crypto/encryptor.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 CRYPTO_ENCRYPTOR_H_
   6 #define CRYPTO_ENCRYPTOR_H_
   7
   8 #include <string>
   9
  10 #include "base/basictypes.h"
  11 #include "base/memory/scoped_ptr.h"
  12 #include "base/strings/string_piece.h"
  13 #include "build/build_config.h"
  14 #include "crypto/crypto_export.h"
  15
  16 #if !defined(USE_OPENSSL)
  17 #include "crypto/scoped_nss_types.h"
  18 #endif
  19
  20 namespace crypto {
  21
  22 class SymmetricKey;
  23
  24 class CRYPTO_EXPORT Encryptor {
  25  public:
  26   enum Mode {
  27     CBC,
  28     CTR,
  29   };
  30
  31   // This class implements a 128-bits counter to be used in AES-CTR encryption.
  32   // Only 128-bits counter is supported in this class.
  33   class CRYPTO_EXPORT Counter {
  34    public:
  35     explicit Counter(const base::StringPiece& counter);
  36     ~Counter();
  37
  38     // Increment the counter value.
  39     bool Increment();
  40
  41     // Write the content of the counter to |buf|. |buf| should have enough
  42     // space for |GetLengthInBytes()|.
  43     void Write(void* buf);
  44
  45     // Return the length of this counter.
  46     size_t GetLengthInBytes() const;
  47
  48    private:
  49     union {
  50       uint32 components32[4];
  51       uint64 components64[2];
  52     } counter_;
  53   };
  54
  55   Encryptor();
  56   virtual ~Encryptor();
  57
  58   // Initializes the encryptor using |key| and |iv|. Returns false if either the
  59   // key or the initialization vector cannot be used.
  60   //
  61   // If |mode| is CBC, |iv| must not be empty; if it is CTR, then |iv| must be
  62   // empty.
  63   bool Init(SymmetricKey* key, Mode mode, const base::StringPiece& iv);
  64
  65   // Encrypts |plaintext| into |ciphertext|.  |plaintext| may only be empty if
  66   // the mode is CBC.
  67   bool Encrypt(const base::StringPiece& plaintext, std::string* ciphertext);
  68
  69   // Decrypts |ciphertext| into |plaintext|.  |ciphertext| must not be empty.
  70   //
  71   // WARNING: In CBC mode, Decrypt() returns false if it detects the padding
  72   // in the decrypted plaintext is wrong. Padding errors can result from
  73   // tampered ciphertext or a wrong decryption key. But successful decryption
  74   // does not imply the authenticity of the data. The caller of Decrypt()
  75   // must either authenticate the ciphertext before decrypting it, or take
  76   // care to not report decryption failure. Otherwise it could inadvertently
  77   // be used as a padding oracle to attack the cryptosystem.
  78   bool Decrypt(const base::StringPiece& ciphertext, std::string* plaintext);
  79
  80   // Sets the counter value when in CTR mode. Currently only 128-bits
  81   // counter value is supported.
  82   //
  83   // Returns true only if update was successful.
  84   bool SetCounter(const base::StringPiece& counter);
  85
  86   // TODO(albertb): Support streaming encryption.
  87
  88  private:
  89   // Generates a mask using |counter_| to be used for encryption in CTR mode.
  90   // Resulting mask will be written to |mask| with |mask_len| bytes.
  91   //
  92   // Make sure there's enough space in mask when calling this method.
  93   // Reserve at least |plaintext_len| + 16 bytes for |mask|.
  94   //
  95   // The generated mask will always have at least |plaintext_len| bytes and
  96   // will be a multiple of the counter length.
  97   //
  98   // This method is used only in CTR mode.
  99   //
 100   // Returns false if this call failed.
 101   bool GenerateCounterMask(size_t plaintext_len,
 102                            uint8* mask,
 103                            size_t* mask_len);
 104
 105   // Mask the |plaintext| message using |mask|. The output will be written to
 106   // |ciphertext|. |ciphertext| must have at least |plaintext_len| bytes.
 107   void MaskMessage(const void* plaintext,
 108                    size_t plaintext_len,
 109                    const void* mask,
 110                    void* ciphertext) const;
 111
 112   SymmetricKey* key_;
 113   Mode mode_;
 114   scoped_ptr<Counter> counter_;
 115
 116 #if defined(USE_OPENSSL)
 117   bool Crypt(bool do_encrypt,  // Pass true to encrypt, false to decrypt.
 118              const base::StringPiece& input,
 119              std::string* output);
 120   bool CryptCTR(bool do_encrypt,
 121                 const base::StringPiece& input,
 122                 std::string* output);
 123   std::string iv_;
 124 #else
 125   bool Crypt(PK11Context* context,
 126              const base::StringPiece& input,
 127              std::string* output);
 128   bool CryptCTR(PK11Context* context,
 129                 const base::StringPiece& input,
 130                 std::string* output);
 131   ScopedSECItem param_;
 132 #endif
 133 };
 134
 135 }  // namespace crypto
 136
 137 #endif  // CRYPTO_ENCRYPTOR_H_