OSGiSelectionPolicy


1   /*
2    * Oscar - An implementation of the OSGi framework.
3    * Copyright (c) 2004, Richard S. Hall
4    * All rights reserved.
5    *  
6    * Redistribution and use in source and binary forms, with or without
7    * modification, are permitted provided that the following conditions
8    * are met:
9    *  
10   *   * Redistributions of source code must retain the above copyright
11   *     notice, this list of conditions and the following disclaimer.
12   *   * Redistributions in binary form must reproduce the above copyright
13   *     notice, this list of conditions and the following disclaimer in
14   *     the documentation and/or other materials provided with the
15   *     distribution.
16   *   * Neither the name of the ungoverned.org nor the names of its
17   *     contributors may be used to endorse or promote products derived
18   *     from this software without specific prior written permission.
19   *  
20   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
23   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
24   * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
25   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
26   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
30   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31   * 
32   * Contact: Richard S. Hall (heavy@ungoverned.org)
33   * Contributor(s):
34   * 
35  **/
36  package org.ungoverned.oscar;
37  
38  import java.net.MalformedURLException  ;
39  import java.net.URL  ;
40  import java.security.*;
41  import java.security.cert.Certificate  ;
42  import java.util.HashMap  ;
43  import java.util.Iterator  ;
44  import java.util.Map  ;
45  
46  import org.osgi.framework.Bundle;
47  import org.osgi.framework.PackagePermission;
48  import org.ungoverned.moduleloader.Module;
49  import org.ungoverned.moduleloader.ModuleEvent;
50  import org.ungoverned.moduleloader.ModuleListener;
51  import org.ungoverned.moduleloader.search.ImportSearchPolicy;
52  import org.ungoverned.moduleloader.search.SelectionPolicy;
53  import org.ungoverned.moduleloader.search.CompatibilityPolicy;
54  
55  public class OSGiSelectionPolicy implements SelectionPolicy, ModuleListener
56  {
57      private Oscar m_oscar = null;
58      private Map   m_resolvedPackageMap = new HashMap  ();
59      private Map   m_resolvedModuleMap = new HashMap  ();
60  
61      public OSGiSelectionPolicy(Oscar oscar)
62      {
63          m_oscar = oscar;
64      }
65  
66      /**
67       * Selects a single module to resolve the specified import
68       * from the array of compatible candidate modules. If the import
69       * target has not been resolved before, then this selection policy
70       * chooses the module that exports the newest version of the
71       * import target. If the import target has been resolved already,
72       * then the same module that was chosen before is chosen again.
73       * This ensures that all modules use the same version of all
74       * exported classes, as described in the OSGi specification.
75       * @param module the module that is importing the target.
76       * @param identifier the identifier of the import target.
77       * @param version the version number of the import target.
78       * @param candidates array of compatible candidate modules from which to choose.
79       * @param compatPolicy the compatibility policy that is being used.
80       * @return the selected module or <tt>null</tt> if no module
81       *         can be selected.
82      **/
83      public synchronized Module select(Module module, Object   identifier,
84          Object   v, Module[] candidates, CompatibilityPolicy compatPolicy)
85      {
86          String   pkgName = (String  ) identifier;
87          int[] version = (int[]) v;
88  
89          // See if a module was already selected to resolve this package.
90          Module selModule = (Module) m_resolvedPackageMap.get(pkgName);
91  
92          // If no module was previously selected to resolve the package,
93          // then try to choose one now.
94          if (selModule == null)
95          {
96              int[] selVersion = version;
97              Bundle selBundle = null;
98  
99              // Examine all exported instances of the package and
100             // choose the one with the newest version number. If
101             // there is more than one source for the newest version,
102             // then select the package coming from the bundle with
103             // the with the smallest bundle ID.
104             for (int i = 0; i < candidates.length; i++)
105             {
106                 // Get the bundle associated with the module.
107                 long id = BundleInfo.getBundleIdFromModuleId(candidates[i].getId());
108                 if (id < 0)
109                 {
110                     // Ignore modules for which there is no bundle.
111                     continue;
112                 }
113 
114                 BundleImpl bundle = (BundleImpl) m_oscar.getBundle(id);
115 
116                 // The bundle may be uninstalled, so just ignore that case.
117                 if (bundle == null)
118                 {
119                     continue;
120                 }
121 
122                 // Ignore the package if its bundle is not resolved,
123                 // active, or installed.
124                 if ((bundle.getState() != Bundle.RESOLVED)
125                     && (bundle.getState() != Bundle.ACTIVE)
126                     && (bundle.getState() != Bundle.INSTALLED))
127                 {
128                     continue;
129                 }
130 
131                 // If the security manager is set, then check if the
132                 // exporting bundle is allowed to export the package,
133                 // unless the bundle is the system bundle.
