/*
 * @(#)Permissions.java	1.52 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
 
package java.security;

import java.util.Enumeration; 
import java.util.Hashtable;
import java.util.NoSuchElementException;
import java.util.Map;
import java.util.HashMap;
import java.util.List;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.Collections;
import java.io.Serializable;
import java.io.ObjectStreamField;
import java.io.ObjectOutputStream;
import java.io.ObjectInputStream;
import java.io.IOException;


/**  
 * This class represents a heterogeneous collection of Permissions. That is,
 * it contains different types of Permission objects, organized into
 * PermissionCollections. For example, if any
 * <code>java.io.FilePermission</code> objects are added to an instance of
 * this class, they are all stored in a single
 * PermissionCollection. It is the PermissionCollection returned by a call to
 * the <code>newPermissionCollection</code> method in the FilePermission class.
 * Similarly, any <code>java.lang.RuntimePermission</code> objects are
 * stored in the PermissionCollection returned by a call to the 
 * <code>newPermissionCollection</code> method in the
 * RuntimePermission class. Thus, this class represents a collection of
 * PermissionCollections.
 * 
 * <p>When the <code>add</code> method is called to add a Permission, the 
 * Permission is stored in the appropriate PermissionCollection. If no such 
 * collection exists yet, the Permission object's class is determined and the
 * <code>newPermissionCollection</code> method is called on that class to create
 * the PermissionCollection and add it to the Permissions object. If
 * <code>newPermissionCollection</code> returns null, then a default 
 * PermissionCollection that uses a hashtable will be created and used. Each 
 * hashtable entry stores a Permission object as both the key and the value.
 *
 * <p> Enumerations returned via the <code>elements</code> method are
 * not <em>fail-fast</em>.  Modifications to a collection should not be
 * performed while enumerating over that collection.
 * 
 * @see Permission
 * @see PermissionCollection
 * @see AllPermission
 * 
 * @version 1.52, 03/01/23
 *
 * @author Marianne Mueller
 * @author Roland Schemers
 *
 * @serial exclude
 */

public final class Permissions extends PermissionCollection 
implements Serializable 
{
    /**
     * Key is permissions Class, value is PermissionCollection for that class.
     * Not serialized; see serialization section at end of class.
     */
    private transient Map permsMap;

    // optimization. keep track of whether unresolved permissions need to be checked
    private transient boolean hasUnresolved = false;

    // optimization. keep track of the AllPermission collection
    private PermissionCollection allPermission;

    /**
     * Creates a new Permissions object containing no PermissionCollections.
     */
    public Permissions() {
	permsMap = new HashMap(11);
	allPermission = null;
    }

    /**
     * Adds a permission object to the PermissionCollection for the class the
     * permission belongs to. For example, if <i>permission</i> is a
     * FilePermission, it is added to the FilePermissionCollection stored
     * in this Permissions object. 
     * 
     * This method creates
     * a new PermissionCollection object (and adds the permission to it)
     * if an appropriate collection does not yet exist. <p>
     *
     * @param permission the Permission object to add.
     * 
     * @exception SecurityException if this Permissions object is
     * marked as readonly.
     * 
     * @see PermissionCollection#isReadOnly()
     */

    public void add(Permission permission) {
	if (isReadOnly())
	    throw new SecurityException(
              "attempt to add a Permission to a readonly Permissions object");
	PermissionCollection pc = getPermissionCollection(permission, true);
	pc.add(permission);

        // No need to synchronize because all adds are done sequentially
	// and allPermission and hasUnresolved are set only by add()
	if (permission instanceof AllPermission) {
	    allPermission = pc;
	}
	if (permission instanceof UnresolvedPermission) {
	    hasUnresolved = true;
	}
    }

