1 /*
2 * Copyright (c) 1997, 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 java.lang.reflect;
27
28 import java.security.AccessController;
29 import sun.reflect.Reflection;
30 import sun.reflect.ReflectionFactory;
31 import java.lang.annotation.Annotation;
32
33 /**
34 * The AccessibleObject class is the base class for Field, Method and
35 * Constructor objects. It provides the ability to flag a reflected
36 * object as suppressing default Java language access control checks
37 * when it is used. The access checks--for public, default (package)
38 * access, protected, and private members--are performed when Fields,
39 * Methods or Constructors are used to set or get fields, to invoke
40 * methods, or to create and initialize new instances of classes,
41 * respectively.
42 *
43 * <p>Setting the {@code accessible} flag in a reflected object
44 * permits sophisticated applications with sufficient privilege, such
45 * as Java Object Serialization or other persistence mechanisms, to
46 * manipulate objects in a manner that would normally be prohibited.
47 *
48 * <p>By default, a reflected object is <em>not</em> accessible.
49 *
50 * @see Field
51 * @see Method
52 * @see Constructor
53 * @see ReflectPermission
54 *
55 * @since 1.2
56 */
57 public class AccessibleObject implements AnnotatedElement {
58
59 /**
60 * The Permission object that is used to check whether a client
61 * has sufficient privilege to defeat Java language access
62 * control checks.
63 */
64 static final private java.security.Permission ACCESS_PERMISSION =
65 new ReflectPermission("suppressAccessChecks");
66
67 /**
68 * Convenience method to set the {@code accessible} flag for an
69 * array of objects with a single security check (for efficiency).
70 *
71 * <p>First, if there is a security manager, its
72 * {@code checkPermission} method is called with a
73 * {@code ReflectPermission("suppressAccessChecks")} permission.
74 *
75 * <p>A {@code SecurityException} is raised if {@code flag} is
76 * {@code true} but accessibility of any of the elements of the input
77 * {@code array} may not be changed (for example, if the element
78 * object is a {@link Constructor} object for the class {@link
79 * java.lang.Class}). In the event of such a SecurityException, the
80 * accessibility of objects is set to {@code flag} for array elements
81 * upto (and excluding) the element for which the exception occurred; the
82 * accessibility of elements beyond (and including) the element for which
83 * the exception occurred is unchanged.
84 *
85 * @param array the array of AccessibleObjects
86 * @param flag the new value for the {@code accessible} flag
87 * in each object
88 * @throws SecurityException if the request is denied.
89 * @see SecurityManager#checkPermission
90 * @see java.lang.RuntimePermission
91 */
92 public static void setAccessible(AccessibleObject[] array, boolean flag)
93 throws SecurityException {
94 SecurityManager sm = System.getSecurityManager();
95 if (sm != null) sm.checkPermission(ACCESS_PERMISSION);
96 for (int i = 0; i < array.length; i++) {
97 setAccessible0(array[i], flag);
98 }
99 }
100
101 /**
102 * Set the {@code accessible} flag for this object to
103 * the indicated boolean value. A value of {@code true} indicates that
104 * the reflected object should suppress Java language access
105 * checking when it is used. A value of {@code false} indicates
106 * that the reflected object should enforce Java language access checks.
107 *
108 * <p>First, if there is a security manager, its
109 * {@code checkPermission} method is called with a
110 * {@code ReflectPermission("suppressAccessChecks")} permission.
111 *
112 * <p>A {@code SecurityException} is raised if {@code flag} is
113 * {@code true} but accessibility of this object may not be changed
114 * (for example, if this element object is a {@link Constructor} object for
115 * the class {@link java.lang.Class}).
116 *
117 * <p>A {@code SecurityException} is raised if this object is a {@link
118 * java.lang.reflect.Constructor} object for the class
119 * {@code java.lang.Class}, and {@code flag} is true.
120 *
121 * @param flag the new value for the {@code accessible} flag
122 * @throws SecurityException if the request is denied.
123 * @see SecurityManager#checkPermission
124 * @see java.lang.RuntimePermission
125 */
126 public void setAccessible(boolean flag) throws SecurityException {
127 SecurityManager sm = System.getSecurityManager();
128 if (sm != null) sm.checkPermission(ACCESS_PERMISSION);
129 setAccessible0(this, flag);
130 }
131
132 /* Check that you aren't exposing java.lang.Class.<init>. */
133 private static void setAccessible0(AccessibleObject obj, boolean flag)
134 throws SecurityException
135 {
136 if (obj instanceof Constructor && flag == true) {
137 Constructor<?> c = (Constructor<?>)obj;
138 if (c.getDeclaringClass() == Class.class) {
139 throw new SecurityException("Can not make a java.lang.Class" +
140 " constructor accessible");
141 }
142 }
143 obj.override = flag;
144 }
145
146 /**
147 * Get the value of the {@code accessible} flag for this object.
148 *
149 * @return the value of the object's {@code accessible} flag
150 */
151 public boolean isAccessible() {
152 return override;
153 }
154
155 /**
156 * Constructor: only used by the Java Virtual Machine.
