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authordrebs <drebs@leap.se>2014-08-01 12:47:43 -0300
committerdrebs <drebs@leap.se>2014-08-08 11:49:02 -0300
commit074848f78bdac78328eb4de7fe72d85830da561d (patch)
tree090868473ee689d72213adc3f469f27107ecaa3e /client/src/leap
parent622708945d51a1e22dde95424a6214e8e67be180 (diff)
Refactor secrets out of main soledad client class.
Diffstat (limited to 'client/src/leap')
-rw-r--r--client/src/leap/soledad/client/__init__.py659
-rw-r--r--client/src/leap/soledad/client/crypto.py21
-rw-r--r--client/src/leap/soledad/client/secrets.py681
3 files changed, 757 insertions, 604 deletions
diff --git a/client/src/leap/soledad/client/__init__.py b/client/src/leap/soledad/client/__init__.py
index 586e3389..0fd6672a 100644
--- a/client/src/leap/soledad/client/__init__.py
+++ b/client/src/leap/soledad/client/__init__.py
@@ -31,9 +31,7 @@ import os
import socket
import ssl
import urlparse
-import hmac
-from hashlib import sha256
try:
import cchardet as chardet
@@ -43,41 +41,20 @@ except ImportError:
from u1db.remote import http_client
from u1db.remote.ssl_match_hostname import match_hostname
-import scrypt
-import simplejson as json
-
from leap.common.config import get_path_prefix
from leap.soledad.common import (
SHARED_DB_NAME,
soledad_assert,
soledad_assert_type
)
-from leap.soledad.common.errors import (
- InvalidTokenError,
- NotLockedError,
- AlreadyLockedError,
- LockTimedOutError,
-)
-from leap.soledad.common.crypto import (
- MacMethods,
- UnknownMacMethod,
- WrongMac,
- MAC_KEY,
- MAC_METHOD_KEY,
-)
from leap.soledad.client.events import (
- SOLEDAD_CREATING_KEYS,
- SOLEDAD_DONE_CREATING_KEYS,
- SOLEDAD_DOWNLOADING_KEYS,
- SOLEDAD_DONE_DOWNLOADING_KEYS,
- SOLEDAD_UPLOADING_KEYS,
- SOLEDAD_DONE_UPLOADING_KEYS,
SOLEDAD_NEW_DATA_TO_SYNC,
SOLEDAD_DONE_DATA_SYNC,
signal,
)
from leap.soledad.common.document import SoledadDocument
from leap.soledad.client.crypto import SoledadCrypto
+from leap.soledad.client.secrets import SoledadSecrets
from leap.soledad.client.shared_db import SoledadSharedDatabase
from leap.soledad.client.sqlcipher import open as sqlcipher_open
from leap.soledad.client.sqlcipher import SQLCipherDatabase
@@ -102,27 +79,6 @@ Soledad client and server.
# Soledad: local encrypted storage and remote encrypted sync.
#
-class NoStorageSecret(Exception):
- """
- Raised when trying to use a storage secret but none is available.
- """
- pass
-
-
-class PassphraseTooShort(Exception):
- """
- Raised when trying to change the passphrase but the provided passphrase is
- too short.
- """
-
-
-class BootstrapSequenceError(Exception):
- """
- Raised when an attempt to generate a secret and store it in a recovery
- documents on server failed.
- """
-
-
class Soledad(object):
"""
Soledad provides encrypted data storage and sync.
@@ -166,57 +122,6 @@ class Soledad(object):
The name of the file where the storage secrets will be stored.
"""
- GENERATED_SECRET_LENGTH = 1024
- """
- The length of the generated secret used to derive keys for symmetric
- encryption for local and remote storage.
- """
-
- LOCAL_STORAGE_SECRET_LENGTH = 512
- """
- The length of the secret used to derive a passphrase for the SQLCipher
- database.
- """
-
- REMOTE_STORAGE_SECRET_LENGTH = \
- GENERATED_SECRET_LENGTH - LOCAL_STORAGE_SECRET_LENGTH
- """
- The length of the secret used to derive an encryption key and a MAC auth
- key for remote storage.
- """
-
- SALT_LENGTH = 64
- """
- The length of the salt used to derive the key for the storage secret
- encryption.
- """
-
- MINIMUM_PASSPHRASE_LENGTH = 6
- """
- The minimum length for a passphrase. The passphrase length is only checked
- when the user changes her passphrase, not when she instantiates Soledad.
- """
-
- IV_SEPARATOR = ":"
- """
- A separator used for storing the encryption initial value prepended to the
- ciphertext.
- """
-
- UUID_KEY = 'uuid'
- STORAGE_SECRETS_KEY = 'storage_secrets'
- SECRET_KEY = 'secret'
- CIPHER_KEY = 'cipher'
- LENGTH_KEY = 'length'
- KDF_KEY = 'kdf'
- KDF_SALT_KEY = 'kdf_salt'
- KDF_LENGTH_KEY = 'kdf_length'
- KDF_SCRYPT = 'scrypt'
- CIPHER_AES256 = 'aes256'
- """
- Keys used to access storage secrets in recovery documents.
- """
-
DEFAULT_PREFIX = os.path.join(get_path_prefix(), 'leap', 'soledad')
"""
Prefix for default values for path.
@@ -266,41 +171,49 @@ class Soledad(object):
storage on server sequence has failed
for some reason.
"""
- # get config params
+ # store config params
self._uuid = uuid
- soledad_assert_type(passphrase, unicode)
self._passphrase = passphrase
- # init crypto variables
- self._secrets = {}
- self._secret_id = secret_id
+ self._secrets_path = secrets_path
+ self._local_db_path = local_db_path
+ self._server_url = server_url
+ # configure SSL certificate
+ global SOLEDAD_CERT
+ SOLEDAD_CERT = cert_file
+ self._set_token(auth_token)
self._defer_encryption = defer_encryption
- self._init_config(secrets_path, local_db_path, server_url)
+ self._init_config()
+ self._init_dirs()
- self._set_token(auth_token)
+ # init crypto variables
self._shared_db_instance = None
- # configure SSL certificate
- global SOLEDAD_CERT
- SOLEDAD_CERT = cert_file
+ self._crypto = SoledadCrypto(self)
+ self._secrets = SoledadSecrets(
+ self._uuid,
+ self._passphrase,
+ self._secrets_path,
+ self._shared_db,
+ self._crypto,
+ secret_id=secret_id)
+
# initiate bootstrap sequence
self._bootstrap() # might raise BootstrapSequenceError()
- def _init_config(self, secrets_path, local_db_path, server_url):
+ def _init_config(self):
"""
Initialize configuration using default values for missing params.
