Source for java.security.Security

   1: /* Security.java --- Java base security class implementation
   2:    Copyright (C) 1999, 2001, 2002, 2003, 2004, 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: 
  40: package java.security;
  41: 
  42: import gnu.classpath.SystemProperties;
  43: 
  44: import gnu.classpath.Configuration;
  45: import gnu.classpath.VMStackWalker;
  46: 
  47: import java.io.IOException;
  48: import java.io.InputStream;
  49: import java.net.URL;
  50: import java.util.Collections;
  51: import java.util.Enumeration;
  52: import java.util.HashMap;
  53: import java.util.HashSet;
  54: import java.util.Iterator;
  55: import java.util.LinkedHashSet;
  56: import java.util.Map;
  57: import java.util.Properties;
  58: import java.util.Set;
  59: import java.util.Vector;
  60: 
  61: /**
  62:  * This class centralizes all security properties and common security methods.
  63:  * One of its primary uses is to manage security providers.
  64:  *
  65:  * @author Mark Benvenuto (ivymccough@worldnet.att.net)
  66:  */
  67: public final class Security
  68: {
  69:   private static final String ALG_ALIAS = "Alg.Alias.";
  70: 
  71:   private static Vector providers = new Vector();
  72:   private static Properties secprops = new Properties();
  73:   
  74:   static
  75:     {
  76:       String base = SystemProperties.getProperty("gnu.classpath.home.url");
  77:       String vendor = SystemProperties.getProperty("gnu.classpath.vm.shortname");
  78: 
  79:       // Try VM specific security file
  80:       boolean loaded = loadProviders (base, vendor);
  81:     
  82:       // Append classpath standard provider if possible
  83:       if (!loadProviders (base, "classpath")
  84:       && !loaded
  85:       && providers.size() == 0)
  86:       {
  87:           if (Configuration.DEBUG)
  88:           {
  89:               /* No providers found and both security files failed to
  90:                * load properly. Give a warning in case of DEBUG is
  91:                * enabled. Could be done with java.util.logging later.
  92:                */
  93:               System.err.println
  94:               ("WARNING: could not properly read security provider files:");
  95:               System.err.println
  96:               ("         " + base + "/security/" + vendor
  97:                + ".security");
  98:               System.err.println
  99:               ("         " + base + "/security/" + "classpath"
 100:                + ".security");
 101:               System.err.println
 102:               ("         Falling back to standard GNU security provider");
 103:           }
 104:               // Note that this matches our classpath.security file.
 105:           providers.addElement (new gnu.java.security.provider.Gnu());
 106:           providers.addElement(new gnu.javax.crypto.jce.GnuCrypto());
 107:               providers.addElement(new gnu.javax.crypto.jce.GnuSasl());
 108:               providers.addElement(new gnu.javax.net.ssl.provider.Jessie());
 109:               providers.addElement(new gnu.javax.security.auth.callback.GnuCallbacks());
 110:       }
 111:     }
 112:   // This class can't be instantiated.
 113:   private Security()
 114:   {
 115:   }
 116: 
 117:   /**
 118:    * Tries to load the vender specific security providers from the given base
 119:    * URL. Returns true if the resource could be read and completely parsed
 120:    * successfully, false otherwise.
 121:    */
 122:   private static boolean loadProviders(String baseUrl, String vendor)
 123:   {
 124:     if (baseUrl == null || vendor == null)
 125:       return false;
 126: 
 127:     boolean result = true;
 128:     String secfilestr = baseUrl + "/security/" + vendor + ".security";
 129:     try
 130:       {
 131:     InputStream fin = new URL(secfilestr).openStream();
 132:     secprops.load(fin);
 133: 
 134:     int i = 1;
 135:     String name;
 136:     while ((name = secprops.getProperty("security.provider." + i)) != null)
 137:       {
 138:         Exception exception = null;
 139:         try
 140:           {
 141:         ClassLoader sys = ClassLoader.getSystemClassLoader();
 142:         providers.addElement(Class.forName(name, true, sys).newInstance());
 143:           }
 144:         catch (ClassNotFoundException x)
 145:           {
 146:             exception = x;
 147:           }
 148:         catch (InstantiationException x)
 149:           {
 150:             exception = x;
 151:           }
 152:         catch (IllegalAccessException x)
 153:           {
 154:             exception = x;
 155:           }
 156: 
 157:         if (exception != null)
 158:           {
 159:         System.err.println ("WARNING: Error loading security provider "
 160:                     + name + ": " + exception);
 161:         result = false;
 162:           }
 163:         i++;
 164:       }
 165:       }
 166:     catch (IOException ignored)
 167:       {
 168:     result = false;
 169:       }
 170: 
 171:     return result;
 172:   }
 173: 
 174:   /**
 175:    * Returns the value associated to a designated property name for a given
 176:    * algorithm.
