diff --git a/apps/kolab_guam/src/kolab_guam_session.erl b/apps/kolab_guam/src/kolab_guam_session.erl index 3df533e..f548288 100644 --- a/apps/kolab_guam/src/kolab_guam_session.erl +++ b/apps/kolab_guam/src/kolab_guam_session.erl @@ -1,457 +1,453 @@ %% Copyright 2015 Kolab Systems AG (http://www.kolabsys.com) %% %% Aaron Seigo (Kolab Systems) %% %% This program is free software: you can redistribute it and/or modify %% it under the terms of the GNU General Public License as published by %% the Free Software Foundation, either version 3 of the License, or %% (at your option) any later version. %% %% This program is distributed in the hope that it will be useful, %% but WITHOUT ANY WARRANTY; without even the implied warranty of %% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the %% GNU General Public License for more details. %% %% You should have received a copy of the GNU General Public License %% along with this program. If not, see . -module(kolab_guam_session). -behaviour(gen_server). %% API -export([ start_link/6 ]). %% gen_server callbacks -export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, code_change/3]). -include("kolab_guam_session.hrl"). %% public API start_link(SupervisorPID, ListenSocket, ImapConfig, ImplicitTLS, TLSConfig, Rules) -> gen_server:start_link(?MODULE, [SupervisorPID, ListenSocket, ImapConfig, ImplicitTLS, TLSConfig, Rules], []). %% gen_server API init([SupervisorPID, ListenSocket, ServerConfig, ImplicitTLS, TLSConfig, Rules]) -> %% accepting a connection is blocking .. so do it async %% lager:debug("Starting a session handler on socket ~p for listener ~p", [ListenSocket, SupervisorPID]), process_flag(trap_exit, true), ActiveRules = init_rules(Rules), gen_server:cast(self(), accept), %% lager:debug("Rules are ~p from ~p", [ActiveRules, Rules]), { ok, #state{ listen_socket = ListenSocket, super_pid = SupervisorPID, client_implicit_tls = ImplicitTLS, tls_config = TLSConfig, server_config = ServerConfig, rules_deciding = ActiveRules } }. handle_call(_Request, _From, State) -> { reply, ok, State }. handle_cast(accept, State = #state{ server_config = ServerConfig } = State) -> %% try to rate limit our responses a bit here so that hammering the socket with connections is survivable timer:sleep(3), { ok, AcceptSocket, TLSActive } = accept_client(State), { ok, ImapSession } = eimap:start_link(ServerConfig), eimap:connect(ImapSession, self(), server_hello), { noreply, State#state{ listen_socket = undefined, socket = AcceptSocket, imap_session = ImapSession, client_tls_active = TLSActive } }; handle_cast(_Msg, State) -> { noreply, State }. handle_info({ tcp_closed, _Socket }, State) -> %lager:debug("Client closed socket"), { stop, normal, State }; handle_info({ tcp_error, _Socket, _Error }, State) -> %lager:debug("Socket error"), { stop, normal, State }; handle_info({ ssl_closed, _Socket }, State) -> %lager:debug("Client closed socket"), { stop, normal, State }; handle_info({ ssl_error, _Socket, _Error }, State) -> %lager:debug("Socket error"), { stop, normal, State }; handle_info({ tcp, Socket, Data }, #state{ client_tls_active = false } = State) -> %lager:debug("Data coming in from client over TCP ~s", [Data]), process_client_data(Socket, Data, State); handle_info({ ssl, Socket, Data }, State) -> %lager:debug("Data coming in from client over SSL, ~p", [Data]), process_client_data(Socket, Data, State); handle_info({ server_hello, ServerHello }, #state{ imap_session = ImapSession, tls_config = TLSConfig, socket = Socket, client_implicit_tls = ImplicitTLS, client_tls_active = TLSActive, deflator = Deflator } = State) -> CorrectedHello = correct_hello(TLSActive, ImplicitTLS, TLSConfig, ServerHello), ServerIdent = proplists:get_value(server_id, ServerHello, <<>>), FullGreeting = <<"* OK [CAPABILITY ", CorrectedHello/binary, "] ", ServerIdent/binary, "\r\n">>, eimap:start_passthrough(ImapSession, self()), relay_response(Socket, postprocess_server_data(Deflator, FullGreeting), TLSActive), { noreply, State }; handle_info({ { rule_data, Module, ResponseToken }, Data }, #state{ rules_active = ActiveRules } = State) -> %lager:debug("Got back data requested by rule ~p: ~p", [Module, Data]), NewActiveRules = case proplists:get_value(Module, ActiveRules) of undefined -> ActiveRules; ModuleState -> NewModuleState = Module:imap_data(ResponseToken, Data, ModuleState), lists:reverse(lists:foldl(fun({ Rule, RuleState }, Acc) -> case Rule =:= Module of true -> [{ Rule, NewModuleState }|Acc]; _ -> [{ Rule, RuleState }|Acc] end end, [], ActiveRules)) end, %TODO: should we also support non-active rules doing imapy things here? { noreply, State#state{ rules_active = NewActiveRules } }; handle_info({ imap_server_response, Data }, #state{ socket = Socket, imap_session = ImapSession, client_tls_active = TLS, deflator = Deflator, rules_active = ActiveRules } = State) -> lager:debug("FROM SERVER: ~p", [Data]), { ModifiedData, CurrentlyActiveRules } = apply_ruleset_serverside(ImapSession, Data, ActiveRules), relay_response(Socket, postprocess_server_data(Deflator, ModifiedData), TLS), NewSplitCommand = update_split_command_state(ModifiedData, State), { noreply, State#state{ rules_active = CurrentlyActiveRules, current_command_split = NewSplitCommand } }; handle_info({ 'EXIT', PID, _Reason }, #state { imap_session = PID } = State) -> { stop, normal, State#state{ imap_session = undefined } }; handle_info(Info, State) -> lager:debug("Received unexpected info... ~p", [Info]), { noreply, State }. terminate(_Reason, #state{ inflator = Inflator, imap_session = ImapSession, deflator = Deflator, socket = Socket, client_implicit_tls = ImplicitTLS, client_tls_active = TLS }) -> close_zlib_handle(Inflator), close_zlib_handle(Deflator), close_socket(ImplicitTLS, TLS, Socket), case ImapSession of undefined -> ok; _ -> exit(ImapSession, kill) end, ok. code_change(_OldVsn, State, _Extra) -> { ok, State }. %% private API %% update_split_command_state updates the split_command being held on to when we get a server response %% in the case of "transactional" messages (such as authentication) where the client and server enter a bidirectional conversation %% that is goverened by rules outside the the usual IMAP call/response pattern, we need to wait for the end of the server response %% since this is relatively expensive due to having to scan the data for the tagged server response, and is not necessary for all other %% IMAP commands, we shortcircuit when the command does not trigger a "transactional" interaction between client and server, and instead %% just always reset the split data state at that point update_split_command_state(Data, #state{ command_split_reset_trigger = reset_on_server_response, current_command_split = CurrentCommandSplit }) -> case CurrentCommandSplit of undefined -> undefined; { Tag, _Command, _Data } -> case binary:match(Data, <>) of nomatch -> CurrentCommandSplit; { 0, _ } -> undefined; { Start, _ } -> case binary:at(Data, Start - 1) of $\n -> undefined; _ -> CurrentCommandSplit end end end; update_split_command_state(_Data, _State) -> undefined. update_split_command_state_client(ClientDataComponents, #state{ command_split_reset_trigger = reset_for_next_client_command, current_command_split = CurrentCommandSplit }) -> %If we have a currently active command (CurrentCommandSplit), then we reset only if we find a new command (and not just on any new line). %This is relevant for multi-line commands such as APPEND, which follow up with a continuation which we want to avoid buffering. case CurrentCommandSplit of undefined -> undefined; _ -> case ClientDataComponents of { <<>>, <<>>, <<>> } -> CurrentCommandSplit; { _Tag, <<>>, <<>> } -> CurrentCommandSplit; { <<>>, Command, <<>> } -> CurrentCommandSplit; { _Tag, Command, _Data } -> undefined end end; update_split_command_state_client(_ClientDataComponents, _State) -> undefined. accept_client(#state{ client_implicit_tls = true, tls_config = TLSConfig, listen_socket = ListenSocket, super_pid = SupervisorPID }) -> AcceptSocket = accept_socket(ListenSocket, SupervisorPID), %% prep for the next listen { ok, SSLSocket } = ssl:ssl_accept(AcceptSocket, TLSConfig), ok = ssl:setopts(SSLSocket, [{ active, once }, { mode, binary }]), % lager:info("~p All done!", [self()]), { ok, SSLSocket, true }; accept_client(#state{ listen_socket = ListenSocket, super_pid = SupervisorPID }) -> AcceptSocket = accept_socket(ListenSocket, SupervisorPID), ok = inet:setopts(AcceptSocket, [{ active, once }, { mode, binary }]), { ok, AcceptSocket, false }. accept_socket(ListenSocket, SupervisorPID) -> AcceptResult = gen_tcp:accept(ListenSocket), %% start a new accepting process to replace this one, which is now in use supervisor:start_child(SupervisorPID, []), %% assert that the accept worked { ok, AcceptSocket } = AcceptResult, AcceptSocket. close_zlib_handle(undefined) -> ok; close_zlib_handle(Z) -> zlib:close(Z). close_socket(_ImplicitTLS, _TLS, undefined) -> ok; close_socket(_ImplicitTLS, true, Socket) -> ssl:close(Socket); close_socket(true, _TLS, Socket) -> ssl:close(Socket); close_socket(_ImplicitTLS, _TLS, Socket) -> gen_tcp:close(Socket). -read_line(Data) -> - case binary:match(Data, <<"\r\n">>) of - nomatch -> - {Data, <<>>}; - {SplitPos, SplitSize} -> - split_binary(Data, SplitPos + SplitSize) - end. - - - - -process_preprocessed_client_data(Socket, <<>>, State) -> +process_lines(Socket, State, [<<>>]) -> State; +process_lines(Socket, State, [Line|MoreLines]) -> + NewState = process_client_line(<>/binary>>, Socket, State), + process_lines(Socket, NewState, MoreLines). + process_preprocessed_client_data(Socket, PreprocessData, State) -> - {Line, Remainder} = read_line(PreprocessData), - NewState = process_client_line(Line, Socket, State), - process_preprocessed_client_data(Socket, Remainder, NewState). + { FullLinesBuffer, NewLastPartialLine } = eimap_utils:only_full_lines(PreprocessData), + Lines = binary:split(FullLinesBuffer, <<"\r\n">>, [global]), + NewState = process_lines(Socket, State, Lines), + process_client_line(NewLastPartialLine, Socket, NewState). % Client data is processed as it comes in, but split up by lines if more than one line comes in at a time. % The processing interanly buffers data as necessary if it encounters incomplete lines. process_client_data(Socket, Data, #state{ inflator = Inflator } = State) -> % TODO: refactor so starttls and compress commands can be made into rules PreprocessData = preprocess_client_data(Inflator, Data, State), lager:debug("FROM CLIENT: ~p", [PreprocessData]), { noreply, process_preprocessed_client_data(Socket, PreprocessData, State) }. +process_client_line(<<>>, Socket, State) -> + State; process_client_line(Data, Socket, #state{ rules_deciding = UndecidedRules, tls_config = TLSConfig, client_tls_active = TLS, rules_active = ActiveRules, socket = Socket, imap_session = ImapSession, inflator = Inflator, deflator = Deflator, server_config = ServerConfig, current_command_split = CurrentCommandSplit, command_split_reset_trigger = CurrentCommandSplitResetTrigger} = State) -> ClientDataComponents = eimap_utils:split_command_into_components(Data), { TLSActive, CurrentSocket, CurrentInflator, CurrentDeflator, CurrentUndecidedRules, CurrentActiveRules, DataToBuffer, SplitCommand, SplitResetTrigger } = case check_for_transmission_change_commands(TLS, TLSConfig, ClientDataComponents, Deflator, Socket) of { socket_upgraded, SSLSocket } -> %% if we have upgraded our socket, then do so to the backend if that hasn't happened