net/quic/crypto/quic_decrypter.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef NET_QUIC_CRYPTO_QUIC_DECRYPTER_H_
   6 #define NET_QUIC_CRYPTO_QUIC_DECRYPTER_H_
   7
   8 #include "net/base/net_export.h"
   9 #include "net/quic/quic_protocol.h"
  10
  11 namespace net {
  12
  13 class NET_EXPORT_PRIVATE QuicDecrypter {
  14  public:
  15   virtual ~QuicDecrypter() {}
  16
  17   static QuicDecrypter* Create(QuicTag algorithm);
  18
  19   // Sets the encryption key. Returns true on success, false on failure.
  20   //
  21   // NOTE: The key is the client_write_key or server_write_key derived from
  22   // the master secret.
  23   virtual bool SetKey(base::StringPiece key) = 0;
  24
  25   // Sets the fixed initial bytes of the nonce. Returns true on success,
  26   // false on failure.
  27   //
  28   // NOTE: The nonce prefix is the client_write_iv or server_write_iv
  29   // derived from the master secret. A 64-bit packet sequence number will
  30   // be appended to form the nonce.
  31   //
  32   //                          <------------ 64 bits ----------->
  33   //   +---------------------+----------------------------------+
  34   //   |    Fixed prefix     |      Packet sequence number      |
  35   //   +---------------------+----------------------------------+
  36   //                          Nonce format
  37   //
  38   // The security of the nonce format requires that QUIC never reuse a
  39   // packet sequence number, even when retransmitting a lost packet.
  40   virtual bool SetNoncePrefix(base::StringPiece nonce_prefix) = 0;
  41
  42   // Decrypt authenticates |associated_data| and |ciphertext| and then decrypts
  43   // |ciphertext| into |output|, using |nonce|. |nonce| must be 8 bytes longer
  44   // than the nonce prefix length returned by GetNoncePrefixSize() (of the
  45   // encrypter). |output| must be as long as |ciphertext| on entry and, on
  46   // successful return, the true length of the plaintext will be written to
  47   // |*output_length|.
  48   virtual bool Decrypt(base::StringPiece nonce,
  49                        base::StringPiece associated_data,
  50                        base::StringPiece ciphertext,
  51                        unsigned char* output,
  52                        size_t* output_length) = 0;
  53
  54   // Returns a newly created QuicData object containing the decrypted
  55   // |ciphertext| or NULL if there is an error. |sequence_number| is
  56   // appended to the |nonce_prefix| value provided in SetNoncePrefix()
  57   // to form the nonce.
  58   // TODO(wtc): add a way for DecryptPacket to report decryption failure due
  59   // to non-authentic inputs, as opposed to other reasons for failure.
  60   virtual QuicData* DecryptPacket(QuicPacketSequenceNumber sequence_number,
  61                                   base::StringPiece associated_data,
  62                                   base::StringPiece ciphertext) = 0;
  63
  64   // For use by unit tests only.
  65   virtual base::StringPiece GetKey() const = 0;
  66   virtual base::StringPiece GetNoncePrefix() const = 0;
  67 };
  68
  69 }  // namespace net
  70
  71 #endif  // NET_QUIC_CRYPTO_QUIC_DECRYPTER_H_