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
|
%%%-------------------------------------------------------------------
%%% File : mod_block_strangers.erl
%%% Author : Alexey Shchepin <alexey@process-one.net>
%%% Purpose : Block packets from non-subscribers
%%% Created : 25 Dec 2016 by Alexey Shchepin <alexey@process-one.net>
%%%
%%%
%%% ejabberd, Copyright (C) 2002-2021 ProcessOne
%%%
%%% 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 2 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, write to the Free Software Foundation, Inc.,
%%% 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
%%%
%%%-------------------------------------------------------------------
-module(mod_block_strangers).
-author('alexey@process-one.net').
-behaviour(gen_mod).
%% API
-export([start/2, stop/1, reload/3, mod_doc/0,
depends/2, mod_opt_type/1, mod_options/1]).
-export([filter_packet/1, filter_offline_msg/1, filter_subscription/2]).
-include_lib("xmpp/include/xmpp.hrl").
-include("logger.hrl").
-include("translate.hrl").
-define(SETS, gb_sets).
-type c2s_state() :: ejabberd_c2s:state().
%%%===================================================================
%%% Callbacks and hooks
%%%===================================================================
start(Host, _Opts) ->
ejabberd_hooks:add(user_receive_packet, Host,
?MODULE, filter_packet, 25),
ejabberd_hooks:add(roster_in_subscription, Host,
?MODULE, filter_subscription, 25),
ejabberd_hooks:add(offline_message_hook, Host,
?MODULE, filter_offline_msg, 25).
stop(Host) ->
ejabberd_hooks:delete(user_receive_packet, Host,
?MODULE, filter_packet, 25),
ejabberd_hooks:delete(roster_in_subscription, Host,
?MODULE, filter_subscription, 25),
ejabberd_hooks:delete(offline_message_hook, Host,
?MODULE, filter_offline_msg, 25).
reload(_Host, _NewOpts, _OldOpts) ->
ok.
-spec filter_packet({stanza(), c2s_state()}) -> {stanza(), c2s_state()} |
{stop, {drop, c2s_state()}}.
filter_packet({#message{from = From} = Msg, State} = Acc) ->
LFrom = jid:tolower(From),
LBFrom = jid:remove_resource(LFrom),
#{pres_a := PresA} = State,
case (?SETS):is_element(LFrom, PresA)
orelse (?SETS):is_element(LBFrom, PresA)
orelse sets_bare_member(LBFrom, PresA) of
false ->
case check_message(Msg) of
allow -> Acc;
deny -> {stop, {drop, State}}
end;
true ->
Acc
end;
filter_packet(Acc) ->
Acc.
-spec filter_offline_msg({_, message()}) -> {_, message()} | {stop, {drop, message()}}.
filter_offline_msg({_Action, #message{} = Msg} = Acc) ->
case check_message(Msg) of
allow -> Acc;
deny -> {stop, {drop, Msg}}
end.
-spec filter_subscription(boolean(), presence()) -> boolean() | {stop, false}.
filter_subscription(Acc, #presence{meta = #{captcha := passed}}) ->
Acc;
filter_subscription(Acc, #presence{from = From, to = To, lang = Lang,
id = SID, type = subscribe} = Pres) ->
LServer = To#jid.lserver,
case mod_block_strangers_opt:drop(LServer) andalso
mod_block_strangers_opt:captcha(LServer) andalso
need_check(Pres) of
true ->
case check_subscription(From, To) of
false ->
BFrom = jid:remove_resource(From),
BTo = jid:remove_resource(To),
Limiter = jid:tolower(BFrom),
case ejabberd_captcha:create_captcha(
SID, BTo, BFrom, Lang, Limiter,
fun(Res) -> handle_captcha_result(Res, Pres) end) of
{ok, ID, Body, CaptchaEls} ->
Msg = #message{from = BTo, to = From,
id = ID, body = Body,
sub_els = CaptchaEls},
case mod_block_strangers_opt:log(LServer) of
true ->
?INFO_MSG("Challenge subscription request "
"from stranger ~ts to ~ts with "
"CAPTCHA",
[jid:encode(From), jid:encode(To)]);
false ->
ok
end,
ejabberd_router:route(Msg);
{error, limit} ->
ErrText = ?T("Too many CAPTCHA requests"),
Err = xmpp:err_resource_constraint(ErrText, Lang),
ejabberd_router:route_error(Pres, Err);
_ ->
ErrText = ?T("Unable to generate a CAPTCHA"),
Err = xmpp:err_internal_server_error(ErrText, Lang),
ejabberd_router:route_error(Pres, Err)
end,
{stop, false};
true ->
Acc
end;
false ->
Acc
end;
filter_subscription(Acc, _) ->
Acc.
-spec handle_captcha_result(captcha_succeed | captcha_failed, presence()) -> ok.
handle_captcha_result(captcha_succeed, Pres) ->
Pres1 = xmpp:put_meta(Pres, captcha, passed),
ejabberd_router:route(Pres1);
handle_captcha_result(captcha_failed, #presence{lang = Lang} = Pres) ->
Txt = ?T("The CAPTCHA verification has failed"),
ejabberd_router:route_error(Pres, xmpp:err_not_allowed(Txt, Lang)).
