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| #include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#define MAX_LEN 1024
#define FLAG_LEN 30
void upkeep() {
setvbuf(stdin, NULL, _IONBF, 0);
setvbuf(stdout, NULL, _IONBF, 0);
setvbuf(stderr, NULL, _IONBF, 0);
}
void print_hex(char* buf, int len) {
for (int i=0; i<len; i++) {
printf("%02x", (unsigned char)buf[i]);
}
printf("\n");
}
void encrypt(char* msg, int len, char* iv) {
char key[len];
FILE *file;
file = fopen("/dev/urandom", "rb");
fread(key, len, 1, file);
fclose(file);
for (int i=0; i<len; i++) {
msg[i] = msg[i] ^ key[i] ^ iv[i % 8];
}
}
void randomize(char* msg, int len, unsigned long seed, unsigned long iterations) {
seed = seed * iterations + len;
if (iterations > 1) {
randomize(msg, len, seed, iterations- 1);
} else {
encrypt(msg, len, ((char *) &seed));
}
}
char menu() {
char option;
printf("\nSelect from the options below:\n");
printf("1. Encrypt a message\n");
printf("2. View the encrypted message\n");
printf("3. Quit\n");
printf("> ");
scanf("%c", &option);
while (getchar() != '\n');
return option;
}
void console() {
FILE* file;
long seed;
int index;
int read_len;
char buf[MAX_LEN] = "";
int len = -1;
while (1) {
switch(menu()) {
case '1':
printf("\nPlease enter message to encrypt: ");
fgets(buf, MAX_LEN-FLAG_LEN, stdin);
len = strlen(buf);
file = fopen("flag.txt", "rb");
fread(buf + len, FLAG_LEN, 1, file);
fclose(file);
len += FLAG_LEN;
seed = ((long) rand()) << 32 + rand();
randomize(buf, len, seed, buf[0]);
break;
case '2':
if(len == -1) {
printf("Sorry, you need to encrypt a message first.\n");
break;
}
index = 0;
printf("\nRead a substring of the encrypted message.");
printf("\nPlease enter the starting index (%d - %d): ", index, len);
scanf("%d", &index);
while (getchar() != '\n');
if (index > len) {
printf("Error, index out of bounds.\n");
break;
}
printf("Here's your encrypted string with the flag:\n");
print_hex(buf+index, len - index);
break;
case '3':
printf("goodbye.\n");
exit(0);
default:
printf("There was an error processing that request, please try again.\n");
break;
}
}
}
int main() {
srand(time(NULL));
upkeep();
printf("Welcome to my encryption engine: ENCRYPT-INATOR!\n");
printf("I'll encrypt anything you want but no guarantees you'll be able to decrypt it,\n");
printf("I haven't quite figured out how to do that yet... :(\n");
console();
}
|