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-- 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 s_match = string.match;
local type = type
local string = string
local base64 = require "util.encodings".base64;
local hmac_sha1 = require "util.hmac".sha1;
local sha1 = require "util.hashes".sha1;
local generate_uuid = require "util.uuid".generate;
local saslprep = require "util.encodings".stringprep.saslprep;
local log = require "util.logger".init("sasl");
local t_concat = table.concat;
local char = string.char;
local byte = string.byte;
module "scram"
--=========================
--SASL SCRAM-SHA-1 according to RFC 5802
--[[
Supported Authentication Backends
scram_{MECH}:
-- MECH being a standard hash name (like those at IANA's hash registry) with '-' replaced with '_'
function(username, realm)
return stored_key, server_key, iteration_count, salt, state;
end
]]
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 xor_map = {0;1;2;3;4;5;6;7;8;9;10;11;12;13;14;15;1;0;3;2;5;4;7;6;9;8;11;10;13;12;15;14;2;3;0;1;6;7;4;5;10;11;8;9;14;15;12;13;3;2;1;0;7;6;5;4;11;10;9;8;15;14;13;12;4;5;6;7;0;1;2;3;12;13;14;15;8;9;10;11;5;4;7;6;1;0;3;2;13;12;15;14;9;8;11;10;6;7;4;5;2;3;0;1;14;15;12;13;10;11;8;9;7;6;5;4;3;2;1;0;15;14;13;12;11;10;9;8;8;9;10;11;12;13;14;15;0;1;2;3;4;5;6;7;9;8;11;10;13;12;15;14;1;0;3;2;5;4;7;6;10;11;8;9;14;15;12;13;2;3;0;1;6;7;4;5;11;10;9;8;15;14;13;12;3;2;1;0;7;6;5;4;12;13;14;15;8;9;10;11;4;5;6;7;0;1;2;3;13;12;15;14;9;8;11;10;5;4;7;6;1;0;3;2;14;15;12;13;10;11;8;9;6;7;4;5;2;3;0;1;15;14;13;12;11;10;9;8;7;6;5;4;3;2;1;0;};
local result = {};
local function binaryXOR( a, b )
for i=1, #a do
local x, y = byte(a, i), byte(b, i);
local lowx, lowy = x % 16, y % 16;
local hix, hiy = (x - lowx) / 16, (y - lowy) / 16;
local lowr, hir = xor_map[lowx * 16 + lowy + 1], xor_map[hix * 16 + hiy + 1];
local r = hir * 16 + lowr;
result[i] = char(r)
end
return t_concat(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
local Und = hmac(str, Ust)
res = binaryXOR(res, Und)
Ust = Und
end
return res
end
local function validate_username(username)
-- check for forbidden char sequences
for eq in username:gmatch("=(.?.?)") do
if eq ~= "2D" and eq ~= "3D" then
return false
end
end
-- replace =2D with , and =3D with =
username = username:gsub("=2D", ",");
username = username:gsub("=3D", "=");
-- apply SASLprep
username = saslprep(username);
return username;
end
local function hashprep(hashname)
return hashname:lower():gsub("-", "_");
end
function getAuthenticationDatabaseSHA1(password, salt, iteration_count)
if type(password) ~= "string" or type(salt) ~= "string" or type(iteration_count) ~= "number" then
return false, "inappropriate argument types"
end
if iteration_count < 4096 then
log("warn", "Iteration count < 4096 which is the suggested minimum according to RFC 5802.")
