/* Sasl.java -- 
   Copyright (C) 2003, 2004, 2005  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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02111-1307 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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package javax.security.sasl;

import java.security.Provider;
import java.security.Security;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Vector;

import javax.security.auth.callback.CallbackHandler;

/**
 * <p>A static class for creating SASL clients and servers.</p>
 *
 * <p>This class defines the policy of how to locate, load, and instantiate SASL
 * clients and servers.</p>
 *
 * <p>For example, an application or library gets a SASL client instance by
 * doing something like:</p>
 *
 * <pre>
 *SaslClient sc =
 *      Sasl.createSaslClient(mechanisms, authorizationID, protocol,
 *                            serverName, props, callbackHandler);
 * </pre>
 *
 * <p>It can then proceed to use the instance to create an authenticated
 * connection.</p>
 *
 * <p>Similarly, a server gets a SASL server instance by using code that looks
 * as follows:</p>
 *
 * <pre>
 *SaslServer ss =
 *      Sasl.createSaslServer(mechanism, protocol, serverName, props,
 *                            callbackHandler);
 * </pre>
 */
public class Sasl
{

  // Constants and variables
  // -------------------------------------------------------------------------

  /**
   * <p>The name of a property that specifies the quality-of-protection to use.
   * The property contains a comma-separated, ordered list of quality-of-
   * protection values that the client or server is willing to support. A qop
   * value is one of:</p>
   *
   * <ul>
   *    <li><code>"auth"</code> - authentication only,</li>
   *    <li><code>"auth-int"</code> - authentication plus integrity
   *    protection,</li>
   *    <li><code>"auth-conf"</code> - authentication plus integrity and
   *    confidentiality protection.</li>
   * </ul>
   *
   * <p>The order of the list specifies the preference order of the client or
   * server.</p>
   *
   * <p>If this property is absent, the default qop is <code>"auth"</code>.</p>
   *
   * <p>The value of this constant is <code>"javax.security.sasl.qop"</code>.</p>
   */
  public static final String QOP = "javax.security.sasl.qop";

  /**
   * <p>The name of a property that specifies the cipher strength to use. The
   * property contains a comma-separated, ordered list of cipher strength
   * values that the client or server is willing to support. A strength value
   * is one of:</p>
   *
   * <ul>
   *    <li><code>"low"</code>,</li>
   *    <li><code>"medium"</code>,</li>
   *    <li><code>"high"</code>.</li>
   * </ul>
   *
   * <p>The order of the list specifies the preference order of the client or
   * server. An implementation should allow configuration of the meaning of
   * these values. An application may use the Java Cryptography Extension (JCE)
   * with JCE-aware mechanisms to control the selection of cipher suites that
   * match the strength values.</p>
   *
   * <p>If this property is absent, the default strength is
   * <code>"high,medium,low"</code>.</p>
   *
   * <p>The value of this constant is <code>"javax.security.sasl.strength"</code>.
   * </p>
   */
  public static final String STRENGTH = "javax.security.sasl.strength";

  /**
   * <p>The name of a property that specifies whether the server must authenticate
   * to the client. The property contains <code>"true"</code> if the server
   * must authenticate the to client; <code>"false"</code> otherwise. The
   * default is <code>"false"</code>.</p>
   *
   * <p>The value of this constant is
   * <code>"javax.security.sasl.server.authentication"</code>.</p>
   */
  public static final String SERVER_AUTH = "javax.security.sasl.server.authentication";

  /**
   * <p>The name of a property that specifies the maximum size of the receive
   * buffer in bytes of {@link SaslClient}/{@link SaslServer}. The property
   * contains the string representation of an integer.</p>
   *
   * <p>If this property is absent, the default size is defined by the
   * mechanism.</p>
   *
   * <p>The value of this constant is <code>"javax.security.sasl.maxbuffer"</code>.
   * </p>
   */
  public static final String MAX_BUFFER = "javax.security.sasl.maxbuffer";

  /**
   * <p>The name of a property that specifies the maximum size of the raw send
   * buffer in bytes of {@link SaslClient}/{@link SaslServer}. The property
   * contains the string representation of an integer. The value of this
   * property is negotiated between the client and server during the
   * authentication exchange.</p>
   *
   * <p>The value of this constant is <code>"javax.security.sasl.rawsendsize"</code>.
   * </p>
   */
  public static final String RAW_SEND_SIZE = "javax.security.sasl.rawsendsize";

