Vulnerability Development mailing list archives
Re: shellcoding on gentoo
From: security () spinfoo net
Date: Wed, 22 Feb 2006 23:42:44 +0100
Hi Borja, On Mon, Feb 20, 2006 at 01:56:45AM +0100, Borja wrote:
Hi Lot of ppl tell me that I did not proper zero the EAX register,so 3 MSB of eax corrupt trapping the syscall, but Its OK. I successfully run the shellcodes on a debian box,but in gentoo,allways SEGFAULT. There is it, a new log: ------------------------------------------------------------------------------------------------------------------------------------------------------ petalo shellcode # cat 1.asm BITS 32 ;exit() xor eax,eax xor ebx,ebx mov eax,1 int 0x80 petalo shellcode # nasm -g -f elf 1.asm petalo shellcode # ld 1.o ld: warning: cannot find entry symbol _start; defaulting to 00000000080480a0
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The above line is self-explanatory, you forget add _start symbol to your assembler program to let ld do its work properly, i suggest you that write your assembler programs in a more standard way (to avoid problems with diferent distros, etc), that's it: $ cat new1.asm Section .text global _start _start: xor ebx,ebx ;= mov ebx,0 | 31 db mov al,1 ;= mov eax,1 | b0 01 int 0x80 ; | cd 80 If you forget add _start symbol the linker don't know when it has to start to read the code(instruccions). This program should work on any linux distro. Then: $ nasm -f elf new1.asm and get OPcodes. I hope that this helps you.
Current thread:
- Re: shellcoding on gentoo apriori (Feb 01)
- <Possible follow-ups>
- Re: shellcoding on gentoo nonexistent (Feb 07)
- Re: shellcoding on gentoo Borja (Feb 21)
- Re: shellcoding on gentoo Mike Davis (Feb 21)
- Re: shellcoding on gentoo DJ Ether (Feb 21)
- Re: shellcoding on gentoo Mike Davis (Feb 21)
- Re: shellcoding on gentoo security (Feb 22)