Get ZIP file from Chrome CRX extension format

crx.py

# Because I was on Windows, without dd :)

import os
import struct
import sys


if len(sys.argv) != 3:
	print "Usage:", sys.argv[0], "<crx file> <zip file>"
	exit(0)

crx = open(sys.argv[1], "rb")

if crx.read(4) == "Cr24":
    print "CRX File"
else:
    print "Not a CRX File!"
    exit(0)

version, pk_length, sig_length = struct.unpack("<lll", crx.read(4 * 3))
print "Version:", version
print "Public key length:", pk_length
print "Signature length:", sig_length

crx.seek(pk_length + sig_length, os.SEEK_CUR)

zip_offset = crx.tell()

print "Zip offset:", zip_offset, "({0})".format(hex(zip_offset))

crx.seek(0, os.SEEK_END)
file_size = crx.tell()

zip_size = file_size - zip_offset
print "Zip size:", zip_size, "({0})".format(hex(zip_size))

crx.seek(zip_offset, os.SEEK_SET)
open(sys.argv[2], "wb").write(crx.read(zip_size))