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Java example source code file (AccessController.java)
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The AccessController.java Java example source code
/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* 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.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.security;
import sun.security.util.Debug;
import sun.reflect.CallerSensitive;
import sun.reflect.Reflection;
/**
* <p> The AccessController class is used for access control operations
* and decisions.
*
* <p> More specifically, the AccessController class is used for
* three purposes:
*
* <ul>
* <li> to decide whether an access to a critical system
* resource is to be allowed or denied, based on the security policy
* currently in effect,
* <li>to mark code as being "privileged", thus affecting subsequent
* access determinations, and
* <li>to obtain a "snapshot" of the current calling context so
* access-control decisions from a different context can be made with
* respect to the saved context. </ul>
*
* <p> The {@link #checkPermission(Permission) checkPermission} method
* determines whether the access request indicated by a specified
* permission should be granted or denied. A sample call appears
* below. In this example, {@code checkPermission} will determine
* whether or not to grant "read" access to the file named "testFile" in
* the "/temp" directory.
*
* <pre>
*
* FilePermission perm = new FilePermission("/temp/testFile", "read");
* AccessController.checkPermission(perm);
*
* </pre>
*
* <p> If a requested access is allowed,
* {@code checkPermission} returns quietly. If denied, an
* AccessControlException is
* thrown. AccessControlException can also be thrown if the requested
* permission is of an incorrect type or contains an invalid value.
* Such information is given whenever possible.
*
* Suppose the current thread traversed m callers, in the order of caller 1
* to caller 2 to caller m. Then caller m invoked the
* {@code checkPermission} method.
* The {@code checkPermission} method determines whether access
* is granted or denied based on the following algorithm:
*
* <pre> {@code
* for (int i = m; i > 0; i--) {
*
* if (caller i's domain does not have the permission)
* throw AccessControlException
*
* else if (caller i is marked as privileged) {
* if (a context was specified in the call to doPrivileged)
* context.checkPermission(permission)
* if (limited permissions were specified in the call to doPrivileged) {
* for (each limited permission) {
* if (the limited permission implies the requested permission)
* return;
* }
* } else
* return;
* }
* }
*
* // Next, check the context inherited when the thread was created.
* // Whenever a new thread is created, the AccessControlContext at
* // that time is stored and associated with the new thread, as the
* // "inherited" context.
*
* inheritedContext.checkPermission(permission);
* }</pre>
*
* <p> A caller can be marked as being "privileged"
* (see {@link #doPrivileged(PrivilegedAction) doPrivileged} and below).
* When making access control decisions, the {@code checkPermission}
* method stops checking if it reaches a caller that
* was marked as "privileged" via a {@code doPrivileged}
* call without a context argument (see below for information about a
* context argument). If that caller's domain has the
* specified permission and at least one limiting permission argument (if any)
* implies the requested permission, no further checking is done and
* {@code checkPermission}
* returns quietly, indicating that the requested access is allowed.
* If that domain does not have the specified permission, an exception
* is thrown, as usual. If the caller's domain had the specified permission
* but it was not implied by any limiting permission arguments given in the call
* to {@code doPrivileged} then the permission checking continues
* until there are no more callers or another {@code doPrivileged}
* call matches the requested permission and returns normally.
*
* <p> The normal use of the "privileged" feature is as follows. If you
* don't need to return a value from within the "privileged" block, do
* the following:
*
* <pre> {@code
* somemethod() {
* ...normal code here...
* AccessController.doPrivileged(new PrivilegedAction<Void>() {
* public Void run() {
* // privileged code goes here, for example:
* System.loadLibrary("awt");
* return null; // nothing to return
* }
* });
* ...normal code here...
* }}</pre>
*
* <p>
* PrivilegedAction is an interface with a single method, named
* {@code run}.
* The above example shows creation of an implementation
* of that interface; a concrete implementation of the
* {@code run} method is supplied.
