mirror of
https://github.com/kidfromjupiter/nearby.git
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75 lines
2.8 KiB
C++
75 lines
2.8 KiB
C++
// Copyright 2022 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef THIRD_PARTY_NEARBY_PRESENCE_ENCRYPTION_H_
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#define THIRD_PARTY_NEARBY_PRESENCE_ENCRYPTION_H_
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#include <string>
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#include "absl/status/statusor.h"
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#include "absl/strings/string_view.h"
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namespace nearby {
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namespace presence {
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/** Utilities for encryption and decryption of presence advertisements. */
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class Encryption {
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public:
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/**
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* Uses a HMAC based HKDF algorithm to generate and return a
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* new byte array of given length based on input bytes and a zero-initialized
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* salt.
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*/
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static std::string CustomizeBytesSize(absl::string_view bytes, size_t len);
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/** Generates a random byte array of given size. */
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static std::string GenerateRandomByteArray(size_t len);
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/** Generates encrypted metadata key. `metadata_encryption_key` must be 14 or
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* 16 bytes long. `authenticity_key` is the AES key and must be 128 bit (16
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* bytes) long. `salt` must be 2 bytes long.
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*
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* Note, because the salt is ony 16 bit long, the caller should not reuse
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* salts. Reusing salts will expose the encrypted metadata key. The solution
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* in NP is to store all used salts and rotate the autheticity key when we run
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* out of salts.
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*/
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static absl::StatusOr<std::string> GenerateEncryptedMetadataKey(
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absl::string_view metadata_encryption_key,
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absl::string_view authenticity_key, absl::string_view salt) {
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return RunMetadataEncryption(metadata_encryption_key, authenticity_key,
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salt, /*encrypt= */ true);
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}
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/** Generates decrypted metadata key. `encrypted_metadata_key` must be 14 or
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* 16 bytes long. `authenticity_key` is the AES key and must be 128 bit (16
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* bytes) long. `salt` must be 2 bytes long.*/
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static absl::StatusOr<std::string> GenerateDecryptedMetadataKey(
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absl::string_view encrypted_metadata_key,
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absl::string_view authenticity_key, absl::string_view salt) {
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return RunMetadataEncryption(encrypted_metadata_key, authenticity_key, salt,
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/*encrypt= */ false);
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}
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private:
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static absl::StatusOr<std::string> RunMetadataEncryption(
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absl::string_view metadata, absl::string_view key, absl::string_view salt,
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bool encrypt);
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};
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} // namespace presence
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} // namespace nearby
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#endif // THIRD_PARTY_NEARBY_PRESENCE_ENCRYPTION_H_
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