"""
+ soledad_assert_type(self._passphrase, unicode)
# initialize secrets_path
- self._secrets_path = secrets_path
if self._secrets_path is None:
self._secrets_path = os.path.join(
self.DEFAULT_PREFIX, self.STORAGE_SECRETS_FILE_NAME)
# initialize local_db_path
- self._local_db_path = local_db_path
if self._local_db_path is None:
self._local_db_path = os.path.join(
self.DEFAULT_PREFIX, self.LOCAL_DATABASE_FILE_NAME)
# initialize server_url
- self._server_url = server_url
soledad_assert(
self._server_url is not None,
'Missing URL for Soledad server.')
@@ -309,129 +222,18 @@ class Soledad(object):
# initialization/destruction methods
#
- def _get_or_gen_crypto_secrets(self):
- """
- Retrieves or generates the crypto secrets.
-
- Might raise BootstrapSequenceError
- """
- doc = self._get_secrets_from_shared_db()
-
- if doc:
- logger.info(
- 'Found cryptographic secrets in shared recovery '
- 'database.')
- _, mac = self.import_recovery_document(doc.content)
- if mac is False:
- self.put_secrets_in_shared_db()
- self._store_secrets() # save new secrets in local file
- if self._secret_id is None:
- self._set_secret_id(self._secrets.items()[0][0])
- else:
- # STAGE 3 - there are no secrets in server also, so
- # generate a secret and store it in remote db.
- logger.info(
- 'No cryptographic secrets found, creating new '
- ' secrets...')
- self._set_secret_id(self._gen_secret())
- try:
- self._put_secrets_in_shared_db()
- except Exception as ex:
- # storing generated secret in shared db failed for
- # some reason, so we erase the generated secret and
- # raise.
- try:
- os.unlink(self._secrets_path)
- except OSError as e:
- if e.errno != errno.ENOENT: # no such file or directory
- logger.exception(e)
- logger.exception(ex)
- raise BootstrapSequenceError(
- 'Could not store generated secret in the shared '
- 'database, bailing out...')
-
def _bootstrap(self):
"""
Bootstrap local Soledad instance.
- Soledad Client bootstrap is the following sequence of stages:
-
- * stage 0 - local environment setup.
- - directory initialization.
- - crypto submodule initialization
- * stage 1 - local secret loading:
- - if secrets exist locally, load them.
- * stage 2 - remote secret loading:
- - else, if secrets exist in server, download them.
- * stage 3 - secret generation:
- - else, generate a new secret and store in server.
- * stage 4 - database initialization.
-
- This method decides which bootstrap stages have already been performed
- and performs the missing ones in order.
-
:raise BootstrapSequenceError: Raised when the secret generation and
storage on server sequence has failed for some reason.
"""
- # STAGE 0 - local environment setup
- self._init_dirs()
- self._crypto = SoledadCrypto(self)
-
- secrets_problem = None
-
- # STAGE 1 - verify if secrets exist locally
- if not self._has_secret(): # try to load from local storage.
-
- # STAGE 2 - there are no secrets in local storage, so try to fetch
- # encrypted secrets from server.
- logger.info(
- 'Trying to fetch cryptographic secrets from shared recovery '
- 'database...')
-
- # --- start of atomic operation in shared db ---
-
- # obtain lock on shared db
- token = timeout = None
- try:
- token, timeout = self._shared_db.lock()
- except AlreadyLockedError:
- raise BootstrapSequenceError('Database is already locked.')
- except LockTimedOutError:
- raise BootstrapSequenceError('Lock operation timed out.')
-
- try:
- self._get_or_gen_crypto_secrets()
- except Exception as e:
- secrets_problem = e
-
- # release the lock on shared db
- try:
- self._shared_db.unlock(token)
- self._shared_db.close()
- except NotLockedError:
- # for some reason the lock expired. Despite that, secret
- # loading or generation/storage must have been executed
- # successfully, so we pass.
- pass
- except InvalidTokenError:
- # here, our lock has not only expired but also some other
- # client application has obtained a new lock and is currently
- # doing its thing in the shared database. Using the same
- # reasoning as above, we assume everything went smooth and
- # pass.
- pass
- except Exception as e:
- logger.error("Unhandled exception when unlocking shared "
- "database.")
- logger.exception(e)
-
- # --- end of atomic operation in shared db ---
-
- # STAGE 4 - local database initialization
- if secrets_problem is None:
+ try:
+ self._secrets.bootstrap()
self._init_db()
- else:
- raise secrets_problem
+ except:
+ raise
def _init_dirs(self):
"""
@@ -460,27 +262,8 @@ class Soledad(object):
Currently, Soledad uses the default SQLCipher cipher, i.e.
'aes-256-cbc'. We use scrypt to derive a 256-bit encryption key and
uses the 'raw PRAGMA key' format to handle the key to SQLCipher.
-
- The first C{self.REMOTE_STORAGE_SECRET_LENGTH} bytes of the storage
- secret are used for remote storage encryption. We use the next
- C{self.LOCAL_STORAGE_SECRET} bytes to derive a key for local storage.
- From these bytes, the first C{self.SALT_LENGTH} are used as the salt
- and the rest as the password for the scrypt hashing.
- """
- # salt indexes
- salt_start = self.REMOTE_STORAGE_SECRET_LENGTH
- salt_end = salt_start + self.SALT_LENGTH
- # password indexes
- pwd_start = salt_end
- pwd_end = salt_start + self.LOCAL_STORAGE_SECRET_LENGTH
- # calculate the key for local encryption
- secret = self._get_storage_secret()
- key = scrypt.hash(
- secret[pwd_start:pwd_end], # the password
- secret[salt_start:salt_end], # the salt
- buflen=32, # we need a key with 256 bits (32 bytes)
- )
-
+ """
+ key = self._secrets.get_local_storage_key()
self._db = sqlcipher_open(
self._local_db_path,
binascii.b2a_hex(key), # sqlcipher only accepts the hex version
@@ -501,186 +284,6 @@ class Soledad(object):
self._db.stop_sync()
self._db.close()
- #
- # Management of secret for symmetric encryption.
- #
-
- def _get_storage_secret(self):
- """
- Return the storage secret.