* When the call to {@code doPrivileged} is made, an
* instance of the PrivilegedAction implementation is passed
* to it. The {@code doPrivileged} method calls the
* {@code run} method from the PrivilegedAction
* implementation after enabling privileges, and returns the
* {@code run} method's return value as the
* {@code doPrivileged} return value (which is
* ignored in this example).
*
* <p> If you need to return a value, you can do something like the following:
*
* <pre> {@code
* somemethod() {
* ...normal code here...
* String user = AccessController.doPrivileged(
* new PrivilegedAction<String>() {
* public String run() {
* return System.getProperty("user.name");
* }
* });
* ...normal code here...
* }}</pre>
*
* <p>If the action performed in your {@code run} method could
* throw a "checked" exception (those listed in the {@code throws} clause
* of a method), then you need to use the
* {@code PrivilegedExceptionAction} interface instead of the
* {@code PrivilegedAction} interface:
*
* <pre> {@code
* somemethod() throws FileNotFoundException {
* ...normal code here...
* try {
* FileInputStream fis = AccessController.doPrivileged(
* new PrivilegedExceptionAction<FileInputStream>() {
* public FileInputStream run() throws FileNotFoundException {
* return new FileInputStream("someFile");
* }
* });
* } catch (PrivilegedActionException e) {
* // e.getException() should be an instance of FileNotFoundException,
* // as only "checked" exceptions will be "wrapped" in a
* // PrivilegedActionException.
* throw (FileNotFoundException) e.getException();
* }
* ...normal code here...
* }}</pre>
*
* <p> Be *very* careful in your use of the "privileged" construct, and
* always remember to make the privileged code section as small as possible.
* You can pass {@code Permission} arguments to further limit the
* scope of the "privilege" (see below).
*
*
* <p> Note that {@code checkPermission} always performs security checks
* within the context of the currently executing thread.
* Sometimes a security check that should be made within a given context
* will actually need to be done from within a
* <i>different context (for example, from within a worker thread).
* The {@link #getContext() getContext} method and
* AccessControlContext class are provided
* for this situation. The {@code getContext} method takes a "snapshot"
* of the current calling context, and places
* it in an AccessControlContext object, which it returns. A sample call is
* the following:
*
* <pre>
*
* AccessControlContext acc = AccessController.getContext()
*
* </pre>
*
* <p>
* AccessControlContext itself has a {@code checkPermission} method
* that makes access decisions based on the context <i>it encapsulates,
* rather than that of the current execution thread.
* Code within a different context can thus call that method on the
* previously-saved AccessControlContext object. A sample call is the
* following:
*
* <pre>
*
* acc.checkPermission(permission)
*
* </pre>
*
* <p> There are also times where you don't know a priori which permissions
* to check the context against. In these cases you can use the
* doPrivileged method that takes a context. You can also limit the scope
* of the privileged code by passing additional {@code Permission}
* parameters.
*
* <pre> {@code
* somemethod() {
* AccessController.doPrivileged(new PrivilegedAction<Object>() {
* public Object run() {
* // Code goes here. Any permission checks within this
* // run method will require that the intersection of the
* // caller's protection domain and the snapshot's
* // context have the desired permission. If a requested
* // permission is not implied by the limiting FilePermission
* // argument then checking of the thread continues beyond the
* // caller of doPrivileged.
* }
* }, acc, new FilePermission("/temp/*", read));
* ...normal code here...
* }}</pre>
* <p> Passing a limiting {@code Permission} argument of an instance of
* {@code AllPermission} is equivalent to calling the equivalent
* {@code doPrivileged} method without limiting {@code Permission}
* arguments. Passing a zero length array of {@code Permission} disables
* the code privileges so that checking always continues beyond the caller of
* that {@code doPrivileged} method.
*
* @see AccessControlContext
*
* @author Li Gong
* @author Roland Schemers
*/
public final class AccessController {
/**
* Don't allow anyone to instantiate an AccessController
*/
private AccessController() { }
/**
* Performs the specified {@code PrivilegedAction} with privileges
* enabled. The action is performed with <i>all of the permissions
* possessed by the caller's protection domain.
