cc/hybrid/hpke_proto_serialization.cc

// Copyright 2023 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
////////////////////////////////////////////////////////////////////////////////

#include "tink/hybrid/hpke_proto_serialization.h"

#include <string>

#include "absl/base/attributes.h"
#include "absl/status/status.h"
#include "absl/strings/string_view.h"
#include "absl/types/optional.h"
#include "tink/hybrid/hpke_parameters.h"
#include "tink/hybrid/hpke_private_key.h"
#include "tink/hybrid/hpke_public_key.h"
#include "tink/insecure_secret_key_access.h"
#include "tink/internal/key_parser.h"
#include "tink/internal/key_serializer.h"
#include "tink/internal/mutable_serialization_registry.h"
#include "tink/internal/parameters_parser.h"
#include "tink/internal/parameters_serializer.h"
#include "tink/internal/proto_key_serialization.h"
#include "tink/internal/proto_parameters_serialization.h"
#include "tink/partial_key_access.h"
#include "tink/restricted_data.h"
#include "tink/secret_key_access_token.h"
#include "tink/util/status.h"
#include "tink/util/statusor.h"
#include "proto/hpke.pb.h"
#include "proto/tink.pb.h"

namespace crypto {
namespace tink {
namespace {

using ::google::crypto::tink::HpkeAead;
using ::google::crypto::tink::HpkeKdf;
using ::google::crypto::tink::HpkeKem;
using ::google::crypto::tink::HpkeKeyFormat;
using ::google::crypto::tink::HpkeParams;
using ::google::crypto::tink::KeyData;
using ::google::crypto::tink::OutputPrefixType;

using HpkeProtoParametersParserImpl =
    internal::ParametersParserImpl<internal::ProtoParametersSerialization,
                                   HpkeParameters>;
using HpkeProtoParametersSerializerImpl =
    internal::ParametersSerializerImpl<HpkeParameters,
                                       internal::ProtoParametersSerialization>;
using HpkeProtoPublicKeyParserImpl =
    internal::KeyParserImpl<internal::ProtoKeySerialization, HpkePublicKey>;
using HpkeProtoPublicKeySerializerImpl =
    internal::KeySerializerImpl<HpkePublicKey, internal::ProtoKeySerialization>;
using HpkeProtoPrivateKeyParserImpl =
    internal::KeyParserImpl<internal::ProtoKeySerialization, HpkePrivateKey>;
using HpkeProtoPrivateKeySerializerImpl =
    internal::KeySerializerImpl<HpkePrivateKey,
                                internal::ProtoKeySerialization>;

const absl::string_view kPublicTypeUrl =
    "type.googleapis.com/google.crypto.tink.HpkePublicKey";
const absl::string_view kPrivateTypeUrl =
    "type.googleapis.com/google.crypto.tink.HpkePrivateKey";

util::StatusOr<HpkeParameters::Variant> ToVariant(
    OutputPrefixType output_prefix_type) {
  switch (output_prefix_type) {
    case OutputPrefixType::LEGACY:
      ABSL_FALLTHROUGH_INTENDED;  // Parse LEGACY output prefix as CRUNCHY.
    case OutputPrefixType::CRUNCHY:
      return HpkeParameters::Variant::kCrunchy;
    case OutputPrefixType::RAW:
      return HpkeParameters::Variant::kNoPrefix;
    case OutputPrefixType::TINK:
      return HpkeParameters::Variant::kTink;
    default:
      return util::Status(absl::StatusCode::kInvalidArgument,
                          "Could not determine HpkeParameters::Variant");
  }
}

util::StatusOr<OutputPrefixType> ToOutputPrefixType(
    HpkeParameters::Variant variant) {
  switch (variant) {
    case HpkeParameters::Variant::kCrunchy:
      return OutputPrefixType::CRUNCHY;
    case HpkeParameters::Variant::kNoPrefix:
      return OutputPrefixType::RAW;
    case HpkeParameters::Variant::kTink:
      return OutputPrefixType::TINK;
    default:
      return util::Status(absl::StatusCode::kInvalidArgument,
                          "Could not determine output prefix type.");
  }
}

