summaryrefslogtreecommitdiff
path: root/src/leap/soledad/backends/leap_backend.py
blob: 6f1f9546f132a83884cf334de7d8acfc2dc3089f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
# -*- coding: utf-8 -*-
# leap_backend.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 for encrypting data before sending to server and decrypting
after receiving.
"""

try:
    import simplejson as json
except ImportError:
    import json  # noqa


from u1db import Document
from u1db.remote import utils
from u1db.errors import BrokenSyncStream
from u1db.remote.http_target import HTTPSyncTarget


from leap.common.keymanager import KeyManager
from leap.common.check import leap_assert
from leap.soledad.auth import TokenBasedAuth

#
# Exceptions
#

class DocumentNotEncrypted(Exception):
    """
    Raised for failures in document encryption.
    """
    pass


class UnknownEncryptionScheme(Exception):
    """
    Raised when trying to decrypt from unknown encryption schemes.
    """


#
# Encryption schemes used for encryption.
#

class EncryptionSchemes(object):
    """
    Representation of encryption schemes used to encrypt documents.
    """

    NONE = 'none'
    SYMKEY = 'symkey'
    PUBKEY = 'pubkey'


#
# Crypto utilities for a LeapDocument.
#

ENC_JSON_KEY = '_enc_json'
ENC_SCHEME_KEY = '_enc_scheme'


def encrypt_doc(crypto, doc):
    """
    Encrypt C{doc}'s content.

    Return a valid JSON string representing the following:

        {
            ENC_JSON_KEY: '<encrypted doc JSON string>',
            ENC_SCHEME_KEY: 'symkey',
        }

    @param crypto: A SoledadCryto instance used to perform the encryption.
    @type crypto: leap.soledad.crypto.SoledadCrypto
    @param doc: The document with contents to be encrypted.
    @type doc: LeapDocument

    @return: The JSON serialization of the dict representing the encrypted
        content.
    @rtype: str
    """
    leap_assert(doc.is_tombstone() is False)
    # encrypt content
    ciphertext = crypto.encrypt_sym(
        doc.get_json(),
        crypto.passphrase_hash(doc.doc_id))
    # verify it is indeed encrypted
    if not crypto.is_encrypted_sym(ciphertext):
        raise DocumentNotEncrypted('Failed encrypting document.')
    # calculate hmac
    #mac = hmac.new(doc_id,, doc_json, 
    # update doc's content with encrypted version
    return json.dumps({
        ENC_JSON_KEY: ciphertext,
        ENC_SCHEME_KEY: EncryptionSchemes.SYMKEY,
    })


def decrypt_doc(crypto, doc):
    """
    Decrypt C{doc}'s content.

    Return the JSON string representation of the document's decrypted content.

    The content of the document should have the following structure:

        {
            ENC_JSON_KEY: '<enc_blob>',
            ENC_SCHEME_KEY: '<enc_scheme>',
        }

    C{enc_blob} is the encryption of the JSON serialization of the document's
    content. For now Soledad just deals with documents whose C{enc_scheme} is
    EncryptionSchemes.SYMKEY.

    @param crypto: A SoledadCryto instance to perform the encryption.
    @type crypto: leap.soledad.crypto.SoledadCrypto
    @param doc: The document to be decrypted.
    @type doc: LeapDocument

    @return: The JSON serialization of the decrypted content.
    @rtype: str
    """
    leap_assert(doc.is_tombstone() is False)
    leap_assert(ENC_JSON_KEY in doc.content)
    leap_assert(ENC_SCHEME_KEY in doc.content)
    # decrypt doc's content
    ciphertext = doc.content[ENC_JSON_KEY]
    enc_scheme = doc.content[ENC_SCHEME_KEY]
    plainjson = None
    if enc_scheme == EncryptionSchemes.SYMKEY:
        if not crypto.is_encrypted_sym(ciphertext):
            raise DocumentNotEncrypted(
                'Unable to identify document encryption for incoming '
                'document, although it is marked as being encrypted with a '
                'symmetric key.')
        plainjson = crypto.decrypt_sym(
            ciphertext,
            crypto.passphrase_hash(doc.doc_id))
    else:
        raise UnknownEncryptionScheme(enc_scheme)
    return plainjson


class LeapDocument(Document):
    """
    Encryptable and syncable document.

    LEAP Documents can be flagged as syncable or not, so the replicas
    might not sync every document.
    """

    def __init__(self, doc_id=None, rev=None, json='{}', has_conflicts=False,
                 syncable=True):
        """
        Container for handling an encryptable document.

        @param doc_id: The unique document identifier.
        @type doc_id: str
        @param rev: The revision identifier of the document.
        @type rev: str
        @param json: The JSON string for this document.
        @type json: str
        @param has_conflicts: Boolean indicating if this document has conflicts
        @type has_conflicts: bool
        @param syncable: Should this document be synced with remote replicas?
        @type syncable: bool
        """
        Document.__init__(self, doc_id, rev, json, has_conflicts)
        self._syncable = syncable

    def _get_syncable(self):
        """
        Return whether this document is syncable.

        @return: Is this document syncable?
        @rtype: bool
        """
        return self._syncable

    def _set_syncable(self, syncable=True):
        """
        Determine if this document should be synced with remote replicas.

