VerifyAccess.java revision 13901:b2a69d66dc65
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 26package sun.invoke.util; 27 28import java.lang.reflect.Modifier; 29import static java.lang.reflect.Modifier.*; 30import java.lang.reflect.Module; 31import sun.reflect.Reflection; 32 33/** 34 * This class centralizes information about the JVM's linkage access control. 35 * @author jrose 36 */ 37public class VerifyAccess { 38 39 private VerifyAccess() { } // cannot instantiate 40 41 private static final int MODULE_ALLOWED = java.lang.invoke.MethodHandles.Lookup.MODULE; 42 private static final int PACKAGE_ONLY = 0; 43 private static final int PACKAGE_ALLOWED = java.lang.invoke.MethodHandles.Lookup.PACKAGE; 44 private static final int PROTECTED_OR_PACKAGE_ALLOWED = (PACKAGE_ALLOWED|PROTECTED); 45 private static final int ALL_ACCESS_MODES = (PUBLIC|PRIVATE|PROTECTED|PACKAGE_ONLY); 46 private static final boolean ALLOW_NESTMATE_ACCESS = false; 47 48 /** 49 * Evaluate the JVM linkage rules for access to the given method 50 * on behalf of a caller class which proposes to perform the access. 51 * Return true if the caller class has privileges to invoke a method 52 * or access a field with the given properties. 53 * This requires an accessibility check of the referencing class, 54 * plus an accessibility check of the member within the class, 55 * which depends on the member's modifier flags. 56 * <p> 57 * The relevant properties include the defining class ({@code defc}) 58 * of the member, and its modifier flags ({@code mods}). 59 * Also relevant is the class used to make the initial symbolic reference 60 * to the member ({@code refc}). If this latter class is not distinguished, 61 * the defining class should be passed for both arguments ({@code defc == refc}). 62 * <h3>JVM Specification, 5.4.4 "Access Control"</h3> 63 * A field or method R is accessible to a class or interface D if 64 * and only if any of the following conditions is true:<ul> 65 * <li>R is public. 66 * <li>R is protected and is declared in a class C, and D is either 67 * a subclass of C or C itself. Furthermore, if R is not 68 * static, then the symbolic reference to R must contain a 69 * symbolic reference to a class T, such that T is either a 70 * subclass of D, a superclass of D or D itself. 71 * <li>R is either protected or has default access (that is, 72 * neither public nor protected nor private), and is declared 73 * by a class in the same runtime package as D. 74 * <li>R is private and is declared in D. 75 * </ul> 76 * This discussion of access control omits a related restriction 77 * on the target of a protected field access or method invocation 78 * (the target must be of class D or a subtype of D). That 79 * requirement is checked as part of the verification process 80 * (5.4.1); it is not part of link-time access control. 81 * @param refc the class used in the symbolic reference to the proposed member 82 * @param defc the class in which the proposed member is actually defined 83 * @param mods modifier flags for the proposed member 84 * @param lookupClass the class for which the access check is being made 85 * @return true iff the accessing class can access such a member 86 */ 87 public static boolean isMemberAccessible(Class<?> refc, // symbolic ref class 88 Class<?> defc, // actual def class 89 int mods, // actual member mods 90 Class<?> lookupClass, 91 int allowedModes) { 92 if (allowedModes == 0) return false; 93 assert((allowedModes & PUBLIC) != 0 && 94 (allowedModes & ~(ALL_ACCESS_MODES|PACKAGE_ALLOWED|MODULE_ALLOWED)) == 0); 95 // The symbolic reference class (refc) must always be fully verified. 96 if (!isClassAccessible(refc, lookupClass, allowedModes)) { 97 return false; 98 } 99 // Usually refc and defc are the same, but verify defc also in case they differ. 100 if (defc == lookupClass && 101 (allowedModes & PRIVATE) != 0) 102 return true; // easy check; all self-access is OK 103 switch (mods & ALL_ACCESS_MODES) { 104 case PUBLIC: 105 return true; // already checked above 106 case PROTECTED: 107 assert !defc.isInterface(); // protected members aren't allowed in interfaces 108 if ((allowedModes & PROTECTED_OR_PACKAGE_ALLOWED) != 0 && 109 isSamePackage(defc, lookupClass)) 110 return true; 111 if ((allowedModes & PROTECTED) == 0) 112 return false; 113 // Protected members are accessible by subclasses, which does not include interfaces. 