It can be interesting to unpack Electron apps to see how they function or just generally try to reimplement a feature in a different language.
You’ll first need to open up the application itself which varies from platform to platform. In our case, we’ll have a look at the Obsidian macOS app as an example.
$ cd /Applications/Obsidian.app/Contents
CodeResources Info.plist PkgInfo _CodeSignature
Frameworks MacOS Resources
$ grep 'ElectronAsar' Info.plist -A 2
The thing that we’re after is an
asar file which is effectively just a
tar.gz file by another name.
Here we can see that we need to navigate into the Resources folder to get our hands on
$ cd Resources
$ ls -la | grep .asar
-rw-r--r--@ 1 marcus admin 948879 10 May 03:35 app.asar
drwxr-xr-x@ 3 marcus admin 96 10 May 03:35 app.asar.unpacked
-rwxr-xr-x@ 1 marcus admin 18912821 10 May 03:35 obsidian.asar
We have two
.asar files which may or may not be the case for whatever you’re looking for.
We’ll want to grab the bigger
obsidian.asar as that’s where all of the content actually lives but again, this may differ between applications.
Unpacking the asar file is pretty straightforward using the
asar npm package. Let’s extract this file to desktop.
$ cd ~/Desktop
$ npx @electron/asar extract /Applications/Obsidian.app/Contents/Resources/obsidian.asar obsidian-unpack
$ ls obsidian-unpack
app.css i18n main.js sim.js
app.js i18n.js package-lock.json starter.html
enhance.js icon.png package.json starter.js
help.html index.html public worker.js
help.js lib sandbox
While you shouldn’t use this to cause too much trouble, I didn’t feel too bad using Obsidian as an example. While it is closed source, it’s not that much effort to pop open Chrome DevTools and poke around those same files.
Everything is all minified and uglified too. Not exactly a security measure (nor is it intended to be) but most of the effort in poking around is interpreting all this nonsense rather than actually unpacking it in the first place.
Once that’s done, you can also repack the asar file like so:
$ npx @electron/asar pack obsidian-unpack obsidian.asar