prosody
337391d34b70

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Changeset

3651:337391d34b70

s2s: SASL EXTERNAL
author Paul Aurich <paul@darkrain42.org>
date Sun, 21 Nov 2010 21:10:43 -0800
parents 3650:2b80450bd7ae
children 3652:8ae10787272a
files core/s2smanager.lua plugins/mod_dialback.lua plugins/mod_saslauth.lua util/certverification.lua
diffstat 4 files changed, 391 insertions(+), 4 deletions(-) [+]
line wrap: on
line diff
--- a/core/s2smanager.lua	Sun Nov 21 21:02:31 2010 -0800
+++ b/core/s2smanager.lua	Sun Nov 21 21:10:43 2010 -0800
@@ -27,6 +27,7 @@
 local st = require "stanza";
 local stanza = st.stanza;
 local nameprep = require "util.encodings".stringprep.nameprep;
+local cert_verify_identity = require "util.certverification".verify_identity;
 
 local fire_event = prosody.events.fire_event;
 local uuid_gen = require "util.uuid".generate;
@@ -373,16 +374,44 @@
 		from=from, to=to, version='1.0', ["xml:lang"]='en'}):top_tag());
 end
 
+local function check_cert_status(session)
+	local conn = session.conn:socket()
+	local cert = conn:getpeercertificate()
+
+	if cert then
+		local chain_valid, err = conn:getpeerchainvalid()
+		if not chain_valid then
+			session.cert_chain_status = "invalid";
+			(session.log or log)("debug", "certificate chain validation result: %s", err);
+		else
+			session.cert_chain_status = "valid";
+
+			local host = session.direction == "incoming" and session.from_host or session.to_host
+
+			-- We'll go ahead and verify the asserted identity if the
+			-- connecting server specified one.
+			if host then
+				if cert_verify_identity(host, "xmpp-server", cert) then
+					session.cert_identity_status = "valid"
+				else
+					session.cert_identity_status = "invalid"
+				end
+			end
+		end
+	end
+end
+
 function streamopened(session, attr)
 	local send = session.sends2s;
 	
 	-- TODO: #29: SASL/TLS on s2s streams
 	session.version = tonumber(attr.version) or 0;
 	
+	-- TODO: Rename session.secure to session.encrypted
 	if session.secure == false then
 		session.secure = true;
 	end
-	
+
 	if session.direction == "incoming" then
 		-- Send a reply stream header
 		session.to_host = attr.to and nameprep(attr.to);
@@ -407,6 +436,9 @@
 				return;
 			end
 		end
+
+		if session.secure and not session.cert_chain_status then check_cert_status(session); end
+
 		send("<?xml version='1.0'?>");
 		send(stanza("stream:stream", { xmlns='jabber:server', ["xmlns:db"]='jabber:server:dialback',
 				["xmlns:stream"]='http://etherx.jabber.org/streams', id=session.streamid, from=session.to_host, to=session.from_host, version=(session.version > 0 and "1.0" or nil) }):top_tag());
@@ -426,7 +458,9 @@
 		-- If we are just using the connection for verifying dialback keys, we won't try and auth it
 		if not attr.id then error("stream response did not give us a streamid!!!"); end
 		session.streamid = attr.id;
-	
+
+		if session.secure and not session.cert_chain_status then check_cert_status(session); end
+
 		-- Send unauthed buffer
 		-- (stanzas which are fine to send before dialback)
 		-- Note that this is *not* the stanza queue (which
--- a/plugins/mod_dialback.lua	Sun Nov 21 21:02:31 2010 -0800
+++ b/plugins/mod_dialback.lua	Sun Nov 21 21:10:43 2010 -0800
@@ -132,9 +132,19 @@
 	end
 end);
 
+module:hook_stanza("urn:ietf:params:xml:ns:xmpp-sasl", "failure", function (origin, stanza)
+	if origin.external_auth == "failed" then
+		module:log("debug", "SASL EXTERNAL failed, falling back to dialback");
+		s2s_initiate_dialback(origin);
+		return true;
+	end
+end, 100);
+
 module:hook_stanza(xmlns_stream, "features", function (origin, stanza)
-	s2s_initiate_dialback(origin);
-	return true;
+	if not origin.external_auth or origin.external_auth == "failed" then
+		s2s_initiate_dialback(origin);
+		return true;
+	end
 end, 100);
 
