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1: /* Engine -- generic getInstance method. 2: Copyright (C) 2003, 2006 Free Software Foundation, Inc. 3: 4: This file is part of GNU Classpath. 5: 6: GNU Classpath is free software; you can redistribute it and/or modify 7: it under the terms of the GNU General Public License as published by 8: the Free Software Foundation; either version 2, or (at your option) 9: any later version. 10: 11: GNU Classpath is distributed in the hope that it will be useful, but 12: WITHOUT ANY WARRANTY; without even the implied warranty of 13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14: General Public License for more details. 15: 16: You should have received a copy of the GNU General Public License 17: along with GNU Classpath; see the file COPYING. If not, write to the 18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19: 02110-1301 USA. 20: 21: Linking this library statically or dynamically with other modules is 22: making a combined work based on this library. Thus, the terms and 23: conditions of the GNU General Public License cover the whole 24: combination. 25: 26: As a special exception, the copyright holders of this library give you 27: permission to link this library with independent modules to produce an 28: executable, regardless of the license terms of these independent 29: modules, and to copy and distribute the resulting executable under 30: terms of your choice, provided that you also meet, for each linked 31: independent module, the terms and conditions of the license of that 32: module. An independent module is a module which is not derived from 33: or based on this library. If you modify this library, you may extend 34: this exception to your version of the library, but you are not 35: obligated to do so. If you do not wish to do so, delete this 36: exception statement from your version. */ 37: 38: package gnu.java.security; 39: 40: import gnu.java.lang.CPStringBuilder; 41: 42: import java.lang.reflect.Constructor; 43: import java.lang.reflect.InvocationTargetException; 44: 45: import java.security.NoSuchAlgorithmException; 46: import java.security.Provider; 47: import java.util.Enumeration; 48: 49: /** 50: * Generic implementation of the getInstance methods in the various 51: * engine classes in java.security. 52: * <p> 53: * These classes ({@link java.security.Signature} for example) can be 54: * thought of as the "chrome, upholstery, and steering wheel", and the SPI 55: * (service provider interface, e.g. {@link java.security.SignatureSpi}) 56: * classes can be thought of as the "engine" -- providing the actual 57: * functionality of whatever cryptographic algorithm the instance 58: * represents. 59: * 60: * @see Provider 61: * @author Casey Marshall 62: */ 63: public final class Engine 64: { 65: 66: // Constants. 67: // ------------------------------------------------------------------------ 68: 69: /** Prefix for aliases. */ 70: private static final String ALG_ALIAS = "Alg.Alias."; 71: 72: /** Maximum number of aliases to try. */ 73: private static final int MAX_ALIASES = 5; 74: 75: /** Argument list for no-argument constructors. */ 76: private static final Object[] NO_ARGS = new Object[0]; 77: 78: // Constructor. 79: // ------------------------------------------------------------------------ 80: 81: /** This class cannot be instantiated. */ 82: private Engine() { } 83: 84: /** 85: * Return the implementation for <i>algorithm</i> for service <i>service</i> 86: * from <i>provider</i>. The service is e.g. "Signature", and the algorithm 87: * "DSA". 88: * 89: * @param service The service name. 90: * @param algorithm The name of the algorithm to get. 91: * @param provider The provider to get the implementation from. 92: * @return The engine class for the specified algorithm; the object returned 93: * is typically a subclass of the SPI class for that service, but 94: * callers should check that this is so. 95: * @throws NoSuchAlgorithmException If the implementation cannot be found or 96: * cannot be instantiated. 97: * @throws InvocationTargetException If the SPI class's constructor throws an 98: * exception. 99: * @throws IllegalArgumentException If any of the three arguments is null. 100: */ 101: public static Object getInstance(String service, String algorithm, 102: Provider provider) 103: throws InvocationTargetException, NoSuchAlgorithmException 104: { 105: return getInstance(service, algorithm, provider, NO_ARGS); 106: } 107: 108: /** 109: * Return the implementation for <i>algorithm</i> for service <i>service</i> 110: * from <i>provider</i>, passing <i>initArgs</i> to the SPI class's 111: * constructor (which cannot be null; pass a zero-length array if the SPI 112: * takes no arguments). The service is e.g. "Signature", and the algorithm 113: * "DSA". 114: * 115: * @param service The service name. 116: * @param algorithm The name of the algorithm to get. 117: * @param provider The provider to get the implementation from. 118: * @param initArgs The arguments to pass to the SPI class's constructor 119: * (cannot be null). 120: * @return The engine class for the specified algorithm; the object returned 121: * is typically a subclass of the SPI class for that service, but 122: * callers should check that this is so. 123: * @throws NoSuchAlgorithmException If the implementation cannot be found or 124: * cannot be instantiated. 