Buffer_Overflow.md

Buffer Overflow

The code below is vulnureable to Buffer Overflow

char str1[10];
char str2[]="text";
strcpy(str1,str2);

Why it's vulnerable?

When the strcpy() function is called, it copies the contents of str2 into str1, but str1 is not large enough to hold the entire contents of str2.

Impact?

This could lead to a buffer overflow, where data is written outside of the bounds of the str1 array, potentially leading to a crash or other undefined behavior.

How to fix?

To fix this issue, you can either make sure that str1 is large enough to hold the contents of str2, or use a safer alternative to strcpy() such as strncpy() which allows you to specify the maximum number of characters to be copied.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_LENGTH 10

int main() {
    char str1[MAX_LENGTH+1]; // Add 1 to include null terminator
    const char *str2 = "text";

    // Copy at most MAX_LENGTH characters from str2 to str1
    strncpy(str1, str2, MAX_LENGTH);
    str1[MAX_LENGTH] = '\0'; // Ensure null terminator is present

    printf("str1: %s\n", str1);
    return 0;
}