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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 java.lang.reflect.Constructor; 41: import java.lang.reflect.InvocationTargetException; 42: 43: import java.security.NoSuchAlgorithmException; 44: import java.security.Provider; 45: import java.util.Enumeration; 46: 47: /** 48: * Generic implementation of the getInstance methods in the various 49: * engine classes in java.security. 50: * <p> 51: * These classes ({@link java.security.Signature} for example) can be 52: * thought of as the "chrome, upholstery, and steering wheel", and the SPI 53: * (service provider interface, e.g. {@link java.security.SignatureSpi}) 54: * classes can be thought of as the "engine" -- providing the actual 55: * functionality of whatever cryptographic algorithm the instance 56: * represents. 57: * 58: * @see Provider 59: * @author Casey Marshall 60: */ 61: public final class Engine 62: { 63: 64: // Constants. 65: // ------------------------------------------------------------------------ 66: 67: /** Prefix for aliases. */ 68: private static final String ALG_ALIAS = "Alg.Alias."; 69: 70: /** Maximum number of aliases to try. */ 71: private static final int MAX_ALIASES = 5; 72: 73: /** Argument list for no-argument constructors. */ 74: private static final Object[] NO_ARGS = new Object[0]; 75: 76: // Constructor. 77: // ------------------------------------------------------------------------ 78: 79: /** This class cannot be instantiated. */ 80: private Engine() { } 81: 82: // Class method. 83: // ------------------------------------------------------------------------ 84: 85: /** 86: * Get the implementation for <i>algorithm</i> for service 87: * <i>service</i> from <i>provider</i>. The service is e.g. 88: * "Signature", and the algorithm "DSA". 89: * 90: * @param service The service name. 91: * @param algorithm The name of the algorithm to get. 92: * @param provider The provider to get the implementation from. 93: * @return The engine class for the specified algorithm; the object 94: * returned is typically a subclass of the SPI class for that 95: * service, but callers should check that this is so. 96: * @throws NoSuchAlgorithmException If the implementation cannot be 97: * found or cannot be instantiated. 98: * @throws InvocationTargetException If the SPI class's constructor 99: * throws an exception. 100: * @throws IllegalArgumentException If any of the three arguments are null. 101: */ 102: public static Object getInstance(String service, String algorithm, 103: Provider provider) 104: throws InvocationTargetException, NoSuchAlgorithmException 105: { 106: return getInstance(service, algorithm, provider, NO_ARGS); 107: } 108: 109: /** 110: * Get the implementation for <i>algorithm</i> for service 111: * <i>service</i> from <i>provider</i>, passing <i>initArgs</i> to the 112: * SPI class's constructor (which cannot be null; pass a zero-length 113: * array if the SPI takes no arguments). The service is e.g. 114: * "Signature", and the algorithm "DSA". 115: * 116: * @param service The service name. 117: * @param algorithm The name of the algorithm to get. 118: * @param provider The provider to get the implementation from. 119: * @param initArgs The arguments to pass to the SPI class's 120: * constructor (cannot be null). 121: * @return The engine class for the specified algorithm; the object 122: * returned is typically a subclass of the SPI class for that 123: * service, but callers should check that this is so. 124: * @throws NoSuchAlgorithmException If the implementation cannot be 125: * found or cannot be instantiated. 126: * @throws InvocationTargetException If the SPI class's constructor 127: * throws an exception. 