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// Copyright (c) 2012 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.
// Crypto - class for handling the keyset key management functions relating to
// cryptohome. This includes wrapping/unwrapping the vault keyset (and
// supporting functions) and setting/clearing the user keyring for use with
// ecryptfs.
#ifndef CRYPTOHOME_CRYPTO_H_
#define CRYPTOHOME_CRYPTO_H_
#include <stdint.h>
#include <string>
#include <base/files/file_path.h>
#include <base/macros.h>
#include <brillo/secure_blob.h>
#include "cryptohome/tpm.h"
#include "cryptohome/tpm_init.h"
#include "cryptohome/vault_keyset.h"
#include "vault_keyset.pb.h" // NOLINT(build/include)
namespace cryptohome {
class Crypto {
public:
enum CryptoError {
CE_NONE = 0,
CE_TPM_FATAL,
CE_TPM_COMM_ERROR,
CE_TPM_DEFEND_LOCK,
CE_TPM_CRYPTO,
CE_TPM_REBOOT,
CE_SCRYPT_CRYPTO,
CE_OTHER_FATAL,
CE_OTHER_CRYPTO,
CE_NO_PUBLIC_KEY_HASH,
};
// Default constructor
explicit Crypto(Platform* platform);
virtual ~Crypto();
// Initializes Crypto
virtual bool Init(TpmInit* tpm_init);
// Decrypts an encrypted vault keyset. The vault keyset should be the output
// of EncryptVaultKeyset().
//
// Parameters
// encrypted_keyset - The blob containing the encrypted keyset
// vault_key - The passkey used to decrypt the keyset
// crypt_flags (OUT) - Whether the keyset was wrapped by the TPM or scrypt
// error (OUT) - The specific error code on failure
// vault_keyset (OUT) - The decrypted vault keyset on success
virtual bool DecryptVaultKeyset(const SerializedVaultKeyset& serialized,
const brillo::SecureBlob& vault_key,
unsigned int* crypt_flags, CryptoError* error,
VaultKeyset* vault_keyset) const;
// Encrypts the vault keyset with the given passkey
//
// Parameters
// vault_keyset - The VaultKeyset to encrypt
// vault_key - The passkey used to encrypt the keyset
// vault_key_salt - The salt to use for the vault passkey to key conversion
// when encrypting the keyset
// encrypted_keyset - On success, the encrypted vault keyset
virtual bool EncryptVaultKeyset(const VaultKeyset& vault_keyset,
const brillo::SecureBlob& vault_key,
const brillo::SecureBlob& vault_key_salt,
SerializedVaultKeyset* serialized) const;
// Derives keys and other values from User Passkey.
//
// Parameters
// passkey - The User Passkey, from which to derive the keys.
// salt - The salt used when deriving the keys.
// aes_skey (OUT) - The resulting key used at AES step (SKeyAES).
// kdf_skey (OUT) - The resulting key used at KDF step (SKeyKDF).
// vkk_iv (OUT) - The IV used for encrypting/decrypting VK.
virtual bool PasskeyToSKeys(const brillo::Blob& passkey,
const brillo::Blob& salt,
brillo::SecureBlob* aes_skey,
brillo::SecureBlob* kdf_skey,
brillo::SecureBlob* vkk_iv) const;
// Converts the passkey to authorization data for a TPM-backed crypto token.
//
// Parameters
// passkey - The passkey from which to derive the authorization data.
// salt - The salt file used in deriving the authorization data.
// auth_data (OUT) - The token authorization data.
virtual bool PasskeyToTokenAuthData(const brillo::Blob& passkey,
const base::FilePath& salt_file,
brillo::SecureBlob* auth_data) const;
// Gets an existing salt, or creates one if it doesn't exist
//
// Parameters
// path - The path to the salt file
// length - The length of the new salt if it needs to be created
// force - If true, forces creation of a new salt even if the file exists
// salt (OUT) - The salt
virtual bool GetOrCreateSalt(const base::FilePath& path,
size_t length,
bool force,
brillo::SecureBlob* salt) const;
// Converts a null-terminated password to a passkey (ascii-encoded first half
// of the salted SHA1 hash of the password).
//
// Parameters
// password - The password to convert
// salt - The salt used during hashing
// passkey (OUT) - The passkey
static void PasswordToPasskey(const char* password,
const brillo::Blob& salt,
brillo::SecureBlob* passkey);
// Ensures that the TPM is connected
CryptoError EnsureTpm(bool reload_key) const;
// Seals arbitrary-length data to the TPM's PCR0.