    /**
     * Checks to see if this object's PermissionCollection for permissions of
     * the specified permission's type implies the permissions 
     * expressed in the <i>permission</i> object. Returns true if the
     * combination of permissions in the appropriate PermissionCollection
     * (e.g., a FilePermissionCollection for a FilePermission) together
     * imply the specified permission.
     * 
     * <p>For example, suppose there is a FilePermissionCollection in this
     * Permissions object, and it contains one FilePermission that specifies
     * "read" access for  all files in all subdirectories of the "/tmp"
     * directory, and another FilePermission that specifies "write" access
     * for all files in the "/tmp/scratch/foo" directory.
     * Then if the <code>implies</code> method
     * is called with a permission specifying both "read" and "write" access
     * to files in the "/tmp/scratch/foo" directory, <code>true</code> is
     * returned.
     *
     * <p>Additionally, if this PermissionCollection contains the
     * AllPermission, this method will always return true.
     * <p>
     * @param permission the Permission object to check.
     *
     * @return true if "permission" is implied by the permissions in the
     * PermissionCollection it
     * belongs to, false if not.
     */

    public boolean implies(Permission permission) {
	if (allPermission != null) {
	    return true; // AllPermission has already been added
	} else {
	    PermissionCollection pc = getPermissionCollection(permission, false);
	    if (pc != null) {
		return pc.implies(permission);
	    } else {
		// none found
		return false;
	    }
	}
    }

    /**
     * Returns an enumeration of all the Permission objects in all the
     * PermissionCollections in this Permissions object.
     *
     * @return an enumeration of all the Permissions.
     */

    public Enumeration elements() {
	// go through each Permissions in the hash table 
	// and call their elements() function.

	if (hasUnresolved) {
	    // Take snapshot of what's in permsMap because permsMap might
	    // change during iteration by implies() of other threads;
	    // individual PermissionCollections won't change during implies().

	    List copy = new ArrayList();
	    synchronized (permsMap) {
		copy.addAll(permsMap.values());
	    }
	    return new PermissionsEnumerator(copy.iterator());
	} else {
	    // permsMap won't be updated during iteration; sync unnecessary
	    return new PermissionsEnumerator(permsMap.values().iterator());
	}
    }

    /** 
     * Gets the PermissionCollection in this Permissions object for
     * permissions whose type is the same as that of <i>p</i>.
     * For example, if <i>p</i> is a FilePermission,
     * the FilePermissionCollection
     * stored in this Permissions object will be returned. 
     * 
     * If createEmtpy is true, 
     * this method creates a new PermissionCollection object for the specified 
     * type of permission objects if one does not yet exist. 
     * To do so, it first calls the <code>newPermissionCollection</code> method
     * on <i>p</i>.  Subclasses of class Permission 
     * override that method if they need to store their permissions in a
     * particular PermissionCollection object in order to provide the
     * correct semantics when the <code>PermissionCollection.implies</code>
     * method is called.
     * If the call returns a PermissionCollection, that collection is stored
     * in this Permissions object. If the call returns null and createEmpty
     * is true, then
     * this method instantiates and stores a default PermissionCollection 
     * that uses a hashtable to store its permission objects.
     *
     * createEmtpy is ignored when creating empty PermissionCollection
     * for unresolved permissions because of the overhead of determining the 
     * PermissionCollection to use.
     * 
     * createEmpty should be set to false when this method is invoked from
     * implies() because it incurs the additional overhead of creating and
     * adding an empty PermissionCollection that will just return false.
     * It should be set to true when invoked from add().
     */
    private PermissionCollection getPermissionCollection(Permission p, 
	boolean createEmpty) {
	Class c = p.getClass();

	if (!hasUnresolved && !createEmpty) {
	    // No need to synchronize because updates have all been done
	    return (PermissionCollection) permsMap.get(c);
	} else {
	    PermissionCollection pc = null;

	    // synchronize because permsMap might be updated with a new 
	    // PermissionCollection
	    synchronized (permsMap) {
		pc = (PermissionCollection) permsMap.get(c);

		// Check for unresolved permissions
		if (pc == null) {
		    pc = (hasUnresolved ? getUnresolvedPermissions(p) : null);

		    // if still null, create a new collection
		    if (pc == null && createEmpty) {

			pc = p.newPermissionCollection();
			
			// still no PermissionCollection? 
			// We'll give them a PermissionsHash.
			if (pc == null)
			    pc = new PermissionsHash();
		    }

		    if (pc != null) {
			permsMap.put(c, pc);
		    }
		}
	    }
	    return pc;
	}
    }

