tjcrypt/main.c

#include <lz4.h>
#include <stdio.h>
#include <stdlib.h>

#include "xxtea.h"

const unsigned char key[16] =
    "\xd2\"\x82\x7f\xe9\xd3r\xa5$\x90\x8cm\n\x96\xcb\xa3";
const unsigned char password[16] = "MODDEDBYPL0NK!!!";
const int key_len = 16;

void tj_decrypt(const char *path, const char *out) {
  unsigned char tmp = 0, fix_key[16] = {0};
  unsigned char *dec = 0, *dst = 0;
  xxtea_long ret = 0;

  FILE *f = fopen(path, "rb");
  fseek(f, 0, SEEK_END);
  long size = ftell(f);
  fseek(f, 0, SEEK_SET);

  char *buffer = malloc(size + 1);
  fread(buffer, 1, size, f);
  fclose(f);

  if (buffer[0] != 't' || buffer[1] != 'j' || buffer[2] != '!') {
    fprintf(stderr, "can't decrypt this type of file\n");
    goto BAIL_OUT;
  }

  for (int i = 0; i < 16; i++) {
    tmp = key[i % key_len];
    fix_key[i] ^= tmp ^ buffer[i + 3];
  }

  dec = xxtea_decrypt(buffer + 23, size - 23, fix_key, 16, &ret);
  if (!ret) goto BAIL_OUT;

  unsigned int dstSz = *(unsigned int *)dec;
  if (dstSz != *(unsigned int *)(buffer + 19)) goto BAIL_OUT;

  dst = malloc(dstSz + 1);
  if (!dst) goto BAIL_OUT;

  LZ4_decompress_safe(dec + 4, dst, ret - 4, dstSz);

  f = fopen(out, "wb");
  fwrite(dst, dstSz, 1, f);
  fclose(f);

BAIL_OUT:
  free(dst);
  free(buffer);

  return;
}

void tj_encrypt(const char *path, const char *out) {
  unsigned char tmp = 0, fix_key[16] = {0};
  unsigned char *enc = 0, *dst = 0;
  xxtea_long ret = 0;

  FILE *f = fopen(path, "rb");
  fseek(f, 0, SEEK_END);
  long size = ftell(f);
  fseek(f, 0, SEEK_SET);

  char *buffer = malloc(size + 1);
  fread(buffer, 1, size, f);
  fclose(f);

  dst = malloc(size*2+1);
  ret = LZ4_compress_default(buffer, dst + 4, size, size*2);
  if (!ret) {
    fprintf(stderr, "failed compressing\n");
    goto BAIL_OUT;
  }
  fprintf(stderr, "[ret] %ld %d\n", size*2, ret);

  for (int i = 0; i < 16; i++) {
    tmp = key[i % key_len];
    fix_key[i] ^= tmp ^ password[i];
  }

  f = fopen(out, "wb");
  fwrite("tj!", 3, 1, f);
  fwrite(password, 16, 1, f);
  fwrite(&size, 4, 1, f);

  *(unsigned int*) dst = size;
  size = ret;
  ret = 0;

  enc = xxtea_encrypt(dst, size + 4, fix_key, 16, &ret);
  if (!ret) {
    fprintf(stderr, "failed encrypting\n");
    goto BAIL_OUT;
  }
  fprintf(stderr, "[ret] %ld %d\n", size, ret);

  fwrite(enc, ret, 1, f);
  fclose(f);

BAIL_OUT:
  free(dst);
  free(buffer);

  return;
}

int main(int argc, char const *argv[]) {
  if (argc < 4) goto HELP;
  switch (argv[1][0]) {
    case 'e':
      /* encrypt */
      tj_encrypt(argv[2], argv[3]);
      break;
    case 'd':
      /* decrypt */
      tj_decrypt(argv[2], argv[3]);
      break;
    default:
    HELP:
      fprintf(stderr, "usage: %s [d|e] in out\n", argv[0]);
      break;
  }
  return 0;
}