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package javax.security.sasl;

import javax.security.auth.callback.CallbackHandler;

import java.util.Enumeration;

import java.util.Iterator;

import java.util.Map;

import java.util.Set;

import java.util.HashSet;

import java.util.Collections;

import java.security.InvalidParameterException;

import java.security.NoSuchAlgorithmException;

import java.security.Provider;

import java.security.Provider.Service;

import java.security.Security;

/**

 * A static class for creating SASL clients and servers.

 *<p>

 * This class defines the policy of how to locate, load, and instantiate

 * SASL clients and servers.

 *<p>

 * For example, an application or library gets a SASL client by doing

 * something like:

 *<blockquote><pre>

 * SaslClient sc = Sasl.createSaslClient(mechanisms,

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

 *</pre></blockquote>

 * It can then proceed to use the instance to create an authentication connection.

 *<p>

 * Similarly, a server gets a SASL server by using code that looks as follows:

 *<blockquote><pre>

 * SaslServer ss = Sasl.createSaslServer(mechanism,

 *     protocol, serverName, props, callbackHandler);

 *</pre></blockquote>

 *

 * @since 1.5

 *

 * @author Rosanna Lee

 * @author Rob Weltman

 */

public class Sasl {

    // Cannot create one of these

    private Sasl() {

    }

    /**

     * 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

     * <ul>

     * <li>{@code "auth"} - authentication only</li>

     * <li>{@code "auth-int"} - authentication plus integrity protection</li>

     * <li>{@code "auth-conf"} - authentication plus integrity and confidentiality

     * protection</li>

     * </ul>

     *

     * The order of the list specifies the preference order of the client or

     * server. If this property is absent, the default qop is {@code "auth"}.

     * The value of this constant is {@code "javax.security.sasl.qop"}.

     */

    public static final String QOP = "javax.security.sasl.qop";

    /**

     * 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

     * <ul>

     * <li>{@code "low"}</li>

     * <li>{@code "medium"}</li>

     * <li>{@code "high"}</li>

     * </ul>

     * 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.

     * <BR>

     * If this property is absent, the default strength is

     * {@code "high,medium,low"}.

     * The value of this constant is {@code "javax.security.sasl.strength"}.

     */

    public static final String STRENGTH = "javax.security.sasl.strength";

    /**

     * The name of a property that specifies whether the

     * server must authenticate to the client. The property contains

     * {@code "true"} if the server must

     * authenticate the to client; {@code "false"} otherwise.

     * The default is {@code "false"}.

     * <br>The value of this constant is

     * {@code "javax.security.sasl.server.authentication"}.

     */

    public static final String SERVER_AUTH =

    "javax.security.sasl.server.authentication";

    /**

     * The name of a property that specifies the bound server name for

     * an unbound server. A server is created as an unbound server by setting

     * the {@code serverName} argument in {@link #createSaslServer} as null.

     * The property contains the bound host name after the authentication

     * exchange has completed. It is only available on the server side.

     * <br>The value of this constant is

     * {@code "javax.security.sasl.bound.server.name"}.

     */

    public static final String BOUND_SERVER_NAME =

    "javax.security.sasl.bound.server.name";

    /**

     * The name of a property that specifies the maximum size of the receive

     * buffer in bytes of {@code SaslClient}/{@code SaslServer}.

     * The property contains the string representation of an integer.

     * <br>If this property is absent, the default size

     * is defined by the mechanism.

     * <br>The value of this constant is {@code "javax.security.sasl.maxbuffer"}.

     */

    public static final String MAX_BUFFER = "javax.security.sasl.maxbuffer";

    /**

     * The name of a property that specifies the maximum size of the raw send

     * buffer in bytes of {@code SaslClient}/{@code 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.

     * <br>The value of this constant is {@code "javax.security.sasl.rawsendsize"}.

     */

    public static final String RAW_SEND_SIZE = "javax.security.sasl.rawsendsize";

    /**

     * The name of a property that specifies whether to reuse previously

     * authenticated session information. The property contains "true" if the

     * mechanism implementation may attempt to reuse previously authenticated

     * session information; it contains "false" if the implementation must

     * not reuse previously authenticated session information.  A setting of

     * "true" 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 "false".  The value of this constant

     * is "javax.security.sasl.reuse".

     *

     * 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 reusability. Such customizations are

     * implementation-dependent.

     */

     public static final String REUSE = "javax.security.sasl.reuse";

    /**

     * 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"} if such mechanisms are not permitted;

     * {@code "false"} if such mechanisms are permitted.

     * The default is {@code "false"}.

     * <br>The value of this constant is

     * {@code "javax.security.sasl.policy.noplaintext"}.

     */

    public static final String POLICY_NOPLAINTEXT =

    "javax.security.sasl.policy.noplaintext";

    /**

     * The name of a property that specifies whether

     * mechanisms susceptible to active (non-dictionary) attacks

     * are not permitted.

