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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.
//
///////////////////////////////////////////////////////////////////////////////
#ifndef TINK_STREAMING_AEAD_H_
#define TINK_STREAMING_AEAD_H_
#include <memory>
#include "absl/strings/string_view.h"
#include "tink/input_stream.h"
#include "tink/output_stream.h"
#include "tink/random_access_stream.h"
#include "tink/util/statusor.h"
namespace crypto {
namespace tink {
// An interface for streaming authenticated encryption with associated data.
// Streaming encryption is typically used for encrypting large plaintexts such
// as large files. Tink may eventually contain multiple interfaces for
// streaming encryption depending on the supported properties. This interface
// supports a streaming interface for symmetric encryption with
// authentication. The underlying encryption modes are selected so that partial
// plaintext can be obtained fast by decrypting and authenticating just a part
// of the ciphertext.
class StreamingAead {
public:
// Returns a wrapper around 'ciphertext_destination', such that any bytes
// written via the wrapper are AEAD-encrypted using 'associated_data' as
// associated authenticated data. The associated data is not included in the
// ciphertext and has to be passed in as parameter for decryption.
// ByteCount() of the wrapper returns the number of written plaintext bytes.
// Closing the wrapper results in closing of the wrapped stream.
virtual crypto::tink::util::StatusOr<
std::unique_ptr<crypto::tink::OutputStream>>
NewEncryptingStream(
std::unique_ptr<crypto::tink::OutputStream> ciphertext_destination,
absl::string_view associated_data) const = 0;
// Returns a wrapper around 'ciphertext_source', such that reading
// via the wrapper leads to AEAD-decryption of the underlying ciphertext,
// using 'associated_data' as associated authenticated data, and the
// read bytes are bytes of the resulting plaintext.
// ByteCount() of the wrapper returns the number of read plaintext bytes.
virtual crypto::tink::util::StatusOr<
std::unique_ptr<crypto::tink::InputStream>>
NewDecryptingStream(
std::unique_ptr<crypto::tink::InputStream> ciphertext_source,
absl::string_view associated_data) const = 0;
// Returns a wrapper around 'ciphertext_source', such that reading
// via the wrapper leads to AEAD-decryption of the underlying ciphertext,
// using 'associated_data' as associated authenticated data, and the
// read bytes are bytes of the resulting plaintext.
// Note that the returned wrapper's size()-method reports size that is
// not checked for integrity. For example, if the ciphertext file has been
// truncated then size() will return a wrong result. Reading the last block
// of the plaintext will verify whether size() is correct.
// Reading through the wrapper is thread safe.
virtual crypto::tink::util::StatusOr<
std::unique_ptr<crypto::tink::RandomAccessStream>>
NewDecryptingRandomAccessStream(
std::unique_ptr<crypto::tink::RandomAccessStream> ciphertext_source,
absl::string_view associated_data) const = 0;
virtual ~StreamingAead() = default;
};
} // namespace tink
} // namespace crypto
#endif // TINK_STREAMING_AEAD_H_
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