Add rfc868-time.nse, queries a Time protocol server

scripts/rfc868-time.nse

@@ -0,0 +1,61 @@
+local comm = require "comm"
+local shortport = require "shortport"
+local stdnse = require "stdnse"
+local bin = require "bin"
+local nmap = require "nmap"
+local os = require "os"
+
+description = [[
+Retrieves the day and time from the Time service.
+]]
+
+---
+-- @output
+-- PORT   STATE SERVICE
+-- 37/tcp open  time
+-- |_rfc868-time: 2013-10-23T10:33:00
+
+author = "Daniel Miller"
+
+license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
+
+categories = {"discovery", "safe", "version"}
+
+
+portrule = shortport.port_or_service(37, "time", {"tcp", "udp"})
+
+action = function(host, port)
+  local status, result = comm.exchange(host, port, "", {bytes=4, proto=port.protocol})
+
+  if status then
+    local _, stamp
+    local width = #result
+    if width == 4 then
+      _, stamp = bin.unpack(">I", result)
+      port.version.extrainfo = "32 bits"
+    elseif width == 8 then
+      _, stamp = bin.unpack(">I", result)
+      port.version.extrainfo = "64 bits"
+    else
+      stdnse.print_debug(1, "Odd response: %s", stdnse.filename_escape(response)) 
+      return nil
+    end
+
+    -- RFC 868 epoch is Jan 1, 1900
+    stamp = stamp - 2208988800
+
+    -- Make sure we don't stomp a more-likely service detection.
+    if port.version.name == "time" then
+      local diff = os.difftime(stamp,os.time())
+      if diff < 0 then diff = -diff end
+      -- confidence decreases by 1 for each year the time is off.
+      stdnse.print_debug(1, "Time difference: %d seconds (%0.2f years)", diff, diff / 31556926)
+      local confidence = 10 - diff / 31556926
+      if confidence < 0 then confidence = 0 end
+      port.version.name_confidence = confidence
+      nmap.set_port_version(host, port, "hardmatched")
+    end
+
+    return stdnse.format_timestamp(stamp)
+  end
+end