// Copyright (c) 2012 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_QUIC_DECRYPTER_H_
#define NET_QUIC_CRYPTO_QUIC_DECRYPTER_H_

#include "net/base/net_export.h"
#include "net/quic/quic_protocol.h"

namespace net {

class NET_EXPORT_PRIVATE QuicDecrypter {
 public:
  virtual ~QuicDecrypter() {}

  static QuicDecrypter* Create(QuicTag algorithm);

  // Sets the encryption key. Returns true on success, false on failure.
  //
  // NOTE: The key is the client_write_key or server_write_key derived from
  // the master secret.
  virtual bool SetKey(base::StringPiece key) = 0;

  // Sets the fixed initial bytes of the nonce. Returns true on success,
  // false on failure.
  //
  // NOTE: The nonce prefix is the client_write_iv or server_write_iv
  // derived from the master secret. A 64-bit packet sequence number will
  // be appended to form the nonce.
  //
  //                          <------------ 64 bits ----------->
  //   +---------------------+----------------------------------+
  //   |    Fixed prefix     |      Packet sequence number      |
  //   +---------------------+----------------------------------+
  //                          Nonce format
  //
  // The security of the nonce format requires that QUIC never reuse a
  // packet sequence number, even when retransmitting a lost packet.
  virtual bool SetNoncePrefix(base::StringPiece nonce_prefix) = 0;

  // Populates |output| with the decrypted |ciphertext| and populates
  // |output_length| with the length.  Returns 0 if there is an error.
  // |output| size is specified by |max_output_length| and must be
  // at least as large as the ciphertext.  |sequence_number| is
  // appended to the |nonce_prefix| value provided in SetNoncePrefix()
  // to form the nonce.
  // TODO(wtc): add a way for DecryptPacket to report decryption failure due
  // to non-authentic inputs, as opposed to other reasons for failure.
  virtual bool DecryptPacket(QuicPacketSequenceNumber sequence_number,
                             const base::StringPiece& associated_data,
                             const base::StringPiece& ciphertext,
                             char* output,
                             size_t* output_length,
                             size_t max_output_length) = 0;

  // For use by unit tests only.
  virtual base::StringPiece GetKey() const = 0;
  virtual base::StringPiece GetNoncePrefix() const = 0;
};

}  // namespace net

#endif  // NET_QUIC_CRYPTO_QUIC_DECRYPTER_H_