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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package sun.security.jgss;

import java.lang.reflect.InvocationTargetException;

import org.ietf.jgss.*;

import java.security.AccessController;

import java.security.Provider;

import java.security.Security;

import java.util.ArrayList;

import java.util.HashSet;

import java.util.HashMap;

import java.util.Enumeration;

import java.util.Iterator;

import sun.security.jgss.spi.*;

import sun.security.jgss.wrapper.NativeGSSFactory;

import sun.security.jgss.wrapper.SunNativeProvider;

import sun.security.action.GetPropertyAction;

/**

 * This class stores the list of providers that this

 * GSS-Implementation is configured to use. The GSSManagerImpl class

 * queries this class whenever it needs a mechanism's factory.<p>

 *

 * This class stores an ordered list of pairs of the form

 * <provider, oid>. When it attempts to instantiate a mechanism

 * defined by oid o, it steps through the list looking for an entry

 * with oid=o, or with oid=null. (An entry with oid=null matches all

 * mechanisms.) When it finds such an entry, the corresponding

 * provider is approached for the mechanism's factory class.

 * At instantiation time this list in initialized to contain those

 * system wide providers that contain a property of the form

 * "GssApiMechanism.x.y.z..." where "x.y.z..." is a numeric object

 * identifier with numbers x, y, z, etc. Such a property is defined

 * to map to that provider's implementation of the MechanismFactory

 * interface for the mechanism x.y.z...

 * As and when a MechanismFactory is instantiated, it is

 * cached for future use. <p>

 *

 * An application can cause more providers to be added by means of

 * the addProviderAtFront and addProviderAtEnd methods on

 * GSSManager which get delegated to this class. The

 * addProviderAtFront method can also cause a change in the ordering

 * of the providers without adding any new providers, by causing a

 * provider to move up in a list. The method addProviderAtEnd can

 * only add providers at the end of the list if they are not already

 * in the list. The rationale is that an application will call

 * addProviderAtFront when it wants a provider to be used in

 * preference over the default ones. And it will call

 * addProviderAtEnd when it wants a provider to be used in case

 * the system ones don't suffice.<p>

 *

 * If a mechanism's factory is being obtained from a provider as a

 * result of encountering a entryof the form <provider, oid> where

 * oid is non-null, then the assumption is that the application added

 * this entry and it wants this mechanism to be obtained from this

 * provider. Thus is the provider does not actually contain the

 * requested mechanism, an exception will be thrown. However, if the

 * entry were of the form <provider, null>, then it is viewed more

 * liberally and is simply skipped over if the provider does not claim to

 * support the requested mechanism.

 */

public final class ProviderList {

    private static final String PROV_PROP_PREFIX = "GssApiMechanism.";

    private static final int PROV_PROP_PREFIX_LEN =

        PROV_PROP_PREFIX.length();

    private static final String SPI_MECH_FACTORY_TYPE

        = "sun.security.jgss.spi.MechanismFactory";

    // Undocumented property?

    private static final String DEFAULT_MECH_PROP =

        "sun.security.jgss.mechanism";

    public static final Oid DEFAULT_MECH_OID;

    static {

        /*

         * Set the default mechanism. Kerberos v5 is the default

         * mechanism unless it is overridden by a system property.

         * with a valid OID value

         */

        Oid defOid = null;

        String defaultOidStr = AccessController.doPrivileged

            (new GetPropertyAction(DEFAULT_MECH_PROP));

        if (defaultOidStr != null) {

            defOid = GSSUtil.createOid(defaultOidStr);

        }

        DEFAULT_MECH_OID =

            (defOid == null ? GSSUtil.GSS_KRB5_MECH_OID : defOid);

   }

    private ArrayList<PreferencesEntry> preferences =

                        new ArrayList<PreferencesEntry>(5);

    private HashMap<PreferencesEntry, MechanismFactory> factories =

                        new HashMap<PreferencesEntry, MechanismFactory>(5);

    private HashSet<Oid> mechs = new HashSet<Oid>(5);

    final private GSSCaller caller;

    public ProviderList(GSSCaller caller, boolean useNative) {

        this.caller = caller;

