Fuzzer

Fuzzers usually used for general or precisely applications functions. In this part we'll show how to fuzz most known services using ruby. Remember, Fuzzing is an Art of Hitting Things, it's not about the tools.
Fuzzer Types
Mutation
Metadata/File format
Mutation
FTP Fuzzer
The general idea of fuzzing FTP service is to test all commands buffer sizes. However, not the case isn't the same all the time, for example, testing username and password buffers. In addition, the same technique could be applied for many services even customized services.
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#!/bin/ruby
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# KING SABRI | @KINGSABRI
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# Simple FTP COMMNDS Fuzzer
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#
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require 'socket'
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​
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class String
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  def red; colorize(self, "\e[31m"); end
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  def green; colorize(self, "\e[32m"); end
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  def colorize(text, color_code);  "#{color_code}#{text}\e[0m" end
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end
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​
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mark_Red   = "[+]".red
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mark_Green = "[+]".green
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​
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​
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host = ARGV[0] || "127.0.0.1"
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port = ARGV[1] || 21
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​
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# List of FTP protocol commands
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cmds = ["MKD","ACCL","TOP","CWD","STOR","STAT","LIST","RETR","NLST","LS","DELE","RSET","NOOP","UIDL","USER","APPE"]
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​
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buffer  = ["A"]
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counter = 1
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​
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cmds.each do |cmd|
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  buffer.each do |buf|
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​
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    while buffer.length <= 40
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      buffer << "A" * counter
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      counter += 100
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    end
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​
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    s = TCPSocket.open(host, port)
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    s.recv(1024)
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    s.send("USER ftp\r\n", 0)
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    s.recv(1024)
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    s.send("PASS ftp\r\n", 0)
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    s.recv(1024)
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    puts mark_Red + " Sending " + "#{cmd} ".green + "Command with " + "#{buf.size} bytes ".green  + "Evil buffer" + ".".green
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    s.send(cmd + " " + buf + "\r\n", 0)
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    s.recv(1024)
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    s.send("QUIT\r\n", 0)
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    s.close
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  end
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  puts "~~~~~~~~~~~~~~~~~~~~".red
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  sleep 0.5
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end
Copied!
I was thinking of making it a bit more elegant to give myself a chance to inspect and configure each command separately.
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#!/usr/bin/evn ruby
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#
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# KING SABRI | @KINGSABRI
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# Simple FTP COMMNDS Fuzzer
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#
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require 'socket'
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​
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if ARGV.size < 1 
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  puts "#{__FILE__} <host> [port]"
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  exit 0 
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else
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  @host = ARGV[0]
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  @port = ARGV[1] || 21
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end
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​
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def fuzz(payload)
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  begin 
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  s = TCPSocket.open(@host, @port)
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  s.recv(2048)
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  s.send payload, 0
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  s.recv(2048)
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  s.close
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  rescue
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    puts "Crash detected after #{payload.size} bytes"
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    exit 0
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  end
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end
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​
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def insertion(point="", buffer=0)
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  buffer = buffer * 10
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  points = 
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    {
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      core:           "A" * buffer, # Comment this line is it hangs the fuzzer
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      user: "USER " + "B" * buffer + "\r\n",
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      pass: "PASS " + "C" * buffer + "\r\n",
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      accl: "ACCL " + "D" * buffer + "\r\n",
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      appe: "APPE " + "E" * buffer + "\r\n",
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      cmd:  "CWD "  + "F" * buffer + "\r\n",
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      dele: "DELE " + "G" * buffer + "\r\n",
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      list: "LIST " + "H" * buffer + "\r\n",
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      ls:   "LS "   + "I" * buffer + "\r\n",
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      mkd:  "MKD "  + "J" * buffer + "\r\n",
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      nlst: "NLST " + "K" * buffer + "\r\n",
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      noop: "NOOP " + "L" * buffer + "\r\n",
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      retr: "RETR " + "M" * buffer + "\r\n",
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      rest: "RSET " + "N" * buffer + "\r\n",
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      stat: "STAT " + "O" * buffer + "\r\n",
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      stor: "STOR " + "P" * buffer + "\r\n",
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      top:  "TOP "  + "Q" * buffer + "\r\n",
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      uidl: "UIDL " + "R" * buffer + "\r\n"
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      }
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  return points[point] unless point.empty?
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  points
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end
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​
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puts "[+] Fuzzing #{@host} on port #{@port}..."
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insertion.keys.each do |point|
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  (1..500).each do |buffer|
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​
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    puts "[+] Fuzzing #{point.to_s}: #{insertion(point, buffer).size} bytes"
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    fuzz insertion(point, buffer)
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​
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  end
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end
Copied!
Note that, this script can be used for other protocols (IMAP, POP3, etc) since it deals with socket!.

Module 0x5 | Exploitation Kung Fu

Calling Windows APIs

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Contents

Mutation

FTP Fuzzer