Source for java.security.SecureRandom

   1: /* SecureRandom.java --- Secure Random class implementation
   2:    Copyright (C) 1999, 2001, 2002, 2003, 2005, 2006
   3:    Free Software Foundation, Inc.
   4: 
   5: This file is part of GNU Classpath.
   6: 
   7: GNU Classpath is free software; you can redistribute it and/or modify
   8: it under the terms of the GNU General Public License as published by
   9: the Free Software Foundation; either version 2, or (at your option)
  10: any later version.
  11: 
  12: GNU Classpath is distributed in the hope that it will be useful, but
  13: WITHOUT ANY WARRANTY; without even the implied warranty of
  14: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15: General Public License for more details.
  16: 
  17: You should have received a copy of the GNU General Public License
  18: along with GNU Classpath; see the file COPYING.  If not, write to the
  19: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  20: 02110-1301 USA.
  21: 
  22: Linking this library statically or dynamically with other modules is
  23: making a combined work based on this library.  Thus, the terms and
  24: conditions of the GNU General Public License cover the whole
  25: combination.
  26: 
  27: As a special exception, the copyright holders of this library give you
  28: permission to link this library with independent modules to produce an
  29: executable, regardless of the license terms of these independent
  30: modules, and to copy and distribute the resulting executable under
  31: terms of your choice, provided that you also meet, for each linked
  32: independent module, the terms and conditions of the license of that
  33: module.  An independent module is a module which is not derived from
  34: or based on this library.  If you modify this library, you may extend
  35: this exception to your version of the library, but you are not
  36: obligated to do so.  If you do not wish to do so, delete this
  37: exception statement from your version. */
  38: 
  39: package java.security;
  40: 
  41: import gnu.classpath.SystemProperties;
  42: import gnu.java.security.Engine;
  43: import gnu.java.security.action.GetSecurityPropertyAction;
  44: import gnu.java.security.jce.prng.Sha160RandomSpi;
  45: 
  46: import java.io.IOException;
  47: import java.io.InputStream;
  48: import java.lang.reflect.InvocationTargetException;
  49: import java.net.MalformedURLException;
  50: import java.net.URL;
  51: import java.util.Enumeration;
  52: import java.util.Random;
  53: import java.util.logging.Level;
  54: import java.util.logging.Logger;
  55: 
  56: /**
  57:  * An interface to a cryptographically secure pseudo-random number
  58:  * generator (PRNG). Random (or at least unguessable) numbers are used
  59:  * in all areas of security and cryptography, from the generation of
  60:  * keys and initialization vectors to the generation of random padding
  61:  * bytes.
  62:  *
  63:  * @author Mark Benvenuto (ivymccough@worldnet.att.net)
  64:  * @author Casey Marshall
  65:  */
  66: public class SecureRandom extends Random
  67: {
  68: 
  69:   // Constants and fields.
  70:   // ------------------------------------------------------------------------
  71: 
  72:   /** Service name for PRNGs. */
  73:   private static final String SECURE_RANDOM = "SecureRandom";
  74: 
  75:   private static final long serialVersionUID = 4940670005562187L;
  76: 
  77:   //Serialized Field
  78:   long counter = 0;        //Serialized
  79:   Provider provider = null;
  80:   byte[] randomBytes = null;    //Always null
  81:   int randomBytesUsed = 0;
  82:   SecureRandomSpi secureRandomSpi = null;
  83:   byte[] state = null;
  84:   private String algorithm;
  85: 
  86:   private boolean isSeeded = false;
  87: 
  88:   // Constructors.
  89:   // ------------------------------------------------------------------------
  90: 
  91:   /**
  92:      Default constructor for SecureRandom. It constructs a 
  93:      new SecureRandom by instantating the first SecureRandom 
  94:      algorithm in the default security provier. 
  95: 
  96:      It is not seeded and should be seeded using setSeed or else
  97:      on the first call to getnextBytes it will force a seed.
  98: 
  99:      It is maintained for backwards compatibility and programs
 100:      should use {@link #getInstance(java.lang.String)}.
 101:    */
 102:   public SecureRandom()
 103:   {
 104:     Provider[] p = Security.getProviders();
 105: 
 106:     //Format of Key: SecureRandom.algname
 107:     String key;
 108: 
 109:     String classname = null;
 110:     int i;
 111:     Enumeration e;
 112:     for (i = 0; i < p.length; i++)
 113:       {
 114:         e = p[i].propertyNames();
 115:         while (e.hasMoreElements())
 116:           {
 117:             key = (String) e.nextElement();
 118:             if (key.startsWith("SECURERANDOM."))