157 */
158 protected AccessibleObject() {}
159
160 // Indicates whether language-level access checks are overridden
161 // by this object. Initializes to "false". This field is used by
162 // Field, Method, and Constructor.
163 //
164 // NOTE: for security purposes, this field must not be visible
165 // outside this package.
166 boolean override;
167
168 // Reflection factory used by subclasses for creating field,
169 // method, and constructor accessors. Note that this is called
170 // very early in the bootstrapping process.
171 static final ReflectionFactory reflectionFactory =
172 AccessController.doPrivileged(
173 new sun.reflect.ReflectionFactory.GetReflectionFactoryAction());
174
175 /**
176 * @throws NullPointerException {@inheritDoc}
177 * @since 1.5
178 */
179 public <T extends Annotation> T getAnnotation(Class<T> annotationClass) {
180 throw new AssertionError("All subclasses should override this method");
181 }
182
183 /**
184 * {@inheritDoc}
185 * @throws NullPointerException {@inheritDoc}
186 * @since 1.5
187 */
188 @Override
189 public boolean isAnnotationPresent(Class<? extends Annotation> annotationClass) {
190 return AnnotatedElement.super.isAnnotationPresent(annotationClass);
191 }
192
193 /**
194 * @throws NullPointerException {@inheritDoc}
195 * @since 1.8
196 */
197 @Override
198 public <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass) {
199 throw new AssertionError("All subclasses should override this method");
200 }
201
202 /**
203 * @since 1.5
204 */
205 public Annotation[] getAnnotations() {
206 return getDeclaredAnnotations();
207 }
208
209 /**
210 * @throws NullPointerException {@inheritDoc}
211 * @since 1.8
212 */
213 @Override
214 public <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass) {
215 // Only annotations on classes are inherited, for all other
216 // objects getDeclaredAnnotation is the same as
217 // getAnnotation.
218 return getAnnotation(annotationClass);
219 }
220
221 /**
222 * @throws NullPointerException {@inheritDoc}
223 * @since 1.8
224 */
225 @Override
226 public <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass) {
227 // Only annotations on classes are inherited, for all other
228 // objects getDeclaredAnnotationsByType is the same as
229 // getAnnotationsByType.
230 return getAnnotationsByType(annotationClass);
231 }
232
233 /**
234 * @since 1.5
235 */
236 public Annotation[] getDeclaredAnnotations() {
237 throw new AssertionError("All subclasses should override this method");
238 }
239
240
241 // Shared access checking logic.
242
243 // For non-public members or members in package-private classes,
244 // it is necessary to perform somewhat expensive security checks.
245 // If the security check succeeds for a given class, it will
246 // always succeed (it is not affected by the granting or revoking
247 // of permissions); we speed up the check in the common case by
248 // remembering the last Class for which the check succeeded.
249 //
250 // The simple security check for Constructor is to see if
251 // the caller has already been seen, verified, and cached.
252 // (See also Class.newInstance(), which uses a similar method.)
253 //
254 // A more complicated security check cache is needed for Method and Field
255 // The cache can be either null (empty cache), a 2-array of {caller,target},
256 // or a caller (with target implicitly equal to this.clazz).
257 // In the 2-array case, the target is always different from the clazz.
258 volatile Object securityCheckCache;
259
260 void checkAccess(Class<?> caller, Class<?> clazz, Object obj, int modifiers)
261 throws IllegalAccessException
262 {
263 if (caller == clazz) { // quick check
264 return; // ACCESS IS OK
265 }
266 Object cache = securityCheckCache; // read volatile
267 Class<?> targetClass = clazz;
268 if (obj != null
269 && Modifier.isProtected(modifiers)
270 && ((targetClass = obj.getClass()) != clazz)) {
271 // Must match a 2-list of { caller, targetClass }.
272 if (cache instanceof Class[]) {
273 Class<?>[] cache2 = (Class<?>[]) cache;
274 if (cache2[1] == targetClass &&
275 cache2[0] == caller) {
276 return; // ACCESS IS OK
277 }
278 // (Test cache[1] first since range check for [1]
279 // subsumes range check for [0].)
280 }
281 } else if (cache == caller) {
282 // Non-protected case (or obj.class == this.clazz).
283 return; // ACCESS IS OK
284 }
285
286 // If no return, fall through to the slow path.
287 slowCheckMemberAccess(caller, clazz, obj, modifiers, targetClass);
288 }
289
290 // Keep all this slow stuff out of line:
291 void slowCheckMemberAccess(Class<?> caller, Class<?> clazz, Object obj, int modifiers,
292 Class<?> targetClass)
293 throws IllegalAccessException
294 {
295 Reflection.ensureMemberAccess(caller, clazz, obj, modifiers);
296
297 // Success: Update the cache.
298 Object cache = ((targetClass == clazz)
299 ? caller
300 : new Class<?>[] { caller, targetClass });
301
302 // Note: The two cache elements are not volatile,
303 // but they are effectively final. The Java memory model
304 // guarantees that the initializing stores for the cache
305 // elements will occur before the volatile write.
306 securityCheckCache = cache; // write volatile
307 }
308 }