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| 1 | /* | ||
| 2 | * Copyright (c) 2008, 2011, 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.anon; | ||
| 27 | |||
| 28 | import java.io.IOException; | ||
| 29 | import java.lang.reflect.InvocationTargetException; | ||
| 30 | import java.lang.reflect.Method; | ||
| 31 | import sun.misc.IOUtils; | ||
| 32 | |||
| 33 | /** | ||
| 34 | * Anonymous class loader. Will load any valid classfile, producing | ||
| 35 | * a {@link Class} metaobject, without installing that class in the | ||
| 36 | * system dictionary. Therefore, {@link Class#forName(String)} will never | ||
| 37 | * produce a reference to an anonymous class. | ||
| 38 | * <p> | ||
| 39 | * The access permissions of the anonymous class are borrowed from | ||
| 40 | * a <em>host class</em>. The new class behaves as if it were an | ||
| 41 | * inner class of the host class. It can access the host's private | ||
| 42 | * members, if the creator of the class loader has permission to | ||
| 43 | * do so (or to create accessible reflective objects). | ||
| 44 | * <p> | ||
| 45 | * When the anonymous class is loaded, elements of its constant pool | ||
| 46 | * can be patched to new values. This provides a hook to pre-resolve | ||
| 47 | * named classes in the constant pool to other classes, including | ||
| 48 | * anonymous ones. Also, string constants can be pre-resolved to | ||
| 49 | * any reference. (The verifier treats non-string, non-class reference | ||
| 50 | * constants as plain objects.) | ||
| 51 | * <p> | ||
| 52 | * Why include the patching function? It makes some use cases much easier. | ||
| 53 | * Second, the constant pool needed some internal patching anyway, | ||
| 54 | * to anonymize the loaded class itself. Finally, if you are going | ||
| 55 | * to use this seriously, you'll want to build anonymous classes | ||
| 56 | * on top of pre-existing anonymous classes, and that requires patching. | ||
| 57 | * | ||
| 58 | * <p>%%% TO-DO: | ||
| 59 | * <ul> | ||
| 60 | * <li>needs better documentation</li> | ||
| 61 | * <li>needs more security work (for safe delegation)</li> | ||
| 62 | * <li>needs a clearer story about error processing</li> | ||
| 63 | * <li>patch member references also (use ';' as delimiter char)</li> | ||
| 64 | * <li>patch method references to (conforming) method handles</li> | ||
| 65 | * </ul> | ||
| 66 | * | ||
| 67 | * @author jrose | ||
| 68 | * @author Remi Forax | ||
| 69 | * @see <a href="http://blogs.sun.com/jrose/entry/anonymous_classes_in_the_vm"> | ||
| 70 | * http://blogs.sun.com/jrose/entry/anonymous_classes_in_the_vm</a> | ||
| 71 | */ | ||
| 72 | |||
| 73 | public class AnonymousClassLoader { | ||
| 74 | final Class<?> hostClass; | ||
| 75 | |||
| 76 | // Note: Do not refactor the calls to checkHostClass unless you | ||
| 77 | // also adjust this constant: | ||
| 78 | private static int CHC_CALLERS = 3; | ||
| 79 | |||
| 80 | public AnonymousClassLoader() { | ||
| 81 | this.hostClass = checkHostClass(null); | ||
| 82 | } | ||
| 83 | public AnonymousClassLoader(Class<?> hostClass) { | ||
| 84 | this.hostClass = checkHostClass(hostClass); | ||
| 85 | } | ||
| 86 | |||
| 87 | private static Class<?> getTopLevelClass(Class<?> clazz) { | ||
| 88 | for(Class<?> outer = clazz.getDeclaringClass(); outer != null; | ||
| 89 | outer = outer.getDeclaringClass()) { | ||
| 90 | clazz = outer; | ||
| 91 | } | ||
| 92 | return clazz; | ||
| 93 | } | ||
| 94 | |||
| 95 | private static Class<?> checkHostClass(Class<?> hostClass) { | ||
| 96 | // called only from the constructor | ||
| 97 | // does a context-sensitive check on caller class | ||
| 98 | // CC[0..3] = {Reflection, this.checkHostClass, this.<init>, caller} | ||
| 99 | Class<?> caller = sun.reflect.Reflection.getCallerClass(CHC_CALLERS); | ||
| 100 | |||
| 101 | if (caller == null) { | ||
| 102 | // called from the JVM directly | ||
| 103 | if (hostClass == null) | ||
| 104 | return AnonymousClassLoader.class; // anything central will do | ||
| 105 | return hostClass; | ||
| 106 | } | ||
| 107 | |||