125: * @throws InvocationTargetException If the SPI class's constructor throws an 126: * exception. 127: * @throws IllegalArgumentException If any of the four arguments is 128: * <code>null</code> or if either <code>service</code>, or 129: * <code>algorithm</code> is an empty string. 130: */ 131: public static Object getInstance(String service, String algorithm, 132: Provider provider, Object[] initArgs) 133: throws InvocationTargetException, NoSuchAlgorithmException 134: { 135: if (service == null) 136: throw new IllegalArgumentException("service MUST NOT be null"); 137: service = service.trim(); 138: if (service.length() == 0) 139: throw new IllegalArgumentException("service MUST NOT be empty"); 140: if (algorithm == null) 141: throw new IllegalArgumentException("algorithm MUST NOT be null"); 142: algorithm = algorithm.trim(); 143: if (algorithm.length() == 0) 144: throw new IllegalArgumentException("algorithm MUST NOT be empty"); 145: if (provider == null) 146: throw new IllegalArgumentException("provider MUST NOT be null"); 147: if (initArgs == null) 148: throw new IllegalArgumentException("Constructor's parameters MUST NOT be null"); 149: 150: Enumeration enumer = provider.propertyNames(); 151: String key = null; 152: String alias; 153: int count = 0; 154: boolean algorithmFound = false; 155: CPStringBuilder sb = new CPStringBuilder(); 156: while (enumer.hasMoreElements()) 157: { 158: key = (String) enumer.nextElement(); 159: if (key.equalsIgnoreCase(service + "." + algorithm)) 160: { 161: // remove the service portion from the key 162: algorithm = key.substring(service.length() + 1); 163: algorithmFound = true; 164: break; 165: } 166: else if (key.equalsIgnoreCase(ALG_ALIAS + service + "." + algorithm)) 167: { 168: alias = provider.getProperty(key); 169: if (! algorithm.equalsIgnoreCase(alias)) // does not refer to itself 170: { 171: algorithm = alias; 172: if (count++ > MAX_ALIASES) 173: { 174: sb.append("Algorithm [").append(algorithm) 175: .append("] of type [").append(service) 176: .append("] from provider [").append(provider) 177: .append("] has too many aliases"); 178: throw new NoSuchAlgorithmException(sb.toString()); 179: } 180: // need to reset enumeration to now look for the alias 181: enumer = provider.propertyNames(); 182: } 183: } 184: } 185: 186: if (! algorithmFound) 187: { 188: sb.append("Algorithm [").append(algorithm).append("] of type [") 189: .append(service).append("] from provider [") 190: .append(provider).append("] is not found"); 191: throw new NoSuchAlgorithmException(sb.toString()); 192: } 193: 194: // Find and instantiate the implementation 195: Class clazz = null; 196: ClassLoader loader = provider.getClass().getClassLoader(); 197: Constructor constructor = null; 198: String className = provider.getProperty(key); 199: sb.append("Class [").append(className).append("] for algorithm [") 200: .append(algorithm).append("] of type [").append(service) 201: .append("] from provider [").append(provider).append("] "); 202: Throwable cause = null; 203: try 204: { 205: if (loader != null) 206: clazz = loader.loadClass(className); 207: else 208: clazz = Class.forName(className); 209: constructor = getCompatibleConstructor(clazz, initArgs); 210: return constructor.newInstance(initArgs); 211: } 212: catch (ClassNotFoundException x) 213: { 214: sb.append("cannot not be found"); 215: cause = x; 216: } 217: catch (IllegalAccessException x) 218: { 219: sb.append("cannot be accessed"); 220: cause = x; 221: } 222: catch (InstantiationException x) 223: { 224: sb.append("cannot be instantiated"); 225: cause = x; 226: } 227: catch (ExceptionInInitializerError x) 228: { 229: sb.append("cannot be initialized"); 230: cause = x; 231: } 232: catch (SecurityException x) 233: { 234: sb.append("caused a security violation"); 235: cause = x; 236: } 237: catch (NoSuchMethodException x) 238: { 239: sb.append("does not have/expose an appropriate constructor"); 240: cause = x; 241: } 242: 243: NoSuchAlgorithmException x = new NoSuchAlgorithmException(sb.toString()); 244: x.initCause(cause); 245: throw x; 246: } 247: 248: /** 249: * Find a constructor in the given class that can take the specified 250: * argument list, allowing any of which to be null. 251: * 252: * @param clazz The class from which to get the constructor. 253: * @param initArgs The argument list to be passed to the constructor. 254: * @return The constructor. 255: * @throws NoSuchMethodException If no constructor of the given class 256: * can take the specified argument array. 257: */ 258: private static Constructor getCompatibleConstructor(Class clazz, 259: Object[] initArgs) 260: throws NoSuchMethodException 261: { 262: Constructor[] c = clazz.getConstructors(); 263: outer:for (int i = 0; i < c.length; i++) 264: { 265: Class[] argTypes = c[i].getParameterTypes(); 266: if (argTypes.length != initArgs.length) 267: continue; 268: for (int j = 0; j < argTypes.length; j++) 269: { 270: if (initArgs[j] != null && 271: !argTypes[j].isAssignableFrom(initArgs[j].getClass())) 272: continue outer; 273: } 274: // If we reach this point, we know this constructor (c[i]) has 275: // the same number of parameters as the target parameter list, 276: // and all our parameters are either (1) null, or (2) assignable 277: // to the target parameter type. 278: return c[i]; 279: } 280: throw new NoSuchMethodException(); 281: } 282: }