login.c

#include <stdio.h>

char password[128];

void generate_password() {
	FILE *file = fopen("/dev/urandom","r");
	fgets(password, 128, file);
	fclose(file);
}

void main() {
	puts("Welcome to my ultra secure login service!");

	// no way they can guess my password if it's random!
	generate_password();

	char input[128];
	printf("Enter the password: ");
	fgets(input, 128, stdin);

	if (strcmp(input, password) == 0) {
		char flag[128];

		FILE *file = fopen("flag.txt","r");
		if (!file) {
		    puts("Error: missing flag.txt.");
		    exit(1);
		}

		fgets(flag, 128, file);
		puts(flag);
	} else {
		puts("Wrong!");
	}
}