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"""
A U1DB backend that encrypts data before sending to server and decrypts after
receiving.
"""
try:
import simplejson as json
except ImportError:
import json # noqa
from u1db import Document
from u1db.remote import utils
from u1db.remote.http_target import HTTPSyncTarget
from u1db.remote.http_database import HTTPDatabase
from u1db.errors import BrokenSyncStream
import uuid
class NoDefaultKey(Exception):
"""
Exception to signal that there's no default OpenPGP key configured.
"""
pass
class NoSoledadInstance(Exception):
"""
Exception to signal that no Soledad instance was found.
"""
pass
class DocumentNotEncrypted(Exception):
"""
Exception to signal failures in document encryption.
"""
pass
class LeapDocument(Document):
"""
Encryptable and syncable document.
LEAP Documents are standard u1db documents with cabability of returning an
encrypted version of the document json string as well as setting document
content based on an encrypted version of json string.
"""
def __init__(self, doc_id=None, rev=None, json='{}', has_conflicts=False,
encrypted_json=None, soledad=None, syncable=True):
super(LeapDocument, self).__init__(doc_id, rev, json, has_conflicts)
self._soledad = soledad
self._syncable = syncable
if encrypted_json:
self.set_encrypted_json(encrypted_json)
def get_encrypted_content(self):
"""
Return an encrypted JSON serialization of document's contents.
"""
if not self._soledad:
raise NoSoledadInstance()
return self._soledad.encrypt_symmetric(self.doc_id,
self.get_json())
def set_encrypted_content(self, cyphertext):
"""
Set document's content based on an encrypted JSON serialization of
contents.
"""
plaintext = self._soledad.decrypt_symmetric(self.doc_id, cyphertext)
return self.set_json(plaintext)
def get_encrypted_json(self):
"""
Return a valid JSON string containing document's content encrypted to
the user's public key.
"""
return json.dumps({'_encrypted_json': self.get_encrypted_content()})
def set_encrypted_json(self, encrypted_json):
"""
Set document's content based on a valid JSON string containing the
encrypted document's contents.
"""
if not self._soledad:
raise NoSoledadInstance()
cyphertext = json.loads(encrypted_json)['_encrypted_json']
self.set_encrypted_content(cyphertext)
def _get_syncable(self):
return self._syncable
def _set_syncable(self, syncable=True):
self._syncable = syncable
syncable = property(
_get_syncable,
_set_syncable,
doc="Determine if document should be synced with server."
)
# Returning the revision as string solves the following exception in
# Twisted web:
# exceptions.TypeError: Can only pass-through bytes on Python 2
def _get_rev(self):
if self._rev is None:
return None
return str(self._rev)
def _set_rev(self, rev):
self._rev = rev
rev = property(
_get_rev,
_set_rev,
doc="Wrapper to ensure `doc.rev` is always returned as bytes.")
class LeapSyncTarget(HTTPSyncTarget):
"""
A SyncTarget that encrypts data before sending and decrypts data after
receiving.
"""
def __init__(self, url, creds=None, soledad=None):
super(LeapSyncTarget, self).__init__(url, creds)
self._soledad = soledad
def _parse_sync_stream(self, data, return_doc_cb, ensure_callback=None):
"""
Does the same as parent's method but ensures incoming content will be
decrypted.
"""
parts = data.splitlines() # one at a time
if not parts or parts[0] != '[':
raise BrokenSyncStream
data = parts[1:-1]
comma = False
if data:
line, comma = utils.check_and_strip_comma(data[0])
res = json.loads(line)
if ensure_callback and 'replica_uid' in res:
ensure_callback(res['replica_uid'])
for entry in data[1:]:
if not comma: # missing in between comma
raise BrokenSyncStream
line, comma = utils.check_and_strip_comma(entry)
entry = json.loads(line)
# decrypt after receiving from server.
if not self._soledad:
raise NoSoledadInstance()
enc_json = json.loads(entry['content'])['_encrypted_json']
if not self._soledad.is_encrypted_sym(enc_json):
raise DocumentNotEncrypted(
"Incoming document from sync is not encrypted.")
doc = LeapDocument(entry['id'], entry['rev'],
encrypted_json=entry['content'],
soledad=self._soledad)
return_doc_cb(doc, entry['gen'], entry['trans_id'])
if parts[-1] != ']':
try:
partdic = json.loads(parts[-1])
except ValueError:
pass
else:
if isinstance(partdic, dict):
self._error(partdic)
raise BrokenSyncStream
if not data or comma: # no entries or bad extra comma
raise BrokenSyncStream
return res
def sync_exchange(self, docs_by_generations, source_replica_uid,
last_known_generation, last_known_trans_id,
return_doc_cb, ensure_callback=None):
"""
Does the same as parent's method but encrypts content before syncing.
"""
self._ensure_connection()
if self._trace_hook: # for tests
self._trace_hook('sync_exchange')
url = '%s/sync-from/%s' % (self._url.path, source_replica_uid)
self._conn.putrequest('POST', url)
self._conn.putheader('content-type', 'application/x-u1db-sync-stream')
for header_name, header_value in self._sign_request('POST', url, {}):
self._conn.putheader(header_name, header_value)
entries = ['[']
size = 1
def prepare(**dic):
entry = comma + '\r\n' + json.dumps(dic)
entries.append(entry)
return len(entry)
comma = ''
size += prepare(
last_known_generation=last_known_generation,
last_known_trans_id=last_known_trans_id,
ensure=ensure_callback is not None)
comma = ','
for doc, gen, trans_id in docs_by_generations:
if doc.syncable:
# encrypt and verify before sending to server.
enc_json = json.loads(
doc.get_encrypted_json())['_encrypted_json']
if not self._soledad.is_encrypted_sym(enc_json):
raise DocumentNotEncrypted(
"Could not encrypt document before sync.")
size += prepare(id=doc.doc_id, rev=doc.rev,
content=doc.get_encrypted_json(),
gen=gen, trans_id=trans_id)
entries.append('\r\n]')
size += len(entries[-1])
self._conn.putheader('content-length', str(size))
self._conn.endheaders()
for entry in entries:
self._conn.send(entry)
entries = None
data, _ = self._response()
res = self._parse_sync_stream(data, return_doc_cb, ensure_callback)
data = None
return res['new_generation'], res['new_transaction_id']
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