1 /*
2 * Copyright (c) 2008, 2013, 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.invoke.util;
27
28 import java.lang.reflect.Modifier;
29 import static java.lang.reflect.Modifier.*;
30 import sun.reflect.Reflection;
31
32 /**
33 * This class centralizes information about the JVM's linkage access control.
34 * @author jrose
35 */
36 public class VerifyAccess {
37
38 private VerifyAccess() { } // cannot instantiate
39
40 private static final int PACKAGE_ONLY = 0;
41 private static final int PACKAGE_ALLOWED = java.lang.invoke.MethodHandles.Lookup.PACKAGE;
42 private static final int PROTECTED_OR_PACKAGE_ALLOWED = (PACKAGE_ALLOWED|PROTECTED);
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 int allowedModes) {
90 if (allowedModes == 0) return false;
91 assert((allowedModes & PUBLIC) != 0 &&
92 (allowedModes & ~(ALL_ACCESS_MODES|PACKAGE_ALLOWED)) == 0);
93 // The symbolic reference class (refc) must always be fully verified.
94 if (!isClassAccessible(refc, lookupClass, allowedModes)) {
95 return false;
96 }
97 // Usually refc and defc are the same, but verify defc also in case they differ.
98 if (defc == lookupClass &&
99 (allowedModes & PRIVATE) != 0)
100 return true; // easy check; all self-access is OK
101 switch (mods & ALL_ACCESS_MODES) {
102 case PUBLIC:
103 return true; // already checked above
104 case PROTECTED:
105 if ((allowedModes & PROTECTED_OR_PACKAGE_ALLOWED) != 0 &&
106 isSamePackage(defc, lookupClass))
107 return true;
108 if ((allowedModes & PROTECTED) == 0)
109 return false;
110 if ((mods & STATIC) != 0 &&
111 !isRelatedClass(refc, lookupClass))
112 return false;
113 if ((allowedModes & PROTECTED) != 0 &&
114 isSuperClass(defc, lookupClass))
115 return true;
116 return false;
117 case PACKAGE_ONLY: // That is, zero. Unmarked member is package-only access.
118 return ((allowedModes & PACKAGE_ALLOWED) != 0 &&
119 isSamePackage(defc, lookupClass));
120 case PRIVATE:
121 // Loosened rules for privates follows access rules for inner classes.
122 return (ALLOW_NESTMATE_ACCESS &&
123 (allowedModes & PRIVATE) != 0 &&
124 isSamePackageMember(defc, lookupClass));
125 default:
126 throw new IllegalArgumentException("bad modifiers: "+Modifier.toString(mods));
127 }
128 }
129
130 static boolean isRelatedClass(Class<?> refc, Class<?> lookupClass) {
131 return (refc == lookupClass ||
132 refc.isAssignableFrom(lookupClass) ||
133 lookupClass.isAssignableFrom(refc));
134 }
135
136 static boolean isSuperClass(Class<?> defc, Class<?> lookupClass) {
137 return defc.isAssignableFrom(lookupClass);
138 }
139
140 static int getClassModifiers(Class<?> c) {
141 // This would return the mask stored by javac for the source-level modifiers.
142 // return c.getModifiers();
143 // But what we need for JVM access checks are the actual bits from the class header.
144 // ...But arrays and primitives are synthesized with their own odd flags:
145 if (c.isArray() || c.isPrimitive())
146 return c.getModifiers();
147 return Reflection.getClassAccessFlags(c);
148 }
149
150 /**
151 * Evaluate the JVM linkage rules for access to the given class on behalf of caller.
152 * <h3>JVM Specification, 5.4.4 "Access Control"</h3>
153 * A class or interface C is accessible to a class or interface D
154 * if and only if either of the following conditions are true:<ul>
155 * <li>C is public.
156 * <li>C and D are members of the same runtime package.
157 * </ul>
158 * @param refc the symbolic reference class to which access is being checked (C)
159 * @param lookupClass the class performing the lookup (D)
160 */
161 public static boolean isClassAccessible(Class<?> refc, Class<?> lookupClass,
162 int allowedModes) {
163 if (allowedModes == 0) return false;
164 assert((allowedModes & PUBLIC) != 0 &&
165 (allowedModes & ~(ALL_ACCESS_MODES|PACKAGE_ALLOWED)) == 0);
166 int mods = getClassModifiers(refc);
167 if (isPublic(mods))
168 return true;
169 if ((allowedModes & PACKAGE_ALLOWED) != 0 &&
170 isSamePackage(lookupClass, refc))
171 return true;
172 return false;
173 }
174
175 /**
176 * Decide if the given method type, attributed to a member or symbolic
177 * reference of a given reference class, is really visible to that class.
