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.hashes".hmac_sha1;
  19 local sha1 = require "util.hashes".sha1;
  20 local Hi = require "util.hashes".scram_Hi_sha1;
  21 local generate_uuid = require "util.uuid".generate;
  22 local saslprep = require "util.encodings".stringprep.saslprep;
  23 local nodeprep = require "util.encodings".stringprep.nodeprep;
  24 local log = require "util.logger".init("sasl");
  25 local t_concat = table.concat;
  26 local char = string.char;
  27 local byte = string.byte;
  28
  29 module "sasl.scram"
  30
  31 --=========================
  32 --SASL SCRAM-SHA-1 according to RFC 5802
  33
  34 --[[
  35 Supported Authentication Backends
  36
  37 scram_{MECH}:
  38         -- MECH being a standard hash name (like those at IANA's hash registry) with '-' replaced with '_'
  39         function(username, realm)
  40                 return stored_key, server_key, iteration_count, salt, state;
  41         end
  42 ]]
  43
  44 local default_i = 4096
  45
  46 local function bp( b )
  47         local result = ""
  48         for i=1, b:len() do
  49                 result = result.."\\"..b:byte(i)
  50         end
  51         return result
  52 end
  53
  54 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;};
  55
  56 local result = {};
  57 local function binaryXOR( a, b )
  58         for i=1, #a do
  59                 local x, y = byte(a, i), byte(b, i);
  60                 local lowx, lowy = x % 16, y % 16;
  61                 local hix, hiy = (x - lowx) / 16, (y - lowy) / 16;
  62                 local lowr, hir = xor_map[lowx * 16 + lowy + 1], xor_map[hix * 16 + hiy + 1];
  63                 local r = hir * 16 + lowr;
  64                 result[i] = char(r)
  65         end
  66         return t_concat(result);
  67 end
  68
  69 local function validate_username(username, _nodeprep)
  70         -- check for forbidden char sequences
  71         for eq in username:gmatch("=(.?.?)") do
  72                 if eq ~= "2C" and eq ~= "3D" then
  73                         return false
  74                 end
  75         end
  76
  77         -- replace =2C with , and =3D with =
  78         username = username:gsub("=2C", ",");
  79         username = username:gsub("=3D", "=");
  80
  81         -- apply SASLprep
  82         username = saslprep(username);
  83
  84         if username and _nodeprep ~= false then
  85                 username = (_nodeprep or nodeprep)(username);
  86         end
  87
  88         return username and #username>0 and username;
  89 end
  90
  91 local function hashprep(hashname)
  92         return hashname:lower():gsub("-", "_");
  93 end
  94
  95 function getAuthenticationDatabaseSHA1(password, salt, iteration_count)
  96         if type(password) ~= "string" or type(salt) ~= "string" or type(iteration_count) ~= "number" then
  97                 return false, "inappropriate argument types"
  98         end
  99         if iteration_count < 4096 then
 100                 log("warn", "Iteration count < 4096 which is the suggested minimum according to RFC 5802.")
 101         end
 102         local salted_password = Hi(password, salt, iteration_count);
 103         local stored_key = sha1(hmac_sha1(salted_password, "Client Key"))
 104         local server_key = hmac_sha1(salted_password, "Server Key");
 105         return true, stored_key, server_key
 106 end
 107
 108 local function scram_gen(hash_name, H_f, HMAC_f)
 109         local function scram_hash(self, message)
 110                 if not self.state then self["state"] = {} end
 111
 112                 if type(message) ~= "string" or #message == 0 then return "failure", "malformed-request" end
 113                 if not self.state.name then
 114                         -- we are processing client_first_message
 115                         local client_first_message = message;
 116
 117                         -- TODO: fail if authzid is provided, since we don't support them yet
 118                         self.state["client_first_message"] = client_first_message;
 119                         self.state["gs2_cbind_flag"], self.state["authzid"], self.state["name"], self.state["clientnonce"]
 120                                 = client_first_message:match("^(%a),(.*),n=(.*),r=([^,]*).*");
 121
 122                         -- we don't do any channel binding yet
 123                         if self.state.gs2_cbind_flag ~= "n" and self.state.gs2_cbind_flag ~= "y" then
 124                                 return "failure", "malformed-request";
 125                         end
 126
 127                         if not self.state.name or not self.state.clientnonce then
 128                                 return "failure", "malformed-request", "Channel binding isn't support at this time.";
 129                         end
 130
 131                         self.state.name = validate_username(self.state.name, self.profile.nodeprep);
 132                         if not self.state.name then
 133                                 log("debug", "Username violates either SASLprep or contains forbidden character sequences.")
