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Add Legacy Envelope KMS AEAD parameters.
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| Original file line number | Diff line number | Diff line change |
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| // Copyright 2024 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. | ||
| // | ||
| //////////////////////////////////////////////////////////////////////////////// | ||
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| #include "tink/aead/legacy_kms_envelope_aead_parameters.h" | ||
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| #include <memory> | ||
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| #include "absl/memory/memory.h" | ||
| #include "absl/status/status.h" | ||
| #include "absl/strings/string_view.h" | ||
| #include "tink/aead/aead_parameters.h" | ||
| #include "tink/aead/aes_ctr_hmac_aead_parameters.h" | ||
| #include "tink/aead/aes_eax_parameters.h" | ||
| #include "tink/aead/aes_gcm_parameters.h" | ||
| #include "tink/aead/aes_gcm_siv_parameters.h" | ||
| #include "tink/aead/xchacha20_poly1305_parameters.h" | ||
| #include "tink/parameters.h" | ||
| #include "tink/util/status.h" | ||
| #include "tink/util/statusor.h" | ||
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| namespace crypto { | ||
| namespace tink { | ||
| namespace { | ||
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| util::Status ValidateDekParsingStrategy( | ||
| LegacyKmsEnvelopeAeadParameters::DekParsingStrategy dek_parsing_strategy, | ||
| const AeadParameters& dek_parameters) { | ||
| if (dek_parsing_strategy == LegacyKmsEnvelopeAeadParameters:: | ||
| DekParsingStrategy::kAssumeAesCtrHmac && | ||
| typeid(dek_parameters) == typeid(AesCtrHmacAeadParameters)) { | ||
| return util::OkStatus(); | ||
| } | ||
| if (dek_parsing_strategy == | ||
| LegacyKmsEnvelopeAeadParameters::DekParsingStrategy::kAssumeAesEax && | ||
| typeid(dek_parameters) == typeid(AesEaxParameters)) { | ||
| return util::OkStatus(); | ||
| } | ||
| if (dek_parsing_strategy == | ||
| LegacyKmsEnvelopeAeadParameters::DekParsingStrategy::kAssumeAesGcm && | ||
| typeid(dek_parameters) == typeid(AesGcmParameters)) { | ||
| return util::OkStatus(); | ||
| } | ||
| if (dek_parsing_strategy == LegacyKmsEnvelopeAeadParameters:: | ||
| DekParsingStrategy::kAssumeAesGcmSiv && | ||
| typeid(dek_parameters) == typeid(AesGcmSivParameters)) { | ||
| return util::OkStatus(); | ||
| } | ||
| if (dek_parsing_strategy == | ||
| LegacyKmsEnvelopeAeadParameters::DekParsingStrategy:: | ||
| kAssumeXChaCha20Poly1305 && | ||
| typeid(dek_parameters) == typeid(XChaCha20Poly1305Parameters)) { | ||
| return util::OkStatus(); | ||
| } | ||
| return util::Status(absl::StatusCode::kInvalidArgument, | ||
| "Cannot create legacy KMS Envelope AEAD parameters with " | ||
| "mismatching parsing strategy and DEK parameters type."); | ||
| } | ||
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| } // namespace | ||
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| util::StatusOr<LegacyKmsEnvelopeAeadParameters> | ||
| LegacyKmsEnvelopeAeadParameters::Create(absl::string_view key_uri, | ||
| Variant variant, | ||
| DekParsingStrategy dek_parsing_strategy, | ||
| const AeadParameters& dek_parameters) { | ||
| if (variant != Variant::kTink && variant != Variant::kNoPrefix) { | ||
| return util::Status(absl::StatusCode::kInvalidArgument, | ||
| "Cannot create legacy KMS Envelope AEAD parameters " | ||
| "with unknown variant."); | ||
| } | ||
| if (dek_parameters.HasIdRequirement()) { | ||
| return util::Status(absl::StatusCode::kInvalidArgument, | ||
| "DEK parameters must not have an ID requirement."); | ||
| } | ||
| util::Status status = | ||
| ValidateDekParsingStrategy(dek_parsing_strategy, dek_parameters); | ||
| if (!status.ok()) { | ||
| return status; | ||
| } | ||
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| std::unique_ptr<Parameters> cloned_dek_parameters = dek_parameters.Clone(); | ||
| const AeadParameters* dek_parameters_ptr = | ||