*
* <p> If the action's {@code run} method throws an (unchecked)
* exception, it will propagate through this method.
*
* <p> Note that any DomainCombiner associated with the current
* AccessControlContext will be ignored while the action is performed.
*
* @param <T> the type of the value returned by the PrivilegedAction's
* {@code run} method.
*
* @param action the action to be performed.
*
* @return the value returned by the action's {@code run} method.
*
* @exception NullPointerException if the action is {@code null}
*
* @see #doPrivileged(PrivilegedAction,AccessControlContext)
* @see #doPrivileged(PrivilegedExceptionAction)
* @see #doPrivilegedWithCombiner(PrivilegedAction)
* @see java.security.DomainCombiner
*/
@CallerSensitive
public static native <T> T doPrivileged(PrivilegedAction action);
/**
* Performs the specified {@code PrivilegedAction} with privileges
* enabled. The action is performed with <i>all of the permissions
* possessed by the caller's protection domain.
*
* <p> If the action's {@code run} method throws an (unchecked)
* exception, it will propagate through this method.
*
* <p> This method preserves the current AccessControlContext's
* DomainCombiner (which may be null) while the action is performed.
*
* @param <T> the type of the value returned by the PrivilegedAction's
* {@code run} method.
*
* @param action the action to be performed.
*
* @return the value returned by the action's {@code run} method.
*
* @exception NullPointerException if the action is {@code null}
*
* @see #doPrivileged(PrivilegedAction)
* @see java.security.DomainCombiner
*
* @since 1.6
*/
@CallerSensitive
public static <T> T doPrivilegedWithCombiner(PrivilegedAction action) {
AccessControlContext acc = getStackAccessControlContext();
if (acc == null) {
return AccessController.doPrivileged(action);
}
DomainCombiner dc = acc.getAssignedCombiner();
return AccessController.doPrivileged(action,
preserveCombiner(dc, Reflection.getCallerClass()));
}
/**
* Performs the specified {@code PrivilegedAction} with privileges
* enabled and restricted by the specified {@code AccessControlContext}.
* The action is performed with the intersection of the permissions
* possessed by the caller's protection domain, and those possessed
* by the domains represented by the specified {@code AccessControlContext}.
* <p>
* If the action's {@code run} method throws an (unchecked) exception,
* it will propagate through this method.
* <p>
* If a security manager is installed and the specified
* {@code AccessControlContext} was not created by system code and the
* caller's {@code ProtectionDomain} has not been granted the
* {@literal "createAccessControlContext"}
* {@link java.security.SecurityPermission}, then the action is performed
* with no permissions.
*
* @param <T> the type of the value returned by the PrivilegedAction's
* {@code run} method.
* @param action the action to be performed.
* @param context an <i>access control context
* representing the restriction to be applied to the
* caller's domain's privileges before performing
* the specified action. If the context is
* {@code null}, then no additional restriction is applied.
*
* @return the value returned by the action's {@code run} method.
*
* @exception NullPointerException if the action is {@code null}
*
* @see #doPrivileged(PrivilegedAction)
* @see #doPrivileged(PrivilegedExceptionAction,AccessControlContext)
*/
@CallerSensitive
public static native <T> T doPrivileged(PrivilegedAction action,
AccessControlContext context);
/**
* Performs the specified {@code PrivilegedAction} with privileges
* enabled and restricted by the specified
* {@code AccessControlContext} and with a privilege scope limited
* by specified {@code Permission} arguments.
*
* The action is performed with the intersection of the permissions
* possessed by the caller's protection domain, and those possessed
* by the domains represented by the specified
* {@code AccessControlContext}.
* <p>
* If the action's {@code run} method throws an (unchecked) exception,
* it will propagate through this method.
