1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
|
-module(telnet_server).
-compile(export_all).
%% telnet control characters
-define(SE, 240).
-define(NOP, 241).
-define(DM, 242).
-define(BRK, 243).
-define(IP, 244).
-define(AO, 245).
-define(AYT, 246).
-define(EC, 247).
-define(EL, 248).
-define(GA, 249).
-define(SB, 250).
-define(WILL, 251).
-define(WONT, 252).
-define(DO, 253).
-define(DONT, 254).
-define(IAC, 255).
%% telnet options
-define(BINARY, 0).
-define(ECHO, 1).
-define(SUPPRESS_GO_AHEAD, 3).
-define(TERMINAL_TYPE, 24).
-record(state,
{listen,
client,
users,
authorized=false,
suppress_go_ahead=false,
buffer=[],
break=false}).
-type options() :: [{port,pos_integer()} | {users,users()}].
-type users() :: [{user(),password()}].
-type user() :: string().
-type password() :: string().
-spec start(Opts::options()) -> Pid::pid().
start(Opts) when is_list(Opts) ->
spawn_link(fun() -> init(Opts) end).
-spec stop(Pid::pid()) -> ok.
stop(Pid) ->
Ref = erlang:monitor(process,Pid),
Pid ! stop,
receive {'DOWN',Ref,_,_,_} -> ok end.
init(Opts) ->
Port = proplists:get_value(port,Opts),
Users = proplists:get_value(users,Opts,[]),
{ok, LSock} = listen(5, Port, [list, {packet, 0},
{active, true},
{reuseaddr,true}]),
State = #state{listen=LSock,users=Users},
accept(State),
ok = gen_tcp:close(LSock),
dbg("telnet_server closed the listen socket ~p\n", [LSock]),
timer:sleep(1000),
ok.
listen(0, _Port, _Opts) ->
{error,eaddrinuse};
listen(Retries, Port, Opts) ->
case gen_tcp:listen(Port, Opts) of
{error,eaddrinuse} ->
dbg("Listen port not released, trying again..."),
timer:sleep(5000),
listen(Retries-1, Port, Opts);
Ok = {ok,_LSock} ->
Ok;
Error ->
exit(Error)
end.
accept(#state{listen=LSock}=State) ->
Server = self(),
Acceptor = spawn_link(fun() -> do_accept(LSock,Server) end),
receive
{Acceptor,Sock} when is_port(Sock) ->
dbg("Connected to client on socket ~p\n", [Sock]),
case init_client(State#state{client=Sock}) of
stopped ->
dbg("telnet_server stopped\n"),
ok;
R ->
dbg("Connection to client "
"closed with reason ~p~n",[R]),
accept(State)
end;
{Acceptor,closed} ->
dbg("Listen socket closed unexpectedly, "
"terminating telnet_server\n"),
ok;
stop ->
dbg("telnet_server stopped\n"),
ok
end.
do_accept(LSock,Server) ->
case gen_tcp:accept(LSock) of
{ok, Sock} ->
ok = gen_tcp:controlling_process(Sock,Server),
Server ! {self(),Sock};
{error,closed} ->
%% This will happen when stop/1 is called, since listen
%% socket is closed. Then the server is probably already
%% dead by now, but to be 100% sure not to hang, we send a
%% message to say what happened.
Server ! {self(),closed}
end.
init_client(#state{client=Sock}=State) ->
dbg("Server sending: ~p~n",["login: "]),
R = case gen_tcp:send(Sock,"login: ") of
ok ->
loop(State, 1);
Error ->
Error
end,
_ = gen_tcp:close(Sock),
R.
loop(State, N) ->
receive
{tcp,_,Data} ->
try handle_data(Data,State) of
{ok,State1} ->
loop(State1, N);
closed ->
closed
catch
throw:Error ->
Error
end;
{tcp_closed, _} ->
closed;
{tcp_error,_,Error} ->
{error,tcp,Error};
disconnect ->
Sock = State#state.client,
dbg("Server closing connection on socket ~p~n", [Sock]),
ok = gen_tcp:close(Sock),
closed;
stop ->
stopped
end.
handle_data(Cmd,#state{break=true}=State) ->
dbg("Server got data when in break mode: ~p~n",[Cmd]),
handle_break_cmd(Cmd,State);
handle_data([?IAC|Cmd],State) ->
dbg("Server got cmd: ~p~n",[Cmd]),
handle_cmd(Cmd,State);
handle_data(Data,State) ->
dbg("Server got data: ~p~n",[Data]),
case get_line(Data,[]) of
{Line,Rest} ->
WholeLine = lists:flatten(lists:reverse(State#state.buffer,Line)),
case do_handle_data(WholeLine,State) of
{ok,State1} ->
case Rest of
[] -> {ok,State1};
_ -> handle_data(Rest,State1)
end;
{close,State1} ->
dbg("Server closing connection~n",[]),
gen_tcp:close(State1#state.client),
closed
end;
false ->
{ok,State#state{buffer=[Data|State#state.buffer]}}
end.
