1 /*
2 * Copyright (c) 1997, 2017, 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.lang.annotation.Annotation;
29 import java.security.AccessController;
30
31 import jdk.internal.misc.VM;
32 import jdk.internal.module.IllegalAccessLogger;
33 import jdk.internal.reflect.CallerSensitive;
34 import jdk.internal.reflect.Reflection;
35 import jdk.internal.reflect.ReflectionFactory;
36 import sun.security.action.GetPropertyAction;
37
38 /**
39 * The {@code AccessibleObject} class is the base class for {@code Field},
40 * {@code Method}, and {@code Constructor} objects (known as <em>reflected
41 * objects</em>). It provides the ability to flag a reflected object as
42 * suppressing checks for Java language access control when it is used. This
43 * permits sophisticated applications with sufficient privilege, such as Java
44 * Object Serialization or other persistence mechanisms, to manipulate objects
45 * in a manner that would normally be prohibited.
46 *
47 * <p> Java language access control prevents use of private members outside
48 * their class; package access members outside their package; protected members
49 * outside their package or subclasses; and public members outside their
50 * module unless they are declared in an {@link Module#isExported(String,Module)
51 * exported} package and the user {@link Module#canRead reads} their module. By
52 * default, Java language access control is enforced (with one variation) when
53 * {@code Field}s, {@code Method}s, or {@code Constructor}s are used to get or
54 * set fields, to invoke methods, or to create and initialize new instances of
55 * classes, respectively. Every reflected object checks that the code using it
56 * is in an appropriate class, package, or module. </p>
57 *
58 * <p> The one variation from Java language access control is that the checks
59 * by reflected objects assume readability. That is, the module containing
60 * the use of a reflected object is assumed to read the module in which
61 * the underlying field, method, or constructor is declared. </p>
62 *
63 * <p> Whether the checks for Java language access control can be suppressed
64 * (and thus, whether access can be enabled) depends on whether the reflected
65 * object corresponds to a member in an exported or open package
66 * (see {@link #setAccessible(boolean)}). </p>
67 *
68 * @jls 6.6 Access Control
69 * @since 1.2
70 * @revised 9
71 * @spec JPMS
72 */
73 public class AccessibleObject implements AnnotatedElement {
74
75 /**
76 * The Permission object that is used to check whether a client
77 * has sufficient privilege to defeat Java language access
78 * control checks.
79 */
80 private static final java.security.Permission ACCESS_PERMISSION =
81 new ReflectPermission("suppressAccessChecks");
82
83 static void checkPermission() {
84 SecurityManager sm = System.getSecurityManager();
85 if (sm != null) sm.checkPermission(ACCESS_PERMISSION);
86 }
87
88 /**
89 * Convenience method to set the {@code accessible} flag for an
90 * array of reflected objects with a single security check (for efficiency).
91 *
92 * <p> This method may be used to enable access to all reflected objects in
93 * the array when access to each reflected object can be enabled as
94 * specified by {@link #setAccessible(boolean) setAccessible(boolean)}. </p>
95 *
96 * <p>If there is a security manager, its
97 * {@code checkPermission} method is first called with a
98 * {@code ReflectPermission("suppressAccessChecks")} permission.
99 *
100 * <p>A {@code SecurityException} is also thrown if any of the elements of
101 * the input {@code array} is a {@link java.lang.reflect.Constructor}
102 * object for the class {@code java.lang.Class} and {@code flag} is true.
