libtpmcrypto/tpm_crypto.h

// Copyright 2018 The Chromium OS 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 LIBTPMCRYPTO_TPM_CRYPTO_H_
#define LIBTPMCRYPTO_TPM_CRYPTO_H_

#include <string>

#include <base/macros.h>
#include <brillo/brillo_export.h>

namespace brillo {
class SecureBlob;
}  // namespace brillo

namespace tpmcrypto {

// AES key size in bytes (256 bits).
constexpr unsigned int kDefaultAesKeySize = 32;

// AES GCM tag size in bytes (128 bits).
constexpr int kGcmDefaultTagSize = 16;

// AES GCM default IV size in bytes (96 bits).
constexpr int kGcmDefaultIVSize = 12;

class BRILLO_EXPORT TpmCrypto {
 public:
  virtual ~TpmCrypto() = default;

  // Seals arbitrary-length |data| to the TPM's PCR0 and returns
  // |encrypted_data| containing the encrypted data. Internally a new random
  // key is generated by the TPM which is used to encrypt the data, that key
  // is sealed by the Storage Root Key in the TPM. Returns true if the
  // encrypted data blob was created successfully.
  virtual bool Encrypt(const brillo::SecureBlob& data,
                       std::string* encrypted_data) = 0;

  // Decrypts data previously sealed to the TPM's PCR0. Internally the key
  // is unsealed using the Storage Root Key in the TPM, and the unsealed key
  // is used to decrypt the content. Decryption also validates that the GCM
  // tag created during encryption matches. Returns true if the data is
  // decrypted and verified successfully.
  virtual bool Decrypt(const std::string& encrypted_data,
                       brillo::SecureBlob* data) = 0;

 protected:
  TpmCrypto() = default;
  TpmCrypto(const TpmCrypto&) = delete;
  TpmCrypto& operator=(const TpmCrypto&) = delete;
};

}  // namespace tpmcrypto

#endif  // LIBTPMCRYPTO_TPM_CRYPTO_H_