| dynamic_cast<const AeadParameters*>(cloned_dek_parameters.get()); | ||
| if (dek_parameters_ptr == nullptr) { | ||
| return absl::Status(absl::StatusCode::kInvalidArgument, | ||
| "DEK parameters cannot be set to non-AEAD parameters."); | ||
| } | ||
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| return LegacyKmsEnvelopeAeadParameters( | ||
| key_uri, variant, dek_parsing_strategy, | ||
| absl::WrapUnique(dynamic_cast<const AeadParameters*>( | ||
| cloned_dek_parameters.release()))); | ||
| } | ||
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| bool LegacyKmsEnvelopeAeadParameters::operator==( | ||
| const Parameters& other) const { | ||
| const LegacyKmsEnvelopeAeadParameters* that = | ||
| dynamic_cast<const LegacyKmsEnvelopeAeadParameters*>(&other); | ||
| if (that == nullptr) { | ||
| return false; | ||
| } | ||
| return key_uri_ == that->key_uri_ && variant_ == that->variant_ && | ||
| dek_parsing_strategy_ == that->dek_parsing_strategy_ && | ||
| *dek_parameters_ == *that->dek_parameters_; | ||
| } | ||
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| } // namespace tink | ||
| } // namespace crypto |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,149 @@ | ||
| // Copyright 2024 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. | ||
| // | ||
| //////////////////////////////////////////////////////////////////////////////// | ||
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| #ifndef TINK_AEAD_LEGACY_KMS_ENVELOPE_AEAD_PARAMETERS_H_ | ||
| #define TINK_AEAD_LEGACY_KMS_ENVELOPE_AEAD_PARAMETERS_H_ | ||
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| #include <memory> | ||
| #include <string> | ||
| #include <utility> | ||
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| #include "absl/strings/string_view.h" | ||
| #include "tink/aead/aead_parameters.h" | ||
| #include "tink/parameters.h" | ||
| #include "tink/util/statusor.h" | ||
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| namespace crypto { | ||
| namespace tink { | ||
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| // Describes the parameters of a LegacyKmsEnvelopeAeadKey. | ||
| // | ||
| // Usage of this key type is not recommended. Instead, we recommend to | ||
| // implement the idea of this class manually, i.e., create a remote Aead object | ||
| // for your KMS with an appropriate Tink extension (typically using a subclass | ||
| // of `KmsClient`), and then create an envelope AEAD with | ||
| // `KmsEnvelopeAead::New`. | ||
| // | ||
| // Known Issues: | ||
| // 1. Global registration: | ||
| // If a user uses a `LegacyKmsEnvelopeAeadKey`, when | ||
| // the corresponding `Aead` is created, Tink looks up the `KmsClient` in a | ||
| // global registry. This registry needs to store all the credentials and all | ||
| // the information. This is inappropriate in many situations. | ||
| // | ||
| // 2. Ciphertext format: | ||
| // The ciphertext format does not encode the key type of the key used. This | ||
| // can lead to unexpected results if a user changes the `dekParameters` or | ||
| // the `dekParsingStrategy` for the same remote key. In more details, the | ||
| // ciphertext contains a Tink key proto of newly generated key, but not the | ||
| // type URL. This means that if a user reuses the same remote Key with a | ||
| // different key type, it will be parsed with the wrong one. | ||
| // | ||
| // Also, Tink does not compare the parameters of the parsed key with the | ||
| // parameters specified in 'dekParameters`. For example, if the | ||
| // `dekParameters` is specified as AES_128_GCM in one binary, and AES_256_GCM | ||
| // in another binary, communication between the binaries succeeds in both | ||
| // directions. | ||
| // | ||
| // 3. Ciphertext malleability: | ||
| // Some KMS have malleable ciphertexts. This means that the Aeads | ||
| // corresponding to these keys may be malleable. See | ||
| // https://developers.google.com/tink/issues/envelope-aead-malleability | ||
| class LegacyKmsEnvelopeAeadParameters : public AeadParameters { | ||
| public: | ||