103 *
104 * @param array the array of AccessibleObjects
105 * @param flag the new value for the {@code accessible} flag
106 * in each object
107 * @throws InaccessibleObjectException if access cannot be enabled for all
108 * objects in the array
109 * @throws SecurityException if the request is denied by the security manager
110 * or an element in the array is a constructor for {@code
111 * java.lang.Class}
112 * @see SecurityManager#checkPermission
113 * @see ReflectPermission
114 * @revised 9
115 * @spec JPMS
116 */
117 @CallerSensitive
118 public static void setAccessible(AccessibleObject[] array, boolean flag) {
119 checkPermission();
120 if (flag) {
121 Class<?> caller = Reflection.getCallerClass();
122 array = array.clone();
123 for (AccessibleObject ao : array) {
124 ao.checkCanSetAccessible(caller);
125 }
126 }
127 for (AccessibleObject ao : array) {
128 ao.setAccessible0(flag);
129 }
130 }
131
132 /**
133 * Set the {@code accessible} flag for this reflected object to
134 * the indicated boolean value. A value of {@code true} indicates that
135 * the reflected object should suppress checks for Java language access
136 * control when it is used. A value of {@code false} indicates that
137 * the reflected object should enforce checks for Java language access
138 * control when it is used, with the variation noted in the class description.
139 *
140 * <p> This method may be used by a caller in class {@code C} to enable
141 * access to a {@link Member member} of {@link Member#getDeclaringClass()
142 * declaring class} {@code D} if any of the following hold: </p>
143 *
144 * <ul>
145 * <li> {@code C} and {@code D} are in the same module. </li>
146 *
147 * <li> The member is {@code public} and {@code D} is {@code public} in
148 * a package that the module containing {@code D} {@link
149 * Module#isExported(String,Module) exports} to at least the module
150 * containing {@code C}. </li>
151 *
152 * <li> The member is {@code protected} {@code static}, {@code D} is
153 * {@code public} in a package that the module containing {@code D}
154 * exports to at least the module containing {@code C}, and {@code C}
155 * is a subclass of {@code D}. </li>
156 *
157 * <li> {@code D} is in a package that the module containing {@code D}
158 * {@link Module#isOpen(String,Module) opens} to at least the module
159 * containing {@code C}.
160 * All packages in unnamed and open modules are open to all modules and
161 * so this method always succeeds when {@code D} is in an unnamed or
162 * open module. </li>
163 * </ul>
164 *
165 * <p> This method cannot be used to enable access to private members,
166 * members with default (package) access, protected instance members, or
167 * protected constructors when the declaring class is in a different module
168 * to the caller and the package containing the declaring class is not open
169 * to the caller's module. </p>
170 *
171 * <p> If there is a security manager, its
172 * {@code checkPermission} method is first called with a
173 * {@code ReflectPermission("suppressAccessChecks")} permission.
174 *
175 * @param flag the new value for the {@code accessible} flag
176 * @throws InaccessibleObjectException if access cannot be enabled
177 * @throws SecurityException if the request is denied by the security manager
178 * @see #trySetAccessible
179 * @see java.lang.invoke.MethodHandles#privateLookupIn
180 * @revised 9
181 * @spec JPMS
182 */
183 public void setAccessible(boolean flag) {
184 AccessibleObject.checkPermission();
185 setAccessible0(flag);
186 }
187
188 /**
189 * Sets the accessible flag and returns the new value
190 */
191 boolean setAccessible0(boolean flag) {
192 this.override = flag;
193 return flag;
194 }
195
196 /**
197 * Set the {@code accessible} flag for this reflected object to {@code true}
198 * if possible. This method sets the {@code accessible} flag, as if by
199 * invoking {@link #setAccessible(boolean) setAccessible(true)}, and returns
200 * the possibly-updated value for the {@code accessible} flag. If access
201 * cannot be enabled, i.e. the checks or Java language access control cannot
202 * be suppressed, this method returns {@code false} (as opposed to {@code
203 * setAccessible(true)} throwing {@code InaccessibleObjectException} when
204 * it fails).
205 *
206 * <p> This method is a no-op if the {@code accessible} flag for
207 * this reflected object is {@code true}.
208 *
209 * <p> For example, a caller can invoke {@code trySetAccessible}
210 * on a {@code Method} object for a private instance method
211 * {@code p.T::privateMethod} to suppress the checks for Java language access
212 * control when the {@code Method} is invoked.
213 * If {@code p.T} class is in a different module to the caller and
214 * package {@code p} is open to at least the caller's module,
215 * the code below successfully sets the {@code accessible} flag
216 * to {@code true}.
