-- XEP-0257: Client Certificates Management implementation for Prosody

-- Copyright (C) 2012 Thijs Alkemade

--

-- This file is MIT/X11 licensed.

local st = require "util.stanza";

local jid_bare = require "util.jid".bare;

local jid_split = require "util.jid".split;

local xmlns_saslcert = "urn:xmpp:saslcert:1";

local dm_load = require "util.datamanager".load;

local dm_store = require "util.datamanager".store;

local dm_table = "client_certs";

local x509 = require "ssl.x509";

local id_on_xmppAddr = "1.3.6.1.5.5.7.8.5";

local id_ce_subjectAltName = "2.5.29.17";

local digest_algo = "sha1";

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

local function get_id_on_xmpp_addrs(cert)

	local id_on_xmppAddrs = {};

	for k,ext in pairs(cert:extensions()) do

		if k == id_ce_subjectAltName then

			for e,extv in pairs(ext) do

				if e == id_on_xmppAddr then

					for i,v in ipairs(extv) do

						id_on_xmppAddrs[#id_on_xmppAddrs+1] = v;

					end

				end

			end

		end

	end

	module:log("debug", "Found JIDs: (%d) %s", #id_on_xmppAddrs, table.concat(id_on_xmppAddrs, ", "));

	return id_on_xmppAddrs;

end

local function enable_cert(username, cert, info)

	-- Check the certificate. Is it not expired? Does it include id-on-xmppAddr?

	--[[ the method expired doesn't exist in luasec .. yet?

	if cert:expired() then

	module:log("debug", "This certificate is already expired.");

	return nil, "This certificate is expired.";

	end

	--]]

	if not cert:validat(os.time()) then

		module:log("debug", "This certificate is not valid at this moment.");

	end

	local valid_id_on_xmppAddrs;

	local require_id_on_xmppAddr = true;

	if require_id_on_xmppAddr then

		valid_id_on_xmppAddrs = get_id_on_xmpp_addrs(cert);

		local found = false;

		for i,k in pairs(valid_id_on_xmppAddrs) do

			if jid_bare(k) == (username .. "@" .. module.host) then

				found = true;

				break;

			end

		end

		if not found then

			return nil, "This certificate has no valid id-on-xmppAddr field.";

		end

	end

	local certs = dm_load(username, module.host, dm_table) or {};

	info.pem = cert:pem();

	local digest = cert:digest(digest_algo);

	info.digest = digest;

	certs[info.name] = info;

	dm_store(username, module.host, dm_table, certs);

	return true

end

local function disable_cert(username, name, disconnect)

	local certs = dm_load(username, module.host, dm_table) or {};

	local info = certs[name];

	if not info then

		return nil, "item-not-found"

	end

	certs[name] = nil;

	if disconnect then

		module:log("debug", "%s revoked a certificate! Disconnecting all clients that used it", username);

		local sessions = hosts[module.host].sessions[username].sessions;

		local disabled_cert_pem = info.pem;

		for _, session in pairs(sessions) do

			if session and session.conn then

				local cert = session.conn:socket():getpeercertificate();

				if cert and cert:pem() == disabled_cert_pem then

					module:log("debug", "Found a session that should be closed: %s", tostring(session));

					session:close{ condition = "not-authorized", text = "This client side certificate has been revoked."};

				end

			end

		end

	end

	dm_store(username, module.host, dm_table, certs);

	return info;

end

module:hook("iq/self/"..xmlns_saslcert..":items", function(event)

	local origin, stanza = event.origin, event.stanza;

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

		module:log("debug", "%s requested items", origin.full_jid);

		local reply = st.reply(stanza):tag("items", { xmlns = xmlns_saslcert });

		local certs = dm_load(origin.username, module.host, dm_table) or {};

		for digest,info in pairs(certs) do

			reply:tag("item")

				:tag("name"):text(info.name):up()

				:tag("x509cert"):text(info.x509cert)

