Add access rule to mod_roster (EJAB-72)

doc/guide.tex

@@ -4039,6 +4039,13 @@ Options:
   This option is disabled by default.
   Important: if you use \modsharedroster{} or \modsharedrosterldap{},
   you must disable this option.
+ \titem{access} \ind{options!access}
+   This option can be configured to specify rules to restrict roster management.
+   If a rule returns `deny' on the requested user name,
+   that user cannot modify his personal roster:
+   not add/remove/modify contacts,
+   or subscribe/unsubscribe presence.
+   By default there aren't restrictions.
 \end{description}
 
 This example configuration enables Roster Versioning with storage of current id:
@@ -4051,6 +4058,24 @@ modules:
   ...
 \end{verbatim}
 
+With this example configuration, only admins can manage their rosters;
+everybody else cannot modify the roster:
+\begin{verbatim}
+acl:
+  admin:
+    user:
+      - "sarah": "example.org"
+access:
+  roster:
+    admin: allow
+
+modules:
+  ...
+  mod_roster:
+    access: roster
+  ...
+\end{verbatim}
+
 \makesubsection{modservicelog}{\modservicelog{}}
 \ind{modules!\modservicelog{}}\ind{message auditing}\ind{Bandersnatch}
 

src/ejabberd_c2s.erl

@@ -1879,10 +1879,7 @@ presence_track(From, To, Packet, StateData) ->
 	  A = remove_element(LTo, StateData#state.pres_a),
 	  StateData#state{pres_a = A};
       <<"subscribe">> ->
-	  ejabberd_hooks:run(roster_out_subscription, Server,
+	  try_roster_subscribe(subscribe, User, Server, From, To, Packet, StateData),
-			     [User, Server, To, subscribe]),
-	  check_privacy_route(From, StateData,
-			      jlib:jid_remove_resource(From), To, Packet),
 	  StateData;
       <<"subscribed">> ->
 	  ejabberd_hooks:run(roster_out_subscription, Server,
@@ -1891,10 +1888,7 @@ presence_track(From, To, Packet, StateData) ->
 			      jlib:jid_remove_resource(From), To, Packet),
 	  StateData;
       <<"unsubscribe">> ->
-	  ejabberd_hooks:run(roster_out_subscription, Server,
+	  try_roster_subscribe(unsubscribe, User, Server, From, To, Packet, StateData),
-			     [User, Server, To, unsubscribe]),
-	  check_privacy_route(From, StateData,
-			      jlib:jid_remove_resource(From), To, Packet),
 	  StateData;
       <<"unsubscribed">> ->
 	  ejabberd_hooks:run(roster_out_subscription, Server,
@@ -1943,6 +1937,22 @@ is_privacy_allow(StateData, From, To, Packet, Dir) ->
     allow ==
       privacy_check_packet(StateData, From, To, Packet, Dir).
 
+%%% Check ACL before allowing to send a subscription stanza
+try_roster_subscribe(Type, User, Server, From, To, Packet, StateData) ->
+    JID1 = jlib:make_jid(User, Server, <<"">>),
+    Access = gen_mod:get_module_opt(Server, mod_roster, access, fun(A) when is_atom(A) -> A end, all),
+    case acl:match_rule(Server, Access, JID1) of
+	deny ->
+	    %% Silently drop this (un)subscription request
+	    ok;
+	allow ->
+	    ejabberd_hooks:run(roster_out_subscription,
+			       Server,
+			       [User, Server, To, Type]),
+	    check_privacy_route(From, StateData, jlib:jid_remove_resource(From),
+				To, Packet)
+    end.
+
 %% Send presence when disconnecting
 presence_broadcast(StateData, From, JIDSet, Packet) ->
     JIDs = ?SETS:to_list(JIDSet),

src/mod_roster.erl

@@ -142,7 +142,7 @@ process_iq(From, To, IQ) ->
 
 process_local_iq(From, To, #iq{type = Type} = IQ) ->
     case Type of
-      set -> process_iq_set(From, To, IQ);
+      set -> try_process_iq_set(From, To, IQ);
       get -> process_iq_get(From, To, IQ)
     end.
 
@@ -455,6 +455,16 @@ get_roster_by_jid_t(LUser, LServer, LJID, odbc) ->
 	  end
     end.
 
+try_process_iq_set(From, To, #iq{sub_el = SubEl} = IQ) ->
+    #jid{server = Server} = From,
+    Access = gen_mod:get_module_opt(Server, ?MODULE, access, fun(A) when is_atom(A) -> A end, all),
+    case acl:match_rule(Server, Access, From) of
+	deny ->
+	    IQ#iq{type = error, sub_el = [SubEl, ?ERR_NOT_ALLOWED]};
+	allow ->
+	    process_iq_set(From, To, IQ)
+    end.
+
 process_iq_set(From, To, #iq{sub_el = SubEl} = IQ) ->
     #xmlel{children = Els} = SubEl,
     lists:foreach(fun (El) -> process_item_set(From, To, El)
@@ -1508,7 +1518,7 @@ user_roster_item_parse_query(User, Server, Items,
 				  {value, _} ->
 				      UJID = jlib:make_jid(User, Server,
 							   <<"">>),
-				      process_iq(UJID, UJID,
+				      process_iq_set(UJID, UJID,
 						 #iq{type = set,
 						     sub_el =
 							 #xmlel{name =