Function cryptoMessageDigestGet

plugins/experimental/access_control/utils.cc:201–219

* @brief Calculate message digest * * @param digestType digest name * @param data ptr to input message for calculating the digest * @param dataLen message length * @param key ptr to a counted string containing the key (secret) * @param keyLen key length * @param out ptr to where to store the digest * @param outLen length of the out buffer (must be at least MAX_MSGDIGEST_BUFFER_SIZE) * @re

 * @return the number of character actually written to the buffer.
 */
size_t
cryptoMessageDigestGet(const char *digestType, const char *data, size_t dataLen, const char *key, size_t keyLen, char *out,
                       size_t /* outLen ATS_UNUSED */)
{
  const EVP_MD *md  = nullptr;
  unsigned int  len = 0;
  char          buffer[256];

  if (!(md = EVP_get_digestbyname(digestType))) {
    AccessControlError("unknown digest name '%s'", digestType);
    return 0;
  }

  if (!HMAC(md, reinterpret_cast<const unsigned char *>(key), keyLen, reinterpret_cast<const unsigned char *>(data), dataLen,
            reinterpret_cast<unsigned char *>(out), &len)) {
    AccessControlError("failed to get the signing hash: %s", cryptoErrStr(buffer, sizeof(buffer)));
  }
  return len;
}

/**
 * @brief Check if 2 message digests are the same using a constant-time openssl function to avoid timing attacks.