 134                                 return "failure", "malformed-request", "Invalid username.";
 135                         end
 136
 137                         self.state["servernonce"] = generate_uuid();
 138
 139                         -- retreive credentials
 140                         if self.profile.plain then
 141                                 local password, state = self.profile.plain(self, self.state.name, self.realm)
 142                                 if state == nil then return "failure", "not-authorized"
 143                                 elseif state == false then return "failure", "account-disabled" end
 144
 145                                 password = saslprep(password);
 146                                 if not password then
 147                                         log("debug", "Password violates SASLprep.");
 148                                         return "failure", "not-authorized", "Invalid password."
 149                                 end
 150
 151                                 self.state.salt = generate_uuid();
 152                                 self.state.iteration_count = default_i;
 153
 154                                 local succ = false;
 155                                 succ, self.state.stored_key, self.state.server_key = getAuthenticationDatabaseSHA1(password, self.state.salt, default_i, self.state.iteration_count);
 156                                 if not succ then
 157                                         log("error", "Generating authentication database failed. Reason: %s", self.state.stored_key);
 158                                         return "failure", "temporary-auth-failure";
 159                                 end
 160                         elseif self.profile["scram_"..hashprep(hash_name)] then
 161                                 local stored_key, server_key, iteration_count, salt, state = self.profile["scram_"..hashprep(hash_name)](self, self.state.name, self.realm);
 162                                 if state == nil then return "failure", "not-authorized"
 163                                 elseif state == false then return "failure", "account-disabled" end
 164
 165                                 self.state.stored_key = stored_key;
 166                                 self.state.server_key = server_key;
 167                                 self.state.iteration_count = iteration_count;
 168                                 self.state.salt = salt
 169                         end
 170
 171                         local server_first_message = "r="..self.state.clientnonce..self.state.servernonce..",s="..base64.encode(self.state.salt)..",i="..self.state.iteration_count;
 172                         self.state["server_first_message"] = server_first_message;
 173                         return "challenge", server_first_message
 174                 else
 175                         -- we are processing client_final_message
 176                         local client_final_message = message;
 177
 178                         self.state["channelbinding"], self.state["nonce"], self.state["proof"] = client_final_message:match("^c=(.*),r=(.*),.*p=(.*)");
 179
 180                         if not self.state.proof or not self.state.nonce or not self.state.channelbinding then
 181                                 return "failure", "malformed-request", "Missing an attribute(p, r or c) in SASL message.";
 182                         end
 183
 184                         if self.state.nonce ~= self.state.clientnonce..self.state.servernonce then
 185                                 return "failure", "malformed-request", "Wrong nonce in client-final-message.";
 186                         end
 187
 188                         local ServerKey = self.state.server_key;
 189                         local StoredKey = self.state.stored_key;
 190
 191                         local AuthMessage = "n=" .. s_match(self.state.client_first_message,"n=(.+)") .. "," .. self.state.server_first_message .. "," .. s_match(client_final_message, "(.+),p=.+")
 192                         local ClientSignature = HMAC_f(StoredKey, AuthMessage)
 193                         local ClientKey = binaryXOR(ClientSignature, base64.decode(self.state.proof))
 194                         local ServerSignature = HMAC_f(ServerKey, AuthMessage)
 195
 196                         if StoredKey == H_f(ClientKey) then
 197                                 local server_final_message = "v="..base64.encode(ServerSignature);
 198                                 self["username"] = self.state.name;
 199                                 return "success", server_final_message;
 200                         else
 201                                 return "failure", "not-authorized", "The response provided by the client doesn't match the one we calculated.";
 202                         end
 203                 end
 204         end
 205         return scram_hash;
 206 end
 207
 208 function init(registerMechanism)
 209         local function registerSCRAMMechanism(hash_name, hash, hmac_hash)
 210                 registerMechanism("SCRAM-"..hash_name, {"plain", "scram_"..(hashprep(hash_name))}, scram_gen(hash_name:lower(), hash, hmac_hash));
 211         end
 212
 213         registerSCRAMMechanism("SHA-1", sha1, hmac_sha1);
 214 end
 215
 216 return _M;