        Provider[] provList;

        if (useNative) {

            provList = new Provider[1];

            provList[0] = new SunNativeProvider();

        } else {

            provList = Security.getProviders();

        }

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

            Provider prov = provList[i];

            try {

                addProviderAtEnd(prov, null);

            } catch (GSSException ge) {

                // Move on to the next provider

                GSSUtil.debug("Error in adding provider " +

                              prov.getName() + ": " + ge);

            }

        } // End of for loop

    }

    /**

     * Determines if the given provider property represents a GSS-API

     * Oid to MechanismFactory mapping.

     * @return true if this is a GSS-API property, false otherwise.

     */

    private boolean isMechFactoryProperty(String prop) {

        return (prop.startsWith(PROV_PROP_PREFIX) ||

                prop.regionMatches(true, 0, // Try ignoring case

                                   PROV_PROP_PREFIX, 0,

                                   PROV_PROP_PREFIX_LEN));

    }

    private Oid getOidFromMechFactoryProperty(String prop)

        throws GSSException {

        String oidPart = prop.substring(PROV_PROP_PREFIX_LEN);

        return new Oid(oidPart);

    }

    // So the existing code do not have to be changed

    synchronized public MechanismFactory getMechFactory(Oid mechOid)

        throws GSSException {

        if (mechOid == null) mechOid = ProviderList.DEFAULT_MECH_OID;

        return getMechFactory(mechOid, null);

    }

    /**

     * Obtains a MechanismFactory for a given mechanism. If the

     * specified provider is not null, then the impl from the

     * provider is used. Otherwise, the most preferred impl based

     * on the configured preferences is used.

     * @param mechOid the oid of the desired mechanism

     * @return a MechanismFactory for the desired mechanism.

     * @throws GSSException when the specified provider does not

     * support the desired mechanism, or when no provider supports

     * the desired mechanism.

     */

    synchronized public MechanismFactory getMechFactory(Oid mechOid,

                                                        Provider p)

        throws GSSException {

        if (mechOid == null) mechOid = ProviderList.DEFAULT_MECH_OID;

        if (p == null) {

            // Iterate thru all preferences to find right provider

            String className;

            PreferencesEntry entry;

            Iterator<PreferencesEntry> list = preferences.iterator();

            while (list.hasNext()) {

                entry = list.next();

                if (entry.impliesMechanism(mechOid)) {

                    MechanismFactory retVal = getMechFactory(entry, mechOid);

                    if (retVal != null) return retVal;

                }

            } // end of while loop

            throw new GSSExceptionImpl(GSSException.BAD_MECH, mechOid);

        } else {

            // Use the impl from the specified provider; return null if the

            // the mech is unsupported by the specified provider.

            PreferencesEntry entry = new PreferencesEntry(p, mechOid);

            return getMechFactory(entry, mechOid);

        }

    }

    /**

     * Helper routine that uses a preferences entry to obtain an

     * implementation of a MechanismFactory from it.

     * @param e the preferences entry that contains the provider and

     * either a null of an explicit oid that matched the oid of the

     * desired mechanism.

     * @param mechOid the oid of the desired mechanism

     * @throws GSSException If the application explicitly requested

     * this entry's provider to be used for the desired mechanism but

     * some problem is encountered

     */

    private MechanismFactory getMechFactory(PreferencesEntry e, Oid mechOid)

        throws GSSException {

        Provider p = e.getProvider();

        /*

         * See if a MechanismFactory was previously instantiated for

         * this provider and mechanism combination.

         */

        PreferencesEntry searchEntry = new PreferencesEntry(p, mechOid);

        MechanismFactory retVal = factories.get(searchEntry);

        if (retVal == null) {

            /*

             * Apparently not. Now try to instantiate this class from

             * the provider.

             */

            String prop = PROV_PROP_PREFIX + mechOid.toString();

            String className = p.getProperty(prop);

            if (className != null) {

                retVal = getMechFactoryImpl(p, className, mechOid, caller);

                factories.put(searchEntry, retVal);

            } else {

                /*

                 * This provider does not support this mechanism.