 119:               {
 120:                 if ((classname = p[i].getProperty(key)) != null)
 121:                   {
 122:                     try
 123:                       {
 124:                         secureRandomSpi = (SecureRandomSpi) Class.
 125:                           forName(classname).newInstance();
 126:                         provider = p[i];
 127:                         algorithm = key.substring(13); // Minus SecureRandom.
 128:                         return;
 129:                       }
 130:                     catch (ThreadDeath death)
 131:                       {
 132:                         throw death;
 133:                       }
 134:                     catch (Throwable t)
 135:               {
 136:             // Ignore.
 137:               }
 138:                   }
 139:               }
 140:           }
 141:       }
 142: 
 143:     // Nothing found. Fall back to SHA1PRNG
 144:     secureRandomSpi = new Sha160RandomSpi();
 145:     algorithm = "Sha160";
 146:   }
 147: 
 148:   /**
 149:      A constructor for SecureRandom. It constructs a new 
 150:      SecureRandom by instantating the first SecureRandom algorithm 
 151:      in the default security provier. 
 152: 
 153:      It is seeded with the passed function and is useful if the user
 154:      has access to hardware random device (like a radiation detector).
 155: 
 156:      It is maintained for backwards compatibility and programs
 157:      should use getInstance.
 158: 
 159:      @param seed Seed bytes for class
 160:    */
 161:   public SecureRandom(byte[] seed)
 162:   {
 163:     this();
 164:     setSeed(seed);
 165:   }
 166: 
 167:   /**
 168:      A constructor for SecureRandom. It constructs a new 
 169:      SecureRandom using the specified SecureRandomSpi from
 170:      the specified security provier. 
 171: 
 172:      @param secureRandomSpi A SecureRandomSpi class
 173:      @param provider A Provider class
 174:    */
 175:   protected SecureRandom(SecureRandomSpi secureRandomSpi, Provider provider)
 176:   {
 177:     this(secureRandomSpi, provider, "unknown");
 178:   }
 179: 
 180:   /**
 181:    * Private constructor called from the getInstance() method.
 182:    */
 183:   private SecureRandom(SecureRandomSpi secureRandomSpi, Provider provider,
 184:                String algorithm)
 185:   {
 186:     this.secureRandomSpi = secureRandomSpi;
 187:     this.provider = provider;
 188:     this.algorithm = algorithm;
 189:   }
 190: 
 191:   /**
 192:    * Returns an instance of a <code>SecureRandom</code> from the first provider
 193:    * that implements it.
 194:    * 
 195:    * @param algorithm The algorithm name.
 196:    * @return A new <code>SecureRandom</code> implementing the given algorithm.
 197:    * @throws NoSuchAlgorithmException If no installed provider implements the
 198:    *           given algorithm.
 199:    * @throws IllegalArgumentException if <code>algorithm</code> is
 200:    *           <code>null</code> or is an empty string.
 201:    */
 202:   public static SecureRandom getInstance(String algorithm)
 203:       throws NoSuchAlgorithmException
 204:   {
 205:     Provider[] p = Security.getProviders();
 206:     NoSuchAlgorithmException lastException = null;
 207:     for (int i = 0; i < p.length; i++)
 208:       try
 209:         {
 210:           return getInstance(algorithm, p[i]);
 211:         }
 212:       catch (NoSuchAlgorithmException x)
 213:         {
 214:           lastException = x;
 215:         }
 216:     if (lastException != null)
 217:       throw lastException;
 218:     throw new NoSuchAlgorithmException(algorithm);
 219:   }
 220: 
 221:   /**
 222:    * Returns an instance of a <code>SecureRandom</code> for the specified
 223:    * algorithm from the named provider.
 224:    * 
 225:    * @param algorithm The algorithm name.
 226:    * @param provider The provider name.
 227:    * @return A new <code>SecureRandom</code> implementing the chosen
 228:    *         algorithm.
 229:    * @throws NoSuchAlgorithmException If the named provider does not implement
 230:    *           the algorithm, or if the implementation cannot be instantiated.
 231:    * @throws NoSuchProviderException If no provider named <code>provider</code>
 232:    *           is currently installed.
 233:    * @throws IllegalArgumentException if either <code>algorithm</code> or
 234:    *           <code>provider</code> is <code>null</code> or empty.
