util/sasl/scram.lua

   1 -- sasl.lua v0.4
   2 -- Copyright (C) 2008-2009 Tobias Markmann
   3 --
   4 --    All rights reserved.
   5 --
   6 --    Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
   7 --
   8 --        * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
   9 --        * 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.
  10 --        * 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.
  11 --
  12 --    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.
  13
  14 local s_match = string.match;
  15 local type = type
  16 local string = string
  17 local base64 = require "util.encodings".base64;
  18 local xor = require "bit".bxor
  19 local hmac_sha1 = require "util.hmac".sha1;
  20 local sha1 = require "util.hashes".sha1;
  21 local generate_uuid = require "util.uuid".generate;
  22
  23 module "plain"
  24
  25 --=========================
  26 --SASL SCRAM-SHA-1 according to draft-ietf-sasl-scram-10
  27 local default_i = 4096
  28
  29 local function bp( b )
  30         local result = ""
  31         for i=1, b:len() do
  32                 result = result.."\\"..b:byte(i)
  33         end
  34         return result
  35 end
  36
  37 local function binaryXOR( a, b )
  38         if a:len() > b:len() then
  39                 b = string.rep("\0", a:len() - b:len())..b
  40         elseif string.len(a) < string.len(b) then
  41                 a = string.rep("\0", b:len() - a:len())..a
  42         end
  43         local result = ""
  44         for i=1, a:len() do
  45                 result = result..string.char(xor(a:byte(i), b:byte(i)))
  46         end
  47         return result
  48 end
  49
  50 -- hash algorithm independent Hi(PBKDF2) implementation
  51 local function Hi(hmac, str, salt, i)
  52         local Ust = hmac(str, salt.."\0\0\0\1");
  53         local res = Ust;
  54         for n=1,i-1 do
  55                 Und = hmac(str, Ust)
  56                 res = binaryXOR(res, Und)
  57                 Ust = Und
  58         end
  59         return res
  60 end
  61
  62 local function validate_username(username)
  63         -- check for forbidden char sequences
  64         for eq in username:gmatch("=(.?.?)") do
  65                 if eq ~= "2D" and eq ~= "3D" then
  66                         return false
  67                 end
  68         end
  69
  70         -- replace =2D with , and =3D with =
  71
  72         -- apply SASLprep
  73         return username;
  74 end
  75
  76 local function scram_sha_1(self, message)
  77         if not self.state then self["state"] = {} end
  78
  79         if not self.state.name then
  80                 -- we are processing client_first_message
  81                 local client_first_message = message;
  82                 self.state["client_first_message"] = client_first_message;
  83                 self.state["name"] = client_first_message:match("n=(.+),r=")
  84                 self.state["clientnonce"] = client_first_message:match("r=([^,]+)")
  85
  86                 self.state.name = validate_username(self.state.name);
  87                 if not self.state.name or not self.state.clientnonce then
  88                         return "failure", "malformed-request";
  89                 end
  90                 self.state["servernonce"] = generate_uuid();
  91                 self.state["salt"] = generate_uuid();
  92
  93                 local server_first_message = "r="..self.state.clientnonce..self.state.servernonce..",s="..base64.encode(self.state.salt)..",i="..default_i;
  94                 self.state["server_first_message"] = server_first_message;
  95                 return "challenge", server_first_message
  96         else
  97                 if type(message) ~= "string" then return "failure", "malformed-request" end
  98                 -- we are processing client_final_message
  99                 local client_final_message = message;
 100
 101                 self.state["proof"] = client_final_message:match("p=(.+)");
 102                 self.state["nonce"] = client_final_message:match("r=(.+),p=");
 103                 self.state["channelbinding"] = client_final_message:match("c=(.+),r=");
 104                 if not self.state.proof or not self.state.nonce or not self.state.channelbinding then
 105                         return "failure", "malformed-request";
 106                 end
 107
 108                 local password;
 109                 if self.profile.plain then
 110                         password, state = self.profile.plain(self.state.name, self.realm)
 111                         if state == nil then return "failure", "not-authorized"
 112                         elseif state == false then return "failure", "account-disabled" end
 113                 end
 114
 115                 local SaltedPassword = Hi(hmac_sha1, password, self.state.salt, default_i)
 116                 local ClientKey = hmac_sha1(SaltedPassword, "Client Key")
 117                 local ServerKey = hmac_sha1(SaltedPassword, "Server Key")
 118                 local StoredKey = sha1(ClientKey)
 119                 local AuthMessage = "n=" .. s_match(self.state.client_first_message,"n=(.+)") .. "," .. self.state.server_first_message .. "," .. s_match(client_final_message, "(.+),p=.+")
 120                 local ClientSignature = hmac_sha1(StoredKey, AuthMessage)
 121                 local ClientProof     = binaryXOR(ClientKey, ClientSignature)
 122                 local ServerSignature = hmac_sha1(ServerKey, AuthMessage)
 123
 124                 if base64.encode(ClientProof) == self.state.proof then
 125                         local server_final_message = "v="..base64.encode(ServerSignature);
 126                         self["username"] = self.state.name;
 127                         return "success", server_final_message;
 128                 else
 129                         return "failure", "not-authorized", "The response provided by the client doesn't match the one we calculated.";
 130                 end
 131         end
 132 end
 133
 134 function init(registerMechanism)
 135         registerMechanism("SCRAM-SHA-1", {"plain"}, scram_sha_1);
 136 end
 137
 138 return _M;