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prosody
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plugins/muc/subject.lib.lua @ 12181:783056b4e448 0.11 0.11.12
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 | 11128:c3eefb517b7b |
child | 11141:a5acd6354845 |
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-- Prosody IM -- Copyright (C) 2008-2010 Matthew Wild -- Copyright (C) 2008-2010 Waqas Hussain -- Copyright (C) 2014 Daurnimator -- -- This project is MIT/X11 licensed. Please see the -- COPYING file in the source package for more information. -- local st = require "util.stanza"; local dt = require "util.datetime"; local muc_util = module:require "muc/util"; local valid_roles = muc_util.valid_roles; local function create_subject_message(from, subject) return st.message({from = from; type = "groupchat"}) :tag("subject"):text(subject or ""):up(); end local function get_changesubject(room) return room._data.changesubject; end local function set_changesubject(room, changesubject) changesubject = changesubject and true or nil; if get_changesubject(room) == changesubject then return false; end room._data.changesubject = changesubject; return true; end module:hook("muc-disco#info", function (event) table.insert(event.form, { name = "muc#roomconfig_changesubject"; type = "boolean"; }); event.formdata["muc#roomconfig_changesubject"] = get_changesubject(event.room); end); module:hook("muc-config-form", function(event) table.insert(event.form, { name = "muc#roomconfig_changesubject"; type = "boolean"; label = "Allow anyone to set the room's subject"; desc = "Choose whether anyone, or only moderators, may set the room's subject"; value = get_changesubject(event.room); }); end, 80-1); module:hook("muc-config-submitted/muc#roomconfig_changesubject", function(event) if set_changesubject(event.room, event.value) then event.status_codes["104"] = true; end end); local function get_subject(room) -- a <message/> stanza from the room JID (or from the occupant JID of the entity that set the subject) return room._data.subject_from or room.jid, room._data.subject; end local function send_subject(room, to, time) local msg = create_subject_message(get_subject(room)); msg.attr.to = to; if time then msg:tag("delay", { xmlns = "urn:xmpp:delay", from = room.jid, stamp = dt.datetime(time); }):up(); end room:route_stanza(msg); end local function set_subject(room, from, subject) if subject == "" then subject = nil; end local old_from, old_subject = get_subject(room); if old_subject == subject and old_from == from then return false; end room._data.subject_from = from; room._data.subject = subject; room._data.subject_time = os.time(); local msg = create_subject_message(from, subject); room:broadcast_message(msg); return true; end -- Send subject to joining user module:hook("muc-occupant-session-new", function(event) send_subject(event.room, event.stanza.attr.from, event.room._data.subject_time); end, 20); -- Prosody has made the decision that messages with <subject/> are exclusively subject changes -- e.g. body will be ignored; even if the subject change was not allowed module:hook("muc-occupant-groupchat", function(event) local stanza = event.stanza; local subject = stanza:get_child("subject"); if subject then local room = event.room; local occupant = event.occupant; -- Role check for subject changes local role_rank = valid_roles[occupant and occupant.role or "none"]; if role_rank >= valid_roles.moderator or ( role_rank >= valid_roles.participant and get_changesubject(room) ) then -- and participant set_subject(room, occupant.nick, subject:get_text()); room:save(); return true; else event.origin.send(st.error_reply(stanza, "auth", "forbidden", "You are not allowed to change the subject")); return true; end end end, 20); return { get_changesubject = get_changesubject; set_changesubject = set_changesubject; get = get_subject; set = set_subject; send = send_subject; };