1 /*

     2  * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package sun.dyn.util;

    27 

    28 import java.lang.reflect.Modifier;

    29 import sun.dyn.MemberName;

    30 import sun.dyn.MethodHandleImpl;

    31 import sun.dyn.empty.Empty;

    32 import static java.lang.reflect.Modifier.*;

    33 

    34 /**

    35  * This class centralizes information about the JVM's linkage access control.

    36  * @author jrose

    37  */

    38 public class VerifyAccess {

    39 

    40     private VerifyAccess() { }  // cannot instantiate

    41 

    42     private static final int PACKAGE_ONLY = 0;

    43     private static final int ALL_ACCESS_MODES = (PUBLIC|PRIVATE|PROTECTED|PACKAGE_ONLY);

    44     private static final boolean ALLOW_NESTMATE_ACCESS = false;

    45 

    46     /**

    47      * Evaluate the JVM linkage rules for access to the given method

    48      * on behalf of a caller class which proposes to perform the access.

    49      * Return true if the caller class has privileges to invoke a method

    50      * or access a field with the given properties.

    51      * This requires an accessibility check of the referencing class,

    52      * plus an accessibility check of the member within the class,

    53      * which depends on the member's modifier flags.

    54      * <p>

    55      * The relevant properties include the defining class ({@code defc})

    56      * of the member, and its modifier flags ({@code mods}).

    57      * Also relevant is the class used to make the initial symbolic reference

    58      * to the member ({@code refc}).  If this latter class is not distinguished,

    59      * the defining class should be passed for both arguments ({@code defc == refc}).

    60      * <h3>JVM Specification, 5.4.4 "Access Control"</h3>

    61      * A field or method R is accessible to a class or interface D if

    62      * and only if any of the following conditions is true:<ul>

    63      * <li>R is public.

    64      * <li>R is protected and is declared in a class C, and D is either

    65      *     a subclass of C or C itself.  Furthermore, if R is not

    66      *     static, then the symbolic reference to R must contain a

    67      *     symbolic reference to a class T, such that T is either a

    68      *     subclass of D, a superclass of D or D itself.

    69      * <li>R is either protected or has default access (that is,

    70      *     neither public nor protected nor private), and is declared

    71      *     by a class in the same runtime package as D.

    72      * <li>R is private and is declared in D.

    73      * </ul>

    74      * This discussion of access control omits a related restriction

    75      * on the target of a protected field access or method invocation

    76      * (the target must be of class D or a subtype of D). That

    77      * requirement is checked as part of the verification process

    78      * (5.4.1); it is not part of link-time access control.

    79      * @param refc the class used in the symbolic reference to the proposed member

    80      * @param defc the class in which the proposed member is actually defined

    81      * @param mods modifier flags for the proposed member

    82      * @param lookupClass the class for which the access check is being made

    83      * @return true iff the the accessing class can access such a member

    84      */

    85     public static boolean isMemberAccessible(Class<?> refc,  // symbolic ref class

    86                                              Class<?> defc,  // actual def class

    87                                              int      mods,  // actual member mods

    88                                              Class<?> lookupClass) {

    89         // Usually refc and defc are the same, but if they differ, verify them both.

    90         if (refc != defc) {

    91             if (!isClassAccessible(refc, lookupClass)) {

    92                 // Note that defc is verified in the switch below.

    93                 return false;

    94             }

    95             if ((mods & (ALL_ACCESS_MODES|STATIC)) == (PROTECTED|STATIC)) {

    96                 // Apply the special rules for refc here.

    97                 if (!isRelatedClass(refc, lookupClass))

    98                     return isSamePackage(defc, lookupClass);

    99                 // If refc == defc, the call to isPublicSuperClass will do

   100                 // the whole job, since in that case refc (as defc) will be

   101                 // a superclass of the lookup class.

   102             }

   103         }

   104         if (defc == lookupClass)

   105             return true;        // easy check; all self-access is OK

   106         switch (mods & ALL_ACCESS_MODES) {

   107         case PUBLIC:

   108             if (refc != defc)  return true;  // already checked above

   109             return isClassAccessible(refc, lookupClass);

   110         case PROTECTED:

   111             return isSamePackage(defc, lookupClass) || isPublicSuperClass(defc, lookupClass);

   112         case PACKAGE_ONLY:

   113             return isSamePackage(defc, lookupClass);

   114         case PRIVATE:

   115             // Loosened rules for privates follows access rules for inner classes.

