Tailscale SSH: Investigation and remediation update

Former tailscalar here and now someone managing tailscale at an org.

Having done my own review of the vulns and the fixes as they are landing in github, its pretty clear to me that this only affects situations where you use ACLs to permit ssh into a node (via tailscale ssh, not via opensshd), but dont give a path to sudoers/root.

If a user had no SSH access and/or connectivity to a vulnerable node, none of these vulns give them access.

However, if you have a vulnerable tailscaled and you give ssh access as some non-root account/privs, then yes, these vulns are relevant as theres now known privilege escalations that give access beyond some specific user account.

Not trying to play down the vuln (its important), but its not a free-for-all RCE that some ppl are acting like it is.

I am fairly glad I have stuck with stock OpenSSH that ships with Linux. This incident proves I am glad with that choice.

Over the decades, I have maintained remote access through port forwarding on my router - at one point in 2008 I put SSH on port 80 so I could access it from the restricted wifi network at the hospital my grandmother was at. I have also used openvpn. I have also used cloudflare tunnels. But in the end, I always connect to hardened openssh with key only authentication.

Somehow I don't think it's a good idea to let Tailscale handle service authentication at all. It's supposed to be an additional security layer around existing infrastructure and services.

Letting Tailscale handle VPN and SSH at the same time is basically once again a single point of failure. Similar to exposing SSH directly to the internet.

The amount of people claiming to be happy to have never gotten on the Tailscale (or other virtual network layer like Nebula) boat is too damn high. Remember people, it's just a layer. I.e. GitLab seems to have a new set of critical CVEs every week now, and I have been glad to have Tailscale (plus a physical firewall) as a layer in front of it. Total stress level would have been higher without Tailscale.

And before people start coming up with alternatives, I know, but they either have the same (theoretical level of) attack surface (ie [managed] Nebula), or they require much more manual work (ie Wireguard) and are therefore more sensitive to misconfiguration.

There are too many features, and lines of code (probably more than OpenVPN). I'm pretty sure there are all kinds of zero days in it, with this attack surface and feature set.

I use it extensively, and I would rather pay them a fee if they could review thr code.

A possibility is a lock down mode, disabling risky features.

I just want a VPN for connrctiviy, no taildrop, taildrive, SSH, funnel, services, DNS, node sharing, ...They are disabled in my admin console, but the code runs on my devices and they can be enabled by mistake.

A question. Taildrop enables unauthenticated input and doesn't even obey ACLs. I'm not quite sure about this, but couldn't malware in a low trust device send a file to my Synology NAS, which will then automatically process it for indexing things like thumbnail, leading to potential code execution? Why doesn't it obey ACLs, and why isn't the recipient approval needed before the file exits the sender's device? I use tags, but I'm the owner not the tag.

They may not recommend disabling Tailscale SSH but I do. It interferes with sshd features and adds to your attack surface. Distribute your SSH keys the old-fashioned way and disable Tailscale SSH.

I like Tailascale as a product but I decided to move my homelab to plain WireGuard.

I wasn't using any of the additional features, I can get away with exposing a port on my router and I am changing devices rarely.

News like this make me happy I removed a lot of complexity and attack surface

I've already installed WireGuard, ZeroTier, and OpenVPN. What's the difference between Tailscale and these other tools?

Everyone is twitchy over security right now, but at first glance this seems not that bad. If the attacker has to be manually added to your tailnet that makes this not very exploitable. You should be more worried about all the iot slop on your local network.

Good idea to set up automatic updates for the tailscale client though.

I self-host a tailnet with Headscale and could not be happier: https://headscale.net/stable/

I wouldn't be too surprised if tailscale has become a critical vector of the internet like cloudflare over the years as most ai companies seem to use it

  > Most of the Tailscale SSH issues we've identified concern privilege escalation. In some circumstances, someone already authorized to connect over Tailscale SSH may be able to perform actions beyond the permissions of their configured local user, including potentially gaining elevated privileges.

"Most"? "In some circumstances"? Makes me think that they could also be investigating a full on unauthorized connection issue, or am I reading too much into it?

Recently NetBird also had a huge privesc through their SSH component too... I'm using both at $DAYJOB and my personal infra, damn you guys ought to be more careful with such a sensible and important component...

vaguely related - I want to make it easy for the llms to deploy and manage derp,tailgate etc with the hard requirement that you can continue to use the tailscale clients (very thankful to tailscale for making this so easy!):

https://tailgate.latchlabs.dev

Not a tailscale user so I am a bit lost here: where does SSH fit into a Wireguard based VPN service?

I have tried to like tailscale ssh, but having used tailscale for many many years. I always just disable it and use normal opensshd.

With the success of Tailscale I would like to be sure that their repositories and scenarios are continuously reviewed. I understand that there is always a next hop in cybersecurity though.

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I'll point out that Tailscale has been repeatedly praised here as a replacement "because SSH was too old" by "security professionals". Those very same security professional happen to be the exact same closing their eyes when there's the state doing wrongdoings.

My question to those who kept praising Tailscale and making fun of good old plain SSH: how do you like your state backdoor --excuse me, I mean bug-- in Tailscale now?

I think it's so invasive that they ship this per default. But thats the business model i guess.