-- 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 "util.stanza";

local sm_bind_resource = require "core.sessionmanager".bind_resource;

local sm_make_authenticated = require "core.sessionmanager".make_authenticated;

local base64 = require "util.encodings".base64;

local cert_verify_identity = require "util.x509".verify_identity;

local usermanager_get_sasl_handler = require "core.usermanager".get_sasl_handler;

local tostring = tostring;

local secure_auth_only = module:get_option("c2s_require_encryption") or module:get_option("require_encryption");

local allow_unencrypted_plain_auth = module:get_option("allow_unencrypted_plain_auth")

local log = module._log;

local xmlns_sasl ='urn:ietf:params:xml:ns:xmpp-sasl';

local xmlns_bind ='urn:ietf:params:xml:ns:xmpp-bind';

local function build_reply(status, ret, err_msg)

	local reply = st.stanza(status, {xmlns = xmlns_sasl});

	if status == "challenge" then

		--log("debug", "CHALLENGE: %s", ret or "");

		reply:text(base64.encode(ret or ""));

	elseif status == "failure" then

		reply:tag(ret):up();

		if err_msg then reply:tag("text"):text(err_msg); end

	elseif status == "success" then

		--log("debug", "SUCCESS: %s", ret or "");

		reply:text(base64.encode(ret or ""));

	else

		module:log("error", "Unknown sasl status: %s", status);

	end

	return reply;

end

local function handle_status(session, status, ret, err_msg)

	if status == "failure" then

		module:fire_event("authentication-failure", { session = session, condition = ret, text = err_msg });

		session.sasl_handler = session.sasl_handler:clean_clone();

	elseif status == "success" then

		local ok, err = sm_make_authenticated(session, session.sasl_handler.username);

		if ok then

			module:fire_event("authentication-success", { session = session });

			session.sasl_handler = nil;

			session:reset_stream();

		else

			module:log("warn", "SASL succeeded but username was invalid");

			module:fire_event("authentication-failure", { session = session, condition = "not-authorized", text = err });

			session.sasl_handler = session.sasl_handler:clean_clone();

			return "failure", "not-authorized", "User authenticated successfully, but username was invalid";

		end

	end

	return status, ret, err_msg;

end

local function sasl_process_cdata(session, stanza)

	local text = stanza[1];

	if text then

		text = base64.decode(text);

		--log("debug", "AUTH: %s", text:gsub("[%z\001-\008\011\012\014-\031]", " "));

		if not text then

			session.sasl_handler = nil;

			session.send(build_reply("failure", "incorrect-encoding"));

			return true;

		end

	end

	local status, ret, err_msg = session.sasl_handler:process(text);

	status, ret, err_msg = handle_status(session, status, ret, err_msg);

	local s = build_reply(status, ret, err_msg);

	log("debug", "sasl reply: %s", tostring(s));

	session.send(s);

	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();

	session:open_stream();

	module:fire_event("s2s-authenticated", { session = session, host = 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"))

	local domain = text ~= "" and text or session.from_host;

	module:log("info", "Accepting SASL EXTERNAL identity from %s", domain);

	module:fire_event("s2s-authenticated", { session = session, host = domain });

	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

		session.sasl_handler = nil; -- allow starting a new SASL negotiation before completing an old one

	end

	if not session.sasl_handler then

		session.sasl_handler = usermanager_get_sasl_handler(module.host, session);

	end

	local mechanism = stanza.attr.mechanism;

	if not session.secure and (secure_auth_only or (mechanism == "PLAIN" and not allow_unencrypted_plain_auth)) then

		session.send(build_reply("failure", "encryption-required"));

		return true;

	end

	local valid_mechanism = session.sasl_handler:select(mechanism);

	if not valid_mechanism then

		session.send(build_reply("failure", "invalid-mechanism"));

		return true;

	end

	return sasl_process_cdata(session, stanza);

end);

module:hook("stanza/urn:ietf:params:xml:ns:xmpp-sasl:response", function(event)

	local session = event.origin;

	if not(session.sasl_handler and session.sasl_handler.selected) then

		session.send(build_reply("failure", "not-authorized", "Out of order SASL element"));

		return true;

	end

	return sasl_process_cdata(session, event.stanza);

end);

module:hook("stanza/urn:ietf:params:xml:ns:xmpp-sasl:abort", function(event)

	local session = event.origin;

	session.sasl_handler = nil;

	session.send(build_reply("failure", "aborted"));

	return true;

end);

local mechanisms_attr = { xmlns='urn:ietf:params:xml:ns:xmpp-sasl' };

local bind_attr = { xmlns='urn:ietf:params:xml:ns:xmpp-bind' };

local xmpp_session_attr = { xmlns='urn:ietf:params:xml:ns:xmpp-session' };

module:hook("stream-features", function(event)

	local origin, features = event.origin, event.features;

	if not origin.username then

		if secure_auth_only and not origin.secure then

			return;

		end

		origin.sasl_handler = usermanager_get_sasl_handler(module.host, origin);

		local mechanisms = st.stanza("mechanisms", mechanisms_attr);

		for mechanism in pairs(origin.sasl_handler:mechanisms()) do

			if mechanism ~= "PLAIN" or origin.secure or allow_unencrypted_plain_auth then

				mechanisms:tag("mechanism"):text(mechanism):up();

			end

		end

		if mechanisms[1] then features:add_child(mechanisms); end

	else

		features:tag("bind", bind_attr):tag("required"):up():up();

		features:tag("session", xmpp_session_attr):tag("optional"):up():up();

	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;

	if stanza.attr.type == "set" then

		local bind = stanza.tags[1];

		resource = bind:child_with_name("resource");

		resource = resource and #resource.tags == 0 and resource[1] or nil;

	end

	local success, err_type, err, err_msg = sm_bind_resource(origin, resource);

	if success then

		origin.send(st.reply(stanza)

			:tag("bind", { xmlns = xmlns_bind })

			:tag("jid"):text(origin.full_jid));

		origin.log("debug", "Resource bound: %s", origin.full_jid);

	else

		origin.send(st.error_reply(stanza, err_type, err, err_msg));

		origin.log("debug", "Resource bind failed: %s", err_msg or err);

	end

	return true;

end);

local function handle_legacy_session(event)

	event.origin.send(st.reply(event.stanza));

	return true;

end

module:hook("iq/self/urn:ietf:params:xml:ns:xmpp-session:session", handle_legacy_session);

module:hook("iq/host/urn:ietf:params:xml:ns:xmpp-session:session", handle_legacy_session);