diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/leap/soledad/client/_crypto.py | 74 | ||||
| -rw-r--r-- | src/leap/soledad/client/_preamble.py | 88 |
2 files changed, 113 insertions, 49 deletions
diff --git a/src/leap/soledad/client/_crypto.py b/src/leap/soledad/client/_crypto.py index 8cedf52e..d0fb6e7f 100644 --- a/src/leap/soledad/client/_crypto.py +++ b/src/leap/soledad/client/_crypto.py @@ -69,11 +69,8 @@ checked during PREAMBLE reading. import base64 import hashlib -import warnings import hmac import os -import struct -import time from io import BytesIO from collections import namedtuple @@ -89,19 +86,14 @@ from cryptography.hazmat.backends import default_backend from zope.interface import implementer +from ._preamble import InvalidPreambleException, decode_preamble, Preamble +from ._preamble import ENC_SCHEME, ENC_METHOD, BLOB_SIGNATURE_MAGIC + SECRET_LENGTH = 64 SEPARATOR = ' ' # Anything that doesn't belong to base64 encoding CRYPTO_BACKEND = default_backend() - -PACMAN = struct.Struct('2sbbQ16s255p255pQ') -LEGACY_PACMAN = struct.Struct('2sbbQ16s255p255p') -BLOB_SIGNATURE_MAGIC = '\x13\x37' - - -ENC_SCHEME = namedtuple('SCHEME', 'symkey')(1) -ENC_METHOD = namedtuple('METHOD', 'aes_256_ctr aes_256_gcm')(1, 2) DocInfo = namedtuple('DocInfo', 'doc_id rev') @@ -288,18 +280,12 @@ class BlobEncryptor(object): return d def _encode_preamble(self): - current_time = int(time.time()) - - preamble = PACMAN.pack( - BLOB_SIGNATURE_MAGIC, - ENC_SCHEME.symkey, - ENC_METHOD.aes_256_gcm, - current_time, - self.iv, - str(self.doc_id), - str(self.rev), - self._content_size) - return preamble + scheme = ENC_SCHEME.symkey + method = ENC_METHOD.aes_256_gcm + content_size = self._content_size + + return Preamble(self.doc_id, self.rev, scheme, method, iv=self.iv, + content_size=content_size).encode() def _end_crypto_stream_and_encode_result(self): @@ -309,10 +295,10 @@ class BlobEncryptor(object): # chunks? # FIXME also, it needs to be able to encode chunks with base64 if armor - preamble, encrypted = self._aes.end() + raw_preamble, encrypted = self._aes.end() result = BytesIO() result.write( - base64.urlsafe_b64encode(preamble)) + base64.urlsafe_b64encode(raw_preamble)) result.write(SEPARATOR) if self.armor: @@ -374,7 +360,7 @@ class BlobDecryptor(object): self.fd.seek(0) try: parts = self.fd.getvalue().split(SEPARATOR, 1) - preamble = base64.urlsafe_b64decode(parts[0]) + encoded_preamble = base64.urlsafe_b64decode(parts[0]) if len(parts) == 2: ciphertext = parts[1] if self.armor: @@ -390,40 +376,30 @@ class BlobDecryptor(object): raise InvalidBlob try: - if len(preamble) == LEGACY_PACMAN.size: - warnings.warn("Decrypting a legacy document without size. " + - "This will be deprecated in 0.12. Doc was: " + - "doc_id: %s rev: %s" % (self.doc_id, self.rev), - Warning) - unpacked_data = LEGACY_PACMAN.unpack(preamble) - magic, sch, meth, ts, iv, doc_id, rev = unpacked_data - elif len(preamble) == PACMAN.size: - unpacked_data = PACMAN.unpack(preamble) - magic, sch, meth, ts, iv, doc_id, rev, doc_size = unpacked_data - self.size = doc_size - else: - raise InvalidBlob("Unexpected preamble size %d", len(preamble)) - except struct.error as e: + preamble = decode_preamble(encoded_preamble) + except InvalidPreambleException as e: raise InvalidBlob(e) - if magic != BLOB_SIGNATURE_MAGIC: + if preamble.magic != BLOB_SIGNATURE_MAGIC: raise InvalidBlob # TODO check timestamp. Just as a sanity check, but for instance # we can refuse to process something that is in the future or # too far in the past (1984 would be nice, hehe) - if sch != ENC_SCHEME.symkey: - raise InvalidBlob('Invalid scheme: %s' % sch) - if meth != ENC_METHOD.aes_256_gcm: - raise InvalidBlob('Invalid encryption scheme: %s' % meth) - if rev != self.rev: + if preamble.scheme != ENC_SCHEME.symkey: + raise InvalidBlob('Invalid scheme: %s' % preamble.scheme) + if preamble.method != ENC_METHOD.aes_256_gcm: + method = preamble.method + raise InvalidBlob('Invalid encryption scheme: %s' % method) + if preamble.rev != self.rev: + rev = preamble.rev msg = 'Invalid revision. Expected: %s, was: %s' % (self.rev, rev) raise InvalidBlob(msg) - if doc_id != self.doc_id: + if preamble.doc_id != self.doc_id: msg = 'Invalid doc_id. ' - + 'Expected: %s, was: %s' % (self.doc_id, doc_id) + + 'Expected: %s, was: %s' % (self.doc_id, preamble.doc_id) raise InvalidBlob(msg) - return preamble, iv + return encoded_preamble, preamble.iv def _end_stream(self): try: diff --git a/src/leap/soledad/client/_preamble.py b/src/leap/soledad/client/_preamble.py new file mode 100644 index 00000000..262d70ce --- /dev/null +++ b/src/leap/soledad/client/_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 <http://www.gnu.org/licenses/>. +""" +Preamble is a metadata payload present on encrypted documents. It holds data +about encryption scheme, iv, document id and sync related data. + BLOB_SIGNATURE_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 +BLOB_SIGNATURE_MAGIC = '\x13\x37' +ENC_SCHEME = namedtuple('SCHEME', 'symkey')(1) +ENC_METHOD = namedtuple('METHOD', 'aes_256_ctr aes_256_gcm')(1, 2) + + +class InvalidPreambleException(Exception): + pass + + +class Preamble: + + 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 BLOB_SIGNATURE_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) |