			:up();

		end

		origin.send(reply);

		return true

	end

end);

module:hook("iq/self/"..xmlns_saslcert..":append", function(event)

	local origin, stanza = event.origin, event.stanza;

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

		local append = stanza:get_child("append", xmlns_saslcert);

		local name = append:get_child_text("name", xmlns_saslcert);

		local x509cert = append:get_child_text("x509cert", xmlns_saslcert);

		if not x509cert or not name then

			origin.send(st.error_reply(stanza, "cancel", "bad-request", "Missing fields.")); -- cancel? not modify?

			return true

		end

		local can_manage = append:get_child("no-cert-management", xmlns_saslcert) ~= nil;

		x509cert = x509cert:gsub("^%s*(.-)%s*$", "%1");

		local cert = x509.load(

		"-----BEGIN CERTIFICATE-----\n"

		.. x509cert ..

		"\n-----END CERTIFICATE-----\n");

		if not cert then

			origin.send(st.error_reply(stanza, "modify", "not-acceptable", "Could not parse X.509 certificate"));

			return true;

		end

		local ok, err = enable_cert(origin.username, cert, {

			name = name,

			x509cert = x509cert,

			no_cert_management = can_manage,

		});

		if not ok then

			origin.send(st.error_reply(stanza, "cancel", "bad-request", err));

			return true -- REJECT?!

		end

		module:log("debug", "%s added certificate named %s", origin.full_jid, name);

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

		return true

	end

end);

local function handle_disable(event)

	local origin, stanza = event.origin, event.stanza;

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

		local disable = stanza.tags[1];

		module:log("debug", "%s disabled a certificate", origin.full_jid);

		local name = disable:get_child_text("name");

		if not name then

			origin.send(st.error_reply(stanza, "cancel", "bad-request", "No key specified."));

			return true

		end

		disable_cert(origin.username, name, disable.name == "revoke");

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

		return true

	end

end

module:hook("iq/self/"..xmlns_saslcert..":disable", handle_disable);

module:hook("iq/self/"..xmlns_saslcert..":revoke", handle_disable);

-- Ad-hoc command

local adhoc_new = module:require "adhoc".new;

local dataforms_new = require "util.dataforms".new;

local function generate_error_message(errors)

	local errmsg = {};

	for name, err in pairs(errors) do

		errmsg[#errmsg + 1] = name .. ": " .. err;

	end

	return table.concat(errmsg, "\n");

end

local choose_subcmd_layout = dataforms_new {

	title = "Certificate management";

	instructions = "What action do you want to perform?";

	{ name = "FORM_TYPE", type = "hidden", value = "http://prosody.im/protocol/certs#subcmd" };

	{ name = "subcmd", type = "list-single", label = "Actions", required = true,

		value = { {label = "Add certificate", value = "add"},

			  {label = "List certificates", value = "list"},

			  {label = "Disable certificate", value = "disable"},

			  {label = "Revoke certificate", value = "revoke"},

		};

	};

};

local add_layout = dataforms_new {

	title = "Adding a certificate";

	instructions = "Enter the certificate in PEM format";

	{ name = "FORM_TYPE", type = "hidden", value = "http://prosody.im/protocol/certs#add" };

	{ name = "name", type = "text-single", label = "Name", required = true };

	{ name = "cert", type = "text-multi", label = "PEM certificate", required = true };

	{ name = "manage", type = "boolean", label = "Can manage certificates", value = true };

};

local disable_layout_stub = dataforms_new { { name = "cert", type = "list-single", label = "Certificate", required = true } };

local function adhoc_handler(self, data, state)

	if data.action == "cancel" then return { status = "canceled" }; end

	if not state or data.action == "prev" then

		return { status = "executing", form = choose_subcmd_layout, actions = { "next" } }, {};

	end

	if not state.subcmd then

		local fields, errors = choose_subcmd_layout:data(data.form);

		if errors then

			return { status = "completed", error = { message = generate_error_message(errors) } };

		end

		local subcmd = fields.subcmd

		if subcmd == "add" then

			return { status = "executing", form = add_layout, actions = { "prev", "next", "complete" } }, { subcmd = "add" };

		elseif subcmd == "list" then

			local list_layout = dataforms_new {

				title = "List of certificates";