178 * @param type the supposed type of a member or symbolic reference of refc
179 * @param refc the class attempting to make the reference
180 */
181 public static boolean isTypeVisible(Class<?> type, Class<?> refc) {
182 if (type == refc) return true; // easy check
183 while (type.isArray()) type = type.getComponentType();
184 if (type.isPrimitive() || type == Object.class) return true;
185 ClassLoader parent = type.getClassLoader();
186 if (parent == null) return true;
187 ClassLoader child = refc.getClassLoader();
188 if (child == null) return false;
189 if (parent == child || loadersAreRelated(parent, child, true))
190 return true;
191 // Do it the hard way: Look up the type name from the refc loader.
192 try {
193 Class<?> res = child.loadClass(type.getName());
194 return (type == res);
195 } catch (ClassNotFoundException ex) {
196 return false;
197 }
198 }
199
200 /**
201 * Decide if the given method type, attributed to a member or symbolic
202 * reference of a given reference class, is really visible to that class.
203 * @param type the supposed type of a member or symbolic reference of refc
204 * @param refc the class attempting to make the reference
205 */
206 public static boolean isTypeVisible(java.lang.invoke.MethodType type, Class<?> refc) {
207 for (int n = -1, max = type.parameterCount(); n < max; n++) {
208 Class<?> ptype = (n < 0 ? type.returnType() : type.parameterType(n));
209 if (!isTypeVisible(ptype, refc))
210 return false;
211 }
212 return true;
213 }
214
215 /**
216 * Test if two classes have the same class loader and package qualifier.
217 * @param class1 a class
218 * @param class2 another class
219 * @return whether they are in the same package
220 */
221 public static boolean isSamePackage(Class<?> class1, Class<?> class2) {
222 assert(!class1.isArray() && !class2.isArray());
223 if (class1 == class2)
224 return true;
225 if (class1.getClassLoader() != class2.getClassLoader())
226 return false;
227 String name1 = class1.getName(), name2 = class2.getName();
228 int dot = name1.lastIndexOf('.');
229 if (dot != name2.lastIndexOf('.'))
230 return false;
231 for (int i = 0; i < dot; i++) {
232 if (name1.charAt(i) != name2.charAt(i))
233 return false;
234 }
235 return true;
236 }
237
238 /** Return the package name for this class.
239 */
240 public static String getPackageName(Class<?> cls) {
241 assert(!cls.isArray());
242 String name = cls.getName();
243 int dot = name.lastIndexOf('.');
244 if (dot < 0) return "";
245 return name.substring(0, dot);
246 }
247
248 /**
249 * Test if two classes are defined as part of the same package member (top-level class).
250 * If this is true, they can share private access with each other.
251 * @param class1 a class
252 * @param class2 another class
253 * @return whether they are identical or nested together
254 */
255 public static boolean isSamePackageMember(Class<?> class1, Class<?> class2) {
256 if (class1 == class2)
257 return true;
258 if (!isSamePackage(class1, class2))
259 return false;
260 if (getOutermostEnclosingClass(class1) != getOutermostEnclosingClass(class2))
261 return false;
262 return true;
263 }
264
265 private static Class<?> getOutermostEnclosingClass(Class<?> c) {
266 Class<?> pkgmem = c;
267 for (Class<?> enc = c; (enc = enc.getEnclosingClass()) != null; )
268 pkgmem = enc;
269 return pkgmem;
270 }
271
272 private static boolean loadersAreRelated(ClassLoader loader1, ClassLoader loader2,
273 boolean loader1MustBeParent) {
274 if (loader1 == loader2 || loader1 == null
275 || (loader2 == null && !loader1MustBeParent)) {
276 return true;
277 }
278 for (ClassLoader scan2 = loader2;
279 scan2 != null; scan2 = scan2.getParent()) {
280 if (scan2 == loader1) return true;
281 }
282 if (loader1MustBeParent) return false;
283 // see if loader2 is a parent of loader1:
284 for (ClassLoader scan1 = loader1;
285 scan1 != null; scan1 = scan1.getParent()) {
286 if (scan1 == loader2) return true;
287 }
288 return false;
289 }
290
291 /**
292 * Is the class loader of parentClass identical to, or an ancestor of,
293 * the class loader of childClass?
294 * @param parentClass a class
295 * @param childClass another class, which may be a descendent of the first class
296 * @return whether parentClass precedes or equals childClass in class loader order
297 */
298 public static boolean classLoaderIsAncestor(Class<?> parentClass, Class<?> childClass) {
299 return loadersAreRelated(parentClass.getClassLoader(), childClass.getClassLoader(), true);
300 }
301 }