     * The property contains {@code "true"}

     * if mechanisms susceptible to active attacks

     * are not permitted; {@code "false"} if such mechanisms are permitted.

     * The default is {@code "false"}.

     * <br>The value of this constant is

     * {@code "javax.security.sasl.policy.noactive"}.

     */

    public static final String POLICY_NOACTIVE =

    "javax.security.sasl.policy.noactive";

    /**

     * The name of a property that specifies whether

     * mechanisms susceptible to passive dictionary attacks are not permitted.

     * The property contains {@code "true"}

     * if mechanisms susceptible to dictionary attacks are not permitted;

     * {@code "false"} if such mechanisms are permitted.

     * The default is {@code "false"}.

     *<br>

     * The value of this constant is

     * {@code "javax.security.sasl.policy.nodictionary"}.

     */

    public static final String POLICY_NODICTIONARY =

    "javax.security.sasl.policy.nodictionary";

    /**

     * The name of a property that specifies whether mechanisms that accept

     * anonymous login are not permitted. The property contains {@code "true"}

     * if mechanisms that accept anonymous login are not permitted;

     * {@code "false"}

     * if such mechanisms are permitted. The default is {@code "false"}.

     *<br>

     * The value of this constant is

     * {@code "javax.security.sasl.policy.noanonymous"}.

     */

    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"} if mechanisms that implement forward secrecy

      * between sessions are required; {@code "false"} if such mechanisms

      * are not required. The default is {@code "false"}.

      *<br>

      * The value of this constant is

      * {@code "javax.security.sasl.policy.forward"}.

      */

    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"} if mechanisms that pass

     * client credentials are required; {@code "false"}

     * if such mechanisms are not required. The default is {@code "false"}.

     *<br>

     * The value of this constant is

     * {@code "javax.security.sasl.policy.credentials"}.

     */

    public static final String POLICY_PASS_CREDENTIALS =

    "javax.security.sasl.policy.credentials";

    /**

     * The name of a property that specifies the credentials to use.

     * The property contains a mechanism-specific Java credential object.

     * Mechanism implementations may examine the value of this property

     * to determine whether it is a class that they support.

     * The property may be used to supply credentials to a mechanism that

     * supports delegated authentication.

     *<br>

     * The value of this constant is

     * {@code "javax.security.sasl.credentials"}.

     */

    public static final String CREDENTIALS = "javax.security.sasl.credentials";

    /**

     * Creates a {@code SaslClient} using the parameters supplied.

     *

     * This method uses the

     * {@extLink security_guide_jca JCA Security Provider Framework},

     * described in the

     * "Java Cryptography Architecture (JCA) Reference Guide", for

     * locating and selecting a {@code SaslClient} implementation.

     *

     * First, it

     * obtains an ordered list of {@code SaslClientFactory} instances from

     * the registered security providers for the "SaslClientFactory" service

     * and the specified SASL mechanism(s). It then invokes

     * {@code createSaslClient()} on each factory instance on the list

     * until one produces a non-null {@code SaslClient} instance. It returns

     * the non-null {@code SaslClient} instance, or null if the search fails

     * to produce a non-null {@code SaslClient} instance.

     *<p>

     * A security provider for SaslClientFactory registers with the

     * JCA Security Provider Framework keys of the form <br>

     * {@code SaslClientFactory.}<em>{@code mechanism_name}</em>

     * <br>

     * and values that are class names of implementations of

     * {@code javax.security.sasl.SaslClientFactory}.

     *

     * For example, a provider that contains a factory class,

     * {@code com.wiz.sasl.digest.ClientFactory}, that supports the

     * "DIGEST-MD5" mechanism would register the following entry with the JCA:

     * {@code SaslClientFactory.DIGEST-MD5 com.wiz.sasl.digest.ClientFactory}

     *<p>

     * See the

     * "Java Cryptography Architecture API Specification & Reference"

     * for information about how to install and configure security service

     *  providers.

     *

     * @implNote

     * The JDK Reference Implementation additionally uses the

     * {@code jdk.security.provider.preferred}

     * {@link Security#getProperty(String) Security} property to determine

     * the preferred provider order for the specified algorithm. This

     * may be different than the order of providers returned by

     * {@link Security#getProviders() Security.getProviders()}.

     *

     * @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 null 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 {@code props} contains the

     * {@code Sasl.POLICY_NOPLAINTEXT} property with the value

     * {@code "true"}, 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,

     * including any map entries with non-String keys.

     *

     * @param cbh The possibly null 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 {@code NameCallback}.

     * The password is requested by using a {@code PasswordCallback}.

     * The realm is requested by using a {@code RealmChoiceCallback} if there is a list

     * of realms to choose from, and by using a {@code RealmCallback} if

     * the realm must be entered.

