--- /dev/null
+/* VMAccessController.java -- VM-specific access controller methods.
+ Copyright (C) 2004, 2005 Free Software Foundation, Inc.
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+This program 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 for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; see the file COPYING. If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library. Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module. An independent module is a module which is not derived from
+or based on this library. If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so. If you do not wish to do so, delete this
+exception statement from your version. */
+
+
+package java.security;
+
+import java.util.HashSet;
+import java.util.LinkedList;
+
+final class VMAccessController
+{
+
+ // Fields.
+ // -------------------------------------------------------------------------
+
+ /**
+ * This is a per-thread stack of AccessControlContext objects (which can
+ * be null) for each call to AccessController.doPrivileged in each thread's
+ * call stack. We use this to remember which context object corresponds to
+ * which call.
+ */
+ private static final ThreadLocal contexts = new ThreadLocal();
+
+ /**
+ * This is a Boolean that, if set, tells getContext that it has already
+ * been called once, allowing us to handle recursive permission checks
+ * caused by methods getContext calls.
+ */
+ private static final ThreadLocal inGetContext = new ThreadLocal();
+
+ /**
+ * And we return this all-permissive context to ensure that privileged
+ * methods called from getContext succeed.
+ */
+ private static final AccessControlContext DEFAULT_CONTEXT;
+ static
+ {
+ CodeSource source = new CodeSource(null, null);
+ Permissions permissions = new Permissions();
+ permissions.add(new AllPermission());
+ ProtectionDomain[] domain = new ProtectionDomain[] {
+ new ProtectionDomain(source, permissions)
+ };
+ DEFAULT_CONTEXT = new AccessControlContext(domain);
+ }
+
+ private static final boolean DEBUG = gnu.classpath.Configuration.DEBUG;
+ private static void debug(String msg)
+ {
+ System.err.print(">>> VMAccessController: ");
+ System.err.println(msg);
+ }
+
+ // Constructors.
+ // -------------------------------------------------------------------------
+
+ private VMAccessController() { }
+
+ // Class methods.
+ // -------------------------------------------------------------------------
+
+ /**
+ * Relate a class (which should be an instance of {@link PrivilegedAction}
+ * with an access control context. This method is used by {@link
+ * AccessController#doPrivileged(java.security.PrivilegedAction,java.security.AccessControlContext)}
+ * to set up the context that will be returned by {@link #getContext()}.
+ * This method relates the class to the current thread, so contexts
+ * pushed from one thread will not be available to another.
+ *
+ * @param acc The access control context.
+ */
+ static void pushContext (AccessControlContext acc)
+ {
+ if (DEBUG)
+ debug("pushing " + acc);
+ LinkedList stack = (LinkedList) contexts.get();
+ if (stack == null)
+ {
+ if (DEBUG)
+ debug("no stack... creating ");
+ stack = new LinkedList();
+ contexts.set(stack);
+ }
+ stack.addFirst(acc);
+ }
+
+ /**
+ * Removes the relation of a class to an {@link AccessControlContext}.
+ * This method is used by {@link AccessController} when exiting from a
+ * call to {@link
+ * AccessController#doPrivileged(java.security.PrivilegedAction,java.security.AccessControlContext)}.
+ */
+ static void popContext()
+ {
+ if (DEBUG)
+ debug("popping context");
+
+ // Stack should never be null, nor should it be empty, if this method
+ // and its counterpart has been called properly.
+ LinkedList stack = (LinkedList) contexts.get();
+ if (stack != null)
+ {
+ stack.removeFirst();
+ if (stack.isEmpty())
+ contexts.set(null);
+ }
+ else if (DEBUG)
+ {
+ debug("no stack during pop?????");
+ }
+ }
+
+ /**
+ * Examine the method stack of the currently running thread, and create
+ * an {@link AccessControlContext} filled in with the appropriate {@link
+ * ProtectionDomain} objects given this stack.
+ *
+ * @return The context.
+ */
+ static AccessControlContext getContext()
+ {
+ // If we are already in getContext, but called a method that needs
+ // a permission check, return the all-permissive context so methods
+ // called from here succeed.
+ //
+ // XXX is this necessary? We should verify if there are any calls in
+ // the stack below this method that require permission checks.
