absl::Status SignDigest()

in kmscng/operation/sign_utils.cc [308:349]

• 37 lines of code
• 5 McCabe index (conditional complexity)

absl::Status SignDigest(Object* object, absl::Span<const uint8_t> digest,
                        absl::Span<uint8_t> signature) {
  ASSIGN_OR_RETURN(const EVP_MD* md, DigestForAlgorithm(object->algorithm()));

  if (digest.size() != EVP_MD_size(md)) {
    return NewInvalidArgumentError(
        absl::StrFormat("provided digest has incorrect size (got %d, want %d)",
                        digest.size(), EVP_MD_size(md)),
        NTE_INVALID_PARAMETER, SOURCE_LOCATION);
  }

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

  kms_v1::AsymmetricSignRequest req;
  req.set_name(std::string(object->kms_key_name()));

  int digest_nid = EVP_MD_type(md);
  switch (digest_nid) {
    case NID_sha256:
      req.mutable_digest()->set_sha256(digest.data(), digest.size());
      break;
    case NID_sha384:
      req.mutable_digest()->set_sha384(digest.data(), digest.size());
      break;
    default:
      return NewInternalError(
          absl::StrFormat("unhandled digest type: %d", digest_nid),
          SOURCE_LOCATION);
  }

  ASSIGN_OR_RETURN(kms_v1::AsymmetricSignResponse resp,
                   object->kms_client()->AsymmetricSign(req));
  RETURN_IF_ERROR(CopySignature(object, resp.signature(), signature));
  return absl::OkStatus();
}