    /**
     * Resolves any unresolved permissions of type p.
     *
     * @param p the type of unresolved permission to resolve
     *
     * @return PermissionCollection containing the unresolved permissions,
     *  or null if there were no unresolved permissions of type p.
     *
     */
    private PermissionCollection getUnresolvedPermissions(Permission p)
    {
	// Called from within synchronized method so permsMap doesn't need lock

	UnresolvedPermissionCollection uc = 
	(UnresolvedPermissionCollection) permsMap.get(UnresolvedPermission.class);

	// we have no unresolved permissions if uc is null
	if (uc == null) 
	    return null;

	List unresolvedPerms = uc.getUnresolvedPermissions(p);
	
	// we have no unresolved permissions of this type if unresolvedPerms is null
	if (unresolvedPerms == null)
	    return null;

	java.security.cert.Certificate certs[] = null;

	Object signers[] = p.getClass().getSigners();

	int n = 0;
	if (signers != null) {
	    for (int j=0; j < signers.length; j++) {
		if (signers[j] instanceof java.security.cert.Certificate) {
		    n++;
		}
	    }
	    certs = new java.security.cert.Certificate[n];
	    n = 0;
	    for (int j=0; j < signers.length; j++) {
		if (signers[j] instanceof java.security.cert.Certificate) {
		    certs[n++] = (java.security.cert.Certificate)signers[j];
		}
	    }
	}

	PermissionCollection pc = null;
	int len = unresolvedPerms.size();
	for (int i = 0; i < len; i++) {
	    UnresolvedPermission up = (UnresolvedPermission)unresolvedPerms.get(i);
	    Permission perm = up.resolve(p, certs);
	    if (perm != null) {
		if (pc == null) {
		    pc = p.newPermissionCollection();
		    if (pc == null) 
			pc = new PermissionsHash();
		}
		pc.add(perm);
	    }

	}
	return pc;
    }

    private static final long serialVersionUID = 4858622370623524688L;

    // Need to maintain serialization interoperability with earlier releases,
    // which had the serializable field:
    // private Hashtable perms;

    /**
     * @serialField perms java.util.Hashtable
     *     A table of the Permission classes and PermissionCollections.
     * @serialField allPermission java.security.PermissionCollection
     */
    private static final ObjectStreamField[] serialPersistentFields = {
        new ObjectStreamField("perms", Hashtable.class),
	new ObjectStreamField("allPermission", PermissionCollection.class),
    };

    /**
     * @serialData Default fields.
     */
    /*
     * Writes the contents of the permsMap field out as a Hashtable for
     * serialization compatibility with earlier releases. allPermission
     * unchanged.
     */
    private void writeObject(ObjectOutputStream out) throws IOException {
	// Don't call out.defaultWriteObject()

	// Copy perms into a Hashtable
	Hashtable perms = new Hashtable(permsMap.size()*2);
	perms.putAll(permsMap);

	// Write out serializable fields
        ObjectOutputStream.PutField pfields = out.putFields();
	pfields.put("allPermission", allPermission);
        pfields.put("perms", perms);
        out.writeFields();
    }

    /*
     * Reads in a Hashtable of Class/PermissionCollections and saves them in the 
     * permsMap field. Reads in allPermission.
     */
    private void readObject(ObjectInputStream in) throws IOException, 
    ClassNotFoundException {
	// Don't call defaultReadObject()

	// Read in serialized fields
	ObjectInputStream.GetField gfields = in.readFields();

	// Get allPermission
	allPermission = (PermissionCollection) gfields.get("allPermission", null);

	// Get permissions
	Hashtable perms = (Hashtable)gfields.get("perms", null);
	permsMap = new HashMap(perms.size()*2);
	permsMap.putAll(perms);

	// Set hasUnresolved
	UnresolvedPermissionCollection uc = 
	(UnresolvedPermissionCollection) permsMap.get(UnresolvedPermission.class);
	hasUnresolved = (uc != null && uc.elements().hasMoreElements());
    }
}

final class PermissionsEnumerator implements Enumeration {

    // all the perms
    private Iterator perms;
    // the current set
    private Enumeration permset;
   
    PermissionsEnumerator(Iterator e) {
	perms = e;
	permset = getNextEnumWithMore();
    }

    // No need to synchronize; caller should sync on object as required
    public boolean hasMoreElements() {
	// if we enter with permissionimpl null, we know
	// there are no more left.