util::StatusOr<HpkeParameters::KemId> ToKemId(HpkeKem kem) {
  switch (kem) {
    case HpkeKem::DHKEM_P256_HKDF_SHA256:
      return HpkeParameters::KemId::kDhkemP256HkdfSha256;
    case HpkeKem::DHKEM_P384_HKDF_SHA384:
      return HpkeParameters::KemId::kDhkemP384HkdfSha384;
    case HpkeKem::DHKEM_P521_HKDF_SHA512:
      return HpkeParameters::KemId::kDhkemP521HkdfSha512;
    case HpkeKem::DHKEM_X25519_HKDF_SHA256:
      return HpkeParameters::KemId::kDhkemX25519HkdfSha256;
    default:
      return util::Status(absl::StatusCode::kInvalidArgument,
                          "Could not determine KEM.");
  }
}

util::StatusOr<HpkeKem> FromKemId(HpkeParameters::KemId kem_id) {
  switch (kem_id) {
    case HpkeParameters::KemId::kDhkemP256HkdfSha256:
      return HpkeKem::DHKEM_P256_HKDF_SHA256;
    case HpkeParameters::KemId::kDhkemP384HkdfSha384:
      return HpkeKem::DHKEM_P384_HKDF_SHA384;
    case HpkeParameters::KemId::kDhkemP521HkdfSha512:
      return HpkeKem::DHKEM_P521_HKDF_SHA512;
    case HpkeParameters::KemId::kDhkemX25519HkdfSha256:
      return HpkeKem::DHKEM_X25519_HKDF_SHA256;
    default:
      return util::Status(absl::StatusCode::kInvalidArgument,
                          "Could not determine KEM.");
  }
}

util::StatusOr<HpkeParameters::KdfId> ToKdfId(HpkeKdf kdf) {
  switch (kdf) {
    case HpkeKdf::HKDF_SHA256:
      return HpkeParameters::KdfId::kHkdfSha256;
    case HpkeKdf::HKDF_SHA384:
      return HpkeParameters::KdfId::kHkdfSha384;
    case HpkeKdf::HKDF_SHA512:
      return HpkeParameters::KdfId::kHkdfSha512;
    default:
      return util::Status(absl::StatusCode::kInvalidArgument,
                          "Could not determine KDF.");
  }
}

util::StatusOr<HpkeKdf> FromKdfId(HpkeParameters::KdfId kdf_id) {
  switch (kdf_id) {
    case HpkeParameters::KdfId::kHkdfSha256:
      return HpkeKdf::HKDF_SHA256;
    case HpkeParameters::KdfId::kHkdfSha384:
      return HpkeKdf::HKDF_SHA384;
    case HpkeParameters::KdfId::kHkdfSha512:
      return HpkeKdf::HKDF_SHA512;
    default:
      return util::Status(absl::StatusCode::kInvalidArgument,
                          "Could not determine KDF.");
  }
}

util::StatusOr<HpkeParameters::AeadId> ToAeadId(HpkeAead aead) {
  switch (aead) {
    case HpkeAead::AES_128_GCM:
      return HpkeParameters::AeadId::kAesGcm128;
    case HpkeAead::AES_256_GCM:
      return HpkeParameters::AeadId::kAesGcm256;
    case HpkeAead::CHACHA20_POLY1305:
      return HpkeParameters::AeadId::kChaCha20Poly1305;
    default:
      return util::Status(absl::StatusCode::kInvalidArgument,
                          "Could not determine AEAD.");
  }
}

util::StatusOr<HpkeAead> FromAeadId(HpkeParameters::AeadId aead_id) {
  switch (aead_id) {
    case HpkeParameters::AeadId::kAesGcm128:
      return HpkeAead::AES_128_GCM;
    case HpkeParameters::AeadId::kAesGcm256:
      return HpkeAead::AES_256_GCM;
    case HpkeParameters::AeadId::kChaCha20Poly1305:
      return HpkeAead::CHACHA20_POLY1305;
    default:
      return util::Status(absl::StatusCode::kInvalidArgument,
                          "Could not determine AEAD.");
  }
}