* <p>
* If a security manager is installed and the specified
* {@code AccessControlContext} was not created by system code and the
* caller's {@code ProtectionDomain} has not been granted the
* {@literal "createAccessControlContext"}
* {@link java.security.SecurityPermission}, then the action is performed
* with no permissions.
*
* @param <T> the type of the value returned by the PrivilegedAction's
* {@code run} method.
* @param action the action to be performed.
* @param context an <i>access control context
* representing the restriction to be applied to the
* caller's domain's privileges before performing
* the specified action. If the context is
* {@code null},
* then no additional restriction is applied.
* @param perms the {@code Permission} arguments which limit the
* scope of the caller's privileges. The number of arguments
* is variable.
*
* @return the value returned by the action's {@code run} method.
*
* @throws NullPointerException if action or perms or any element of
* perms is {@code null}
*
* @see #doPrivileged(PrivilegedAction)
* @see #doPrivileged(PrivilegedExceptionAction,AccessControlContext)
*
* @since 1.8
*/
@CallerSensitive
public static <T> T doPrivileged(PrivilegedAction action,
AccessControlContext context, Permission... perms) {
AccessControlContext parent = getContext();
if (perms == null) {
throw new NullPointerException("null permissions parameter");
}
Class <?> caller = Reflection.getCallerClass();
return AccessController.doPrivileged(action, createWrapper(null,
caller, parent, context, perms));
}
/**
* Performs the specified {@code PrivilegedAction} with privileges
* enabled and restricted by the specified
* {@code AccessControlContext} and with a privilege scope limited
* by specified {@code Permission} arguments.
*
* The action is performed with the intersection of the permissions
* possessed by the caller's protection domain, and those possessed
* by the domains represented by the specified
* {@code AccessControlContext}.
* <p>
* If the action's {@code run} method throws an (unchecked) exception,
* it will propagate through this method.
*
* <p> This method preserves the current AccessControlContext's
* DomainCombiner (which may be null) while the action is performed.
* <p>
* If a security manager is installed and the specified
* {@code AccessControlContext} was not created by system code and the
* caller's {@code ProtectionDomain} has not been granted the
* {@literal "createAccessControlContext"}
* {@link java.security.SecurityPermission}, then the action is performed
* with no permissions.
*
* @param <T> the type of the value returned by the PrivilegedAction's
* {@code run} method.
* @param action the action to be performed.
* @param context an <i>access control context
* representing the restriction to be applied to the
* caller's domain's privileges before performing
* the specified action. If the context is
* {@code null},
* then no additional restriction is applied.
* @param perms the {@code Permission} arguments which limit the
* scope of the caller's privileges. The number of arguments
* is variable.
*
* @return the value returned by the action's {@code run} method.
*
* @throws NullPointerException if action or perms or any element of
* perms is {@code null}
*
* @see #doPrivileged(PrivilegedAction)
* @see #doPrivileged(PrivilegedExceptionAction,AccessControlContext)
* @see java.security.DomainCombiner
*
* @since 1.8
*/
@CallerSensitive
public static <T> T doPrivilegedWithCombiner(PrivilegedAction action,
AccessControlContext context, Permission... perms) {
AccessControlContext parent = getContext();
DomainCombiner dc = parent.getCombiner();
if (dc == null && context != null) {
dc = context.getCombiner();
}
if (perms == null) {
throw new NullPointerException("null permissions parameter");
}
Class <?> caller = Reflection.getCallerClass();
return AccessController.doPrivileged(action, createWrapper(dc, caller,
parent, context, perms));
}
/**
* Performs the specified {@code PrivilegedExceptionAction} with
* privileges enabled. The action is performed with <i>all of the
* permissions possessed by the caller's protection domain.
*
* <p> If the action's {@code run} method throws an unchecked
* exception, it will propagate through this method.
*
* <p> Note that any DomainCombiner associated with the current
* AccessControlContext will be ignored while the action is performed.