114 // Interfaces are types, not classes. They should not have access to 115 // protected members in j.l.Object, even though it is their superclass. 116 if ((mods & STATIC) != 0 && 117 !isRelatedClass(refc, lookupClass)) 118 return false; 119 if ((allowedModes & PROTECTED) != 0 && 120 isSubClass(lookupClass, defc)) 121 return true; 122 return false; 123 case PACKAGE_ONLY: // That is, zero. Unmarked member is package-only access. 124 assert !defc.isInterface(); // package-private members aren't allowed in interfaces 125 return ((allowedModes & PACKAGE_ALLOWED) != 0 && 126 isSamePackage(defc, lookupClass)); 127 case PRIVATE: 128 // Loosened rules for privates follows access rules for inner classes. 129 return (ALLOW_NESTMATE_ACCESS && 130 (allowedModes & PRIVATE) != 0 && 131 isSamePackageMember(defc, lookupClass)); 132 default: 133 throw new IllegalArgumentException("bad modifiers: "+Modifier.toString(mods)); 134 } 135 } 136 137 static boolean isRelatedClass(Class<?> refc, Class<?> lookupClass) { 138 return (refc == lookupClass || 139 isSubClass(refc, lookupClass) || 140 isSubClass(lookupClass, refc)); 141 } 142 143 static boolean isSubClass(Class<?> lookupClass, Class<?> defc) { 144 return defc.isAssignableFrom(lookupClass) && 145 !lookupClass.isInterface(); // interfaces are types, not classes. 146 } 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 * Evaluate the JVM linkage rules for access to the given class on behalf of caller. 160 * <h3>JVM Specification, 5.4.4 "Access Control"</h3> 161 * A class or interface C is accessible to a class or interface D 162 * if and only if any of the following conditions are true:<ul> 163 * <li>C is public and in the same module as D. 164 * <li>D is in a module that reads the module containing C, C is public and in a 165 * package that is exported to the module that contains D. 166 * <li>C and D are members of the same runtime package. 167 * </ul> 168 * @param refc the symbolic reference class to which access is being checked (C) 169 * @param lookupClass the class performing the lookup (D) 170 */ 171 public static boolean isClassAccessible(Class<?> refc, Class<?> lookupClass, 172 int allowedModes) { 173 if (allowedModes == 0) return false; 174 assert((allowedModes & PUBLIC) != 0 && 175 (allowedModes & ~(ALL_ACCESS_MODES|PACKAGE_ALLOWED|MODULE_ALLOWED)) == 0); 176 int mods = getClassModifiers(refc); 177 if (isPublic(mods)) { 178 179 Module lookupModule = lookupClass.getModule(); 180 Module refModule = refc.getModule(); 181 182 // early VM startup case, java.base not defined 183 if (lookupModule == null) { 184 assert refModule == null; 185 return true; 186 } 187 188 // trivially allow 189 if ((allowedModes & MODULE_ALLOWED) != 0 && 190 (lookupModule == refModule)) 191 return true; 192 193 // check readability 194 if (lookupModule.canRead(refModule)) { 195 196 // check that refc is in an exported package 197 Class<?> c = refc; 198 while (c.isArray()) { 199 c = c.getComponentType(); 200 } 201 if (c.isPrimitive()) 202 return true; 203 if ((allowedModes & MODULE_ALLOWED) != 0) { 204 if (refModule.isExported(c.getPackageName(), lookupModule)) 205 return true; 206 } else { 207 // exported unconditionally 208 if (refModule.isExported(c.getPackageName())) 209 return true; 210 } 211 212 // not exported but allow access during VM initialization 213 // because java.base does not have its exports setup 214 if (!jdk.internal.misc.VM.isModuleSystemInited()) 215 return true; 216 } 217 218 // public class not accessible to lookupClass 219 return false; 220 } 221 if ((allowedModes & PACKAGE_ALLOWED) != 0 && 222 isSamePackage(lookupClass, refc)) 223 return true; 224 return false; 225 } 226 227 /** 228 * Decide if the given method type, attributed to a member or symbolic 229 * reference of a given reference class, is really visible to that class. 230 * @param type the supposed type of a member or symbolic reference of refc 231 * @param refc the class attempting to make the reference 232 */ 233 public static boolean isTypeVisible(Class<?> type, Class<?> refc) { 234 if (type == refc) return true; // easy check 235 while (type.isArray()) type = type.getComponentType(); 236 if (type.isPrimitive() || type == Object.class) return true; 237 ClassLoader parent = type.getClassLoader(); 238 if (parent == null) return true; 239 ClassLoader child = refc.getClassLoader(); 240 if (child == null) return false; 241 if (parent == child || loadersAreRelated(parent, child, true)) 242 return true; 243 // Do it the hard way: Look up the type name from the refc loader. 