Split client and server in two different packages and refactor.

1 files changed, 0 insertions, 653 deletions

diff --git a/src/leap/soledad/backends/sqlcipher.py b/src/leap/soledad/backends/sqlcipher.py
deleted file mode 100644
index d6d62f21..00000000
--- a/src/leap/soledad/backends/sqlcipher.py
+++ /dev/null
@@ -1,653 +0,0 @@
-# -*- coding: utf-8 -*-
-# sqlcipher.py
-# Copyright (C) 2013 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/>.
-
-
-"""
-A U1DB backend that uses SQLCipher as its persistence layer.
-
-The SQLCipher API (http://sqlcipher.net/sqlcipher-api/) is fully implemented,
-with the exception of the following statements:
-
-  * PRAGMA cipher_use_hmac
-  * PRAGMA cipher_default_use_mac
-
-SQLCipher 2.0 introduced a per-page HMAC to validate that the page data has
-not be tampered with. By default, when creating or opening a database using
-SQLCipher 2, SQLCipher will attempt to use an HMAC check. This change in
-database format means that SQLCipher 2 can't operate on version 1.1.x
-databases by default. Thus, in order to provide backward compatibility with
-SQLCipher 1.1.x, PRAGMA cipher_use_hmac can be used to disable the HMAC
-functionality on specific databases.
-
-In some very specific cases, it is not possible to call PRAGMA cipher_use_hmac
-as one of the first operations on a database. An example of this is when
-trying to ATTACH a 1.1.x database to the main database. In these cases PRAGMA
-cipher_default_use_hmac can be used to globally alter the default use of HMAC
-when opening a database.
-
-So, as the statements above were introduced for backwards compatibility with
-SLCipher 1.1 databases, we do not implement them as all SQLCipher databases
-handled by Soledad should be created by SQLCipher >= 2.0.
-"""
-
-import os
-import time
-import string
-
-
-from u1db.backends import sqlite_backend
-from pysqlcipher import dbapi2
-from u1db import (
-    errors,
-)
-from leap.soledad.backends.leap_backend import LeapDocument
-
-
-# Monkey-patch u1db.backends.sqlite_backend with pysqlcipher.dbapi2
-sqlite_backend.dbapi2 = dbapi2
-
-
-def open(path, password, create=True, document_factory=None, crypto=None,
-         raw_key=False, cipher='aes-256-cbc', kdf_iter=4000,
-         cipher_page_size=1024):
-    """Open a database at the given location.
-
-    Will raise u1db.errors.DatabaseDoesNotExist if create=False and the
-    database does not already exist.
-
-    @param path: The filesystem path for the database to open.
-    @param type: str
-    @param create: True/False, should the database be created if it doesn't
-        already exist?
-    @param type: bool
-    @param document_factory: A function that will be called with the same
-        parameters as Document.__init__.
-    @type document_factory: callable
-    @param crypto: An instance of SoledadCrypto so we can encrypt/decrypt
-        document contents when syncing.
-    @type crypto: soledad.crypto.SoledadCrypto
-    @param raw_key: Whether C{password} is a raw 64-char hex string or a
-        passphrase that should be hashed to obtain the encyrption key.
-    @type raw_key: bool
-    @param cipher: The cipher and mode to use.
-    @type cipher: str
-    @param kdf_iter: The number of iterations to use.
-    @type kdf_iter: int
-    @param cipher_page_size: The page size.
-    @type cipher_page_size: int
-
-    @return: An instance of Database.
-    @rtype SQLCipherDatabase
-    """
-    return SQLCipherDatabase.open_database(
-        path, password, create=create, document_factory=document_factory,
-        crypto=crypto, raw_key=raw_key, cipher=cipher, kdf_iter=kdf_iter,
-        cipher_page_size=cipher_page_size)
-
-
-#
-# Exceptions
-#
-
-class DatabaseIsNotEncrypted(Exception):
-    """
-    Exception raised when trying to open non-encrypted databases.
-    """
-    pass
-
-
-class NotAnHexString(Exception):
-    """
-    Raised when trying to (raw) key the database with a non-hex string.
