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