RFC: https_proxy extension: initial commit

[EvilOlaf]

Description

This is a draft/wip for adding https proxy caching. This is especially designed for machines hosting lots of github runners to reduce their bandwidth usage by sacrificing disk space. http caching has been merged already and only needed minor changes.

Caching https however is way more complicated. Encryption needs to be broken and rewrapped and then obviously downloads will fail due to cert issues. Classic MITM. So a new certificate authority (CA) needs to be put in place to allow these "fake" certs.

Why is this even necessary? Well one major part is downloads from upstream apt repositories. The other major part is downloading 3rd party repositories and artifacts from OCI/ORAS/whatever the correct name for that system is. They do not allow plain http downloads but redirect to https. So in order to cache these encryption must be broken on the fly.

On custom runs this works already with the mentioned extension. However when the build framework is used within a GH Actions Runner environment it would need to detect this and enable the extension automatically. No clue how to do that or overall if it is worth diving even deeper into this topic. Therefore this RFC to collect feedback.

Also lots of fail-safe checks are missing. Sometimes I had to mix run_host_command_logged and chroot_sdcard since pipes don't work using latter.

Documentation summary for feature / change

Yes, this would need documentation.

How Has This Been Tested?

• [x] custom builds with ENABLE_EXTENSION
• [ ] Test B

Checklist:

• [no idea] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] My changes generate no new warnings
• [ ] Any dependent changes have been merged and published in downstream modules

[coderabbitai[bot]]

Walkthrough

A new Bash script, https_proxy.sh, has been added to manage HTTPS proxy configuration using Squid with SSL bumping and a self-signed certificate. The script introduces three main functions: one to prepare the host system by installing the Squid CA certificate, another to set up the certificate inside a chroot environment before image customization, and a third to clean up the certificate from the chroot after customization. The script utilizes helper functions for command execution and logging, and includes comments regarding prerequisites and future improvements. A function for host certificate removal is present but commented out.

✨ Finishing Touches

• [ ] 📝 Generate Docstrings

🧪 Generate Unit Tests

• [ ] Create PR with Unit Tests
• [ ] Commit Unit Tests in branch https
• [ ] Post Copyable Unit Tests in Comment

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[EvilOlaf]

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[coderabbitai[bot]]

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[leggewie]

I very much support this idea!

I suggest you have a look at how apt-cacher-ng does this. Essentially, you tell your build host to connect to the proxy instance over http but the proxy then connects to the proper server over https. That way, the artifacts are cacheable. It might even make sense for armbian to set up an artifact cache somewhere on the internet specifically to be served over http instead of https. Artifacts of course should then be protected with hashes.

I also suggest to look into making this work more easily out of the box with detection of LAN proxies the way that squid-deb-proxy-client does it via Avahi zeroconf.

[EvilOlaf]

I did not work on this since then. Caching apt packages is good enough for me for now which does not need any adjustments except passing some env variables. Feel free to dig further (and ideally come up with something not totally messy and hacked together lol)