  /**
   * <p>The name of a property that specifies whether mechanisms susceptible
   * to simple plain passive attacks (e.g., "PLAIN") are not permitted. The
   * property contains <code>"true"</code> if such mechanisms are not
   * permitted; <code>"false"</code> if such mechanisms are permitted. The
   * default is <code>"false"</code>.</p>
   *
   * <p>The value of this constant is <code>"javax.security.sasl.policy.noplaintext"</code>.
   * </p>
   */
  public static final String POLICY_NOPLAINTEXT = "javax.security.sasl.policy.noplaintext";

  /**
   * <p>The name of a property that specifies whether mechanisms susceptible to
   * active (non-dictionary) attacks are not permitted. The property contains
   * <code>"true"</code> if mechanisms susceptible to active attacks are not
   * permitted; <code>"false"</code> if such mechanisms are permitted. The
   * default is <code>"false"</code>.</p>
   *
   * <p>The value of this constant is <code>"javax.security.sasl.policy.noactive"</code>.
   * </p>
   */
  public static final String POLICY_NOACTIVE = "javax.security.sasl.policy.noactive";

  /**
   * <p>The name of a property that specifies whether mechanisms susceptible to
   * passive dictionary attacks are not permitted. The property contains
   * <code>"true"</code> if mechanisms susceptible to dictionary attacks are
   * not permitted; <code>"false"</code> if such mechanisms are permitted. The
   * default is <code>"false"</code>.</p>
   *
   * <p>The value of this constant is <code>"javax.security.sasl.policy.nodictionary"</code>.
   * </p>
   */
  public static final String POLICY_NODICTIONARY = "javax.security.sasl.policy.nodictionary";

  /**
   * <p>The name of a property that specifies whether mechanisms that accept
   * anonymous login are not permitted. The property contains <code>"true"</code>
   * if mechanisms that accept anonymous login are not permitted; <code>"false"
   * </code> if such mechanisms are permitted. The default is <code>"false"</code>.
   * </p>
   *
   * <p>The value of this constant is <code>"javax.security.sasl.policy.noanonymous"</code>.
   * </p>
   */
  public static final String POLICY_NOANONYMOUS = "javax.security.sasl.policy.noanonymous";

  /**
   * The name of a property that specifies whether mechanisms that implement
   * forward secrecy between sessions are required. Forward secrecy means that
   * breaking into one session will not automatically provide information for
   * breaking into future sessions. The property contains <code>"true"</code>
   * if mechanisms that implement forward secrecy between sessions are
   * required; <code>"false"</code> if such mechanisms are not required. The
   * default is <code>"false"</code>.
   *
   * <p>The value of this constant is <code>"javax.security.sasl.policy.forward"</code>.
   * </p>
   */
  public static final String POLICY_FORWARD_SECRECY = "javax.security.sasl.policy.forward";

  /**
   * The name of a property that specifies whether mechanisms that pass client
   * credentials are required. The property contains <code>"true"</code> if
   * mechanisms that pass client credentials are required; <code>"false"</code>
   * if such mechanisms are not required. The default is <code>"false"</code>.
   *
   * <p>The value of this constant is <code>"javax.security.sasl.policy.credentials"</code>.
   * </p>
   */
  public static final String POLICY_PASS_CREDENTIALS = "javax.security.sasl.policy.credentials";

  /**
   * <p>The name of a property that specifies whether to reuse previously
   * authenticated session information. The property contains <code>"true"</code>
   * if the mechanism implementation may attempt to reuse previously
   * authenticated session information; it contains <code>"false"</code> if the
   * implementation must not reuse previously authenticated session information.
   * A setting of <code>"true"</code> serves only as a hint; it does not
   * necessarily entail actual reuse because reuse might not be possible due to
   * a number of reasons, including, but not limited to, lack of mechanism
   * support for reuse, expiration of reusable information, and the peer's
   * refusal to support reuse. The property's default value is <code>"false"</code>.
   * </p>
   *
   * <p>The value of this constant is <code>"javax.security.sasl.reuse"</code>.
   * Note that all other parameters and properties required to create a SASL
   * client/server instance must be provided regardless of whether this
   * property has been supplied. That is, you cannot supply any less
   * information in anticipation of reuse. Mechanism implementations that
   * support reuse might allow customization of its implementation for factors
   * such as cache size, timeouts, and criteria for reuseability. Such
   * customizations are implementation-dependent.</p>
   */
  public static final String REUSE = "javax.security.sasl.reuse";

  private static final String CLIENT_FACTORY_SVC = "SaslClientFactory.";
  private static final String SERVER_FACTORY_SVC = "SaslServerFactory.";
  private static final String ALIAS = "Alg.Alias.";