-
- Storage secret is encrypted before being stored. This method decrypts
- and returns the stored secret.
-
- :return: The storage secret.
- :rtype: str
- """
- # calculate the encryption key
- key = scrypt.hash(
- self._passphrase_as_string(),
- # the salt is stored base64 encoded
- binascii.a2b_base64(
- self._secrets[self._secret_id][self.KDF_SALT_KEY]),
- buflen=32, # we need a key with 256 bits (32 bytes).
- )
- # recover the initial value and ciphertext
- iv, ciphertext = self._secrets[self._secret_id][self.SECRET_KEY].split(
- self.IV_SEPARATOR, 1)
- ciphertext = binascii.a2b_base64(ciphertext)
- return self._crypto.decrypt_sym(ciphertext, key, iv=iv)
-
- def _set_secret_id(self, secret_id):
- """
- Define the id of the storage secret to be used.
-
- This method will also replace the secret in the crypto object.
-
- :param secret_id: The id of the storage secret to be used.
- :type secret_id: str
- """
- self._secret_id = secret_id
-
- def _load_secrets(self):
- """
- Load storage secrets from local file.
- """
- # does the file exist in disk?
- if not os.path.isfile(self._secrets_path):
- raise IOError('File does not exist: %s' % self._secrets_path)
- # read storage secrets from file
- content = None
- with open(self._secrets_path, 'r') as f:
- content = json.loads(f.read())
- _, mac = self.import_recovery_document(content)
- if mac is False:
- self._store_secrets()
- self._put_secrets_in_shared_db()
- # choose first secret if no secret_id was given
- if self._secret_id is None:
- self._set_secret_id(self._secrets.items()[0][0])
-
- def _has_secret(self):
- """
- Return whether there is a storage secret available for use or not.
-
- :return: Whether there's a storage secret for symmetric encryption.
- :rtype: bool
- """
- if self._secret_id is None or self._secret_id not in self._secrets:
- try:
- self._load_secrets() # try to load from disk
- except IOError, e:
- logger.warning('IOError: %s' % str(e))
- try:
- self._get_storage_secret()
- return True
- except Exception:
- return False
-
- def _gen_secret(self):
- """
- Generate a secret for symmetric encryption and store in a local
- encrypted file.
-
- This method emits the following signals:
-
- * SOLEDAD_CREATING_KEYS
- * SOLEDAD_DONE_CREATING_KEYS
-
- A secret has the following structure:
-
- {
- '<secret_id>': {
- 'kdf': 'scrypt',
- 'kdf_salt': '<b64 repr of salt>'
- 'kdf_length': <key length>
- 'cipher': 'aes256',
- 'length': <secret length>,
- 'secret': '<encrypted b64 repr of storage_secret>',
- }
- }
-
- :return: The id of the generated secret.
- :rtype: str
- """
- signal(SOLEDAD_CREATING_KEYS, self._uuid)
- # generate random secret
- secret = os.urandom(self.GENERATED_SECRET_LENGTH)
- secret_id = sha256(secret).hexdigest()
- # generate random salt
- salt = os.urandom(self.SALT_LENGTH)
- # get a 256-bit key
- key = scrypt.hash(self._passphrase_as_string(), salt, buflen=32)
- iv, ciphertext = self._crypto.encrypt_sym(secret, key)
- self._secrets[secret_id] = {
- # leap.soledad.crypto submodule uses AES256 for symmetric
- # encryption.
- self.KDF_KEY: self.KDF_SCRYPT,
- self.KDF_SALT_KEY: binascii.b2a_base64(salt),
- self.KDF_LENGTH_KEY: len(key),
- self.CIPHER_KEY: self.CIPHER_AES256,
- self.LENGTH_KEY: len(secret),
- self.SECRET_KEY: '%s%s%s' % (
- str(iv), self.IV_SEPARATOR, binascii.b2a_base64(ciphertext)),
- }
- self._store_secrets()
- signal(SOLEDAD_DONE_CREATING_KEYS, self._uuid)
- return secret_id
-
- def _store_secrets(self):
- """
- Store secrets in C{Soledad.STORAGE_SECRETS_FILE_PATH}.
- """
- with open(self._secrets_path, 'w') as f:
- f.write(
- json.dumps(
- self.export_recovery_document()))
-
- def change_passphrase(self, new_passphrase):
- """
- Change the passphrase that encrypts the storage secret.
-
- :param new_passphrase: The new passphrase.
- :type new_passphrase: unicode
-
- :raise NoStorageSecret: Raised if there's no storage secret available.
- """
- # maybe we want to add more checks to guarantee passphrase is
- # reasonable?
- soledad_assert_type(new_passphrase, unicode)
- if len(new_passphrase) < self.MINIMUM_PASSPHRASE_LENGTH:
- raise PassphraseTooShort(
- 'Passphrase must be at least %d characters long!' %
- self.MINIMUM_PASSPHRASE_LENGTH)
- # ensure there's a secret for which the passphrase will be changed.
- if not self._has_secret():
- raise NoStorageSecret()
- secret = self._get_storage_secret()
- # generate random salt
- new_salt = os.urandom(self.SALT_LENGTH)
- # get a 256-bit key
- key = scrypt.hash(new_passphrase.encode('utf-8'), new_salt, buflen=32)
- iv, ciphertext = self._crypto.encrypt_sym(secret, key)
- # XXX update all secrets in the dict
- self._secrets[self._secret_id] = {
- # leap.soledad.crypto submodule uses AES256 for symmetric
- # encryption.
- self.KDF_KEY: self.KDF_SCRYPT, # TODO: remove hard coded kdf
- self.KDF_SALT_KEY: binascii.b2a_base64(new_salt),
- self.KDF_LENGTH_KEY: len(key),
- self.CIPHER_KEY: self.CIPHER_AES256,
- self.LENGTH_KEY: len(secret),
- self.SECRET_KEY: '%s%s%s' % (
- str(iv), self.IV_SEPARATOR, binascii.b2a_base64(ciphertext)),
- }
- self._passphrase = new_passphrase
- self._store_secrets()
- self._put_secrets_in_shared_db()
-
- #
- # General crypto utility methods.
- #
-
@property
def _shared_db(self):
"""
@@ -697,63 +300,6 @@ class Soledad(object):
creds=self._creds)
return self._shared_db_instance
- def _shared_db_doc_id(self):
- """
- Calculate the doc_id of the document in the shared db that stores key
- material.
