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/*
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* Copyright (c) 1997, 2007, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.security;
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import sun.security.util.Debug;
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/**
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* <p> The AccessController class is used for access control operations
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* and decisions.
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*
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* <p> More specifically, the AccessController class is used for
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* three purposes:
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*
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* <ul>
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* <li> to decide whether an access to a critical system
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* resource is to be allowed or denied, based on the security policy
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* currently in effect,<p>
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* <li>to mark code as being "privileged", thus affecting subsequent
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* access determinations, and<p>
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* <li>to obtain a "snapshot" of the current calling context so
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* access-control decisions from a different context can be made with
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* respect to the saved context. </ul>
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*
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* <p> The {@link #checkPermission(Permission) checkPermission} method
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* determines whether the access request indicated by a specified
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* permission should be granted or denied. A sample call appears
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* below. In this example, <code>checkPermission</code> will determine
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* whether or not to grant "read" access to the file named "testFile" in
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* the "/temp" directory.
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*
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* <pre>
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*
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* FilePermission perm = new FilePermission("/temp/testFile", "read");
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* AccessController.checkPermission(perm);
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*
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* </pre>
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*
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* <p> If a requested access is allowed,
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* <code>checkPermission</code> returns quietly. If denied, an
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* AccessControlException is
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* thrown. AccessControlException can also be thrown if the requested
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* permission is of an incorrect type or contains an invalid value.
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* Such information is given whenever possible.
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*
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* Suppose the current thread traversed m callers, in the order of caller 1
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* to caller 2 to caller m. Then caller m invoked the
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* <code>checkPermission</code> method.
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* The <code>checkPermission </code>method determines whether access
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* is granted or denied based on the following algorithm:
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*
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* <pre> {@code
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* for (int i = m; i > 0; i--) {
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*
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* if (caller i's domain does not have the permission)
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* throw AccessControlException
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*
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* else if (caller i is marked as privileged) {
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* if (a context was specified in the call to doPrivileged)
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* context.checkPermission(permission)
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* return;
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* }
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* };
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*
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* // Next, check the context inherited when the thread was created.
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* // Whenever a new thread is created, the AccessControlContext at
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* // that time is stored and associated with the new thread, as the
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* // "inherited" context.
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*
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* inheritedContext.checkPermission(permission);
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* }</pre>
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*
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* <p> A caller can be marked as being "privileged"
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* (see {@link #doPrivileged(PrivilegedAction) doPrivileged} and below).
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* When making access control decisions, the <code>checkPermission</code>
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* method stops checking if it reaches a caller that
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* was marked as "privileged" via a <code>doPrivileged</code>
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* call without a context argument (see below for information about a
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* context argument). If that caller's domain has the
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* specified permission, no further checking is done and
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* <code>checkPermission</code>
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* returns quietly, indicating that the requested access is allowed.
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* If that domain does not have the specified permission, an exception
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* is thrown, as usual.
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*
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* <p> The normal use of the "privileged" feature is as follows. If you
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* don't need to return a value from within the "privileged" block, do
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* the following:
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*
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* <pre> {@code
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* somemethod() {
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* ...normal code here...
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* AccessController.doPrivileged(new PrivilegedAction<Void>() {
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* public Void run() {
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* // privileged code goes here, for example:
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* System.loadLibrary("awt");
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* return null; // nothing to return
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* }
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* });
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* ...normal code here...
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* }}</pre>
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*
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* <p>
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* PrivilegedAction is an interface with a single method, named
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* <code>run</code>.
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* The above example shows creation of an implementation
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* of that interface; a concrete implementation of the
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* <code>run</code> method is supplied.
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* When the call to <code>doPrivileged</code> is made, an
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* instance of the PrivilegedAction implementation is passed
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* to it. The <code>doPrivileged</code> method calls the
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* <code>run</code> method from the PrivilegedAction
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* implementation after enabling privileges, and returns the
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* <code>run</code> method's return value as the
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* <code>doPrivileged</code> return value (which is
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* ignored in this example).
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*
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* <p> If you need to return a value, you can do something like the following:
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*
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* <pre> {@code
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* somemethod() {
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* ...normal code here...
