1 /* 2 * Copyright (c) 1997, 2012, 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 * @throws NullPointerException {@inheritDoc} 185 * @since 1.8 186 */ 187 public <T extends Annotation> T[] getAnnotations(Class<T> annotationClass) { 188 throw new AssertionError("All subclasses should override this method"); 189 } 190 191 /** 192 * @since 1.5 193 */ 194 public Annotation[] getAnnotations() { 195 return getDeclaredAnnotations(); 196 } 197 198 /** 199 * @throws NullPointerException {@inheritDoc} 200 * @since 1.8 201 */ 202 public <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass) { 203 // Only annotations on classes are inherited, for all other 204 // objects getDeclaredAnnotation is the same as 205 // getAnnotation. 206 return getAnnotation(annotationClass); 207 } 208 209 /** 210 * @throws NullPointerException {@inheritDoc} 211 * @since 1.8 212 */ 213 public <T extends Annotation> T[] getDeclaredAnnotations(Class<T> annotationClass) { 214 // Only annotations on classes are inherited, for all other 215 // objects getDeclaredAnnotations is the same as 216 // getAnnotations. 217 return getAnnotations(annotationClass); 218 } 219 220 /** 221 * @since 1.5 222 */ 223 public Annotation[] getDeclaredAnnotations() { 224 throw new AssertionError("All subclasses should override this method"); 225 } 226 227 228 // Shared access checking logic. 229 230 // For non-public members or members in package-private classes, 231 // it is necessary to perform somewhat expensive security checks. 232 // If the security check succeeds for a given class, it will 233 // always succeed (it is not affected by the granting or revoking 234 // of permissions); we speed up the check in the common case by 235 // remembering the last Class for which the check succeeded. 236 // 237 // The simple security check for Constructor is to see if 238 // the caller has already been seen, verified, and cached. 239 // (See also Class.newInstance(), which uses a similar method.) 240 // 241 // A more complicated security check cache is needed for Method and Field 242 // The cache can be either null (empty cache), a 2-array of {caller,target}, 243 // or a caller (with target implicitly equal to this.clazz). 244 // In the 2-array case, the target is always different from the clazz. 245 volatile Object securityCheckCache; 246 247 void checkAccess(Class<?> caller, Class<?> clazz, Object obj, int modifiers) 248 throws IllegalAccessException 249 { 250 if (caller == clazz) { // quick check 251 return; // ACCESS IS OK 252 } 253 Object cache = securityCheckCache; // read volatile 254 Class<?> targetClass = clazz; 255 if (obj != null 256 && Modifier.isProtected(modifiers) 257 && ((targetClass = obj.getClass()) != clazz)) { 258 // Must match a 2-list of { caller, targetClass }. 259 if (cache instanceof Class[]) { 260 Class<?>[] cache2 = (Class<?>[]) cache; 261 if (cache2[1] == targetClass && 262 cache2[0] == caller) { 263 return; // ACCESS IS OK 264 } 265 // (Test cache[1] first since range check for [1] 266 // subsumes range check for [0].) 267 } 268 } else if (cache == caller) { 269 // Non-protected case (or obj.class == this.clazz). 270 return; // ACCESS IS OK 271 } 272 273 // If no return, fall through to the slow path. 274 slowCheckMemberAccess(caller, clazz, obj, modifiers, targetClass); 275 } 276 277 // Keep all this slow stuff out of line: 278 void slowCheckMemberAccess(Class<?> caller, Class<?> clazz, Object obj, int modifiers, 279 Class<?> targetClass) 280 throws IllegalAccessException 281 { 282 Reflection.ensureMemberAccess(caller, clazz, obj, modifiers); 283 284 // Success: Update the cache. 285 Object cache = ((targetClass == clazz) 286 ? caller 287 : new Class<?>[] { caller, targetClass }); 288 289 // Note: The two cache elements are not volatile, 290 // but they are effectively final. The Java memory model 291 // guarantees that the initializing stores for the cache 292 // elements will occur before the volatile write. 293 securityCheckCache = cache; // write volatile 294 } 295 }