util/sasl/scram.lua

   1 -- sasl.lua v0.4
   2 -- Copyright (C) 2008-2010 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 hmac_sha1 = require "util.hmac".sha1;
  19 local sha1 = require "util.hashes".sha1;
  20 local generate_uuid = require "util.uuid".generate;
  21 local saslprep = require "util.encodings".stringprep.saslprep;
  22 local log = require "util.logger".init("sasl");
  23 local t_concat = table.concat;
  24 local char = string.char;
  25 local byte = string.byte;
  26
  27 module "scram"
  28
  29 --=========================
  30 --SASL SCRAM-SHA-1 according to RFC 5802
  31
  32 --[[
  33 Supported Authentication Backends
  34
  35 scram_{MECH}:
  36         -- MECH being a standard hash name (like those at IANA's hash registry) with '-' replaced with '_'
  37         function(username, realm)
  38                 return stored_key, server_key, iteration_count, salt, state;
  39         end
  40 ]]
  41
  42 local default_i = 4096
  43
  44 local function bp( b )
  45         local result = ""
  46         for i=1, b:len() do
  47                 result = result.."\\"..b:byte(i)
  48         end
  49         return result
  50 end
  51
  52 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;};
  53
  54 local result = {};
  55 local function binaryXOR( a, b )
  56         for i=1, #a do
  57                 local x, y = byte(a, i), byte(b, i);
  58                 local lowx, lowy = x % 16, y % 16;
  59                 local hix, hiy = (x - lowx) / 16, (y - lowy) / 16;
  60                 local lowr, hir = xor_map[lowx * 16 + lowy + 1], xor_map[hix * 16 + hiy + 1];
  61                 local r = hir * 16 + lowr;
  62                 result[i] = char(r)
  63         end
  64         return t_concat(result);
  65 end
  66
  67 -- hash algorithm independent Hi(PBKDF2) implementation
  68 function Hi(hmac, str, salt, i)
  69         local Ust = hmac(str, salt.."\0\0\0\1");
  70         local res = Ust;
  71         for n=1,i-1 do
  72                 local Und = hmac(str, Ust)
  73                 res = binaryXOR(res, Und)
  74                 Ust = Und
  75         end
  76         return res
  77 end
  78
  79 local function validate_username(username)
  80         -- check for forbidden char sequences
  81         for eq in username:gmatch("=(.?.?)") do
  82                 if eq ~= "2D" and eq ~= "3D" then
  83                         return false
  84                 end
  85         end
  86
  87         -- replace =2D with , and =3D with =
  88         username = username:gsub("=2D", ",");
  89         username = username:gsub("=3D", "=");
  90
  91         -- apply SASLprep
  92         username = saslprep(username);
  93         return username;
  94 end
  95
  96 local function hashprep(hashname)
  97         return hashname:lower():gsub("-", "_");
  98 end
  99
 100 function getAuthenticationDatabaseSHA1(password, salt, iteration_count)
 101         if type(password) ~= "string" or type(salt) ~= "string" or type(iteration_count) ~= "number" then
 102                 return false, "inappropriate argument types"
 103         end
 104         if iteration_count < 4096 then
 105                 log("warn", "Iteration count < 4096 which is the suggested minimum according to RFC 5802.")
 106         end
 107         local salted_password = Hi(hmac_sha1, password, salt, iteration_count);
 108         local stored_key = sha1(hmac_sha1(salted_password, "Client Key"))
 109         local server_key = hmac_sha1(salted_password, "Server Key");
 110         return true, stored_key, server_key
 111 end
 112
 113 local function scram_gen(hash_name, H_f, HMAC_f)
 114         local function scram_hash(self, message)
 115                 if not self.state then self["state"] = {} end
 116
 117                 if type(message) ~= "string" or #message == 0 then return "failure", "malformed-request" end
 118                 if not self.state.name then
 119                         -- we are processing client_first_message
 120                         local client_first_message = message;
 121
 122                         -- TODO: fail if authzid is provided, since we don't support them yet
 123                         self.state["client_first_message"] = client_first_message;
 124                         self.state["gs2_cbind_flag"], self.state["authzid"], self.state["name"], self.state["clientnonce"]
 125                                 = client_first_message:match("^(%a),(.*),n=(.*),r=([^,]*).*");
 126
 127                         -- we don't do any channel binding yet
 128                         if self.state.gs2_cbind_flag ~= "n" and self.state.gs2_cbind_flag ~= "y" then
 129                                 return "failure", "malformed-request";
 130                         end
 131
 132                         if not self.state.name or not self.state.clientnonce then
 133                                 return "failure", "malformed-request", "Channel binding isn't support at this time.";
 134                         end
 135
 136                         self.state.name = validate_username(self.state.name);
 137                         if not self.state.name then
 138                                 log("debug", "Username violates either SASLprep or contains forbidden character sequences.")
