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# Copyright 2011 Canonical Ltd.
#
# This file is part of u1db.
#
# u1db is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License version 3
# as published by the Free Software Foundation.
#
# u1db 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 Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with u1db. If not, see <http://www.gnu.org/licenses/>.
"""A U1DB implementation that uses SQLCipher as its persistence layer."""
import os
from sqlite3 import dbapi2, DatabaseError
import time
from u1db.backends.sqlite_backend import SQLitePartialExpandDatabase
from u1db import (
Document,
errors,
)
def open(path, password, create, document_factory=None):
"""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 create: True/False, should the database be created if it doesn't
already exist?
:param document_factory: A function that will be called with the same
parameters as Document.__init__.
:return: An instance of Database.
"""
return SQLCipherDatabase.open_database(
path, password, create=create, document_factory=document_factory)
class DatabaseIsNotEncrypted(Exception):
"""
Exception raised when trying to open non-encrypted databases.
"""
pass
class SQLCipherDatabase(SQLitePartialExpandDatabase):
"""A U1DB implementation that uses SQLCipher as its persistence layer."""
_index_storage_value = 'expand referenced encrypted'
@classmethod
def set_pragma_key(cls, db_handle, key):
db_handle.cursor().execute("PRAGMA key = '%s'" % key)
def __init__(self, sqlite_file, password, document_factory=None):
"""Create a new sqlcipher file."""
self._check_if_db_is_encrypted(sqlite_file)
self._db_handle = dbapi2.connect(sqlite_file)
SQLCipherDatabase.set_pragma_key(self._db_handle, password)
self._real_replica_uid = None
self._ensure_schema()
self._factory = document_factory or Document
def _check_if_db_is_encrypted(self, sqlite_file):
if not os.path.exists(sqlite_file):
return
else:
try:
# try to open an encrypted database with the regular u1db backend
# should raise a DatabaseError exception.
SQLitePartialExpandDatabase(sqlite_file)
raise DatabaseIsNotEncrypted()
except DatabaseError:
pass
@classmethod
def _open_database(cls, sqlite_file, password, document_factory=None):
if not os.path.isfile(sqlite_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(sqlite_file)
SQLCipherDatabase.set_pragma_key(db_handle, password)
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](
sqlite_file, password, document_factory=document_factory)
@classmethod
def open_database(cls, sqlite_file, password, create, backend_cls=None,
document_factory=None):
try:
return cls._open_database(sqlite_file, password,
document_factory=document_factory)
except errors.DatabaseDoesNotExist:
if not create:
raise
if backend_cls is None:
# default is SQLCipherPartialExpandDatabase
backend_cls = SQLCipherDatabase
return backend_cls(sqlite_file, password,
document_factory=document_factory)
@staticmethod
def register_implementation(klass):
"""Register that we implement an SQLCipherDatabase.
The attribute _index_storage_value will be used as the lookup key.
"""
SQLCipherDatabase._sqlite_registry[klass._index_storage_value] = klass
SQLCipherDatabase.register_implementation(SQLCipherDatabase)
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