 -- Offer dialback to incoming hosts
--- a/plugins/mod_saslauth.lua	Sun Nov 21 21:02:31 2010 -0800
+++ b/plugins/mod_saslauth.lua	Sun Nov 21 21:10:43 2010 -0800
@@ -11,8 +11,11 @@
 local st = require "util.stanza";
 local sm_bind_resource = require "core.sessionmanager".bind_resource;
 local sm_make_authenticated = require "core.sessionmanager".make_authenticated;
+local s2s_make_authenticated = require "core.s2smanager".make_authenticated;
 local base64 = require "util.encodings".base64;
 
+local cert_verify_identity = require "util.certverification".verify_identity;
+
 local nodeprep = require "util.encodings".stringprep.nodeprep;
 local usermanager_get_sasl_handler = require "core.usermanager".get_sasl_handler;
 local t_concat, t_insert = table.concat, table.insert;
@@ -91,8 +94,123 @@
 	return true;
 end
 
+module:hook_stanza(xmlns_sasl, "success", function (session, stanza)
+	if session.type ~= "s2sout_unauthed" or session.external_auth ~= "attempting" then return; end
+	module:log("debug", "SASL EXTERNAL with %s succeeded", session.to_host);
+	session.external_auth = "succeeded"
+	session:reset_stream();
+
+	local default_stream_attr = {xmlns = "jabber:server", ["xmlns:stream"] = "http://etherx.jabber.org/streams",
+	                            ["xmlns:db"] = 'jabber:server:dialback', version = "1.0", to = session.to_host, from = session.from_host};
+	session.sends2s("<?xml version='1.0'?>");
+	session.sends2s(st.stanza("stream:stream", default_stream_attr):top_tag());
+
+	s2s_make_authenticated(session, session.to_host);
+	return true;
+end)
+
+module:hook_stanza(xmlns_sasl, "failure", function (session, stanza)
+	if session.type ~= "s2sout_unauthed" or session.external_auth ~= "attempting" then return; end
+
+	module:log("info", "SASL EXTERNAL with %s failed", session.to_host)
+	-- TODO: Log the failure reason
+	session.external_auth = "failed"
+end, 500)
+
+module:hook_stanza(xmlns_sasl, "failure", function (session, stanza)
+	-- TODO: Dialback wasn't loaded.  Do something useful.
+end, 90)
+
+module:hook_stanza("http://etherx.jabber.org/streams", "features", function (session, stanza)
+	if session.type ~= "s2sout_unauthed" or not session.secure then return; end
+
+	local mechanisms = stanza:get_child("mechanisms", xmlns_sasl)
+	if mechanisms then
+		for mech in mechanisms:childtags() do
+			if mech[1] == "EXTERNAL" then
+				module:log("debug", "Initiating SASL EXTERNAL with %s", session.to_host);
+				local reply = st.stanza("auth", {xmlns = xmlns_sasl, mechanism = "EXTERNAL"});
+				reply:text(base64.encode(session.from_host))
+				session.sends2s(reply)
+				session.external_auth = "attempting"
+				return true
+			end
+		end
+	end
+end, 150);
+
+local function s2s_external_auth(session, stanza)
+	local mechanism = stanza.attr.mechanism;
+
+	if not session.secure then
+		if mechanism == "EXTERNAL" then
+			session.sends2s(build_reply("failure", "encryption-required"))
+		else
+			session.sends2s(build_reply("failure", "invalid-mechanism"))
+		end
+		return true;
+	end
+
+	if mechanism ~= "EXTERNAL" or session.cert_chain_status ~= "valid" then
+		session.sends2s(build_reply("failure", "invalid-mechanism"))
+		return true;
+	end
+
+	local text = stanza[1]
+	if not text then
+		session.sends2s(build_reply("failure", "malformed-request"))
+		return true
+	end
+
+	-- Either the value is "=" and we've already verified the external
+	-- cert identity, or the value is a string and either matches the
+	-- from_host (
+
+	text = base64.decode(text)
+	if not text then
+		session.sends2s(build_reply("failure", "incorrect-encoding"))
+		return true;
+	end
+
+	if session.cert_identity_status == "valid" then
+		if text ~= "" and text ~= session.from_host then
+			session.sends2s(build_reply("failure", "invalid-authzid"))
+			return true
+		end
+	else
+		if text == "" then
+			session.sends2s(build_reply("failure", "invalid-authzid"))
+			return true
+		end
+
+		local cert = session.conn:socket():getpeercertificate()
+		if (cert_verify_identity(text, "xmpp-server", cert)) then
+			session.cert_identity_status = "valid"
+		else
+			session.cert_identity_status = "invalid"
+			session.sends2s(build_reply("failure", "invalid-authzid"))
+			return true
+		end
+	end
+
+	session.external_auth = "succeeded"
+
+	if not session.from_host then
+		session.from_host = text;
+	end
+	session.sends2s(build_reply("success"))
+	module:log("info", "Accepting SASL EXTERNAL identity from %s", text or session.from_host);
+	s2s_make_authenticated(session, text or session.from_host)
+	session:reset_stream();
+	return true
+end
+
 module:hook("stanza/urn:ietf:params:xml:ns:xmpp-sasl:auth", function(event)
 	local session, stanza = event.origin, event.stanza;
+	if session.type == "s2sin_unauthed" then
+		return s2s_external_auth(session, stanza)
+	end
+
 	if session.type ~= "c2s_unauthed" then return; end
 
 	if session.sasl_handler and session.sasl_handler.selected then
@@ -168,6 +286,20 @@
 	end
 end);
 
