytes.
  Throws:
    `SaslException` - if `outgoing` cannot be successfully wrapped.
    `java.lang.IllegalStateException` - if the authentication exchange has not completed, or if the negotiated quality of protection has neither integrity nor privacy.

### getNegotiatedProperty

    public java.lang.Object getNegotiatedProperty(java.lang.String propName)
                                           throws SaslException

  Retrieves the negotiated property. This method can be called only after the authentication exchange has completed (i.e., when `isComplete()` returns `true`); otherwise, an `IllegalStateException` is thrown.

  Parameters:
    `propName` - the non-null property name.
  Returns:
    the value of the negotiated property. If `null`, the property was not negotiated or is not applicable to this mechanism.
  Throws:
    `java.lang.IllegalStateException` - if this authentication exchange has not completed.
    `SaslException`

### dispose

    public void dispose()
                 throws SaslException

  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 of the resources.

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