 177:    * 
 178:    * @param algName
 179:    *          the algorithm name.
 180:    * @param propName
 181:    *          the name of the property to return.
 182:    * @return the value of the specified property or <code>null</code> if none
 183:    *         found.
 184:    * @deprecated Use the provider-based and algorithm-independent
 185:    *             {@link AlgorithmParameters} and {@link KeyFactory} engine
 186:    *             classes instead.
 187:    */
 188:   public static String getAlgorithmProperty(String algName, String propName)
 189:   {
 190:     if (algName == null || propName == null)
 191:       return null;
 192: 
 193:     String property = String.valueOf(propName) + "." + String.valueOf(algName);
 194:     Provider p;
 195:     for (Iterator i = providers.iterator(); i.hasNext(); )
 196:       {
 197:         p = (Provider) i.next();
 198:         for (Iterator j = p.keySet().iterator(); j.hasNext(); )
 199:           {
 200:             String key = (String) j.next();
 201:             if (key.equalsIgnoreCase(property))
 202:               return p.getProperty(key);
 203:           }
 204:       }
 205:     return null;
 206:   }
 207: 
 208:   /**
 209:    * Inserts a new designated {@link Provider} at a designated (1-based)
 210:    * position in the current list of installed {@link Provider}s,
 211:    * 
 212:    * @param provider
 213:    *          the new {@link Provider} to add.
 214:    * @param position
 215:    *          the position (starting from 1) of where to install
 216:    *          <code>provider</code>.
 217:    * @return the actual position, in the list of installed Providers. Returns
 218:    *         <code>-1</code> if <code>provider</code> was laready in the
 219:    *         list. The actual position may be different than the desired
 220:    *         <code>position</code>.
 221:    * @throws SecurityException
 222:    *           if a {@link SecurityManager} is installed and it disallows this
 223:    *           operation.
 224:    * @see #getProvider(String)
 225:    * @see #removeProvider(String)
 226:    * @see SecurityPermission
 227:    */
 228:   public static int insertProviderAt(Provider provider, int position)
 229:   {
 230:     SecurityManager sm = System.getSecurityManager();
 231:     if (sm != null)
 232:       sm.checkSecurityAccess("insertProvider." + provider.getName());
 233: 
 234:     position--;
 235:     int max = providers.size ();
 236:     for (int i = 0; i < max; i++)
 237:       {
 238:     if (((Provider) providers.elementAt(i)).getName().equals(provider.getName()))
 239:       return -1;
 240:       }
 241: 
 242:     if (position < 0)
 243:       position = 0;
 244:     if (position > max)
 245:       position = max;
 246: 
 247:     providers.insertElementAt(provider, position);
 248: 
 249:     return position + 1;
 250:   }
 251: 
 252:   /**
 253:    * Appends the designated new {@link Provider} to the current list of
 254:    * installed {@link Provider}s.
 255:    * 
 256:    * @param provider
 257:    *          the new {@link Provider} to append.
 258:    * @return the position (starting from 1) of <code>provider</code> in the
 259:    *         current list of {@link Provider}s, or <code>-1</code> if
 260:    *         <code>provider</code> was already there.
 261:    * @throws SecurityException
 262:    *           if a {@link SecurityManager} is installed and it disallows this
 263:    *           operation.
 264:    * @see #getProvider(String)
 265:    * @see #removeProvider(String)
 266:    * @see SecurityPermission
 267:    */
 268:   public static int addProvider(Provider provider)
 269:   {
 270:     return insertProviderAt (provider, providers.size () + 1);
 271:   }
 272: 
 273:   /**
 274:    * Removes an already installed {@link Provider}, given its name, from the
 275:    * current list of installed {@link Provider}s.
 276:    * 
 277:    * @param name
 278:    *          the name of an already installed {@link Provider} to remove.
 279:    * @throws SecurityException
 280:    *           if a {@link SecurityManager} is installed and it disallows this
 281:    *           operation.