  // Constructor(s)
  // -------------------------------------------------------------------------

  private Sasl()
  {
    super();
  }

  // Class methods
  // -------------------------------------------------------------------------

  /**
   * Creates a {@link SaslClient} for the specified mechanism.
   *
   * <p>This method uses the JCA Security Provider Framework, described in the
   * "Java Cryptography Architecture API Specification &amp; Reference", for
   * locating and selecting a {@link SaslClient} implementation.</p>
   *
   * <p>First, it obtains an ordered list of {@link SaslClientFactory}
   * instances from the registered security providers for the
   * <code>"SaslClientFactory"</code> service and the specified mechanism. It
   * then invokes <code>createSaslClient()</code> on each factory instance on
   * the list until one produces a non-null {@link SaslClient} instance. It
   * returns the non-null {@link SaslClient} instance, or <code>null</code> if
   * the search fails to produce a non-null {@link SaslClient} instance.</p>
   *
   * <p>A security provider for <code>SaslClientFactory</code> registers with
   * the JCA Security Provider Framework keys of the form:</p>
   *
   * <pre>
   *    SaslClientFactory.mechanism_name
   * </pre>
   *
   * <p>and values that are class names of implementations of {@link
   * SaslClientFactory}.</p>
   *
   * <p>For example, a provider that contains a factory class,
   * <code>com.wiz.sasl.digest.ClientFactory</code>, that supports the
   * <code>"DIGEST-MD5"</code> mechanism would register the following entry
   * with the JCA:</p>
   *
   * <pre>
   *    SaslClientFactory.DIGEST-MD5     com.wiz.sasl.digest.ClientFactory
   * </pre>
   *
   * <p>See the "Java Cryptography Architecture API Specification &amp;
   * Reference" for information about how to install and configure security
   * service providers.</p>
   *
   * @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 <code>null</code> 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 null set of properties used to select the SASL
   * mechanism and to configure the authentication exchange of the selected
   * mechanism. For example, if props contains the {@link Sasl#POLICY_NOPLAINTEXT}
   * property with the value <code>"true"</code>, then the selected SASL
   * mechanism must not be susceptible to simple plain passive attacks. In
   * addition to the standard properties declared in this class, 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>, the method could not find a
   * {@link SaslClientFactory} that will produce one.
   * @throws SaslException if a {@link SaslClient} cannot be created because
   * of an error.
   */
  public static SaslClient createSaslClient(String[] mechanisms,
                                            String authorizationID,
                                            String protocol,
                                            String serverName, Map props,
                                            CallbackHandler cbh)
    throws SaslException
  {
    if (mechanisms == null)
      {
        return null;
      }
    Provider[] providers = Security.getProviders();
    if (providers == null || providers.length == 0)
      {
        return null;
      }

    SaslClient result = null;
    SaslClientFactory factory = null;
    String m, clazz = null, upper, alias;
    int j;
    Provider p;
    for (int i = 0; i < mechanisms.length; i++)
      {
        m = mechanisms[i];
        if (m == null)
          continue;
        for (j = 0; j < providers.length; j++)
          {
            p = providers[j];
            if (p != null)
              {
                // try the name as is
                clazz = p.getProperty(CLIENT_FACTORY_SVC + m);
                if (clazz == null) // try all uppercase
                  {
                    upper = m.toUpperCase();
                    clazz = p.getProperty(CLIENT_FACTORY_SVC + upper);
                    if (clazz == null) // try if it's an alias
                      {
                        alias = p.getProperty(ALIAS + CLIENT_FACTORY_SVC + m);
                        if (alias == null) // try all-uppercase alias name
                          {
                            alias = p.getProperty(ALIAS + CLIENT_FACTORY_SVC + upper);
                            if (alias == null) // spit the dummy
                              continue;
                          }
                        clazz = p.getProperty(CLIENT_FACTORY_SVC + alias);
                      }
                  }
                if (clazz == null)
                  continue;
                else
                  clazz = clazz.trim();
              }

