https://openjdk.java.net/ 
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 * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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
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 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * accompanied this code).
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 */

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.Iterator;
import java.util.Collections;
import java.util.concurrent.ConcurrentHashMap;
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 java.io.FilePermission 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 newPermissionCollection method in the FilePermission class. Similarly, any java.lang.RuntimePermission objects are stored in the PermissionCollection returned by a call to the newPermissionCollection method in the RuntimePermission class. Thus, this class represents a collection of PermissionCollections. 
When the add 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 newPermissionCollection method is called on that class to create the PermissionCollection and add it to the Permissions object. If newPermissionCollection 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. 
 Enumerations returned via the elements method are not fail-fast.  Modifications to a collection should not be
performed while enumerating over that collection.

Author:Marianne Mueller, Roland Schemers
See Also:
Since:1.2
@serialexclude
/**
 * 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} 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} method in the FilePermission class.
 * Similarly, any {@code java.lang.RuntimePermission} objects are
 * stored in the PermissionCollection returned by a call to the
 * {@code newPermissionCollection} method in the
 * RuntimePermission class. Thus, this class represents a collection of
 * PermissionCollections.
 *
 * <p>When the {@code add} 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} method is called on that class to create
 * the PermissionCollection and add it to the Permissions object. If
 * {@code newPermissionCollection} 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} 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
 *
 *
 * @author Marianne Mueller
 * @author Roland Schemers
 * @since 1.2
 *
 * @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.

/**
     * Key is permissions Class, value is PermissionCollection for that class.
     * Not serialized; see serialization section at end of class.
     */
    private transient ConcurrentHashMap<Class<?>, PermissionCollection> permsMap;

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

    // optimization. keep track of the AllPermission collection
    // - package private for ProtectionDomain optimization
    PermissionCollection allPermission;

    
Creates a new Permissions object containing no PermissionCollections.

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

    
Adds a permission object to the PermissionCollection for the class the
permission belongs to. For example, if permission 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.

Params:
  • permission – the Permission object to add.
Throws:
See Also:
/**
     * 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.
     *
     * @param permission the Permission object to add.
     *
     * @exception SecurityException if this Permissions object is
     * marked as readonly.
     *
     * @see PermissionCollection#isReadOnly()
     */
    @Override
    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 sync; staleness -> optimizations delayed, which is OK
        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 class implies the permissions
expressed in the permission object. Returns true if the
combination of permissions in the appropriate PermissionCollection
(e.g., a FilePermissionCollection for a FilePermission) together
imply the specified permission.

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 implies method is called with a permission specifying both "read" and "write" access to files in the "/tmp/scratch/foo" directory, true is returned. 
Additionally, if this PermissionCollection contains the
AllPermission, this method will always return true.

Params:
  • permission – the Permission object to check.
Returns:true if "permission" is implied by the permissions in the
PermissionCollection it
belongs to, false if not.
/**
     * Checks to see if this object's PermissionCollection for permissions of
     * the specified permission's class 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} method
     * is called with a permission specifying both "read" and "write" access
     * to files in the "/tmp/scratch/foo" directory, {@code true} is
     * returned.
     *
     * <p>Additionally, if this PermissionCollection contains the
     * AllPermission, this method will always return true.
     *
     * @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.
     */
    @Override
    public boolean implies(Permission permission) {
        // No sync; staleness -> skip optimization, which is OK
        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.

Returns:an enumeration of all the Permissions.
/**
     * Returns an enumeration of all the Permission objects in all the
     * PermissionCollections in this Permissions object.
     *
     * @return an enumeration of all the Permissions.
     */
    @Override
    public Enumeration<Permission> elements() {
        // go through each Permissions in the hash table
        // and call their elements() function.

        return new PermissionsEnumerator(permsMap.values().iterator());
    }

    
Gets the PermissionCollection in this Permissions object for
permissions whose type is the same as that of p.
For example, if p is a FilePermission, the FilePermissionCollection stored in this Permissions object will be returned. If createEmpty 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 newPermissionCollection method on p. 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 PermissionCollection.implies 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. createEmpty 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(). 
/**
     * 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 createEmpty 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} 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}
     * 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.
     *
     * createEmpty 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) {
            return permsMap.get(c);
        }

        // Create and add permission collection to map if it is absent.
        // NOTE: cannot use lambda for mappingFunction parameter until
        // JDK-8076596 is fixed.
        return permsMap.computeIfAbsent(c,
            new java.util.function.Function<>() {
                @Override
                public PermissionCollection apply(Class<?> k) {
                    // Check for unresolved permissions
                    PermissionCollection 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();
                        }
                    }
                    return pc;
                }
            }
        );
    }

    
Resolves any unresolved permissions of type p.

