canary_test.c

// Demo del stack canary.
//
// Compilar dos veces:
//   gcc -fstack-protector-all   canary_test.c -o canary_on
//   gcc -fno-stack-protector    canary_test.c -o canary_off
//
// Ejecutar ambos con un argumento largo (>16 bytes) y comparar:
//   ./canary_on  AAAAAAAAAAAAAAAAAAAAAAAAAAAAAA   ← *** stack smashing detected ***
//   ./canary_off AAAAAAAAAAAAAAAAAAAAAAAAAAAAAA   ← segfault o ejecución sospechosa
#include <stdio.h>
#include <string.h>

void copy_input(char *src) {
    char buf[16];
    strcpy(buf, src);              // ⚠ overflow si src > 15 chars + null
    printf("[ok] buf = \"%s\"\n", buf);
}

int main(int argc, char *argv[]) {
    if (argc < 2) { printf("Uso: %s <input>\n", argv[0]); return 1; }
    copy_input(argv[1]);
    return 0;
}