-
- :return: the hash
- :rtype: str
- """
- return sha256(
- '%s%s' %
- (self._passphrase_as_string(), self.uuid)).hexdigest()
-
- def _get_secrets_from_shared_db(self):
- """
- Retrieve the document with encrypted key material from the shared
- database.
-
- :return: a document with encrypted key material in its contents
- :rtype: SoledadDocument
- """
- signal(SOLEDAD_DOWNLOADING_KEYS, self._uuid)
- db = self._shared_db
- if not db:
- logger.warning('No shared db found')
- return
- doc = db.get_doc(self._shared_db_doc_id())
- signal(SOLEDAD_DONE_DOWNLOADING_KEYS, self._uuid)
- return doc
-
- def _put_secrets_in_shared_db(self):
- """
- Assert local keys are the same as shared db's ones.
-
- Try to fetch keys from shared recovery database. If they already exist
- in the remote db, assert that that data is the same as local data.
- Otherwise, upload keys to shared recovery database.
- """
- soledad_assert(
- self._has_secret(),
- 'Tried to send keys to server but they don\'t exist in local '
- 'storage.')
- # try to get secrets doc from server, otherwise create it
- doc = self._get_secrets_from_shared_db()
- if doc is None:
- doc = SoledadDocument(
- doc_id=self._shared_db_doc_id())
- # fill doc with encrypted secrets
- doc.content = self.export_recovery_document()
- # upload secrets to server
- signal(SOLEDAD_UPLOADING_KEYS, self._uuid)
- db = self._shared_db
- if not db:
- logger.warning('No shared db found')
- return
- db.put_doc(doc)
- signal(SOLEDAD_DONE_UPLOADING_KEYS, self._uuid)
-
#
# Document storage, retrieval and sync.
#
@@ -1153,104 +699,6 @@ class Soledad(object):
token = property(_get_token, _set_token, doc='The authentication Token.')
#
- # Recovery document export and import methods
- #
-
- def export_recovery_document(self):
- """
- Export the storage secrets.
-
- A recovery document has the following structure:
-
- {
- 'storage_secrets': {
- '<storage_secret id>': {
- 'kdf': 'scrypt',
- 'kdf_salt': '<b64 repr of salt>'
- 'kdf_length': <key length>
- 'cipher': 'aes256',
- 'length': <secret length>,
- 'secret': '<encrypted storage_secret>',
- },
- },
- 'kdf': 'scrypt',
- 'kdf_salt': '<b64 repr of salt>',
- 'kdf_length: <key length>,
- '_mac_method': 'hmac',
- '_mac': '<mac>'
- }
-
- Note that multiple storage secrets might be stored in one recovery
- document. This method will also calculate a MAC of a string
- representation of the secrets dictionary.
-
- :return: The recovery document.
- :rtype: dict
- """
- # create salt and key for calculating MAC
- salt = os.urandom(self.SALT_LENGTH)
- key = scrypt.hash(self._passphrase_as_string(), salt, buflen=32)
- data = {
- self.STORAGE_SECRETS_KEY: self._secrets,
- self.KDF_KEY: self.KDF_SCRYPT,
- self.KDF_SALT_KEY: binascii.b2a_base64(salt),
- self.KDF_LENGTH_KEY: len(key),
- MAC_METHOD_KEY: MacMethods.HMAC,
- MAC_KEY: hmac.new(
- key,
- json.dumps(self._secrets),
- sha256).hexdigest(),
- }
- return data
-
- def import_recovery_document(self, data):
- """
- Import storage secrets for symmetric encryption and uuid (if present)
- from a recovery document.
-
- Note that this method does not store the imported data on disk. For
- that, use C{self._store_secrets()}.
-
- :param data: The recovery document.
- :type data: dict
-
- :return: A tuple containing the number of imported secrets and whether
- there was MAC informationa available for authenticating.
- :rtype: (int, bool)
- """
- soledad_assert(self.STORAGE_SECRETS_KEY in data)
- # check mac of the recovery document
- mac = None
- if MAC_KEY in data:
- soledad_assert(data[MAC_KEY] is not None)
- soledad_assert(MAC_METHOD_KEY in data)
- soledad_assert(self.KDF_KEY in data)
- soledad_assert(self.KDF_SALT_KEY in data)
- soledad_assert(self.KDF_LENGTH_KEY in data)
- if data[MAC_METHOD_KEY] == MacMethods.HMAC:
- key = scrypt.hash(
- self._passphrase_as_string(),
- binascii.a2b_base64(data[self.KDF_SALT_KEY]),
- buflen=32)
- mac = hmac.new(
- key,
- json.dumps(data[self.STORAGE_SECRETS_KEY]),
- sha256).hexdigest()
- else:
- raise UnknownMacMethod('Unknown MAC method: %s.' %
- data[MAC_METHOD_KEY])
- if mac != data[MAC_KEY]:
- raise WrongMac('Could not authenticate recovery document\'s '
- 'contents.')
- # include secrets in the secret pool.
- secrets = 0
- for secret_id, secret_data in data[self.STORAGE_SECRETS_KEY].items():
- if secret_id not in self._secrets:
- secrets += 1
- self._secrets[secret_id] = secret_data
- return secrets, mac
-
- #
# Setters/getters
#
@@ -1259,18 +707,26 @@ class Soledad(object):
uuid = property(_get_uuid, doc='The user uuid.')
- def _get_secret_id(self):
- return self._secret_id
+ def get_secret_id(self):
+ return self._secrets.secret_id
+
+ def set_secret_id(self, secret_id):
+ self._secrets.set_secret_id(secret_id)
secret_id = property(
- _get_secret_id,
+ get_secret_id,
+ set_secret_id,
doc='The active secret id.')
+ def _set_secrets_path(self, secrets_path):
+ self._secrets.secrets_path = secrets_path
+
def _get_secrets_path(self):
- return self._secrets_path
+ return self._secrets.secrets_path
secrets_path = property(
_get_secrets_path,
+ _set_secrets_path,
doc='The path for the file containing the encrypted symmetric secret.')
def _get_local_db_path(self):
@@ -1287,20 +743,31 @@ class Soledad(object):
_get_server_url,
doc='The URL of the Soledad server.')
- storage_secret = property(
- _get_storage_secret,
- doc='The secret used for symmetric encryption.')
+ @property
+ def storage_secret(self):
+ """
+ Return the secret used for symmetric encryption.
