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 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 */ 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 } 134 135 static boolean isRelatedClass(Class<?> refc, Class<?> lookupClass) { 136 return (refc == lookupClass || 137 isSubClass(refc, lookupClass) || 138 isSubClass(lookupClass, refc)); 139 } 140 141 static boolean isSubClass(Class<?> lookupClass, Class<?> defc) { 142 return defc.isAssignableFrom(lookupClass) && 143 !lookupClass.isInterface(); // interfaces are types, not classes. 144 } 145 146 /** 147 * Evaluate the JVM linkage rules for access to the given class on behalf of caller. 148 * <h3>JVM Specification, 5.4.4 "Access Control"</h3> 149 * A class or interface C is accessible to a class or interface D 150 * if and only if either of the following conditions are true:<ul> 151 * <li>C is public. 152 * <li>C and D are members of the same runtime package. 153 * </ul> 154 * @param refc the symbolic reference class to which access is being checked (C) 155 * @param lookupClass the class performing the lookup (D) 156 */ 157 public static boolean isClassAccessible(Class<?> refc, Class<?> lookupClass, 158 int allowedModes) { 159 if (allowedModes == 0) return false; 160 // Android-changed: Use public APIs to figure out whether a class 161 // is public or not. 162 if (Modifier.isPublic(refc.getModifiers())) 163 return true; 164 if ((allowedModes & PACKAGE_ALLOWED) != 0 && 165 isSamePackage(lookupClass, refc)) 166 return true; 167 return false; 168 } 169 170 /** 171 * Decide if the given method type, attributed to a member or symbolic 172 * reference of a given reference class, is really visible to that class. 173 * @param type the supposed type of a member or symbolic reference of refc 174 * @param refc the class attempting to make the reference 175 */ 176 public static boolean isTypeVisible(Class<?> type, Class<?> refc) { 177 if (type == refc) return true; // easy check 178 while (type.isArray()) type = type.getComponentType(); 179 if (type.isPrimitive() || type == Object.class) return true; 180 ClassLoader parent = type.getClassLoader(); 181 if (parent == null) return true; 182 ClassLoader child = refc.getClassLoader(); 183 if (child == null) return false; 184 if (parent == child || loadersAreRelated(parent, child, true)) 185 return true; 186 // Do it the hard way: Look up the type name from the refc loader. 187 try { 188 Class<?> res = child.loadClass(type.getName()); 189 return (type == res); 190 } catch (ClassNotFoundException ex) { 191 return false; 192 } 193 } 194 195 /** 196 * Decide if the given method type, attributed to a member or symbolic 197 * reference of a given reference class, is really visible to that class. 198 * @param type the supposed type of a member or symbolic reference of refc 199 * @param refc the class attempting to make the reference 200 */ 201 public static boolean isTypeVisible(java.lang.invoke.MethodType type, Class<?> refc) { 202 for (int n = -1, max = type.parameterCount(); n < max; n++) { 203 Class<?> ptype = (n < 0 ? type.returnType() : type.parameterType(n)); 204 if (!isTypeVisible(ptype, refc)) 205 return false; 206 } 207 return true; 208 } 209 210 /** 211 * Test if two classes have the same class loader and package qualifier. 212 * @param class1 a class 213 * @param class2 another class 214 * @return whether they are in the same package 215 */ 216 public static boolean isSamePackage(Class<?> class1, Class<?> class2) { 217 // Android-changed: Throw IAE (instead of asserting) if called with array classes. 218 if (class1.isArray() || class2.isArray()) { 219 throw new IllegalArgumentException(); 220 } 221 222 if (class1 == class2) 223 return true; 224 if (class1.getClassLoader() != class2.getClassLoader()) 225 return false; 226 String name1 = class1.getName(), name2 = class2.getName(); 227 int dot = name1.lastIndexOf('.'); 228 if (dot != name2.lastIndexOf('.')) 229 return false; 230 for (int i = 0; i < dot; i++) { 231 if (name1.charAt(i) != name2.charAt(i)) 232 return false; 233 } 234 return true; 235 } 236 237 /** Return the package name for this class. 238 */ 239 public static String getPackageName(Class<?> cls) { 240 assert(!cls.isArray()); 241 String name = cls.getName(); 242 int dot = name.lastIndexOf('.'); 243 if (dot < 0) return ""; 244 return name.substring(0, dot); 245 } 246 247 /** 248 * Test if two classes are defined as part of the same package member (top-level class). 249 * If this is true, they can share private access with each other. 250 * @param class1 a class 251 * @param class2 another class 252 * @return whether they are identical or nested together 253 */ 254 public static boolean isSamePackageMember(Class<?> class1, Class<?> class2) { 255 if (class1 == class2) 256 return true; 257 if (!isSamePackage(class1, class2)) 258 return false; 259 if (getOutermostEnclosingClass(class1) != getOutermostEnclosingClass(class2)) 260 return false; 261 return true; 262 } 263 264 private static Class<?> getOutermostEnclosingClass(Class<?> c) { 265 Class<?> pkgmem = c; 266 for (Class<?> enc = c; (enc = enc.getEnclosingClass()) != null; ) 267 pkgmem = enc; 268 return pkgmem; 269 } 270 271 private static boolean loadersAreRelated(ClassLoader loader1, ClassLoader loader2, 272 boolean loader1MustBeParent) { 273 if (loader1 == loader2 || loader1 == null 274 || (loader2 == null && !loader1MustBeParent)) { 275 return true; 276 } 277 for (ClassLoader scan2 = loader2; 278 scan2 != null; scan2 = scan2.getParent()) { 279 if (scan2 == loader1) return true; 280 } 281 if (loader1MustBeParent) return false; 282 // see if loader2 is a parent of loader1: 283 for (ClassLoader scan1 = loader1; 284 scan1 != null; scan1 = scan1.getParent()) { 285 if (scan1 == loader2) return true; 286 } 287 return false; 288 } 289 290 /** 291 * Is the class loader of parentClass identical to, or an ancestor of, 292 * the class loader of childClass? 293 * @param parentClass a class 294 * @param childClass another class, which may be a descendent of the first class 295 * @return whether parentClass precedes or equals childClass in class loader order 296 */ 297 public static boolean classLoaderIsAncestor(Class<?> parentClass, Class<?> childClass) { 298 return loadersAreRelated(parentClass.getClassLoader(), childClass.getClassLoader(), true); 299 } 300 } 301