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* String user = AccessController.doPrivileged(
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* new PrivilegedAction<String>() {
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* public String run() {
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* return System.getProperty("user.name");
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* }
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* });
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* ...normal code here...
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* }}</pre>
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*
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* <p>If the action performed in your <code>run</code> method could
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* throw a "checked" exception (those listed in the <code>throws</code> clause
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* of a method), then you need to use the
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* <code>PrivilegedExceptionAction</code> interface instead of the
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* <code>PrivilegedAction</code> interface:
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*
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* <pre> {@code
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* somemethod() throws FileNotFoundException {
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* ...normal code here...
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* try {
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* FileInputStream fis = AccessController.doPrivileged(
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* new PrivilegedExceptionAction<FileInputStream>() {
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* public FileInputStream run() throws FileNotFoundException {
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* return new FileInputStream("someFile");
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* }
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* });
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* } catch (PrivilegedActionException e) {
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* // e.getException() should be an instance of FileNotFoundException,
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* // as only "checked" exceptions will be "wrapped" in a
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* // PrivilegedActionException.
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* throw (FileNotFoundException) e.getException();
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* }
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* ...normal code here...
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* }}</pre>
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*
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* <p> Be *very* careful in your use of the "privileged" construct, and
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* always remember to make the privileged code section as small as possible.
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*
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* <p> Note that <code>checkPermission</code> always performs security checks
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* within the context of the currently executing thread.
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* Sometimes a security check that should be made within a given context
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* will actually need to be done from within a
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* <i>different</i> context (for example, from within a worker thread).
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* The {@link #getContext() getContext} method and
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* AccessControlContext class are provided
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* for this situation. The <code>getContext</code> method takes a "snapshot"
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* of the current calling context, and places
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* it in an AccessControlContext object, which it returns. A sample call is
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* the following:
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*
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* <pre>
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*
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* AccessControlContext acc = AccessController.getContext()
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*
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* </pre>
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*
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* <p>
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* AccessControlContext itself has a <code>checkPermission</code> method
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* that makes access decisions based on the context <i>it</i> encapsulates,
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* rather than that of the current execution thread.
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* Code within a different context can thus call that method on the
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* previously-saved AccessControlContext object. A sample call is the
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* following:
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*
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* <pre>
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*
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* acc.checkPermission(permission)
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*
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* </pre>
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*
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* <p> There are also times where you don't know a priori which permissions
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* to check the context against. In these cases you can use the
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* doPrivileged method that takes a context:
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*
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* <pre> {@code
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* somemethod() {
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* AccessController.doPrivileged(new PrivilegedAction<Object>() {
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* public Object run() {
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* // Code goes here. Any permission checks within this
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* // run method will require that the intersection of the
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* // callers protection domain and the snapshot's
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* // context have the desired permission.
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* }
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* }, acc);
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* ...normal code here...
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* }}</pre>
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*
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* @see AccessControlContext
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*
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* @author Li Gong
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* @author Roland Schemers
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*/
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public final class AccessController {
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/**
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* Don't allow anyone to instantiate an AccessController
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*/
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private AccessController() { }
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/**
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* Performs the specified <code>PrivilegedAction</code> with privileges
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* enabled. The action is performed with <i>all</i> of the permissions
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* possessed by the caller's protection domain.
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*
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* <p> If the action's <code>run</code> method throws an (unchecked)
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* exception, it will propagate through this method.
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*
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* <p> Note that any DomainCombiner associated with the current
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* AccessControlContext will be ignored while the action is performed.
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*
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* @param action the action to be performed.
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*
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* @return the value returned by the action's <code>run</code> method.
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*
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* @exception NullPointerException if the action is <code>null</code>
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*
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* @see #doPrivileged(PrivilegedAction,AccessControlContext)
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* @see #doPrivileged(PrivilegedExceptionAction)
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* @see #doPrivilegedWithCombiner(PrivilegedAction)
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* @see java.security.DomainCombiner
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*/
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public static native <T> T doPrivileged(PrivilegedAction<T> action);
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/**
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* Performs the specified <code>PrivilegedAction</code> with privileges
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* enabled. The action is performed with <i>all</i> of the permissions
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* possessed by the caller's protection domain.