244 try { 245 Class<?> res = child.loadClass(type.getName()); 246 return (type == res); 247 } catch (ClassNotFoundException ex) { 248 return false; 249 } 250 } 251 252 /** 253 * Decide if the given method type, attributed to a member or symbolic 254 * reference of a given reference class, is really visible to that class. 255 * @param type the supposed type of a member or symbolic reference of refc 256 * @param refc the class attempting to make the reference 257 */ 258 public static boolean isTypeVisible(java.lang.invoke.MethodType type, Class<?> refc) { 259 for (int n = -1, max = type.parameterCount(); n < max; n++) { 260 Class<?> ptype = (n < 0 ? type.returnType() : type.parameterType(n)); 261 if (!isTypeVisible(ptype, refc)) 262 return false; 263 } 264 return true; 265 } 266 267 /** 268 * Tests if two classes are in the same module. 269 * @param class1 a class 270 * @param class2 another class 271 * @return whether they are in the same module 272 */ 273 public static boolean isSameModule(Class<?> class1, Class<?> class2) { 274 return class1.getModule() == class2.getModule(); 275 } 276 277 /** 278 * Test if two classes have the same class loader and package qualifier. 279 * @param class1 a class 280 * @param class2 another class 281 * @return whether they are in the same package 282 */ 283 public static boolean isSamePackage(Class<?> class1, Class<?> class2) { 284 assert(!class1.isArray() && !class2.isArray()); 285 if (class1 == class2) 286 return true; 287 if (class1.getClassLoader() != class2.getClassLoader()) 288 return false; 289 String name1 = class1.getName(), name2 = class2.getName(); 290 int dot = name1.lastIndexOf('.'); 291 if (dot != name2.lastIndexOf('.')) 292 return false; 293 for (int i = 0; i < dot; i++) { 294 if (name1.charAt(i) != name2.charAt(i)) 295 return false; 296 } 297 return true; 298 } 299 300 /** Return the package name for this class. 301 */ 302 public static String getPackageName(Class<?> cls) { 303 assert (!cls.isArray()); 304 String name = cls.getName(); 305 int dot = name.lastIndexOf('.'); 306 if (dot < 0) return ""; 307 return name.substring(0, dot); 308 } 309 310 /** 311 * Test if two classes are defined as part of the same package member (top-level class). 312 * If this is true, they can share private access with each other. 313 * @param class1 a class 314 * @param class2 another class 315 * @return whether they are identical or nested together 316 */ 317 public static boolean isSamePackageMember(Class<?> class1, Class<?> class2) { 318 if (class1 == class2) 319 return true; 320 if (!isSamePackage(class1, class2)) 321 return false; 322 if (getOutermostEnclosingClass(class1) != getOutermostEnclosingClass(class2)) 323 return false; 324 return true; 325 } 326 327 private static Class<?> getOutermostEnclosingClass(Class<?> c) { 328 Class<?> pkgmem = c; 329 for (Class<?> enc = c; (enc = enc.getEnclosingClass()) != null; ) 330 pkgmem = enc; 331 return pkgmem; 332 } 333 334 private static boolean loadersAreRelated(ClassLoader loader1, ClassLoader loader2, 335 boolean loader1MustBeParent) { 336 if (loader1 == loader2 || loader1 == null 337 || (loader2 == null && !loader1MustBeParent)) { 338 return true; 339 } 340 for (ClassLoader scan2 = loader2; 341 scan2 != null; scan2 = scan2.getParent()) { 342 if (scan2 == loader1) return true; 343 } 344 if (loader1MustBeParent) return false; 345 // see if loader2 is a parent of loader1: 346 for (ClassLoader scan1 = loader1; 347 scan1 != null; scan1 = scan1.getParent()) { 348 if (scan1 == loader2) return true; 349 } 350 return false; 351 } 352 353 /** 354 * Is the class loader of parentClass identical to, or an ancestor of, 355 * the class loader of childClass? 356 * @param parentClass a class 357 * @param childClass another class, which may be a descendent of the first class 358 * @return whether parentClass precedes or equals childClass in class loader order 359 */ 360 public static boolean classLoaderIsAncestor(Class<?> parentClass, Class<?> childClass) { 361 return loadersAreRelated(parentClass.getClassLoader(), childClass.getClassLoader(), true); 362 } 363} 364