message: Fix sign warning
diff: @@ -39,7 +39,7 @@ int pem_passwd_cb(char* buf, int size, int, void* ptr) {
  auto passphrase = reinterpret_cast<session*>(ptr)->openssl_passphrase();
  strncpy(buf, passphrase, static_cast<size_t>(size));
  buf[size - 1] = '\0';
  - return strlen(buf);
  + return static_cast<int>(strlen(buf));
  }
  } // namespace <anonymous>
  