-    """
-    pass
-
-
-#
-# The SQLCipher database
-#
-
-class SQLCipherDatabase(sqlite_backend.SQLitePartialExpandDatabase):
-    """A U1DB implementation that uses SQLCipher as its persistence layer."""
-
-    _index_storage_value = 'expand referenced encrypted'
-
-    def __init__(self, sqlcipher_file, password, document_factory=None,
-                 crypto=None, raw_key=False, cipher='aes-256-cbc',
-                 kdf_iter=4000, cipher_page_size=1024):
-        """
-        Create a new sqlcipher file.
-
-        @param sqlcipher_file: The path for the SQLCipher file.
-        @type sqlcipher_file: str
-        @param password: The password that protects the SQLCipher db.
-        @type password: str
-        @param document_factory: A function that will be called with the same
-            parameters as Document.__init__.
-        @type document_factory: callable
-        @param crypto: An instance of SoledadCrypto so we can encrypt/decrypt
-            document contents when syncing.
-        @type crypto: soledad.crypto.SoledadCrypto
-        @param raw_key: Whether C{password} is a raw 64-char hex string or a
-            passphrase that should be hashed to obtain the encyrption key.
-        @type raw_key: bool
-        @param cipher: The cipher and mode to use.
-        @type cipher: str
-        @param kdf_iter: The number of iterations to use.
-        @type kdf_iter: int
-        @param cipher_page_size: The page size.
-        @type cipher_page_size: int
-        """
-        # ensure the db is encrypted if the file already exists
-        if os.path.exists(sqlcipher_file):
-            self.assert_db_is_encrypted(
-                sqlcipher_file, password, raw_key, cipher, kdf_iter,
-                cipher_page_size)
-        # connect to the database
-        self._db_handle = dbapi2.connect(sqlcipher_file)
-        # set SQLCipher cryptographic parameters
-        self._set_crypto_pragmas(
-            self._db_handle, password, raw_key, cipher, kdf_iter,
-            cipher_page_size)
-        self._real_replica_uid = None
-        self._ensure_schema()
-        self._crypto = crypto
-
-        def factory(doc_id=None, rev=None, json='{}', has_conflicts=False,
-                    syncable=True):
-            return LeapDocument(doc_id=doc_id, rev=rev, json=json,
-                                has_conflicts=has_conflicts,
-                                syncable=syncable)
-        self.set_document_factory(factory)
-
-    @classmethod
-    def _open_database(cls, sqlcipher_file, password, document_factory=None,
-                       crypto=None, raw_key=False, cipher='aes-256-cbc',
-                       kdf_iter=4000, cipher_page_size=1024):
-        """
-        Open a SQLCipher database.
-
-        @param sqlcipher_file: The path for the SQLCipher file.
-        @type sqlcipher_file: str
-        @param password: The password that protects the SQLCipher db.
-        @type password: str
-        @param document_factory: A function that will be called with the same
-            parameters as Document.__init__.
-        @type document_factory: callable
-        @param crypto: An instance of SoledadCrypto so we can encrypt/decrypt
-            document contents when syncing.
-        @type crypto: soledad.crypto.SoledadCrypto
-        @param raw_key: Whether C{password} is a raw 64-char hex string or a
-            passphrase that should be hashed to obtain the encyrption key.
-        @type raw_key: bool
-        @param cipher: The cipher and mode to use.
-        @type cipher: str
-        @param kdf_iter: The number of iterations to use.
-        @type kdf_iter: int
-        @param cipher_page_size: The page size.
-        @type cipher_page_size: int
-
-        @return: The database object.
-        @rtype: SQLCipherDatabase
-        """
-        if not os.path.isfile(sqlcipher_file):
-            raise errors.DatabaseDoesNotExist()
-        tries = 2
-        while True:
-            # Note: There seems to be a bug in sqlite 3.5.9 (with python2.6)
-            #       where without re-opening the database on Windows, it
-            #       doesn't see the transaction that was just committed
-            db_handle = dbapi2.connect(sqlcipher_file)
-            # set cryptographic params
-            cls._set_crypto_pragmas(
-                db_handle, password, raw_key, cipher, kdf_iter,
-                cipher_page_size)
-            c = db_handle.cursor()
-            v, err = cls._which_index_storage(c)
-            db_handle.close()
-            if v is not None:
-                break
-            # possibly another process is initializing it, wait for it to be
-            # done
-            if tries == 0:
-                raise err  # go for the richest error?