 235:    */
 236:   public static SecureRandom getInstance(String algorithm, String provider)
 237:       throws NoSuchAlgorithmException, NoSuchProviderException
 238:   {
 239:     if (provider == null)
 240:       throw new IllegalArgumentException("provider MUST NOT be null");
 241:     provider = provider.trim();
 242:     if (provider.length() == 0)
 243:       throw new IllegalArgumentException("provider MUST NOT be empty");
 244:     Provider p = Security.getProvider(provider);
 245:     if (p == null)
 246:       throw new NoSuchProviderException(provider);
 247:     return getInstance(algorithm, p);
 248:   }
 249: 
 250:   /**
 251:    * Returns an instance of a <code>SecureRandom</code> for the specified
 252:    * algorithm from the given provider.
 253:    * 
 254:    * @param algorithm The <code>SecureRandom</code> algorithm to create.
 255:    * @param provider The provider to use.
 256:    * @throws NoSuchAlgorithmException If the algorithm cannot be found, or if
 257:    *           the class cannot be instantiated.
 258:    * @throws IllegalArgumentException if either <code>algorithm</code> or
 259:    *           <code>provider</code> is <code>null</code>, or if
 260:    *           <code>algorithm</code> is an empty string.
 261:    */
 262:   public static SecureRandom getInstance(String algorithm, Provider provider)
 263:       throws NoSuchAlgorithmException
 264:   {
 265:     StringBuilder sb = new StringBuilder("SecureRandom for algorithm [")
 266:         .append(algorithm).append("] from provider[")
 267:         .append(provider).append("] could not be created");
 268:     Throwable cause;
 269:     try
 270:       {
 271:         Object spi = Engine.getInstance(SECURE_RANDOM, algorithm, provider);
 272:         return new SecureRandom((SecureRandomSpi) spi, provider, algorithm);
 273:       }
 274:     catch (InvocationTargetException x)
 275:       {
 276:         cause = x.getCause();
 277:         if (cause instanceof NoSuchAlgorithmException)
 278:           throw (NoSuchAlgorithmException) cause;
 279:         if (cause == null)
 280:           cause = x;
 281:       }
 282:     catch (ClassCastException x)
 283:       {
 284:         cause = x;
 285:       }
 286:     NoSuchAlgorithmException x = new NoSuchAlgorithmException(sb.toString());
 287:     x.initCause(cause);
 288:     throw x;
 289:   }
 290: 
 291:   /**
 292:      Returns the provider being used by the current SecureRandom class.
 293: 
 294:      @return The provider from which this SecureRandom was attained
 295:    */
 296:   public final Provider getProvider()
 297:   {
 298:     return provider;
 299:   }
 300: 
 301:   /**
 302:    * Returns the algorithm name used or "unknown" when the algorithm
 303:    * used couldn't be determined (as when constructed by the protected
 304:    * 2 argument constructor).
 305:    *
 306:    * @since 1.5
 307:    */
 308:   public String getAlgorithm()
 309:   {
 310:     return algorithm;
 311:   }
 312: 
 313:   /**
 314:      Seeds the SecureRandom. The class is re-seeded for each call and 
 315:      each seed builds on the previous seed so as not to weaken security.
 316: 
 317:      @param seed seed bytes to seed with
 318:    */
 319:   public void setSeed(byte[] seed)
 320:   {
 321:     secureRandomSpi.engineSetSeed(seed);
 322:     isSeeded = true;
 323:   }
 324: 
 325:   /**
 326:      Seeds the SecureRandom. The class is re-seeded for each call and 
 327:      each seed builds on the previous seed so as not to weaken security.
 328: 
 329:      @param seed 8 seed bytes to seed with
 330:    */
 331:   public void setSeed(long seed)
 332:   {
 333:     // This particular setSeed will be called by Random.Random(), via
 334:     // our own constructor, before secureRandomSpi is initialized.  In
 335:     // this case we can't call a method on secureRandomSpi, and we
 336:     // definitely don't want to throw a NullPointerException.
 337:     // Therefore we test.
 338:     if (secureRandomSpi != null)
 339:       {
 340:         byte[] tmp = { (byte) (0xff & (seed >> 56)),
 341:                (byte) (0xff & (seed >> 48)),
 342:                (byte) (0xff & (seed >> 40)),
 343:                (byte) (0xff & (seed >> 32)),
 344:                (byte) (0xff & (seed >> 24)),
 345:                (byte) (0xff & (seed >> 16)),
 346:                (byte) (0xff & (seed >> 8)),
 347:                (byte) (0xff & seed)
 348:         };
 349:         secureRandomSpi.engineSetSeed(tmp);
 350:         isSeeded = true;
 351:       }
 352:   }
 353: 
 354:   /**
 355:      Generates a user specified number of bytes. This function
 356:      is the basis for all the random functions.