128: * @throws IllegalArgumentException If any of the four arguments are null. 129: */ 130: public static Object getInstance(String service, String algorithm, 131: Provider provider, Object[] initArgs) 132: throws InvocationTargetException, NoSuchAlgorithmException 133: { 134: if (service != null) 135: service = service.trim(); 136: 137: if (algorithm != null) 138: algorithm = algorithm.trim(); 139: 140: if (service == null || service.length() == 0 141: || algorithm == null || algorithm.length() == 0 142: || provider == null || initArgs == null) 143: throw new IllegalArgumentException(); 144: 145: 146: Enumeration enumer = provider.propertyNames(); 147: String key; 148: String alias; 149: int count = 0; 150: boolean algorithmFound = false; 151: 152: while (enumer.hasMoreElements()) 153: { 154: key = (String) enumer.nextElement(); 155: 156: if (key.equalsIgnoreCase(service + "." + algorithm)) 157: { 158: // remove the service portion from the key 159: algorithm = key.substring(service.length() + 1); 160: 161: algorithmFound = true; 162: break; 163: 164: } 165: else if (key.equalsIgnoreCase(ALG_ALIAS + service + "." + algorithm)) 166: { 167: 168: alias = (String) provider.getProperty(key); 169: 170: if (! algorithm.equalsIgnoreCase(alias)) // does not refer to itself 171: { 172: algorithm = alias; 173: if (count++ > MAX_ALIASES) 174: throw new NoSuchAlgorithmException("too many aliases"); 175: 176: // need to reset enumeration to now look for the alias 177: enumer = provider.propertyNames(); 178: } 179: } 180: } 181: 182: if (! algorithmFound) 183: { 184: throw new NoSuchAlgorithmException(algorithm); 185: } 186: 187: 188: // Find and instantiate the implementation. 189: Class clazz = null; 190: ClassLoader loader = provider.getClass().getClassLoader(); 191: Constructor constructor = null; 192: String error = algorithm; 193: 194: try 195: { 196: if (loader != null) 197: clazz = loader.loadClass(provider.getProperty(service+"."+algorithm)); 198: else 199: clazz = Class.forName(provider.getProperty(service+"."+algorithm)); 200: constructor = getCompatibleConstructor(clazz, initArgs); 201: return constructor.newInstance(initArgs); 202: } 203: catch (ClassNotFoundException cnfe) 204: { 205: error = "class not found: " + algorithm; 206: } 207: catch (IllegalAccessException iae) 208: { 209: error = "illegal access: " + iae.getMessage(); 210: } 211: catch (InstantiationException ie) 212: { 213: error = "instantiation exception: " + ie.getMessage(); 214: } 215: catch (ExceptionInInitializerError eiie) 216: { 217: error = "exception in initializer: " + eiie.getMessage(); 218: } 219: catch (SecurityException se) 220: { 221: error = "security exception: " + se.getMessage(); 222: } 223: catch (NoSuchMethodException nsme) 224: { 225: error = "no appropriate constructor found"; 226: } 227: 228: throw new NoSuchAlgorithmException(error); 229: } 230: 231: // Own methods. 232: // ------------------------------------------------------------------------ 233: 234: /** 235: * Find a constructor in the given class that can take the specified 236: * argument list, allowing any of which to be null. 237: * 238: * @param clazz The class from which to get the constructor. 239: * @param initArgs The argument list to be passed to the constructor. 240: * @return The constructor. 241: * @throws NoSuchMethodException If no constructor of the given class 242: * can take the specified argument array. 243: */ 244: private static Constructor getCompatibleConstructor(Class clazz, 245: Object[] initArgs) 246: throws NoSuchMethodException 247: { 248: Constructor[] c = clazz.getConstructors(); 249: outer:for (int i = 0; i < c.length; i++) 250: { 251: Class[] argTypes = c[i].getParameterTypes(); 252: if (argTypes.length != initArgs.length) 253: continue; 254: for (int j = 0; j < argTypes.length; j++) 255: { 256: if (initArgs[j] != null && 257: !argTypes[j].isAssignableFrom(initArgs[j].getClass())) 258: continue outer; 259: } 260: // If we reach this point, we know this constructor (c[i]) has 261: // the same number of parameters as the target parameter list, 262: // and all our parameters are either (1) null, or (2) assignable 263: // to the target parameter type. 264: return c[i]; 265: } 266: throw new NoSuchMethodException(); 267: } 268: }