Apple Developer Connection Student Program/ADC Tools Sampler CD Disk 3 1999.iso/Metrowerks CodeWarrior/Java Support/Java_Source/Java2/src/java/security/Permissions.java

Java Source | 1999-05-28 | 12.4 KB | 417 lines | [TEXT/CWIE]

/*
 * @(#)Permissions.java    1.37 98/07/30
 *
 * Copyright 1997, 1998 by Sun Microsystems, Inc.,
 * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
 * All rights reserved.
 *
 * This software is the confidential and proprietary information
 * of Sun Microsystems, Inc. ("Confidential Information").  You
 * shall not disclose such Confidential Information and shall use
 * it only in accordance with the terms of the license agreement
 * you entered into with Sun.
 */

package java.security;

import java.util.Enumeration;
import java.util.Hashtable;
import java.util.NoSuchElementException;
import java.io.Serializable;
import java.util.ArrayList;

/**
 * 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.
 *
 * @see Permission
 * @see PermissionCollection
 * @see AllPermission
 *
 * @version 1.37, 99/03/26
 *
 * @author Marianne Mueller
 * @author Roland Schemers
 */

public final class Permissions extends PermissionCollection
implements Serializable
{

    private Hashtable perms;

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

    /**
     * Creates a new Permissions object containing no PermissionCollections.
     */
    public Permissions() {
    perms = new Hashtable(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 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);
    pc.add(permission);
    if (permission instanceof AllPermission) {
        allPermission = pc;
    }
    }

    /**
     * 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) {
    PermissionCollection pc = getPermissionCollection(permission);

    if (allPermission != null && allPermission.implies(permission))
        return true;
    else
        return pc.implies(permission);
    }

    /**
     * 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.
    return new PermissionsEnumerator(perms.elements());
    }

    /**
     * Returns an enumeration of all the Permission objects with the same
     * type as <i>p</i>.
     *
     * @param p the prototype Permission object.
     *
     * @return an enumeration of all the Permissions with the same type as <i>p</i>.
     */

    // XXX this could be public. Question is, do we want to make it public?
    // it is currently trivial to implement, but that might change...

    private Enumeration elements(Permission p) {
    PermissionCollection pc = getPermissionCollection(p);
    return pc.elements();
    }

    /**
     * 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.
     *
     * 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, then
     * this method instantiates and stores a default PermissionCollection
     * that uses a hashtable to store its permission objects.
     */

    private PermissionCollection getPermissionCollection(Permission p) {
    Class c = p.getClass();
    PermissionCollection pc = (PermissionCollection) perms.get(c);
    if (pc == null) {
        synchronized (perms) {
        // check again, in case someone else created one
        // between the time we checked and the time we
        // got the lock. We do this here to avoid
        // making this whole method synchronized, because
        // it is called by every public method.
        pc = (PermissionCollection) perms.get(c);

        //check for unresolved permissions
        if (pc == null) {

            pc = getUnresolvedPermissions(p);

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

            pc = p.newPermissionCollection();

            // still no PermissionCollection?
            // We'll give them a PermissionsHash.
            if (pc == null)
                pc = new PermissionsHash();
            }
        }
        perms.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)
    {
    UnresolvedPermissionCollection uc =
    (UnresolvedPermissionCollection) perms.get(UnresolvedPermission.class);

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

    java.util.Vector v = uc.getUnresolvedPermissions(p);

    // we have no unresolved permissions of this type if v is null
    if (v == 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;
    Enumeration e = v.elements();

    while(e.hasMoreElements()) {
        UnresolvedPermission up = (UnresolvedPermission) e.nextElement();
        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;
    }
}

final class PermissionsEnumerator implements Enumeration {

    // all the perms
    private Enumeration perms;
    // the current set
    private Enumeration permset;

    PermissionsEnumerator(Enumeration e) {
    perms = e;
    permset = getNextEnumWithMore();
    }

    public synchronized 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);
    }

    public synchronized 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.hasMoreElements()) {
        PermissionCollection pc = (PermissionCollection) perms.nextElement();
        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 1.37, 99/03/26
 *
 * @author Roland Schemers
 */

final class PermissionsHash extends PermissionCollection
implements Serializable
{

    private Hashtable perms;

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

    PermissionsHash() {
    perms = new Hashtable(11);
    }

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

    public void add(Permission permission)
    {
    perms.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) perms.get(permission);
    if ((p == null) || (!p.implies(permission))) {
        Enumeration enum = elements();
        try {
        while (enum.hasMoreElements()) {
            p = (Permission) enum.nextElement();
            if (p.implies(permission))
            return true;
        }
        } catch (NoSuchElementException e){
        // ignore
        }
        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()
    {
    return perms.elements();
    }
}