 357: 
 358:      @param bytes array to store generated bytes in
 359:    */
 360:   public void nextBytes(byte[] bytes)
 361:   {
 362:     if (!isSeeded)
 363:       setSeed(getSeed(32));
 364:     randomBytesUsed += bytes.length;
 365:     counter++;
 366:     secureRandomSpi.engineNextBytes(bytes);
 367:   }
 368: 
 369:   /**
 370:      Generates an integer containing the user specified
 371:      number of random bits. It is right justified and padded
 372:      with zeros.
 373: 
 374:      @param numBits number of random bits to get, 0 <= numBits <= 32;
 375: 
 376:      @return the random bits
 377:    */
 378:   protected final int next(int numBits)
 379:   {
 380:     if (numBits == 0)
 381:       return 0;
 382: 
 383:     byte[] tmp = new byte[(numBits + 7) / 8];
 384:     this.nextBytes(tmp);
 385:     int ret = 0;
 386:     for (int i = 0; i < tmp.length; i++)
 387:       ret |= (tmp[i] & 0xFF) << (8 * i);
 388: 
 389:     long mask = (1L << numBits) - 1;
 390:     return (int) (ret & mask);
 391:   }
 392: 
 393:   /**
 394:      Returns the given number of seed bytes. This method is
 395:      maintained only for backwards capability. 
 396: 
 397:      @param numBytes number of seed bytes to get
 398: 
 399:      @return an array containing the seed bytes
 400:    */
 401:   public static byte[] getSeed(int numBytes)
 402:   {
 403:     byte[] tmp = new byte[numBytes];
 404:     generateSeed(tmp);
 405:     return tmp;
 406:   }
 407: 
 408:   /**
 409:      Returns the specified number of seed bytes.
 410: 
 411:      @param numBytes number of seed bytes to get
 412: 
 413:      @return an array containing the seed bytes
 414:    */
 415:   public byte[] generateSeed(int numBytes)
 416:   {
 417:     return secureRandomSpi.engineGenerateSeed(numBytes);
 418:   }
 419: 
 420:   // Seed methods.
 421: 
 422:   private static final String SECURERANDOM_SOURCE = "securerandom.source";
 423:   private static final String JAVA_SECURITY_EGD = "java.security.egd";
 424:   private static final Logger logger = Logger.getLogger(SecureRandom.class.getName());
 425: 
 426:   private static int generateSeed(byte[] buffer)
 427:   {
 428:     return generateSeed(buffer, 0, buffer.length);
 429:   }
 430: 
 431:   private static int generateSeed(byte[] buffer, int offset, int length)
 432:   {
 433:     URL sourceUrl = null;
 434:     String urlStr = null;
 435: 
 436:     GetSecurityPropertyAction action = new GetSecurityPropertyAction(SECURERANDOM_SOURCE);
 437:     try
 438:       {
 439:         urlStr = (String) AccessController.doPrivileged(action);
 440:         if (urlStr != null)
 441:           sourceUrl = new URL(urlStr);
 442:       }
 443:     catch (MalformedURLException ignored)
 444:       {
 445:         logger.log(Level.WARNING, SECURERANDOM_SOURCE + " property is malformed: {0}", 
 446:                    urlStr);
 447:       }
 448: 
 449:     if (sourceUrl == null)
 450:       {
 451:         try
 452:           {
 453:             urlStr = SystemProperties.getProperty(JAVA_SECURITY_EGD);
 454:             if (urlStr != null)
 455:               sourceUrl = new URL(urlStr);
 456:           }
 457:         catch (MalformedURLException mue)
 458:           {
 459:             logger.log(Level.WARNING, JAVA_SECURITY_EGD + " property is malformed: {0}",
 460:                        urlStr);
 461:           }
 462:       }
 463: 
 464:     if (sourceUrl != null)
 465:       {
 466:         try
 467:           {
 468:             InputStream in = sourceUrl.openStream();
 469:             return in.read(buffer, offset, length);
 470:           }
 471:         catch (IOException ioe)
 472:           {
 473:             logger.log(Level.FINE, "error reading random bytes", ioe);
 474:           }
 475:       }
 476: 
 477:     // If we get here, we did not get any seed from a property URL.
 478:     return VMSecureRandom.generateSeed(buffer, offset, length);
 479:   }
 480: }