 282:    * @see #getProvider(String)
 283:    * @see #addProvider(Provider)
 284:    */
 285:   public static void removeProvider(String name)
 286:   {
 287:     SecurityManager sm = System.getSecurityManager();
 288:     if (sm != null)
 289:       sm.checkSecurityAccess("removeProvider." + name);
 290: 
 291:     int max = providers.size ();
 292:     for (int i = 0; i < max; i++)
 293:       {
 294:     if (((Provider) providers.elementAt(i)).getName().equals(name))
 295:       {
 296:         providers.remove(i);
 297:         break;
 298:       }
 299:       }
 300:   }
 301: 
 302:   /**
 303:    * Returns the current list of installed {@link Provider}s as an array
 304:    * ordered according to their installation preference order.
 305:    * 
 306:    * @return an array of all the installed providers.
 307:    */
 308:   public static Provider[] getProviders()
 309:   {
 310:     Provider[] array = new Provider[providers.size ()];
 311:     providers.copyInto (array);
 312:     return array;
 313:   }
 314: 
 315:   /**
 316:    * Returns an already installed {@link Provider} given its name.
 317:    * 
 318:    * @param name
 319:    *          the name of an already installed {@link Provider}.
 320:    * @return the {@link Provider} known by <code>name</code>. Returns
 321:    *         <code>null</code> if the current list of {@link Provider}s does
 322:    *         not include one named <code>name</code>.
 323:    * @see #removeProvider(String)
 324:    * @see #addProvider(Provider)
 325:    */
 326:   public static Provider getProvider(String name)
 327:   {
 328:     if (name == null)
 329:       return null;
 330:     else
 331:       {
 332:         name = name.trim();
 333:         if (name.length() == 0)
 334:           return null;
 335:       }
 336:     Provider p;
 337:     int max = providers.size ();
 338:     for (int i = 0; i < max; i++)
 339:       {
 340:     p = (Provider) providers.elementAt(i);
 341:     if (p.getName().equals(name))
 342:       return p;
 343:       }
 344:     return null;
 345:   }
 346: 
 347:   /**
 348:    * Returns the value associated with a Security propery.
 349:    * 
 350:    * @param key
 351:    *          the key of the property to fetch.
 352:    * @return the value of the Security property associated with
 353:    *         <code>key</code>. Returns <code>null</code> if no such property
 354:    *         was found.
 355:    * @throws SecurityException
 356:    *           if a {@link SecurityManager} is installed and it disallows this
 357:    *           operation.
 358:    * @see #setProperty(String, String)
 359:    * @see SecurityPermission
 360:    */
 361:   public static String getProperty(String key)
 362:   {
 363:     // XXX To prevent infinite recursion when the SecurityManager calls us,
 364:     // don't do a security check if the caller is trusted (by virtue of having
 365:     // been loaded by the bootstrap class loader).
 366:     SecurityManager sm = System.getSecurityManager();
 367:     if (sm != null && VMStackWalker.getCallingClassLoader() != null)
 368:       sm.checkSecurityAccess("getProperty." + key);
 369: 
 370:     return secprops.getProperty(key);
 371:   }
 372: 
 373:   /**
 374:    * Sets or changes a designated Security property to a designated value.
 375:    * 
 376:    * @param key
 377:    *          the name of the property to set.
 378:    * @param datum
 379:    *          the new value of the property.
 380:    * @throws SecurityException
 381:    *           if a {@link SecurityManager} is installed and it disallows this
 382:    *           operation.
 383:    * @see #getProperty(String)
 384:    * @see SecurityPermission
 385:    */
 386:   public static void setProperty(String key, String datum)
 387:   {
 388:     SecurityManager sm = System.getSecurityManager();
 389:     if (sm != null)
 390:       sm.checkSecurityAccess("setProperty." + key);
 391: 
 392:     if (datum == null)
 393:       secprops.remove(key);
 394:     else
 395:       secprops.put(key, datum);
 396:   }
 397: 
 398:   /**
 399:    * For a given <i>service</i> (e.g. Signature, MessageDigest, etc...) this
 400:    * method returns the {@link Set} of all available algorithm names (instances
 401:    * of {@link String}, from all currently installed {@link Provider}s.
 402:    * 
 403:    * @param serviceName
 404:    *          the case-insensitive name of a service (e.g. Signature,
 405:    *          MessageDigest, etc).
 406:    * @return a {@link Set} of {@link String}s containing the names of all
 407:    *         algorithm names provided by all of the currently installed
 408:    *         {@link Provider}s.