%% Add function clause below to handle new telnet commands sent with
%% ?IAC from client. This can be done from ct_telnet:send or
%% ct_telnet:cmd if using the option {newline,false}. Also, ct_telnet
%% sends DONT SUPPRESS_GO_AHEAD.
handle_cmd([?DO,?SUPPRESS_GO_AHEAD|T],State) ->
send([?IAC,?WILL,?SUPPRESS_GO_AHEAD],State),
handle_data(T,State#state{suppress_go_ahead=true});
handle_cmd([?DONT,?SUPPRESS_GO_AHEAD|T],State) ->
send([?IAC,?WONT,?SUPPRESS_GO_AHEAD],State),
handle_data(T,State#state{suppress_go_ahead=false});
handle_cmd([?BRK|T],State) ->
%% Used when testing 'newline' option in ct_telnet:send and ct_telnet:cmd.
send("# ",State),
handle_data(T,State#state{break=true});
handle_cmd([?AYT|T],State) ->
%% Used when testing 'newline' option in ct_telnet:send and ct_telnet:cmd.
send("yes\r\n> ",State),
handle_data(T,State);
handle_cmd([_H|T],State) ->
%% Not responding to this command
handle_cmd(T,State);
handle_cmd([],State) ->
{ok,State}.
handle_break_cmd([$q|T],State) ->
%% Dummy cmd allowed in break mode - quit break mode
send("\r\n> ",State),
handle_data(T,State#state{break=false});
handle_break_cmd([],State) ->
{ok,State}.
%% Add function clause below to handle new text command (text entered
%% from the telnet prompt)
do_handle_data(Data,#state{authorized=false}=State) ->
check_user(Data,State);
do_handle_data(Data,#state{authorized={user,_}}=State) ->
check_pwd(Data,State);
do_handle_data("echo " ++ Data,State) ->
send(Data++"\r\n> ",State),
{ok,State};
do_handle_data("echo_sep " ++ Data,State) ->
Msgs = string:tokens(Data," "),
lists:foreach(fun(Msg) ->
send(Msg,State),
timer:sleep(10)
end, Msgs),
send("\r\n> ",State),
{ok,State};
do_handle_data("echo_no_prompt " ++ Data,State) ->
send(Data,State),
{ok,State};
do_handle_data("echo_ml " ++ Data,State) ->
Lines = string:tokens(Data," "),
ReturnData = string:join(Lines,"\n"),
send(ReturnData++"\r\n> ",State),
{ok,State};
do_handle_data("echo_ml_no_prompt " ++ Data,State) ->
Lines = string:tokens(Data," "),
ReturnData = string:join(Lines,"\n"),
send(ReturnData,State),
{ok,State};
do_handle_data("echo_loop " ++ Data,State) ->
[TStr|Lines] = string:tokens(Data," "),
ReturnData = string:join(Lines,"\n"),
send_loop(list_to_integer(TStr),ReturnData,State),
{ok,State};
do_handle_data("echo_delayed_prompt "++Data,State) ->
[MsStr|EchoData] = string:tokens(Data, " "),
send(string:join(EchoData,"\n"),State),
timer:sleep(list_to_integer(MsStr)),
send("\r\n> ",State),
{ok,State};
do_handle_data("disconnect_after " ++WaitStr,State) ->
Wait = list_to_integer(string:strip(WaitStr,right,$\n)),
dbg("Server will close connection in ~w ms...", [Wait]),
erlang:send_after(Wait,self(),disconnect),
{ok,State};
do_handle_data("disconnect" ++_,State) ->
{close,State};
do_handle_data([],State) ->
send("> ",State),
{ok,State};
do_handle_data(_Data,State) ->
send("error: unknown command\r\n> ",State),
{ok,State}.
check_user(User,State) ->
case lists:keyfind(User,1,State#state.users) of
{User,Pwd} ->
dbg("user ok\n"),
send("Password: ",State),
{ok,State#state{authorized={user,Pwd}}};
false ->
throw({error,unknown_user})
end.
check_pwd(Pwd,#state{authorized={user,Pwd}}=State) ->
dbg("password ok\n"),
send("Welcome to the ultimate telnet server!\r\n> ",State),
{ok,State#state{authorized=true}};
check_pwd(_,_State) ->
throw({error,authentication}).
send(Data,State) ->
dbg("Server sending: ~p~n",[Data]),
case gen_tcp:send(State#state.client,Data) of
ok ->
ok;
{error,Error} ->
throw({error,send,Error})
end.
send_loop(T,Data,State) ->
dbg("Server sending ~p in loop for ~w ms...~n",[Data,T]),
send_loop(os:timestamp(),T,Data,State).
send_loop(T0,T,Data,State) ->
ElapsedMS = trunc(timer:now_diff(os:timestamp(),T0)/1000),
if ElapsedMS >= T ->
ok;
true ->
send(Data,State),
timer:sleep(500),
send_loop(T0,T,Data,State)
end.
get_line([$\r,$\n|Rest],Acc) ->
{lists:reverse(Acc),Rest};
get_line([$\r,0|Rest],Acc) ->
{lists:reverse(Acc),Rest};
get_line([$\n|Rest],Acc) ->
{lists:reverse(Acc),Rest};
get_line([H|T],Acc) ->
get_line(T,[H|Acc]);
get_line([],_) ->
false.
dbg(_F) ->
dbg(_F,[]).
dbg(_F,_A) ->
TS = timestamp(),
io:format("[telnet_server, ~s]\n" ++ _F,[TS|_A]).
timestamp() ->
{MS,S,US} = os:timestamp(),
{{Year,Month,Day}, {Hour,Min,Sec}} =
calendar:now_to_local_time({MS,S,US}),
MilliSec = trunc(US/1000),
lists:flatten(io_lib:format("~4.10.0B-~2.10.0B-~2.10.0B "
"~2.10.0B:~2.10.0B:~2.10.0B.~3.10.0B",
[Year,Month,Day,Hour,Min,Sec,MilliSec])).
|