-            tries -= 1
-            time.sleep(cls.WAIT_FOR_PARALLEL_INIT_HALF_INTERVAL)
-        return SQLCipherDatabase._sqlite_registry[v](
-            sqlcipher_file, password, document_factory=document_factory,
-            crypto=crypto, raw_key=raw_key, cipher=cipher, kdf_iter=kdf_iter,
-            cipher_page_size=cipher_page_size)
-
-    @classmethod
-    def open_database(cls, sqlcipher_file, password, create, backend_cls=None,
-                      document_factory=None, crypto=None, raw_key=False,
-                      cipher='aes-256-cbc', kdf_iter=4000,
-                      cipher_page_size=1024):
-        """
-        Open a SQLCipher database.
-
-        @param sqlcipher_file: The path for the SQLCipher file.
-        @type sqlcipher_file: str
-        @param password: The password that protects the SQLCipher db.
-        @type password: str
-        @param create: Should the datbase be created if it does not already
-            exist?
-        @type: bool
-        @param backend_cls: A class to use as backend.
-        @type backend_cls: type
-        @param document_factory: A function that will be called with the same
-            parameters as Document.__init__.
-        @type document_factory: callable
-        @param crypto: An instance of SoledadCrypto so we can encrypt/decrypt
-            document contents when syncing.
-        @type crypto: soledad.crypto.SoledadCrypto
-        @param raw_key: Whether C{password} is a raw 64-char hex string or a
-            passphrase that should be hashed to obtain the encyrption key.
-        @type raw_key: bool
-        @param cipher: The cipher and mode to use.
-        @type cipher: str
-        @param kdf_iter: The number of iterations to use.
-        @type kdf_iter: int
-        @param cipher_page_size: The page size.
-        @type cipher_page_size: int
-
-        @return: The database object.
-        @rtype: SQLCipherDatabase
-        """
-        try:
-            return cls._open_database(
-                sqlcipher_file, password, document_factory=document_factory,
-                crypto=crypto, raw_key=raw_key, cipher=cipher,
-                kdf_iter=kdf_iter, cipher_page_size=cipher_page_size)
-        except errors.DatabaseDoesNotExist:
-            if not create:
-                raise
-            # TODO: remove backend class from here.
-            if backend_cls is None:
-                # default is SQLCipherPartialExpandDatabase
-                backend_cls = SQLCipherDatabase
-            return backend_cls(
-                sqlcipher_file, password, document_factory=document_factory,
-                crypto=crypto, raw_key=raw_key, cipher=cipher,
-                kdf_iter=kdf_iter, cipher_page_size=cipher_page_size)
-
-    def sync(self, url, creds=None, autocreate=True):
-        """
-        Synchronize documents with remote replica exposed at url.
-
-        @param url: The url of the target replica to sync with.
-        @type url: str
-        @param creds: optional dictionary giving credentials.
-            to authorize the operation with the server.
-        @type creds: dict
-        @param autocreate: Ask the target to create the db if non-existent.
-        @type autocreate: bool
-
-        @return: The local generation before the synchronisation was performed.
-        @rtype: int
-        """
-        from u1db.sync import Synchronizer
-        from leap.soledad.backends.leap_backend import LeapSyncTarget
-        return Synchronizer(
-            self,
-            LeapSyncTarget(url,
-                           creds=creds,
-                           crypto=self._crypto)).sync(autocreate=autocreate)
-
-    def _extra_schema_init(self, c):
-        """
-        Add any extra fields, etc to the basic table definitions.
-
-        @param c: The cursor for querying the database.
-        @type c: dbapi2.cursor
-        """
-        c.execute(
-            'ALTER TABLE document '
-            'ADD COLUMN syncable BOOL NOT NULL DEFAULT TRUE')
-
-    def _put_and_update_indexes(self, old_doc, doc):
-        """
-        Update a document and all indexes related to it.
-
-        @param old_doc: The old version of the document.
-        @type old_doc: u1db.Document
-        @param doc: The new version of the document.