// Parameters
// data - Data to encrypt with tpm.
// encrypted_data (OUT) - Encrypted data as a string.
// Returns true if we succeeded in creating the encrypted data blob.
virtual bool EncryptWithTpm(const brillo::SecureBlob& data,
std::string* encrypted_data) const;
// Decrypts data previously sealed to the TPM's PCR0.
// Parameters
// encrypted_data - Encrypted data previously sealed with EncryptWithTPM.
// data (OUT) - Decrypted data as a blob.
// Returns true if we succeeded to decrypt the data blob.
virtual bool DecryptWithTpm(const std::string& encrypted_data,
brillo::SecureBlob* data) const;
// Note the following 4 methods are only to be used if there is a strong
// reason to avoid talking to the TPM e.g. needing to flush some encrypted
// data periodically to disk and you don't want to seal a key each time.
// Otherwise, a user should use Encrypt/DecryptWithTpm.
// Creates a randomly generated aes key and seals it to the TPM's PCR0.
virtual bool CreateSealedKey(brillo::SecureBlob* aes_key,
brillo::SecureBlob* sealed_key) const;
// Encrypts the given data using the aes_key. Sealed key is necessary to
// wrap into the returned data to allow for decryption.
virtual bool EncryptData(const brillo::SecureBlob& data,
const brillo::SecureBlob& aes_key,
const brillo::SecureBlob& sealed_key,
std::string* encrypted_data) const;
// Returns the sealed and unsealed aes_key wrapped in the encrypted_data.
virtual bool UnsealKey(const std::string& encrypted_data,
brillo::SecureBlob* aes_key,
brillo::SecureBlob* sealed_key) const;
// Decrypts encrypted_data using the aes_key.
virtual bool DecryptData(const std::string& encrypted_data,
const brillo::SecureBlob& aes_key,
brillo::SecureBlob* data) const;
// Sets whether or not to use the TPM (must be called before init, depends
// on the presence of a functioning, initialized TPM). The TPM is merely used
// to add a layer of difficulty in a brute-force attack against the user's
// credentials.
void set_use_tpm(bool value) {
use_tpm_ = value;
}
// Sets the TPM implementation
void set_tpm(Tpm* value) {
tpm_ = value;
}
// Gets whether the TPM is set
bool has_tpm() {
return (tpm_ != NULL);
}
// Gets the TPM implementation
const Tpm* get_tpm() {
return tpm_;
}
// Checks if the cryptohome key is loaded in TPM
bool is_cryptohome_key_loaded() const;
// Sets the Platform implementation
// Does NOT take ownership of the pointer.
void set_platform(Platform* value) {
platform_ = value;
}
Platform* platform() {
return platform_;
}
void set_scrypt_max_encrypt_time(double max_time) {
scrypt_max_encrypt_time_ = max_time;
}
static const int64_t kSaltMax;
private:
// Converts a TPM error to a Crypto error
CryptoError TpmErrorToCrypto(Tpm::TpmRetryAction retry_action) const;
bool EncryptTPM(const VaultKeyset& vault_keyset,
const brillo::SecureBlob& key,
const brillo::SecureBlob& salt,
SerializedVaultKeyset* serialized) const;
bool EncryptScrypt(const VaultKeyset& vault_keyset,
const brillo::SecureBlob& key,
SerializedVaultKeyset* serialized) const;
bool DecryptTPM(const SerializedVaultKeyset& serialized,
const brillo::SecureBlob& key,
CryptoError* error,
VaultKeyset* vault_keyset) const;
bool DecryptScrypt(const SerializedVaultKeyset& serialized,
const brillo::SecureBlob& key,
CryptoError* error,
VaultKeyset* keyset) const;
bool IsTPMPubkeyHash(const std::string& hash, CryptoError* error) const;
// If set, the TPM will be used during the encryption of the vault keyset
bool use_tpm_;
// The TPM implementation
Tpm* tpm_;
// Platform abstraction
Platform* platform_;
// The TpmInit object used to reload Cryptohome key
TpmInit* tpm_init_;
double scrypt_max_encrypt_time_;
DISALLOW_COPY_AND_ASSIGN(Crypto);
};
} // namespace cryptohome
#endif // CRYPTOHOME_CRYPTO_H_