--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/sun/invoke/util/VerifyAccess.java Wed Mar 23 23:02:31 2011 -0700
@@ -0,0 +1,210 @@
+/*
+ * Copyright (c) 2008, 2011, Oracle and/or its affiliates. All rights reserved.
+ * 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 sun.invoke.util;
+
+import java.lang.reflect.Modifier;
+import static java.lang.reflect.Modifier.*;
+
+/**
+ * This class centralizes information about the JVM's linkage access control.
+ * @author jrose
+ */
+public class VerifyAccess {
+
+ private VerifyAccess() { } // cannot instantiate
+
+ private static final int PACKAGE_ONLY = 0;
+ private static final int ALL_ACCESS_MODES = (PUBLIC|PRIVATE|PROTECTED|PACKAGE_ONLY);
+ private static final boolean ALLOW_NESTMATE_ACCESS = false;
+
+ /**
+ * Evaluate the JVM linkage rules for access to the given method
+ * on behalf of a caller class which proposes to perform the access.
+ * Return true if the caller class has privileges to invoke a method
+ * or access a field with the given properties.
+ * This requires an accessibility check of the referencing class,
+ * plus an accessibility check of the member within the class,
+ * which depends on the member's modifier flags.
+ * <p>
+ * The relevant properties include the defining class ({@code defc})
+ * of the member, and its modifier flags ({@code mods}).
+ * Also relevant is the class used to make the initial symbolic reference
+ * to the member ({@code refc}). If this latter class is not distinguished,
+ * the defining class should be passed for both arguments ({@code defc == refc}).
+ * <h3>JVM Specification, 5.4.4 "Access Control"</h3>
+ * A field or method R is accessible to a class or interface D if
+ * and only if any of the following conditions is true:<ul>
+ * <li>R is public.
+ * <li>R is protected and is declared in a class C, and D is either
+ * a subclass of C or C itself. Furthermore, if R is not
+ * static, then the symbolic reference to R must contain a
+ * symbolic reference to a class T, such that T is either a
+ * subclass of D, a superclass of D or D itself.
+ * <li>R is either protected or has default access (that is,
+ * neither public nor protected nor private), and is declared
+ * by a class in the same runtime package as D.
+ * <li>R is private and is declared in D.
+ * </ul>
+ * This discussion of access control omits a related restriction
+ * on the target of a protected field access or method invocation
+ * (the target must be of class D or a subtype of D). That
+ * requirement is checked as part of the verification process
+ * (5.4.1); it is not part of link-time access control.
+ * @param refc the class used in the symbolic reference to the proposed member
+ * @param defc the class in which the proposed member is actually defined
+ * @param mods modifier flags for the proposed member
+ * @param lookupClass the class for which the access check is being made
+ * @return true iff the the accessing class can access such a member
+ */
+ public static boolean isMemberAccessible(Class<?> refc, // symbolic ref class
+ Class<?> defc, // actual def class
+ int mods, // actual member mods
+ Class<?> lookupClass) {
+ // Usually refc and defc are the same, but if they differ, verify them both.
+ if (refc != defc) {
+ if (!isClassAccessible(refc, lookupClass)) {
+ // Note that defc is verified in the switch below.
+ return false;
+ }
+ if ((mods & (ALL_ACCESS_MODES|STATIC)) == (PROTECTED|STATIC)) {
+ // Apply the special rules for refc here.
+ if (!isRelatedClass(refc, lookupClass))
+ return isSamePackage(defc, lookupClass);
+ // If refc == defc, the call to isPublicSuperClass will do
+ // the whole job, since in that case refc (as defc) will be
+ // a superclass of the lookup class.