                 * If the application explicitly requested that

                 * this provider be used for this mechanism, then

                 * throw an exception

                 */

                if (e.getOid() != null) {

                    throw new GSSExceptionImpl(GSSException.BAD_MECH,

                         "Provider " + p.getName() +

                         " does not support mechanism " + mechOid);

                }

            }

        }

        return retVal;

    }

    /**

     * Helper routine to obtain a MechanismFactory implementation

     * from the same class loader as the provider of this

     * implementation.

     * @param p the provider whose classloader must be used for

     * instantiating the desired MechanismFactory

     * @ param className the name of the MechanismFactory class

     * @throws GSSException If some error occurs when trying to

     * instantiate this MechanismFactory.

     */

    private static MechanismFactory getMechFactoryImpl(Provider p,

                                                       String className,

                                                       Oid mechOid,

                                                       GSSCaller caller)

        throws GSSException {

        try {

            Class<?> baseClass = Class.forName(SPI_MECH_FACTORY_TYPE);

            /*

             * 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.

             */

            ClassLoader cl = p.getClass().getClassLoader();

            Class<?> implClass;

            if (cl != null) {

                implClass = cl.loadClass(className);

            } else {

                implClass = Class.forName(className);

            }

            if (baseClass.isAssignableFrom(implClass)) {

                java.lang.reflect.Constructor<?> c =

                                implClass.getConstructor(GSSCaller.class);

                MechanismFactory mf = (MechanismFactory) (c.newInstance(caller));

                if (mf instanceof NativeGSSFactory) {

                    ((NativeGSSFactory) mf).setMech(mechOid);

                }

                return mf;

            } else {

                throw createGSSException(p, className, "is not a " +

                                         SPI_MECH_FACTORY_TYPE, null);

            }

        } catch (ClassNotFoundException e) {

            throw createGSSException(p, className, "cannot be created", e);

        } catch (NoSuchMethodException e) {

            throw createGSSException(p, className, "cannot be created", e);

        } catch (InvocationTargetException e) {

            throw createGSSException(p, className, "cannot be created", e);

        } catch (InstantiationException e) {

            throw createGSSException(p, className, "cannot be created", e);

        } catch (IllegalAccessException e) {

            throw createGSSException(p, className, "cannot be created", e);

        } catch (SecurityException e) {

            throw createGSSException(p, className, "cannot be created", e);

        }

    }

    // Only used by getMechFactoryImpl

    private static GSSException createGSSException(Provider p,

                                                   String className,

                                                   String trailingMsg,

                                                   Exception cause) {

        String errClassInfo = className + " configured by " +

            p.getName() + " for GSS-API Mechanism Factory ";

        return new GSSExceptionImpl(GSSException.BAD_MECH,

                                    errClassInfo + trailingMsg,

                                    cause);

    }

    public Oid[] getMechs() {

        return mechs.toArray(new Oid[] {});

    }

    synchronized public void addProviderAtFront(Provider p, Oid mechOid)

        throws GSSException {

        PreferencesEntry newEntry = new PreferencesEntry(p, mechOid);

        PreferencesEntry oldEntry;

        boolean foundSomeMech;

        Iterator<PreferencesEntry> list = preferences.iterator();

        while (list.hasNext()) {

            oldEntry = list.next();

            if (newEntry.implies(oldEntry))

                list.remove();

        }

        if (mechOid == null) {

            foundSomeMech = addAllMechsFromProvider(p);

        } else {

            String oidStr = mechOid.toString();

            if (p.getProperty(PROV_PROP_PREFIX + oidStr) == null)

                throw new GSSExceptionImpl(GSSException.BAD_MECH,

                                           "Provider " + p.getName()

                                           + " does not support "

                                           + oidStr);

            mechs.add(mechOid);

            foundSomeMech = true;

        }

        if (foundSomeMech) {

            preferences.add(0, newEntry);

        }

    }

    synchronized public void addProviderAtEnd(Provider p, Oid mechOid)

        throws GSSException {

        PreferencesEntry newEntry = new PreferencesEntry(p, mechOid);

