util/sasl/scram.lua

-- sasl.lua v0.4
-- Copyright (C) 2008-2009 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 s_match = string.match;

local base64 = require "util.encodings".base64;
local xor = require "bit".bxor
local hmac_sha1 = require "util.hmac".sha1;
local sha1 = require "util.hashes".sha1;

module "plain"

--=========================
--SASL SCRAM-SHA-1 according to draft-ietf-sasl-scram-10
local default_i = 4096

local function bp( b )
	local result = ""
	for i=1, b:len() do
		result = result.."\\"..b:byte(i)
	end
	return result
end

local function binaryXOR( a, b )
	if string.len(a) > string.len(b) then
		b = string.rep("\0", a:len() - b:len())..b
	elseif string.len(a) < string.len(b) then
		a = string.rep("\0", b:len() - a:len())..a
	end
	local result = ""
	for i=1, a:len() do
		result = result..string.char(xor(a:byte(i), b:byte(i)))
	end
	return result
end

-- hash algorithm independent Hi(PBKDF2) implementation
local function Hi(hmac, str, salt, i)
	local Ust = hmac(str, salt.."\0\0\0\1");
	local res = Ust;	
	for n=1,i-1 do
		Und = hmac(str, Ust)
		res = binaryXOR(res, Und)
		Ust = Und
	end
	return res
end

local function validate_username(username)
	-- check for forbidden char sequences
	
	-- replace =2D with , and =3D with =
	
	-- apply SASLprep
	return username;
end

local function scram_sha_1(self, message)
	if not self.state then self["state"] = {} end
	
	if not self.state.name then
		-- we are processing client_first_message
		self.state["name"] = string.match(client_first_message, "n=(.+),r=")
		self.state["clientnonce"] = string.match(client_first_message, "r=([^,]+)")
		
		self.state.name = validate_username(self.state.name);
		if not self.state.name then
			return "failure", "malformed-request";
		end
	else
		-- we are processing client_final_message
	end
end

function init(registerMechanism)
	registerMechanism("SCRAM-SHA-1", {"plain"}, scram_sha_1);
end

return _M;