BUFFER OVERFLOW ARENA

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

void hacked() {
    printf("System Compromised!\n");
}

void login() {
    char buffer[8];
    int authenticated = 0;
    
    printf("Enter payload: ");
    // VULNERABILITY: gets() does not check bounds!
    gets(buffer); 
    
    if (authenticated) {
        printf("Access Granted.\n");
    }
}

int main() {
    login();
    return 0;
}
#include <stdio.h>
#include <string.h>

void hacked() {
    printf("System Compromised!\n");
}

void login() {
    char buffer[8];
    int authenticated = 0;
    
    printf("Enter payload: ");
    // SECURE: fgets() strictly limits input to buffer size.
    fgets(buffer, sizeof(buffer), stdin); 
    
    if (authenticated) {
        printf("Access Granted.\n");
    }
}

int main() {
    login();
    return 0;
}
Terminal Output
$ ./vulnerable_program
Enter payload:

Memory Stack Diagram

Lower
Memory Higher
Memory
(Stack Grows Down ↓)
Buffer
EBP
EIP

Control Panel

Inject data into the program's memory. Watch how standard functions like gets() blindly write beyond their allocated space.

0/24

Characters animate into memory blocks sequentially.

Target

The vulnerable buffer is only 8 bytes. The next byte is EBP, and the following is the Return Address (EIP).

Can you overwrite EIP with 0xEF or HACK?