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// Copyright 2018 Google Inc.
//
// 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/subtle/aes_gcm_siv_boringssl.h"
#include <cstdint>
#include <memory>
#include <string>
#include <utility>
#include <vector>
#include "absl/memory/memory.h"
#include "absl/status/status.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/string_view.h"
#include "absl/types/span.h"
#include "tink/aead/internal/ssl_aead.h"
#include "tink/subtle/random.h"
#include "tink/subtle/subtle_util.h"
#include "tink/util/status.h"
namespace crypto {
namespace tink {
namespace subtle {
constexpr int kIvSizeInBytes = 12;
constexpr int kTagSizeInBytes = 16;
util::StatusOr<std::unique_ptr<Aead>> AesGcmSivBoringSsl::New(
const util::SecretData& key) {
auto status = internal::CheckFipsCompatibility<AesGcmSivBoringSsl>();
if (!status.ok()) {
return status;
}
util::StatusOr<std::unique_ptr<internal::SslOneShotAead>> aead =
internal::CreateAesGcmSivOneShotCrypter(key);
if (!aead.ok()) {
return aead.status();
}
return {absl::WrapUnique(new AesGcmSivBoringSsl(*std::move(aead)))};
}
util::StatusOr<std::string> AesGcmSivBoringSsl::Encrypt(
absl::string_view plaintext, absl::string_view associated_data) const {
const int64_t kCiphertextSize =
kIvSizeInBytes + aead_->CiphertextSize(plaintext.size());
std::string ct;
ResizeStringUninitialized(&ct, kCiphertextSize);
util::Status res =
Random::GetRandomBytes(absl::MakeSpan(ct).subspan(0, kIvSizeInBytes));
if (!res.ok()) {
return res;
}
auto nonce = absl::string_view(ct).substr(0, kIvSizeInBytes);
auto ciphertext_and_tag_buffer = absl::MakeSpan(ct).subspan(kIvSizeInBytes);
util::StatusOr<int64_t> written_bytes = aead_->Encrypt(
plaintext, associated_data, nonce, ciphertext_and_tag_buffer);
if (!written_bytes.ok()) {
return written_bytes.status();
}
return ct;
}
util::StatusOr<std::string> AesGcmSivBoringSsl::Decrypt(
absl::string_view ciphertext, absl::string_view associated_data) const {
if (ciphertext.size() < kIvSizeInBytes + kTagSizeInBytes) {
return util::Status(absl::StatusCode::kInvalidArgument,
absl::StrCat("Ciphertext too short; expected at least ",
kIvSizeInBytes + kTagSizeInBytes, " got ",
ciphertext.size()));
}
const int64_t kPlaintextSize =
aead_->PlaintextSize(ciphertext.size() - kIvSizeInBytes);
std::string plaintext;
ResizeStringUninitialized(&plaintext, kPlaintextSize);
auto nonce = ciphertext.substr(0, kIvSizeInBytes);
auto encrypted = ciphertext.substr(kIvSizeInBytes);
util::StatusOr<int64_t> written_bytes = aead_->Decrypt(
encrypted, associated_data, nonce, absl::MakeSpan(plaintext));
if (!written_bytes.ok()) {
return written_bytes.status();
}
return plaintext;
}
} // namespace subtle
} // namespace tink
} // namespace crypto
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