 409:    * @since 1.4
 410:    */
 411:   public static Set<String> getAlgorithms(String serviceName)
 412:   {
 413:     HashSet<String> result = new HashSet<String>();
 414:     if (serviceName == null || serviceName.length() == 0)
 415:       return result;
 416: 
 417:     serviceName = serviceName.trim();
 418:     if (serviceName.length() == 0)
 419:       return result;
 420: 
 421:     serviceName = serviceName.toUpperCase()+".";
 422:     Provider[] providers = getProviders();
 423:     int ndx;
 424:     for (int i = 0; i < providers.length; i++)
 425:       for (Enumeration e = providers[i].propertyNames(); e.hasMoreElements(); )
 426:         {
 427:           String service = ((String) e.nextElement()).trim();
 428:           if (service.toUpperCase().startsWith(serviceName))
 429:             {
 430:               service = service.substring(serviceName.length()).trim();
 431:               ndx = service.indexOf(' '); // get rid of attributes
 432:               if (ndx != -1)
 433:                 service = service.substring(0, ndx);
 434:               result.add(service);
 435:             }
 436:         }
 437:     return Collections.unmodifiableSet(result);
 438:   }
 439: 
 440:   /**
 441:    * Returns an array of currently installed {@link Provider}s, ordered
 442:    * according to their installation preference order, which satisfy a given
 443:    * <i>selection</i> criterion.
 444:    * 
 445:    * <p>This implementation recognizes a <i>selection</i> criterion written in
 446:    * one of two following forms:</p>
 447:    * 
 448:    * <ul>
 449:    *   <li>&lt;crypto_service&gt;.&lt;algorithm_or_type&gt;: Where
 450:    *   <i>crypto_service</i> is a case-insensitive string, similar to what has
 451:    *   been described in the {@link #getAlgorithms(String)} method, and
 452:    *   <i>algorithm_or_type</i> is a known case-insensitive name of an
 453:    *   Algorithm, or one of its aliases.
 454:    *   
 455:    *   <p>For example, "CertificateFactory.X.509" would return all the installed
 456:    *   {@link Provider}s which provide a <i>CertificateFactory</i>
 457:    *   implementation of <i>X.509</i>.</p></li>
 458:    *   
 459:    *   <li>&lt;crypto_service&gt;.&lt;algorithm_or_type&gt; &lt;attribute_name&gt;:&lt;value&gt;:
 460:    *   Where <i>crypto_service</i> is a case-insensitive string, similar to what
 461:    *   has been described in the {@link #getAlgorithms(String)} method,
 462:    *   <i>algorithm_or_type</i> is a case-insensitive known name of an Algorithm
 463:    *   or one of its aliases, <i>attribute_name</i> is a case-insensitive
 464:    *   property name with no whitespace characters, and no dots, in-between, and
 465:    *   <i>value</i> is a {@link String} with no whitespace characters in-between.
 466:    *   
 467:    *   <p>For example, "Signature.Sha1WithDSS KeySize:1024" would return all the
 468:    *   installed {@link Provider}s which declared their ability to provide
 469:    *   <i>Signature</i> services, using the <i>Sha1WithDSS</i> algorithm with
 470:    *   key sizes of <i>1024</i>.</p></li>
 471:    * </ul>
 472:    * 
 473:    * @param filter
 474:    *          the <i>selection</i> criterion for selecting among the installed
 475:    *          {@link Provider}s.
 476:    * @return all the installed {@link Provider}s which satisfy the <i>selection</i>
 477:    *         criterion. Returns <code>null</code> if no installed
 478:    *         {@link Provider}s were found which satisfy the <i>selection</i>
 479:    *         criterion. Returns ALL installed {@link Provider}s if
 480:    *         <code>filter</code> is <code>null</code> or is an empty string.
 481:    * @throws InvalidParameterException
 482:    *           if an exception occurs while parsing the <code>filter</code>.
 483:    * @see #getProviders(Map)
 484:    */
 485:   public static Provider[] getProviders(String filter)
 486:   {
 487:     if (providers == null || providers.isEmpty())
 488:       return null;
 489: 
 490:     if (filter == null || filter.length() == 0)
 491:       return getProviders();
 492: 
 493:     HashMap map = new HashMap(1);
 494:     int i = filter.indexOf(':');
 495:     if (i == -1) // <service>.<algorithm>
 496:       map.put(filter, "");
 497:     else // <service>.<algorithm> <attribute>:<value>
 498:       map.put(filter.substring(0, i), filter.substring(i+1));
 499: 
 500:     return getProviders(map);
 501:   }
 502: 
 503:   /**
 504:    * Returns an array of currently installed {@link Provider}s which satisfy a
 505:    * set of <i>selection</i> criteria.