| 108 | if (hostClass == null) | ||
| 109 | hostClass = caller; // default value is caller itself | ||
| 110 | |||
| 111 | // anonymous class will access hostClass on behalf of caller | ||
| 112 | Class<?> callee = hostClass; | ||
| 113 | |||
| 114 | if (caller == callee) | ||
| 115 | // caller can always nominate itself to grant caller's own access rights | ||
| 116 | return hostClass; | ||
| 117 | |||
| 118 | // normalize caller and callee to their top-level classes: | ||
| 119 | caller = getTopLevelClass(caller); | ||
| 120 | callee = getTopLevelClass(callee); | ||
| 121 | if (caller == callee) | ||
| 122 | return caller; | ||
| 123 | |||
| 124 | ClassLoader callerCL = caller.getClassLoader(); | ||
| 125 | if (callerCL == null) { | ||
| 126 | // caller is trusted code, so accept the proposed hostClass | ||
| 127 | return hostClass; | ||
| 128 | } | ||
| 129 | |||
| 130 | // %%% should do something with doPrivileged, because trusted | ||
| 131 | // code should have a way to execute on behalf of | ||
| 132 | // partially-trusted clients | ||
| 133 | |||
| 134 | // Does the caller have the right to access the private | ||
| 135 | // members of the callee? If not, raise an error. | ||
| 136 | final int ACC_PRIVATE = 2; | ||
| 137 | try { | ||
| 138 | sun.reflect.Reflection.ensureMemberAccess(caller, callee, null, ACC_PRIVATE); | ||
| 139 | } catch (IllegalAccessException ee) { | ||
| 140 | throw new IllegalArgumentException(ee); | ||
| 141 | } | ||
| 142 | |||
| 143 | return hostClass; | ||
| 144 | } | ||
| 145 | |||
| 146 | public Class<?> loadClass(byte[] classFile) { | ||
| 147 | if (defineAnonymousClass == null) { | ||
| 148 | // no JVM support; try to fake an approximation | ||
| 149 | try { | ||
| 150 | return fakeLoadClass(new ConstantPoolParser(classFile).createPatch()); | ||
| 151 | } catch (InvalidConstantPoolFormatException ee) { | ||
| 152 | throw new IllegalArgumentException(ee); | ||
| 153 | } | ||
| 154 | } | ||
| 155 | return loadClass(classFile, null); | ||
| 156 | } | ||
| 157 | |||
| 158 | public Class<?> loadClass(ConstantPoolPatch classPatch) { | ||
| 159 | if (defineAnonymousClass == null) { | ||
| 160 | // no JVM support; try to fake an approximation | ||
| 161 | return fakeLoadClass(classPatch); | ||
| 162 | } | ||
| 163 | Object[] patches = classPatch.patchArray; | ||
| 164 | // Convert class names (this late in the game) | ||
| 165 | // to use slash '/' instead of dot '.'. | ||
| 166 | // Java likes dots, but the JVM likes slashes. | ||
| 167 | for (int i = 0; i < patches.length; i++) { | ||
| 168 | Object value = patches[i]; | ||
| 169 | if (value != null) { | ||
| 170 | byte tag = classPatch.getTag(i); | ||
| 171 | switch (tag) { | ||
| 172 | case ConstantPoolVisitor.CONSTANT_Class: | ||
| 173 | if (value instanceof String) { | ||
| 174 | if (patches == classPatch.patchArray) | ||
| 175 | patches = patches.clone(); | ||
| 176 | patches[i] = ((String)value).replace('.', '/'); | ||
| 177 | } | ||
| 178 | break; | ||
| 179 | case ConstantPoolVisitor.CONSTANT_Fieldref: | ||
| 180 | case ConstantPoolVisitor.CONSTANT_Methodref: | ||
| 181 | case ConstantPoolVisitor.CONSTANT_InterfaceMethodref: | ||
| 182 | case ConstantPoolVisitor.CONSTANT_NameAndType: | ||
| 183 | // When/if the JVM supports these patches, | ||
| 184 | // we'll probably need to reformat them also. | ||
| 185 | // Meanwhile, let the class loader create the error. | ||
| 186 | break; | ||
| 187 | } | ||
| 188 | } | ||
| 189 | } | ||
| 190 | return loadClass(classPatch.outer.classFile, classPatch.patchArray); | ||
| 191 | } | ||
| 192 | |||
| 193 | private Class<?> loadClass(byte[] classFile, Object[] patchArray) { | ||
| 194 | try { | ||
| 195 | return (Class<?>) | ||
| 196 | defineAnonymousClass.invoke(unsafe, | ||
| 197 | hostClass, classFile, patchArray); | ||
| 198 | } catch (Exception ex) { | ||
| 199 | throwReflectedException(ex); | ||
| 200 | throw new RuntimeException("error loading into "+hostClass, ex); | ||
| 201 | } | ||
| 202 | } | ||
| 203 | |||
| 204 | private static void throwReflectedException(Exception ex) { | ||