+ """
+ return self._secrets.storage_secret
+
+ @property
+ def secrets(self):
+ return self._secrets
- def _get_passphrase(self):
- return self._passphrase
+ @property
+ def passphrase(self):
+ return self._secrets.passphrase
- passphrase = property(
- _get_passphrase,
- doc='The passphrase for locking and unlocking encryption secrets for '
- 'local and remote storage.')
+ def change_passphrase(self, new_passphrase):
+ """
+ Change the passphrase that encrypts the storage secret.
- def _passphrase_as_string(self):
- return self._passphrase.encode('utf-8')
+ :param new_passphrase: The new passphrase.
+ :type new_passphrase: unicode
+
+ :raise NoStorageSecret: Raised if there's no storage secret available.
+ """
+ self._secrets.change_passphrase(new_passphrase)
# ----------------------------------------------------------------------------
diff --git a/client/src/leap/soledad/client/crypto.py b/client/src/leap/soledad/client/crypto.py
index eb5a4f64..4a64b5a8 100644
--- a/client/src/leap/soledad/client/crypto.py
+++ b/client/src/leap/soledad/client/crypto.py
@@ -242,7 +242,7 @@ class SoledadCrypto(object):
return hmac.new(
self.secret[
MAC_KEY_LENGTH:
- self._soledad.REMOTE_STORAGE_SECRET_LENGTH],
+ self._soledad.secrets.REMOTE_STORAGE_SECRET_LENGTH],
doc_id,
hashlib.sha256).digest()
@@ -819,7 +819,8 @@ class SyncDecrypterPool(SyncEncryptDecryptPool):
try:
content = json.loads(content)
except TypeError:
- logger.warning("Wrong type while decoding json: %s" % repr(docstr))
+ logger.warning("Wrong type while decoding json: %s"
+ % repr(content))
return
key = self._crypto.doc_passphrase(doc_id)
@@ -884,11 +885,15 @@ class SyncDecrypterPool(SyncEncryptDecryptPool):
all_docs = self.get_docs_by_generation()
decrypted_docs = self.get_docs_by_generation(encrypted=False)
insertable = []
- for doc_id, rev, content, gen, trans_id, encrypted in all_docs:
- next_decrypted = decrypted_docs.next()
- if doc_id == next_decrypted[0]:
- insertable.append((doc_id, rev, content, gen, trans_id))
- else:
+ for doc_id, rev, _, gen, trans_id, encrypted in all_docs:
+ try:
+ next_decrypted = decrypted_docs.next()
+ if doc_id == next_decrypted[0]:
+ content = next_decrypted[2]
+ insertable.append((doc_id, rev, content, gen, trans_id))
+ else:
+ break
+ except StopIteration:
break
return insertable
@@ -966,7 +971,7 @@ class SyncDecrypterPool(SyncEncryptDecryptPool):
"""
# could pass source_replica in params for callback chain
insert_fun = self._insert_doc_cb[self.source_replica_uid]
- logger.debug("Sync decrypter pool: inserting doc in local db: " \
+ logger.debug("Sync decrypter pool: inserting doc in local db: "
"%s:%s %s" % (doc_id, doc_rev, gen))
try:
# convert deleted documents to avoid error on document creation
diff --git a/client/src/leap/soledad/client/secrets.py b/client/src/leap/soledad/client/secrets.py
new file mode 100644
index 00000000..3c6fc569
--- /dev/null
+++ b/client/src/leap/soledad/client/secrets.py
@@ -0,0 +1,681 @@
+# -*- coding: utf-8 -*-
+# secrets.py
+# Copyright (C) 2014 LEAP
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+
+"""
+Soledad secrets handling.
+"""
+
+
+import os
+import scrypt
+import hmac
+import logging
+import binascii
+import errno
+
+
+from hashlib import sha256
+import simplejson as json
+
+
+from leap.soledad.common import (
+ soledad_assert,
+ soledad_assert_type
+)
+from leap.soledad.common.document import SoledadDocument
+from leap.soledad.common.crypto import (
+ MacMethods,
+ UnknownMacMethod,
+ WrongMac,
+ MAC_KEY,
+ MAC_METHOD_KEY,
+)
+from leap.soledad.common.errors import (
+ InvalidTokenError,
+ NotLockedError,
+ AlreadyLockedError,
+ LockTimedOutError,
+)
+from leap.soledad.client.events import (
+ SOLEDAD_CREATING_KEYS,
+ SOLEDAD_DONE_CREATING_KEYS,
+ SOLEDAD_DOWNLOADING_KEYS,
+ SOLEDAD_DONE_DOWNLOADING_KEYS,
+ SOLEDAD_UPLOADING_KEYS,
+ SOLEDAD_DONE_UPLOADING_KEYS,
+ signal,
+)
+
+
+logger = logging.getLogger(name=__name__)
+
+
+#
+# Exceptions
+#
+
+class NoStorageSecret(Exception):
+ """
+ Raised when trying to use a storage secret but none is available.
+ """
+ pass
+
+
+class PassphraseTooShort(Exception):
+ """
+ Raised when trying to change the passphrase but the provided passphrase is
+ too short.
+ """
+
+
+class BootstrapSequenceError(Exception):
+ """
+ Raised when an attempt to generate a secret and store it in a recovery
+ document on server failed.
+ """
+
+
+#
+# Secrets handler
+#
+
+class SoledadSecrets(object):
+ """
+ Soledad secrets handler.
+
+ The first C{self.REMOTE_STORAGE_SECRET_LENGTH} bytes of the storage
+ secret are used for remote storage encryption. We use the next
+ C{self.LOCAL_STORAGE_SECRET} bytes to derive a key for local storage.
+ From these bytes, the first C{self.SALT_LENGTH} bytes are used as the
+ salt and the rest as the password for the scrypt hashing.
+ """
+
+ LOCAL_STORAGE_SECRET_LENGTH = 512
+ """
+ The length of the secret used to derive a passphrase for the SQLCipher
+ database.
+ """
+
+ REMOTE_STORAGE_SECRET_LENGTH = 512
+ """
+ The length of the secret used to derive an encryption key and a MAC auth
+ key for remote storage.
+ """
+
+ SALT_LENGTH = 64
+ """
+ The length of the salt used to derive the key for the storage secret
+ encryption.
+ """
+
+ MINIMUM_PASSPHRASE_LENGTH = 6
+ """
+ The minimum length for a passphrase. The passphrase length is only checked
+ when the user changes her passphrase, not when she instantiates Soledad.