     *

     *@return A possibly null {@code SaslClient} created using the parameters

     * supplied. If null, cannot find a {@code SaslClientFactory}

     * that will produce one.

     *@exception SaslException If cannot create a {@code SaslClient} because

     * of an error.

     */

    public static SaslClient createSaslClient(

        String[] mechanisms,

        String authorizationId,

        String protocol,

        String serverName,

        Map<String,?> props,

        CallbackHandler cbh) throws SaslException {

        SaslClient mech = null;

        SaslClientFactory fac;

        Service service;

        String mechName;

        for (int i = 0; i < mechanisms.length; i++) {

            if ((mechName=mechanisms[i]) == null) {

                throw new NullPointerException(

                    "Mechanism name cannot be null");

            } else if (mechName.length() == 0) {

                continue;

            }

            String type = "SaslClientFactory";

            Provider[] provs = Security.getProviders(type + "." + mechName);

            if (provs != null) {

                for (Provider p : provs) {

                    service = p.getService(type, mechName);

                    if (service == null) {

                        // no such service exists

                        continue;

                    }

                    fac = (SaslClientFactory) loadFactory(service);

                    if (fac != null) {

                        mech = fac.createSaslClient(

                            new String[]{mechanisms[i]}, authorizationId,

                            protocol, serverName, props, cbh);

                        if (mech != null) {

                            return mech;

                        }

                    }

                }

            }

        }

        return null;

    }

    private static Object loadFactory(Service service)

        throws SaslException {

        try {

            /*

             * Load the implementation class with the same class loader

             * that was used to load the provider.

             * In order to get the class loader of a class, the

             * caller's class loader must be the same as or an ancestor of

             * the class loader being returned. Otherwise, the caller must

             * have "getClassLoader" permission, or a SecurityException

             * will be thrown.

             */

            return service.newInstance(null);

        } catch (InvalidParameterException | NoSuchAlgorithmException e) {

            throw new SaslException("Cannot instantiate service " + service, e);

        }

    }

    /**

     * Creates a {@code SaslServer} for the specified mechanism.

     *

     * This method uses the

     * {@extLink security_guide_jca JCA Security Provider Framework},

     * described in the

     * "Java Cryptography Architecture (JCA) Reference Guide", for

     * locating and selecting a {@code SaslClient} implementation.

     *

     * First, it

     * obtains an ordered list of {@code SaslServerFactory} instances from

     * the registered security providers for the "SaslServerFactory" service

     * and the specified mechanism. It then invokes

     * {@code createSaslServer()} on each factory instance on the list

     * until one produces a non-null {@code SaslServer} instance. It returns

     * the non-null {@code SaslServer} instance, or null if the search fails

     * to produce a non-null {@code SaslServer} instance.

     *<p>

     * A security provider for SaslServerFactory registers with the

     * JCA Security Provider Framework keys of the form <br>

     * {@code SaslServerFactory.}<em>{@code mechanism_name}</em>

     * <br>

     * and values that are class names of implementations of

     * {@code javax.security.sasl.SaslServerFactory}.

     *

     * For example, a provider that contains a factory class,

     * {@code com.wiz.sasl.digest.ServerFactory}, that supports the

     * "DIGEST-MD5" mechanism would register the following entry with the JCA:

     * {@code SaslServerFactory.DIGEST-MD5  com.wiz.sasl.digest.ServerFactory}

     *<p>

     * See the

     * "Java Cryptography Architecture API Specification & Reference"

     * for information about how to install and configure security

     * service providers.

     *

     * @implNote

     * The JDK Reference Implementation additionally uses the

     * {@code jdk.security.provider.preferred}

     * {@link Security#getProperty(String) Security} property to determine

     * the preferred provider order for the specified algorithm. This

     * may be different than the order of providers returned by

     * {@link Security#getProviders() Security.getProviders()}.

     *

     * @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 fully qualified host name of the server, or null

     * if the server is not bound to any specific host name. If the mechanism

     * does not allow an unbound server, a {@code SaslException} will

     * be thrown.

     * @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 {@code props} contains the

     * {@code Sasl.POLICY_NOPLAINTEXT} property with the value

     * {@code "true"}, 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,

     * including any map entries with non-String keys.

     *

     * @param cbh The possibly null 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 {@code NameCallback}.

     * The password is requested by using a {@code PasswordCallback}.

     * The realm is requested by using a {@code RealmChoiceCallback} if there is a list

     * of realms to choose from, and by using a {@code RealmCallback} if

     * the realm must be entered.

     *

     *@return A possibly null {@code SaslServer} created using the parameters

     * supplied. If null, cannot find a {@code SaslServerFactory}

     * that will produce one.

     *@exception SaslException If cannot create a {@code SaslServer} because

     * of an error.

     **/

    public static SaslServer