forked from BrowserSecurity/ExtensionCrawler
142 lines
4.6 KiB
Python
142 lines
4.6 KiB
Python
#!/usr/bin/env python3
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#
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# Copyright (C) 2016,2017 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 <https://www.gnu.org/licenses/>.
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#
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"""Utility functions for working with Chrome extensionsx archives,
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i.e., *.crx files."""
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import io
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import zipfile
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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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"""Record class for storing crx files."""
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def __init__(self, filename, magic, version, pk_len, sig_len, pk, sig,
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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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"""Check magic matches the magic bytes of the crx specificaton."""
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return magic == b'Cr24'
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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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"""Check validity of signature contained in the crx file."""
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key = RSA.importKey(pk)
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crxhash = SHA.new(data)
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return PKCS1_v1_5.new(key).verify(crxhash, 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,
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header_len, data)
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def print_crx_info(verbose, crx):
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"""Print information extracted from a crx file."""
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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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")")
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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(
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binascii.hexlify(crx.sig)))
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out = io.BytesIO(crx.data)
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ziparchive = zipfile.ZipFile(out, 'r')
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print("Zip content:")
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for info in ziparchive.infolist():
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print('{:8d} {:8d}'.format(info.file_size, info.compress_size),
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info.filename)
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def verify_crxfile(verbose, filename):
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"""Verify integrity of a crx file."""
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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, destdir):
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"""Extract crxfile into specified destdir."""
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crx = read_crx(filename)
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if is_valid_magic(crx.magic) | force:
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if (destdir == "") | (destdir is None):
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destdir = "."
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if filename.endswith(".crx"):
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dirname = filename[0:len(filename) - 4]
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else:
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dirname = filename
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out = io.BytesIO(crx.data)
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ziparchive = zipfile.ZipFile(out, 'r')
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ziparchive.extractall(destdir + "/" + dirname)
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if verbose:
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print("Content extracted into: " + destdir + "/" + dirname)
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return 0
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else:
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print("Input file not valid.")
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return -1
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