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plugins/mod_legacyauth.lua @ 13801:a5d5fefb8b68 13.0

mod_tls: Enable Prosody's certificate checking for incoming s2s connections (fixes #1916) (thanks Damian, Zash) Various options in Prosody allow control over the behaviour of the certificate verification process For example, some deployments choose to allow falling back to traditional "dialback" authentication (XEP-0220), while others verify via DANE, hard-coded fingerprints, or other custom plugins. Implementing this flexibility requires us to override OpenSSL's default certificate verification, to allow Prosody to verify the certificate itself, apply custom policies and make decisions based on the outcome. To enable our custom logic, we have to suppress OpenSSL's default behaviour of aborting the connection with a TLS alert message. With LuaSec, this can be achieved by using the verifyext "lsec_continue" flag. We also need to use the lsec_ignore_purpose flag, because XMPP s2s uses server certificates as "client" certificates (for mutual TLS verification in outgoing s2s connections). Commit 99d2100d2918 moved these settings out of the defaults and into mod_s2s, because we only really need these changes for s2s, and they should be opt-in, rather than automatically applied to all TLS services we offer. That commit was incomplete, because it only added the flags for incoming direct TLS connections. StartTLS connections are handled by mod_tls, which was not applying the lsec_* flags. It previously worked because they were already in the defaults. This resulted in incoming s2s connections with "invalid" certificates being aborted early by OpenSSL, even if settings such as `s2s_secure_auth = false` or DANE were present in the config. Outgoing s2s connections inherit verify "none" from the defaults, which means OpenSSL will receive the cert but will not terminate the connection when it is deemed invalid. This means we don't need lsec_continue there, and we also don't need lsec_ignore_purpose (because the remote peer is a "server"). Wondering why we can't just use verify "none" for incoming s2s? It's because in that mode, OpenSSL won't request a certificate from the peer for incoming connections. Setting verify "peer" is how you ask OpenSSL to request a certificate from the client, but also what triggers its built-in verification.
author Matthew Wild <mwild1@gmail.com>
date Tue, 01 Apr 2025 17:26:56 +0100
parent 12977:74b9e05af71e
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-- Prosody IM
-- Copyright (C) 2008-2010 Matthew Wild
-- Copyright (C) 2008-2010 Waqas Hussain
--
-- This project is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--



local st = require "prosody.util.stanza";
local t_concat = table.concat;

local secure_auth_only = module:get_option("c2s_require_encryption",
	module:get_option("require_encryption", true))
	or not(module:get_option("allow_unencrypted_plain_auth"));

local sessionmanager = require "prosody.core.sessionmanager";
local usermanager = require "prosody.core.usermanager";
local nodeprep = require "prosody.util.encodings".stringprep.nodeprep;
local resourceprep = require "prosody.util.encodings".stringprep.resourceprep;

module:add_feature("jabber:iq:auth");
module:hook("stream-features", function(event)
	local origin, features = event.origin, event.features;
	if secure_auth_only and not origin.secure then
		-- Sorry, not offering to insecure streams!
		return;
	elseif not origin.username then
		features:tag("auth", {xmlns='http://jabber.org/features/iq-auth'}):up();
	end
end);

module:hook("stanza/iq/jabber:iq:auth:query", function(event)
	local session, stanza = event.origin, event.stanza;

	if session.type ~= "c2s_unauthed" then
		(session.sends2s or session.send)(st.error_reply(stanza, "cancel", "service-unavailable",
			"Legacy authentication is only allowed for unauthenticated client connections."));
		return true;
	end

	if secure_auth_only and not session.secure then
		session.send(st.error_reply(stanza, "modify", "not-acceptable", "Encryption (SSL or TLS) is required to connect to this server"));
		return true;
	end

	local query = stanza.tags[1];
	local username = query:get_child("username");
	local password = query:get_child("password");
	local resource = query:get_child("resource");
	if not (username and password and resource) then
		local reply = st.reply(stanza);
		session.send(reply:query("jabber:iq:auth")
			:tag("username"):up()
			:tag("password"):up()
			:tag("resource"):up());
	else
		username, password, resource = t_concat(username), t_concat(password), t_concat(resource);
		username = nodeprep(username);
		resource = resourceprep(resource)
		if not (username and resource) then
			session.send(st.error_reply(stanza, "modify", "bad-request"));
			return true;
		end
		if usermanager.test_password(username, session.host, password) then
			-- Authentication successful!
			local success, err = sessionmanager.make_authenticated(session, username);
			if success then
				local err_type, err_msg;
				success, err_type, err, err_msg = sessionmanager.bind_resource(session, resource);
				if not success then
					session.send(st.error_reply(stanza, err_type, err, err_msg));
					session.username, session.type = nil, "c2s_unauthed"; -- FIXME should this be placed in sessionmanager?
					return true;
				elseif resource ~= session.resource then -- server changed resource, not supported by legacy auth
					session.send(st.error_reply(stanza, "cancel", "conflict", "The requested resource could not be assigned to this session."));
					session:close(); -- FIXME undo resource bind and auth instead of closing the session?
					return true;
				end
				session.send(st.reply(stanza));
			else
				session.send(st.error_reply(stanza, "auth", "not-authorized", err));
			end
		else
			session.send(st.error_reply(stanza, "auth", "not-authorized"));
		end
	end
	return true;
end);