+ """
+
+ IV_SEPARATOR = ":"
+ """
+ A separator used for storing the encryption initial value prepended to the
+ ciphertext.
+ """
+
+ UUID_KEY = 'uuid'
+ STORAGE_SECRETS_KEY = 'storage_secrets'
+ SECRET_KEY = 'secret'
+ CIPHER_KEY = 'cipher'
+ LENGTH_KEY = 'length'
+ KDF_KEY = 'kdf'
+ KDF_SALT_KEY = 'kdf_salt'
+ KDF_LENGTH_KEY = 'kdf_length'
+ KDF_SCRYPT = 'scrypt'
+ CIPHER_AES256 = 'aes256'
+ """
+ Keys used to access storage secrets in recovery documents.
+ """
+
+ def __init__(self, uuid, passphrase, secrets_path, shared_db, crypto,
+ secret_id=None):
+ """
+ Initialize the secrets manager.
+
+ :param uuid: User's unique id.
+ :type uuid: str
+ :param passphrase: The passphrase for locking and unlocking encryption
+ secrets for local and remote storage.
+ :type passphrase: unicode
+ :param secrets_path: Path for storing encrypted key used for
+ symmetric encryption.
+ :type secrets_path: str
+ :param shared_db: The shared database that stores user secrets.
+ :type shared_db: leap.soledad.client.shared_db.SoledadSharedDatabase
+ :param crypto: A soledad crypto object.
+ :type crypto: SoledadCrypto
+ :param secret_id: The id of the storage secret to be used.
+ :type secret_id: str
+ """
+ self._uuid = uuid
+ self._passphrase = passphrase
+ self._secrets_path = secrets_path
+ self._shared_db = shared_db
+ self._crypto = crypto
+ self._secret_id = secret_id
+ self._secrets = {}
+
+ def bootstrap(self):
+ """
+ Bootstrap secrets.
+
+ Soledad secrets bootstrap is the following sequence of stages:
+
+ * stage 1 - local secret loading:
+ - if secrets exist locally, load them.
+ * stage 2 - remote secret loading:
+ - else, if secrets exist in server, download them.
+ * stage 3 - secret generation:
+ - else, generate a new secret and store in server.
+
+ This method decides which bootstrap stages have already been performed
+ and performs the missing ones in order.
+
+ :raise BootstrapSequenceError: Raised when the secret generation and
+ storage on server sequence has failed for some reason.
+ """
+ # STAGE 1 - verify if secrets exist locally
+ if not self._has_secret(): # try to load from local storage.
+
+ # STAGE 2 - there are no secrets in local storage, so try to fetch
+ # encrypted secrets from server.
+ logger.info(
+ 'Trying to fetch cryptographic secrets from shared recovery '
+ 'database...')
+
+ # --- start of atomic operation in shared db ---
+
+ # obtain lock on shared db
+ token = timeout = None
+ try:
+ token, timeout = self._shared_db.lock()
+ except AlreadyLockedError:
+ raise BootstrapSequenceError('Database is already locked.')
+ except LockTimedOutError:
+ raise BootstrapSequenceError('Lock operation timed out.')
+
+ self._get_or_gen_crypto_secrets()
+
+ # release the lock on shared db
+ try:
+ self._shared_db.unlock(token)
+ self._shared_db.close()
+ except NotLockedError:
+ # for some reason the lock expired. Despite that, secret
+ # loading or generation/storage must have been executed
+ # successfully, so we pass.
+ pass
+ except InvalidTokenError:
+ # here, our lock has not only expired but also some other
+ # client application has obtained a new lock and is currently
+ # doing its thing in the shared database. Using the same
+ # reasoning as above, we assume everything went smooth and
+ # pass.
+ pass
+ except Exception as e:
+ logger.error("Unhandled exception when unlocking shared "
+ "database.")
+ logger.exception(e)
+
+ # --- end of atomic operation in shared db ---
+
+ def _has_secret(self):
+ """
+ Return whether there is a storage secret available for use or not.
+
+ :return: Whether there's a storage secret for symmetric encryption.
+ :rtype: bool
+ """
+ if self._secret_id is None or self._secret_id not in self._secrets:
+ try:
+ self._load_secrets() # try to load from disk
+ except IOError as e:
+ logger.warning('IOError: %s' % str(e))
+ try:
+ self.storage_secret
+ return True
+ except Exception as e:
+ logger.warning("Couldn't load storage secret: %s" % str(e))
+ return False
+
+ def _load_secrets(self):
+ """
+ Load storage secrets from local file.
+ """
+ # does the file exist in disk?
+ if not os.path.isfile(self._secrets_path):
+ raise IOError('File does not exist: %s' % self._secrets_path)
+ # read storage secrets from file
+ content = None
+ with open(self._secrets_path, 'r') as f:
+ content = json.loads(f.read())
+ _, mac = self._import_recovery_document(content)
+ if mac is False:
+ self._store_secrets()
+ self._put_secrets_in_shared_db()
+ # choose first secret if no secret_id was given
+ if self._secret_id is None:
+ self.set_secret_id(self._secrets.items()[0][0])
+
+ def _get_or_gen_crypto_secrets(self):
+ """
+ Retrieves or generates the crypto secrets.
+
+ :raises BootstrapSequenceError: Raised when unable to store secrets in
+ shared database.
+ """
+ doc = self._get_secrets_from_shared_db()
+
+ if doc:
+ logger.info(
+ 'Found cryptographic secrets in shared recovery '
+ 'database.')
+ _, mac = self._import_recovery_document(doc.content)
+ if mac is False:
+ self.put_secrets_in_shared_db()
+ self._store_secrets() # save new secrets in local file
+ if self._secret_id is None:
+ self.set_secret_id(self._secrets.items()[0][0])
+ else:
+ # STAGE 3 - there are no secrets in server also, so
+ # generate a secret and store it in remote db.
+ logger.info(
+ 'No cryptographic secrets found, creating new '
+ ' secrets...')
+ self.set_secret_id(self._gen_secret())
+ try:
+ self._put_secrets_in_shared_db()
+ except Exception as ex:
+ # storing generated secret in shared db failed for
+ # some reason, so we erase the generated secret and
+ # raise.
+ try:
+ os.unlink(self._secrets_path)
+ except OSError as e:
+ if e.errno != errno.ENOENT: # no such file or directory
+ logger.exception(e)
+ logger.exception(ex)
+ raise BootstrapSequenceError(
+ 'Could not store generated secret in the shared '
+ 'database, bailing out...')