*
* @param <T> the type of the value returned by the
* PrivilegedExceptionAction's {@code run} method.
*
* @param action the action to be performed
*
* @return the value returned by the action's {@code run} method
*
* @exception PrivilegedActionException if the specified action's
* {@code run} method threw a <i>checked exception
* @exception NullPointerException if the action is {@code null}
*
* @see #doPrivileged(PrivilegedAction)
* @see #doPrivileged(PrivilegedExceptionAction,AccessControlContext)
* @see #doPrivilegedWithCombiner(PrivilegedExceptionAction)
* @see java.security.DomainCombiner
*/
@CallerSensitive
public static native <T> T
doPrivileged(PrivilegedExceptionAction<T> action)
throws PrivilegedActionException;
/**
* Performs the specified {@code PrivilegedExceptionAction} with
* privileges enabled. The action is performed with <i>all of the
* permissions possessed by the caller's protection domain.
*
* <p> If the action's {@code run} method throws an unchecked
* exception, it will propagate through this method.
*
* <p> This method preserves the current AccessControlContext's
* DomainCombiner (which may be null) while the action is performed.
*
* @param <T> the type of the value returned by the
* PrivilegedExceptionAction's {@code run} method.
*
* @param action the action to be performed.
*
* @return the value returned by the action's {@code run} method
*
* @exception PrivilegedActionException if the specified action's
* {@code run} method threw a <i>checked exception
* @exception NullPointerException if the action is {@code null}
*
* @see #doPrivileged(PrivilegedAction)
* @see #doPrivileged(PrivilegedExceptionAction,AccessControlContext)
* @see java.security.DomainCombiner
*
* @since 1.6
*/
@CallerSensitive
public static <T> T doPrivilegedWithCombiner(PrivilegedExceptionAction action)
throws PrivilegedActionException
{
AccessControlContext acc = getStackAccessControlContext();
if (acc == null) {
return AccessController.doPrivileged(action);
}
DomainCombiner dc = acc.getAssignedCombiner();
return AccessController.doPrivileged(action,
preserveCombiner(dc, Reflection.getCallerClass()));
}
/**
* preserve the combiner across the doPrivileged call
*/
private static AccessControlContext preserveCombiner(DomainCombiner combiner,
Class<?> caller)
{
return createWrapper(combiner, caller, null, null, null);
}
/**
* Create a wrapper to contain the limited privilege scope data.
*/
private static AccessControlContext
createWrapper(DomainCombiner combiner, Class<?> caller,
AccessControlContext parent, AccessControlContext context,
Permission[] perms)
{
ProtectionDomain callerPD = getCallerPD(caller);
// check if caller is authorized to create context
if (context != null && !context.isAuthorized() &&
System.getSecurityManager() != null &&
!callerPD.impliesCreateAccessControlContext())
{
ProtectionDomain nullPD = new ProtectionDomain(null, null);
return new AccessControlContext(new ProtectionDomain[] { nullPD });
} else {
return new AccessControlContext(callerPD, combiner, parent,
context, perms);
}
}
private static ProtectionDomain getCallerPD(final Class <?> caller) {
ProtectionDomain callerPd = doPrivileged
(new PrivilegedAction<ProtectionDomain>() {
public ProtectionDomain run() {
return caller.getProtectionDomain();
}
});
return callerPd;
}
/**
* Performs the specified {@code PrivilegedExceptionAction} with
* privileges enabled and restricted by the specified
* {@code AccessControlContext}. The action is performed with the
* intersection of the permissions possessed by the caller's
* protection domain, and those possessed by the domains represented by the
* specified {@code AccessControlContext}.
* <p>
* If the action's {@code run} method throws an <i>unchecked
* exception, it will propagate through this method.
* <p>
* If a security manager is installed and the specified
* {@code AccessControlContext} was not created by system code and the
* caller's {@code ProtectionDomain} has not been granted the
* {@literal "createAccessControlContext"}
* {@link java.security.SecurityPermission}, then the action is performed
* with no permissions.
