Software / code / prosody
File
plugins/muc/hats.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 | 11245:43b43e7156b8 |
| child | 12977:74b9e05af71e |
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local st = require "util.stanza"; local muc_util = module:require "muc/util"; local xmlns_hats = "xmpp:prosody.im/protocol/hats:1"; -- Strip any hats claimed by the client (to prevent spoofing) muc_util.add_filtered_namespace(xmlns_hats); module:hook("muc-build-occupant-presence", function (event) local bare_jid = event.occupant and event.occupant.bare_jid or event.bare_jid; local aff_data = event.room:get_affiliation_data(bare_jid); local hats = aff_data and aff_data.hats; if not hats then return; end local hats_el; for hat_id, hat_data in pairs(hats) do if hat_data.active then if not hats_el then hats_el = st.stanza("hats", { xmlns = xmlns_hats }); end hats_el:tag("hat", { uri = hat_id, title = hat_data.title }):up(); end end if not hats_el then return; end event.stanza:add_direct_child(hats_el); end);