net/quic/crypto/crypto_secret_boxer.h

// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef NET_QUIC_CRYPTO_CRYPTO_SECRET_BOXER_H_
#define NET_QUIC_CRYPTO_CRYPTO_SECRET_BOXER_H_

#include <stddef.h>

#include <string>
#include <vector>

#include "base/macros.h"
#include "base/strings/string_piece.h"
#include "base/synchronization/lock.h"
#include "net/base/net_export.h"

namespace net {

class QuicRandom;

// CryptoSecretBoxer encrypts small chunks of plaintext (called 'boxing') and
// then, later, can authenticate+decrypt the resulting boxes. This object is
// thread-safe.
class NET_EXPORT_PRIVATE CryptoSecretBoxer {
 public:
  CryptoSecretBoxer();
  ~CryptoSecretBoxer();

  // GetKeySize returns the number of bytes in a key.
  static size_t GetKeySize();

  // SetKeys sets a std::list of encryption keys. The first key in the std::list
  // will be used by |Box|, but all supplied keys will be tried by |Unbox|, to
  // handle key skew across the fleet. This must be called before |Box| or
  // |Unbox|. Keys must be |GetKeySize()| bytes long.
  void SetKeys(const std::vector<std::string>& keys);

  // Box encrypts |plaintext| using a random nonce generated from |rand| and
  // returns the resulting ciphertext. Since an authenticator and nonce are
  // included, the result will be slightly larger than |plaintext|. The first
  // key in the std::vector supplied to |SetKeys| will be used.
  std::string Box(QuicRandom* rand, base::StringPiece plaintext) const;

  // Unbox takes the result of a previous call to |Box| in |ciphertext| and
  // authenticates+decrypts it. If |ciphertext| cannot be decrypted with any of
  // the supplied keys, the function returns false. Otherwise, |out_storage| is
  // used to store the result and |out| is set to point into |out_storage| and
  // contains the original plaintext.
  bool Unbox(base::StringPiece ciphertext,
             std::string* out_storage,
             base::StringPiece* out) const;

 private:
  mutable base::Lock lock_;
  //  GUARDED_BY(lock_).
  std::vector<std::string> keys_;

  DISALLOW_COPY_AND_ASSIGN(CryptoSecretBoxer);
};

}  // namespace net

#endif  // NET_QUIC_CRYPTO_CRYPTO_SECRET_BOXER_H_