News for hackers. Stuff that matters.

A comment on Making an SSH client the hard way.

Re:Making an SSH client the hard way by gunapologist99 on Thursday October 27, 2022 @06:55PM (#33365122)
This significantly increases the threat model for your remote servers to include all sorts of remote attacks through the web, including:

  * garden-variety web attacks (i.e., XSS, CRSF, etc)

  * attacks that might become viable against the browser (for example, Mobile Safari has a history of vulnerabilities)

  * various attacks against the backend web server (API attacks)

  * attacks against the WASM layer

  * CDN injections

  * Tailscale's backend (various types of injections, timing attacks, or deeper attacks on Tailscale's infrastructure like the nightmares of HeartBleed, Shellshock, Meltdown, etc)
That's probably a very incomplete list.

Realistically, this essentially (actually, literally) opens a remote root shell into your entire infrastructure through a web page, with apparently nothing more than matching an IP address pair (https://news.ycombinator.com/item?id=33361837) to authenticate.

What could go wrong?

[ Parent | on HN ]
Re:Making an SSH client the hard way by sedatk on Thursday October 27, 2022 @07:15PM (#33365316)
That's unnecessary sensationalism. Most of those vectors are behind an SSO login and are not exposed to Internet at all (from the article: "your browser becomes a Tailscale client, and joins your tailnet in the same way as any other device that you run Tailscale on").

Or, did you mean attacks on SSO? If that's the case, then SSH web wouldn't make any difference. Someone authenticating themselves could use regular SSH or whatever.

Similarly, Tailscale backend is already subject to the vectors you mentioned (API, side-channel attacks). This feature doesn't add any new attack vectors.

Again, attacks on browser means end of game already. Someone can use that vector to access to your local network in other ways. They don't need Tailscale's SSH web client for that.

[ Parent | on HN ]
Re:Making an SSH client the hard way by gunapologist99 on Thursday October 27, 2022 @08:14PM (#33365847)
> Again, attacks on browser means end of game already.

A bad Chrome extension does not allow the bad guys to open a terminal on my machine, load my ssh keys, launch an authenticated SSH connection, and launch an authenticated SSH connection into an enumerated list of remote servers.

[ Parent | on HN ]
Re:Making an SSH client the hard way by sedatk on Thursday October 27, 2022 @09:06PM (#33366233)
A malicious browser extension can access your email, SSO prompts, password manager, etc, and therefore gain access to your Tailscale network anyway. SSH web doesn't add a new threat vector here. It's already game over.
[ Parent | on HN ]
Re:Making an SSH client the hard way by ipaddr on Thursday October 27, 2022 @09:18PM (#33366317)
A browser extension cannot access your email or password manager. But it can use this new security hole created by tailscale.
[ Parent | on HN ]
Re:Making an SSH client the hard way by yjftsjthsd-h on Thursday October 27, 2022 @09:39PM (#33366475)
If the extension in question has the read/modify all websites permission, why would it not be able to access your email or password manager?
[ Parent | on HN ]
Re:Making an SSH client the hard way by r2_pilot on Thursday October 27, 2022 @09:59PM (#33366630)
Who's using extensions in a work context anyway? I only use an ad-blocker because it's safer from a malware perspective.
[ Parent | on HN ]
Re:Making an SSH client the hard way by throwawaaarrgh on Friday October 28, 2022 @12:51AM (#33367801)
> Who's using extensions in a work context anyway?

literally everyone?

[ Parent | on HN ]
Re:Making an SSH client the hard way by francislavoie on Friday October 28, 2022 @03:17AM (#33368550)
React Developer Tools, for example.
[ Parent | on HN ]
Re:Making an SSH client the hard way by r2_pilot on Friday October 28, 2022 @06:37AM (#33369707)
Ah, thanks. I'm more on sysadmin side for my day job, and didn't even know about this. I'll have to keep it in mind as I've been dabbling with learning a modern web framework and React was a candidate.
[ Parent | on HN ]
Re:Making an SSH client the hard way by KAMSPioneer on Friday October 28, 2022 @04:51AM (#33369126)
Not OP, but...my email and password managers are not websites. I have a local app that does email, I have a local app that does password management. So the extension could certainly access passwords I put into my browser, but I don't see a vector to the "keys to the kingdom" so to speak.
[ Parent | on HN ]
Re:Making an SSH client the hard way by sedatk on Friday October 28, 2022 @12:31PM (#33373686)
The most popular password managers (1Password, Bitwarden, Lastpass) have a web UI.
[ Parent | on HN ]
Re:Making an SSH client the hard way by KAMSPioneer on Friday October 28, 2022 @02:37PM (#33375537)
Sure, and I use Bitwarden. I just don't use the web UI, specifically to avoid issues like malicious extensions, Firefox exploits, etc.

I'm aware that web-based email and credential managers exist, but GP asked "...why would it not be able to access your email or password manager?" I answered that, with my app choice, I don't see how they could.

[ Parent | on HN ]
Re:Making an SSH client the hard way by ignoramous on Thursday October 27, 2022 @07:58PM (#33365701)
Well, this exists: https://engineering.fb.com/2022/03/10/security/code-verify/
[ Parent | on HN ]
Re:Making an SSH client the hard way by dgentry on Thursday October 27, 2022 @08:12PM (#33365837)
(Tailscale employee)

It is not a web page with a shell open.

It is the Tailscale client, compiled to WASM, maintaining the keys for connections to nodes on the tailnet. Connections opened from the browser engine don't get the ability to reach the tailnet.

[ Parent | on HN ]
Re:Making an SSH client the hard way by otterley on Thursday October 27, 2022 @11:43PM (#33367391)
Given the apparent (yet possibly unfounded) concern, it might be useful to discuss this issue in the blog post. Would you consider updating it?
[ Parent | on HN ]
Re:Making an SSH client the hard way by mynameisvlad on Friday October 28, 2022 @12:02AM (#33367546)
Doesn't the post say exactly what the parent comment did? It explains the process that they came up with the WASM Tailscale, and how it authorizes and works. If anything, the parent comment just paraphrased the article.
[ Parent | on HN ]
Re:Making an SSH client the hard way by elcomet on Friday October 28, 2022 @04:16AM (#33368901)
It doesn't paragraph, this is the important sentence

> Connections opened from the browser engine don't get the ability to reach the tailnet.

That was not really explained in the article. Maybe it's obvious to some people, but I'm sure it's not for many.

[ Parent | on HN ]
Re:Making an SSH client the hard way by _hyn3 on Thursday October 27, 2022 @11:45PM (#33367408)
This seems to really expand the scope of how keys are handled and authorized. It at least appears to be optional, however.

Or just use userify's public key distribution model (then you can stick with a simple and proven design that just automates the standard SSH design that's been around for decades)

Or just do it the old way, by hand: drop your teams' public keys on groups of remote servers, setup their sudo access, and you're done.

Or just use Ansible or Chef or Terraform, or any of those other server orchestration tools, too (just without the permission layer/bulk remote session kills/user deletes of Userify).

of course, if you really need an ssh terminal in a browser, then you have to go with one of these sorts of crazy things, and at least it's not using passwords!

[ Parent | on HN ]