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	/*
	* Copyright (c) 2000, 2009, Oracle and/or its affiliates. All rights reserved.
	* 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
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	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
	* {@code <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 {@code <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 {@code <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
	* indicating that it is applicable to all mechs.
	* @param mechOid the desired mechanism
	* @return true if the provider in this entry should be
	* queried for this mechanism.
	*/
	boolean impliesMechanism(Oid oid) {
	return (this.oid == null \|\| this.oid.equals(oid));
	}

	// For debugging
	public String toString() {
	StringBuffer buf = new StringBuffer("<");
	buf.append(p.getName());
	buf.append(", ");
	buf.append(oid);
	buf.append(">");
	return buf.toString();
	}
	}
	}

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