%%%===================================================================
%%% Internal functions
%%%===================================================================
-spec check_message(message()) -> allow | deny.
check_message(#message{from = From, to = To, lang = Lang} = Msg) ->
LServer = To#jid.lserver,
case need_check(Msg) of
true ->
case check_subscription(From, To) of
false ->
Drop = mod_block_strangers_opt:drop(LServer),
Log = mod_block_strangers_opt:log(LServer),
if
Log ->
?INFO_MSG("~ts message from stranger ~ts to ~ts",
[if Drop -> "Rejecting";
true -> "Allow"
end,
jid:encode(From), jid:encode(To)]);
true ->
ok
end,
if
Drop ->
Txt = ?T("Messages from strangers are rejected"),
Err = xmpp:err_policy_violation(Txt, Lang),
Msg1 = maybe_adjust_from(Msg),
ejabberd_router:route_error(Msg1, Err),
deny;
true ->
allow
end;
true ->
allow
end;
false ->
allow
end.
-spec maybe_adjust_from(message()) -> message().
maybe_adjust_from(#message{type = groupchat, from = From} = Msg) ->
Msg#message{from = jid:remove_resource(From)};
maybe_adjust_from(#message{} = Msg) ->
Msg.
-spec need_check(presence() | message()) -> boolean().
need_check(Pkt) ->
To = xmpp:get_to(Pkt),
From = xmpp:get_from(Pkt),
IsSelf = To#jid.luser == From#jid.luser andalso
To#jid.lserver == From#jid.lserver,
LServer = To#jid.lserver,
IsEmpty = case Pkt of
#message{body = [], subject = []} ->
true;
_ ->
false
end,
IsError = (error == xmpp:get_type(Pkt)),
AllowLocalUsers = mod_block_strangers_opt:allow_local_users(LServer),
Access = mod_block_strangers_opt:access(LServer),
not (IsSelf orelse IsEmpty orelse IsError
orelse acl:match_rule(LServer, Access, From) == allow
orelse ((AllowLocalUsers orelse From#jid.luser == <<"">>)
andalso ejabberd_router:is_my_host(From#jid.lserver))).
-spec check_subscription(jid(), jid()) -> boolean().
check_subscription(From, To) ->
LocalServer = To#jid.lserver,
{RemoteUser, RemoteServer, _} = jid:tolower(From),
case mod_roster:is_subscribed(From, To) of
false when RemoteUser == <<"">> ->
false;
false ->
%% Check if the contact's server is in the roster
mod_block_strangers_opt:allow_transports(LocalServer)
andalso mod_roster:is_subscribed(jid:make(RemoteServer), To);
true ->
true
end.
-spec sets_bare_member(ljid(), ?SETS:set()) -> boolean().
sets_bare_member({U, S, <<"">>} = LBJID, Set) ->
case ?SETS:next(?SETS:iterator_from(LBJID, Set)) of
{{U, S, _}, _} -> true;
_ -> false
end.
depends(_Host, _Opts) ->
[].
mod_opt_type(access) ->
econf:acl();
mod_opt_type(drop) ->
econf:bool();
mod_opt_type(log) ->
econf:bool();
mod_opt_type(captcha) ->
econf:bool();
mod_opt_type(allow_local_users) ->
econf:bool();
mod_opt_type(allow_transports) ->
econf:bool().
mod_options(_) ->
[{access, none},
{drop, true},
{log, false},
{captcha, false},
{allow_local_users, true},
{allow_transports, true}].
mod_doc() ->
#{desc =>
?T("This module allows to block/log messages coming from an "
"unknown entity. If a writing entity is not in your roster, "
"you can let this module drop and/or log the message. "
"By default you'll just not receive message from that entity. "
"Enable this module if you want to drop SPAM messages."),
opts =>
[{access,
#{value => ?T("AccessName"),
desc =>
?T("The option is supposed to be used when 'allow_local_users' "
"and 'allow_transports' are not enough. It's an ACL where "
"'deny' means the message will be rejected (or a CAPTCHA "
"would be generated for a presence, if configured), and "
"'allow' means the sender is whitelisted and the stanza "
"will pass through. The default value is 'none', which "
"means nothing is whitelisted.")}},
{drop,
#{value => "true | false",
desc =>
?T("This option specifies if strangers messages should "
"be dropped or not. The default value is 'true'.")}},
{log,
#{value => "true | false",
desc =>
?T("This option specifies if strangers' messages should "
"be logged (as info message) in ejabberd.log. "
"The default value is 'false'.")}},
{allow_local_users,
#{value => "true | false",
desc =>
?T("This option specifies if strangers from the same "
"local host should be accepted or not. "
"The default value is 'true'.")}},
{allow_transports,
#{value => "true | false",
desc =>
?T("If set to 'true' and some server's JID is in user's "
"roster, then messages from any user of this server "
"are accepted even if no subscription present. "
"The default value is 'true'.")}},
{captcha,
#{value => "true | false",
desc =>
?T("Whether to generate CAPTCHA or not in response to "
"messages from strangers. See also section "
"https://docs.ejabberd.im/admin/configuration/#captcha"
"[CAPTCHA] of the Configuration Guide. "
"The default value is 'false'.")}}]}.
|
