1 // Copyright 2021 Google LLC 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 // 15 /////////////////////////////////////////////////////////////////////////////// 16 17 #ifndef TINK_AEAD_INTERNAL_ZERO_COPY_AEAD_H_ 18 #define TINK_AEAD_INTERNAL_ZERO_COPY_AEAD_H_ 19 20 #include <cstdint> 21 22 #include "absl/strings/string_view.h" 23 #include "tink/util/statusor.h" 24 25 namespace crypto { 26 namespace tink { 27 namespace internal { 28 29 /////////////////////////////////////////////////////////////////////////////// 30 // The interface for authenticated encryption with associated data. 31 // Implementations of this interface are secure against adaptive 32 // chosen ciphertext attacks. Encryption with associated data ensures 33 // authenticity and integrity of that data, but not its secrecy. 34 // (see RFC 5116, https://tools.ietf.org/html/rfc5116) 35 // 36 // This implementation expects the user to provide a contiguous block 37 // of memory and writes the Encrypt and Decrypt results in the block. 38 // This requires the user to avoid mutating this block during calls to 39 // Encrypt and Decrypt and aims to reduce the latency associated with 40 // copying strings from one location to another. 41 class ZeroCopyAead { 42 public: 43 virtual ~ZeroCopyAead() = default; 44 45 // Returns the maximum buffer size needed for encryption. The actual 46 // size of the written cypertext may be smaller. 47 virtual int64_t MaxEncryptionSize(int64_t plaintext_size) const = 0; 48 49 // Encrypts `plaintext` with `associated_data` as associated data, 50 // and returns the size of the ciphertext that is written in `buffer`. 51 // `buffer` size must be at least MaxEncryptionSize to guarantee 52 // enough space for encryption. 53 // The ciphertext allows for checking authenticity and integrity 54 // of the associated data, but does not guarantee its secrecy. 55 virtual crypto::tink::util::StatusOr<int64_t> Encrypt( 56 absl::string_view plaintext, absl::string_view associated_data, 57 absl::Span<char> buffer) const = 0; 58 59 // Returns an upper bound on the size of the plaintext based on 60 // `ciphertext_size`. The actual size of the written plaintext may be smaller. 61 // The returned value is always >= 0. 62 virtual int64_t MaxDecryptionSize(int64_t ciphertext_size) const = 0; 63 64 // Decrypts `ciphertext` with `associated_data` as associated data, 65 // and returns the size of the plaintext that is written in `buffer`. 66 // `buffer` size must be at least MaxDecryptionSize to guarantee 67 // enough space for decryption. 68 // If the authentication tag does not validate, `buffer` is zeroed. 69 // The decryption verifies the authenticity and integrity of the 70 // associated data, but there are no guarantees wrt. secrecy of 71 // that data. 72 virtual crypto::tink::util::StatusOr<int64_t> Decrypt( 73 absl::string_view ciphertext, absl::string_view associated_data, 74 absl::Span<char> buffer) const = 0; 75 }; 76 77 } // namespace internal 78 } // namespace tink 79 } // namespace crypto 80 81 #endif // TINK_AEAD_INTERNAL_ZERO_COPY_AEAD_H_ 82