217 *
218 * <pre>
219 * {@code
220 * p.T obj = ....; // instance of p.T
221 * :
222 * Method m = p.T.class.getDeclaredMethod("privateMethod");
223 * if (m.trySetAccessible()) {
224 * m.invoke(obj);
225 * } else {
226 * // package p is not opened to the caller to access private member of T
227 * ...
228 * }
229 * }</pre>
230 *
231 * <p> If there is a security manager, its {@code checkPermission} method
232 * is first called with a {@code ReflectPermission("suppressAccessChecks")}
233 * permission. </p>
234 *
235 * @return {@code true} if the {@code accessible} flag is set to {@code true};
236 * {@code false} if access cannot be enabled.
237 * @throws SecurityException if the request is denied by the security manager
238 *
239 * @since 9
240 * @spec JPMS
241 * @see java.lang.invoke.MethodHandles#privateLookupIn
242 */
243 @CallerSensitive
244 public final boolean trySetAccessible() {
245 AccessibleObject.checkPermission();
246
247 if (override == true) return true;
248
249 // if it's not a Constructor, Method, Field then no access check
250 if (!Member.class.isInstance(this)) {
251 return setAccessible0(true);
252 }
253
254 // does not allow to suppress access check for Class's constructor
255 Class<?> declaringClass = ((Member) this).getDeclaringClass();
256 if (declaringClass == Class.class && this instanceof Constructor) {
257 return false;
258 }
259
260 if (checkCanSetAccessible(Reflection.getCallerClass(),
261 declaringClass,
262 false)) {
263 return setAccessible0(true);
264 } else {
265 return false;
266 }
267 }
268
269
270 /**
271 * If the given AccessibleObject is a {@code Constructor}, {@code Method}
272 * or {@code Field} then checks that its declaring class is in a package
273 * that can be accessed by the given caller of setAccessible.
274 */
275 void checkCanSetAccessible(Class<?> caller) {
276 // do nothing, needs to be overridden by Constructor, Method, Field
277 }
278
279
280 void checkCanSetAccessible(Class<?> caller, Class<?> declaringClass) {
281 checkCanSetAccessible(caller, declaringClass, true);
282 }
283
284 private boolean checkCanSetAccessible(Class<?> caller,
285 Class<?> declaringClass,
286 boolean throwExceptionIfDenied) {
287 Module callerModule = caller.getModule();
288 Module declaringModule = declaringClass.getModule();
289
290 if (callerModule == declaringModule) return true;
291 if (callerModule == Object.class.getModule()) return true;
292 if (!declaringModule.isNamed()) return true;
293
294 String pn = declaringClass.getPackageName();
295 int modifiers;
296 if (this instanceof Executable) {
297 modifiers = ((Executable) this).getModifiers();
298 } else {
299 modifiers = ((Field) this).getModifiers();
300 }
301
302 // class is public and package is exported to caller
303 boolean isClassPublic = Modifier.isPublic(declaringClass.getModifiers());
304 if (isClassPublic && declaringModule.isExported(pn, callerModule)) {
305 // member is public
306 if (Modifier.isPublic(modifiers)) {
307 logIfExportedByBackdoor(caller, declaringClass);
308 return true;
309 }
310
311 // member is protected-static
312 if (Modifier.isProtected(modifiers)
313 && Modifier.isStatic(modifiers)
314 && isSubclassOf(caller, declaringClass)) {
315 logIfExportedByBackdoor(caller, declaringClass);
316 return true;
317 }
318 }
319
320 // package is open to caller
321 if (declaringModule.isOpen(pn, callerModule)) {
322 logIfOpenByBackdoor(caller, declaringClass);
323 return true;
324 }
325
326 if (throwExceptionIfDenied) {
327 // not accessible
328 String msg = "Unable to make ";
329 if (this instanceof Field)
330 msg += "field ";