+
+ #
+ # Shared DB related methods
+ #
+
+ def _shared_db_doc_id(self):
+ """
+ Calculate the doc_id of the document in the shared db that stores key
+ material.
+
+ :return: the hash
+ :rtype: str
+ """
+ return sha256(
+ '%s%s' %
+ (self._passphrase_as_string(), self._uuid)).hexdigest()
+
+ def _export_recovery_document(self):
+ """
+ Export the storage secrets.
+
+ A recovery document has the following structure:
+
+ {
+ 'storage_secrets': {
+ '<storage_secret id>': {
+ 'kdf': 'scrypt',
+ 'kdf_salt': '<b64 repr of salt>'
+ 'kdf_length': <key length>
+ 'cipher': 'aes256',
+ 'length': <secret length>,
+ 'secret': '<encrypted storage_secret>',
+ },
+ },
+ 'kdf': 'scrypt',
+ 'kdf_salt': '<b64 repr of salt>',
+ 'kdf_length: <key length>,
+ '_mac_method': 'hmac',
+ '_mac': '<mac>'
+ }
+
+ Note that multiple storage secrets might be stored in one recovery
+ document. This method will also calculate a MAC of a string
+ representation of the secrets dictionary.
+
+ :return: The recovery document.
+ :rtype: dict
+ """
+ # create salt and key for calculating MAC
+ salt = os.urandom(self.SALT_LENGTH)
+ key = scrypt.hash(self._passphrase_as_string(), salt, buflen=32)
+ data = {
+ self.STORAGE_SECRETS_KEY: self._secrets,
+ self.KDF_KEY: self.KDF_SCRYPT,
+ self.KDF_SALT_KEY: binascii.b2a_base64(salt),
+ self.KDF_LENGTH_KEY: len(key),
+ MAC_METHOD_KEY: MacMethods.HMAC,
+ MAC_KEY: hmac.new(
+ key,
+ json.dumps(self._secrets),
+ sha256).hexdigest(),
+ }
+ return data
+
+ def _import_recovery_document(self, data):
+ """
+ Import storage secrets for symmetric encryption and uuid (if present)
+ from a recovery document.
+
+ Note that this method does not store the imported data on disk. For
+ that, use C{self._store_secrets()}.
+
+ :param data: The recovery document.
+ :type data: dict
+
+ :return: A tuple containing the number of imported secrets and whether
+ there was MAC informationa available for authenticating.
+ :rtype: (int, bool)
+ """
+ soledad_assert(self.STORAGE_SECRETS_KEY in data)
+ # check mac of the recovery document
+ mac = None
+ if MAC_KEY in data:
+ soledad_assert(data[MAC_KEY] is not None)
+ soledad_assert(MAC_METHOD_KEY in data)
+ soledad_assert(self.KDF_KEY in data)
+ soledad_assert(self.KDF_SALT_KEY in data)
+ soledad_assert(self.KDF_LENGTH_KEY in data)
+ if data[MAC_METHOD_KEY] == MacMethods.HMAC:
+ key = scrypt.hash(
+ self._passphrase_as_string(),
+ binascii.a2b_base64(data[self.KDF_SALT_KEY]),
+ buflen=32)
+ mac = hmac.new(
+ key,
+ json.dumps(data[self.STORAGE_SECRETS_KEY]),
+ sha256).hexdigest()
+ else:
+ raise UnknownMacMethod('Unknown MAC method: %s.' %
+ data[MAC_METHOD_KEY])
+ if mac != data[MAC_KEY]:
+ raise WrongMac('Could not authenticate recovery document\'s '
+ 'contents.')
+ # include secrets in the secret pool.
+ secrets = 0
+ for secret_id, secret_data in data[self.STORAGE_SECRETS_KEY].items():
+ if secret_id not in self._secrets:
+ secrets += 1
+ self._secrets[secret_id] = secret_data
+ return secrets, mac
+
+ def _get_secrets_from_shared_db(self):
+ """
+ Retrieve the document with encrypted key material from the shared
+ database.
+
+ :return: a document with encrypted key material in its contents
+ :rtype: SoledadDocument
+ """
+ signal(SOLEDAD_DOWNLOADING_KEYS, self._uuid)
+ db = self._shared_db
+ if not db:
+ logger.warning('No shared db found')
+ return
+ doc = db.get_doc(self._shared_db_doc_id())
+ signal(SOLEDAD_DONE_DOWNLOADING_KEYS, self._uuid)
+ return doc
+
+ def _put_secrets_in_shared_db(self):
+ """
+ Assert local keys are the same as shared db's ones.
+
+ Try to fetch keys from shared recovery database. If they already exist
+ in the remote db, assert that that data is the same as local data.
+ Otherwise, upload keys to shared recovery database.
+ """
+ soledad_assert(
+ self._has_secret(),
+ 'Tried to send keys to server but they don\'t exist in local '
+ 'storage.')
+ # try to get secrets doc from server, otherwise create it
+ doc = self._get_secrets_from_shared_db()
+ if doc is None:
+ doc = SoledadDocument(
+ doc_id=self._shared_db_doc_id())
+ # fill doc with encrypted secrets
+ doc.content = self._export_recovery_document()
+ # upload secrets to server
+ signal(SOLEDAD_UPLOADING_KEYS, self._uuid)
+ db = self._shared_db
+ if not db:
+ logger.warning('No shared db found')
+ return
+ db.put_doc(doc)
+ signal(SOLEDAD_DONE_UPLOADING_KEYS, self._uuid)
+
+ #
+ # Management of secret for symmetric encryption.
+ #
+
+ @property
+ def storage_secret(self):
+ """
+ Return the storage secret.
+
+ Storage secret is encrypted before being stored. This method decrypts
+ and returns the stored secret.
+
+ :return: The storage secret.
+ :rtype: str
+ """
+ # calculate the encryption key
+ key = scrypt.hash(
+ self._passphrase_as_string(),
+ # the salt is stored base64 encoded
+ binascii.a2b_base64(
+ self._secrets[self._secret_id][self.KDF_SALT_KEY]),
+ buflen=32, # we need a key with 256 bits (32 bytes).
