126 lines
4.3 KiB
Python
Executable File
126 lines
4.3 KiB
Python
Executable File
#!/usr/bin/env python3
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#
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# Copyright (C) 2016 The University of Sheffield, UK
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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#
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import argparse
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import binascii
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from Crypto.PublicKey import RSA
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from Crypto.Hash import SHA
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from Crypto.Signature import PKCS1_v1_5
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class CrxFile:
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def __init__(self,filename,magic,version,pk_len,sig_len,pk,sig,header_len,data):
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self.file = filename
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self.magic = magic
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self.version = version
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self.pk_len = pk_len
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self.sig_len = sig_len
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self.pk = pk
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self.sig = sig
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self.header_len = header_len
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self.data = data
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def is_valid_magic(magic):
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return (b'Cr24' == magic)
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def is_crxfile (filename):
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"Check magic number: crx files should start with \"Cr24\"."
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file = open (filename, 'rb')
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magic = file.read(4)
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file.close()
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return is_valid_magic(magic)
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def check_signature(pk,sig,data):
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key = RSA.importKey(pk)
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hash = SHA.new(data)
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return PKCS1_v1_5.new(key).verify(hash, sig)
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def read_crx(filename):
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"Read header of an crx file (https://developer.chrome.com/extensions/crx)."
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file = open (filename, 'rb')
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magic = file.read(4)
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version = int.from_bytes(file.read(4), byteorder='little')
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pk_len = int.from_bytes(file.read(4), byteorder='little')
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sig_len = int.from_bytes(file.read(4), byteorder='little')
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pk = file.read(pk_len)
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sig = file.read(sig_len)
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header_len = 16+pk_len+sig_len
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data = file.read()
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file.close()
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return CrxFile(filename,magic,version,pk_len,sig_len,pk,sig,header_len,data)
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def print_crx_info(verbose,crx):
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if is_valid_magic(crx.magic):
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magic="valid"
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else:
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magic="invalid"
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if check_signature(crx.pk,crx.sig,crx.data):
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sig="valid"
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else:
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sig="invalid"
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print("Filename: "+crx.file)
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print("Header size: "+str(crx.header_len))
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print("Size: "+str(crx.header_len+len(crx.data)))
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print("Magic byte: "+str(crx.magic.decode("utf-8"))+" ("+magic+")")
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print("Version: "+str(crx.version))
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print("Signature: "+sig)
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print("Public Key ["+str(crx.pk_len)+"]:")
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key = RSA.importKey(crx.pk)
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print (key.exportKey().decode("utf-8"))
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if verbose:
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print("Signature ["+str(crx.sig_len)+"]: "+str(binascii.hexlify(crx.sig)))
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def verify_crxfile (verbose, filename):
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if is_crxfile(filename):
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if verbose:
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print("Found correct magic bytes.")
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print_crx_info(verbose,read_crx(filename))
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return 0
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else:
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if verbose:
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print("No valid magic bytes found")
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return -1
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def extract_crxfile(verbose, force, filename):
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print("Not yet implemented: extract crxfile(",verbose,", ", force,", ", filename, ")")
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def main():
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parser = argparse.ArgumentParser()
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parser.add_argument("file", help="chrome extension archive (*.crx)")
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parser.add_argument("-c", "--check", help="verify format and signature of <file>",
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action="store_true")
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parser.add_argument("-e", "--extract", help="extract <file>",
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action="store_true")
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parser.add_argument("-f", "--force", help="apply action also to (potential) invalid files",
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action="store_true")
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parser.add_argument("-v", "--verbose", help="increase verbosity",
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action="store_true")
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args = parser.parse_args()
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if args.extract:
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retval = extract_crxfile(args.verbose, args.force, args.file)
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else:
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retval = verify_crxfile(args.verbose, args.file)
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exit(retval)
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if __name__ == "__main__":
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main()
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