absl::Status RsaRawPkcs1Signer::Sign()

in kmsp11/operation/rsassa_raw_pkcs1.cc [92:129]
32 lines of code
3 McCabe index (conditional complexity)

absl::Status RsaRawPkcs1Signer::Sign(KmsClient* client,
                                     absl::Span<const uint8_t> data,
                                     absl::Span<uint8_t> signature) {
  size_t key_byte_length = RSA_size(key_.get());
  constexpr size_t kRsaPkcs1OverheadBytes = 11;
  // I don't know how we'd end up with a <11-byte key, but for completeness, and
  // to avoid unsigned underflow...
  CHECK_GE(key_byte_length, kRsaPkcs1OverheadBytes);
  size_t max_data_byte_length = key_byte_length - kRsaPkcs1OverheadBytes;

  if (data.size() > max_data_byte_length) {
    return NewInvalidArgumentError(
        absl::StrFormat("data length (%d bytes) exceeds maximum allowed "
                        "for a %d-bit key (%d bytes)",
                        data.size(), RSA_bits(key_.get()),
                        max_data_byte_length),
        CKR_DATA_LEN_RANGE, SOURCE_LOCATION);
  }

  if (signature.size() != signature_length()) {
    return NewInternalError(
        absl::StrFormat(
            "provided signature buffer has incorrect size (got %d, want %d)",
            signature.size(), signature_length()),
        SOURCE_LOCATION);
  }

  kms_v1::AsymmetricSignRequest req;
  req.set_name(std::string(object_->kms_key_name()));
  req.set_data(
      std::string(reinterpret_cast<const char*>(data.data()), data.size()));

  ASSIGN_OR_RETURN(kms_v1::AsymmetricSignResponse resp,
                   client->AsymmetricSign(req));
  std::copy(resp.signature().begin(), resp.signature().end(),
            signature.begin());
  return absl::OkStatus();
}