[refactor] move preamble module to common

This move allows server to use it on #8868 as described in #8890

-- Relates: #8890

2 files changed, 5 insertions, 90 deletions

diff --git a/src/leap/soledad/client/_crypto.py b/src/leap/soledad/client/_crypto.py
index d0fb6e7f..998b70fa 100644
--- a/src/leap/soledad/client/_crypto.py
+++ b/src/leap/soledad/client/_crypto.py
@@ -86,8 +86,11 @@ 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
+from leap.soledad.common.preamble import InvalidPreambleException
+from leap.soledad.common.preamble import decode_preamble
+from leap.soledad.common.preamble import Preamble
+from leap.soledad.common.preamble import ENC_SCHEME, ENC_METHOD
+from leap.soledad.common.preamble import BLOB_SIGNATURE_MAGIC
 
 
 SECRET_LENGTH = 64
diff --git a/src/leap/soledad/client/_preamble.py b/src/leap/soledad/client/_preamble.py
deleted file mode 100644
index 262d70ce..00000000
--- a/src/leap/soledad/client/_preamble.py
+++ /dev/null
@@ -1,88 +0,0 @@
-# -*- 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)