        PreferencesEntry oldEntry;

        boolean foundSomeMech;

        Iterator<PreferencesEntry> list = preferences.iterator();

        while (list.hasNext()) {

            oldEntry = list.next();

            if (oldEntry.implies(newEntry))

                return;

        }

        // System.out.println("addProviderAtEnd: No it is not redundant");

        if (mechOid == null)

            foundSomeMech = addAllMechsFromProvider(p);

        else {

            String oidStr = mechOid.toString();

            if (p.getProperty(PROV_PROP_PREFIX + oidStr) == null)

                throw new GSSExceptionImpl(GSSException.BAD_MECH,

                                       "Provider " + p.getName()

                                       + " does not support "

                                       + oidStr);

            mechs.add(mechOid);

            foundSomeMech = true;

        }

        if (foundSomeMech) {

            preferences.add(newEntry);

        }

    }

    /**

     * Helper routine to go through all properties contined in a

     * provider and add its mechanisms to the list of supported

     * mechanisms. If no default mechanism has been assinged so far,

     * it sets the default MechanismFactory and Oid as well.

     * @param p the provider to query

     * @return true if there is at least one mechanism that this

     * provider contributed, false otherwise

     */

    private boolean addAllMechsFromProvider(Provider p) {

        String prop;

        boolean retVal = false;

        // Get all props for this provider

        Enumeration<Object> props = p.keys();

        // See if there are any GSS prop's

        while (props.hasMoreElements()) {

            prop = (String) props.nextElement();

            if (isMechFactoryProperty(prop)) {

                // Ok! This is a GSS provider!

                try {

                    Oid mechOid = getOidFromMechFactoryProperty(prop);

                    mechs.add(mechOid);

                    retVal = true;

                } catch (GSSException e) {

                    // Skip to next property

                    GSSUtil.debug("Ignore the invalid property " +

                                  prop + " from provider " + p.getName());

                }

            } // Processed GSS property

        } // while loop

        return retVal;

    }

    /**

     * Stores a provider and a mechanism oid indicating that the

     * provider should be used for the mechanism. If the mechanism

     * Oid is null, then it indicates that this preference holds for

     * any mechanism.<p>

     *

     * The ProviderList maintains an ordered list of

     * PreferencesEntry's and iterates thru them as it tries to

     * instantiate MechanismFactory's.

     */

    private static final class PreferencesEntry {

        private Provider p;

        private Oid oid;

        PreferencesEntry(Provider p, Oid oid) {

            this.p = p;

            this.oid = oid;

        }

        public boolean equals(Object other) {

            if (this == other) {

                return true;

            }

            if (!(other instanceof PreferencesEntry)) {

                return false;

            }

            PreferencesEntry that = (PreferencesEntry)other;

            if (this.p.getName().equals(that.p.getName())) {

                if (this.oid != null && that.oid != null) {

                    return this.oid.equals(that.oid);

                } else {

                    return (this.oid == null && that.oid == null);

                }

            }

            return false;

        }

        public int hashCode() {

            int result = 17;

            result = 37 * result + p.getName().hashCode();

            if (oid != null) {

                result = 37 * result + oid.hashCode();

            }

            return result;

        }

        /**

         * Determines if a preference implies another. A preference

         * implies another if the latter is subsumed by the

         * former. e.g., <Provider1, null> implies <Provider1, OidX>

         * because the null in the former indicates that it should

         * be used for all mechanisms.

         */

        boolean implies(Object other) {

            if (other instanceof PreferencesEntry) {

                PreferencesEntry temp = (PreferencesEntry) other;

                return (equals(temp) ||

                        p.getName().equals(temp.p.getName()) &&

                        oid == null);

            } else {

                return false;

            }

        }

        Provider getProvider() {

            return p;

        }

        Oid getOid() {

            return oid;

        }

        /**

         * Determines if this entry is applicable to the desired

         * mechanism. The entry is applicable to the desired mech if

         * it contains the same oid or if it contains a null oid