--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_s2s_auth_posh/mod_s2s_auth_posh.lua	Wed May 21 23:01:47 2014 +0200
@@ -0,0 +1,118 @@
+-- Copyright (C) 2013 - 2014 Tobias Markmann
+-- This file is MIT/X11 licensed.
+--
+-- Implements authentication via POSH (PKIX over Secure HTTP)
+-- http://tools.ietf.org/html/draft-miller-posh-03
+--
+module:set_global();
+--local https = require 'ssl.https'
+--local http = require "socket.http";
+local json = require 'util.json'
+local serialization = require 'util.serialization'
+
+local nameprep = require "util.encodings".stringprep.nameprep;
+local to_unicode = require "util.encodings".idna.to_unicode;
+local cert_verify_identity = require "util.x509".verify_identity;
+local der2pem = require"util.x509".der2pem;
+local base64 = require"util.encodings".base64;
+
+local function posh_lookup(host_session, resume)
+	-- do nothing if posh info already exists
+	if host_session.posh ~= nil then return end
+
+	(host_session.log or module._log)("debug", "DIRECTION: %s", tostring(host_session.direction));
+
+	local target_host = false;
+	if host_session.direction == "incoming" then
+		target_host = host_session.from_host;
+	elseif host_session.direction == "outgoing" then
+		target_host = host_session.to_host;
+	end
+
+	local url = "https://"..target_host.."/.well-known/posh._xmpp-server._tcp.json"
+
+	(host_session.log or module._log)("debug", "Request POSH information for %s", tostring(target_host));
+	local request = http.request(url, nil, function(response, code, req)
+				(host_session.log or module._log)("debug", "Received POSH response");
+				local jwk = json.decode(response);
+				if not jwk then
+					(host_session.log or module._log)("error", "POSH response is not valid JSON!");
+					(host_session.log or module._log)("debug", tostring(response));
+				end
+				host_session.posh = {};
+				host_session.posh.jwk = jwk;
+				resume()
+		end)
+	return true;
+end
+
+function module.add_host(module)
+	local function on_new_s2s(event)
+		local host_session = event.origin;
+		if host_session.type == "s2sout" or host_session.type == "s2sin" or host_session.posh ~= nil then return end -- Already authenticated
+		
+		host_session.log("debug", "Pausing connection until POSH lookup is completed");
+		host_session.conn:pause()
+		local function resume()
+				host_session.log("debug", "POSH lookup completed, resuming connection");
+				host_session.conn:resume()
+			end
+		if not posh_lookup(host_session, resume) then
+			resume();
+		end
+	end
+	
+	-- New outgoing connections
+	module:hook("stanza/http://etherx.jabber.org/streams:features", on_new_s2s, 501);
+	module:hook("s2sout-authenticate-legacy", on_new_s2s, 200);
+	
+	-- New incoming connections
+	module:hook("s2s-stream-features", on_new_s2s, 10);
+
+	module:hook("s2s-authenticated", function(event)
+		local session = event.session;
+		if session.posh and not session.secure then
+			-- Bogus replies should trigger this path
+			-- How does this interact with Dialback?
+			session:close({
+				condition = "policy-violation",
+				text = "Secure server-to-server communication is required but was not "
+					..((session.direction == "outgoing" and "offered") or "used")
+			});
+			return false;
+		end
+		-- Cleanup
+		session.posh = nil;
+	end);
+end
+
+-- Do POSH authentication
+module:hook("s2s-check-certificate", function(event)
+	local session, cert = event.session, event.cert;
+	(session.log or module._log)("info", "Trying POSH authentication.");
+	-- if session.cert_identity_status ~= "valid" and session.posh then
+	if session.posh then
+		local target_host = event.host;
+
+		local jwk = session.posh.jwk;
+ 
+		local connection_certs = session.conn:socket():getpeerchain();
+
+		local x5c_table = jwk.keys[1].x5c;
+
+		local wire_cert = connection_certs[1];
+		local jwk_cert = ssl.x509.load(der2pem(base64.decode(x5c_table[1])));
+
+		if (wire_cert and jwk_cert and
+			wire_cert:digest("sha1") == jwk_cert:digest("sha1")) then
+			session.cert_chain_status = "valid";
+			session.cert_identity_status = "valid";
+			(session.log or module._log)("debug", "POSH authentication succeeded!");
+			return true;
+		else
+			(session.log or module._log)("debug", "POSH authentication failed!");
+			(session.log or module._log)("debug", "(top wire sha1 vs top jwk sha1) = (%s vs %s)", wire_cert:digest("sha1"), jwk_cert:digest("sha1"));
+			return false;
+		end
+	end
+end);