util::StatusOr<HpkeParameters> ToParameters(OutputPrefixType output_prefix_type,
                                            HpkeParams params) {
  util::StatusOr<HpkeParameters::Variant> variant =
      ToVariant(output_prefix_type);
  if (!variant.ok()) {
    return variant.status();
  }

  util::StatusOr<HpkeParameters::KemId> kem_id = ToKemId(params.kem());
  if (!kem_id.ok()) {
    return kem_id.status();
  }

  util::StatusOr<HpkeParameters::KdfId> kdf_id = ToKdfId(params.kdf());
  if (!kdf_id.ok()) {
    return kdf_id.status();
  }

  util::StatusOr<HpkeParameters::AeadId> aead_id = ToAeadId(params.aead());
  if (!aead_id.ok()) {
    return aead_id.status();
  }

  return HpkeParameters::Builder()
      .SetVariant(*variant)
      .SetKemId(*kem_id)
      .SetKdfId(*kdf_id)
      .SetAeadId(*aead_id)
      .Build();
}

util::StatusOr<HpkeParams> FromParameters(HpkeParameters parameters) {
  util::StatusOr<HpkeKem> kem = FromKemId(parameters.GetKemId());
  if (!kem.ok()) {
    return kem.status();
  }

  util::StatusOr<HpkeKdf> kdf = FromKdfId(parameters.GetKdfId());
  if (!kdf.ok()) {
    return kdf.status();
  }

  util::StatusOr<HpkeAead> aead = FromAeadId(parameters.GetAeadId());
  if (!aead.ok()) {
    return aead.status();
  }

  HpkeParams params;
  params.set_kem(*kem);
  params.set_kdf(*kdf);
  params.set_aead(*aead);

  return params;
}

util::StatusOr<HpkeParameters> ParseParameters(
    const internal::ProtoParametersSerialization& serialization) {
  if (serialization.GetKeyTemplate().type_url() != kPrivateTypeUrl) {
    return util::Status(absl::StatusCode::kInvalidArgument,
                        "Wrong type URL when parsing HpkeParameters.");
  }

  HpkeKeyFormat proto_key_format;
  if (!proto_key_format.ParseFromString(
          serialization.GetKeyTemplate().value())) {
    return util::Status(absl::StatusCode::kInvalidArgument,
                        "Failed to parse HpkeKeyFormat proto");
  }
  if (!proto_key_format.has_params()) {
    return util::Status(absl::StatusCode::kInvalidArgument,
                        "HpkeKeyFormat proto is missing params field.");
  }

  return ToParameters(serialization.GetKeyTemplate().output_prefix_type(),
                      proto_key_format.params());
}

util::StatusOr<HpkePublicKey> ParsePublicKey(
    const internal::ProtoKeySerialization& serialization,
    absl::optional<SecretKeyAccessToken> token) {
  if (serialization.TypeUrl() != kPublicTypeUrl) {
    return util::Status(absl::StatusCode::kInvalidArgument,
                        "Wrong type URL when parsing HpkePublicKey.");
  }

  google::crypto::tink::HpkePublicKey proto_key;
  const RestrictedData& restricted_data = serialization.SerializedKeyProto();
  if (!proto_key.ParseFromString(
          restricted_data.GetSecret(InsecureSecretKeyAccess::Get()))) {
    return util::Status(absl::StatusCode::kInvalidArgument,
                        "Failed to parse HpkePublicKey proto");
  }
  if (proto_key.version() != 0) {
    return util::Status(absl::StatusCode::kInvalidArgument,
                        "Only version 0 keys are accepted.");
  }

  util::StatusOr<HpkeParameters> parameters =
      ToParameters(serialization.GetOutputPrefixType(), proto_key.params());
  if (!parameters.ok()) {
    return parameters.status();
  }

  return HpkePublicKey::Create(*parameters, proto_key.public_key(),
                               serialization.IdRequirement(),
                               GetPartialKeyAccess());
}

