-- XEP-0215 implementation for time-limited turn credentials
-- Copyright (C) 2012-2013 Philipp Hancke
-- This file is MIT/X11 licensed. 

local st = require "util.stanza";
local hmac_sha1 = require "util.hashes".hmac_sha1;
local base64 = require "util.encodings".base64;
local os_time = os.time;
local secret = module:get_option_string("turncredentials_secret");
local host = module:get_option_string("turncredentials_host"); -- use ip addresses here to avoid further dns lookup latency
local port = module:get_option_number("turncredentials_port", 3478);
local ttl = module:get_option_number("turncredentials_ttl", 86400);
if not (secret and host) then
    module:log("error", "turncredentials not configured");
    return;
end

module:hook("iq/host/urn:xmpp:extdisco:1:services", function(event)
    local origin, stanza = event.origin, event.stanza;
    if stanza.attr.type ~= "get" or stanza.tags[1].name ~= "services" or origin.type ~= "c2s" then
        return;
    end
    local now = os_time() + ttl;
    local userpart = tostring(now);
    local nonce = base64.encode(hmac_sha1(secret, tostring(userpart), false));
    origin.send(st.reply(stanza):tag("services", {xmlns = "urn:xmpp:extdisco:1"})
        :tag("service", { type = "stun", host = host, port = port }):up()
        :tag("service", { type = "turn", host = host, port = port, username = userpart, password = nonce, ttl = ttl}):up()
    );
    return true;
end);