   116             return (ALLOW_NESTMATE_ACCESS &&

   117                     isSamePackageMember(defc, lookupClass));

   118         default:

   119             throw new IllegalArgumentException("bad modifiers: "+Modifier.toString(mods));

   120         }

   121     }

   122 

   123     static boolean isRelatedClass(Class<?> refc, Class<?> lookupClass) {

   124         return (refc == lookupClass ||

   125                 refc.isAssignableFrom(lookupClass) ||

   126                 lookupClass.isAssignableFrom(refc));

   127     }

   128 

   129     static boolean isPublicSuperClass(Class<?> defc, Class<?> lookupClass) {

   130         return isPublic(defc.getModifiers()) && defc.isAssignableFrom(lookupClass);

   131     }

   132 

   133     /**

   134      * Evaluate the JVM linkage rules for access to the given class on behalf of caller.

   135      * <h3>JVM Specification, 5.4.4 "Access Control"</h3>

   136      * A class or interface C is accessible to a class or interface D

   137      * if and only if either of the following conditions are true:<ul>

   138      * <li>C is public.

   139      * <li>C and D are members of the same runtime package.

   140      * </ul>

   141      * @param refc the symbolic reference class to which access is being checked (C)

   142      * @param lookupClass the class performing the lookup (D)

   143      */

   144     public static boolean isClassAccessible(Class<?> refc, Class<?> lookupClass) {

   145         int mods = refc.getModifiers();

   146         if (isPublic(mods))

   147             return true;

   148         if (isSamePackage(lookupClass, refc))

   149             return true;

   150         return false;

   151     }

   152 

   153     /**

   154      * Test if two classes have the same class loader and package qualifier.

   155      * @param class1

   156      * @param class2

   157      * @return whether they are in the same package

   158      */

   159     public static boolean isSamePackage(Class<?> class1, Class<?> class2) {

   160         if (class1 == class2)

   161             return true;

   162         if (!loadersAreRelated(class1.getClassLoader(), class2.getClassLoader()))

   163             return false;

   164         String name1 = class1.getName(), name2 = class2.getName();

   165         int dot = name1.lastIndexOf('.');

   166         if (dot != name2.lastIndexOf('.'))

   167             return false;

   168         for (int i = 0; i < dot; i++) {

   169             if (name1.charAt(i) != name2.charAt(i))

   170                 return false;

   171         }

   172         return true;

   173     }

   174 

   175     /**

   176      * Test if two classes are defined as part of the same package member (top-level class).

   177      * If this is true, they can share private access with each other.

   178      * @param class1

   179      * @param class2

   180      * @return whether they are identical or nested together

   181      */

   182     public static boolean isSamePackageMember(Class<?> class1, Class<?> class2) {

   183         if (class1 == class2)

   184             return true;

   185         if (!isSamePackage(class1, class2))

   186             return false;

   187         if (getOutermostEnclosingClass(class1) != getOutermostEnclosingClass(class2))

   188             return false;

   189         return true;

   190     }

   191 

   192     private static Class<?> getOutermostEnclosingClass(Class<?> c) {

   193         Class<?> pkgmem = c;

   194         for (Class<?> enc = c; (enc = enc.getEnclosingClass()) != null; )

   195             pkgmem = enc;

   196         return pkgmem;

   197     }

   198 

   199     private static boolean loadersAreRelated(ClassLoader loader1, ClassLoader loader2) {

   200         if (loader1 == loader2 || loader1 == null || loader2 == null) {

   201             return true;

   202         }

   203         for (ClassLoader scan1 = loader1;

   204                 scan1 != null; scan1 = scan1.getParent()) {

   205             if (scan1 == loader2)  return true;

   206         }

   207         for (ClassLoader scan2 = loader2;

   208                 scan2 != null; scan2 = scan2.getParent()) {

   209             if (scan2 == loader1)  return true;

   210         }

   211         return false;

   212     }

   213 }