331 msg += this + " accessible: " + declaringModule + " does not \"";
332 if (isClassPublic && Modifier.isPublic(modifiers))
333 msg += "exports";
334 else
335 msg += "opens";
336 msg += " " + pn + "\" to " + callerModule;
337 InaccessibleObjectException e = new InaccessibleObjectException(msg);
338 if (printStackTraceWhenAccessFails()) {
339 e.printStackTrace(System.err);
340 }
341 throw e;
342 }
343 return false;
344 }
345
346 private boolean isSubclassOf(Class<?> queryClass, Class<?> ofClass) {
347 while (queryClass != null) {
348 if (queryClass == ofClass) {
349 return true;
350 }
351 queryClass = queryClass.getSuperclass();
352 }
353 return false;
354 }
355
356 private void logIfOpenByBackdoor(Class<?> caller, Class<?> declaringClass) {
357 Module callerModule = caller.getModule();
358 Module targetModule = declaringClass.getModule();
359 // callerModule is null during early startup
360 if (callerModule != null && !callerModule.isNamed() && targetModule.isNamed()) {
361 IllegalAccessLogger logger = IllegalAccessLogger.illegalAccessLogger();
362 if (logger != null) {
363 logger.logIfOpenByBackdoor(caller, declaringClass, this::toShortString);
364 }
365 }
366 }
367
368 private void logIfExportedByBackdoor(Class<?> caller, Class<?> declaringClass) {
369 Module callerModule = caller.getModule();
370 Module targetModule = declaringClass.getModule();
371 // callerModule is null during early startup
372 if (callerModule != null && !callerModule.isNamed() && targetModule.isNamed()) {
373 IllegalAccessLogger logger = IllegalAccessLogger.illegalAccessLogger();
374 if (logger != null) {
375 logger.logIfExportedByBackdoor(caller, declaringClass, this::toShortString);
376 }
377 }
378 }
379
380 /**
381 * Returns a short descriptive string to describe this object in log messages.
382 */
383 String toShortString() {
384 return toString();
385 }
386
387 /**
388 * Get the value of the {@code accessible} flag for this reflected object.
389 *
390 * @return the value of the object's {@code accessible} flag
391 *
392 * @deprecated
393 * This method is deprecated because its name hints that it checks
394 * if the reflected object is accessible when it actually indicates
395 * if the checks for Java language access control are suppressed.
396 * This method may return {@code false} on a reflected object that is
397 * accessible to the caller. To test if this reflected object is accessible,
398 * it should use {@link #canAccess(Object)}.
399 *
400 * @revised 9
401 * @spec JPMS
402 */
403 @Deprecated(since="9")
404 public boolean isAccessible() {
405 return override;
406 }
407
408 /**
409 * Test if the caller can access this reflected object. If this reflected
410 * object corresponds to an instance method or field then this method tests
411 * if the caller can access the given {@code obj} with the reflected object.
412 * For instance methods or fields then the {@code obj} argument must be an
413 * instance of the {@link Member#getDeclaringClass() declaring class}. For
414 * static members and constructors then {@code obj} must be {@code null}.
415 *
416 * <p> This method returns {@code true} if the {@code accessible} flag
417 * is set to {@code true}, i.e. the checks for Java language access control
418 * are suppressed, or if the caller can access the member as
419 * specified in <cite>The Java™ Language Specification</cite>,
420 * with the variation noted in the class description. </p>
421 *
422 * @param obj an instance object of the declaring class of this reflected
423 * object if it is an instance method or field
424 *
425 * @return {@code true} if the caller can access this reflected object.
