From eb000dac7a66ea249adb8c9b7d154101b897311c Mon Sep 17 00:00:00 2001 From: Victor Shyba Date: Sat, 8 Jul 2017 05:44:31 -0300 Subject: [refactor] creates a common.blobs with preamble Refactor suggested from !105 review. --- src/leap/soledad/common/blobs/preamble.py | 88 +++++++++++++++++++++++++++++++ 1 file changed, 88 insertions(+) create mode 100644 src/leap/soledad/common/blobs/preamble.py (limited to 'src/leap/soledad/common/blobs/preamble.py') diff --git a/src/leap/soledad/common/blobs/preamble.py b/src/leap/soledad/common/blobs/preamble.py new file mode 100644 index 00000000..d4065c38 --- /dev/null +++ b/src/leap/soledad/common/blobs/preamble.py @@ -0,0 +1,88 @@ +# -*- coding: utf-8 -*- +# preamble.py +# Copyright (C) 2017 LEAP Encryption Access Project +# +# 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 . +""" +Preamble is a binary packed metadata payload present on encrypted documents. It +holds data about encryption scheme, iv, document id and sync related data. + MAGIC, -> used to differentiate from other data formats + ENC_SCHEME, -> cryptographic scheme (symmetric or asymmetric) + ENC_METHOD, -> cipher used, such as AES-GCM or AES-CTR or GPG + current_time, -> time.time() + self.iv, -> initialization vector if any, or 0 when not applicable + str(self.doc_id), -> document id + str(self.rev), -> current revision + self._content_size) -> size, rounded to ceiling +""" +import warnings +import struct +import time +from collections import namedtuple +PACMAN = struct.Struct('2sbbQ16s255p255pQ') +LEGACY_PACMAN = struct.Struct('2sbbQ16s255p255p') # DEPRECATED +MAGIC = '\x13\x37' +ENC_SCHEME = namedtuple('SCHEME', 'symkey external')(1, 2) +ENC_METHOD = namedtuple('METHOD', 'aes_256_ctr aes_256_gcm pgp')(1, 2, 3) + + +class InvalidPreambleException(Exception): + pass + + +class Preamble(object): + + def __init__(self, doc_id, rev, scheme, method, + timestamp=0, iv='', magic=None, content_size=0): + self.doc_id = doc_id + self.rev = rev + self.scheme = scheme + self.method = method + self.iv = iv + self.timestamp = int(timestamp) or int(time.time()) + self.magic = magic or MAGIC + self.content_size = int(content_size) + + def encode(self): + preamble = PACMAN.pack( + self.magic, + self.scheme, + self.method, + self.timestamp, + self.iv, + str(self.doc_id), + str(self.rev), + self.content_size) + return preamble + + +def decode_preamble(encoded_preamble): + preamble_size = len(encoded_preamble) + try: + if preamble_size == LEGACY_PACMAN.size: + unpacked_data = LEGACY_PACMAN.unpack(encoded_preamble) + magic, sch, meth, ts, iv, doc_id, rev = unpacked_data + warnings.warn("Decoding a legacy preamble without size. " + + "This will be deprecated in 0.12. Doc was: " + + "doc_id: %s rev: %s" % (doc_id, rev), Warning) + return Preamble(doc_id, rev, sch, meth, ts, iv, magic) + elif preamble_size == PACMAN.size: + unpacked_data = PACMAN.unpack(encoded_preamble) + magic, sch, meth, ts, iv, doc_id, rev, size = unpacked_data + return Preamble(doc_id, rev, sch, meth, ts, iv, magic, int(size)) + else: + raise InvalidPreambleException("Unexpected preamble size %d", + preamble_size) + except struct.error as e: + raise InvalidPreambleException(e) -- cgit v1.2.3