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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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.
 *
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package com.sun.jmx.remote.security;

import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.CodeSource;
import java.security.Permissions;
import java.security.ProtectionDomain;
import javax.security.auth.Subject;
import javax.security.auth.SubjectDomainCombiner;

This class represents an extension to the SubjectDomainCombiner and is used to add a new ProtectionDomain, comprised of a null codesource/signers and an empty permission set, to the access control context with which this combiner is combined.
When the combine method is called the ProtectionDomain is augmented with the permissions granted to the set of principals present in the supplied Subject.
/**
 * <p>This class represents an extension to the {@link SubjectDomainCombiner}
 * and is used to add a new {@link ProtectionDomain}, comprised of a null
 * codesource/signers and an empty permission set, to the access control
 * context with which this combiner is combined.</p>
 *
 * <p>When the {@link #combine} method is called the {@link ProtectionDomain}
 * is augmented with the permissions granted to the set of principals present
 * in the supplied {@link Subject}.</p>
 */
public class JMXSubjectDomainCombiner extends SubjectDomainCombiner {

    public JMXSubjectDomainCombiner(Subject s) {
        super(s);
    }

    public ProtectionDomain[] combine(ProtectionDomain[] current,
                                      ProtectionDomain[] assigned) {
        // Add a new ProtectionDomain with the null codesource/signers, and
        // the empty permission set, to the end of the array containing the
        // 'current' protections domains, i.e. the ones that will be augmented
        // with the permissions granted to the set of principals present in
        // the supplied subject.
        //
        ProtectionDomain[] newCurrent;
        if (current == null || current.length == 0) {
            newCurrent = new ProtectionDomain[1];
            newCurrent[0] = pdNoPerms;
        } else {
            newCurrent = new ProtectionDomain[current.length + 1];
            for (int i = 0; i < current.length; i++) {
                newCurrent[i] = current[i];
            }
            newCurrent[current.length] = pdNoPerms;
        }
        return super.combine(newCurrent, assigned);
    }

    
A null CodeSource.
/**
     * A null CodeSource.
     */
    private static final CodeSource nullCodeSource =
        new CodeSource(null, (java.security.cert.Certificate[]) null);

    
A ProtectionDomain with a null CodeSource and an empty permission set.
/**
     * A ProtectionDomain with a null CodeSource and an empty permission set.
     */
    private static final ProtectionDomain pdNoPerms =
        new ProtectionDomain(nullCodeSource, new Permissions(), null, null);

    
Get the current AccessControlContext combined with the supplied subject.
/**
     * Get the current AccessControlContext combined with the supplied subject.
     */
    public static AccessControlContext getContext(Subject subject) {
        return new AccessControlContext(AccessController.getContext(),
                                        new JMXSubjectDomainCombiner(subject));
    }

    
Get the AccessControlContext of the domain combiner created with
the supplied subject, i.e. an AccessControlContext with the domain
combiner created with the supplied subject and where the caller's
context has been removed.
/**
     * Get the AccessControlContext of the domain combiner created with
     * the supplied subject, i.e. an AccessControlContext with the domain
     * combiner created with the supplied subject and where the caller's
     * context has been removed.
     */
    public static AccessControlContext
        getDomainCombinerContext(Subject subject) {
        return new AccessControlContext(
            new AccessControlContext(new ProtectionDomain[0]),
            new JMXSubjectDomainCombiner(subject));
    }
}