+ }
+ }
+ if (defc == lookupClass)
+ return true; // easy check; all self-access is OK
+ switch (mods & ALL_ACCESS_MODES) {
+ case PUBLIC:
+ if (refc != defc) return true; // already checked above
+ return isClassAccessible(refc, lookupClass);
+ case PROTECTED:
+ return isSamePackage(defc, lookupClass) || isPublicSuperClass(defc, lookupClass);
+ case PACKAGE_ONLY:
+ return isSamePackage(defc, lookupClass);
+ case PRIVATE:
+ // Loosened rules for privates follows access rules for inner classes.
+ return (ALLOW_NESTMATE_ACCESS &&
+ isSamePackageMember(defc, lookupClass));
+ default:
+ throw new IllegalArgumentException("bad modifiers: "+Modifier.toString(mods));
+ }
+ }
+
+ static boolean isRelatedClass(Class<?> refc, Class<?> lookupClass) {
+ return (refc == lookupClass ||
+ refc.isAssignableFrom(lookupClass) ||
+ lookupClass.isAssignableFrom(refc));
+ }
+
+ static boolean isPublicSuperClass(Class<?> defc, Class<?> lookupClass) {
+ return isPublic(defc.getModifiers()) && defc.isAssignableFrom(lookupClass);
+ }
+
+ /**
+ * Evaluate the JVM linkage rules for access to the given class on behalf of caller.
+ * <h3>JVM Specification, 5.4.4 "Access Control"</h3>
+ * A class or interface C is accessible to a class or interface D
+ * if and only if either of the following conditions are true:<ul>
+ * <li>C is public.
+ * <li>C and D are members of the same runtime package.
+ * </ul>
+ * @param refc the symbolic reference class to which access is being checked (C)
+ * @param lookupClass the class performing the lookup (D)
+ */
+ public static boolean isClassAccessible(Class<?> refc, Class<?> lookupClass) {
+ int mods = refc.getModifiers();
+ if (isPublic(mods))
+ return true;
+ if (isSamePackage(lookupClass, refc))
+ return true;
+ return false;
+ }
+
+ /**
+ * Test if two classes have the same class loader and package qualifier.
+ * @param class1
+ * @param class2
+ * @return whether they are in the same package
+ */
+ public static boolean isSamePackage(Class<?> class1, Class<?> class2) {
+ if (class1 == class2)
+ return true;
+ if (!loadersAreRelated(class1.getClassLoader(), class2.getClassLoader()))
+ return false;
+ String name1 = class1.getName(), name2 = class2.getName();
+ int dot = name1.lastIndexOf('.');
+ if (dot != name2.lastIndexOf('.'))
+ return false;
+ for (int i = 0; i < dot; i++) {
+ if (name1.charAt(i) != name2.charAt(i))
+ return false;
+ }
+ return true;
+ }
+
+ /**
+ * Test if two classes are defined as part of the same package member (top-level class).
+ * If this is true, they can share private access with each other.
+ * @param class1
+ * @param class2
+ * @return whether they are identical or nested together
+ */
+ public static boolean isSamePackageMember(Class<?> class1, Class<?> class2) {
+ if (class1 == class2)
+ return true;
+ if (!isSamePackage(class1, class2))
+ return false;
+ if (getOutermostEnclosingClass(class1) != getOutermostEnclosingClass(class2))
+ return false;
+ return true;
+ }
+
+ private static Class<?> getOutermostEnclosingClass(Class<?> c) {
+ Class<?> pkgmem = c;
+ for (Class<?> enc = c; (enc = enc.getEnclosingClass()) != null; )
+ pkgmem = enc;
+ return pkgmem;
+ }
+
+ private static boolean loadersAreRelated(ClassLoader loader1, ClassLoader loader2) {
+ if (loader1 == loader2 || loader1 == null || loader2 == null) {
+ return true;
+ }
+ for (ClassLoader scan1 = loader1;
+ scan1 != null; scan1 = scan1.getParent()) {
+ if (scan1 == loader2) return true;
+ }
+ for (ClassLoader scan2 = loader2;
+ scan2 != null; scan2 = scan2.getParent()) {
+ if (scan2 == loader1) return true;
+ }
+ return false;
+ }
+}