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

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

 local tostring = tostring;

 local st = require "util.stanza";

 local generate_uuid = require "util.uuid".generate;

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

 local to_byte, to_char = string.byte, string.char;

 local s_match = string.match;

 local gmatch = string.gmatch

 local string = string

 local math = require "math"

 local type = type

 local error = error

 local print = print

 module "sasl"

 local function new_plain(realm, password_handler)

 	local object = { mechanism = "PLAIN", realm = realm, password_handler = password_handler}

 	function object.feed(self, message)

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

 		local response = message

 		local authorization = s_match(response, "([^&%z]+)")

 		local authentication = s_match(response, "%z([^&%z]+)%z")

 		local password = s_match(response, "%z[^&%z]+%z([^&%z]+)")

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

 		local password_encoding, correct_password = self.password_handler(authentication, self.realm, "PLAIN")

 		if correct_password == nil then return "failure", "not-authorized"

 		elseif correct_password == false then return "failure", "account-disabled" end

 		local claimed_password = ""

 		if password_encoding == nil then claimed_password = password

 		else claimed_password = password_encoding(password) end

 		self.username = authentication

 		if claimed_password == correct_password then

 			return "success"

 		else

 			return "failure", "not-authorized"

 		end

 	end

 	return object

 end

 -- implementing RFC 2831

 local function new_digest_md5(realm, password_handler)

 	--TODO complete support for authzid

 	local function serialize(message)

 		local data = ""

 		if type(message) ~= "table" then error("serialize needs an argument of type table.") end

 		-- testing all possible values

 		if message["nonce"] then data = data..[[nonce="]]..message.nonce..[[",]] end

 		if message["qop"] then data = data..[[qop="]]..message.qop..[[",]] end

 		if message["charset"] then data = data..[[charset=]]..message.charset.."," end

 		if message["algorithm"] then data = data..[[algorithm=]]..message.algorithm.."," end

 		if message["realm"] then data = data..[[realm="]]..message.realm..[[",]] end

 		if message["rspauth"] then data = data..[[rspauth=]]..message.rspauth.."," end

 		data = data:gsub(",$", "")

 		return data

 	end

 	local function utf8tolatin1ifpossible(passwd)

 		local i = 1;

 		while i <= #passwd do

 			local passwd_i = to_byte(passwd:sub(i, i));

 			if passwd_i > 0x7F then

 				if passwd_i < 0xC0 or passwd_i > 0xC3 then

 					return passwd;

 				end

 				i = i + 1;

 				passwd_i = to_byte(passwd:sub(i, i));

 				if passwd_i < 0x80 or passwd_i > 0xBF then

 					return passwd;

 				end

 			end

 			i = i + 1;

 		end

 		local p = {};

 		local j = 0;

 		i = 1;

 		while (i <= #passwd) do

 			local passwd_i = to_byte(passwd:sub(i, i));

 			if passwd_i > 0x7F then

 				i = i + 1;

 				local passwd_i_1 = to_byte(passwd:sub(i, i));

 				t_insert(p, to_char(passwd_i%4*64 + passwd_i_1%64)); -- I'm so clever

 			else

 				t_insert(p, to_char(passwd_i));

 			end

 			i = i + 1;

 		end

 		return t_concat(p);

 	end

 	local function latin1toutf8(str)

 		local p = {};

 		for ch in gmatch(str, ".") do

 			ch = to_byte(ch);

 			if (ch < 0x80) then

 				t_insert(p, to_char(ch));

 			elseif (ch < 0xC0) then

 				t_insert(p, to_char(0xC2, ch));

 			else

 				t_insert(p, to_char(0xC3, ch - 64));

 			end

 		end

 		return t_concat(p);

 	end

 	local function parse(data)

 		message = {}

 		for k, v in gmatch(data, [[([%w%-]+)="?([^",]*)"?,?]]) do -- FIXME The hacky regex makes me shudder

 			message[k] = v;

 		end

 		return message;

 	end

 	local object = { mechanism = "DIGEST-MD5", realm = realm, password_handler = password_handler};

 	object.nonce = generate_uuid();

 	object.step = 0;

 	object.nonce_count = {};

 	function object.feed(self, message)

 		self.step = self.step + 1;

 		if (self.step == 1) then

 			local challenge = serialize({	nonce = object.nonce, 

 											qop = "auth",

 											charset = "utf-8",

 											algorithm = "md5-sess",

 											realm = self.realm});

 			return "challenge", challenge;

 		elseif (self.step == 2) then

 			local response = parse(message);