| // Description of the output prefix prepended to the ciphertext. | ||
| enum class Variant : int { | ||
| // Prepends '0x01<big endian key id>' to the ciphertext. | ||
| kTink = 1, | ||
| // Does not prepend any prefix (i.e., keys must have no ID requirement). | ||
| kNoPrefix = 2, | ||
| // Added to guard from failures that may be caused by future expansions. | ||
| kDoNotUseInsteadUseDefaultWhenWritingSwitchStatements = 20, | ||
| }; | ||
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| // Specifies how the DEKs in received ciphertexts are parsed. | ||
| enum class DekParsingStrategy : int { | ||
| // When parsing, assume that the ciphertext was encrypted with AES-GCM. | ||
| kAssumeAesGcm = 1, | ||
| // When parsing, assume that the ciphertext was encrypted with | ||
| // XChaCha20-Poly1305. | ||
| kAssumeXChaCha20Poly1305 = 2, | ||
| // When parsing, assume that the ciphertext was encrypted with AES-GCM-SIV. | ||
| kAssumeAesGcmSiv = 3, | ||
| // When parsing, assume that the ciphertext was encrypted with AES-CTR-HMAC. | ||
| kAssumeAesCtrHmac = 4, | ||
| // When parsing, assume that the ciphertext was encrypted with AES-EAX. | ||
| kAssumeAesEax = 5, | ||
| // Added to guard from failures that may be caused by future expansions. | ||
| kDoNotUseInsteadUseDefaultWhenWritingSwitchStatements = 20, | ||
| }; | ||
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| // Copyable and movable. | ||
| LegacyKmsEnvelopeAeadParameters( | ||
| const LegacyKmsEnvelopeAeadParameters& other) = default; | ||
| LegacyKmsEnvelopeAeadParameters& operator=( | ||
| const LegacyKmsEnvelopeAeadParameters& other) = default; | ||
| LegacyKmsEnvelopeAeadParameters(LegacyKmsEnvelopeAeadParameters&& other) = | ||
| default; | ||
| LegacyKmsEnvelopeAeadParameters& operator=( | ||
| LegacyKmsEnvelopeAeadParameters&& other) = default; | ||
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| static util::StatusOr<LegacyKmsEnvelopeAeadParameters> Create( | ||
| absl::string_view key_uri, Variant variant, | ||
| DekParsingStrategy dek_parsing_strategy, | ||
| const AeadParameters& dek_parameters); | ||
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| const std::string& GetKeyUri() const { return key_uri_; } | ||
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| Variant GetVariant() const { return variant_; } | ||
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| // Returns strategy used when parsing encrypted keys. | ||
| DekParsingStrategy GetDekParsingStrategy() const { | ||
| return dek_parsing_strategy_; | ||
| } | ||
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| const AeadParameters& GetDekParameters() const { return *dek_parameters_; } | ||
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| bool HasIdRequirement() const override { | ||
| return variant_ != Variant::kNoPrefix; | ||
| } | ||
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| bool operator==(const Parameters& other) const override; | ||
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| std::unique_ptr<Parameters> Clone() const override { | ||
| return std::make_unique<LegacyKmsEnvelopeAeadParameters>(*this); | ||
| } | ||
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| private: | ||
| explicit LegacyKmsEnvelopeAeadParameters( | ||
| absl::string_view key_uri, Variant variant, | ||
| DekParsingStrategy dek_parsing_strategy, | ||
| std::unique_ptr<const AeadParameters> dek_parameters) | ||
| : key_uri_(key_uri), | ||
| variant_(variant), | ||
| dek_parsing_strategy_(dek_parsing_strategy), | ||
| dek_parameters_(std::move(dek_parameters)) {} | ||
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| std::string key_uri_; | ||
| Variant variant_; | ||
| DekParsingStrategy dek_parsing_strategy_; | ||
| std::shared_ptr<const AeadParameters> dek_parameters_; | ||
| }; | ||
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| } // namespace tink | ||
| } // namespace crypto | ||
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| #endif // TINK_AEAD_LEGACY_KMS_ENVELOPE_AEAD_PARAMETERS_H_ |
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