GUACAMOLE-289: Add getResource() functions to UserContext and AuthenticationProvider, allowing extensions to expose arbitrary REST resources/services.

guacamole/src/main/java/org/apache/guacamole/extension/AuthenticationProviderFacade.java

@@ -134,6 +134,20 @@ public class AuthenticationProviderFacade implements AuthenticationProvider {
 
     }
 
+    @Override
+    public Object getResource() throws GuacamoleException {
+
+        // Ignore auth attempts if no auth provider could be loaded
+        if (authProvider == null) {
+            logger.warn("The authentication system could not be loaded. Please check for errors earlier in the logs.");
+            return null;
+        }
+
+        // Delegate to underlying auth provider
+        return authProvider.getResource();
+
+    }
+
     @Override
     public AuthenticatedUser authenticateUser(Credentials credentials)
             throws GuacamoleException {

guacamole/src/main/java/org/apache/guacamole/rest/RESTServiceModule.java

@@ -36,6 +36,7 @@ import org.apache.guacamole.rest.auth.SecureRandomAuthTokenGenerator;
 import org.apache.guacamole.rest.auth.TokenSessionMap;
 import org.apache.guacamole.rest.connection.ConnectionModule;
 import org.apache.guacamole.rest.connectiongroup.ConnectionGroupModule;
+import org.apache.guacamole.rest.extension.ExtensionRESTService;
 import org.apache.guacamole.rest.language.LanguageRESTService;
 import org.apache.guacamole.rest.patch.PatchRESTService;
 import org.apache.guacamole.rest.session.SessionResourceFactory;
@@ -84,6 +85,7 @@ public class RESTServiceModule extends ServletModule {
         bindInterceptor(Matchers.any(), new RESTMethodMatcher(), interceptor);
 
         // Set up the API endpoints
+        bind(ExtensionRESTService.class);
         bind(LanguageRESTService.class);
         bind(PatchRESTService.class);
         bind(TokenRESTService.class);

guacamole/src/main/java/org/apache/guacamole/rest/extension/ExtensionRESTService.java

@@ -0,0 +1,104 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.guacamole.rest.extension;
+
+import com.google.inject.Inject;
+import java.util.List;
+import javax.ws.rs.Path;
+import javax.ws.rs.PathParam;
+import org.apache.guacamole.GuacamoleException;
+import org.apache.guacamole.GuacamoleResourceNotFoundException;
+import org.apache.guacamole.net.auth.AuthenticationProvider;
+
+/**
+ * A REST service which provides access to extension-specific REST resources,
+ * each exposed by the identifier of that extension's AuthenticationProvider.
+ */
+@Path("/ext")
+public class ExtensionRESTService {
+
+    /**
+     * All configured authentication providers.
+     */
+    @Inject
+    private List<AuthenticationProvider> authProviders;
+
+    /**
+     * Returns the AuthenticationProvider having the given identifier. If no
+     * such AuthenticationProvider has been loaded, null is returned.
+     *
+     * @param identifier
+     *     The identifier of the AuthenticationProvider to locate.
+     *
+     * @return
+     *     The AuthenticationProvider having the given identifier, or null if
+     *     no such AuthenticationProvider is loaded.
+     */
+    private AuthenticationProvider getAuthenticationProvider(String identifier) {
+
+        // Iterate through all installed AuthenticationProviders, searching for
+        // the given identifier
+        for (AuthenticationProvider authProvider : authProviders) {
+            if (authProvider.getIdentifier().equals(identifier))
+                return authProvider;
+        }
+
+        // No such AuthenticationProvider found
+        return null;
+
+    }
+
+    /**
+     * Returns the arbitrary REST resource exposed by the AuthenticationProvider
+     * having the given identifier.
+     *
+     * @param identifier
+     *     The identifier of the AuthenticationProvider whose REST resource
+     *     should be retrieved.
+     *
+     * @return
+     *     The arbitrary REST resource exposed by the AuthenticationProvider
+     *     having the given identifier.
+     *
+     * @throws GuacamoleException
+     *     If no such resource could be found, or if an error occurs while
+     *     retrieving that resource.
+     */
+    @Path("{identifier}")
+    public Object getExtensionResource(@PathParam("identifier") String identifier)
+            throws GuacamoleException {
+
+        // Retrieve authentication provider having given identifier
+        AuthenticationProvider authProvider = getAuthenticationProvider(identifier);
+        if (authProvider != null) {
+
+            // Pull resource from authentication provider
+            Object resource = authProvider.getResource();
+            if (resource != null)
+                return resource;
+
+        }
+
+        // AuthenticationProvider-specific resource could not be found
+        throw new GuacamoleResourceNotFoundException("No such resource.");
+
+    }
+
+}

guacamole/src/main/java/org/apache/guacamole/rest/extension/package-info.java

@@ -0,0 +1,23 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+/**
+ * Classes related to the arbitrary REST services exposed by extensions.
+ */
+package org.apache.guacamole.rest.extension;

guacamole/src/main/java/org/apache/guacamole/rest/session/UserContextResource.java

@@ -29,6 +29,7 @@ import javax.ws.rs.Path;
 import javax.ws.rs.Produces;
 import javax.ws.rs.core.MediaType;
 import org.apache.guacamole.GuacamoleException;
+import org.apache.guacamole.GuacamoleResourceNotFoundException;
 import org.apache.guacamole.net.auth.ActiveConnection;
 import org.apache.guacamole.net.auth.Connection;
 import org.apache.guacamole.net.auth.ConnectionGroup;
@@ -253,4 +254,29 @@ public class UserContextResource {
         return new SchemaResource(userContext);
     }
 
+    /**
+     * Returns the arbitrary REST resource exposed by the UserContext exposed
+     * by this UserContextResource.
+     *
+     * @return
+     *     The arbitrary REST resource exposed by the UserContext exposed by
+     *     this UserContextresource.
+     *
+     * @throws GuacamoleException
+     *     If no such resource could be found, or if an error occurs while
+     *     retrieving that resource.
+     */
+    @Path("ext")
+    public Object getExtensionResource() throws GuacamoleException {
+
+        // Pull resource from user context
+        Object resource = userContext.getResource();
+        if (resource != null)
+            return resource;
+
+        // UserContext-specific resource could not be found
+        throw new GuacamoleResourceNotFoundException("No such resource.");
+
+    }
+
 }