end
local salted_password = Hi(hmac_sha1, password, salt, iteration_count);
local stored_key = sha1(hmac_sha1(salted_password, "Client Key"))
local server_key = hmac_sha1(salted_password, "Server Key");
return true, stored_key, server_key
end
local function scram_gen(hash_name, H_f, HMAC_f)
local function scram_hash(self, message)
if not self.state then self["state"] = {} end
if type(message) ~= "string" or #message == 0 then return "failure", "malformed-request" end
if not self.state.name then
-- we are processing client_first_message
local client_first_message = message;
-- TODO: fail if authzid is provided, since we don't support them yet
self.state["client_first_message"] = client_first_message;
self.state["gs2_cbind_flag"], self.state["authzid"], self.state["name"], self.state["clientnonce"]
= client_first_message:match("^(%a),(.*),n=(.*),r=([^,]*).*");
-- we don't do any channel binding yet
if self.state.gs2_cbind_flag ~= "n" and self.state.gs2_cbind_flag ~= "y" then
return "failure", "malformed-request";
end
if not self.state.name or not self.state.clientnonce then
return "failure", "malformed-request", "Channel binding isn't support at this time.";
end
self.state.name = validate_username(self.state.name);
if not self.state.name then
log("debug", "Username violates either SASLprep or contains forbidden character sequences.")
return "failure", "malformed-request", "Invalid username.";
end
self.state["servernonce"] = generate_uuid();
-- retreive credentials
if self.profile.plain then
local password, state = self.profile.plain(self.state.name, self.realm)
if state == nil then return "failure", "not-authorized"
elseif state == false then return "failure", "account-disabled" end
password = saslprep(password);
if not password then
log("debug", "Password violates SASLprep.");
return "failure", "not-authorized", "Invalid password."
end
self.state.salt = generate_uuid();
self.state.iteration_count = default_i;
local succ = false;
succ, self.state.stored_key, self.state.server_key = getAuthenticationDatabaseSHA1(password, self.state.salt, default_i, self.state.iteration_count);
if not succ then
log("error", "Generating authentication database failed. Reason: %s", self.state.stored_key);
return "failure", "temporary-auth-failure";
end
elseif self.profile["scram_"..hashprep(hash_name)] then
local stored_key, server_key, iteration_count, salt, state = self.profile["scram_"..hashprep(hash_name)](self.state.name, self.realm);
if state == nil then return "failure", "not-authorized"
elseif state == false then return "failure", "account-disabled" end
self.state.stored_key = stored_key;
self.state.server_key = server_key;
self.state.iteration_count = iteration_count;
self.state.salt = salt
end
local server_first_message = "r="..self.state.clientnonce..self.state.servernonce..",s="..base64.encode(self.state.salt)..",i="..self.state.iteration_count;
self.state["server_first_message"] = server_first_message;
return "challenge", server_first_message
else
-- we are processing client_final_message
local client_final_message = message;
self.state["channelbinding"], self.state["nonce"], self.state["proof"] = client_final_message:match("^c=(.*),r=(.*),.*p=(.*)");
if not self.state.proof or not self.state.nonce or not self.state.channelbinding then
return "failure", "malformed-request", "Missing an attribute(p, r or c) in SASL message.";
end
if self.state.nonce ~= self.state.clientnonce..self.state.servernonce then
return "failure", "malformed-request", "Wrong nonce in client-final-message.";
end
local ServerKey = self.state.server_key;
local StoredKey = self.state.stored_key;
local AuthMessage = "n=" .. s_match(self.state.client_first_message,"n=(.+)") .. "," .. self.state.server_first_message .. "," .. s_match(client_final_message, "(.+),p=.+")
local ClientSignature = HMAC_f(StoredKey, AuthMessage)
local ClientKey = binaryXOR(ClientSignature, base64.decode(self.state.proof))
local ServerSignature = HMAC_f(ServerKey, AuthMessage)
if StoredKey == H_f(ClientKey) then
local server_final_message = "v="..base64.encode(ServerSignature);
self["username"] = self.state.name;
return "success", server_final_message;
else
return "failure", "not-authorized", "The response provided by the client doesn't match the one we calculated.";
end
end
end
return scram_hash;
end
function init(registerMechanism)
local function registerSCRAMMechanism(hash_name, hash, hmac_hash)
registerMechanism("SCRAM-"..hash_name, {"plain", "scram_"..(hashprep(hash_name))}, scram_gen(hash_name:lower(), hash, hmac_hash));
end
registerSCRAMMechanism("SHA-1", sha1, hmac_sha1);
end
return _M;
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