JWT enhancement (#3460)

* ref: run the default JWT verifier as hook callback

* ref: add system timestamp to JWT debug log

src/ejabberd_auth_jwt.erl

@@ -33,6 +33,8 @@
 	 store_type/1, plain_password_required/1,
          user_exists/2, use_cache/1
         ]).
+%% 'ejabberd_hooks' callback:
+-export([check_decoded_jwt/5]).
 
 -include_lib("xmpp/include/xmpp.hrl").
 -include("logger.hrl").
@@ -41,6 +43,12 @@
 %%% API
 %%%----------------------------------------------------------------------
 start(Host) ->
+    %% We add our default JWT verifier with hook priority 100.
+    %% So if you need to check or verify your custom JWT before the 
+    %% default verifier, It's better to use this hook with priority 
+    %% little than 100 and return bool() or {stop, bool()} in your own 
+    %% callback function.
+    ejabberd_hooks:add(check_decoded_jwt, Host, ?MODULE, check_decoded_jwt, 100),
     case ejabberd_option:jwt_key(Host) of
 	undefined ->
 	    ?ERROR_MSG("Option jwt_key is not configured for ~ts: "
@@ -49,7 +57,8 @@ start(Host) ->
 	    ok
     end.
 
-stop(_Host) -> ok.
+stop(Host) ->
+    ejabberd_hooks:delete(check_decoded_jwt, Host, ?MODULE, check_decoded_jwt, 100).
 
 plain_password_required(_Host) -> true.
 
@@ -81,36 +90,47 @@ user_exists(_User, _Host) -> {nocache, false}.
 use_cache(_) ->
     false.
 
+%%%----------------------------------------------------------------------
+%%% 'ejabberd_hooks' callback
+%%%----------------------------------------------------------------------
+check_decoded_jwt(true, Fields, _Signature, Server, User) ->
+    JidField = ejabberd_option:jwt_jid_field(Server),
+    case maps:find(JidField, Fields) of
+        {ok, SJid} when is_binary(SJid) ->
+            try
+                JID = jid:decode(SJid),
+                JID#jid.luser == User andalso JID#jid.lserver == Server
+            catch error:{bad_jid, _} ->
+                false
+            end;
+        _ -> % error | {ok, _UnknownType}
+            false
+    end;
+check_decoded_jwt(Acc, _, _, _, _) ->
+    Acc.
+
 %%%----------------------------------------------------------------------
 %%% Internal functions
 %%%----------------------------------------------------------------------
 check_jwt_token(User, Server, Token) ->
     JWK = ejabberd_option:jwt_key(Server),
-    JidField = ejabberd_option:jwt_jid_field(Server),
     try jose_jwt:verify(JWK, Token) of
         {true, {jose_jwt, Fields}, Signature} ->
-            ?DEBUG("jwt verify: ~p - ~p~n", [Fields, Signature]),
+            Now = erlang:system_time(second),
+            ?DEBUG("jwt verify at system timestamp ~p: ~p - ~p~n", [Now, Fields, Signature]),
 	    case maps:find(<<"exp">>, Fields) of
                 error ->
 		    %% No expiry in token => We consider token invalid:
 		    false;
                 {ok, Exp} ->
-                    Now = erlang:system_time(second),
                     if
                         Exp > Now ->
-                            case maps:find(JidField, Fields) of
-                                error ->
-                                    false;
-                                {ok, SJID} ->
-                                    try jid:decode(SJID) of
-                                        JID ->
-                                            (JID#jid.luser == User) andalso
-                                            (JID#jid.lserver == Server) andalso
-                                            ejabberd_hooks:run_fold(check_decoded_jwt, Server, true, [Fields, Signature, User])
-                                    catch error:{bad_jid, _} ->
-                                            false
-                                    end
-                            end;
+                            ejabberd_hooks:run_fold(
+                                check_decoded_jwt,
+                                Server,
+                                true,
+                                [Fields, Signature, Server, User]
+                            );
                         true ->
                             %% return false, if token has expired
                             false
@@ -122,4 +142,3 @@ check_jwt_token(User, Server, Token) ->
         error:{badarg, _} ->
             false
     end.
-