1 /*
2 * Copyright 2008-2009 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package impl.java.dyn.util;
27
28 import impl.java.dyn.MemberName;
29 import java.lang.reflect.Method;
30 import java.lang.reflect.Modifier;
31 import java.util.Arrays;
32
33 /**
34 * This class centralizes information about the JVM's linkage access control.
35 * @author jrose
36 */
37 public class VerifyAccess {
38
39 private VerifyAccess() { } // cannot instantiate
40
41 /**
42 * Evaluate the JVM linkage rules for access to the given method on behalf of caller.
43 * Return non-null if and only if the given accessing class has at least partial
44 * privileges to invoke the given method. The return value {@code Object.class}
45 * denotes unlimited privileges.
46 * <p>
47 * Some circumstances require an additional check on the
48 * leading parameter (the receiver) of the method, if it is non-static.
49 * In the case of {@code invokespecial} ({@code doDispatch} is false),
50 * the leading parameter must be the accessing class or a subclass.
51 * In the case of a call to a {@code protected} method outside the same
52 * package, the same constraint applies.
53 * @param m the proposed callee
54 * @param doDispatch if false, a non-static m will be invoked as if by {@code invokespecial}
55 * @param accessingClass the class for which the access check is being made
56 * @return null if the method is not accessible, else a receiver type constraint, else {@code Object.class}
57 */
58 public static Class<?> isAccessible(Class<?> defc, int mods,
59 boolean doDispatch, Class<?> accessingClass) {
60 if (!isAccessible(defc, accessingClass))
61 return null;
62 Class<?> constraint = Object.class;
63 if (!doDispatch && !Modifier.isStatic(mods)) {
64 constraint = accessingClass;
65 }
66 if (Modifier.isPublic(mods))
67 return constraint;
68 if (Modifier.isPrivate(mods))
69 return (defc == accessingClass) ? constraint : null;
70 if (isSamePackage(defc, accessingClass))
71 return constraint;
72 if (Modifier.isProtected(mods) && defc.isAssignableFrom(accessingClass))
73 return constraint;
74 // else it is private or package scoped, and not close enough
75 return null;
76 }
77
78 /**
79 * Evaluate the JVM linkage rules for access to the given class on behalf of caller.
80 */
81 public static boolean isAccessible(Class<?> refc, Class<?> accessingClass) {
82 int mods = refc.getModifiers();
83 if (Modifier.isPublic(mods))
84 return true;
85 if (isSamePackage(accessingClass, refc))
86 return true;
87 return false;
88 }
89
90 /**
91 * Test if two classes have the same class loader and package qualifier.
92 * @param class1
93 * @param class2
94 * @return whether they are in the same package
95 */
96 public static boolean isSamePackage(Class<?> class1, Class<?> class2) {
97 if (class1 == class2)
98 return true;
99 if (class1.getClassLoader() != class2.getClassLoader())
100 return false;
101 String name1 = class1.getName(), name2 = class2.getName();
102 int dot = name1.lastIndexOf('.');
103 if (dot != name2.lastIndexOf('.'))
104 return false;
105 for (int i = 0; i < dot; i++) {
106 if (name1.charAt(i) != name2.charAt(i))
107 return false;
108 }
109 return true;
110 }
111
112 /**
113 * Test if two classes are defined as part of the same package member (top-level class).
114 * If this is true, they can share private access with each other.
115 * @param class1
116 * @param class2
117 * @return whether they are identical or nested together
118 */
119 public static boolean isSamePackageMember(Class<?> class1, Class<?> class2) {
120 if (class1 == class2)
121 return true;
122 if (!isSamePackage(class1, class2))
123 return false;
124 if (getOutermostEnclosingClass(class1) != getOutermostEnclosingClass(class2))
125 return false;
126 return true;
127 }
128
129 private static Class<?> getOutermostEnclosingClass(Class<?> c) {
130 Class<?> pkgmem = c;
131 for (Class<?> enc = c; (enc = enc.getEnclosingClass()) != null; )
132 pkgmem = enc;
133 return pkgmem;
134 }
135 }