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 VerifyAccess()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 */ isMemberAccessible(Class<?> refc, Class<?> defc, int mods, Class<?> lookupClass, int allowedModes)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 assert !defc.isInterface(); // protected members aren't allowed in interfaces 106 if ((allowedModes & PROTECTED_OR_PACKAGE_ALLOWED) != 0 && 107 isSamePackage(defc, lookupClass)) 108 return true; 109 if ((allowedModes & PROTECTED) == 0) 110 return false; 111 // Protected members are accessible by subclasses, which does not include interfaces. 112 // Interfaces are types, not classes. They should not have access to 113 // protected members in j.l.Object, even though it is their superclass. 114 if ((mods & STATIC) != 0 && 115 !isRelatedClass(refc, lookupClass)) 116 return false; 117 if ((allowedModes & PROTECTED) != 0 && 118 isSubClass(lookupClass, defc)) 119 return true; 120 return false; 121 case PACKAGE_ONLY: // That is, zero. Unmarked member is package-only access. 122 assert !defc.isInterface(); // package-private members aren't allowed in interfaces 123 return ((allowedModes & PACKAGE_ALLOWED) != 0 && 124 isSamePackage(defc, lookupClass)); 125 case PRIVATE: 126 // Loosened rules for privates follows access rules for inner classes. 127 return (ALLOW_NESTMATE_ACCESS && 128 (allowedModes & PRIVATE) != 0 && 129 isSamePackageMember(defc, lookupClass)); 130 default: 131 throw new IllegalArgumentException("bad modifiers: "+Modifier.toString(mods)); 132 } 133 } 134 isRelatedClass(Class<?> refc, Class<?> lookupClass)135 static boolean isRelatedClass(Class<?> refc, Class<?> lookupClass) { 136 return (refc == lookupClass || 137 isSubClass(refc, lookupClass) || 138 isSubClass(lookupClass, refc)); 139 } 140 isSubClass(Class<?> lookupClass, Class<?> defc)141 static boolean isSubClass(Class<?> lookupClass, Class<?> defc) { 142 return defc.isAssignableFrom(lookupClass) && 143 !lookupClass.isInterface(); // interfaces are types, not classes. 144 } 145 146 // Android-removed: Use public API instead of getClassModifiers() to check if public. 147 /* 148 static int getClassModifiers(Class<?> c) { 149 // This would return the mask stored by javac for the source-level modifiers. 150 // return c.getModifiers(); 151 // But what we need for JVM access checks are the actual bits from the class header. 152 // ...But arrays and primitives are synthesized with their own odd flags: 153 if (c.isArray() || c.isPrimitive()) 154 return c.getModifiers(); 155 return Reflection.getClassAccessFlags(c); 156 } 157 */ 158 159 /** 160 * Evaluate the JVM linkage rules for access to the given class on behalf of caller. 161 * <h3>JVM Specification, 5.4.4 "Access Control"</h3> 162 * A class or interface C is accessible to a class or interface D 163 * if and only if either of the following conditions are true:<ul> 164 * <li>C is public. 165 * <li>C and D are members of the same runtime package. 166 * </ul> 167 * @param refc the symbolic reference class to which access is being checked (C) 168 * @param lookupClass the class performing the lookup (D) 169 */ isClassAccessible(Class<?> refc, Class<?> lookupClass, int allowedModes)170 public static boolean isClassAccessible(Class<?> refc, Class<?> lookupClass, 171 int allowedModes) { 172 if (allowedModes == 0) return false; 173 // Android-changed: Use public API instead of getClassModifiers() to check if public. 174 /* 175 assert((allowedModes & PUBLIC) != 0 && 176 (allowedModes & ~(ALL_ACCESS_MODES|PACKAGE_ALLOWED)) == 0); 177 int mods = getClassModifiers(refc); 178 if (isPublic(mods)) 179 */ 180 if (Modifier.isPublic(refc.getModifiers())) 181 return true; 182 if ((allowedModes & PACKAGE_ALLOWED) != 0 && 183 isSamePackage(lookupClass, refc)) 184 return true; 185 return false; 186 } 187 188 // Android-removed: Unused method. 189 /* 190 /** 191 * Decide if the given method type, attributed to a member or symbolic 192 * reference of a given reference class, is really visible to that class. 193 * @param type the supposed type of a member or symbolic reference of refc 194 * @param refc the class attempting to make the reference 195 * 196 public static boolean isTypeVisible(Class<?> type, Class<?> refc) { 197 if (type == refc) { 198 return true; // easy check 199 } 200 while (type.isArray()) type = type.getComponentType(); 201 if (type.isPrimitive() || type == Object.class) { 202 return true; 203 } 204 ClassLoader typeLoader = type.getClassLoader(); 205 ClassLoader refcLoader = refc.getClassLoader(); 206 if (typeLoader == refcLoader) { 207 return true; 208 } 209 if (refcLoader == null && typeLoader != null) { 210 return false; 211 } 212 if (typeLoader == null && type.getName().startsWith("java.")) { 213 // Note: The API for actually loading classes, ClassLoader.defineClass, 214 // guarantees that classes with names beginning "java." cannot be aliased, 215 // because class loaders cannot load them directly. 216 return true; 217 } 218 219 // Do it the hard way: Look up the type name from the refc loader. 220 // 221 // Force the refc loader to report and commit to a particular binding for this type name (type.getName()). 222 // 223 // In principle, this query might force the loader to load some unrelated class, 224 // which would cause this query to fail (and the original caller to give up). 225 // This would be wasted effort, but it is expected to be very rare, occurring 226 // only when an attacker is attempting to create a type alias. 227 // In the normal case, one class loader will simply delegate to the other, 228 // and the same type will be visible through both, with no extra loading. 