prosody-modules
259ffdbf8906
mod_anti_spam/mod_anti_spam.lua

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mod_anti_spam/mod_anti_spam.lua @ 5883:259ffdbf8906

mod_anti_spam: New module for spam filtering (pre-alpha)
author Matthew Wild <mwild1@gmail.com>
date Tue, 05 Mar 2024 18:26:29 +0000
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equal deleted inserted replaced
5882:761142ee0ff2 5883:259ffdbf8906
1 local ip = require "util.ip";
2 local jid_bare = require "util.jid".bare;
3 local jid_split = require "util.jid".split;
4 local set = require "util.set";
5 local sha256 = require "util.hashes".sha256;
6 local st = require"util.stanza";
7 local is_contact_subscribed = require "core.rostermanager".is_contact_subscribed;
8 local full_sessions = prosody.full_sessions;
9
10 local user_exists = require "core.usermanager".user_exists;
11
12 local new_rtbl_subscription = module:require("rtbl").new_rtbl_subscription;
13 local trie = module:require("trie");
14
15 local spam_source_domains = set.new();
16 local spam_source_ips = trie.new();
17 local spam_source_jids = set.new();
18
19 local count_spam_blocked = module:metric("counter", "anti_spam_blocked", "stanzas", "Stanzas blocked as spam", {"reason"});
20
21 function block_spam(event, reason, action)
22 event.spam_reason = reason;
23 event.spam_action = action;
24 if module:fire_event("spam-blocked", event) == false then
25 module:log("debug", "Spam allowed by another module");
26 return;
27 end
28
29 count_spam_blocked:with_labels(reason):add(1);
30
31 if action == "bounce" then
32 module:log("debug", "Bouncing likely spam %s from %s (%s)", event.stanza.name, event.stanza.attr.from, reason);
33 event.origin.send(st.error_reply("cancel", "policy-violation", "Rejected as spam"));
34 else
35 module:log("debug", "Discarding likely spam %s from %s (%s)", event.stanza.name, event.stanza.attr.from, reason);
36 end
37
38 return true;
39 end
40
41 function is_from_stranger(from_jid, event)
42 local stanza = event.stanza;
43 local to_user, to_host, to_resource = jid_split(stanza.attr.to);
44
45 if not to_user then return false; end
46
47 local to_session = full_sessions[stanza.attr.to];
48 if to_session then return false; end
49
50 if not is_contact_subscribed(to_user, to_host, from_jid) then
51 -- Allow all messages from your own jid
52 if from_jid == to_user.."@"..to_host then
53 return false; -- Pass through
54 end
55 if to_resource and stanza.attr.type == "groupchat" then
56 return false; -- Pass through
57 end
58 return true; -- Stranger danger
59 end
60 end
61
62 function is_spammy_server(session)
63 if spam_source_domains:contains(session.from_host) then
64 return true;
65 end
66 local origin_ip = ip.new(session.ip);
67 if spam_source_ips:contains_ip(origin_ip) then
68 return true;
69 end
70 end
71
72 function is_spammy_sender(sender_jid)
73 return spam_source_jids:contains(sha256(sender_jid, true));
74 end
75
76 local spammy_strings = module:get_option_array("anti_spam_block_strings");
77 local spammy_patterns = module:get_option_array("anti_spam_block_patterns");
78
79 function is_spammy_content(stanza)
80 -- Only support message content
81 if stanza.name ~= "message" then return; end
82 if not (spammy_strings or spammy_patterns) then return; end
83
84 local body = stanza:get_child_text("body");
85 if spammy_strings then
86 for _, s in ipairs(spammy_strings) do
87 if body:find(s, 1, true) then
88 return true;
89 end
90 end
91 end
92 if spammy_patterns then
93 for _, s in ipairs(spammy_patterns) do
94 if body:find(s) then
95 return true;
96 end
97 end
98 end
99 end
100
101 -- Set up RTBLs
102
103 local anti_spam_services = module:get_option_array("anti_spam_services");
104
105 for _, rtbl_service_jid in ipairs(anti_spam_services) do
106 new_rtbl_subscription(rtbl_service_jid, "spam_source_domains", {
107 added = function (item)
108 spam_source_domains:add(item);
109 end;
110 removed = function (item)
111 spam_source_domains:remove(item);
112 end;
113 });
114 new_rtbl_subscription(rtbl_service_jid, "spam_source_ips", {
115 added = function (item)
116 spam_source_ips:add_subnet(ip.parse_cidr(item));
117 end;
118 removed = function (item)
119 spam_source_ips:remove_subnet(ip.parse_cidr(item));
120 end;
121 });
122 new_rtbl_subscription(rtbl_service_jid, "spam_source_jids_sha256", {
123 added = function (item)
124 spam_source_jids:add(item);
125 end;
126 removed = function (item)
127 spam_source_jids:remove(item);
128 end;
129 });
130 end
131
132 module:hook("message/bare", function (event)
133 local to_bare = jid_bare(event.stanza.attr.to);
134
135 if not user_exists(to_bare) then return; end
136
137 local from_bare = jid_bare(event.stanza.attr.from);
138 if not is_from_stranger(from_bare, event) then return; end
139
140 if is_spammy_server(event.origin) then
141 return block_spam(event, "known-spam-source", "drop");
142 end
143
144 if is_spammy_sender(from_bare) then
145 return block_spam(event, "known-spam-jid", "drop");
146 end
147
148 if is_spammy_content(event.stanza) then
149 return block_spam(event, "spam-content", "drop");
150 end
151 end, 500);
152
153 module:hook("presence/bare", function (event)
154 if event.stanza.type ~= "subscribe" then
155 return;
156 end
157
158 if is_spammy_server(event.origin) then
159 return block_spam(event, "known-spam-source", "drop");
160 end
161
162 if is_spammy_sender(event.stanza) then
163 return block_spam(event, "known-spam-jid", "drop");
164 end
165 end, 500);