[C:Source]: Buffer Overflow Challenge

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

// BlackFox's-Team (c)
// Twitter and Telegram: @BlackfoxsOrg
// By ABaDy ( Twitter: @yxs )

char *userroot = "root";
char *passroot = "no password in source ;)";
void welcome()
{
    printf("\n\nWelcome engineer!\n");
    printf("You have logged in successfully!\n");
    printf("Take your flag : no falg in Source ;)\n");
}

void start()
{
    char username[30];
    char password[30];
    printf("login As : ");
    scanf("%s", username);
    if(strcmp(userroot,username)==0)
    {
        printf("%s@labs.blackfoxs.org's password: ",username);
        scanf("%s", password);
        if(strcmp(password,passroot)==0){
            welcome();
        }else{
            printf("access denied!, password not match\n");
        }
    }else{
        printf("access denied!, user not found\n");
    }
}
void blackfoxs(){
    printf("\nWelcome to BlackFox's-Labs (c)\n");
    printf("Twitter and Telegram: @BlackfoxsOrg\n\n");
}
int main()
{
    setvbuf(stdout, NULL, _IONBF, 0);
    blackfoxs();
    start();
    return 0;
}