-- sasl.lua v0.4

-- Copyright (C) 2008-2010 Tobias Markmann

--

--    All rights reserved.

--

--    Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

--

--        * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

--        * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

--        * Neither the name of Tobias Markmann nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

--

--    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

local md5 = require "util.hashes".md5;

local log = require "util.logger".init("sasl");

local st = require "util.stanza";

local set = require "util.set";

local array = require "util.array";

local to_unicode = require "util.encodings".idna.to_unicode;

local tostring = tostring;

local pairs, ipairs = pairs, ipairs;

local t_insert, t_concat = table.insert, table.concat;

local s_match = string.match;

local type = type

local error = error

local setmetatable = setmetatable;

local assert = assert;

local require = require;

require "util.iterators"

local keys = keys

local array = require "util.array"

module "sasl"

--[[

Authentication Backend Prototypes:

state = false : disabled

state = true : enabled

state = nil : non-existant

plain:

	function(username, realm)

		return password, state;

	end

plain-test:

	function(username, realm, password)

		return true or false, state;

	end

digest-md5:

	function(username, domain, realm, encoding) -- domain and realm are usually the same; for some broken

												-- implementations it's not

		return digesthash, state;

	end

digest-md5-test:

	function(username, domain, realm, encoding, digesthash)

		return true or false, state;

	end

]]

local method = {};

method.__index = method;

local mechanisms = {};

local backend_mechanism = {};

-- register a new SASL mechanims

local function registerMechanism(name, backends, f)

	assert(type(name) == "string", "Parameter name MUST be a string.");

	assert(type(backends) == "string" or type(backends) == "table", "Parameter backends MUST be either a string or a table.");

	assert(type(f) == "function", "Parameter f MUST be a function.");

	mechanisms[name] = f

	for _, backend_name in ipairs(backends) do

		if backend_mechanism[backend_name] == nil then backend_mechanism[backend_name] = {}; end

		t_insert(backend_mechanism[backend_name], name);

	end

end

-- create a new SASL object which can be used to authenticate clients

function new(realm, profile, forbidden)

	local sasl_i = {profile = profile};

	sasl_i.realm = realm;

	local s = setmetatable(sasl_i, method);

	if forbidden == nil then forbidden = {} end

	s:forbidden(forbidden)

	return s;

end

-- get a fresh clone with the same realm, profiles and forbidden mechanisms

function method:clean_clone()

	return new(self.realm, self.profile, self:forbidden())

end

-- set the forbidden mechanisms

function method:forbidden( restrict )

	if restrict then

		-- set forbidden

		self.restrict = set.new(restrict);

	else

		-- get forbidden

		return array.collect(self.restrict:items());

	end

end

-- get a list of possible SASL mechanims to use

function method:mechanisms()

	local mechanisms = {}

	for backend, f in pairs(self.profile) do

		if backend_mechanism[backend] then

			for _, mechanism in ipairs(backend_mechanism[backend]) do

				if not self.restrict:contains(mechanism) then

					mechanisms[mechanism] = true;

				end

			end

		end

	end

	self["possible_mechanisms"] = mechanisms;

	return array.collect(keys(mechanisms));

end

-- select a mechanism to use

function method:select(mechanism)

	if self.mech_i then

		return false;

	end

	self.mech_i = mechanisms[mechanism]

	if self.mech_i == nil then 

		return false;

	end

	return true;

end

-- feed new messages to process into the library

function method:process(message)

	--if message == "" or message == nil then return "failure", "malformed-request" end

	return self.mech_i(self, message);

end

-- load the mechanisms

local load_mechs = {"plain", "digest-md5", "anonymous", "scram"}

for _, mech in ipairs(load_mechs) do

	local name = "util.sasl."..mech;

	local m = require(name);

	m.init(registerMechanism)

end

return _M;