Params:
  • p – the type of unresolved permission to resolve
Returns:PermissionCollection containing the unresolved permissions,
 or null if there were no unresolved permissions of type p.
/**
     * 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) permsMap.get(UnresolvedPermission.class);

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

        List<UnresolvedPermission> 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;
        synchronized (unresolvedPerms) {
            int len = unresolvedPerms.size();
            for (int i = 0; i < len; i++) {
                UnresolvedPermission up = 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;

    
@serialFieldperms java.util.Hashtable
    A table of the Permission classes and PermissionCollections.
@serialFieldallPermission java.security.PermissionCollection
/**
     * @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),
    };

    
@serialDataDefault fields.
/**
     * @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<Class<?>, PermissionCollection> perms =
            new Hashtable<>(permsMap.size()*2); // no sync; estimate
        perms.putAll(permsMap);

        // Write out serializable fields
        ObjectOutputStream.PutField pfields = out.putFields();

        pfields.put("allPermission", allPermission); // no sync; staleness OK
        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
        // writeObject writes a Hashtable<Class<?>, PermissionCollection> for
        // the perms key, so this cast is safe, unless the data is corrupt.
        @SuppressWarnings("unchecked")
        Hashtable<Class<?>, PermissionCollection> perms =
            (Hashtable<Class<?>, PermissionCollection>)gfields.get("perms", null);
        permsMap = new ConcurrentHashMap<>(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<Permission> {

    // all the perms
    private Iterator<PermissionCollection> perms;
    // the current set
    private Enumeration<Permission> permset;

    PermissionsEnumerator(Iterator<PermissionCollection> 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 Permission 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<Permission> getNextEnumWithMore() {
        while (perms.hasNext()) {
            PermissionCollection pc = perms.next();
            Enumeration<Permission> next =pc.elements();
            if (next.hasMoreElements())
                return next;
        }
        return null;

    }
}


A PermissionsHash stores a homogeneous set of permissions in a hashtable.

Author:Roland Schemers
See Also:
@serialinclude
/**
 * A PermissionsHash stores a homogeneous set of permissions in a hashtable.
 *
 * @see Permission
 * @see Permissions
 *
 *
 * @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.

/**
     * Key and value are (same) permissions objects.
     * Not serialized; see serialization section at end of class.
     */
    private transient ConcurrentHashMap<Permission, Permission> permsMap;

    
Create an empty PermissionsHash object.

/**
     * Create an empty PermissionsHash object.
     */
    PermissionsHash() {
        permsMap = new ConcurrentHashMap<>(11);
    }

    
Adds a permission to the PermissionsHash.

Params:
  • permission – the Permission object to add.
/**
     * Adds a permission to the PermissionsHash.
     *
     * @param permission the Permission object to add.
     */
    @Override
    public void add(Permission permission) {
        permsMap.put(permission, permission);
    }

    
Check and see if this set of permissions implies the permissions
expressed in "permission".

Params:
  • permission – the Permission object to compare
Returns:true if "permission" is a proper subset of a permission in
the set, false if not.
/**
     * 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.
     */
    @Override
    public boolean implies(Permission permission) {
        // attempt a fast lookup and implies. If that fails
        // then enumerate through all the permissions.
        Permission p = permsMap.get(permission);

        // If permission is found, then p.equals(permission)
        if (p == null) {
            for (Permission p_ : permsMap.values()) {
                if (p_.implies(permission))
                    return true;
            }
            return false;
        } else {
            return true;
        }
    }

    
Returns an enumeration of all the Permission objects in the container.

Returns:an enumeration of all the Permissions.
/**
     * Returns an enumeration of all the Permission objects in the container.
     *
     * @return an enumeration of all the Permissions.
     */
    @Override
    public Enumeration<Permission> elements() {
        return permsMap.elements();
    }

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

    
@serialDataDefault fields.
/**
     * @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<Permission, Permission> 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
        // writeObject writes a Hashtable<Class<?>, PermissionCollection> for
        // the perms key, so this cast is safe, unless the data is corrupt.
        @SuppressWarnings("unchecked")
        Hashtable<Permission, Permission> perms =
                (Hashtable<Permission, Permission>)gfields.get("perms", null);
        permsMap = new ConcurrentHashMap<>(perms.size()*2);
        permsMap.putAll(perms);
    }
}