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Comment by soraminazuki | Hacker News Reader

In this case, double encryption is a good idea though. Tailscale is a great way to reduce exposure of your infrastructure from the public internet, but it’s not without flaws. In theory, it should be possible for Tailscale and your SSO provider to add new nodes to your Tailnet. Though I don’t believe this is something that they’re actually willing to do, it’s definitely something to keep in mind if you’re planning on delegating SSH/sudo authentication to Tailscale.

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Double encryption doesn't actually help in that case though - if tailscale (maliciously) added nodes to your network the ssh session being encrypted wouldn't change the fact that they can run commands on your machines. And if they wanted to actively MITM you they could do so (by redirecting your wireguard connection to a server owned by them) even with encryption (presuming they can fake the host key, which they could do at worst by running code on your server to steal it).

To be clear I implicitly and explicitly trust tailscale not to tamper with my networks and if your threat model includes tailscale becoming a bad actor you should remember that in that case running their binary in the first place could already be game over.

Double encryption should help as long as the Tailscale client installed on your own machines is safe. Without double encryption for SSH, Tailscale and your SSO provider can theoretically run commands on your machines without involving malicious client software. But that's not possible if you encrypt your SSH connection with your own keys.

Also for Linux, the Tailscale client is fully open source and I obtain the binary from the distro. I find that a bit reassuring.

But that's the thing - even with double encryption tailscale and your SSO can run commands on your machines

1) Run tailscale --ssh on your server 2) A malicious SSO or tailscale add a new machine to your network and update your ACL such that the new machine can connect to your server 3) ssh from the new machine to run code on your server

The fact that the connection between the malicious machine and your server is double encrypted doesn't affect the attack here at all

By double encryption, I mean using an SSH server other than "tailscale --ssh". No one except yourself can have SSH access if you disable Tailscale's builtin SSH server, use OpenSSH, and generate your own keys for authentication.

Ah, I don't think that's exactly what this thread was about. Ignoring how authorization works, the question was whether there is an advantage to encrypting your commands again (via say ssh) vs. just sending them in plaintext under wireguard (via say rsh)

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