			};

			local certs = dm_load(jid_split(data.from), module.host, dm_table) or {};

			for digest, info in pairs(certs) do

				list_layout[#list_layout + 1] = { name = info.name, type = "text-multi", label = info.name, value = info.x509cert };

			end

			return { status = "completed", result = list_layout };

		else

			local layout = dataforms_new {

				{ name = "FORM_TYPE", type = "hidden", value = "http://prosody.im/protocol/certs#" .. subcmd };

				{ name = "cert", type = "list-single", label = "Certificate", required = true };

			};

			if subcmd == "disable" then

				layout.title = "Disabling a certificate";

				layout.instructions = "Select the certificate to disable";

			elseif subcmd == "revoke" then

				layout.title = "Revoking a certificate";

				layout.instructions = "Select the certificate to revoke";

			end

			local certs = dm_load(jid_split(data.from), module.host, dm_table) or {};

			local values = {};

			for digest, info in pairs(certs) do

				values[#values + 1] = { label = info.name, value = info.name };

			end

			return { status = "executing", form = { layout = layout, values = { cert = values } }, actions = { "prev", "next", "complete" } },

				{ subcmd = subcmd };

		end

	end

	if state.subcmd == "add" then

		local fields, errors = add_layout:data(data.form);

		if errors then

			return { status = "completed", error = { message = generate_error_message(errors) } };

		end

		local name = fields.name;

		local x509cert = fields.cert:gsub("^%s*(.-)%s*$", "%1");

		local cert = x509.load(

		"-----BEGIN CERTIFICATE-----\n"

		.. x509cert ..

		"\n-----END CERTIFICATE-----\n");

		if not cert then

			return { status = "completed", error = { message = "Could not parse X.509 certificate" } };

		end

		local ok, err = enable_cert(jid_split(data.from), cert, {

			name = name,

			x509cert = x509cert,

			no_cert_management = not fields.manage

		});

		if not ok then

			return { status = "completed", error = { message = err } };

		end

		module:log("debug", "%s added certificate named %s", data.from, name);

		return { status = "completed", info = "Successfully added certificate " .. name .. "." };

	else

		local fields, errors = disable_layout_stub:data(data.form);

		if errors then

			return { status = "completed", error = { message = generate_error_message(errors) } };

		end

		local info = disable_cert(jid_split(data.from), fields.cert, state.subcmd == "revoke" );

		if state.subcmd == "revoke" then

			return { status = "completed", info = "Revoked certificate " .. info.name .. "."  };

		else

			return { status = "completed", info = "Disabled certificate " .. info.name .. "."  };

		end

	end

end

local cmd_desc = adhoc_new("Manage certificates", "http://prosody.im/protocol/certs", adhoc_handler, "user");

module:provides("adhoc", cmd_desc);

-- Here comes the SASL EXTERNAL stuff

local now = os.time;

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

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

	if session.secure and session.type == "c2s_unauthed" then

		local cert = session.conn:socket():getpeercertificate();

		if not cert then

			module:log("error", "No Client Certificate");

			return

		end

		module:log("info", "Client Certificate: %s", cert:digest(digest_algo));

		if not cert:validat(now()) then

			module:log("debug", "Client has an expired certificate", cert:digest(digest_algo));

			return

		end

		module:log("debug", "Stream features:\n%s", tostring(features));

		local mechs = features:get_child("mechanisms", "urn:ietf:params:xml:ns:xmpp-sasl");

		if mechs then

			mechs:tag("mechanism"):text("EXTERNAL");

		end

	end

end, -1);