-        @type doc: u1db.Document
-        """
-        sqlite_backend.SQLitePartialExpandDatabase._put_and_update_indexes(
-            self, old_doc, doc)
-        c = self._db_handle.cursor()
-        c.execute('UPDATE document SET syncable=? '
-                  'WHERE doc_id=?',
-                  (doc.syncable, doc.doc_id))
-
-    def _get_doc(self, doc_id, check_for_conflicts=False):
-        """
-        Get just the document content, without fancy handling.
-
-        @param doc_id: The unique document identifier
-        @type doc_id: str
-        @param include_deleted: If set to True, deleted documents will be
-            returned with empty content. Otherwise asking for a deleted
-            document will return None.
-        @type include_deleted: bool
-
-        @return: a Document object.
-        @type: u1db.Document
-        """
-        doc = sqlite_backend.SQLitePartialExpandDatabase._get_doc(
-            self, doc_id, check_for_conflicts)
-        if doc:
-            c = self._db_handle.cursor()
-            c.execute('SELECT syncable FROM document '
-                      'WHERE doc_id=?',
-                      (doc.doc_id,))
-            result = c.fetchone()
-            doc.syncable = bool(result[0])
-        return doc
-
-    #
-    # SQLCipher API methods
-    #
-
-    @classmethod
-    def assert_db_is_encrypted(cls, sqlcipher_file, key, raw_key, cipher,
-                               kdf_iter, cipher_page_size):
-        """
-        Assert that C{sqlcipher_file} contains an encrypted database.
-
-        When opening an existing database, PRAGMA key will not immediately
-        throw an error if the key provided is incorrect. To test that the
-        database can be successfully opened with the provided key, it is
-        necessary to perform some operation on the database (i.e. read from
-        it) and confirm it is success.
-
-        The easiest way to do this is select off the sqlite_master table,
-        which will attempt to read the first page of the database and will
-        parse the schema.
-
-        @param sqlcipher_file: The path for the SQLCipher file.
-        @type sqlcipher_file: str
-        @param key: The key that protects the SQLCipher db.
-        @type key: str
-        @param raw_key: Whether C{key} is a raw 64-char hex string or a
-            passphrase that should be hashed to obtain the encyrption key.
-        @type raw_key: bool
-        @param cipher: The cipher and mode to use.
-        @type cipher: str
-        @param kdf_iter: The number of iterations to use.
-        @type kdf_iter: int
-        @param cipher_page_size: The page size.
-        @type cipher_page_size: int
-        """
-        try:
-            # try to open an encrypted database with the regular u1db
-            # backend should raise a DatabaseError exception.
-            sqlite_backend.SQLitePartialExpandDatabase(sqlcipher_file)
-            raise DatabaseIsNotEncrypted()
-        except dbapi2.DatabaseError:
-            # assert that we can access it using SQLCipher with the given
-            # key
-            db_handle = dbapi2.connect(sqlcipher_file)
-            cls._set_crypto_pragmas(
-                db_handle, key, raw_key, cipher, kdf_iter, cipher_page_size)
-            db_handle.cursor().execute('SELECT count(*) FROM sqlite_master')
-
-    @classmethod
-    def _set_crypto_pragmas(cls, db_handle, key, raw_key, cipher, kdf_iter,
-                            cipher_page_size):
-        """
-        Set cryptographic params (key, cipher, KDF number of iterations and
-        cipher page size).
-        """
-        cls._pragma_key(db_handle, key, raw_key)
-        cls._pragma_cipher(db_handle, cipher)
-        cls._pragma_kdf_iter(db_handle, kdf_iter)
-        cls._pragma_cipher_page_size(db_handle, cipher_page_size)
-
-    @classmethod
-    def _pragma_key(cls, db_handle, key, raw_key):
-        """
-        Set the C{key} for use with the database.
-
-        The process of creating a new, encrypted database is called 'keying'
-        the database. SQLCipher uses just-in-time key derivation at the point
-        it is first needed for an operation. This means that the key (and any
-        options) must be set before the first operation on the database. As
-        soon as the database is touched (e.g. SELECT, CREATE TABLE, UPDATE,
-        etc.) and pages need to be read or written, the key is prepared for
-        use.
-
-        Implementation Notes:
-
-        * PRAGMA key should generally be called as the first operation on a
-          database.
-
-        @param key: The key for use with the database.