 506:    * 
 507:    * <p>The <i>selection</i> criteria are defined in a {@link Map} where each
 508:    * element specifies a <i>selection</i> querry. The <i>Keys</i> in this
 509:    * {@link Map} must be in one of the two following forms:</p>
 510:    * 
 511:    * <ul>
 512:    *   <li>&lt;crypto_service&gt;.&lt;algorithm_or_type&gt;: Where
 513:    *   <i>crypto_service</i> is a case-insensitive string, similar to what has
 514:    *   been described in the {@link #getAlgorithms(String)} method, and
 515:    *   <i>algorithm_or_type</i> is a case-insensitive known name of an
 516:    *   Algorithm, or one of its aliases. The <i>value</i> of the entry in the
 517:    *   {@link Map} for such a <i>Key</i> MUST be the empty string.
 518:    *   {@link Provider}s which provide an implementation for the designated
 519:    *   <i>service algorithm</i> are included in the result.</li>
 520:    *   
 521:    *   <li>&lt;crypto_service&gt;.&lt;algorithm_or_type&gt; &lt;attribute_name&gt;:
 522:    *   Where <i>crypto_service</i> is a case-insensitive string, similar to what
 523:    *   has been described in the {@link #getAlgorithms(String)} method,
 524:    *   <i>algorithm_or_type</i> is a case-insensitive known name of an Algorithm
 525:    *   or one of its aliases, and <i>attribute_name</i> is a case-insensitive
 526:    *   property name with no whitespace characters, and no dots, in-between. The
 527:    *   <i>value</i> of the entry in this {@link Map} for such a <i>Key</i> MUST
 528:    *   NOT be <code>null</code> or an empty string. {@link Provider}s which
 529:    *   declare the designated <i>attribute_name</i> and <i>value</i> for the
 530:    *   designated <i>service algorithm</i> are included in the result.</li>
 531:    * </ul>
 532:    * 
 533:    * @param filter
 534:    *          a {@link Map} of <i>selection querries</i>.
 535:    * @return all currently installed {@link Provider}s which satisfy ALL the
 536:    *         <i>selection</i> criteria defined in <code>filter</code>.
 537:    *         Returns ALL installed {@link Provider}s if <code>filter</code>
 538:    *         is <code>null</code> or empty.
 539:    * @throws InvalidParameterException
 540:    *           if an exception is encountered while parsing the syntax of the
 541:    *           {@link Map}'s <i>keys</i>.
 542:    * @see #getProviders(String)
 543:    */
 544:   public static Provider[] getProviders(Map<String,String> filter)
 545:   {
 546:     if (providers == null || providers.isEmpty())
 547:       return null;
 548: 
 549:     if (filter == null)
 550:       return getProviders();
 551: 
 552:     Set<String> querries = filter.keySet();
 553:     if (querries == null || querries.isEmpty())
 554:       return getProviders();
 555: 
 556:     LinkedHashSet result = new LinkedHashSet(providers); // assume all
 557:     int dot, ws;
 558:     String querry, service, algorithm, attribute, value;
 559:     LinkedHashSet serviceProviders = new LinkedHashSet(); // preserve insertion order
 560:     for (Iterator i = querries.iterator(); i.hasNext(); )
 561:       {
 562:         querry = (String) i.next();
 563:         if (querry == null) // all providers
 564:           continue;
 565: 
 566:         querry = querry.trim();
 567:         if (querry.length() == 0) // all providers
 568:           continue;
 569: 
 570:         dot = querry.indexOf('.');
 571:         if (dot == -1) // syntax error
 572:           throw new InvalidParameterException(
 573:               "missing dot in '" + String.valueOf(querry)+"'");
 574: 
 575:         value = filter.get(querry);
 576:         // deconstruct querry into [service, algorithm, attribute]
 577:         if (value == null || value.trim().length() == 0) // <service>.<algorithm>
 578:           {
 579:             value = null;
 580:             attribute = null;
 581:             service = querry.substring(0, dot).trim();
 582:             algorithm = querry.substring(dot+1).trim();
 583:           }
 584:         else // <service>.<algorithm> <attribute>
 585:           {
 586:             ws = querry.indexOf(' ');
 587:             if (ws == -1)
 588:               throw new InvalidParameterException(
 589:                   "value (" + String.valueOf(value) +
 590:                   ") is not empty, but querry (" + String.valueOf(querry) +
 591:                   ") is missing at least one space character");
 592:             value = value.trim();
 593:             attribute = querry.substring(ws+1).trim();
 594:             // was the dot in the attribute?
