OSEC

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Re: Re: Linux restricted ASCII Shellcode

nonexistantnospam.org
Date: Sun Apr 22 2007 - 05:42:24 CDT


Yes I'm having a seg-fault, but I can't catch you...
AFAIK when EIP is pointing somewhere in the NOP sled, no matter how the shellcode is aligned... Alignment has nothing to do here...?¿? I'm wrong?
More over, I've tryed more than 5 different ASCII shellcodes all with the same result... Always segfaulting. It looks as if shellcodes where not working for any common reason...
So, summarizing:
1.- I can perfectly overwrite RET thus having EIP pointing almost 100% of the time to the NOP's of my shellcode (in an environment variable)
2.- My -non-ascii- shellcode works perfectly
3.- Whn I try with ANY pure ascii shellcode, it fails 100% of the time.

What is happening?

I've tryed with pure ASCII shellcodes ripped from http://shellcode.org/Shellcode/linux/ascii/ among others...

Metasploit framework failed to convert the original shellcode -the one that works- to pure ascii with the selected charset (A-Z,a-z,0-9).

That's the original shellcode:

\xeb\x1f\x5e\x89\x76\x08\x31\xc0\x88\x46\x07\x89\x46\x0c\xb0\x0b\x89\xf3\x8d\x4e\x08\x8d\x56\x0c\xcd\x80\x31\xdb\x89\xd8\x40\xcd\x80\xe8\xdc\xff\xff\xff/bin/sh

Is anyone able to convert this to pure ASCII or giving me a working pure ASCII shellcode or helping me understand why all the pure ascii shellcodes are failing in my exploit?

Thank you,