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

#define KEY_SIZE 8

/*
 * Scenario:
 * Adam is a security researcher for a well known security company, he has
 * intercepted the code below as well as an encrypted PNG from the notorious
 * hacker "HaPPi". Unfortunately C code confuses Adam, can you help Adam decrypt
 * the PNG file?
 *
 * Objectives:
 * - Compile the code
 * - Make comments on the general security of the code and how it is vulnerable
 * - Reveal the contents of the encrypted file, preferably using the vulnerability!
 * - How would you fix the code so that it is not vulnerable
 */

int main(int argc, char **argv)
{
	char static key[] = {0xD, 0xE, 0xA, 0xD, 0xB, 0xE, 0xE, 0xF};
	int fd_in, fd_out, i;
	char store[KEY_SIZE];
	char buff[30];
	int flag = 0;

	setuid(0); // This makes things work...

	if ( argc < 2 )
	{
		printf("Usage: %s <password>\n", argv[0]);
		exit(1);
	}

	strcpy(buff,argv[1]);

	if(strcmp(buff, "IamSuperL33t"))
	{
		printf("Wrong Password\n");
	}
	else
	{
		flag++;
	}
	if(flag)
	{
		printf("Correct Password\n");
		if ((fd_in = open("encrypted.png", O_RDONLY)) < 0)
		{
			perror("Could not open in_file")
			exit(1);
		}

		if ((fd_out = open("decrypted.png", O_WRONLY|O_CREAT, S_IRUSR|S_IWUSR)) < 0)
		{
			perror("Could not open out_file!");
			exit(1);
		}

		while (read(fd_in, &store, KEY_SIZE))
		{
			for (i=0; i<KEY_SIZE; i++)
			{
				store[i] = store[i] ^ key[i];
			}

			if (!write(fd_out, &store, KEY_SIZE))
			{
				perror("This shouldn't have happened, contact Techsupport");
				exit(-1);
			}
		}
	}
	return 0;
}