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Do you run a private CA? Could you tell me about your certificate setup if you do?

Hi, I was looking at private CAs since I don't want to pay for a domain to use in my homelab.

What is everyone using for their private CA? I've been looking at plain OpenSSL with some automation scripts but would like more ideas. Also, if you have multiple reverse-proxy instances, how do you distribute domain-specific signed certificates to them? I'm not planning to use a wildcard, and would like to rotate certificates often.

Thanks!

Edit: thank you for everyone who commented! I would like to say that I recognise the technical difficulty in getting such a setup working compared to a simple certbot setup to Let's Encrypt, but it's a personal choice that I have made.

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  • I'm not using a private CA for my internal services, just plain self-signed certs. But if I had to, I would probably go as simple as possible in the first time: generate the CA cert using ansible, use ansible to automate signing of all my certs by the CA cert. The openssl_* modules make this easy enough. This is not very different from my current self-signed setup, the benefit is that I'd only have to trust a single CA certificate/bypass a single certificate warning, instead of getting a warning for every single certificate/domain.

    If I wanted to rotate certificates frequently, I'd look into setting up an ACME server like [1], and point mod_md or certbot to it, instead of the default letsencrypt endpoint.

    This still does not solve the problem of how to get your clients to trust your private CA. There are dozens of different mechanisms to get a certificate into the trust store. On Linux machines this is easy enough (add the CA cert to /usr/local/share/ca-certificates/*.crt, run update-ca-certificates), but other operating systems use different methods (ever tried adding a custom CA cert on Android? it's painful. Do other OS even allow it?). Then some apps (Web browsers for example) use their own CA cert store, which is different from the OS... What about clients you don't have admin access to? etc.

    So for simplicity's sake, if I really wanted valid certs for my internal services, I'd use subdomains of an actual, purchased (more like renting...) domain name (e.g. service-name.internal.example.org), and get the certs from Let's Encrypt (using DNS challenge, or HTTP challenge on a public-facing server and sync the certificates to the actual servers that needs them). It's not ideal, but still better than the certificate racket system we had before Let's Encrypt.

    • Finally got around to replying to the comments I got haha!

      Thanks for the explanation. I'm curious why you're not running your own CA since that seems to be a more seamless process than having to deal with ugly SSL errors for every website, every time you rotate the certificate.

      I'm wondering about different the process is between running an ACME server and another daemon/process like certbot to pull certificates from it, vs writing an ansible playbook/simple shell script to automate the rotation of server certificates.

      About my clients: I am likely never going to purchase Apple products since I recognise how much they lock down their device. Unfortunately, there are not that many android devices in the US with custom ROM support. With that said, I do plan to root all of my Android devices when KernelSU matures (in about a year, I think) - I'm currently reading up on how to insert a root and client certificate into Android's certificate store, but I think it's definitely possible. Other than that, I might have a throwaway Windows VM sometimes, which is doable, alongside a Void linux box with a Debian chroot. All in all, fairly doable, just a bit of work to automate.

      Thanks!

      • I’m curious why you’re not running your own CA since that seems to be a more seamless process than having to deal with ugly SSL errors for every website

        It's not, it's another service to deploy, maintain, monitor, backup and troubleshoot. The ugly SSL warning only appears once, I check the certificate fingerprint and bypass the warning, from there it's smooth sailing. The certificate is pinned, so if it ever changes I would get a new warning and would know something shady is going on.

        every time you rotate the certificate.

        I don't really rotate these certs, they have a validity of several years.

        I’m wondering about different the process is between running an ACME server and another daemon/process like certbot to pull certificates from it, vs writing an ansible playbook/simple shell script to automate the rotation of server certificates.

        • Generating self-signed certs is ~40 lines of clean ansible [1], 2 lines of apache config, and one click to get through the self-signed cert warning, once.
        • Obtaining Let's Encrypt certs is 2 lines of apache config with mod_md and the HTTP-01 challenge. But it requires a domain name in the public DNS, and port forwarding.
        • Obtaining certs from a custom ACME CA is 3 lines of apache config (the extra line is to change the ACME endpoint) and a 100k LOC ACME server daemon running somewhere with its own bugs, documentation, deployment and upgrade management tooling, config quirks... and you still have to manage certs for this service. It may be worth it if you have a lot of clients who don't want to see the self-signed cert warning and/or worry about their private keys being compromised and thus needing to rotate the certs frequently (you still need to protect the CA key...)

        likely never going to purchase Apple products since I recognise how much they lock down their device

        hear hear

        there are not that many android devices in the US with custom ROM support. With that said, I do plan to root all of my Android devices when KernelSU mature

        I bought a cheap refurbished Samsung, installed LineageOS on it (Europe, but I don't see why it wouldn't work in the US?), without root - I don't really need root, it's a security liability, and I think the last time I tried Magisk it didn't work. The only downside is that I have to manually tap Update for F-Droid updates to run (fully unattended requires root).

        I’m currently reading up on how to insert a root and client certificate into Android’s certificate store, but I think it’s definitely possible.

        I did it on that LineageOS phone, using adb push, can't remember how exactly (did it require root? I don't know). It works but you get a permanent warning in your notifications telling you that The network might be monitored or something. But some apps would still ignore it.

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