-- 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 pairs, ipairs = pairs, ipairs;

local t_insert = table.insert;

local type = type

local setmetatable = setmetatable;

local assert = assert;

local require = require;

local _ENV = nil;

--[[

Authentication Backend Prototypes:

state = false : disabled

state = true : enabled

state = nil : non-existant

Channel Binding:

To enable support of channel binding in some mechanisms you need to provide appropriate callbacks in a table

at profile.cb.

Example:

	profile.cb["tls-unique"] = function(self)

		return self.user

	end

]]

local method = {};

method.__index = method;

local mechanisms = {};

local backend_mechanism = {};

local mechanism_channelbindings = {};

-- register a new SASL mechanims

local function registerMechanism(name, backends, f, cb_backends)

	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.");

	if cb_backends then assert(type(cb_backends) == "table"); end

	mechanisms[name] = f

	if cb_backends then

		mechanism_channelbindings[name] = {};

		for _, cb_name in ipairs(cb_backends) do

			mechanism_channelbindings[name][cb_name] = true;

		end

	end

	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

local function new(realm, profile)

	local mechanisms = profile.mechanisms;

	if not mechanisms then

		mechanisms = {};

		for backend, f in pairs(profile) do

			if backend_mechanism[backend] then

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

					mechanisms[mechanism] = true;

				end

			end

		end

		profile.mechanisms = mechanisms;

	end

	return setmetatable({ profile = profile, realm = realm, mechs = mechanisms }, method);

end

-- add a channel binding handler

function method:add_cb_handler(name, f)

	if type(self.profile.cb) ~= "table" then

		self.profile.cb = {};

	end

	self.profile.cb[name] = f;

	return self;

end

-- get a fresh clone with the same realm and profile

function method:clean_clone()

	return new(self.realm, self.profile)

end

-- get a list of possible SASL mechanims to use

function method:mechanisms()

	local current_mechs = {};

	for mech, _ in pairs(self.mechs) do

		if mechanism_channelbindings[mech] then

			if self.profile.cb then

				local ok = false;

				for cb_name, _ in pairs(self.profile.cb) do

					if mechanism_channelbindings[mech][cb_name] then

						ok = true;

					end

				end

				if ok == true then current_mechs[mech] = true; end

			end

		else

			current_mechs[mech] = true;

		end

	end

	return current_mechs;

end

-- select a mechanism to use

function method:select(mechanism)

	if not self.selected and self.mechs[mechanism] then

		self.selected = mechanism;

		return true;

	end

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 mechanisms[self.selected](self, message);

end

-- load the mechanisms

require "util.sasl.plain"     .init(registerMechanism);

require "util.sasl.digest-md5".init(registerMechanism);

require "util.sasl.anonymous" .init(registerMechanism);

require "util.sasl.scram"     .init(registerMechanism);

require "util.sasl.external"  .init(registerMechanism);

return {

	registerMechanism = registerMechanism;

	new = new;

};