self-unzip.html

This repo contains tools to create self-extracting HTML pages. It works by taking a payload, compressing it, and encoding the results using ASCII85. It then puts the resulting string in a template file, that contains the code to decode and decompress the payload again.

Currently there are three actions implemented, that can be executed, after the payload is decoded:

• eval: Execute payload as JavaScript code (example usecase: obfuscate malicious JS code)
• replace: Show payload as HTML page (example usecase: compress a big web page)
• download: Download the payload as a file (example usecase: bypass antivirus / filters)

Demo

You can try the online demo at self-extracting-html.six-two.dev. This version is the same as the web version described below. It is entirely client-site, your files do not get uploaded to a server.

Installation

Current feature comparision

Currently the python version has the most features.

Feature	Web version	Python version
Base64 encoding	no	yes
Ascii85 encoding	yes	yes
GZIP compression	yes, always	yes, can be disabled
AES-GCM encryption	no	yes
Automatic detection of most efficient algorithms	no	yes

Web version

There is a bare-bones page generator written in plain HTML and JavaScript. To use it, just clone the repo and put the contents of the site directory somewhere in your web server directory.

You can of course also use it with Python's built in web server:

python3 -m http.server --directory ./site/

Python version

A Python script to generate self extracting web pages is under python/main.py. It just requires a modern Python version (probably Python3.9+) and has no required external dependencies (but you need to install pycryptodomex if you want to encrypt contents).

You can also install it with pip:

python3 -m pip install -U self-unzip-html

Example usage of the pip package:

self-unzip-html -t download -o psexec.html ~/Downloads/SysinternalsSuite/PsExec.exe

Or if you wanted to password-protect it:

self-unzip-html -t download -o psexec.html -p YourPasswordHere ~/Downloads/SysinternalsSuite/PsExec.exe

Encryption

Encryption uses AES-GCM for encryption and tamper detection and PBKDF2 with slightly over 1 million rounds of SHA-256 for password derivation. The code has not been audited, so use it with caution. If data security is very important to you may want to manually encrypt it beforehand (for example using gpg).

You can automatically decrypt a page by adding the password as the hash in a URL like encrypted.html#monkey123!. The hash will not be sent to the server, so your password may only be stored locally (in your browsing history). Otherwise a prompt will ask you for the password.

JavaScript code

Python

The JavaScript code is modular to decrease size and allow mixing and matching different algorithms. The unminified files are in code_to_minify/. They are minified by running code_to_minify/build.sh, which updates python/self_unzip_html/minified_js.py.

template.html

This basically just explains, how I generated the obfuscated script in template.html (JavaScript version). In case you are paranoid, you can reproduce the steps. Or if there is an important update to fflate or ascii85, I will have to run them again.

Install with npm:

npm install .

First use rollup to only select the actually used code:

./node_modules/.bin/rollup -c rollup.config.js

This command should create output/main.js

The next step is optional. If you want to skip it, just rename main.min.js to main.js in the output directory. Otherwise minify the code (may require you to install an external minifier like closure-compiler).

closure-compiler output/main.js --js_output_file output/main.min.js