Discourse Authentication Module for Prosody

mod_auth_discourse.lua

-- Discourse Authentication Module for Prosody
-- https://meta.discourse.org/t/use-discourse-for-sso-in-a-non-web-app/40584/9
--

local new_sasl = require "util.sasl".new;
local http = require "net.http";
local json = require "util.json";

local log = module._log;
local host = module.host;

local discourse_url = module:get_option_string("discourse_url",  ""):gsub("$host", host);
if discourse_url == "" then error("discourse_url required") end

local function discourse(username, password)
	module:log("debug", "fetching token for user %s", username);
	
	local url = discourse_url:gsub("$user", username);
	
	local credentials = {
		{ name = "login", value = username };
		{ name = "password", value = password };
	}

	local function discourse_verify(response, code)
		module:log("debug", "response: %s", response);
	
		if string.match(response, '"username":"(.-)"') == username:gsub("^%l", string.upper) then
			module:log("debug", "login successful for user: %s", username)
		else
			module:log("debug", "login failed for user: %s", username)
		end
	end	

	local function discourse_login(response, code, request)
		
		csrf = string.match(response, '"csrf":"(.-)"');
		cookie = string.match(request.responseheaders["set-cookie"], '(.-);');

		module:log("debug", "csrf: %s", csrf);
		module:log("debug", "cookie: %s", cookie);
		
		if csrf == nil or cookie == nil then
			module:log("debug", "no csrf or cookie fetched for user %s. abort login", username);
		else
			module:log("debug", "trying to login with fetched csrf and cookie for user %s", username);

			local ex = {
				headers = {
					["Origin"] = url,
					["X-CSRF-Token"] = csrf,
					["Cookie"] = cookie,
					["Content-Type"] = "application/x-www-form-urlencoded; charset=UTF-8",
					["Referer"] = url,
					["X-Requested-With"] = "XMLHttpRequest"
				};
				body = http.formencode(credentials);
			}

			http.request (url .. "session", ex, discourse_verify)
		end
	end

	local ex = {
		headers = {
			["X-CSRF-Token"] = "undefined",
			["Referer"] = url,
			["X-Requested-With"] = "XMLHttpRequest"
		};
	}

	http.request(url .. "session/csrf", ex, discourse_login);
end

local provider = {};

function provider.test_password(username, password)
	return nil, "Not supported"
end

function provider.get_password(username)
	return nil, "Not supported"
end

function provider.set_password(username, password)
	return nil, "Not supported"
end

function provider.user_exists(username)
	return true;
end

function provider.create_user(username, password)
	return nil, "Not supported"
end

function provider.delete_user(username)
	return nil, "Not supported"
end

function provider.get_sasl_handler()
        return new_sasl(host, {
			plain_test = function(sasl, username, password, realm)
				return discourse(username, password), true;
			end
        });
end

module:provides("auth", provider);