	if (permset == null) 
	    return  false;

	// try to see if there are any left in the current one

	if (permset.hasMoreElements())
	    return true;

	// get the next one that has something in it...
	permset = getNextEnumWithMore();

	// if it is null, we are done!
	return (permset != null);
    }

    // No need to synchronize; caller should sync on object as required
    public Object nextElement() {

	// hasMoreElements will update permset to the next permset
	// with something in it...

	if (hasMoreElements()) {
	    return permset.nextElement();
	} else {
	    throw new NoSuchElementException("PermissionsEnumerator");
	}

    }

    private Enumeration getNextEnumWithMore() {
	while (perms.hasNext()) {
	    PermissionCollection pc = (PermissionCollection)perms.next();
	    Enumeration next = (Enumeration) pc.elements();
	    if (next.hasMoreElements())
		return next;
	}
	return null;

    }
}

/**
 * A PermissionsHash stores a homogeneous set of permissions in a hashtable.
 *
 * @see Permission
 * @see Permissions
 *
 * @version 1.52, 01/23/03
 *
 * @author Roland Schemers
 *
 * @serial include
 */

final class PermissionsHash extends PermissionCollection
implements Serializable
{
    /**
     * Key and value are (same) permissions objects.
     * Not serialized; see serialization section at end of class.
     */
    private transient Map permsMap;

    /**
     * Create an empty PermissionsHash object.
     */

    PermissionsHash() {
	permsMap = new HashMap(11);
    }

    /**
     * Adds a permission to the PermissionsHash.
     *
     * @param permission the Permission object to add.
     */

    public void add(Permission permission)
    {
	permsMap.put(permission, permission);
    }

    /**
     * Check and see if this set of permissions implies the permissions 
     * expressed in "permission".
     *
     * @param permission the Permission object to compare
     *
     * @return true if "permission" is a proper subset of a permission in 
     * the set, false if not.
     */

    public boolean implies(Permission permission) 
    {
	// attempt a fast lookup and implies. If that fails
	// then enumerate through all the permissions.
	Permission p = (Permission) permsMap.get(permission);

	// If permission is found, then p.equals(permission)
	if (p == null) {
	    Iterator enum = permsMap.values().iterator();
	    while (enum.hasNext()) {
		p = (Permission) enum.next();
		if (p.implies(permission))
		    return true;
	    }
	    return false;
	} else {
	    return true;
	}
    }

    /**
     * Returns an enumeration of all the Permission objects in the container.
     *
     * @return an enumeration of all the Permissions.
     */

    public Enumeration elements() {
        // Convert Iterator of Map values into an Enumeration
	return Collections.enumeration(permsMap.values());
    }

    private static final long serialVersionUID = -8491988220802933440L;
    // Need to maintain serialization interoperability with earlier releases,
    // which had the serializable field:
    // private Hashtable perms;
    /**
     * @serialField perms java.util.Hashtable
     *     A table of the Permissions (both key and value are same).
     */
    private static final ObjectStreamField[] serialPersistentFields = {
        new ObjectStreamField("perms", Hashtable.class),
    };

    /**
     * @serialData Default fields.
     */
    /*
     * Writes the contents of the permsMap field out as a Hashtable for
     * serialization compatibility with earlier releases.
     */
    private void writeObject(ObjectOutputStream out) throws IOException {
	// Don't call out.defaultWriteObject()

	// Copy perms into a Hashtable
	Hashtable perms = new Hashtable(permsMap.size()*2);
	perms.putAll(permsMap);

	// Write out serializable fields
        ObjectOutputStream.PutField pfields = out.putFields();
        pfields.put("perms", perms);
        out.writeFields();
    }

    /*
     * Reads in a Hashtable of Permission/Permission and saves them in the 
     * permsMap field. 
     */
    private void readObject(ObjectInputStream in) throws IOException, 
    ClassNotFoundException {
	// Don't call defaultReadObject()

	// Read in serialized fields
	ObjectInputStream.GetField gfields = in.readFields();

	// Get permissions
	Hashtable perms = (Hashtable)gfields.get("perms", null);
	permsMap = new HashMap(perms.size()*2);
	permsMap.putAll(perms);
    }
}