EncryptingOutputStream.h

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this file,

 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_dom_quota_EncryptingOutputStream_h

#define mozilla_dom_quota_EncryptingOutputStream_h

// Local includes

#include "EncryptedBlock.h"  // for EncryptedBlock

// Global includes

#include <cstddef>

#include <cstdint>

#include "ErrorList.h"

#include "mozilla/InitializedOnce.h"

#include "mozilla/Maybe.h"

#include "mozilla/NotNull.h"

#include "nsCOMPtr.h"

#include "nsIOutputStream.h"

#include "nsISupports.h"

#include "nsTArray.h"

#include "nscore.h"

class nsIInputStream;

class nsIRandomGenerator;

namespace mozilla::dom::quota {

class EncryptingOutputStreamBase : public nsIOutputStream {

 public:

  NS_DECL_THREADSAFE_ISUPPORTS

  NS_IMETHOD Write(const char* aBuf, uint32_t aCount, uint32_t* _retval) final;

  NS_IMETHOD WriteFrom(nsIInputStream* aFromStream, uint32_t aCount,

                       uint32_t* _retval) final;

  NS_IMETHOD IsNonBlocking(bool* _retval) final;

 protected:

  EncryptingOutputStreamBase(nsCOMPtr<nsIOutputStream> aBaseStream,

                             size_t aBlockSize);

  virtual ~EncryptingOutputStreamBase() = default;

  nsresult WriteAll(const char* aBuf, uint32_t aCount,

                    uint32_t* aBytesWrittenOut);

  InitializedOnce<const NotNull<nsCOMPtr<nsIOutputStream>>> mBaseStream;

  const size_t mBlockSize;

};

// Wraps another nsIOutputStream using the CipherStrategy to encrypt it a

// page-based manner. Essentially, the CipherStrategy is not actually

// necessarily doing encryption, but any transformation to a page requiring some

// fixed-size reserved size per page.

//

// Paired with DecryptingInputStream which can be used to read the data written

// to the underlying stream, using the same (or more generally, a compatible)

// CipherStrategy, when created with the same key (assuming a symmetric cipher

// is being used; in principle, an asymmetric cipher would probably also work).

template <typename CipherStrategy>

class EncryptingOutputStream final : public EncryptingOutputStreamBase {

 public:

  // Construct a new blocking output stream to encrypt data to

  // the given base stream.  The base stream must also be blocking.

  // The encryption block size may optionally be set to a value

  // up to kMaxBlockSize.

  explicit EncryptingOutputStream(nsCOMPtr<nsIOutputStream> aBaseStream,

                                  size_t aBlockSize,

                                  typename CipherStrategy::KeyType aKey);

 private:

  ~EncryptingOutputStream();

  nsresult FlushToBaseStream();

  bool EnsureBuffers();

  CipherStrategy mCipherStrategy;

  // Buffer holding copied plain data.  This must be copied here

  // so that the encryption can be performed on a single flat buffer.

  // XXX This is only necessary if the data written doesn't contain a portion of

  // effective block size at a block boundary.

  nsTArray<uint8_t> mBuffer;

  nsCOMPtr<nsIRandomGenerator> mRandomGenerator;

  // The next byte in the plain data to copy incoming data to.

  size_t mNextByte = 0;

  // Buffer holding the resulting encrypted data.

  using EncryptedBlockType = EncryptedBlock<CipherStrategy::BlockPrefixLength,

                                            CipherStrategy::BasicBlockSize>;

  Maybe<EncryptedBlockType> mEncryptedBlock;

 public:

  NS_IMETHOD Close() override;

  NS_IMETHOD Flush() override;

  NS_IMETHOD StreamStatus() override;

  NS_IMETHOD WriteSegments(nsReadSegmentFun aReader, void* aClosure,

                           uint32_t aCount, uint32_t* _retval) override;

};

}  // namespace mozilla::dom::quota

#endif