Tech Challenge

This C function is compiled with GCC's -fstack-protector-strong, and an attacker overflows buf via the unchecked strcpy. How does the inserted stack canary defend against the classic 'overwrite the saved return address' exploit?

void handle(const char *input) {
    char buf[64];
    strcpy(buf, input);   /* no bounds check */
    /* ... use buf ... */
}