util/sasl.lua

   1
   2 local md5 = require "util.hashes".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 local idna_ascii = require "util.encodings".idna.to_ascii
  15 local idna_unicode = require "util.encodings".idna.to_unicode
  16
  17 module "sasl"
  18
  19 local function new_plain(realm, password_handler)
  20         local object = { mechanism = "PLAIN", realm = realm, password_handler = password_handler}
  21         function object.feed(self, message)
  22
  23                 if message == "" or message == nil then return "failure", "malformed-request" end
  24                 local response = message
  25                 local authorization = s_match(response, "([^&%z]+)")
  26                 local authentication = s_match(response, "%z([^&%z]+)%z")
  27                 local password = s_match(response, "%z[^&%z]+%z([^&%z]+)")
  28
  29                 if authentication == nil or password == nil then return "failure", "malformed-request" end
  30
  31                 local password_encoding, correct_password = self.password_handler(authentication, self.realm, "PLAIN")
  32
  33                 if correct_password == nil then return "failure", "not-authorized"
  34                 elseif correct_password == false then return "failure", "account-disabled" end
  35
  36                 local claimed_password = ""
  37                 if password_encoding == nil then claimed_password = password
  38                 else claimed_password = password_encoding(password) end
  39
  40                 self.username = authentication
  41                 if claimed_password == correct_password then
  42                         return "success"
  43                 else
  44                         return "failure", "not-authorized"
  45                 end
  46         end
  47         return object
  48 end
  49
  50 local function new_digest_md5(realm, password_handler)
  51         --TODO maybe support for authzid
  52
  53         local function serialize(message)
  54                 local data = ""
  55
  56                 if type(message) ~= "table" then error("serialize needs an argument of type table.") end
  57
  58                 -- testing all possible values
  59                 if message["nonce"] then data = data..[[nonce="]]..message.nonce..[[",]] end
  60                 if message["qop"] then data = data..[[qop="]]..message.qop..[[",]] end
  61                 if message["charset"] then data = data..[[charset=]]..message.charset.."," end
  62                 if message["algorithm"] then data = data..[[algorithm=]]..message.algorithm.."," end
  63                 if message["realm"] then data = data..[[realm="]]..message.realm..[[",]] end
  64                 if message["rspauth"] then data = data..[[rspauth=]]..message.rspauth.."," end
  65                 data = data:gsub(",$", "")
  66                 return data
  67         end
  68
  69         local function parse(data)
  70                 message = {}
  71                 for k, v in gmatch(data, [[([%w%-]+)="?([^",]*)"?,?]]) do -- FIXME The hacky regex makes me shudder
  72                         message[k] = v
  73                 end
  74                 return message
  75         end
  76
  77         local object = { mechanism = "DIGEST-MD5", realm = realm, password_handler = password_handler}
  78
  79         --TODO: something better than math.random would be nice, maybe OpenSSL's random number generator
  80         object.nonce = generate_uuid()
  81         object.step = 0
  82         object.nonce_count = {}
  83
  84         function object.feed(self, message)
  85                 self.step = self.step + 1
  86                 if (self.step == 1) then
  87                         local challenge = serialize({   nonce = object.nonce,
  88                                                                                         qop = "auth",
  89                                                                                         charset = "utf-8",
  90                                                                                         algorithm = "md5-sess",
  91                                                                                         realm = idna_ascii(self.realm)});
  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", "Missing entry for cnonce in SASL message." 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                                 if protocol == nil or domain == nil then return "failure", "malformed-request" end
 124                         else
 125                                 return "failure", "malformed-request", "Missing entry for digest-uri in SASL message."
 126                         end
 127
 128                         --TODO maybe realm support
 129                         self.username = response["username"]
 130                         local password_encoding, Y = self.password_handler(response["username"], idna_unicode(response["realm"]), "DIGEST-MD5")
 131                         if Y == nil then return "failure", "not-authorized"
 132                         elseif Y == false then return "failure", "account-disabled" end
 133
 134                         local A1 = Y..":"..response["nonce"]..":"..response["cnonce"]--:authzid
 135                         local A2 = "AUTHENTICATE:"..protocol.."/"..idna_ascii(domain)
 136
 137                         local HA1 = md5(A1, true)
 138                         local HA2 = md5(A2, true)
 139
 140                         local KD = HA1..":"..response["nonce"]..":"..response["nc"]..":"..response["cnonce"]..":"..response["qop"]..":"..HA2
 141                         local response_value = md5(KD, true)
 142
 143                         if response_value == response["response"] then
 144                                 -- calculate rspauth
 145                                 A2 = ":"..protocol.."/"..idna_ascii(domain)
 146
 147                                 HA1 = md5(A1, true)
 148                                 HA2 = md5(A2, true)
 149
 150                                 KD = HA1..":"..response["nonce"]..":"..response["nc"]..":"..response["cnonce"]..":"..response["qop"]..":"..HA2
 151                                 local rspauth = md5(KD, true)
 152                                 self.authenticated = true
 153                                 return "challenge", serialize({rspauth = rspauth})
 154                         else
 155                                 return "failure", "not-authorized", "The response provided by the client doesn't match the one we calculated."
 156                         end
 157                 elseif self.step == 3 then
 158                         if self.authenticated ~= nil then return "success"
 159                         else return "failure", "malformed-request" end
 160                 end
 161         end
 162         return object
 163 end
 164
 165 function new(mechanism, realm, password_handler)
 166         local object
 167         if mechanism == "PLAIN" then object = new_plain(realm, password_handler)
 168         elseif mechanism == "DIGEST-MD5" then object = new_digest_md5(realm, password_handler)
 169         else
 170                 log("debug", "Unsupported SASL mechanism: "..tostring(mechanism));
 171                 return nil
 172         end
 173         return object
 174 end
 175
 176 return _M;