util/sasl.lua

   1
   2 local md5 = require "md5"
   3 local log = require "util.logger".init("sasl");
   4 local tostring = tostring;
   5 local st = require "util.stanza";
   6 local generate_uuid = require "util.uuid".generate;
   7 local s_match = string.match;
   8 local gmatch = string.gmatch
   9 local string = string
  10 local math = require "math"
  11 local type = type
  12 local error = error
  13 local print = print
  14
  15 module "sasl"
  16
  17 local function new_plain(realm, password_handler)
  18         local object = { mechanism = "PLAIN", realm = realm, password_handler = password_handler}
  19         object.feed =   function(self, message)
  20                                                 --print(message:gsub("%W", function (c) return string.format("\\%d", string.byte(c)) end));
  21
  22                                                 if message == "" or message == nil then return "failure", "malformed-request" end
  23                                                 local response = message
  24                                                 local authorization = s_match(response, "([^&%z]+)")
  25                                                 local authentication = s_match(response, "%z([^&%z]+)%z")
  26                                                 local password = s_match(response, "%z[^&%z]+%z([^&%z]+)")
  27
  28                                                 local password_encoding, correct_password = self.password_handler(authentication, self.realm, "PLAIN")
  29
  30                                                 local claimed_password = ""
  31                                                 if password_encoding == nil then claimed_password = password
  32                                                 else claimed_password = password_encoding(password) end
  33
  34                                                 self.username = authentication
  35                                                 if claimed_password == correct_password then
  36                                                         log("debug", "success")
  37                                                         return "success"
  38                                                 else
  39                                                         log("debug", "failure")
  40                                                         return "failure", "not-authorized"
  41                                                 end
  42                                         end
  43         return object
  44 end
  45
  46 local function new_digest_md5(realm, password_handler)
  47         --TODO maybe support for authzid
  48
  49         local function serialize(message)
  50                 local data = ""
  51
  52                 if type(message) ~= "table" then error("serialize needs an argument of type table.") end
  53
  54                 -- testing all possible values
  55                 if message["nonce"] then data = data..[[nonce="]]..message.nonce..[[",]] end
  56                 if message["qop"] then data = data..[[qop="]]..message.qop..[[",]] end
  57                 if message["charset"] then data = data..[[charset=]]..message.charset.."," end
  58                 if message["algorithm"] then data = data..[[algorithm=]]..message.algorithm.."," end
  59                 if message["realm"] then data = data..[[realm="]]..message.realm..[[",]] end
  60                 if message["rspauth"] then data = data..[[rspauth=]]..message.rspauth.."," end
  61                 data = data:gsub(",$", "")
  62                 return data
  63         end
  64
  65         local function parse(data)
  66                 message = {}
  67                 log("debug", "parse-message: "..data)
  68                 for k, v in gmatch(data, [[([%w%-]+)="?([%w%-%/%.%+=]+)"?,?]]) do
  69                         message[k] = v
  70                 log("debug", "               "..k.." = "..v)
  71                 end
  72                 return message
  73         end
  74
  75         local object = { mechanism = "DIGEST-MD5", realm = realm, password_handler = password_handler}
  76
  77         --TODO: something better than math.random would be nice, maybe OpenSSL's random number generator
  78         object.nonce = generate_uuid()
  79         object.step = 0
  80         object.nonce_count = {}
  81
  82         function object.feed(self, message)
  83                 log("debug", "SASL step: "..self.step)
  84                 self.step = self.step + 1
  85                 if (self.step == 1) then
  86                         local challenge = serialize({   nonce = object.nonce,
  87                                                                                         qop = "auth",
  88                                                                                         charset = "utf-8",
  89                                                                                         algorithm = "md5-sess",
  90                                                                                         realm = self.realm});
  91                         log("debug", "challenge: "..challenge)
  92                         return "challenge", challenge
  93                 elseif (self.step == 2) then
  94                         local response = parse(message)
  95                         -- check for replay attack
  96                         if response["nc"] then
  97                                 if self.nonce_count[response["nc"]] then return "failure", "not-authorized" end
  98                         end
  99
 100                         -- check for username, it's REQUIRED by RFC 2831
 101                         if not response["username"] then
 102                                 return "failure", "malformed-request"
 103                         end
 104                         self["username"] = response["username"]
 105
 106                         -- check for nonce, ...
 107                         if not response["nonce"] then
 108                                 return "failure", "malformed-request"
 109                         else
 110                                 -- check if it's the right nonce
 111                                 if response["nonce"] ~= tostring(self.nonce) then return "failure", "malformed-request" end
 112                         end
 113
 114                         if not response["cnonce"] then return "failure", "malformed-request" end
 115                         if not response["qop"] then response["qop"] = "auth" end
 116
 117                         if response["realm"] == nil then response["realm"] = "" end
 118
 119                         local domain = ""
 120                         local protocol = ""
 121                         if response["digest-uri"] then
 122                                 protocol, domain = response["digest-uri"]:match("(%w+)/(.*)$")
 123                         else
 124                                 return "failure", "malformed-request", "Missing entry for digest-uri in SASL message."
 125                         end
 126
 127                         --TODO maybe realm support
 128                         self.username = response["username"]
 129                         local password_encoding, Y = self.password_handler(response["username"], response["realm"], "DIGEST-MD5")
 130                         local A1 = Y..":"..response["nonce"]..":"..response["cnonce"]--:authzid
 131                         local A2 = "AUTHENTICATE:"..protocol.."/"..domain
 132
 133                         local HA1 = md5.sumhexa(A1)
 134                         local HA2 = md5.sumhexa(A2)
 135
 136                         local KD = HA1..":"..response["nonce"]..":"..response["nc"]..":"..response["cnonce"]..":"..response["qop"]..":"..HA2
 137                         local response_value = md5.sumhexa(KD)
 138
 139                         log("debug", "response_value: "..response_value);
 140                         log("debug", "response:       "..response["response"]);
 141                         if response_value == response["response"] then
 142                                 -- calculate rspauth
 143                                 A2 = ":"..protocol.."/"..domain
 144
 145                                 HA1 = md5.sumhexa(A1)
 146                                 HA2 = md5.sumhexa(A2)
 147
 148                                 KD = HA1..":"..response["nonce"]..":"..response["nc"]..":"..response["cnonce"]..":"..response["qop"]..":"..HA2
 149                                 local rspauth = md5.sumhexa(KD)
 150
 151                                 return "challenge", serialize({rspauth = rspauth})
 152                         else
 153                                 return "failure", "not-authorized", "The response provided by the client doesn't match the one we calculated."
 154                         end
 155                 elseif self.step == 3 then
 156                         return "success"
 157                 end
 158         end
 159         return object
 160 end
 161
 162 function new(mechanism, realm, password_handler)
 163         local object
 164         if mechanism == "PLAIN" then object = new_plain(realm, password_handler)
 165         elseif mechanism == "DIGEST-MD5" then object = new_digest_md5(realm, password_handler)
 166         else
 167                 log("debug", "Unsupported SASL mechanism: "..tostring(mechanism));
 168                 return nil
 169         end
 170         return object
 171 end
 172
 173 return _M;