Securely Expose your Homelab Services with Mutual TLS

Tried it and it was a breeze to set it up with Caddy!

Problem was... lack of client side support, specially on mobile.

Many (most?) client apps don't support it.

Use the PWA from your browser, you said? I hope you like Google and using Chrome, because Firefox for Android doesn't support it (mTLS) 😭 (for now, see replies)

The client cert management is the biggest hurdle with mTLS - I've found using a YubiKey to store certs makes it wayy more portable across devices, tho still doesn't solve the mobile app support issue.
Firefox for Android partially supports PWAs.
- Oh, I meant mutual TLS by "it". Edited.
I was curious so I looked it up.. But it should technically work on FF for Android, although there is a bug in the UI.
See:
https://connect.mozilla.org/t5/ideas/allow-personal-certificates-in-firefox-mobile/idi-p/176
- That's no bug, mTLS just isn't implemented on Firefox (for Android) currently.
  There are 2 proposed solutions on that thread:
  It was possible on old versions of FF, but not the current ones. I believe this to be related to the versions prior to the revamp that happened circa 2020. (the author refers to a version that was already "old" by 2022). So it was something supported on OG Firefox, not not on the new (current, by 5 years already) version.
  Using the debug menu's secret settings to enable "Use third party CA certificates". This is available on current FF, but that's no mutual TLS. It is about allowing CA certificates that you installed yourself on your device for server TLS auth.

I haven't watched the video yet, but it's generally not worth the hassle of setting up mutual TLS if you're already using a peer-to-peer VPN like Tailscale, as the VPN software is already doing mutual authentication.

Edit: A peer-to-peer VPN (or mesh VPN) is one where two systems that are connected to the VPN can directly communicate with each other, instead of needing to go through a central server as with something like OpenVPN. With Tailscale or Wireguard, the peers need each other's public keys to communicate.

This is only true for the connection security. With mTLS you can also authenticate to the webapplication you're trying to reach. So consider your use-case between vpn/mtls.
- Oh yeah that's a great point I didn't consider. Thanks.
The whole point of mTLS is that you dont need to use a VPN to achieve that same security.
- I get that, but a lot of people are already using a VPN to access their self-hosted system.
- that's not that same security. an observer will still know that you are connecting over HTTPS to a particular doman/IP, maybe they can also deduce that you are using mTLS, and all your other traffic is not protected by it at all. all the while with wireguard, they can see that it's wireguard traffic, and where it goes, but anything inside is secret, plus if an app uses unencrypted traffic for some reason (smb, dns, custom and special protocols), wireguard will hide and protect that too.

mTLS is so cool, until you find out that almost no clients support it.

Immich supports it.

I tried long ago, but as they said, client side authentication is an issue, most clients do not support it.

I have a system, I use wireguard vpn and for when I want to use a domain name with proper tls (because some client apps require a proper tls connection to work) I set my caddy reverse proxy to only accept request from ~~localhost~~ local network.

So, there's a public domain with let's encrypt TLS, and that domain can only be properly access from local network. Then I connect using vpn to my local network and the client app can access the service over a CA verified TLS.

I set my caddy reverse proxy to only accept request from localhost.
It is a bit more involved but you can actually get a proper cert for localhost stuff, with your domain pointing to an internal ip addr and not risk exposing your public ip and having to open a port.
- Signed by a AC?
  I had a lot of issues with some apps not allowing self-signed certificates and the app used their own list of allowed AC or something, I was unable to make it allow my own certificates even adding my own root certificate to Android.
From localhost? Did you mean from local network or am I misunderstanding your point here?
- Yes, local network I meant.

I didn't know what this was until now. It seems like the beta bitwarden app supports this. Would be interesting to get it setup for that.