Source for gnu.java.security.Engine

   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: }