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*
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* <p> If the action's <code>run</code> method throws an (unchecked)
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* exception, it will propagate through this method.
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*
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* <p> This method preserves the current AccessControlContext's
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* DomainCombiner (which may be null) while the action is performed.
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*
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* @param action the action to be performed.
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*
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* @return the value returned by the action's <code>run</code> method.
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*
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* @exception NullPointerException if the action is <code>null</code>
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*
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* @see #doPrivileged(PrivilegedAction)
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* @see java.security.DomainCombiner
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*
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* @since 1.6
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*/
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public static <T> T doPrivilegedWithCombiner(PrivilegedAction<T> action) {
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DomainCombiner dc = null;
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AccessControlContext acc = getStackAccessControlContext();
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if (acc == null || (dc = acc.getAssignedCombiner()) == null) {
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return AccessController.doPrivileged(action);
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}
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return AccessController.doPrivileged(action, preserveCombiner(dc));
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}
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/**
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* Performs the specified <code>PrivilegedAction</code> with privileges
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* enabled and restricted by the specified
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* <code>AccessControlContext</code>.
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* The action is performed with the intersection of the permissions
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* possessed by the caller's protection domain, and those possessed
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* by the domains represented by the specified
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* <code>AccessControlContext</code>.
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* <p>
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* If the action's <code>run</code> method throws an (unchecked) exception,
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* it will propagate through this method.
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*
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* @param action the action to be performed.
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* @param context an <i>access control context</i>
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* representing the restriction to be applied to the
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* caller's domain's privileges before performing
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* the specified action. If the context is
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* <code>null</code>,
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* then no additional restriction is applied.
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*
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* @return the value returned by the action's <code>run</code> method.
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*
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* @exception NullPointerException if the action is <code>null</code>
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*
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* @see #doPrivileged(PrivilegedAction)
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* @see #doPrivileged(PrivilegedExceptionAction,AccessControlContext)
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*/
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public static native <T> T doPrivileged(PrivilegedAction<T> action,
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AccessControlContext context);
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/**
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* Performs the specified <code>PrivilegedExceptionAction</code> with
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* privileges enabled. The action is performed with <i>all</i> of the
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* permissions possessed by the caller's protection domain.
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*
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* <p> If the action's <code>run</code> method throws an <i>unchecked</i>
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* exception, it will propagate through this method.
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*
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* <p> Note that any DomainCombiner associated with the current
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* AccessControlContext will be ignored while the action is performed.
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*
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* @param action the action to be performed
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*
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* @return the value returned by the action's <code>run</code> method
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*
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* @exception PrivilegedActionException if the specified action's
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* <code>run</code> method threw a <i>checked</i> exception
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* @exception NullPointerException if the action is <code>null</code>
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*
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* @see #doPrivileged(PrivilegedAction)
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* @see #doPrivileged(PrivilegedExceptionAction,AccessControlContext)
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* @see #doPrivilegedWithCombiner(PrivilegedExceptionAction)
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* @see java.security.DomainCombiner
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*/
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public static native <T> T
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doPrivileged(PrivilegedExceptionAction<T> action)
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throws PrivilegedActionException;
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/**
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* Performs the specified <code>PrivilegedExceptionAction</code> with
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* privileges enabled. The action is performed with <i>all</i> of the
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* permissions possessed by the caller's protection domain.
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*
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* <p> If the action's <code>run</code> method throws an <i>unchecked</i>
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* exception, it will propagate through this method.
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*
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* <p> This method preserves the current AccessControlContext's
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* DomainCombiner (which may be null) while the action is performed.
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*
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* @param action the action to be performed.