util::StatusOr<HpkePrivateKey> ParsePrivateKey(
    const internal::ProtoKeySerialization& serialization,
    absl::optional<SecretKeyAccessToken> token) {
  if (serialization.TypeUrl() != kPrivateTypeUrl) {
    return util::Status(absl::StatusCode::kInvalidArgument,
                        "Wrong type URL when parsing HpkePrivateKey.");
  }
  if (!token.has_value()) {
    return util::Status(absl::StatusCode::kPermissionDenied,
                        "SecretKeyAccess is required");
  }
  google::crypto::tink::HpkePrivateKey proto_key;
  const RestrictedData& restricted_data = serialization.SerializedKeyProto();
  if (!proto_key.ParseFromString(restricted_data.GetSecret(*token))) {
    return util::Status(absl::StatusCode::kInvalidArgument,
                        "Failed to parse HpkePrivateKey proto");
  }
  if (proto_key.version() != 0) {
    return util::Status(absl::StatusCode::kInvalidArgument,
                        "Only version 0 keys are accepted.");
  }

  util::StatusOr<HpkeParameters::Variant> variant =
      ToVariant(serialization.GetOutputPrefixType());
  if (!variant.ok()) {
    return variant.status();
  }

  util::StatusOr<HpkeParameters> parameters = ToParameters(
      serialization.GetOutputPrefixType(), proto_key.public_key().params());
  if (!parameters.ok()) {
    return parameters.status();
  }

  util::StatusOr<HpkePublicKey> public_key = HpkePublicKey::Create(
      *parameters, proto_key.public_key().public_key(),
      serialization.IdRequirement(), GetPartialKeyAccess());
  if (!public_key.ok()) {
    return public_key.status();
  }

  return HpkePrivateKey::Create(*public_key,
                                RestrictedData(proto_key.private_key(), *token),
                                GetPartialKeyAccess());
}

util::StatusOr<internal::ProtoParametersSerialization> SerializeParameters(
    const HpkeParameters& parameters) {
  util::StatusOr<OutputPrefixType> output_prefix_type =
      ToOutputPrefixType(parameters.GetVariant());
  if (!output_prefix_type.ok()) {
    return output_prefix_type.status();
  }

  util::StatusOr<HpkeParams> params = FromParameters(parameters);
  if (!params.ok()) {
    return params.status();
  }
  HpkeKeyFormat proto_key_format;
  *proto_key_format.mutable_params() = *params;

  return internal::ProtoParametersSerialization::Create(
      kPrivateTypeUrl, *output_prefix_type,
      proto_key_format.SerializeAsString());
}

util::StatusOr<internal::ProtoKeySerialization> SerializePublicKey(
    const HpkePublicKey& key, absl::optional<SecretKeyAccessToken> token) {
  util::StatusOr<HpkeParams> params = FromParameters(key.GetParameters());
  if (!params.ok()) {
    return params.status();
  }

  google::crypto::tink::HpkePublicKey proto_key;
  proto_key.set_version(0);
  *proto_key.mutable_params() = *params;
  // OSS proto library complains if input is not converted to a string.
  proto_key.set_public_key(
      std::string(key.GetPublicKeyBytes(GetPartialKeyAccess())));

  util::StatusOr<OutputPrefixType> output_prefix_type =
      ToOutputPrefixType(key.GetParameters().GetVariant());
  if (!output_prefix_type.ok()) {
    return output_prefix_type.status();
  }

  RestrictedData restricted_output = RestrictedData(
      proto_key.SerializeAsString(), InsecureSecretKeyAccess::Get());
  return internal::ProtoKeySerialization::Create(
      kPublicTypeUrl, restricted_output, KeyData::ASYMMETRIC_PUBLIC,
      *output_prefix_type, key.GetIdRequirement());
}

util::StatusOr<internal::ProtoKeySerialization> SerializePrivateKey(
    const HpkePrivateKey& key, absl::optional<SecretKeyAccessToken> token) {
  util::StatusOr<RestrictedData> restricted_input =
      key.GetPrivateKeyBytes(GetPartialKeyAccess());
  if (!restricted_input.ok()) {
    return restricted_input.status();
  }
  if (!token.has_value()) {
    return util::Status(absl::StatusCode::kPermissionDenied,
                        "SecretKeyAccess is required");
  }

