/* SaslClientFactory.java
   Copyright (C) 2003, Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
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;

import java.util.Map;

import javax.security.auth.callback.CallbackHandler;

/**
 * <p>An interface for creating instances of {@link SaslClient}. A class that
 * implements this interface must be thread-safe and handle multiple
 * simultaneous requests. It must also have a public constructor that accepts
 * no arguments.</p>
 *
 * <p>This interface is not normally accessed directly by a client, which will
 * use the {@link Sasl} static methods to create a client instance instead.
 * However, a particular environment may provide and install a new or different
 * <code>SaslClientFactory</code>.</p>
 *
 * @see SaslClient
 * @see Sasl
 */
public interface SaslClientFactory
{

  /**
   * Creates a {@link SaslClient} using the parameters supplied.
   *
   * @param mechanisms the non-null list of mechanism names to try. Each is the
   * IANA-registered name of a SASL mechanism (e.g. "GSSAPI", "CRAM-MD5").
   * @param authorizationID the possibly null protocol-dependent identification
   * to be used for authorization. If <code>null</code> or empty, the server
   * derives an authorization ID from the client's authentication credentials.
   * When the SASL authentication completes successfully, the specified entity
   * is granted access.
   * @param protocol the non-null string name of the protocol for which the
   * authentication is being performed (e.g. "ldap").
   * @param serverName the non-null fully qualified host name of the server to
   * authenticate to.
   * @param props the possibly <code>null</code> set of properties used to
   * select the SASL mechanism and to configure the authentication exchange of
   * the selected mechanism. See the {@link Sasl} class for a list of standard
   * properties. Other, possibly mechanism-specific, properties can be included.
   * Properties not relevant to the selected mechanism are ignored.
   * @param cbh the possibly <code>null</code> callback handler to used by the
   * SASL mechanisms to get further information from the application/library to
   * complete the authentication. For example, a SASL mechanism might require
   * the authentication ID, password and realm from the caller. The
   * authentication ID is requested by using a
   * {@link javax.security.auth.callback.NameCallback}. The password is
   * requested by using a {@link javax.security.auth.callback.PasswordCallback}.
   * The realm is requested by using a {@link RealmChoiceCallback} if there is
   * a list of realms to choose from, and by using a {@link RealmCallback} if
   * the realm must be entered.
   * @return a possibly <code>null</code> {@link SaslClient} created using the
   * parameters supplied. If <code>null</code>, this factory cannot produce a
   * {@link SaslClient} using the parameters supplied.
   * @throws SaslException if a {@link SaslClient} instance cannot be created
   * because of an error.
   */
  SaslClient createSaslClient(String[] mechanisms, String authorizationID,
                              String protocol, String serverName, Map props,
                              CallbackHandler cbh)
    throws SaslException;

  /**
   * Returns an array of names of mechanisms that match the specified mechanism
   * selection policies.
   *
   * @param props the possibly <code>null</code> set of properties used to
   * specify the security policy of the SASL mechanisms. For example, if props
   * contains the {@link Sasl#POLICY_NOPLAINTEXT} property with the value
   * <code>"true"</code>, then the factory must not return any SASL mechanisms
   * that are susceptible to simple plain passive attacks. See the {@link Sasl}
   * class for a complete list of policy properties. Non-policy related
   * properties, if present in props, are ignored.
   * @return a non-null array containing IANA-registered SASL mechanism names.
   */
  String[] getMechanismNames(Map props);
}