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sbxdec.py
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sbxdec.py
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#!/usr/bin/env python3
#--------------------------------------------------------------------------
# SBXDec - Sequenced Box container Decoder
#
# Created: 03/03/2017
#
# Copyright (C) 2017 Marco Pontello - http://mark0.net/
#
# Licence:
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero 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 Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
#--------------------------------------------------------------------------
import os
import sys
import hashlib
import argparse
import binascii
import time
import seqbox
PROGRAM_VER = "1.0.2"
def get_cmdline():
"""Evaluate command line parameters, usage & help."""
parser = argparse.ArgumentParser(
description="decode a SeqBox container",
formatter_class=argparse.ArgumentDefaultsHelpFormatter,
prefix_chars='-+')
parser.add_argument("-v", "--version", action='version',
version='SeqBox - Sequenced Box container - ' +
'Decoder v%s - (C) 2017 by M.Pontello' % PROGRAM_VER)
parser.add_argument("sbxfilename", action="store", help="SBx container")
parser.add_argument("filename", action="store", nargs='?',
help="target/decoded file")
parser.add_argument("-t","--test", action="store_true", default=False,
help="test container integrity")
parser.add_argument("-i", "--info", action="store_true", default=False,
help="show informations/metadata")
parser.add_argument("-c", "--continue", action="store_true", default=False,
help="continue on block errors", dest="cont")
parser.add_argument("-o", "--overwrite", action="store_true", default=False,
help="overwrite existing file")
parser.add_argument("-p", "--password", type=str, default="",
help="encrypt with password", metavar="pass")
res = parser.parse_args()
return res
def errexit(errlev=1, mess=""):
"""Display an error and exit."""
if mess != "":
sys.stderr.write("%s: error: %s\n" %
(os.path.split(sys.argv[0])[1], mess))
sys.exit(errlev)
def lastEofCount(data):
count = 0
for b in range(len(data)):
if data[-b-1] != 0x1a:
break
count +=1
return count
def main():
cmdline = get_cmdline()
sbxfilename = cmdline.sbxfilename
filename = cmdline.filename
if not os.path.exists(sbxfilename):
errexit(1, "sbx file '%s' not found" % (sbxfilename))
sbxfilesize = os.path.getsize(sbxfilename)
print("decoding '%s'..." % (sbxfilename))
fin = open(sbxfilename, "rb", buffering=1024*1024)
#check magic and get version
header = fin.read(4)
fin.seek(0, 0)
if cmdline.password:
e = seqbox.EncDec(cmdline.password, len(header))
header= e.xor(header)
if header[:3] != b"SBx":
errexit(1, "not a SeqBox file!")
sbxver = header[3]
sbx = seqbox.SbxBlock(ver=sbxver, pswd=cmdline.password)
metadata = {}
trimfilesize = False
hashtype = 0
hashlen = 0
hashdigest = b""
hashcheck = False
buffer = fin.read(sbx.blocksize)
try:
sbx.decode(buffer)
except seqbox.SbxDecodeError as err:
if cmdline.cont == False:
print(err)
errexit(errlev=1, mess="invalid block at offset 0x0")
if sbx.blocknum > 1:
errexit(errlev=1, mess="blocks missing or out of order at offset 0x0")
elif sbx.blocknum == 0:
print("metadata block found!")
metadata = sbx.metadata
if "filesize" in metadata:
trimfilesize = True
if "hash" in metadata:
hashtype = metadata["hash"][0]
if hashtype == 0x12:
hashlen = metadata["hash"][1]
hashdigest = metadata["hash"][2:2+hashlen]
hashcheck = True
else:
#first block is data, so reset from the start
print("no metadata available")
fin.seek(0, 0)
#display some info and stop
if cmdline.info:
print("\nSeqBox container info:")
print(" file size: %i bytes" % (sbxfilesize))
print(" blocks: %i" % (sbxfilesize / sbx.blocksize))
print(" version: %i" % (sbx.ver))
print(" UID: %s" % (binascii.hexlify(sbx.uid).decode()))
if metadata:
print("metadata:")
if "sbxname" in metadata:
print(" SBX name : '%s'" % (metadata["sbxname"]))
if "filename" in metadata:
print(" file name: '%s'" % (metadata["filename"]))
if "filesize" in metadata:
print(" file size: %i bytes" % (metadata["filesize"]))
if "sbxdatetime" in metadata:
print(" SBX date&time : %s" %
(time.strftime("%Y-%m-%d %H:%M:%S",
time.localtime(metadata["sbxdatetime"]))))
if "filedatetime" in metadata:
print(" file date&time: %s" %
(time.strftime("%Y-%m-%d %H:%M:%S",
time.localtime(metadata["filedatetime"]))))
if "hash" in metadata:
if hashtype == 0x12:
print(" SHA256: %s" % (binascii.hexlify(
hashdigest).decode()))
else:
print(" hash type not recognized!")
sys.exit(0)
#evaluate target filename
if not cmdline.test:
if not filename:
if "filename" in metadata:
filename = metadata["filename"]
else:
filename = os.path.split(sbxfilename)[1] + ".out"
elif os.path.isdir(filename):
if "filename" in metadata:
filename = os.path.join(filename, metadata["filename"])
else:
filename = os.path.join(filename,
os.path.split(sbxfilename)[1] + ".out")
if os.path.exists(filename) and not cmdline.overwrite:
errexit(1, "target file '%s' already exists!" % (filename))
print("creating file '%s'..." % (filename))
fout= open(filename, "wb", buffering=1024*1024)
if hashtype == 0x12:
d = hashlib.sha256()
lastblocknum = 0
filesize = 0
blockmiss = 0
updatetime = time.time()
while True:
buffer = fin.read(sbx.blocksize)
if len(buffer) < sbx.blocksize:
break
try:
sbx.decode(buffer)
if sbx.blocknum > lastblocknum+1:
if cmdline.cont:
blockmiss += 1
lastblocknum += 1
else:
errexit(errlev=1, mess="block %i out of order or missing"
% (lastblocknum+1))
lastblocknum += 1
if trimfilesize:
filesize += sbx.datasize
if filesize > metadata["filesize"]:
sbx.data = sbx.data[:-(filesize - metadata["filesize"])]
if hashcheck:
d.update(sbx.data)
if not cmdline.test:
fout.write(sbx.data)
except seqbox.SbxDecodeError as err:
if cmdline.cont:
blockmiss += 1
lastblocknum += 1
else:
print(err)
errexit(errlev=1, mess="invalid block at offset %s" %
(hex(fin.tell()-sbx.blocksize)))
#some progress report
if time.time() > updatetime:
print(" %.1f%%" % (fin.tell()*100.0/sbxfilesize),
end="\r", flush=True)
updatetime = time.time() + .1
fin.close()
if not cmdline.test:
fout.close()
if metadata:
if "filedatetime" in metadata:
os.utime(filename,
(int(time.time()), metadata["filedatetime"]))
print("SBX decoding complete")
if blockmiss:
errexit(1, "missing blocks: %i" % blockmiss)
if hashcheck:
if hashtype == 0x12:
print("SHA256", d.hexdigest())
if d.digest() == hashdigest:
print("hash match!")
else:
errexit(1, "hash mismatch! decoded file corrupted!")
else:
print("can't check integrity via hash!")
#if filesize unknown, estimate based on 0x1a padding at block's end
if not trimfilesize:
c = lastEofCount(sbx.data[-4:])
print("EOF markers at the end of last block: %i/4" % c)
if __name__ == '__main__':
main()