+module:hook("s2s-stream-features", function(event)
+	local origin, features = event.origin, event.features;
+	if origin.secure and origin.type == "s2sin_unauthed" then
+		-- Offer EXTERNAL if chain is valid and either we didn't validate
+		-- the identity or it passed.
+		if origin.cert_chain_status == "valid" and origin.cert_identity_status ~= "invalid" then --TODO: Configurable
+			module:log("debug", "Offering SASL EXTERNAL")
+			features:tag("mechanisms", { xmlns = xmlns_sasl })
+				:tag("mechanism"):text("EXTERNAL")
+			:up():up();
+		end
+	end
+end);
+
 module:hook("iq/self/urn:ietf:params:xml:ns:xmpp-bind:bind", function(event)
 	local origin, stanza = event.origin, event.stanza;
 	local resource;
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/util/certverification.lua	Sun Nov 21 21:10:43 2010 -0800
@@ -0,0 +1,211 @@
+-- Prosody IM
+-- Copyright (C) 2010 Matthew Wild
+-- Copyright (C) 2010 Paul Aurich
+--
+-- This project is MIT/X11 licensed. Please see the
+-- COPYING file in the source package for more information.
+--
+
+-- TODO: I feel a fair amount of this logic should be integrated into Luasec,
+-- so that everyone isn't re-inventing the wheel.  Dependencies on
+-- IDN libraries complicate that.
+
+
+-- [TLS-CERTS] - http://tools.ietf.org/html/draft-saintandre-tls-server-id-check-10
+-- [XMPP-CORE] - http://tools.ietf.org/html/draft-ietf-xmpp-3920bis-18
+-- [SRV-ID]    - http://tools.ietf.org/html/rfc4985
+-- [IDNA]      - http://tools.ietf.org/html/rfc5890
+-- [LDAP]      - http://tools.ietf.org/html/rfc4519
+-- [PKIX]      - http://tools.ietf.org/html/rfc5280
+
+local nameprep = require "util.encodings".stringprep.nameprep;
+local idna_to_ascii = require "util.encodings".idna.to_ascii;
+local log = require "util.logger".init("certverification");
+
+module "certverification"
+
+local oid_commonname = "2.5.4.3"; -- [LDAP] 2.3
+local oid_subjectaltname = "2.5.29.17"; -- [PKIX] 4.2.1.6
+local oid_xmppaddr = "1.3.6.1.5.5.7.8.5"; -- [XMPP-CORE]
+local oid_dnssrv   = "1.3.6.1.5.5.7.8.7"; -- [SRV-ID]
+
+-- Compare a hostname (possibly international) with asserted names
+-- extracted from a certificate.
+-- This function follows the rules laid out in
+-- sections 4.4.1 and 4.4.2 of [TLS-CERTS]
+--
+-- A wildcard ("*") all by itself is allowed only as the left-most label
+local function compare_dnsname(host, asserted_names)
+	-- TODO: Sufficient normalization?  Review relevant specs.
+	local norm_host = idna_to_ascii(host)
+	if norm_host == nil then
+		log("info", "Host %s failed IDNA ToASCII operation", host)
+		return false
+	end
+
+	norm_host = norm_host:lower()
+
+	local host_chopped = norm_host:gsub("^[^.]+%.", "") -- everything after the first label
+
+	for i=1,#asserted_names do
+		local name = asserted_names[i]
+		if norm_host == name:lower() then
+			log("debug", "Cert dNSName %s matched hostname", name);
+			return true
+		end
+
+		-- Allow the left most label to be a "*"
+		if name:match("^%*%.") then
+			local rest_name = name:gsub("^[^.]+%.", "")
+			if host_chopped == rest_name:lower() then
+				log("debug", "Cert dNSName %s matched hostname", name);
+				return true
+			end
+		end
+	end
+
+	return false
+end
+
+-- Compare an XMPP domain name with the asserted id-on-xmppAddr
+-- identities extracted from a certificate.  Both are UTF8 strings.
+--
+-- Per [XMPP-CORE], matches against asserted identities don't include
+-- wildcards, so we just do a normalize on both and then a string comparison
+--
+-- TODO: Support for full JIDs?
+local function compare_xmppaddr(host, asserted_names)
+	local norm_host = nameprep(host)
+
+	for i=1,#asserted_names do
+		local name = asserted_names[i]
+
+		-- We only want to match against bare domains right now, not
+		-- those crazy full-er JIDs.
+		if name:match("[@/]") then