        @param syncable: Should this document be synced with remote replicas?
        @type syncable: bool
        """
        self._syncable = syncable

    syncable = property(
        _get_syncable,
        _set_syncable,
        doc="Determine if document should be synced with server."
    )

    def _get_rev(self):
        """
        Get the document revision.

        Returning the revision as string solves the following exception in
        Twisted web:
            exceptions.TypeError: Can only pass-through bytes on Python 2

        @return: The document revision.
        @rtype: str
        """
        if self._rev is None:
            return None
        return str(self._rev)

    def _set_rev(self, rev):
        """
        Set document revision.

        @param rev: The new document revision.
        @type rev: bytes
        """
        self._rev = rev

    rev = property(
        _get_rev,
        _set_rev,
        doc="Wrapper to ensure `doc.rev` is always returned as bytes.")


#
# LeapSyncTarget
#

class LeapSyncTarget(HTTPSyncTarget, TokenBasedAuth):
    """
    A SyncTarget that encrypts data before sending and decrypts data after
    receiving.
    """

    #
    # Token auth methods.
    #

    def set_token_credentials(self, uuid, token):
        """
        Store given credentials so we can sign the request later.

        @param uuid: The user's uuid.
        @type uuid: str
        @param token: The authentication token.
        @type token: str
        """
        TokenBasedAuth.set_token_credentials(self, uuid, token)

    def _sign_request(self, method, url_query, params):
        """
        Return an authorization header to be included in the HTTP request.

        @param method: The HTTP method.
        @type method: str
        @param url_query: The URL query string.
        @type url_query: str
        @param params: A list with encoded query parameters.
        @type param: list

        @return: The Authorization header.
        @rtype: list of tuple
        """
        return TokenBasedAuth._sign_request(self, method, url_query, params)

    #
    # Modified HTTPSyncTarget methods.
    #

    @staticmethod
    def connect(url, crypto=None):
        return LeapSyncTarget(url, crypto=crypto)

    def __init__(self, url, creds=None, crypto=None):
        """
        Initialize the LeapSyncTarget.

        @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 soledad: An instance of Soledad so we can encrypt/decrypt
            document contents when syncing.
        @type soledad: soledad.Soledad
        """
        HTTPSyncTarget.__init__(self, url, creds)
        self._crypto = crypto

    def _parse_sync_stream(self, data, return_doc_cb, ensure_callback=None):
        """
        Parse incoming synchronization stream and insert documents in the
        local database.

        If an incoming document's encryption scheme is equal to
        EncryptionSchemes.SYMKEY, then this method will decrypt it with
        Soledad's symmetric key.

        @param data: The body of the HTTP response.
        @type data: str
        @param return_doc_cb: A callback to insert docs from target.
        @type return_doc_cb: function
        @param ensure_callback: A callback to ensure we have the correct
            target_replica_uid, if it was just created.
        @type ensure_callback: function

        @raise BrokenSyncStream: If C{data} is malformed.

        @return: A dictionary representing the first line of the response got
            from remote replica.
        @rtype: list of str
        """
        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)
                #-------------------------------------------------------------
                # symmetric decryption of document's contents
                #-------------------------------------------------------------
                # if arriving content was symmetrically encrypted, we decrypt
                # it.
                doc = LeapDocument(entry['id'], entry['rev'], entry['content'])
                if doc.content and ENC_SCHEME_KEY in doc.content:
                    if doc.content[ENC_SCHEME_KEY] == \
                            EncryptionSchemes.SYMKEY:
                        doc.set_json(decrypt_doc(self._crypto, doc))
                #-------------------------------------------------------------
                # end of symmetric decryption
                #-------------------------------------------------------------
                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):
        """
        Find out which documents the remote database does not know about,
        encrypt and send them.

        This does the same as the parent's method but encrypts content before
        syncing.

        @param docs_by_generations: A list of (doc_id, generation, trans_id)
            of local documents that were changed since the last local
            generation the remote replica knows about.
        @type docs_by_generations: list of tuples
        @param source_replica_uid: The uid of the source replica.
        @type source_replica_uid: str
        @param last_known_generation: Target's last known generation.
        @type last_known_generation: int
        @param last_known_trans_id: Target's last known transaction id.
        @type last_known_trans_id: str
        @param return_doc_cb: A callback for inserting received documents from
            target.
        @type return_doc_cb: function
        @param ensure_callback: A callback that ensures we know the target
            replica uid if the target replica was just created.
        @type ensure_callback: function

        @return: The new generation and transaction id of the target replica.
        @rtype: tuple
        """
        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:
            # skip non-syncable docs
            if isinstance(doc, LeapDocument) and not doc.syncable:
                continue
            #-------------------------------------------------------------
            # symmetric encryption of document's contents
            #-------------------------------------------------------------
            doc_json = doc.get_json()
            if not doc.is_tombstone():
                doc_json = encrypt_doc(self._crypto, doc)
            #-------------------------------------------------------------
            # end of symmetric encryption
            #-------------------------------------------------------------
            size += prepare(id=doc.doc_id, rev=doc.rev,
                            content=doc_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']