146 lines
4.8 KiB
Python
146 lines
4.8 KiB
Python
#!/usr/bin/env python3.7
|
|
#
|
|
# Copyright (C) 2016,2017 The University of Sheffield, UK
|
|
#
|
|
# This program is free software: you can redistribute it and/or modify
|
|
# it under the terms of the GNU 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 General Public License for more details.
|
|
#
|
|
# You should have received a copy of the GNU General Public License
|
|
# along with this program. If not, see <https://www.gnu.org/licenses/>.
|
|
#
|
|
"""Utility functions for working with Chrome extensionsx archives,
|
|
i.e., *.crx files."""
|
|
|
|
import io
|
|
import os
|
|
import zipfile
|
|
import binascii
|
|
from Cryptodome.PublicKey import RSA
|
|
from Cryptodome.Hash import SHA
|
|
from Cryptodome.Signature import PKCS1_v1_5
|
|
|
|
|
|
class CrxFile:
|
|
"""Record class for storing crx files."""
|
|
|
|
def __init__(self, filename, magic, version, public_key_len, sig_len,
|
|
public_key, sig, header_len, data):
|
|
self.file = filename
|
|
self.magic = magic
|
|
self.version = version
|
|
self.public_key_len = public_key_len
|
|
self.sig_len = sig_len
|
|
self.public_key = public_key
|
|
self.sig = sig
|
|
self.header_len = header_len
|
|
self.data = data
|
|
|
|
|
|
def is_valid_magic(magic):
|
|
"""Check magic matches the magic bytes of the crx specificaton."""
|
|
return magic == b'Cr24'
|
|
|
|
|
|
def is_crxfile(filename):
|
|
"""Check magic number: crx files should start with \"Cr24\"."""
|
|
file = open(filename, 'rb')
|
|
magic = file.read(4)
|
|
file.close()
|
|
return is_valid_magic(magic)
|
|
|
|
|
|
def check_signature(public_key, sig, data):
|
|
"""Check validity of signature contained in the crx file."""
|
|
key = RSA.importKey(public_key)
|
|
crxhash = SHA.new(data)
|
|
return PKCS1_v1_5.new(key).verify(crxhash, sig)
|
|
|
|
|
|
def read_crx(filename):
|
|
"""Read header of an crx file (https://developer.chrome.com/extensions/crx)."""
|
|
file = open(filename, 'rb')
|
|
magic = file.read(4)
|
|
version = int.from_bytes(file.read(4), byteorder='little')
|
|
public_key_len = int.from_bytes(file.read(4), byteorder='little')
|
|
sig_len = int.from_bytes(file.read(4), byteorder='little')
|
|
public_key = file.read(public_key_len)
|
|
sig = file.read(sig_len)
|
|
header_len = 16 + public_key_len + sig_len
|
|
data = file.read()
|
|
file.close()
|
|
return CrxFile(filename, magic, version, public_key_len, sig_len,
|
|
public_key, sig, header_len, data)
|
|
|
|
|
|
def print_crx_info(verbose, crx):
|
|
"""Print information extracted from a crx file."""
|
|
if is_valid_magic(crx.magic):
|
|
magic = "valid"
|
|
else:
|
|
magic = "invalid"
|
|
if check_signature(crx.public_key, crx.sig, crx.data):
|
|
sig = "valid"
|
|
else:
|
|
sig = "invalid"
|
|
print("Filename: " + crx.file)
|
|
print("Header size: " + str(crx.header_len))
|
|
print("Size: " + str(crx.header_len + len(crx.data)))
|
|
print("Magic byte: " + str(crx.magic.decode("utf-8")) + " (" + magic +
|
|
")")
|
|
print("Version: " + str(crx.version))
|
|
print("Signature: " + sig)
|
|
print("Public Key [" + str(crx.public_key_len) + "]:")
|
|
key = RSA.importKey(crx.public_key)
|
|
print(key.exportKey().decode("utf-8"))
|
|
if verbose:
|
|
print("Signature [" + str(crx.sig_len) + "]: " + str(
|
|
binascii.hexlify(crx.sig)))
|
|
out = io.BytesIO(crx.data)
|
|
ziparchive = zipfile.ZipFile(out, 'r')
|
|
print("Zip content:")
|
|
for info in ziparchive.infolist():
|
|
print('{:8d} {:8d}'.format(info.file_size, info.compress_size),
|
|
info.filename)
|
|
|
|
|
|
def verify_crxfile(verbose, filename):
|
|
"""Verify integrity of a crx file."""
|
|
if is_crxfile(filename):
|
|
if verbose:
|
|
print("Found correct magic bytes.")
|
|
print_crx_info(verbose, read_crx(filename))
|
|
return 0
|
|
else:
|
|
if verbose:
|
|
print("No valid magic bytes found")
|
|
return -1
|
|
|
|
|
|
def extract_crxfile(verbose, force, filename, destdir):
|
|
"""Extract crxfile into specified destdir."""
|
|
crx = read_crx(filename)
|
|
if is_valid_magic(crx.magic) | force:
|
|
if (destdir == "") | (destdir is None):
|
|
destdir = "."
|
|
if filename.endswith(".crx"):
|
|
extname = os.path.basename(filename)
|
|
dirname = extname[0:len(os.path.basename(extname)) - 4]
|
|
else:
|
|
dirname = filename
|
|
out = io.BytesIO(crx.data)
|
|
ziparchive = zipfile.ZipFile(out, 'r')
|
|
ziparchive.extractall(destdir + "/" + dirname)
|
|
if verbose:
|
|
print("Content extracted into: " + destdir + "/" + dirname)
|
|
return 0
|
|
else:
|
|
print("Input file not valid.")
|
|
return -1
|