*
* @param <T> the type of the value returned by the
* PrivilegedExceptionAction's {@code run} method.
* @param action the action to be performed
* @param context an <i>access control context
* representing the restriction to be applied to the
* caller's domain's privileges before performing
* the specified action. If the context is
* {@code null}, then no additional restriction is applied.
*
* @return the value returned by the action's {@code run} method
*
* @exception PrivilegedActionException if the specified action's
* {@code run} method threw a <i>checked exception
* @exception NullPointerException if the action is {@code null}
*
* @see #doPrivileged(PrivilegedAction)
* @see #doPrivileged(PrivilegedAction,AccessControlContext)
*/
@CallerSensitive
public static native <T> T
doPrivileged(PrivilegedExceptionAction<T> action,
AccessControlContext context)
throws PrivilegedActionException;
/**
* Performs the specified {@code PrivilegedExceptionAction} with
* privileges enabled and restricted by the specified
* {@code AccessControlContext} and with a privilege scope limited by
* specified {@code Permission} arguments.
*
* The action is performed with the intersection of the permissions
* possessed by the caller's protection domain, and those possessed
* by the domains represented by the specified
* {@code AccessControlContext}.
* <p>
* If the action's {@code run} method throws an (unchecked) exception,
* it will propagate through this method.
* <p>
* If a security manager is installed and the specified
* {@code AccessControlContext} was not created by system code and the
* caller's {@code ProtectionDomain} has not been granted the
* {@literal "createAccessControlContext"}
* {@link java.security.SecurityPermission}, then the action is performed
* with no permissions.
*
* @param <T> the type of the value returned by the
* PrivilegedExceptionAction's {@code run} method.
* @param action the action to be performed.
* @param context an <i>access control context
* representing the restriction to be applied to the
* caller's domain's privileges before performing
* the specified action. If the context is
* {@code null},
* then no additional restriction is applied.
* @param perms the {@code Permission} arguments which limit the
* scope of the caller's privileges. The number of arguments
* is variable.
*
* @return the value returned by the action's {@code run} method.
*
* @throws PrivilegedActionException if the specified action's
* {@code run} method threw a <i>checked exception
* @throws NullPointerException if action or perms or any element of
* perms is {@code null}
*
* @see #doPrivileged(PrivilegedAction)
* @see #doPrivileged(PrivilegedAction,AccessControlContext)
*
* @since 1.8
*/
@CallerSensitive
public static <T> T doPrivileged(PrivilegedExceptionAction action,
AccessControlContext context, Permission... perms)
throws PrivilegedActionException
{
AccessControlContext parent = getContext();
if (perms == null) {
throw new NullPointerException("null permissions parameter");
}
Class <?> caller = Reflection.getCallerClass();
return AccessController.doPrivileged(action, createWrapper(null, caller, parent, context, perms));
}
/**
* Performs the specified {@code PrivilegedExceptionAction} with
* privileges enabled and restricted by the specified
* {@code AccessControlContext} and with a privilege scope limited by
* specified {@code Permission} arguments.
*
* The action is performed with the intersection of the permissions
* possessed by the caller's protection domain, and those possessed
* by the domains represented by the specified
* {@code AccessControlContext}.
* <p>
* If the action's {@code run} method throws an (unchecked) exception,
* it will propagate through this method.
*
* <p> This method preserves the current AccessControlContext's
* DomainCombiner (which may be null) while the action is performed.
* <p>
* If a security manager is installed and the specified
* {@code AccessControlContext} was not created by system code and the
* caller's {@code ProtectionDomain} has not been granted the
* {@literal "createAccessControlContext"}
* {@link java.security.SecurityPermission}, then the action is performed
* with no permissions.
*
* @param <T> the type of the value returned by the
* PrivilegedExceptionAction's {@code run} method.
* @param action the action to be performed.