+ Boolean inCall = (Boolean) inGetContext.get();
+ if (inCall != null && inCall.booleanValue())
+ {
+ if (DEBUG)
+ debug("already in getContext");
+ return DEFAULT_CONTEXT;
+ }
+
+ inGetContext.set(Boolean.TRUE);
+
+ Object[][] stack = getStack();
+ Class[] classes = (Class[]) stack[0];
+ String[] methods = (String[]) stack[1];
+
+ if (DEBUG)
+ debug("got trace of length " + classes.length);
+
+ HashSet domains = new HashSet();
+ HashSet seenDomains = new HashSet();
+ AccessControlContext context = null;
+ int privileged = 0;
+
+ // We walk down the stack, adding each ProtectionDomain for each
+ // class in the call stack. If we reach a call to doPrivileged,
+ // we don't add any more stack frames. We skip the first three stack
+ // frames, since they comprise the calls to getStack, getContext,
+ // and AccessController.getContext.
+ for (int i = 3; i < classes.length && privileged < 2; i++)
+ {
+ Class clazz = classes[i];
+ String method = methods[i];
+
+ if (DEBUG)
+ {
+ debug("checking " + clazz + "." + method);
+ // subject to getClassLoader RuntimePermission
+ debug("loader = " + clazz.getClassLoader());
+ }
+
+ // If the previous frame was a call to doPrivileged, then this is
+ // the last frame we look at.
+ if (privileged == 1)
+ privileged = 2;
+
+ if (clazz.equals (AccessController.class)
+ && method.equals ("doPrivileged"))
+ {
+ // If there was a call to doPrivileged with a supplied context,
+ // return that context. If using JAAS doAs*, it should be
+ // a context with a SubjectDomainCombiner
+ LinkedList l = (LinkedList) contexts.get();
+ if (l != null)
+ context = (AccessControlContext) l.getFirst();
+ privileged = 1;
+ }
+
+ // subject to getProtectionDomain RuntimePermission
+ ProtectionDomain domain = clazz.getProtectionDomain();
+
+ if (domain == null)
+ continue;
+ if (seenDomains.contains(domain))
+ continue;
+ seenDomains.add(domain);
+
+ // Create a static snapshot of this domain, which may change over time
+ // if the current policy changes.
+ domains.add(new ProtectionDomain(domain.getCodeSource(),
+ domain.getPermissions()));
+ }
+
+ if (DEBUG)
+ debug("created domains: " + domains);
+
+ ProtectionDomain[] result = (ProtectionDomain[])
+ domains.toArray(new ProtectionDomain[domains.size()]);
+
+ if (context != null)
+ {
+ DomainCombiner dc = context.getDomainCombiner ();
+ // If the supplied context had no explicit DomainCombiner, use
+ // our private version, which computes the intersection of the
+ // context's domains with the derived set.
+ if (dc == null)
+ context = new AccessControlContext
+ (IntersectingDomainCombiner.SINGLETON.combine
+ (result, context.getProtectionDomains ()));
+ // Use the supplied DomainCombiner. This should be secure,
+ // because only trusted code may create an
+ // AccessControlContext with a custom DomainCombiner.
+ else
+ context = new AccessControlContext (result, context, dc);
+ }
+ // No context was supplied. Return the derived one.
+ else
+ context = new AccessControlContext (result);
+
+ inGetContext.set(Boolean.FALSE);
+ return context;
+ }
+
+ /**
+ * Returns a snapshot of the current call stack as a pair of arrays:
+ * the first an array of classes in the call stack, the second an array
+ * of strings containing the method names in the call stack. The two
+ * arrays match up, meaning that method <i>i</i> is declared in class
+ * <i>i</i>. The arrays are clean; it will only contain Java methods,
+ * and no element of the list should be null.
+ *
+ * <p>The default implementation returns an empty stack, which will be
+ * interpreted as having no permissions whatsoever.
+ *
+ * @return A pair of arrays describing the current call stack. The first
+ * element is an array of Class objects, and the second is an array
+ * of Strings comprising the method names.
+ */
+// private static Object[][] getStack()
+// {
+// return new Object[][] { new Class[0], new String[0] };
+// }
+ private native static Object[][] getStack();
+}
projects / cacao.git / blobdiff