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#!/usr/bin/env python
# Copyright 2016 Sam Yaple
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# Copied and licensed from https://github.com/SamYaple/osdk
from binascii import b2a_hex
from binascii import crc32
from datetime import datetime
from struct import pack
from struct import unpack
from uuid import UUID
class osdk(object):
def __init__(self, manifest):
self.manifest = manifest
self.segments = dict()
self.metadata = dict()
self.metadata['signature'] = \
UUID('d326503ab5ca49adac56c89eb0b8ef08').bytes
self.metadata['version'] = 0
def write_manifest(self):
with open(self.manifest, 'wb') as f:
self.write_header(f)
self.write_body(f)
def build_header(self):
timestamp = utctimestamp()
padding = str.encode('\0\0' * 14)
data = pack(
'<i2IQH14s',
timestamp,
self.metadata['incremental'],
self.metadata['segment_size'],
self.metadata['sectors'],
len(self.metadata['bases']),
padding
)
checksum = crc32(data)
for i in self.metadata['bases']:
data += i
checksum = crc32(i, checksum)
return data, checksum
def write_body(self, f):
checksum = 0
for segment, meta in self.segments.items():
data = pack(
'<2IH2B20s',
segment,
meta['incremental'],
meta['base'],
meta['encryption'],
meta['compression'],
meta['sha1_hash']
)
f.write(data)
checksum = crc32(data, checksum)
""" Backfill the body_checksum """
f.seek(24, 0)
f.write(pack('<I', checksum))
def write_header(self, f):
data, checksum = self.build_header()
f.write(self.metadata['signature'])
f.write(pack('<3I', self.metadata['version'], checksum, 0))
f.write(data)
f.write(self.metadata['signature'])
def read_signature(self, f):
if not self.metadata['signature'] == f.read(16):
raise Exception('File signiture is not valid')
def read_header(self, f):
self.read_signature(f)
data = f.read(12)
if len(data) != 12:
raise Exception('Failed to read amount of requested data')
version, header_checksum, body_checksum = unpack('<3I', data)
if self.metadata['version'] < version:
raise Exception(
'The manifest version is newer than I know how to read'
)
data = f.read(36)
if len(data) != 36:
raise Exception('Failed to read amount of requested data')
checksum = crc32(data)
num_of_bases = ""
padding = ""
self.metadata['timestamp'],
self.metadata['incremental'],
self.metadata['segment_size'],
self.metadata['sectors'],
num_of_bases,
padding = unpack('<i2IQH14s', data)
if padding:
continue
self.metadata['bases'] = []
for i in range(0, num_of_bases):
data = f.read(16)
if len(data) != 16:
raise Exception('Failed to read amount of requested data')
self.metadata['bases'].append(data)
checksum = crc32(data, checksum)
if checksum != header_checksum:
raise Exception('Header checksum does not match')
self.read_signature(f)
return body_checksum
def read_body(self, f, body_checksum):
checksum = 0
data = f.read(32)
while len(data) == 32:
meta = dict()
segment = ""
segment,
meta['incremental'],
meta['base'],
meta['encryption'],
meta['compression'],
sha1 = unpack('<2IH2B20s', data)
meta['sha1_hash'] = b2a_hex(sha1)
self.segments[segment] = meta
checksum = crc32(data, checksum)
data = f.read(32)
if checksum != body_checksum:
raise Exception('Body checksum does not match')
def read_manifest(self, manifest=None):
if manifest:
with open(manifest, 'rb') as f:
body_checksum = self.read_header(f)
self.read_body(f, body_checksum)
else:
with open(self.manifest, 'rb') as f:
body_checksum = self.read_header(f)
self.read_body(f, body_checksum)
def utctimestamp():
ts = datetime.utcnow() - datetime(1970, 1, 1)
return ts.seconds + ts.days * 24 * 3600
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