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1: /* Engine -- generic getInstance method. 2: Copyright (C) 2003 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: 46: /** 47: * Generic implementation of the getInstance methods in the various 48: * engine classes in java.security. 49: * <p> 50: * These classes ({@link java.security.Signature} for example) can be 51: * thought of as the "chrome, upholstery, and steering wheel", and the SPI 52: * (service provider interface, e.g. {@link java.security.SignatureSpi}) 53: * classes can be thought of as the "engine" -- providing the actual 54: * functionality of whatever cryptographic algorithm the instance 55: * represents. 56: * 57: * @see Provider 58: * @author Casey Marshall 59: */ 60: public final class Engine 61: { 62: 63: // Constants. 64: // ------------------------------------------------------------------------ 65: 66: /** Prefix for aliases. */ 67: private static final String ALG_ALIAS = "Alg.Alias."; 68: 69: /** Maximum number of aliases to try. */ 70: private static final int MAX_ALIASES = 5; 71: 72: /** Argument list for no-argument constructors. */ 73: private static final Object[] NO_ARGS = new Object[0]; 74: 75: // Constructor. 76: // ------------------------------------------------------------------------ 77: 78: /** This class cannot be instantiated. */ 79: private Engine() { } 80: 81: // Class method. 82: // ------------------------------------------------------------------------ 83: 84: /** 85: * Get the implementation for <i>algorithm</i> for service 86: * <i>service</i> from <i>provider</i>. The service is e.g. 87: * "Signature", and the algorithm "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 93: * returned is typically a subclass of the SPI class for that 94: * service, but callers should check that this is so. 95: * @throws NoSuchAlgorithmException If the implementation cannot be 96: * found or cannot be instantiated. 97: * @throws InvocationTargetException If the SPI class's constructor 98: * throws an exception. 99: * @throws IllegalArgumentException If any of the three arguments are 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: * Get the implementation for <i>algorithm</i> for service 110: * <i>service</i> from <i>provider</i>, passing <i>initArgs</i> to the 111: * SPI class's constructor (which cannot be null; pass a zero-length 112: * array if the SPI takes no arguments). The service is e.g. 113: * "Signature", and the algorithm "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 119: * constructor (cannot be null). 120: * @return The engine class for the specified algorithm; the object 121: * returned is typically a subclass of the SPI class for that 122: * service, but callers should check that this is so. 123: * @throws NoSuchAlgorithmException If the implementation cannot be 124: * found or cannot be instantiated. 125: * @throws InvocationTargetException If the SPI class's constructor 126: * throws an exception. 127: * @throws IllegalArgumentException If any of the four arguments are null. 128: */ 129: public static Object getInstance(String service, String algorithm, 130: Provider provider, Object[] initArgs) 131: throws InvocationTargetException, NoSuchAlgorithmException 132: { 133: if (service == null || algorithm == null 134: || provider == null || initArgs == null) 135: throw new IllegalArgumentException(); 136: 137: // If there is no property "service.algorithm" 138: if (provider.getProperty(service + "." + algorithm) == null) 139: { 140: // Iterate through aliases, until we find the class name or resolve 141: // too many aliases. 142: String alias = null; 143: int count = 0; 144: while ((alias = provider.getProperty( 145: ALG_ALIAS + service + "." + algorithm)) != null) 146: { 147: if (algorithm.equals(alias)) // Refers to itself! 148: break; 149: algorithm = alias; 150: if (count++ > MAX_ALIASES) 151: throw new NoSuchAlgorithmException("too many aliases"); 152: } 153: if (provider.getProperty(service + "." + algorithm) == null) 154: throw new NoSuchAlgorithmException(algorithm); 155: } 156: 157: // Find and instantiate the implementation. 158: Class clazz = null; 159: ClassLoader loader = provider.getClass().getClassLoader(); 160: Constructor constructor = null; 161: String error = algorithm; 162: 163: try 164: { 165: if (loader != null) 166: clazz = loader.loadClass(provider.getProperty(service+"."+algorithm)); 167: else 168: clazz = Class.forName(provider.getProperty(service+"."+algorithm)); 169: constructor = getCompatibleConstructor(clazz, initArgs); 170: return constructor.newInstance(initArgs); 171: } 172: catch (ClassNotFoundException cnfe) 173: { 174: error = "class not found: " + algorithm; 175: } 176: catch (IllegalAccessException iae) 177: { 178: error = "illegal access: " + iae.getMessage(); 179: } 180: catch (InstantiationException ie) 181: { 182: error = "instantiation exception: " + ie.getMessage(); 183: } 184: catch (ExceptionInInitializerError eiie) 185: { 186: error = "exception in initializer: " + eiie.getMessage(); 187: } 188: catch (SecurityException se) 189: { 190: error = "security exception: " + se.getMessage(); 191: } 192: catch (NoSuchMethodException nsme) 193: { 194: error = "no appropriate constructor found"; 195: } 196: 197: throw new NoSuchAlgorithmException(error); 198: } 199: 200: // Own methods. 201: // ------------------------------------------------------------------------ 202: 203: /** 204: * Find a constructor in the given class that can take the specified 205: * argument list, allowing any of which to be null. 206: * 207: * @param clazz The class from which to get the constructor. 208: * @param initArgs The argument list to be passed to the constructor. 209: * @return The constructor. 210: * @throws NoSuchMethodException If no constructor of the given class 211: * can take the specified argument array. 212: */ 213: private static Constructor getCompatibleConstructor(Class clazz, 214: Object[] initArgs) 215: throws NoSuchMethodException 216: { 217: Constructor[] c = clazz.getConstructors(); 218: outer:for (int i = 0; i < c.length; i++) 219: { 220: Class[] argTypes = c[i].getParameterTypes(); 221: if (argTypes.length != initArgs.length) 222: continue; 223: for (int j = 0; j < argTypes.length; j++) 224: { 225: if (initArgs[j] != null && 226: !argTypes[j].isAssignableFrom(initArgs[j].getClass())) 227: continue outer; 228: } 229: // If we reach this point, we know this constructor (c[i]) has 230: // the same number of parameters as the target parameter list, 231: // and all our parameters are either (1) null, or (2) assignable 232: // to the target parameter type. 233: return c[i]; 234: } 235: throw new NoSuchMethodException(); 236: } 237: }