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Re: shellcoding on gentoo

just out of curiosity.. i tried out your code as presented (using gcc/gdb/p4/gentoo)

phar@foster ~ $ uname -a
Linux foster 2.4.30-grsec-2.1.5 #8 Mon Aug 29 15:20:57 EDT 2005 i686 Intel(R) Celeron(R) CPU 2.40GHz GenuineIntel GNU/Linux

(gdb) disassemble main
Dump of assembler code for function main:
0x08048354 <main+0>:    xor    %eax,%eax
0x08048356 <main+2>:    xor    %ebx,%ebx
0x08048358 <main+4>:    mov    $0x1,%eax
0x0804835d <main+9>:    int    $0x80
0x0804835f <main+11>:   leave
(gdb) run
Starting program: /home/phar/a.out

Program exited normally.
(gdb) break main
Breakpoint 1 at 0x8048354
(gdb) display /i $eip
(gdb) run
Starting program: /home/phar/a.out

Breakpoint 1, 0x08048354 in main ()
Breakpoint 1 at 0x8048354
1: x/i $eip  0x8048354 <main>:  xor    %eax,%eax
(gdb) stepi
0x08048356 in main ()
1: x/i $eip  0x8048356 <main+2>:        xor    %ebx,%ebx
0x08048358 in main ()
1: x/i $eip  0x8048358 <main+4>:        mov    $0x1,%eax
0x0804835d in main ()
1: x/i $eip  0x804835d <main+9>:        int    $0x80

Program exited normally.


----- Original Message ----- From: "Borja" <padre@xxxxxxxxxxxxx>
To: <vuln-dev@xxxxxxxxxxxxxxxxx>
Sent: Sunday, February 19, 2006 7:56 PM
Subject: Re: shellcoding on gentoo


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

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
petalo shellcode # ./a.out
Segmentation fault
petalo shellcode # gdb -q a.out
Using host libthread_db library "/lib/libthread_db.so.1".
(gdb) break 1
Breakpoint 1 at 0x80480a0: file 1.asm, line 1.
(gdb) r
Starting program: /root/code/shellcode/a.out

Program terminated with signal SIGSEGV, Segmentation fault.
The program no longer exists.
You can't do that without a process to debug.
(gdb) q

petalo shellcode #
Linux petalo 2.6.12-gentoo-r6 #9 Sat Dec 24 14:37:56 CET 2005 i686 AMD Athlon(tm) XP 1600+ AuthenticAMD GNU/Linux


I cant explain why SIGFAULT.
I did not edit any advanced kernel configurations rather than snd card and ethernet.

Thanks in advance.