  util::StatusOr<HpkeParams> params =
      FromParameters(key.GetPublicKey().GetParameters());
  if (!params.ok()) {
    return params.status();
  }

  google::crypto::tink::HpkePublicKey proto_public_key;
  proto_public_key.set_version(0);
  *proto_public_key.mutable_params() = *params;
  // OSS proto library complains if input is not converted to a string.
  proto_public_key.set_public_key(
      std::string(key.GetPublicKey().GetPublicKeyBytes(GetPartialKeyAccess())));

  google::crypto::tink::HpkePrivateKey proto_private_key;
  proto_private_key.set_version(0);
  *proto_private_key.mutable_public_key() = proto_public_key;
  // OSS proto library complains if input is not converted to a string.
  proto_private_key.set_private_key(
      std::string(restricted_input->GetSecret(*token)));

  util::StatusOr<OutputPrefixType> output_prefix_type =
      ToOutputPrefixType(key.GetPublicKey().GetParameters().GetVariant());
  if (!output_prefix_type.ok()) {
    return output_prefix_type.status();
  }

  RestrictedData restricted_output =
      RestrictedData(proto_private_key.SerializeAsString(), *token);
  return internal::ProtoKeySerialization::Create(
      kPrivateTypeUrl, restricted_output, KeyData::ASYMMETRIC_PRIVATE,
      *output_prefix_type, key.GetIdRequirement());
}

HpkeProtoParametersParserImpl* HpkeProtoParametersParser() {
  static auto* parser =
      new HpkeProtoParametersParserImpl(kPrivateTypeUrl, ParseParameters);
  return parser;
}

HpkeProtoParametersSerializerImpl* HpkeProtoParametersSerializer() {
  static auto* serializer = new HpkeProtoParametersSerializerImpl(
      kPrivateTypeUrl, SerializeParameters);
  return serializer;
}

HpkeProtoPublicKeyParserImpl* HpkeProtoPublicKeyParser() {
  static auto* parser =
      new HpkeProtoPublicKeyParserImpl(kPublicTypeUrl, ParsePublicKey);
  return parser;
}

HpkeProtoPublicKeySerializerImpl* HpkeProtoPublicKeySerializer() {
  static auto* serializer =
      new HpkeProtoPublicKeySerializerImpl(SerializePublicKey);
  return serializer;
}

HpkeProtoPrivateKeyParserImpl* HpkeProtoPrivateKeyParser() {
  static auto* parser =
      new HpkeProtoPrivateKeyParserImpl(kPrivateTypeUrl, ParsePrivateKey);
  return parser;
}

HpkeProtoPrivateKeySerializerImpl* HpkeProtoPrivateKeySerializer() {
  static auto* serializer =
      new HpkeProtoPrivateKeySerializerImpl(SerializePrivateKey);
  return serializer;
}

}  // namespace

util::Status RegisterHpkeProtoSerialization() {
  util::Status status =
      internal::MutableSerializationRegistry::GlobalInstance()
          .RegisterParametersParser(HpkeProtoParametersParser());
  if (!status.ok()) {
    return status;
  }

  status = internal::MutableSerializationRegistry::GlobalInstance()
               .RegisterParametersSerializer(HpkeProtoParametersSerializer());
  if (!status.ok()) {
    return status;
  }

  status = internal::MutableSerializationRegistry::GlobalInstance()
               .RegisterKeyParser(HpkeProtoPublicKeyParser());
  if (!status.ok()) {
    return status;
  }

  status = internal::MutableSerializationRegistry::GlobalInstance()
               .RegisterKeySerializer(HpkeProtoPublicKeySerializer());
  if (!status.ok()) {
    return status;
  }

  status = internal::MutableSerializationRegistry::GlobalInstance()
               .RegisterKeyParser(HpkeProtoPrivateKeyParser());
  if (!status.ok()) {
    return status;
  }

  return internal::MutableSerializationRegistry::GlobalInstance()
      .RegisterKeySerializer(HpkeProtoPrivateKeySerializer());
}

}  // namespace tink
}  // namespace crypto