-        @type key: str
-        @param raw_key: Whether C{key} is a raw 64-char hex string or a
-            passphrase that should be hashed to obtain the encyrption key.
-        @type raw_key: bool
-        """
-        if raw_key:
-            cls._pragma_key_raw(db_handle, key)
-        else:
-            cls._pragma_key_passphrase(db_handle, key)
-
-    @classmethod
-    def _pragma_key_passphrase(cls, db_handle, passphrase):
-        """
-        Set a passphrase for encryption key derivation.
-
-        The key itself can be a passphrase, which is converted to a key using
-        PBKDF2 key derivation. The result is used as the encryption key for
-        the database. By using this method, there is no way to alter the KDF;
-        if you want to do so you should use a raw key instead and derive the
-        key using your own KDF.
-
-        @param db_handle: A handle to the SQLCipher database.
-        @type db_handle: pysqlcipher.Connection
-        @param passphrase: The passphrase used to derive the encryption key.
-        @type passphrase: str
-        """
-        db_handle.cursor().execute("PRAGMA key = '%s'" % passphrase)
-
-    @classmethod
-    def _pragma_key_raw(cls, db_handle, key):
-        """
-        Set a raw hexadecimal encryption key.
-
-        It is possible to specify an exact byte sequence using a blob literal.
-        With this method, it is the calling application's responsibility to
-        ensure that the data provided is a 64 character hex string, which will
-        be converted directly to 32 bytes (256 bits) of key data.
-
-        @param db_handle: A handle to the SQLCipher database.
-        @type db_handle: pysqlcipher.Connection
-        @param key: A 64 character hex string.
-        @type key: str
-        """
-        if not all(c in string.hexdigits for c in key):
-            raise NotAnHexString(key)
-        db_handle.cursor().execute('PRAGMA key = "x\'%s"' % key)
-
-    @classmethod
-    def _pragma_cipher(cls, db_handle, cipher='aes-256-cbc'):
-        """
-        Set the cipher and mode to use for symmetric encryption.
-
-        SQLCipher uses aes-256-cbc as the default cipher and mode of
-        operation. It is possible to change this, though not generally
-        recommended, using PRAGMA cipher.
-
-        SQLCipher makes direct use of libssl, so all cipher options available
-        to libssl are also available for use with SQLCipher. See `man enc` for
-        OpenSSL's supported ciphers.
-
-        Implementation Notes:
-
-        * PRAGMA cipher must be called after PRAGMA key and before the first
-          actual database operation or it will have no effect.
-
-        * If a non-default value is used PRAGMA cipher to create a database,
-          it must also be called every time that database is opened.
-
-        * SQLCipher does not implement its own encryption. Instead it uses the
-          widely available and peer-reviewed OpenSSL libcrypto for all
-          cryptographic functions.
-
-        @param db_handle: A handle to the SQLCipher database.
-        @type db_handle: pysqlcipher.Connection
-        @param cipher: The cipher and mode to use.
-        @type cipher: str
-        """
-        db_handle.cursor().execute("PRAGMA cipher = '%s'" % cipher)
-
-    @classmethod
-    def _pragma_kdf_iter(cls, db_handle, kdf_iter=4000):
-        """
-        Set the number of iterations for the key derivation function.
-
-        SQLCipher uses PBKDF2 key derivation to strengthen the key and make it
-        resistent to brute force and dictionary attacks. The default
-        configuration uses 4000 PBKDF2 iterations (effectively 16,000 SHA1
-        operations). PRAGMA kdf_iter can be used to increase or decrease the
-        number of iterations used.
-
-        Implementation Notes:
-
-        * PRAGMA kdf_iter must be called after PRAGMA key and before the first
-          actual database operation or it will have no effect.
-
-        * If a non-default value is used PRAGMA kdf_iter to create a database,
-          it must also be called every time that database is opened.
-
-        * It is not recommended to reduce the number of iterations if a
-          passphrase is in use.
-
-        @param db_handle: A handle to the SQLCipher database.
-        @type db_handle: pysqlcipher.Connection
-        @param kdf_iter: The number of iterations to use.