| 205 | if (ex instanceof InvocationTargetException) { | ||
| 206 | Throwable tex = ((InvocationTargetException)ex).getTargetException(); | ||
| 207 | if (tex instanceof Error) | ||
| 208 | throw (Error) tex; | ||
| 209 | ex = (Exception) tex; | ||
| 210 | } | ||
| 211 | if (ex instanceof RuntimeException) { | ||
| 212 | throw (RuntimeException) ex; | ||
| 213 | } | ||
| 214 | } | ||
| 215 | |||
| 216 | private Class<?> fakeLoadClass(ConstantPoolPatch classPatch) { | ||
| 217 | // Implementation: | ||
| 218 | // 1. Make up a new name nobody has used yet. | ||
| 219 | // 2. Inspect the tail-header of the class to find the this_class index. | ||
| 220 | // 3. Patch the CONSTANT_Class for this_class to the new name. | ||
| 221 | // 4. Add other CP entries required by (e.g.) string patches. | ||
| 222 | // 5. Flatten Class constants down to their names, making sure that | ||
| 223 | // the host class loader can pick them up again accurately. | ||
| 224 | // 6. Generate the edited class file bytes. | ||
| 225 | // | ||
| 226 | // Potential limitations: | ||
| 227 | // * The class won't be truly anonymous, and may interfere with others. | ||
| 228 | // * Flattened class constants might not work, because of loader issues. | ||
| 229 | // * Pseudo-string constants will not flatten down to real strings. | ||
| 230 | // * Method handles will (of course) fail to flatten to linkage strings. | ||
| 231 | if (true) throw new UnsupportedOperationException("NYI"); | ||
| 232 | Object[] cpArray; | ||
| 233 | try { | ||
| 234 | cpArray = classPatch.getOriginalCP(); | ||
| 235 | } catch (InvalidConstantPoolFormatException ex) { | ||
| 236 | throw new RuntimeException(ex); | ||
| 237 | } | ||
| 238 | int thisClassIndex = classPatch.getParser().getThisClassIndex(); | ||
| 239 | String thisClassName = (String) cpArray[thisClassIndex]; | ||
| 240 | synchronized (AnonymousClassLoader.class) { | ||
| 241 | thisClassName = thisClassName+"\\|"+(++fakeNameCounter); | ||
| 242 | } | ||
| 243 | classPatch.putUTF8(thisClassIndex, thisClassName); | ||
| 244 | byte[] classFile = null; | ||
| 245 | return unsafe.defineClass(null, classFile, 0, classFile.length, | ||
| 246 | hostClass.getClassLoader(), | ||
| 247 | hostClass.getProtectionDomain()); | ||
| 248 | } | ||
| 249 | private static int fakeNameCounter = 99999; | ||
| 250 | |||
| 251 | // ignore two warnings on this line: | ||
| 252 | static sun.misc.Unsafe unsafe = sun.misc.Unsafe.getUnsafe(); | ||
| 253 | // preceding line requires that this class be on the boot class path | ||
| 254 | |||
| 255 | static private final Method defineAnonymousClass; | ||
| 256 | static { | ||
| 257 | Method dac = null; | ||
| 258 | Class<? extends sun.misc.Unsafe> unsafeClass = unsafe.getClass(); | ||
| 259 | try { | ||
| 260 | dac = unsafeClass.getMethod("defineAnonymousClass", | ||
| 261 | Class.class, | ||
| 262 | byte[].class, | ||
| 263 | Object[].class); | ||
| 264 | } catch (Exception ee) { | ||
| 265 | dac = null; | ||
| 266 | } | ||
| 267 | defineAnonymousClass = dac; | ||
| 268 | } | ||
| 269 | |||
| 270 | private static void noJVMSupport() { | ||
| 271 | throw new UnsupportedOperationException("no JVM support for anonymous classes"); | ||
| 272 | } | ||
| 273 | |||
| 274 | |||
| 275 | private static native Class<?> loadClassInternal(Class<?> hostClass, | ||
| 276 | byte[] classFile, | ||
| 277 | Object[] patchArray); | ||
| 278 | |||
| 279 | public static byte[] readClassFile(Class<?> templateClass) throws IOException { | ||
| 280 | String templateName = templateClass.getName(); | ||
| 281 | int lastDot = templateName.lastIndexOf('.'); | ||
| 282 | java.net.URL url = templateClass.getResource(templateName.substring(lastDot+1)+".class"); | ||
| 283 | java.net.URLConnection connection = url.openConnection(); | ||
| 284 | int contentLength = connection.getContentLength(); | ||
| 285 | if (contentLength < 0) | ||
| 286 | throw new IOException("invalid content length "+contentLength); | ||
| 287 | |||
| 288 | return IOUtils.readFully(connection.getInputStream(), contentLength, true); | ||
| 289 | } | ||
| 290 | } | ||