134                 if ((System.getSecurityManager() != null) && (bundle.getBundleId() != 0))
135                 {
136                     URL   url = null;
137                     try
138                     {
139                         url = new URL  (bundle.getInfo().getLocation());
140                     }
141                     catch (MalformedURLException   ex)
142                     {
143                         // For safety, ignore if we can't get its
144                         // location URL.
145                         continue;
146                     }
147                     try
148                     {
149                         AccessController.doPrivileged(
150                             new CheckExportPrivileged(url, pkgName));
151                     }
152                     catch (PrivilegedActionException ex)
153                     {
154                         // If we are here, then most likely the security
155                         // check failed, so ignore this package.
156                         continue;
157                     }
158                 }
159 
160                 int[] tmpVersion = (int[])
161                     ImportSearchPolicy.getExportVersion(candidates[i], pkgName);
162 
163                 // If this is the first match, then just select it.
164                 if ((selModule == null) &&
165                     (compatPolicy.compare(pkgName, tmpVersion, pkgName, selVersion) >= 0))
166                 {
167                     selModule = candidates[i];
168                     selVersion = tmpVersion;
169                     selBundle = bundle;
170                 }
171                 // If the current export package version is greater
172                 // than the selected export package version, then
173                 // record it instead.
174                 else if (compatPolicy.compare(pkgName, tmpVersion, pkgName, selVersion) > 0)
175                 {
176                     selModule = candidates[i];
177                     selVersion = tmpVersion;
178                     selBundle = bundle;
179                 }
180                 // If the current export package version is equal to
181                 // the selected export package version, but has a lower
182                 // bundle ID, then record it instead.
183                 else if ((compatPolicy.compare(pkgName, tmpVersion, pkgName, selVersion) == 0)
184                     && (bundle.getBundleId() < selBundle.getBundleId()))
185                 {
186                     selModule = candidates[i];
187                     selVersion = tmpVersion;
188                     selBundle = bundle;
189                 }
190             }
191 
192             m_resolvedPackageMap.put(pkgName, selModule);
193             m_resolvedModuleMap.put(selModule, selModule);
194         }
195         // See if the previously selected export module satisfies
196         // the current request, otherwise return null.
197         else
198         {
199             int[] selVersion = (int[])
200                 ImportSearchPolicy.getExportVersion(selModule, pkgName);
201             Module tmpModule = selModule;
202             selModule = null;
203             if (compatPolicy.isCompatible(pkgName, selVersion, pkgName, version))
204             {
205                 selModule = tmpModule;
206             }
207         }
208 
209         return selModule;
210     }
211 
212     public void moduleAdded(ModuleEvent event)
213     {
214     }
215 
216     public void moduleReset(ModuleEvent event)
217     {
218         moduleRemoved(event);
219     }
220 
221     public synchronized void moduleRemoved(ModuleEvent event)
222     {
223 // TODO: Synchronization?
224         // If the module that was removed was chosen for
225         // exporting packages, then flush it from our
226         // data structures.
227         if (m_resolvedModuleMap.get(event.getModule()) != null)
228         {
229             // Remove from module map.
230             m_resolvedModuleMap.remove(event.getModule());
231             // Remove each exported package from package map.
232             Iterator   iter = m_resolvedPackageMap.entrySet().iterator();
233             while (iter.hasNext())
234             {
235                 Map.Entry   entry = (Map.Entry  ) iter.next();
236                 if (entry.getValue() == event.getModule())
237                 {
238                     iter.remove();
239                 }
240             }
241         }
242     }
243 
244     /**
245      * This simple class is used to perform the privileged action of
246      * checking if a bundle has permission to export a package.
247     **/
248     private static class CheckExportPrivileged implements PrivilegedExceptionAction
249     {
250         private URL   m_url = null;
251         private String   m_pkgName = null;
252 
253         public CheckExportPrivileged(URL   url, String   pkgName)
254         {
255             m_url = url;
256             m_pkgName = pkgName;
257         }
258 
259         public Object   run() throws Exception  
260         {
261             // Get permission collection for code source; we cannot
262             // call AccessController.checkPermission() directly since
263             // the bundle's code is not on the access context yet and
264             // might never be if it is only a library bundle, for example.
265             CodeSource cs = new CodeSource(m_url, (Certificate  []) null);
266             PermissionCollection pc = Policy.getPolicy().getPermissions(cs);
267             PackagePermission perm = new PackagePermission(
268                 m_pkgName, PackagePermission.EXPORT);
269             if (!pc.implies(perm))
270             {
271                 throw new AccessControlException("access denied " + perm);
272             }
273 
274             return null;
275         }
276     }
277 }
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