 139                                 return "failure", "malformed-request", "Invalid username.";
 140                         end
 141
 142                         self.state["servernonce"] = generate_uuid();
 143
 144                         -- retreive credentials
 145                         if self.profile.plain then
 146                                 local password, state = self.profile.plain(self, self.state.name, self.realm)
 147                                 if state == nil then return "failure", "not-authorized"
 148                                 elseif state == false then return "failure", "account-disabled" end
 149
 150                                 password = saslprep(password);
 151                                 if not password then
 152                                         log("debug", "Password violates SASLprep.");
 153                                         return "failure", "not-authorized", "Invalid password."
 154                                 end
 155
 156                                 self.state.salt = generate_uuid();
 157                                 self.state.iteration_count = default_i;
 158
 159                                 local succ = false;
 160                                 succ, self.state.stored_key, self.state.server_key = getAuthenticationDatabaseSHA1(password, self.state.salt, default_i, self.state.iteration_count);
 161                                 if not succ then
 162                                         log("error", "Generating authentication database failed. Reason: %s", self.state.stored_key);
 163                                         return "failure", "temporary-auth-failure";
 164                                 end
 165                         elseif self.profile["scram_"..hashprep(hash_name)] then
 166                                 local stored_key, server_key, iteration_count, salt, state = self.profile["scram_"..hashprep(hash_name)](self, self.state.name, self.realm);
 167                                 if state == nil then return "failure", "not-authorized"
 168                                 elseif state == false then return "failure", "account-disabled" end
 169
 170                                 self.state.stored_key = stored_key;
 171                                 self.state.server_key = server_key;
 172                                 self.state.iteration_count = iteration_count;
 173                                 self.state.salt = salt
 174                         end
 175
 176                         local server_first_message = "r="..self.state.clientnonce..self.state.servernonce..",s="..base64.encode(self.state.salt)..",i="..self.state.iteration_count;
 177                         self.state["server_first_message"] = server_first_message;
 178                         return "challenge", server_first_message
 179                 else
 180                         -- we are processing client_final_message
 181                         local client_final_message = message;
 182
 183                         self.state["channelbinding"], self.state["nonce"], self.state["proof"] = client_final_message:match("^c=(.*),r=(.*),.*p=(.*)");
 184
 185                         if not self.state.proof or not self.state.nonce or not self.state.channelbinding then
 186                                 return "failure", "malformed-request", "Missing an attribute(p, r or c) in SASL message.";
 187                         end
 188
 189                         if self.state.nonce ~= self.state.clientnonce..self.state.servernonce then
 190                                 return "failure", "malformed-request", "Wrong nonce in client-final-message.";
 191                         end
 192
 193                         local ServerKey = self.state.server_key;
 194                         local StoredKey = self.state.stored_key;
 195
 196                         local AuthMessage = "n=" .. s_match(self.state.client_first_message,"n=(.+)") .. "," .. self.state.server_first_message .. "," .. s_match(client_final_message, "(.+),p=.+")
 197                         local ClientSignature = HMAC_f(StoredKey, AuthMessage)
 198                         local ClientKey = binaryXOR(ClientSignature, base64.decode(self.state.proof))
 199                         local ServerSignature = HMAC_f(ServerKey, AuthMessage)
 200
 201                         if StoredKey == H_f(ClientKey) then
 202                                 local server_final_message = "v="..base64.encode(ServerSignature);
 203                                 self["username"] = self.state.name;
 204                                 return "success", server_final_message;
 205                         else
 206                                 return "failure", "not-authorized", "The response provided by the client doesn't match the one we calculated.";
 207                         end
 208                 end
 209         end
 210         return scram_hash;
 211 end
 212
 213 function init(registerMechanism)
 214         local function registerSCRAMMechanism(hash_name, hash, hmac_hash)
 215                 registerMechanism("SCRAM-"..hash_name, {"plain", "scram_"..(hashprep(hash_name))}, scram_gen(hash_name:lower(), hash, hmac_hash));
 216         end
 217
 218         registerSCRAMMechanism("SHA-1", sha1, hmac_sha1);
 219 end
 220
 221 return _M;