426 *
427 * @throws IllegalArgumentException
428 * <ul>
429 * <li> if this reflected object is a static member or constructor and
430 * the given {@code obj} is non-{@code null}, or </li>
431 * <li> if this reflected object is an instance method or field
432 * and the given {@code obj} is {@code null} or of type
433 * that is not a subclass of the {@link Member#getDeclaringClass()
434 * declaring class} of the member.</li>
435 * </ul>
436 *
437 * @since 9
438 * @spec JPMS
439 * @jls 6.6 Access Control
440 * @see #trySetAccessible
441 * @see #setAccessible(boolean)
442 */
443 @CallerSensitive
444 public final boolean canAccess(Object obj) {
445 if (!Member.class.isInstance(this)) {
446 return override;
447 }
448
449 Class<?> declaringClass = ((Member) this).getDeclaringClass();
450 int modifiers = ((Member) this).getModifiers();
451 if (!Modifier.isStatic(modifiers) &&
452 (this instanceof Method || this instanceof Field)) {
453 if (obj == null) {
454 throw new IllegalArgumentException("null object for " + this);
455 }
456 // if this object is an instance member, the given object
457 // must be a subclass of the declaring class of this reflected object
458 if (!declaringClass.isAssignableFrom(obj.getClass())) {
459 throw new IllegalArgumentException("object is not an instance of "
460 + declaringClass.getName());
461 }
462 } else if (obj != null) {
463 throw new IllegalArgumentException("non-null object for " + this);
464 }
465
466 // access check is suppressed
467 if (override) return true;
468
469 Class<?> caller = Reflection.getCallerClass();
470 Class<?> targetClass;
471 if (this instanceof Constructor) {
472 targetClass = declaringClass;
473 } else {
474 targetClass = Modifier.isStatic(modifiers) ? null : obj.getClass();
475 }
476 return verifyAccess(caller, declaringClass, targetClass, modifiers);
477 }
478
479 /**
480 * Constructor: only used by the Java Virtual Machine.
481 */
482 protected AccessibleObject() {}
483
484 // Indicates whether language-level access checks are overridden
485 // by this object. Initializes to "false". This field is used by
486 // Field, Method, and Constructor.
487 //
488 // NOTE: for security purposes, this field must not be visible
489 // outside this package.
490 boolean override;
491
492 // Reflection factory used by subclasses for creating field,
493 // method, and constructor accessors. Note that this is called
494 // very early in the bootstrapping process.
495 static final ReflectionFactory reflectionFactory =
496 AccessController.doPrivileged(
497 new ReflectionFactory.GetReflectionFactoryAction());
498
499 /**
500 * @throws NullPointerException {@inheritDoc}
501 * @since 1.5
502 */
503 public <T extends Annotation> T getAnnotation(Class<T> annotationClass) {
504 throw new AssertionError("All subclasses should override this method");
505 }
506
507 /**
508 * {@inheritDoc}
509 * @throws NullPointerException {@inheritDoc}
510 * @since 1.5
511 */
512 @Override
513 public boolean isAnnotationPresent(Class<? extends Annotation> annotationClass) {
514 return AnnotatedElement.super.isAnnotationPresent(annotationClass);
515 }
516
517 /**
518 * @throws NullPointerException {@inheritDoc}
519 * @since 1.8
520 */
521 @Override
522 public <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass) {
523 throw new AssertionError("All subclasses should override this method");
524 }
525
526 /**
527 * @since 1.5
528 */
529 public Annotation[] getAnnotations() {
530 return getDeclaredAnnotations();
531 }
532
533 /**
534 * @throws NullPointerException {@inheritDoc}
535 * @since 1.8
536 */
537 @Override
538 public <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass) {
539 // Only annotations on classes are inherited, for all other
540 // objects getDeclaredAnnotation is the same as
541 // getAnnotation.
542 return getAnnotation(annotationClass);
543 }
544
545 /**
546 * @throws NullPointerException {@inheritDoc}
547 * @since 1.8
548 */
549 @Override
550 public <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass) {
551 // Only annotations on classes are inherited, for all other
552 // objects getDeclaredAnnotationsByType is the same as
553 // getAnnotationsByType.
554 return getAnnotationsByType(annotationClass);
555 }
556
557 /**
558 * @since 1.5
559 */
560 public Annotation[] getDeclaredAnnotations() {
561 throw new AssertionError("All subclasses should override this method");
562 }
563
564
565 // Shared access checking logic.
566
567 // For non-public members or members in package-private classes,
568 // it is necessary to perform somewhat expensive security checks.
