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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: /** 83: * Return the implementation for <i>algorithm</i> for service <i>service</i> 84: * from <i>provider</i>. The service is e.g. "Signature", and the algorithm 85: * "DSA". 86: * 87: * @param service The service name. 88: * @param algorithm The name of the algorithm to get. 89: * @param provider The provider to get the implementation from. 90: * @return The engine class for the specified algorithm; the object returned 91: * is typically a subclass of the SPI class for that service, but 92: * callers should check that this is so. 93: * @throws NoSuchAlgorithmException If the implementation cannot be found or 94: * cannot be instantiated. 95: * @throws InvocationTargetException If the SPI class's constructor throws an 96: * exception. 97: * @throws IllegalArgumentException If any of the three arguments is null. 98: */ 99: public static Object getInstance(String service, String algorithm, 100: Provider provider) 101: throws InvocationTargetException, NoSuchAlgorithmException 102: { 103: return getInstance(service, algorithm, provider, NO_ARGS); 104: } 105: 106: /** 107: * Return the implementation for <i>algorithm</i> for service <i>service</i> 108: * from <i>provider</i>, passing <i>initArgs</i> to the SPI class's 109: * constructor (which cannot be null; pass a zero-length array if the SPI 110: * takes no arguments). The service is e.g. "Signature", and the algorithm 111: * "DSA". 112: * 113: * @param service The service name. 114: * @param algorithm The name of the algorithm to get. 115: * @param provider The provider to get the implementation from. 116: * @param initArgs The arguments to pass to the SPI class's constructor 117: * (cannot be null). 118: * @return The engine class for the specified algorithm; the object returned 119: * is typically a subclass of the SPI class for that service, but 120: * callers should check that this is so. 121: * @throws NoSuchAlgorithmException If the implementation cannot be found or 122: * cannot be instantiated. 123: * @throws InvocationTargetException If the SPI class's constructor throws an 124: * exception. 125: * @throws IllegalArgumentException If any of the four arguments is 126: * <code>null</code> or if either <code>service</code>, or 127: * <code>algorithm</code> is an empty string. 128: */ 129: public static Object getInstance(String service, String algorithm, 130: Provider provider, Object[] initArgs) 131: throws InvocationTargetException, NoSuchAlgorithmException 132: { 133: if (service == null) 134: throw new IllegalArgumentException("service MUST NOT be null"); 135: service = service.trim(); 136: if (service.length() == 0) 137: throw new IllegalArgumentException("service MUST NOT be empty"); 138: if (algorithm == null) 139: throw new IllegalArgumentException("algorithm MUST NOT be null"); 140: algorithm = algorithm.trim(); 141: if (algorithm.length() == 0) 142: throw new IllegalArgumentException("algorithm MUST NOT be empty"); 143: if (provider == null) 144: throw new IllegalArgumentException("provider MUST NOT be null"); 145: if (initArgs == null) 146: throw new IllegalArgumentException("Constructor's parameters MUST NOT be null"); 147: 148: Enumeration enumer = provider.propertyNames(); 149: String key = null; 150: String alias; 151: int count = 0; 152: boolean algorithmFound = false; 153: StringBuilder sb = new StringBuilder(); 154: while (enumer.hasMoreElements()) 155: { 156: key = (String) enumer.nextElement(); 157: if (key.equalsIgnoreCase(service + "." + algorithm)) 158: { 159: // remove the service portion from the key 160: algorithm = key.substring(service.length() + 1); 161: algorithmFound = true; 162: break; 163: } 164: else if (key.equalsIgnoreCase(ALG_ALIAS + service + "." + algorithm)) 165: { 166: alias = (String) provider.getProperty(key); 167: if (! algorithm.equalsIgnoreCase(alias)) // does not refer to itself 168: { 169: algorithm = alias; 170: if (count++ > MAX_ALIASES) 171: { 172: sb.append("Algorithm [").append(algorithm) 173: .append("] of type [").append(service) 174: .append("] from provider [").append(provider) 175: .append("] has too many aliases"); 176: throw new NoSuchAlgorithmException(sb.toString()); 177: } 178: // need to reset enumeration to now look for the alias 179: enumer = provider.propertyNames(); 180: } 181: } 182: } 183: 184: if (! algorithmFound) 185: { 186: sb.append("Algorithm [").append(algorithm).append("] of type [") 187: .append(service).append("] from provider [") 188: .append(provider).append("] is not found"); 189: throw new NoSuchAlgorithmException(sb.toString()); 190: } 191: 192: // Find and instantiate the implementation 193: Class clazz = null; 194: ClassLoader loader = provider.getClass().getClassLoader(); 195: Constructor constructor = null; 196: String className = provider.getProperty(key); 197: sb.append("Class [").append(className).append("] for algorithm [") 198: .append(algorithm).append("] of type [").append(service) 199: .append("] from provider [").append(provider).append("] "); 200: Throwable cause = null; 201: try 202: { 203: if (loader != null) 204: clazz = loader.loadClass(className); 205: else 206: clazz = Class.forName(className); 207: constructor = getCompatibleConstructor(clazz, initArgs); 208: return constructor.newInstance(initArgs); 209: } 210: catch (ClassNotFoundException x) 211: { 212: sb.append("cannot not be found"); 213: cause = x; 214: } 215: catch (IllegalAccessException x) 216: { 217: sb.append("cannot be accessed"); 218: cause = x; 219: } 220: catch (InstantiationException x) 221: { 222: sb.append("cannot be instantiated"); 223: cause = x; 224: } 225: catch (ExceptionInInitializerError x) 226: { 227: sb.append("cannot be initialized"); 228: cause = x; 229: } 230: catch (SecurityException x) 231: { 232: sb.append("caused a security violation"); 233: cause = x; 234: } 235: catch (NoSuchMethodException x) 236: { 237: sb.append("does not have/expose an appropriate constructor"); 238: cause = x; 239: } 240: 241: NoSuchAlgorithmException x = new NoSuchAlgorithmException(sb.toString()); 242: x.initCause(cause); 243: throw x; 244: } 245: 246: /** 247: * Find a constructor in the given class that can take the specified 248: * argument list, allowing any of which to be null. 249: * 250: * @param clazz The class from which to get the constructor. 251: * @param initArgs The argument list to be passed to the constructor. 252: * @return The constructor. 253: * @throws NoSuchMethodException If no constructor of the given class 254: * can take the specified argument array. 255: */ 256: private static Constructor getCompatibleConstructor(Class clazz, 257: Object[] initArgs) 258: throws NoSuchMethodException 259: { 260: Constructor[] c = clazz.getConstructors(); 261: outer:for (int i = 0; i < c.length; i++) 262: { 263: Class[] argTypes = c[i].getParameterTypes(); 264: if (argTypes.length != initArgs.length) 265: continue; 266: for (int j = 0; j < argTypes.length; j++) 267: { 268: if (initArgs[j] != null && 269: !argTypes[j].isAssignableFrom(initArgs[j].getClass())) 270: continue outer; 271: } 272: // If we reach this point, we know this constructor (c[i]) has 273: // the same number of parameters as the target parameter list, 274: // and all our parameters are either (1) null, or (2) assignable 275: // to the target parameter type. 276: return c[i]; 277: } 278: throw new NoSuchMethodException(); 279: } 280: }