unwrap_data.c

#include <ctype.h>
#include <errno.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#ifdef __WIN32
#include <winsock.h>
#else
#include <arpa/inet.h>
#endif

#include <openssl/evp.h>
#include <openssl/rand.h>

#define NONCE_LEN 13
#define TAG_LEN 16

static uint8_t KEY[] = {
  0x58, 0xdf, 0xe5, 0x21, 0x06, 0xa1, 0x61, 0x43, 0x71, 0x00, 0x1f, 0x66,
  0x9f, 0x50, 0x36, 0x36, 0xe9, 0x35, 0x4c, 0x18, 0x91, 0xa5, 0x35, 0xf4,
  0x69, 0xb7, 0x05, 0x67, 0xb7, 0xd9, 0x77, 0x68
};

static uint8_t wrapped_ed25519[] = {
  0x9a, 0x73, 0x7a, 0x13, 0x38, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x03, 0x94, 0x8d, 0x24, 0x1d, 0x35, 0x1c, 0x60, 0xca, 0xcd, 0x49, 0xc5,
  0xad, 0x01, 0xad, 0xd4, 0x17, 0xbb, 0xe8, 0xf8, 0xab, 0xa7, 0x64, 0x27,
  0xdc, 0x19, 0xe9, 0x3e, 0x9f, 0x24, 0xe4, 0x32, 0xda, 0xd9, 0x16, 0x0b,
  0x65, 0xf0, 0x9d, 0x51, 0x8e, 0x9d, 0x52, 0x41, 0x8d, 0x0e, 0xc1, 0xfb,
  0x6f, 0xe0, 0x90, 0xef, 0x3c, 0x23, 0x8f, 0x95, 0x19, 0x72, 0x93, 0x6b,
  0xcd, 0x13, 0x47, 0x9c, 0xe2, 0x9b, 0xc4, 0x7e, 0x4a, 0xac, 0x8d, 0x57,
  0xd6, 0xf9, 0xaf, 0x24, 0x79, 0x92, 0xf4, 0x68, 0x1d, 0xb0, 0xcc, 0x7c,
  0xcd, 0xc6, 0x12, 0x8a, 0x29, 0x4c, 0xe6, 0xe2, 0xc7, 0xbd, 0xa8, 0x12,
  0xc6, 0x77, 0xae, 0xd0, 0x4e, 0xf7, 0x6a, 0xdc, 0xcf, 0x0d, 0x38, 0x94,
  0xad, 0x87, 0x45, 0x52, 0x07, 0x4c, 0x6b, 0xf2, 0xd0, 0x45, 0xcc, 0x1c,
  0x69, 0x8e, 0xc6, 0xcf, 0x2d, 0xb8, 0xf3, 0xe3, 0x10, 0xfd, 0xdc, 0x0e,
  0x1f, 0x4b, 0xff, 0x21, 0x7b, 0x08, 0x1a, 0xa0, 0x79, 0xa3, 0x57, 0x5c,
  0x3b, 0x37, 0x03, 0xe0, 0xd1, 0xf2, 0xa2, 0x42, 0x14, 0xbf, 0x6e, 0xfb,
  0xd0, 0x4d, 0x94, 0x78, 0xfa, 0x6d, 0xec, 0x29, 0x5e, 0xe2, 0x79, 0xc1,
  0x8b, 0xd2, 0x67, 0x7c
};

static bool unwrap_data(uint8_t *key, size_t key_len,
                        uint8_t *nonce, size_t nonce_len,
                        uint8_t *in, size_t in_len,
                        uint8_t *out, size_t *out_len) {

  EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
  const EVP_CIPHER *cipher_type;

  int len = 0;

  switch (key_len) {
    case 16:
      cipher_type = EVP_aes_128_ccm();
      break;

    case 24:
      cipher_type = EVP_aes_192_ccm();
      break;

    case 32:
      cipher_type = EVP_aes_256_ccm();
      break;

    default:
      return false;
  }

  // Select cipher
  if (EVP_DecryptInit_ex(ctx, cipher_type, NULL, NULL, NULL) != 1) {
    return false;
  }

  // Set nonce length
  if (EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_IVLEN, nonce_len, NULL) != 1) {
    return false;
  }

  // Set tag length
  if (EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_TAG, TAG_LEN, in + in_len - TAG_LEN) != 1) {
        return false;
  }

  // Initialize key and IV
  if (EVP_DecryptInit_ex(ctx, NULL, NULL, key, nonce) != 1) {
    return false;
  }

  // Provide the message to be decrypted, and obtain the decrypted output
  if (EVP_DecryptUpdate(ctx, out, &len, in, in_len - TAG_LEN) != 1) {
    return false;
  }
  *out_len = len;

  // Clean up
  EVP_CIPHER_CTX_free(ctx);

  return true;
}

int main(int argc, char *argv[]) {

  uint8_t out[2048];
  size_t out_len = sizeof(out);

  if (unwrap_data(KEY, sizeof(KEY), wrapped_ed25519, NONCE_LEN, wrapped_ed25519 + NONCE_LEN, sizeof(wrapped_ed25519) - NONCE_LEN, out, &out_len) == false) {
    printf("Decryption failed\n");
  }
  else {
    for (int i = 0; i < out_len; i++) {
      printf("%c", out[i]);
    }
  }

  return 0;
}