GUACAMOLE-96: Add API support for augmenting functionality of other extensions.

extensions/guacamole-auth-cas/src/main/java/org/apache/guacamole/auth/cas/CASAuthenticationProvider.java

@@ -107,6 +107,13 @@ public class CASAuthenticationProvider implements AuthenticationProvider {
 
     }
 
+    @Override
+    public UserContext decorate(UserContext context,
+            AuthenticatedUser authenticatedUser, Credentials credentials)
+            throws GuacamoleException {
+        return context;
+    }
+
     @Override
     public void shutdown() {
         // Do nothing

extensions/guacamole-auth-duo/src/main/java/org/apache/guacamole/auth/duo/DuoAuthenticationProvider.java

@@ -102,6 +102,13 @@ public class DuoAuthenticationProvider implements AuthenticationProvider {
         return context;
     }
 
+    @Override
+    public UserContext decorate(UserContext context,
+            AuthenticatedUser authenticatedUser, Credentials credentials)
+            throws GuacamoleException {
+        return context;
+    }
+
     @Override
     public void shutdown() {
         // Do nothing

extensions/guacamole-auth-header/src/main/java/org/apache/guacamole/auth/header/HTTPHeaderAuthenticationProvider.java

@@ -107,6 +107,13 @@ public class HTTPHeaderAuthenticationProvider implements AuthenticationProvider
 
     }
 
+    @Override
+    public UserContext decorate(UserContext context,
+            AuthenticatedUser authenticatedUser, Credentials credentials)
+            throws GuacamoleException {
+        return context;
+    }
+
     @Override
     public void shutdown() {
         // Do nothing

extensions/guacamole-auth-jdbc/modules/guacamole-auth-jdbc-base/src/main/java/org/apache/guacamole/auth/jdbc/InjectedAuthenticationProvider.java

@@ -104,6 +104,13 @@ public abstract class InjectedAuthenticationProvider implements AuthenticationPr
                 authenticatedUser, credentials);
     }
 
+    @Override
+    public UserContext decorate(UserContext context,
+            AuthenticatedUser authenticatedUser, Credentials credentials)
+            throws GuacamoleException {
+        return context;
+    }
+
     @Override
     public void shutdown() {
         // Do nothing

extensions/guacamole-auth-ldap/src/main/java/org/apache/guacamole/auth/ldap/LDAPAuthenticationProvider.java

@@ -103,6 +103,13 @@ public class LDAPAuthenticationProvider implements AuthenticationProvider {
         return context;
     }
 
+    @Override
+    public UserContext decorate(UserContext context,
+            AuthenticatedUser authenticatedUser, Credentials credentials)
+            throws GuacamoleException {
+        return context;
+    }
+
     @Override
     public void shutdown() {
         // Do nothing

extensions/guacamole-auth-openid/src/main/java/org/apache/guacamole/auth/openid/OpenIDAuthenticationProvider.java

@@ -107,6 +107,13 @@ public class OpenIDAuthenticationProvider implements AuthenticationProvider {
 
     }
 
+    @Override
+    public UserContext decorate(UserContext context,
+            AuthenticatedUser authenticatedUser, Credentials credentials)
+            throws GuacamoleException {
+        return context;
+    }
+
     @Override
     public void shutdown() {
         // Do nothing

guacamole-ext/src/main/java/org/apache/guacamole/net/auth/AuthenticationProvider.java

@@ -168,6 +168,40 @@ public interface AuthenticationProvider {
             AuthenticatedUser authenticatedUser,
             Credentials credentials) throws GuacamoleException;
 
+    /**
+     * Given a UserContext which originates from a different
+     * AuthenticationProvider, returns a UserContext instance which decorates
+     * (wraps) that UserContext, delegating and overriding implemented
+     * functions as necessary. Each UserContext created via getUserContext()
+     * or updateUserContext() will be passed to the decorate() functions of all
+     * other AuthenticationProviders, allowing those AuthenticationProviders
+     * to augment (or perhaps even limit) the functionality or data provided.
+     *
+     * @param context
+     *     An existing UserContext generated by a different
+     *     AuthenticationProvider.
+     *
+     * @param authenticatedUser
+     *     The AuthenticatedUser object representing the user associated with
+     *     the given UserContext.
+     *
+     * @param credentials
+     *     The credentials which were most recently submitted for the given
+     *     AuthenticatedUser. These are not guaranteed to be the same as the
+     *     credentials associated with the AuthenticatedUser object, which are
+     *     the credentials provided when the user originally authenticated.
+     *
+     * @return
+     *     A decorated (wrapped) UserContext object, or the original,
+     *     undecorated UserContext.
+     *
+     * @throws GuacamoleException
+     *     If the UserContext cannot be decorated due to an error.
+     */
+    UserContext decorate(UserContext context,
+            AuthenticatedUser authenticatedUser,
+            Credentials credentials) throws GuacamoleException;
+
     /**
      * Frees all resources associated with this AuthenticationProvider. This
      * function will be automatically invoked when the Guacamole server is

guacamole-ext/src/main/java/org/apache/guacamole/net/auth/simple/SimpleAuthenticationProvider.java

@@ -260,6 +260,16 @@ public abstract class SimpleAuthenticationProvider
         
     }
 
+    @Override
+    public UserContext decorate(UserContext context,
+            AuthenticatedUser authenticatedUser, Credentials credentials)
+            throws GuacamoleException {
+
+        // Simply return the given context, decorating nothing
+        return context;
+
+    }
+
     @Override
     public void shutdown() {
         // Do nothing

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

@@ -158,6 +158,20 @@ public class AuthenticationProviderFacade implements AuthenticationProvider {
         
     }
 
+    @Override
+    public UserContext decorate(UserContext context,
+            AuthenticatedUser authenticatedUser,
+            Credentials credentials) throws GuacamoleException {
+
+        // Do nothing if underlying auth provider could not be loaded
+        if (authProvider == null)
+            return context;
+
+        // Delegate to underlying auth provider
+        return authProvider.decorate(context, authenticatedUser, credentials);
+
+    }
+
     @Override
     public void shutdown() {
         if (authProvider != null)