/* * 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) {        assert(!class1.isArray() && !class2.isArray());        if (class1 == class2)            return true;        if (!loadersAreRelated(class1.getClassLoader(), class2.getClassLoader(), false))            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;    }     /** Return the package name for this class.     */    public static String getPackageName(Class<?> cls) {        assert(!cls.isArray());        String name = cls.getName();        int dot = name.lastIndexOf('.');        if (dot < 0)  return "";        return name.substring(0, dot);    }     /**     * 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,                                             boolean loader1MustBeParent) {        if (loader1 == loader2 || loader1 == null                || (loader2 == null && !loader1MustBeParent)) {            return true;        }        for (ClassLoader scan2 = loader2;                scan2 != null; scan2 = scan2.getParent()) {            if (scan2 == loader1)  return true;        }        if (loader1MustBeParent)  return false;        // see if loader2 is a parent of loader1:        for (ClassLoader scan1 = loader1;                scan1 != null; scan1 = scan1.getParent()) {            if (scan1 == loader2)  return true;        }        return false;    }     /**     * Is the class loader of parentClass identical to, or an ancestor of,     * the class loader of childClass?     * @param parentClass     * @param childClass     * @return whether parentClass precedes or equals childClass in class loader order     */    public static boolean classLoaderIsAncestor(Class<?> parentClass, Class<?> childClass) {        return loadersAreRelated(parentClass.getClassLoader(), childClass.getClassLoader(), true);    }}