VerifyAccess.java revision 11099:678faa7d1a6a
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 sun.reflect.Reflection; 31 32/** 33 * This class centralizes information about the JVM's linkage access control. 34 * @author jrose 35 */ 36public 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 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 static int getClassModifiers(Class<?> c) { 147 // This would return the mask stored by javac for the source-level modifiers. 148 // return c.getModifiers(); 149 // But what we need for JVM access checks are the actual bits from the class header. 150 // ...But arrays and primitives are synthesized with their own odd flags: 151 if (c.isArray() || c.isPrimitive()) 152 return c.getModifiers(); 153 return Reflection.getClassAccessFlags(c); 154 } 155 156 /** 157 * Evaluate the JVM linkage rules for access to the given class on behalf of caller. 158 * <h3>JVM Specification, 5.4.4 "Access Control"</h3> 159 * A class or interface C is accessible to a class or interface D 160 * if and only if either of the following conditions are true:<ul> 161 * <li>C is public. 162 * <li>C and D are members of the same runtime package. 163 * </ul> 164 * @param refc the symbolic reference class to which access is being checked (C) 165 * @param lookupClass the class performing the lookup (D) 166 */ 167 public static boolean isClassAccessible(Class<?> refc, Class<?> lookupClass, 168 int allowedModes) { 169 if (allowedModes == 0) return false; 170 assert((allowedModes & PUBLIC) != 0 && 171 (allowedModes & ~(ALL_ACCESS_MODES|PACKAGE_ALLOWED)) == 0); 172 int mods = getClassModifiers(refc); 173 if (isPublic(mods)) 174 return true; 175 if ((allowedModes & PACKAGE_ALLOWED) != 0 && 176 isSamePackage(lookupClass, refc)) 177 return true; 178 return false; 179 } 180 181 /** 182 * Decide if the given method type, attributed to a member or symbolic 183 * reference of a given reference class, is really visible to that class. 184 * @param type the supposed type of a member or symbolic reference of refc 185 * @param refc the class attempting to make the reference 186 */ 187 public static boolean isTypeVisible(Class<?> type, Class<?> refc) { 188 if (type == refc) return true; // easy check 189 while (type.isArray()) type = type.getComponentType(); 190 if (type.isPrimitive() || type == Object.class) return true; 191 ClassLoader parent = type.getClassLoader(); 192 if (parent == null) return true; 193 ClassLoader child = refc.getClassLoader(); 194 if (child == null) return false; 195 if (parent == child || loadersAreRelated(parent, child, true)) 196 return true; 197 // Do it the hard way: Look up the type name from the refc loader. 198 try { 199 Class<?> res = child.loadClass(type.getName()); 200 return (type == res); 201 } catch (ClassNotFoundException ex) { 202 return false; 203 } 204 } 205 206 /** 207 * Decide if the given method type, attributed to a member or symbolic 208 * reference of a given reference class, is really visible to that class. 209 * @param type the supposed type of a member or symbolic reference of refc 210 * @param refc the class attempting to make the reference 211 */ 212 public static boolean isTypeVisible(java.lang.invoke.MethodType type, Class<?> refc) { 213 for (int n = -1, max = type.parameterCount(); n < max; n++) { 214 Class<?> ptype = (n < 0 ? type.returnType() : type.parameterType(n)); 215 if (!isTypeVisible(ptype, refc)) 216 return false; 217 } 218 return true; 219 } 220 221 /** 222 * Test if two classes have the same class loader and package qualifier. 223 * @param class1 a class 224 * @param class2 another class 225 * @return whether they are in the same package 226 */ 227 public static boolean isSamePackage(Class<?> class1, Class<?> class2) { 228 assert(!class1.isArray() && !class2.isArray()); 229 if (class1 == class2) 230 return true; 231 if (class1.getClassLoader() != class2.getClassLoader()) 232 return false; 233 String name1 = class1.getName(), name2 = class2.getName(); 234 int dot = name1.lastIndexOf('.'); 235 if (dot != name2.lastIndexOf('.')) 236 return false; 237 for (int i = 0; i < dot; i++) { 238 if (name1.charAt(i) != name2.charAt(i)) 239 return false; 240 } 241 return true; 242 } 243 244 /** Return the package name for this class. 245 */ 246 public static String getPackageName(Class<?> cls) { 247 assert(!cls.isArray()); 248 String name = cls.getName(); 249 int dot = name.lastIndexOf('.'); 250 if (dot < 0) return ""; 251 return name.substring(0, dot); 252 } 253 254 /** 255 * Test if two classes are defined as part of the same package member (top-level class). 256 * If this is true, they can share private access with each other. 257 * @param class1 a class 258 * @param class2 another class 259 * @return whether they are identical or nested together 260 */ 261 public static boolean isSamePackageMember(Class<?> class1, Class<?> class2) { 262 if (class1 == class2) 263 return true; 264 if (!isSamePackage(class1, class2)) 265 return false; 266 if (getOutermostEnclosingClass(class1) != getOutermostEnclosingClass(class2)) 267 return false; 268 return true; 269 } 270 271 private static Class<?> getOutermostEnclosingClass(Class<?> c) { 272 Class<?> pkgmem = c; 273 for (Class<?> enc = c; (enc = enc.getEnclosingClass()) != null; ) 274 pkgmem = enc; 275 return pkgmem; 276 } 277 278 private static boolean loadersAreRelated(ClassLoader loader1, ClassLoader loader2, 279 boolean loader1MustBeParent) { 280 if (loader1 == loader2 || loader1 == null 281 || (loader2 == null && !loader1MustBeParent)) { 282 return true; 283 } 284 for (ClassLoader scan2 = loader2; 285 scan2 != null; scan2 = scan2.getParent()) { 286 if (scan2 == loader1) return true; 287 } 288 if (loader1MustBeParent) return false; 289 // see if loader2 is a parent of loader1: 290 for (ClassLoader scan1 = loader1; 291 scan1 != null; scan1 = scan1.getParent()) { 292 if (scan1 == loader2) return true; 293 } 294 return false; 295 } 296 297 /** 298 * Is the class loader of parentClass identical to, or an ancestor of, 299 * the class loader of childClass? 300 * @param parentClass a class 301 * @param childClass another class, which may be a descendent of the first class 302 * @return whether parentClass precedes or equals childClass in class loader order 303 */ 304 public static boolean classLoaderIsAncestor(Class<?> parentClass, Class<?> childClass) { 305 return loadersAreRelated(parentClass.getClassLoader(), childClass.getClassLoader(), true); 306 } 307} 308