229 // 230 // It is important to go through Class.forName instead of ClassLoader.loadClass 231 // because Class.forName goes through the JVM system dictionary, which records 232 // the class lookup once for all. This means that even if a not-well-behaved class loader 233 // would "change its mind" about the meaning of the name, the Class.forName request 234 // will use the result cached in the JVM system dictionary. Note that the JVM system dictionary 235 // will record the first successful result. Unsuccessful results are not stored. 236 // 237 // We use doPrivileged in order to allow an unprivileged caller to ask an arbitrary 238 // class loader about the binding of the proposed name (type.getName()). 239 // The looked up type ("res") is compared for equality against the proposed 240 // type ("type") and then is discarded. Thus, the worst that can happen to 241 // the "child" class loader is that it is bothered to load and report a class 242 // that differs from "type"; this happens once due to JVM system dictionary 243 // memoization. And the caller never gets to look at the alternate type binding 244 // ("res"), whether it exists or not. 245 final String name = type.getName(); 246 Class<?> res = java.security.AccessController.doPrivileged( 247 new java.security.PrivilegedAction<Class>() { 248 public Class<?> run() { 249 try { 250 return Class.forName(name, false, refcLoader); 251 } catch (ClassNotFoundException | LinkageError e) { 252 return null; // Assume the class is not found 253 } 254 } 255 }); 256 return (type == res); 257 } 258 259 /** 260 * Decide if the given method type, attributed to a member or symbolic 261 * reference of a given reference class, is really visible to that class. 262 * @param type the supposed type of a member or symbolic reference of refc 263 * @param refc the class attempting to make the reference 264 * 265 public static boolean isTypeVisible(java.lang.invoke.MethodType type, Class<?> refc) { 266 for (int n = -1, max = type.parameterCount(); n < max; n++) { 267 Class<?> ptype = (n < 0 ? type.returnType() : type.parameterType(n)); 268 if (!isTypeVisible(ptype, refc)) 269 return false; 270 } 271 return true; 272 } 273 */ 274 275 /** 276 * Test if two classes have the same class loader and package qualifier. 277 * @param class1 a class 278 * @param class2 another class 279 * @return whether they are in the same package 280 */ isSamePackage(Class<?> class1, Class<?> class2)281 public static boolean isSamePackage(Class<?> class1, Class<?> class2) { 282 // Android-changed: Throw IAE (instead of asserting) if called with array classes. 283 // assert(!class1.isArray() && !class2.isArray()); 284 if (class1.isArray() || class2.isArray()) { 285 throw new IllegalArgumentException(); 286 } 287 288 if (class1 == class2) 289 return true; 290 if (class1.getClassLoader() != class2.getClassLoader()) 291 return false; 292 String name1 = class1.getName(), name2 = class2.getName(); 293 int dot = name1.lastIndexOf('.'); 294 if (dot != name2.lastIndexOf('.')) 295 return false; 296 for (int i = 0; i < dot; i++) { 297 if (name1.charAt(i) != name2.charAt(i)) 298 return false; 299 } 300 return true; 301 } 302 303 // Android-removed: Unused method. 304 /* 305 /** Return the package name for this class. 306 * 307 public static String getPackageName(Class<?> cls) { 308 assert(!cls.isArray()); 309 String name = cls.getName(); 310 int dot = name.lastIndexOf('.'); 311 if (dot < 0) return ""; 312 return name.substring(0, dot); 313 } 314 */ 315 316 /** 317 * Test if two classes are defined as part of the same package member (top-level class). 318 * If this is true, they can share private access with each other. 319 * @param class1 a class 320 * @param class2 another class 321 * @return whether they are identical or nested together 322 */ isSamePackageMember(Class<?> class1, Class<?> class2)323 public static boolean isSamePackageMember(Class<?> class1, Class<?> class2) { 324 if (class1 == class2) 325 return true; 326 if (!isSamePackage(class1, class2)) 327 return false; 328 if (getOutermostEnclosingClass(class1) != getOutermostEnclosingClass(class2)) 329 return false; 330 return true; 331 } 332 getOutermostEnclosingClass(Class<?> c)333 private static Class<?> getOutermostEnclosingClass(Class<?> c) { 334 Class<?> pkgmem = c; 335 for (Class<?> enc = c; (enc = enc.getEnclosingClass()) != null; ) 336 pkgmem = enc; 337 return pkgmem; 338 } 339 340 // Android-removed: Unused method. 341 /* 342 private static boolean loadersAreRelated(ClassLoader loader1, ClassLoader loader2, 343 boolean loader1MustBeParent) { 344 if (loader1 == loader2 || loader1 == null 345 || (loader2 == null && !loader1MustBeParent)) { 346 return true; 347 } 348 for (ClassLoader scan2 = loader2; 349 scan2 != null; scan2 = scan2.getParent()) { 350 if (scan2 == loader1) return true; 351 } 352 if (loader1MustBeParent) return false; 353 // see if loader2 is a parent of loader1: 354 for (ClassLoader scan1 = loader1; 355 scan1 != null; scan1 = scan1.getParent()) { 356 if (scan1 == loader2) return true; 357 } 358 return false; 359 } 360 */ 361 362 // Android-removed: Unused method. 363 /* 364 /** 365 * Is the class loader of parentClass identical to, or an ancestor of, 366 * the class loader of childClass? 367 * @param parentClass a class 368 * @param childClass another class, which may be a descendent of the first class 369 * @return whether parentClass precedes or equals childClass in class loader order 370 * 371 public static boolean classLoaderIsAncestor(Class<?> parentClass, Class<?> childClass) { 372 return loadersAreRelated(parentClass.getClassLoader(), childClass.getClassLoader(), true); 373 } 374 */ 375 } 376