            try
              {
                result = null;
                factory = (SaslClientFactory) Class.forName(clazz).newInstance();
                result = factory.createSaslClient(mechanisms, authorizationID,
                                                  protocol, serverName, props, cbh);
              }
            catch (ClassCastException ignored) // ignore instantiation exceptions
              {
              }
            catch (ClassNotFoundException ignored)
              {
              }
            catch (InstantiationException ignored)
              {
              }
            catch (IllegalAccessException ignored)
              {
              }
            if (result != null)
              return result;
          }
      }
    return null;
  }

  /**
   * Gets an enumeration of known factories for producing a {@link SaslClient}
   * instance. This method uses the same sources for locating factories as
   * <code>createSaslClient()</code>.
   *
   * @return a non-null {@link Enumeration} of known factories for producing a
   * {@link SaslClient} instance.
   * @see #createSaslClient(String[],String,String,String,Map,CallbackHandler)
   */
  public static Enumeration getSaslClientFactories()
  {
    Vector result = new Vector();
    HashSet names = new HashSet();
    Provider[] providers = Security.getProviders();
    Iterator it;
    if (providers == null)
      {
        Provider p;
        String key;
        for (int i = 0; i < providers.length; i++)
          {
            p = providers[i];
            for (it = p.keySet().iterator(); it.hasNext(); )
              {
                key = (String) it.next();
                // add key's binding (a) it is a class of a client factory,
                // and (b) the key does not include blanks
                if (key.startsWith(CLIENT_FACTORY_SVC) && key.indexOf(" ") == -1)
                  {
                    names.add(p.getProperty(key));
                    break;
                  }
              }
          }
      }
    // we have the factory class names in names; instantiate and enumerate
    String c;
    for (it = names.iterator(); it.hasNext(); )
      {
        c = (String) it.next();
        try
          {
            SaslClientFactory f = (SaslClientFactory) Class.forName(c).newInstance();
            if (f != null)
              result.add(f);
          } catch (ClassCastException ignored) { // ignore instantiation exceptions
          } catch (ClassNotFoundException ignored) {
          } catch (InstantiationException ignored) {
          } catch (IllegalAccessException ignored) {
          }
      }

    return result.elements();
  }

  /**
   * Creates a {@link SaslServer} for the specified mechanism.
   *
   * <p>This method uses the JCA Security Provider Framework, described in the
   * "Java Cryptography Architecture API Specification &amp; Reference", for
   * locating and selecting a SaslServer implementation.</p>
   *
   * <p>First, it obtains an ordered list of {@link SaslServerFactory}
   * instances from the registered security providers for the
   * <code>"SaslServerFactory"</code> service and the specified mechanism. It
   * then invokes <code>createSaslServer()</code> on each factory instance on
   * the list until one produces a non-null {@link SaslServer} instance. It
   * returns the non-null {@link SaslServer} instance, or <code>null</code> if
   * the search fails to produce a non-null {@link SaslServer} instance.</p>
   *
   * <p>A security provider for {@link SaslServerFactory} registers with the
   * JCA Security Provider Framework keys of the form:</p>
   *
   * <pre>
   *    SaslServerFactory.mechanism_name
   * </pre>
   *
   * <p>and values that are class names of implementations of {@link
   * SaslServerFactory}.</p>
   *
   * <p>For example, a provider that contains a factory class,
   * <code>com.wiz.sasl.digest.ServerFactory</code>, that supports the
   * <code>"DIGEST-MD5"</code> mechanism would register the following entry
   * with the JCA:</p>
   *
   * <pre>
   *    SaslServerFactory.DIGEST-MD5     com.wiz.sasl.digest.ServerFactory
   * </pre>
   *
   * <p>See the "Java Cryptography Architecture API Specification &amp;
   * Reference" for information about how to install and configure security
   * service providers.</p>
   *
   * @param mechanism the non-null mechanism name. It must be an
   * IANA-registered name of a SASL mechanism. (e.g. "GSSAPI", "CRAM-MD5").
   * @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.
   * @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. For example, if props contains the {@link
   * Sasl#POLICY_NOPLAINTEXT} property with the value <code>"true"</code>, then
   * the selected SASL mechanism must not be susceptible to simple plain
   * passive attacks. In addition to the standard properties declared in this
   * class, 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 SaslServer} created using the
   * parameters supplied. If <code>null</code>, the method cannot find a
   * {@link SaslServerFactory} instance that will produce one.
   * @throws SaslException if a {@link SaslServer} instance cannot be created
   * because of an error.
   */
  public static SaslServer createSaslServer(String mechanism, String protocol,
                                            String serverName,
                                            Map props, CallbackHandler cbh)
    throws SaslException
  {
    if (mechanism == null)
      return null;
    Provider[] providers = Security.getProviders();
    if (providers == null || providers.length == 0)
      return null;

