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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 s_match = string.match;
local type = type
local string = string
local base64 = require "util.encodings".base64;
local xor = require "bit".bxor
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");
module "scram"
--=========================
--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 a:len() > b:len() 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
for eq in username:gmatch("=(.?.?)") do
if eq ~= "2D" and eq ~= "3D" then
return false
end
end
-- replace =2D with , and =3D with =
username:gsub("=2D", ",");
username:gsub("=3D", "=");
-- apply SASLprep
username = saslprep(username);
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
local client_first_message = message;
self.state["client_first_message"] = client_first_message;
self.state["name"] = client_first_message:match("n=(.+),r=")
self.state["clientnonce"] = client_first_message:match("r=([^,]+)")
if not self.state.name or not self.state.clientnonce then
return "failure", "malformed-request";
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";
end
self.state["servernonce"] = generate_uuid();
self.state["salt"] = generate_uuid();
local server_first_message = "r="..self.state.clientnonce..self.state.servernonce..",s="..base64.encode(self.state.salt)..",i="..default_i;
self.state["server_first_message"] = server_first_message;
return "challenge", server_first_message
else
if type(message) ~= "string" then return "failure", "malformed-request" end
-- we are processing client_final_message
local client_final_message = message;
self.state["proof"] = client_final_message:match("p=(.+)");
self.state["nonce"] = client_final_message:match("r=(.+),p=");
self.state["channelbinding"] = client_final_message:match("c=(.+),r=");
if not self.state.proof or not self.state.nonce or not self.state.channelbinding then
return "failure", "malformed-request";
end
local password;
if self.profile.plain then
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"
end
end
local SaltedPassword = Hi(hmac_sha1, password, self.state.salt, default_i)
local ClientKey = hmac_sha1(SaltedPassword, "Client Key")
local ServerKey = hmac_sha1(SaltedPassword, "Server Key")
local StoredKey = sha1(ClientKey)
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_sha1(StoredKey, AuthMessage)
local ClientProof = binaryXOR(ClientKey, ClientSignature)
local ServerSignature = hmac_sha1(ServerKey, AuthMessage)
if base64.encode(ClientProof) == self.state.proof 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
function init(registerMechanism)
registerMechanism("SCRAM-SHA-1", {"plain"}, scram_sha_1);
end
return _M;
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