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*
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* @return the value returned by the action's <code>run</code> method
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*
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* @exception PrivilegedActionException if the specified action's
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* <code>run</code> method threw a <i>checked</i> exception
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* @exception NullPointerException if the action is <code>null</code>
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*
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* @see #doPrivileged(PrivilegedAction)
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* @see #doPrivileged(PrivilegedExceptionAction,AccessControlContext)
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* @see java.security.DomainCombiner
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*
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* @since 1.6
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*/
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public static <T> T doPrivilegedWithCombiner
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(PrivilegedExceptionAction<T> action) throws PrivilegedActionException {
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DomainCombiner dc = null;
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AccessControlContext acc = getStackAccessControlContext();
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|
391 |
if (acc == null || (dc = acc.getAssignedCombiner()) == null) {
|
|
392 |
return AccessController.doPrivileged(action);
|
|
393 |
}
|
|
394 |
return AccessController.doPrivileged(action, preserveCombiner(dc));
|
|
395 |
}
|
|
396 |
|
|
397 |
/**
|
|
398 |
* preserve the combiner across the doPrivileged call
|
|
399 |
*/
|
|
400 |
private static AccessControlContext preserveCombiner
|
|
401 |
(DomainCombiner combiner) {
|
|
402 |
|
|
403 |
/**
|
|
404 |
* callerClass[0] = Reflection.getCallerClass
|
|
405 |
* callerClass[1] = AccessController.preserveCombiner
|
|
406 |
* callerClass[2] = AccessController.doPrivileged
|
|
407 |
* callerClass[3] = caller
|
|
408 |
*/
|
|
409 |
final Class callerClass = sun.reflect.Reflection.getCallerClass(3);
|
|
410 |
ProtectionDomain callerPd = doPrivileged
|
|
411 |
(new PrivilegedAction<ProtectionDomain>() {
|
|
412 |
public ProtectionDomain run() {
|
|
413 |
return callerClass.getProtectionDomain();
|
|
414 |
}
|
|
415 |
});
|
|
416 |
|
|
417 |
// perform 'combine' on the caller of doPrivileged,
|
|
418 |
// even if the caller is from the bootclasspath
|
|
419 |
ProtectionDomain[] pds = new ProtectionDomain[] {callerPd};
|
|
420 |
return new AccessControlContext(combiner.combine(pds, null), combiner);
|
|
421 |
}
|
|
422 |
|
|
423 |
|
|
424 |
/**
|
|
425 |
* Performs the specified <code>PrivilegedExceptionAction</code> with
|
|
426 |
* privileges enabled and restricted by the specified
|
|
427 |
* <code>AccessControlContext</code>. The action is performed with the
|
2589
|
428 |
* intersection of the permissions possessed by the caller's
|
2
|
429 |
* protection domain, and those possessed by the domains represented by the
|
|
430 |
* specified <code>AccessControlContext</code>.
|
|
431 |
* <p>
|
|
432 |
* If the action's <code>run</code> method throws an <i>unchecked</i>
|
|
433 |
* exception, it will propagate through this method.
|
|
434 |
*
|
|
435 |
* @param action the action to be performed
|
|
436 |
* @param context an <i>access control context</i>
|
|
437 |
* representing the restriction to be applied to the
|
|
438 |
* caller's domain's privileges before performing
|
|
439 |
* the specified action. If the context is
|
|
440 |
* <code>null</code>,
|
|
441 |
* then no additional restriction is applied.
|
|
442 |
*
|
|
443 |
* @return the value returned by the action's <code>run</code> method
|
|
444 |
*
|
|
445 |
* @exception PrivilegedActionException if the specified action's
|
|
446 |
* <code>run</code> method
|
|
447 |
* threw a <i>checked</i> exception
|
|
448 |
* @exception NullPointerException if the action is <code>null</code>
|
|
449 |
*
|
|
450 |
* @see #doPrivileged(PrivilegedAction)
|
|
451 |
* @see #doPrivileged(PrivilegedExceptionAction,AccessControlContext)
|
|
452 |
*/
|
|
453 |
public static native <T> T
|
|
454 |
doPrivileged(PrivilegedExceptionAction<T> action,
|
|
455 |
AccessControlContext context)
|
|
456 |
throws PrivilegedActionException;
|
|
457 |
|
|
458 |
/**
|
|
459 |
* Returns the AccessControl context. i.e., it gets
|
|
460 |
* the protection domains of all the callers on the stack,
|
|
461 |
* starting at the first class with a non-null
|
|
462 |
* ProtectionDomain.
|
|
463 |
*
|
|
464 |
* @return the access control context based on the current stack or
|
|
465 |
* null if there was only privileged system code.