-        @type kdf_iter: int
-        """
-        db_handle.cursor().execute("PRAGMA kdf_iter = '%d'" % kdf_iter)
-
-    @classmethod
-    def _pragma_cipher_page_size(cls, db_handle, cipher_page_size=1024):
-        """
-        Set the page size of the encrypted database.
-
-        SQLCipher 2 introduced the new PRAGMA cipher_page_size that can be
-        used to adjust the page size for the encrypted database. The default
-        page size is 1024 bytes, but it can be desirable for some applications
-        to use a larger page size for increased performance. For instance,
-        some recent testing shows that increasing the page size can noticeably
-        improve performance (5-30%) for certain queries that manipulate a
-        large number of pages (e.g. selects without an index, large inserts in
-        a transaction, big deletes).
-
-        To adjust the page size, call the pragma immediately after setting the
-        key for the first time and each subsequent time that you open the
-        database.
-
-        Implementation Notes:
-
-        * PRAGMA cipher_page_size must be called after PRAGMA key and before
-          the first actual database operation or it will have no effect.
-
-        * If a non-default value is used PRAGMA cipher_page_size to create a
-          database, it must also be called every time that database is opened.
-
-        @param db_handle: A handle to the SQLCipher database.
-        @type db_handle: pysqlcipher.Connection
-        @param cipher_page_size: The page size.
-        @type cipher_page_size: int
-        """
-        db_handle.cursor().execute(
-            "PRAGMA cipher_page_size = '%d'" % cipher_page_size)
-
-    @classmethod
-    def _pragma_rekey(cls, db_handle, new_key, raw_key):
-        """
-        Change the key of an existing encrypted database.
-
-        To change the key on an existing encrypted database, it must first be
-        unlocked with the current encryption key. Once the database is
-        readable and writeable, PRAGMA rekey can be used to re-encrypt every
-        page in the database with a new key.
-
-        * PRAGMA rekey must be called after PRAGMA key. It can be called at any
-          time once the database is readable.
-
-        * PRAGMA rekey can not be used to encrypted a standard SQLite
-          database! It is only useful for changing the key on an existing
-          database.
-
-        * Previous versions of SQLCipher provided a PRAGMA rekey_cipher and
-          code>PRAGMA rekey_kdf_iter. These are deprecated and should not be
-          used. Instead, use sqlcipher_export().
-
-        @param db_handle: A handle to the SQLCipher database.
-        @type db_handle: pysqlcipher.Connection
-        @param new_key: The new key.
-        @type new_key: str
-        @param raw_key: Whether C{password} is a raw 64-char hex string or a
-            passphrase that should be hashed to obtain the encyrption key.
-        @type raw_key: bool
-        """
-        if raw_key:
-            cls._pragma_rekey_raw(db_handle, key)
-        else:
-            cls._pragma_rekey_passphrase(db_handle, key)
-
-    @classmethod
-    def _pragma_rekey_passphrase(cls, db_handle, passphrase):
-        """
-        Change the passphrase for encryption key derivation.
-
-        The key itself can be a passphrase, which is converted to a key using
-        PBKDF2 key derivation. The result is used as the encryption key for
-        the database.
-
-        @param db_handle: A handle to the SQLCipher database.
-        @type db_handle: pysqlcipher.Connection
-        @param passphrase: The passphrase used to derive the encryption key.
-        @type passphrase: str
-        """
-        db_handle.cursor().execute("PRAGMA rekey = '%s'" % passphrase)
-
-    @classmethod
-    def _pragma_rekey_raw(cls, db_handle, key):
-        """
-        Change the raw hexadecimal encryption key.
-
-        It is possible to specify an exact byte sequence using a blob literal.
-        With this method, it is the calling application's responsibility to
-        ensure that the data provided is a 64 character hex string, which will
-        be converted directly to 32 bytes (256 bits) of key data.
-
-        @param db_handle: A handle to the SQLCipher database.
-        @type db_handle: pysqlcipher.Connection
-        @param key: A 64 character hex string.
-        @type key: str
-        """
-        if not all(c in string.hexdigits for c in key):
-            raise NotAnHexString(key)
-        db_handle.cursor().execute('PRAGMA rekey = "x\'%s"' % passphrase)
-
-
-sqlite_backend.SQLiteDatabase.register_implementation(SQLCipherDatabase)