aes_encryptor.h

// Copyright 2014 Google LLC. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd
//
// AES Encryptor implementation using mbedtls.
 
#ifndef PACKAGER_MEDIA_BASE_AES_ENCRYPTOR_H_
#define PACKAGER_MEDIA_BASE_AES_ENCRYPTOR_H_
 
#include <cstdint>
#include <string>
#include <vector>
 
#include <packager/macros/classes.h>
#include <packager/media/base/aes_cryptor.h>
 
namespace shaka {
namespace media {
 
// Class which implements AES-CTR counter-mode encryption.
class AesCtrEncryptor : public AesCryptor {
 public:
  AesCtrEncryptor();
  ~AesCtrEncryptor() override;
 
  uint32_t block_offset() const { return block_offset_; }
 
  bool InitializeWithIv(const std::vector<uint8_t>& key,
                        const std::vector<uint8_t>& iv) override;
 
 private:
  bool CryptInternal(const uint8_t* plaintext,
                     size_t plaintext_size,
                     uint8_t* ciphertext,
                     size_t* ciphertext_size) override;
  void SetIvInternal() override;
 
  // Current block offset.
  uint32_t block_offset_;
  // Current AES-CTR counter.
  std::vector<uint8_t> counter_;
  // Encrypted counter.
  std::vector<uint8_t> encrypted_counter_;
 
  DISALLOW_COPY_AND_ASSIGN(AesCtrEncryptor);
};
 
enum CbcPaddingScheme {
  // Residual block is left unencrypted.
  kNoPadding,
  // Residual block is padded with pkcs5 and encrypted.
  kPkcs5Padding,
  // Residual block and the next-to-last block are encrypted using ciphertext
  // stealing method.
  kCtsPadding,
};
 
// Class which implements AES-CBC (Cipher block chaining) encryption.
class AesCbcEncryptor : public AesCryptor {
 public:
  explicit AesCbcEncryptor(CbcPaddingScheme padding_scheme);
 
  AesCbcEncryptor(CbcPaddingScheme padding_scheme,
                  ConstantIvFlag constant_iv_flag);
 
  ~AesCbcEncryptor() override;
 
  bool InitializeWithIv(const std::vector<uint8_t>& key,
                        const std::vector<uint8_t>& iv) override;
 
  size_t RequiredOutputSize(size_t plaintext_size) override;
 
 private:
  bool CryptInternal(const uint8_t* plaintext,
                     size_t plaintext_size,
                     uint8_t* ciphertext,
                     size_t* ciphertext_size) override;
  void SetIvInternal() override;
  size_t NumPaddingBytes(size_t size) const override;
 
  void CbcEncryptBlocks(const uint8_t* plaintext,
                        size_t plaintext_size,
                        uint8_t* ciphertext,
                        uint8_t* iv);
 
  const CbcPaddingScheme padding_scheme_;
  // 16-byte internal iv for crypto operations.
  std::vector<uint8_t> internal_iv_;
 
  DISALLOW_COPY_AND_ASSIGN(AesCbcEncryptor);
};
 
}  // namespace media
}  // namespace shaka
 
#endif  // PACKAGER_MEDIA_BASE_AES_ENCRYPTOR_H_