569 // If the security check succeeds for a given class, it will
570 // always succeed (it is not affected by the granting or revoking
571 // of permissions); we speed up the check in the common case by
572 // remembering the last Class for which the check succeeded.
573 //
574 // The simple security check for Constructor is to see if
575 // the caller has already been seen, verified, and cached.
576 // (See also Class.newInstance(), which uses a similar method.)
577 //
578 // A more complicated security check cache is needed for Method and Field
579 // The cache can be either null (empty cache), a 2-array of {caller,targetClass},
580 // or a caller (with targetClass implicitly equal to memberClass).
581 // In the 2-array case, the targetClass is always different from the memberClass.
582 volatile Object securityCheckCache;
583
584 final void checkAccess(Class<?> caller, Class<?> memberClass,
585 Class<?> targetClass, int modifiers)
586 throws IllegalAccessException
587 {
588 if (!verifyAccess(caller, memberClass, targetClass, modifiers)) {
589 IllegalAccessException e = Reflection.newIllegalAccessException(
590 caller, memberClass, targetClass, modifiers);
591 if (printStackTraceWhenAccessFails()) {
592 e.printStackTrace(System.err);
593 }
594 throw e;
595 }
596 }
597
598 final boolean verifyAccess(Class<?> caller, Class<?> memberClass,
599 Class<?> targetClass, int modifiers)
600 {
601 if (caller == memberClass) { // quick check
602 return true; // ACCESS IS OK
603 }
604 Object cache = securityCheckCache; // read volatile
605 if (targetClass != null // instance member or constructor
606 && Modifier.isProtected(modifiers)
607 && targetClass != memberClass) {
608 // Must match a 2-list of { caller, targetClass }.
609 if (cache instanceof Class[]) {
610 Class<?>[] cache2 = (Class<?>[]) cache;
611 if (cache2[1] == targetClass &&
612 cache2[0] == caller) {
613 return true; // ACCESS IS OK
614 }
615 // (Test cache[1] first since range check for [1]
616 // subsumes range check for [0].)
617 }
618 } else if (cache == caller) {
619 // Non-protected case (or targetClass == memberClass or static member).
620 return true; // ACCESS IS OK
621 }
622
623 // If no return, fall through to the slow path.
624 return slowVerifyAccess(caller, memberClass, targetClass, modifiers);
625 }
626
627 // Keep all this slow stuff out of line:
628 private boolean slowVerifyAccess(Class<?> caller, Class<?> memberClass,
629 Class<?> targetClass, int modifiers)
630 {
631 if (Reflection.verifyMemberAccess(caller, memberClass, targetClass, modifiers)) {
632 // access okay
633 logIfExportedByBackdoor(caller, memberClass);
634 } else {
635 // access denied
636 return false;
637 }
638
639 // Success: Update the cache.
640 Object cache = (targetClass != null
641 && Modifier.isProtected(modifiers)
642 && targetClass != memberClass)
643 ? new Class<?>[] { caller, targetClass }
644 : caller;
645
646 // Note: The two cache elements are not volatile,
647 // but they are effectively final. The Java memory model
648 // guarantees that the initializing stores for the cache
649 // elements will occur before the volatile write.
650 securityCheckCache = cache; // write volatile
651 return true;
652 }
653
654 // true to print a stack trace when access fails
655 private static volatile boolean printStackWhenAccessFails;
656
657 // true if printStack* values are initialized
658 private static volatile boolean printStackPropertiesSet;
659
660 /**
661 * Returns true if a stack trace should be printed when access fails.
662 */
663 private static boolean printStackTraceWhenAccessFails() {
664 if (!printStackPropertiesSet && VM.initLevel() >= 1) {
665 String s = GetPropertyAction.privilegedGetProperty(
666 "sun.reflect.debugModuleAccessChecks");
667 if (s != null) {
668 printStackWhenAccessFails = !s.equalsIgnoreCase("false");
669 }
670 printStackPropertiesSet = true;
671 }
672 return printStackWhenAccessFails;
673 }
674 }