 			-- check for replay attack

 			if response["nc"] then

 				if self.nonce_count[response["nc"]] then return "failure", "not-authorized" end

 			end

 			-- check for username, it's REQUIRED by RFC 2831

 			if not response["username"] then

 				return "failure", "malformed-request";

 			end

 			self["username"] = response["username"];

 			-- check for nonce, ...

 			if not response["nonce"] then

 				return "failure", "malformed-request";

 			else

 				-- check if it's the right nonce

 				if response["nonce"] ~= tostring(self.nonce) then return "failure", "malformed-request" end

 			end

 			if not response["cnonce"] then return "failure", "malformed-request", "Missing entry for cnonce in SASL message." end

 			if not response["qop"] then response["qop"] = "auth" end

 			if response["realm"] == nil or response["realm"] == "" then

 				response["realm"] = self.realm;

 			elseif response["realm"] ~= self.realm then

 				return "failure", "not-authorized", "Incorrect realm value";

 			end

 			local decoder;

 			if response["charset"] == nil then

 				decoder = utf8tolatin1ifpossible;

 			elseif response["charset"] ~= "utf-8" then

 				return "failure", "incorrect-encoding", "The client's response uses "..response["charset"].." for encoding with isn't supported by sasl.lua. Supported encodings are latin or utf-8.";

 			end

 			local domain = "";

 			local protocol = "";

 			if response["digest-uri"] then

 				protocol, domain = response["digest-uri"]:match("(%w+)/(.*)$");

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

 			else

 				return "failure", "malformed-request", "Missing entry for digest-uri in SASL message."

 			end

 			--TODO maybe realm support

 			self.username = response["username"];

 			local password_encoding, Y = self.password_handler(response["username"], response["realm"], "DIGEST-MD5", decoder)

 			if Y == nil then return "failure", "not-authorized"

 			elseif Y == false then return "failure", "account-disabled" end

 			local A1 = "";

 			if response.authzid then

 				if response.authzid == self.username.."@"..self.realm then

 					-- COMPAT

 					log("warn", "Client is violating XMPP RFC. See section 6.1 of RFC 3920.");

 					A1 = Y..":"..response["nonce"]..":"..response["cnonce"]..":"..response.authzid;

 				else

 					A1 = "?";

 				end

 			else

 				A1 = Y..":"..response["nonce"]..":"..response["cnonce"];

 			end

 			local A2 = "AUTHENTICATE:"..protocol.."/"..domain;

 			local HA1 = md5(A1, true);

 			local HA2 = md5(A2, true);

 			local KD = HA1..":"..response["nonce"]..":"..response["nc"]..":"..response["cnonce"]..":"..response["qop"]..":"..HA2;

 			local response_value = md5(KD, true);

 			if response_value == response["response"] then

 				-- calculate rspauth

 				A2 = ":"..protocol.."/"..domain;

 				HA1 = md5(A1, true);

 				HA2 = md5(A2, true);

 				KD = HA1..":"..response["nonce"]..":"..response["nc"]..":"..response["cnonce"]..":"..response["qop"]..":"..HA2

 				local rspauth = md5(KD, true);

 				self.authenticated = true;

 				return "challenge", serialize({rspauth = rspauth});

 			else

 				return "failure", "not-authorized", "The response provided by the client doesn't match the one we calculated."

 			end							

 		elseif self.step == 3 then

 			if self.authenticated ~= nil then return "success"

 			else return "failure", "malformed-request" end

 		end

 	end

 	return object;

 end

 local function new_anonymous(realm, password_handler)

 	local object = { mechanism = "ANONYMOUS", realm = realm, password_handler = password_handler}

 		function object.feed(self, message)

 			return "success"

 		end

 	object["username"] = generate_uuid()

 	return object

 end

 function new(mechanism, realm, password_handler)

 	local object

 	if mechanism == "PLAIN" then object = new_plain(realm, password_handler)

 	elseif mechanism == "DIGEST-MD5" then object = new_digest_md5(realm, password_handler)

 	elseif mechanism == "ANONYMOUS" then object = new_anonymous(realm, password_handler)

 	else

 		log("debug", "Unsupported SASL mechanism: "..tostring(mechanism));

 		return nil

 	end

 	return object

 end

 return _M;