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
|
%%%----------------------------------------------------------------------
%%% File : mod_pres_counter.erl
%%% Author : Ahmed Omar
%%% Purpose : Presence subscription flood prevention
%%% Created : 23 Sep 2010 by Ahmed Omar
%%%
%%%
%%% ejabberd, Copyright (C) 2002-2022 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_pres_counter).
-behaviour(gen_mod).
-export([start/2, stop/1, reload/3, check_packet/4,
mod_opt_type/1, mod_options/1, depends/2, mod_doc/0]).
-include("logger.hrl").
-include("translate.hrl").
-include_lib("xmpp/include/xmpp.hrl").
-record(pres_counter,
{dir, start, count, logged = false}).
start(Host, _Opts) ->
ejabberd_hooks:add(privacy_check_packet, Host, ?MODULE,
check_packet, 25),
ok.
stop(Host) ->
ejabberd_hooks:delete(privacy_check_packet, Host,
?MODULE, check_packet, 25),
ok.
reload(_Host, _NewOpts, _OldOpts) ->
ok.
depends(_Host, _Opts) ->
[].
-spec check_packet(allow | deny, ejabberd_c2s:state() | jid(),
stanza(), in | out) -> allow | deny.
check_packet(Acc, #{jid := JID}, Packet, Dir) ->
check_packet(Acc, JID, Packet, Dir);
check_packet(_, #jid{lserver = LServer},
#presence{from = From, to = To, type = Type}, Dir) ->
IsSubscription = case Type of
subscribe -> true;
subscribed -> true;
unsubscribe -> true;
unsubscribed -> true;
_ -> false
end,
if IsSubscription ->
JID = case Dir of
in -> To;
out -> From
end,
update(LServer, JID, Dir);
true -> allow
end;
check_packet(Acc, _, _, _) ->
Acc.
update(Server, JID, Dir) ->
StormCount = mod_pres_counter_opt:count(Server),
TimeInterval = mod_pres_counter_opt:interval(Server),
TimeStamp = erlang:system_time(millisecond),
case read(Dir) of
undefined ->
write(Dir,
#pres_counter{dir = Dir, start = TimeStamp, count = 1}),
allow;
#pres_counter{start = TimeStart, count = Count,
logged = Logged} =
R ->
if TimeStamp - TimeStart > TimeInterval ->
write(Dir,
R#pres_counter{start = TimeStamp, count = 1}),
allow;
(Count =:= StormCount) and Logged -> {stop, deny};
Count =:= StormCount ->
write(Dir, R#pres_counter{logged = true}),
case Dir of
in ->
?WARNING_MSG("User ~ts is being flooded, ignoring received "
"presence subscriptions",
[jid:encode(JID)]);
out ->
IP = ejabberd_sm:get_user_ip(JID#jid.luser,
JID#jid.lserver,
JID#jid.lresource),
?WARNING_MSG("Flooder detected: ~ts, on IP: ~ts ignoring "
"sent presence subscriptions~n",
[jid:encode(JID),
misc:ip_to_list(IP)])
end,
{stop, deny};
true ->
write(Dir,
R#pres_counter{start = TimeStamp, count = Count + 1}),
allow
end
end.
read(K) -> get({pres_counter, K}).
write(K, V) -> put({pres_counter, K}, V).
mod_opt_type(count) ->
econf:pos_int();
mod_opt_type(interval) ->
econf:timeout(second).
mod_options(_) ->
[{count, 5}, {interval, timer:seconds(60)}].
mod_doc() ->
#{desc =>
?T("This module detects flood/spam in presence "
"subscriptions traffic. If a user sends or receives "
"more of those stanzas in a given time interval, "
"the exceeding stanzas are silently dropped, and a "
"warning is logged."),
opts =>
[{count,
#{value => ?T("Number"),
desc =>
?T("The number of subscription presence stanzas "
"(subscribe, unsubscribe, subscribed, unsubscribed) "
"allowed for any direction (input or output) per time "
"defined in 'interval' option. Please note that two "
"users subscribing to each other usually generate 4 "
"stanzas, so the recommended value is '4' or more. "
"The default value is '5'.")}},
{interval,
#{value => "timeout()",
desc =>
?T("The time interval. The default value is '1' minute.")}}],
example =>
["modules:",
" ...",
" mod_pres_counter:",
" count: 5",
" interval: 30 secs",
" ..."]}.
|