 595:             if (attribute.indexOf('.') != -1)
 596:               throw new InvalidParameterException(
 597:                   "attribute_name (" + String.valueOf(attribute) +
 598:                   ") in querry (" + String.valueOf(querry) + ") contains a dot");
 599: 
 600:             querry = querry.substring(0, ws).trim();
 601:             service = querry.substring(0, dot).trim();
 602:             algorithm = querry.substring(dot+1).trim();
 603:           }
 604: 
 605:         // service and algorithm must not be empty
 606:         if (service.length() == 0)
 607:           throw new InvalidParameterException(
 608:               "<crypto_service> in querry (" + String.valueOf(querry) +
 609:               ") is empty");
 610: 
 611:         if (algorithm.length() == 0)
 612:           throw new InvalidParameterException(
 613:               "<algorithm_or_type> in querry (" + String.valueOf(querry) +
 614:               ") is empty");
 615: 
 616:         selectProviders(service, algorithm, attribute, value, result, serviceProviders);
 617:         result.retainAll(serviceProviders); // eval next retaining found providers
 618:         if (result.isEmpty()) // no point continuing
 619:           break;
 620:       }
 621: 
 622:     if (result.isEmpty())
 623:       return null;
 624: 
 625:     return (Provider[]) result.toArray(new Provider[result.size()]);
 626:   }
 627: 
 628:   private static void selectProviders(String svc, String algo, String attr,
 629:                                       String val, LinkedHashSet providerSet,
 630:                                       LinkedHashSet result)
 631:   {
 632:     result.clear(); // ensure we start with an empty result set
 633:     for (Iterator i = providerSet.iterator(); i.hasNext(); )
 634:       {
 635:         Provider p = (Provider) i.next();
 636:         if (provides(p, svc, algo, attr, val))
 637:           result.add(p);
 638:       }
 639:   }
 640: 
 641:   private static boolean provides(Provider p, String svc, String algo,
 642:                                   String attr, String val)
 643:   {
 644:     Iterator it;
 645:     String serviceDotAlgorithm = null;
 646:     String key = null;
 647:     String realVal;
 648:     boolean found = false;
 649:     // if <svc>.<algo> <attr> is in the set then so is <svc>.<algo>
 650:     // but it may be stored under an alias <algo>. resolve
 651:     outer: for (int r = 0; r < 3; r++) // guard against circularity
 652:       {
 653:         serviceDotAlgorithm = (svc+"."+String.valueOf(algo)).trim();
 654:         for (it = p.keySet().iterator(); it.hasNext(); )
 655:           {
 656:             key = (String) it.next();
 657:             if (key.equalsIgnoreCase(serviceDotAlgorithm)) // eureka
 658:               {
 659:                 found = true;
 660:                 break outer;
 661:               }
 662:             // it may be there but as an alias
 663:             if (key.equalsIgnoreCase(ALG_ALIAS + serviceDotAlgorithm))
 664:               {
 665:                 algo = p.getProperty(key);
 666:                 continue outer;
 667:               }
 668:             // else continue inner
 669:           }
 670:       }
 671: 
 672:     if (!found)
 673:       return false;
 674: 
 675:     // found a candidate for the querry.  do we have an attr to match?
 676:     if (val == null) // <service>.<algorithm> querry
 677:       return true;
 678: 
 679:     // <service>.<algorithm> <attribute>; find the key entry that match
 680:     String realAttr;
 681:     int limit = serviceDotAlgorithm.length() + 1;
 682:     for (it = p.keySet().iterator(); it.hasNext(); )
 683:       {
 684:         key = (String) it.next();
 685:         if (key.length() <= limit)
 686:           continue;
 687: 
 688:         if (key.substring(0, limit).equalsIgnoreCase(serviceDotAlgorithm+" "))
 689:           {
 690:             realAttr = key.substring(limit).trim();
 691:             if (! realAttr.equalsIgnoreCase(attr))
 692:               continue;
 693: 
 694:             // eveything matches so far.  do the value
 695:             realVal = p.getProperty(key);
 696:             if (realVal == null)
 697:               return false;
 698: 
 699:             realVal = realVal.trim();
 700:             // is it a string value?
 701:             if (val.equalsIgnoreCase(realVal))
 702:               return true;
 703: 
 704:             // assume value is a number. cehck for greater-than-or-equal
 705:             return (new Integer(val).intValue() >= new Integer(realVal).intValue());
 706:           }
 707:       }
 708: 
 709:     return false;
 710:   }
 711: }