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