    SaslServer result = null;
    SaslServerFactory factory = null;
    String clazz = null, upper, alias = null;
    int j;
    Provider p;
    for (j = 0; j < providers.length; j++)
      {
        p = providers[j];
        if (p != null)
          {
            // try the name as is
            clazz = p.getProperty(SERVER_FACTORY_SVC + mechanism);
            if (clazz == null) // try all uppercase
              {
                upper = mechanism.toUpperCase();
                clazz = p.getProperty(SERVER_FACTORY_SVC + upper);
                if (clazz == null) // try if it's an alias
                  {
                    alias = p.getProperty(ALIAS + SERVER_FACTORY_SVC + mechanism);
                    if (alias == null) // try all-uppercase alias name
                      {
                        alias = p.getProperty(ALIAS + SERVER_FACTORY_SVC + upper);
                        if (alias == null) // spit the dummy
                          continue;
                      }
                  }
                clazz = p.getProperty(SERVER_FACTORY_SVC + alias);
              }
          }
        if (clazz == null)
          continue;
        else
          clazz = clazz.trim();

        try
          {
            result = null;
            factory = (SaslServerFactory) Class.forName(clazz).newInstance();
            result =
              factory.createSaslServer(mechanism, protocol, serverName, props, cbh);
          }
        catch (ClassCastException ignored) // ignore instantiation exceptions
          {
          }
        catch (ClassNotFoundException ignored)
          {
          }
        catch (InstantiationException ignored)
          {
          }
        catch (IllegalAccessException ignored)
          {
          }
        if (result != null)
          return result;
      }
    return null;
  }

  /**
   * Gets an enumeration of known factories for producing a {@link SaslServer}
   * instance. This method uses the same sources for locating factories as
   * <code>createSaslServer()</code>.
   *
   * @return a non-null {@link Enumeration} of known factories for producing a
   * {@link SaslServer} instance.
   * @see #createSaslServer(String,String,String,Map,CallbackHandler)
   */
  public static Enumeration getSaslServerFactories()
  {
    Vector result = new Vector();
    HashSet names = new HashSet();
    Provider[] providers = Security.getProviders();
    Iterator it;
    if (providers == null)
      {
        Provider p;
        String key;
        for (int i = 0; i < providers.length; i++)
          {
            p = providers[i];
            for (it = p.keySet().iterator(); it.hasNext(); )
              {
                key = (String) it.next();
                // add key's binding (a) it is a class of a server factory,
                // and (b) the key does not include blanks
                if (key.startsWith(SERVER_FACTORY_SVC) && key.indexOf(" ") == -1)
                  {
                    names.add(p.getProperty(key));
                    break;
                  }
              }
          }
      }
    // we have the factory class names in names; instantiate and enumerate
    String c;
    for (it = names.iterator(); it.hasNext(); )
      {
        c = (String) it.next();
        try
          {
            SaslServerFactory f = (SaslServerFactory) Class.forName(c).newInstance();
            if (f != null)
              result.add(f);
          }
        catch (ClassCastException ignored) // ignore instantiation exceptions
          {
          }
        catch (ClassNotFoundException ignored)
          {
          }
        catch (InstantiationException ignored)
          {
          }
        catch (IllegalAccessException ignored)
          {
          }
      }

    return result.elements();
  }
}