+			log("debug", "Ignoring xmppAddr %s because it's not a bare domain", name)
+		else
+			local norm_name = nameprep(name)
+			if norm_name == nil then
+				log("info", "Ignoring xmppAddr %s, failed nameprep!", name)
+			else
+				if norm_host == norm_name then
+					log("debug", "Cert xmppAddr %s matched hostname", name)
+					return true
+				end
+			end
+		end
+	end
+
+	return false
+end
+
+-- Compare a host + service against the asserted id-on-dnsSRV (SRV-ID)
+-- identities extracted from a certificate.
+--
+-- Per [SRV-ID], the asserted identities will be encoded in ASCII via ToASCII.
+-- Comparison is done case-insensitively, and a wildcard ("*") all by itself
+-- is allowed only as the left-most non-service label.
+local function compare_srvname(host, service, asserted_names)
+	local norm_host = idna_to_ascii(host)
+	if norm_host == nil then
+		log("info", "Host %s failed IDNA ToASCII operation", host);
+		return false
+	end
+
+	-- Service names start with a "_"
+	if service:match("^_") == nil then service = "_"..service end
+
+	norm_host = norm_host:lower();
+	local host_chopped = norm_host:gsub("^[^.]+%.", "") -- everything after the first label
+
+	for i=1,#asserted_names do
+		local asserted_service, name = asserted_names[i]:match("^(_[^.]+)%.(.*)");
+		if service == asserted_service then
+			if norm_host == name:lower() then
+				log("debug", "Cert SRVName %s matched hostname", name);
+				return true;
+			end
+
+			-- Allow the left most label to be a "*"
+			if name:match("^%*%.") then
+				local rest_name = name:gsub("^[^.]+%.", "")
+				if host_chopped == rest_name:lower() then
+					log("debug", "Cert SRVName %s matched hostname", name)
+					return true
+				end
+			end
+			if norm_host == name:lower() then
+				log("debug", "Cert SRVName %s matched hostname", name);
+				return true
+			end
+		end
+	end
+
+	return false
+end
+
+function verify_identity(host, service, cert)
+	local ext = cert:extensions()
+	if ext[oid_subjectaltname] then
+		local sans = ext[oid_subjectaltname];
+
+		-- Per [TLS-CERTS] 4.3, 4.4.4, "a client MUST NOT seek a match for a
+		-- reference identifier if the presented identifiers include a DNS-ID
+		-- SRV-ID, URI-ID, or any application-specific identifier types"
+		local had_supported_altnames = false
+
+		if sans[oid_xmppaddr] then
+			had_supported_altnames = true
+			if compare_xmppaddr(host, sans[oid_xmppaddr]) then return true end
+		end
+
+		if sans[oid_dnssrv] then
+			had_supported_altnames = true
+			-- Only check srvNames if the caller specified a service
+			if service and compare_srvname(host, service, sans[oid_dnssrv]) then return true end
+		end
+
+		if sans["dNSName"] then
+			had_supported_altnames = true
+			if compare_dnsname(host, sans["dNSName"]) then return true end
+		end
+
+		-- We don't need URIs, but [TLS-CERTS] is clear.
+		if sans["uniformResourceIdentifier"] then
+			had_supported_altnames = true
+		end
+
+		if had_supported_altnames then return false end
+	end
+
+	-- Extract a common name from the certificate, and check it as if it were
+	-- a dNSName subjectAltName (wildcards may apply for, and receive,
+	-- cat treats)
+	--
+	-- Per [TLS-CERTS] 1.5, a CN-ID is the Common Name from a cert subject
+	-- which has one and only one Common Name
+	local subject = cert:subject()
+	local cn = nil
+	for i=1,#subject do
+		local dn = subject[i]
+		if dn["oid"] == oid_commonname then
+			if cn then
+				log("info", "Certificate has multiple common names")
+				return false
+			end
+
+			cn = dn["value"];
+		end
+	end
+
+	if cn then
+		-- Per [TLS-CERTS] 4.4.4, follow the comparison rules for dNSName SANs.
+		return compare_dnsname(host, { cn })
+	end
+
+	-- If all else fails, well, why should we be any different?
+	return false
+end
+
+return _M;