prosody
53e0ae770917
plugins/muc/occupant_id.lib.lua

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plugins/muc/occupant_id.lib.lua @ 12180:53e0ae770917

util.xml: Do not allow doctypes, comments or processing instructions Yes. This is as bad as it sounds. CVE pending. In Prosody itself, this only affects mod_websocket, which uses util.xml to parse the <open/> frame, thus allowing unauthenticated remote DoS using Billion Laughs. However, third-party modules using util.xml may also be affected by this. This commit installs handlers which disallow the use of doctype declarations and processing instructions without any escape hatch. It, by default, also introduces such a handler for comments, however, there is a way to enable comments nontheless. This is because util.xml is used to parse human-facing data, where comments are generally a desirable feature, and also because comments are generally harmless.
author Jonas Schäfer <jonas@wielicki.name>
date Mon, 10 Jan 2022 18:23:54 +0100
parent 12108:e9882c4c397f
child 12977:74b9e05af71e
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rev   line source
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1 -- Implementation of https://xmpp.org/extensions/inbox/occupant-id.html
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2 -- XEP-0421: Anonymous unique occupant identifiers for MUCs
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3
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4 -- (C) 2020 Maxime “pep” Buquet <pep@bouah.net>
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5 -- (C) 2020 Matthew Wild <mwild1@gmail.com>
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6
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7 local uuid = require "util.uuid";
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8 local hmac_sha256 = require "util.hashes".hmac_sha256;
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9 local b64encode = require "util.encodings".base64.encode;
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10
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11 local xmlns_occupant_id = "urn:xmpp:occupant-id:0";
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12
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13 local function get_room_salt(room)
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14 local salt = room._data.occupant_id_salt;
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15 if not salt then
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16 salt = uuid.generate();
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17 room._data.occupant_id_salt = salt;
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18 end
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19 return salt;
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20 end
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21
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22 local function get_occupant_id(room, occupant)
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23 if occupant.stable_id then
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24 return occupant.stable_id;
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25 end
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26
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27 local salt = get_room_salt(room)
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28
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29 occupant.stable_id = b64encode(hmac_sha256(occupant.bare_jid, salt));
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30
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31 return occupant.stable_id;
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32 end
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33
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34 local function update_occupant(event)
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35 local stanza, room, occupant, dest_occupant = event.stanza, event.room, event.occupant, event.dest_occupant;
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36
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37 -- "muc-occupant-pre-change" provides "dest_occupant" but not "occupant".
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38 if dest_occupant ~= nil then
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39 occupant = dest_occupant;
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40 end
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41
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42 -- strip any existing <occupant-id/> tags to avoid forgery
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43 stanza:remove_children("occupant-id", xmlns_occupant_id);
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44
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45 local unique_id = get_occupant_id(room, occupant);
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46 stanza:tag("occupant-id", { xmlns = xmlns_occupant_id, id = unique_id }):up();
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47 end
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48
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49 local function muc_private(event)
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50 local stanza, room = event.stanza, event.room;
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51 local occupant = room._occupants[stanza.attr.from];
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52
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53 update_occupant({
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54 stanza = stanza,
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55 room = room,
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56 occupant = occupant,
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57 });
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58 end
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59
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60 if module:get_option_boolean("muc_occupant_id", true) then
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61 module:add_feature(xmlns_occupant_id);
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62 module:hook("muc-disco#info", function (event)
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63 event.reply:tag("feature", { var = xmlns_occupant_id }):up();
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64 end);
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65
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66 module:hook("muc-broadcast-presence", update_occupant);
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67 module:hook("muc-occupant-pre-join", update_occupant);
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68 module:hook("muc-occupant-pre-change", update_occupant);
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69 module:hook("muc-occupant-groupchat", update_occupant);
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70 module:hook("muc-private-message", muc_private);
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71 end
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72
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73 return {
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74 get_room_salt = get_room_salt;
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75 get_occupant_id = get_occupant_id;
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76 };