* @param context an <i>access control context
* representing the restriction to be applied to the
* caller's domain's privileges before performing
* the specified action. If the context is
* {@code null},
* then no additional restriction is applied.
* @param perms the {@code Permission} arguments which limit the
* scope of the caller's privileges. The number of arguments
* is variable.
*
* @return the value returned by the action's {@code run} method.
*
* @throws PrivilegedActionException if the specified action's
* {@code run} method threw a <i>checked exception
* @throws NullPointerException if action or perms or any element of
* perms is {@code null}
*
* @see #doPrivileged(PrivilegedAction)
* @see #doPrivileged(PrivilegedAction,AccessControlContext)
* @see java.security.DomainCombiner
*
* @since 1.8
*/
@CallerSensitive
public static <T> T doPrivilegedWithCombiner(PrivilegedExceptionAction action,
AccessControlContext context,
Permission... perms)
throws PrivilegedActionException
{
AccessControlContext parent = getContext();
DomainCombiner dc = parent.getCombiner();
if (dc == null && context != null) {
dc = context.getCombiner();
}
if (perms == null) {
throw new NullPointerException("null permissions parameter");
}
Class <?> caller = Reflection.getCallerClass();
return AccessController.doPrivileged(action, createWrapper(dc, caller,
parent, context, perms));
}
/**
* Returns the AccessControl context. i.e., it gets
* the protection domains of all the callers on the stack,
* starting at the first class with a non-null
* ProtectionDomain.
*
* @return the access control context based on the current stack or
* null if there was only privileged system code.
*/
private static native AccessControlContext getStackAccessControlContext();
/**
* Returns the "inherited" AccessControl context. This is the context
* that existed when the thread was created. Package private so
* AccessControlContext can use it.
*/
static native AccessControlContext getInheritedAccessControlContext();
/**
* This method takes a "snapshot" of the current calling context, which
* includes the current Thread's inherited AccessControlContext and any
* limited privilege scope, and places it in an AccessControlContext object.
* This context may then be checked at a later point, possibly in another thread.
*
* @see AccessControlContext
*
* @return the AccessControlContext based on the current context.
*/
public static AccessControlContext getContext()
{
AccessControlContext acc = getStackAccessControlContext();
if (acc == null) {
// all we had was privileged system code. We don't want
// to return null though, so we construct a real ACC.
return new AccessControlContext(null, true);
} else {
return acc.optimize();
}
}
/**
* Determines whether the access request indicated by the
* specified permission should be allowed or denied, based on
* the current AccessControlContext and security policy.
* This method quietly returns if the access request
* is permitted, or throws an AccessControlException otherwise. The
* getPermission method of the AccessControlException returns the
* {@code perm} Permission object instance.
*
* @param perm the requested permission.
*
* @exception AccessControlException if the specified permission
* is not permitted, based on the current security policy.
* @exception NullPointerException if the specified permission
* is {@code null} and is checked based on the
* security policy currently in effect.
*/
public static void checkPermission(Permission perm)
throws AccessControlException
{
//System.err.println("checkPermission "+perm);
//Thread.currentThread().dumpStack();
if (perm == null) {
throw new NullPointerException("permission can't be null");
}
AccessControlContext stack = getStackAccessControlContext();
// if context is null, we had privileged system code on the stack.
if (stack == null) {
Debug debug = AccessControlContext.getDebug();
boolean dumpDebug = false;
if (debug != null) {
dumpDebug = !Debug.isOn("codebase=");
dumpDebug &= !Debug.isOn("permission=") ||
Debug.isOn("permission=" + perm.getClass().getCanonicalName());
}
if (dumpDebug && Debug.isOn("stack")) {
Thread.dumpStack();
}
if (dumpDebug && Debug.isOn("domain")) {
debug.println("domain (context is null)");
}
if (dumpDebug) {
debug.println("access allowed "+perm);
}
return;
}
AccessControlContext acc = stack.optimize();
acc.checkPermission(perm);
}
}
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