|
|
466 |
*/
|
|
467 |
|
|
468 |
private static native AccessControlContext getStackAccessControlContext();
|
|
469 |
|
|
470 |
/**
|
|
471 |
* Returns the "inherited" AccessControl context. This is the context
|
|
472 |
* that existed when the thread was created. Package private so
|
|
473 |
* AccessControlContext can use it.
|
|
474 |
*/
|
|
475 |
|
|
476 |
static native AccessControlContext getInheritedAccessControlContext();
|
|
477 |
|
|
478 |
/**
|
|
479 |
* This method takes a "snapshot" of the current calling context, which
|
|
480 |
* includes the current Thread's inherited AccessControlContext,
|
|
481 |
* and places it in an AccessControlContext object. This context may then
|
|
482 |
* be checked at a later point, possibly in another thread.
|
|
483 |
*
|
|
484 |
* @see AccessControlContext
|
|
485 |
*
|
|
486 |
* @return the AccessControlContext based on the current context.
|
|
487 |
*/
|
|
488 |
|
|
489 |
public static AccessControlContext getContext()
|
|
490 |
{
|
|
491 |
AccessControlContext acc = getStackAccessControlContext();
|
|
492 |
if (acc == null) {
|
|
493 |
// all we had was privileged system code. We don't want
|
|
494 |
// to return null though, so we construct a real ACC.
|
|
495 |
return new AccessControlContext(null, true);
|
|
496 |
} else {
|
|
497 |
return acc.optimize();
|
|
498 |
}
|
|
499 |
}
|
|
500 |
|
|
501 |
/**
|
|
502 |
* Determines whether the access request indicated by the
|
|
503 |
* specified permission should be allowed or denied, based on
|
|
504 |
* the current AccessControlContext and security policy.
|
|
505 |
* This method quietly returns if the access request
|
|
506 |
* is permitted, or throws an AccessControlException otherwise. The
|
|
507 |
* getPermission method of the AccessControlException returns the
|
|
508 |
* <code>perm</code> Permission object instance.
|
|
509 |
*
|
|
510 |
* @param perm the requested permission.
|
|
511 |
*
|
|
512 |
* @exception AccessControlException if the specified permission
|
|
513 |
* is not permitted, based on the current security policy.
|
|
514 |
* @exception NullPointerException if the specified permission
|
|
515 |
* is <code>null</code> and is checked based on the
|
|
516 |
* security policy currently in effect.
|
|
517 |
*/
|
|
518 |
|
|
519 |
public static void checkPermission(Permission perm)
|
|
520 |
throws AccessControlException
|
|
521 |
{
|
|
522 |
//System.err.println("checkPermission "+perm);
|
|
523 |
//Thread.currentThread().dumpStack();
|
|
524 |
|
|
525 |
if (perm == null) {
|
|
526 |
throw new NullPointerException("permission can't be null");
|
|
527 |
}
|
|
528 |
|
|
529 |
AccessControlContext stack = getStackAccessControlContext();
|
|
530 |
// if context is null, we had privileged system code on the stack.
|
|
531 |
if (stack == null) {
|
|
532 |
Debug debug = AccessControlContext.getDebug();
|
|
533 |
boolean dumpDebug = false;
|
|
534 |
if (debug != null) {
|
|
535 |
dumpDebug = !Debug.isOn("codebase=");
|
|
536 |
dumpDebug &= !Debug.isOn("permission=") ||
|
|
537 |
Debug.isOn("permission=" + perm.getClass().getCanonicalName());
|
|
538 |
}
|
|
539 |
|
|
540 |
if (dumpDebug && Debug.isOn("stack")) {
|
|
541 |
Thread.currentThread().dumpStack();
|
|
542 |
}
|
|
543 |
|
|
544 |
if (dumpDebug && Debug.isOn("domain")) {
|
|
545 |
debug.println("domain (context is null)");
|
|
546 |
}
|
|
547 |
|
|
548 |
if (dumpDebug) {
|
|
549 |
debug.println("access allowed "+perm);
|
|
550 |
}
|
|
551 |
return;
|
|
552 |
}
|
|
553 |
|
|
554 |
AccessControlContext acc = stack.optimize();
|
|
555 |
acc.checkPermission(perm);
|
|
556 |
}
|
|
557 |
}
|