Add STAT support to ftp-syst.nse

CHANGELOG

@@ -1,7 +1,7 @@
 # Nmap Changelog ($Id$); -*-text-*-
 
-o [NSE] ftp-syst sends a SYST command to FTP servers to get system version
-  information. [Daniel Miller]
+o [NSE] ftp-syst sends SYST and STAT commands to FTP servers to get system
+  version and connection information. [Daniel Miller]
 
 o [NSE] FTP scripts like ftp-anon and ftp-brute now correctly handle
   TLS-protected FTP services and use STARTTLS when necessary. [Daniel Miller]

scripts/ftp-syst.nse

@@ -5,9 +5,11 @@ local string = require "string"
 local table = require "table"
 
 description = [[
-Sends an FTP SYST command and returns the result.
+Sends FTP SYST and STAT commands and returns the result.
 
-The canonical response of "UNIX Type: L8" is stripped or ignored, since it is meaningless.
+The canonical SYST response of "UNIX Type: L8" is stripped or ignored, since it
+is meaningless. Typical FTP response codes (215 for SYST and 211 for STAT) are
+also hidden.response codes (215 for SYST and 211 for STAT) are also hidden.
 
 References:
 * https://cr.yp.to/ftp/syst.html
@@ -19,10 +21,55 @@ categories = {"default", "discovery", "safe"}
 
 ---
 -- @output
--- |_ftp-syst: UNIX MikroTik 6.39.2
+-- | ftp-syst:
+-- |   SYST: UNIX MikroTik 6.34.3
+-- |   STAT:
+-- |  Enver Curri FTP server (MikroTik 6.34.3) status:
+-- | Logged in as
+-- | TYPE: ASCII; STRUcture: File; transfer MODE: Stream
+-- | No data connection
+-- |_End of status
+--
+-- | ftp-syst:
+-- |   STAT:
+-- | FTP server status:
+-- |      Connected to 192.0.2.13
+-- |      Logged in as ftp
+-- |      TYPE: ASCII
+-- |      No session bandwidth limit
+-- |      Session timeout in seconds is 300
+-- |      Control connection is plain text
+-- |      Data connections will be plain text
+-- |      At session startup, client count was 1
+-- |      vsFTPd 2.0.5 - secure, fast, stable
+-- |_End of status
+--
+-- | ftp-syst:
+-- |   SYST: Version: Linux 2.6.26.8-rt16
+-- |   STAT:
+-- |  HES_CPE FTP server status:
+-- |      ftpd (GNU inetutils) 1.4.1
+-- |      Connected to 72.14.177.105
+-- |      Waiting for user name
+-- |      TYPE: ASCII, FORM: Nonprint; STRUcture: File; transfer MODE: Stream
+-- |      No data connection
+-- |_End of status
+--
+-- @xmloutput
+-- <elem key="SYST">Version: Linux 3.10.73</elem>
+-- <elem key="STAT">
+--  FRITZ!Box7490 FTP server status:
+--  Connected to 72.14.177.105
+--  Waiting for user name
+--  TYPE: ASCII, FORM: Nonprint; STRUcture: File; transfer MODE: Stream
+--  No data connection
+-- End of status</elem>
 
 portrule = shortport.port_or_service({21,990}, {"ftp","ftps"})
 
+local function do_syst(socket, buffer)
+end
+
 action = function(host, port)
   local socket, code, message, buffer = ftp.connect(host, port)
   if not socket then
@@ -34,38 +81,64 @@ action = function(host, port)
     return nil
   end
 
+  -- SYST
   local auth_done = false
-  ::TRY_AGAIN::
-  if not socket:send("SYST\r\n") then
-    return nil
-  end
-  code, message = ftp.read_reply(buffer)
-  if not code then
-    stdnse.debug1("SYST error: %s", message)
-    return nil
-  end
-  if code == 215 then
-    local stripped = message:gsub("^UNIX Type: L8 *", "")
-    if stripped ~= "" then
-      return stripped
+  local syst
+  repeat
+    if not socket:send("SYST\r\n") then
+      return nil
+    end
+    code, message = ftp.read_reply(buffer)
+    if not code then
+      stdnse.debug1("SYST error: %s", message)
+      break
+    end
+    if code == 215 then
+      local stripped = message:gsub("^UNIX Type: L8 *", "")
+      if stripped ~= "" then
+        syst = stripped
+      end
+      break
+    elseif code < 300 then
+      syst = ("%d %s"):format(code, message)
+      break
+    elseif not auth_done and -- we haven't tried logging in yet
+      ( code == 503 -- Command SYST not accepted during Connected
+        or code == 521 -- Not logged in - Secure authentication required
+        or (code % 100) // 10 == 3 -- x3x codes are auth-related
+        ) then
+      -- Try logging in
+      local status, code, message = ftp.auth(socket, buffer, "anonymous", "IEUser@")
+      if status then
+        auth_done = true
+      end
+    end
+  until not auth_done
+
+  -- STAT
+  if not socket:send("STAT\r\n") then
+    if syst then
+      return {SYST=syst}
     else
       return nil
     end
-  elseif code < 300 then
-    return ("%d %s"):format(code, message)
-  elseif not auth_done and -- we haven't tried logging in yet
-    ( code == 503 -- Command SYST not accepted during Connected
-      or code == 521 -- Not logged in - Secure authentication required
-      or (code % 100) // 10 == 3 -- x3x codes are auth-related
-      ) then
-    -- Try logging in
-    local status, code, message = ftp.auth(socket, buffer, "anonymous", "IEUser@")
-    if status then
-      auth_done = true
-      goto TRY_AGAIN
+  end
+
+  local out = stdnse.output_table()
+  out.SYST = syst
+  local code, stat = ftp.read_reply(buffer)
+
+  if code then
+    if code == 211 then
+      out.STAT = "\n" .. stat
+    elseif code < 300 then
+      out.STAT = ("%d\n%s"):format(code, stat)
     end
   end
 
   ftp.close(socket)
 
+  if #out > 0 then
+    return out
+  end
 end