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