crx-unpack 0.1.4

Unpack .crx files the way Chrome does

This module contains several utilities for working with Google Chrome extension files (CRXs), which have the *.crx file extension. The goal of this project is to mimic as closely as possible the functionality of Google Chrome when these extensions are unpacked and installed.

Documentation

Please view the full documentation for this project on Read the Docs.

Installation

Since crx_unpack is available on PyPI, you can install it using pip:

$ pip install crx_unpack

Structure of CRX Package Format

The information in this section introduces the structure and contents of CRX files.

As explained at https://developer.chrome.com/extensions/crx

Package Header

The header contains the author’s public key and the extension’s signature. The signature is generated from the ZIP file using SHA-1 with the author’s private key. The header requires a little-endian byte ordering with 4-byte alignment. The following table describes the fields of the .crx header in order:

Field	Type	Length	Value	Description
magic number	char[]	32 bits	Cr24	Chrome requires this constant at the beginning of every .crx package.
version	unsigned int	32 bits	2	The version of the *.crx file format used (currently 2).
public key length	unsigned int	32 bits	pubkey.length	The length of the RSA public key in bytes.
signature length	unsigned int	32 bits	sig.length	The length of the signature in bytes.
public key	byte[]	pubkey.length	pubkey.contents	The contents of the author’s RSA public key formatted as an X509 SubjectPublicKeyInfo block.
signature	byte[]	sig.length	sig.contents	The signature of the ZIP content using the author’s private key. The signature is created using the RSA algorithm with the SHA-1 hash function.

Extension Contents

The extension’s ZIP file is appended to the *.crx package after the header. This should be the same ZIP file that the signature in the header was generated from.