[ghjnut]

Could someone do me a solid and explain best security practices around bastion hosts and vpn?

e.g. - would you still require users connected to the vpn to go through a bastion host? - would you ever run bastion/vpn through the same box? - are there preferred access use cases for each?

[tptacek]

Yes, you would still have people connect to the bastion if they're on the VPN; part of the point of a bastion is to have a central place to monitor and control SSH access, which a VPN doesn't really do for you. Additionally, you will inevitably end up with team members who need access to the VPN (to reach staging and test versions of your applications, or to access customer support consoles) but don't get SSH access; a bastion gives you a standard configuration to apply to your fleet to ensure that "on the VPN" doesn't ever equate to "can log into a server".

You should generally do both things.

Wait, I should word that better. You should generally have both sets of controls: network access control with a VPN, and fine-grained, auditable SSH-level access control. I don't love the "Linux shell server" approach to providing those SSH controls.

[ghjnut]

Thanks for the response, that clears things up quite a bit. Would you create jump-boxes per environment or do you generally just have 1 with all the different service/env access logic?

[tptacek]

It depends. It's more important to have some controls in place than to make super-complicated controls. Again: shell servers you SSH into to SSH out of are kind of an anti-pattern. See elsewhere on the thread about Teleport, which, combined with Tailscale, is I think a pretty good answer to these concerns.

[chasil]

I run an "internal" set of bastion hosts that are gateways into a system that runs telnet. This internal system is able to run SSH, but connections stop around 100 because of OS limits. We need to support 400-500 logins, and that has to be telnet. Everybody connecting has to go through these bastions, including VPN users.

I recently built an nspawn container with tinysshd server, with a .profile that execs telnet to the relevant system on login.

We had previously used an old version of Microfocus Reflections (terminal emulation) with stunnels deployed on all the clients and bastions. That was not containerized, but the server stunnels were set to chroot() on startup.

I recently was forced to support the latest version of Reflections, and since it doesn't support chacha-poly, I also built dropbear SSH server just for them. Reflections is very expensive (~$500/seat), and the best that it supports is aes256-ctr, using Tatu Ylonen's commercial ssh.com (which appears to be abandonware). I really hope we can get rid of that.