auomatically case proplists:get_value(implicit_tls, ServerConfig, false) of false -> eimap:starttls(ImapSession, undefined, undefined); _ -> ok end, { true, SSLSocket, Inflator, Deflator, UndecidedRules, ActiveRules, <<>>, undefined, undefined }; { compression, NewInflator, NewDeflator } -> eimap:compress(ImapSession), % TODO: make optional { TLS, Socket, NewInflator, NewDeflator, UndecidedRules, ActiveRules, <<>>, undefined, undefined }; nochange -> %We first check if we have to reset the split command before we process the new command in apply_ruleset_clientside NewSplit = update_split_command_state_client(ClientDataComponents, State), { ModifiedData, NewSplitCommand, NewSplitResetTrigger, NewUndecidedRules, NewActiveRules, PostAction } = apply_ruleset_clientside(ImapSession, Socket, Data, ClientDataComponents, NewSplit, UndecidedRules, ActiveRules), BufferThisData = case PostAction of perform_passthrough -> eimap:passthrough_data(ImapSession, ModifiedData), <<>>; buffer_data -> Data end, { TLS, Socket, Inflator, Deflator, NewUndecidedRules, NewActiveRules, BufferThisData, NewSplitCommand, NewSplitResetTrigger } end, set_socket_active(TLSActive, CurrentSocket), State#state{ rules_deciding = CurrentUndecidedRules, rules_active = CurrentActiveRules, socket = CurrentSocket, client_tls_active = TLSActive, inflator = CurrentInflator, deflator = CurrentDeflator, buffered_client_data = DataToBuffer, current_command_split = SplitCommand, command_split_reset_trigger = SplitResetTrigger }. preprocess_client_data(undefined, Data, #state{ buffered_client_data = Buffered }) -> <>; preprocess_client_data(Z, Data, #state{ buffered_client_data = Buffered }) -> Inflated = iolist_to_binary(zlib:inflate(Z, Data)), <>. postprocess_server_data(undefined, Data) -> %% we aren't compressing so there is nothing to do Data; postprocess_server_data(Z, Data) -> iolist_to_binary(zlib:deflate(Z, Data, sync)). init_rules(RuleConfig) -> init_rule(RuleConfig, []). init_rule([], Acc) -> Acc; init_rule([{ RuleName, Config }|RuleConfig], Acc) -> Module = full_rule_name(RuleName), %% we try to new the module, but if something goes wrong, e.g. it does not exist, %% then we skip this config block because it is BROKEN try Module:new(Config) of ModuleState -> init_rule(RuleConfig, [{ Module, ModuleState }|Acc]) catch Type:Error -> lager:warning("Could not create rule for ~p due to failure: ~p ~p", [RuleName, Type, Error]), init_rule(RuleConfig, Acc) end; init_rule([_|RuleConfig], Acc) -> init_rule(RuleConfig, Acc). full_rule_name(Module) when is_atom(Module) -> list_to_atom("kolab_guam_rule_" ++ atom_to_list(Module)). apply_ruleset_serverside(ImapSession, ServerData, CurrentlyActiveRules) -> %TODO: allow undecided rules to opt-in here as well apply_next_rule_serverside(ImapSession, ServerData, [], CurrentlyActiveRules). apply_next_rule_serverside(_ImapSession, ServerData, ActiveRulesAcc, []) -> { ServerData, lists:reverse(ActiveRulesAcc) }; apply_next_rule_serverside(ImapSession, ServerData, ActiveRulesAcc, [{ Module, RuleState } | ActiveRules]) -> %TODO: allow rules to remove themselves from the action during serverside processing? { ModifiedData, ModifiedRuleState } = Module:apply_to_server_message(ImapSession, ServerData, RuleState), apply_next_rule_serverside(ImapSession, ModifiedData, [{ Module, ModifiedRuleState } | ActiveRulesAcc], ActiveRules). apply_ruleset_clientside(_ImapSession, _Socket, ClientData, ClientDataComponents, _CurrentCommandSplit, [], []) -> { ClientData, undefined, [], [], [], perform_passthrough }; apply_ruleset_clientside(ImapSession, Socket, ClientData, ClientDataComponents, CurrentCommandSplit, UndecidedRules, CurrentlyActiveRules) -> { PostAction, SplitCommand, SplitResetTrigger } = case CurrentCommandSplit of undefined -> case ClientDataComponents of % In case of an empty line ("\r\n") the line is complete (doesn't need to be buffered), but there is also no command or tag. { <<>>, <<>>, <<>> } -> { perform_passthrough, CurrentCommandSplit, reset_for_next_client_command }; { _Tag, <<>>, <<>> } -> { buffer_data, undefined, reset_for_next_client_command }; { _Tag, Command, _Data } = Split -> { perform_passthrough, Split, when_to_reset_split(Command) } end; _ -> { perform_passthrough, CurrentCommandSplit, reset_for_next_client_command } end, { StillUndecided, NewlyActive } = check_undecided(Socket, ClientData, SplitCommand, UndecidedRules), ActiveRules = CurrentlyActiveRules ++ NewlyActive, %lager:info("Active Rules: ~p", [ActiveRules]), { ModifiedData, ActiveRulesRun } = apply_next_rule_clientside(ImapSession, ClientData, SplitCommand, [], ActiveRules), { ModifiedData, SplitCommand, SplitResetTrigger, StillUndecided, ActiveRulesRun, PostAction }. when_to_reset_split(<<"AUTHENTICATE">>) -> reset_on_server_response; when_to_reset_split(<<"authenticate">>) -> reset_on_server_response; when_to_reset_split(_) -> reset_for_next_client_command. check_undecided(_Socket, _ClientData, undefined, Rules) -> %% if we do not have a properly split command ... do nothing! { Rules, [] }; check_undecided(Socket, ClientData, SplitCommand, Rules) -> check_next_undecided_rule(Socket, ClientData, SplitCommand, Rules, { [], [] }). check_next_undecided_rule(_Socket, _ClientData, _SplitCommand, [], Accs) -> Accs; check_next_undecided_rule(Socket, ClientData, SplitCommand, [Rule|Rules], { UndecidedAcc, NewActiveAcc }) -> { Module, RuleState } = Rule, %%lager:debug("Does ~p apply with state ~p? let's find out!", [Module, RuleState]), Application = Module:applies(Socket, ClientData, SplitCommand, RuleState), check_next_undecided_rule(Socket, ClientData, SplitCommand, Rules, applies(Module, Application, UndecidedAcc, NewActiveAcc)). applies(Module, { true, RuleState }, UndecidedAcc, NewActiveAcc) -> { UndecidedAcc, [{ Module, RuleState }|NewActiveAcc] }; applies(_Module, { false, _RuleState }, UndecidedAcc, NewActiveAcc) -> { UndecidedAcc, NewActiveAcc }; applies(Module, { notyet, RuleState }, UndecidedAcc, NewActiveAcc) -> { [{ Module, RuleState }|UndecidedAcc], NewActiveAcc }. apply_next_rule_clientside(_ImapSession, ClientData, _SplitCommand, ActiveRulesAcc, []) -> { ClientData, lists:reverse(ActiveRulesAcc) }; apply_next_rule_clientside(ImapSession, ClientData, SplitCommand, ActiveRulesAcc, [{ Module, RuleState }|Rules]) -> { Data, NewState } = Module:apply_to_client_message(ImapSession, ClientData, SplitCommand, RuleState), apply_next_rule_clientside(ImapSession, Data, SplitCommand, [{ Module, NewState } | ActiveRulesAcc], Rules). relay_response(Socket, Data, false) -> %lager:debug("Sending over non-secure socket ..."), gen_tcp:send(Socket, Data); relay_response(Socket, Data, _TLS) -> %lager:debug("Sending over TLS!"), ssl:send(Socket, Data). check_for_transmission_change_commands(TLS, TLSConfig, ClientDataComponents, Deflator, Socket) -> {Tag, Command, _Data } = ClientDataComponents, case check_tls_state(TLS, TLSConfig, Command, Deflator, Socket, Tag) of nochange -> check_compress_request(Deflator, Command, Socket, TLS, Tag); Response -> Response end. check_tls_state(false, TLSConfig, <<"STARTTLS">>, Deflator, Socket, Tag) -> start_client_tls(TLSConfig, Deflator, Socket, Tag); check_tls_state(false, TLSConfig, <<"starttls">>, Deflator, Socket, Tag) -> start_client_tls(TLSConfig, Deflator, Socket, Tag); check_tls_state(_TLS, _TLSConfig, _Buffer, _Deflator, _Socket, _Tag) -> nochange. start_client_tls(TLSConfig, Deflator, Socket, Tag) -> Response = <>, relay_response(Socket, postprocess_server_data(Deflator, Response), false), inet:setopts(Socket, [{ active, false }]), %% must be set to active false, otherwise can fail depending on timing { ok, SSLSocket } = ssl:ssl_accept(Socket, TLSConfig), { socket_upgraded, SSLSocket }. check_compress_request(undefined, <<"COMPRESS">>, Socket, TLS, Tag) -> start_client_compression(Socket, TLS, Tag); check_compress_request(undefined, <<"compress">>, Socket, TLS, Tag) -> start_client_compression(Socket, TLS, Tag); check_compress_request(_Deflator, _Command, _Socket, _TLS, _Tag) -> nochange. start_client_compression(Socket, TLS, Tag) -> Response = <>, relay_response(Socket, postprocess_server_data(undefined, Response), TLS), %% create an inflate/deflate pair for use with the client Inflator = zlib:open(), ok = zlib:inflateInit(Inflator, -15), Deflator = zlib:open(), ok = zlib:deflateInit(Deflator, 1, deflated, -15, 8, default), { compression, Inflator, Deflator }. set_socket_active(true, Socket) -> ssl:setopts(Socket, [{ active, once }]); set_socket_active(_, Socket) -> inet:setopts(Socket, [{ active, once }]). -spec correct_hello(TLSActive :: true | false, ImplicitTLS :: true | false, TlSConfig :: [] | list(), ServerHello :: binary()) -> CorrectedHello :: binary(). correct_hello(true, true, _TLSConfig, ServerResponse) -> % the connection is already secured, so don't advertise starttls to the client ensure_hello_does_not_have_starttls(ServerResponse); correct_hello(true, _ImplicitTLS, _TLSConfig, ServerResponse) -> % the connection is already secured, so don't advertise starttls to the client ensure_hello_does_not_have_starttls(ServerResponse); correct_hello(_TLSActive, _ImplicitTLS, [], ServerResponse) -> % guam does not have a TLS config and so can not provide TLS to the client ensure_hello_does_not_have_starttls(ServerResponse); correct_hello(_TLSActive, _ImplicitTLS, _TLSConfig, ServerResponse) -> % guam has a TLS config, and it is not currently active, so make sure to include % STARTTLS in our response regardless of what the backend says ensure_hello_has_starttls(ServerResponse). ensure_hello_has_starttls(ServerResponse) -> ServerHello = proplists:get_value(capabilities, ServerResponse, <<>>), case binary:match(ServerHello, <<"STARTTLS">>) of nomatch -> add_starttls_to_capabilities(ServerHello); _ -> ServerHello end. add_starttls_to_capabilities(ServerHello) -> case binary:match(ServerHello, <<"CAPABILITY ">>) of nomatch -> add_starttls_after_imap4_atom(ServerHello); { Start, End } -> Prefix = binary:part(ServerHello, 0, Start + End), Suffix = binary:part(ServerHello, Start + End, size(ServerHello) - Start - End), CorrectHello = <>, remove_auth_offers(CorrectHello) end. add_starttls_after_imap4_atom(ServerHello) -> case binary:match(ServerHello, <<"IMAP4rev1 ">>) of nomatch -> <<"STARTTLS ", ServerHello/binary>>; { Start, End } -> Prefix = binary:part(ServerHello, 0, Start + End), Suffix = binary:part(ServerHello, Start + End, size(ServerHello) - Start - End), CorrectHello = <>, remove_auth_offers(CorrectHello) end. ensure_hello_does_not_have_starttls(ServerResponse) -> ServerHello = proplists:get_value(capabilities, ServerResponse, <<>>), case binary:match(ServerHello, <<"STARTTLS">>) of nomatch -> ServerHello; { Start, End } -> Prefix = binary:part(ServerHello, 0, Start), Suffix = binary:part(ServerHello, Start + End, size(ServerHello) - Start - End), <> end. remove_auth_offers(ServerHello) -> case binary:match(ServerHello, <<"AUTH=">>) of nomatch -> ensure_advertise_login_disabled(ServerHello); { Start, _End } -> Prefix = binary:part(ServerHello, 0, Start), Suffix = case binary:match(ServerHello, <<" ">>, [{ scope, { Start, size(ServerHello) - Start } }]) of nomatch -> %% end of the line, so no suffix <<>>; { SpaceStart, SpaceEnd } -> binary:part(ServerHello, SpaceStart + SpaceEnd, size(ServerHello) - SpaceStart - SpaceEnd) end, remove_auth_offers(<>) end. ensure_advertise_login_disabled(ServerHello) -> case binary:match(ServerHello, <<"LOGINDISABLED">>) of nomatch -> <>; _ -> ServerHello end.