+ )
+ # recover the initial value and ciphertext
+ iv, ciphertext = self._secrets[self._secret_id][self.SECRET_KEY].split(
+ self.IV_SEPARATOR, 1)
+ ciphertext = binascii.a2b_base64(ciphertext)
+ return self._crypto.decrypt_sym(ciphertext, key, iv=iv)
+
+ def set_secret_id(self, secret_id):
+ """
+ Define the id of the storage secret to be used.
+
+ This method will also replace the secret in the crypto object.
+
+ :param secret_id: The id of the storage secret to be used.
+ :type secret_id: str
+ """
+ self._secret_id = secret_id
+
+ def _gen_secret(self):
+ """
+ Generate a secret for symmetric encryption and store in a local
+ encrypted file.
+
+ This method emits the following signals:
+
+ * SOLEDAD_CREATING_KEYS
+ * SOLEDAD_DONE_CREATING_KEYS
+
+ A secret has the following structure:
+
+ {
+ '<secret_id>': {
+ 'kdf': 'scrypt',
+ 'kdf_salt': '<b64 repr of salt>'
+ 'kdf_length': <key length>
+ 'cipher': 'aes256',
+ 'length': <secret length>,
+ 'secret': '<encrypted b64 repr of storage_secret>',
+ }
+ }
+
+ :return: The id of the generated secret.
+ :rtype: str
+ """
+ signal(SOLEDAD_CREATING_KEYS, self._uuid)
+ # generate random secret
+ secret = os.urandom(
+ self.LOCAL_STORAGE_SECRET_LENGTH
+ + self.REMOTE_STORAGE_SECRET_LENGTH)
+ secret_id = sha256(secret).hexdigest()
+ # generate random salt
+ salt = os.urandom(self.SALT_LENGTH)
+ # get a 256-bit key
+ key = scrypt.hash(self._passphrase_as_string(), salt, buflen=32)
+ iv, ciphertext = self._crypto.encrypt_sym(secret, key)
+ self._secrets[secret_id] = {
+ # leap.soledad.crypto submodule uses AES256 for symmetric
+ # encryption.
+ self.KDF_KEY: self.KDF_SCRYPT,
+ self.KDF_SALT_KEY: binascii.b2a_base64(salt),
+ self.KDF_LENGTH_KEY: len(key),
+ self.CIPHER_KEY: self.CIPHER_AES256,
+ self.LENGTH_KEY: len(secret),
+ self.SECRET_KEY: '%s%s%s' % (
+ str(iv), self.IV_SEPARATOR, binascii.b2a_base64(ciphertext)),
+ }
+ self._store_secrets()
+ signal(SOLEDAD_DONE_CREATING_KEYS, self._uuid)
+ return secret_id
+
+ def _store_secrets(self):
+ """
+ Store secrets in C{Soledad.STORAGE_SECRETS_FILE_PATH}.
+ """
+ with open(self._secrets_path, 'w') as f:
+ f.write(
+ json.dumps(
+ self._export_recovery_document()))
+
+ def change_passphrase(self, new_passphrase):
+ """
+ Change the passphrase that encrypts the storage secret.
+
+ :param new_passphrase: The new passphrase.
+ :type new_passphrase: unicode
+
+ :raise NoStorageSecret: Raised if there's no storage secret available.
+ """
+ # TODO: maybe we want to add more checks to guarantee passphrase is
+ # reasonable?
+ soledad_assert_type(new_passphrase, unicode)
+ if len(new_passphrase) < self.MINIMUM_PASSPHRASE_LENGTH:
+ raise PassphraseTooShort(
+ 'Passphrase must be at least %d characters long!' %
+ self.MINIMUM_PASSPHRASE_LENGTH)
+ # ensure there's a secret for which the passphrase will be changed.
+ if not self._has_secret():
+ raise NoStorageSecret()
+ secret = self.storage_secret
+ # generate random salt
+ new_salt = os.urandom(self.SALT_LENGTH)
+ # get a 256-bit key
+ key = scrypt.hash(new_passphrase.encode('utf-8'), new_salt, buflen=32)
+ iv, ciphertext = self._crypto.encrypt_sym(secret, key)
+ # XXX update all secrets in the dict
+ self._secrets[self._secret_id] = {
+ # leap.soledad.crypto submodule uses AES256 for symmetric
+ # encryption.
+ self.KDF_KEY: self.KDF_SCRYPT, # TODO: remove hard coded kdf
+ self.KDF_SALT_KEY: binascii.b2a_base64(new_salt),
+ self.KDF_LENGTH_KEY: len(key),
+ self.CIPHER_KEY: self.CIPHER_AES256,
+ self.LENGTH_KEY: len(secret),
+ self.SECRET_KEY: '%s%s%s' % (
+ str(iv), self.IV_SEPARATOR, binascii.b2a_base64(ciphertext)),
+ }
+ self._passphrase = new_passphrase
+ self._store_secrets()
+ self._put_secrets_in_shared_db()
+
+ #
+ # Setters and getters
+ #
+
+ @property
+ def secret_id(self):
+ return self._secret_id
+
+ def _get_secrets_path(self):
+ return self._secrets_path
+
+ def _set_secrets_path(self, secrets_path):
+ self._secrets_path = secrets_path
+
+ secrets_path = property(
+ _get_secrets_path,
+ _set_secrets_path,
+ doc='The path for the file containing the encrypted symmetric secret.')
+
+ @property
+ def passphrase(self):
+ """
+ Return the passphrase for locking and unlocking encryption secrets for
+ local and remote storage.
+ """
+ return self._passphrase
+
+ def _passphrase_as_string(self):
+ return self._passphrase.encode('utf-8')
+
+ def get_syncdb_secret(self):
+ """
+ Return the secret for sync db.
+ """
+ # TODO: implement.
+ pass
+
+ def get_remote_secret(self):
+ """
+ Return the secret for remote storage.
+ """
+ # TODO: implement
+ pass
+
+ def get_local_storage_key(self):
+ """
+ Return the local storage key derived from the local storage secret.
+ """
+ # salt indexes
+ salt_start = self.REMOTE_STORAGE_SECRET_LENGTH
+ salt_end = salt_start + self.SALT_LENGTH
+ # password indexes
+ pwd_start = salt_end
+ pwd_end = salt_start + self.LOCAL_STORAGE_SECRET_LENGTH
+ # calculate the key for local encryption
+ secret = self.storage_secret
+ return scrypt.hash(
+ secret[pwd_start:pwd_end], # the password
+ secret[salt_start:salt_end], # the salt
+ buflen=32, # we need a key with 256 bits (32 bytes)
+ )