jw/vma-extractor
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skipping md5 hash verification now also skips hash generation

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Jan Wolff 2020-06-01 19:38:25 +02:00
parent b39dd8901d
commit 389e8518f3
2 changed files with 17 additions and 13 deletions
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2
LICENSE.md
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@ -1,4 +1,4 @@
Copyright (c) 2019 Jan Wolff Copyright (c) 2019-2020 Jan Wolff
This software is provided 'as-is', without any express or implied This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages warranty. In no event will the authors be held liable for any damages

28
vma.py
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@ -7,7 +7,7 @@ import argparse
class VmaHeader(): class VmaHeader():
def __init__(self, fo): def __init__(self, fo, skip_hash):
# 0 - 3: magic # 0 - 3: magic
# VMA magic string ("VMA\x00") # VMA magic string ("VMA\x00")
magic = fo.read(4) magic = fo.read(4)
@ -85,7 +85,10 @@ class VmaHeader():
fo.seek(self.header_size, os.SEEK_SET) fo.seek(self.header_size, os.SEEK_SET)
# reread the header and generate a md5 checksum of the data # reread the header and generate a md5 checksum of the data
self.__gen_md5sum(fo) if skip_hash:
self.generated_md5sum = None
else:
self.generated_md5sum = self.__gen_md5sum(fo)
def __gen_md5sum(self, fo): def __gen_md5sum(self, fo):
@ -97,9 +100,8 @@ class VmaHeader():
data = data[:32] + b'\0' * 16 + data[48:] data = data[:32] + b'\0' * 16 + data[48:]
h.update(data) h.update(data)
self.generated_md5sum = h.digest()
fo.seek(p, os.SEEK_SET) fo.seek(p, os.SEEK_SET)
return h.digest()
class VmaDeviceInfoHeader(): class VmaDeviceInfoHeader():
@ -125,7 +127,7 @@ class VmaDeviceInfoHeader():
class VmaExtentHeader(): class VmaExtentHeader():
def __init__(self, fo, vma_header): def __init__(self, fo, vma_header, skip_hash):
self.pos_start = fo.tell() self.pos_start = fo.tell()
# 0 - 3: magic # 0 - 3: magic
@ -156,7 +158,10 @@ class VmaExtentHeader():
self.pos_end = fo.tell() self.pos_end = fo.tell()
self.__gen_md5sum(fo) if skip_hash:
self.generated_md5sum = None
else:
self.generated_md5sum = self.__gen_md5sum(fo)
def __gen_md5sum(self, fo): def __gen_md5sum(self, fo):
@ -168,9 +173,8 @@ class VmaExtentHeader():
data = data[:24] + b'\0' * 16 + data[40:] data = data[:24] + b'\0' * 16 + data[40:]
h.update(data) h.update(data)
self.generated_md5sum = h.digest()
fo.seek(p, os.SEEK_SET) fo.seek(p, os.SEEK_SET)
return h.digest()
class Blob(): class Blob():
@ -236,11 +240,11 @@ def extract(fo, args):
filesize = fo.tell() filesize = fo.tell()
fo.seek(0, os.SEEK_SET) fo.seek(0, os.SEEK_SET)
vma_header = VmaHeader(fo) vma_header = VmaHeader(fo, args.skip_hash)
# check the md5 checksum given in the header with the value calculated from # check the md5 checksum given in the header with the value calculated from
# the file # the file
if not args.skip_hash: if vma_header.generated_md5sum is not None:
assert vma_header.md5sum == vma_header.generated_md5sum assert vma_header.md5sum == vma_header.generated_md5sum
extract_configs(fo, args, vma_header) extract_configs(fo, args, vma_header)
@ -267,12 +271,12 @@ def extract(fo, args):
while(fo.tell() < filesize): while(fo.tell() < filesize):
# when there is data to read at this point, we can safely expect a full # when there is data to read at this point, we can safely expect a full
# extent header with additional clusters # extent header with additional clusters
extent_header = VmaExtentHeader(fo, vma_header) extent_header = VmaExtentHeader(fo, vma_header, args.skip_hash)
assert vma_header.uuid == extent_header.uuid assert vma_header.uuid == extent_header.uuid
# check the md5 checksum given in the header with the value calculated from # check the md5 checksum given in the header with the value calculated from
# the file # the file
if not args.skip_hash: if extent_header.generated_md5sum is not None:
assert extent_header.md5sum == extent_header.generated_md5sum assert extent_header.md5sum == extent_header.generated_md5sum
for blockinfo in extent_header.blockinfo: for blockinfo in extent_header.blockinfo: