Devzat – Chat over SSH, with some nice quality-of-life features | Hacker News Reader

Devzat – Chat over SSH, with some nice quality-of-life features

github.com

435 pointshumanperhaps105 comments

I have a Raspberry Pi running a read-only server where some friends and I have a "poor man's IRC" chat, in that we all log in from Termux and post messages to one another using `wall`. It's absolutely ridiculous and I love it.

It's one of those things that if you need to ask why, you'll never understand :-)

Yea, came here to say, what about wall! :)

Install `finger` and you've practically got a social media platform.

I’m trying to google finger and all I get is fingerprint software

https://en.wikipedia.org/wiki/Finger_(protocol)

An old, old Internet protocol that was used to get information on a user, and could be used by users to post updates from their .plan files. Essentially plaintext social media for people with Internet connections in the 80s and (early-ish) 90s.

I had that "oh crap, I'm old" moment when my initial reaction was "what? You've never heard of finger?!" and then I remembered I last used it in the late 90s.

I'm glad your reaction was to assist the young folks. :)

Famous for enabling one of the very early Internet Worms.

https://en.m.wikipedia.org/wiki/Morris_worm

Reimplementing it (well, the CLI program, `finger`) also happens to be the final exercise of Haskell Programming from First Principles, after 1200 pages of glorious buildup from the lambda calculus forward, in case that sells anyone on trying it ;)

.plan was the original status update.

Indeed, I wish there was something like it today with a modern design. Like a DHT with your public key fingerprint as a lookup. Anyone who 'follows' your .plan also hosts it as a torrent. You 'approve' followers by signing your .plan file with their pubkey, or for a fully public .plan, just sign with your private. Blah blah blah decentralized cypherpunk social media utopia.

That's basically what ssb or dat are

Thank you! I hadn't heard of either of these.

Oh man, I've been working on this stuff for years. End users just don't care. Devs just reinvent the wheel in dumbass languages. The tech for this stuff has existed for 15 years, there's nothing to invent. It's ready now.

https://github.com/anacrolix/btlink https://github.com/anacrolix/dht

Thanks, I'll check these out. I have some hope that something like this could take off because of the popularity of Mastodon. I think the problem is that there has to be a major impetus for lots of people to switch, and it has to be completely brain dead stupid simple to set up, and to have it work fairly transparently so they don't feel like they're doing something completely new and different. Unfortunately decentralized services tend to add overhead, and user's expectations have been primed with centralized tech. We might see people care about stuff like this if we get more online censorship with government taking a closer look at tech lately.

I wonder if you could do something similar with an ssh account which is hard-wired to run 'ytalk' (https://en.wikipedia.org/wiki/Talk_(software)).

Probably. See my comment (and example repo) elsewhere about running any old binary when someone connects.

Or you can just run IRC client on start. Just trap SIGINT and SIGTSTP, run simple or modified client that cannot do exec or escape to shell and you are done :)

Spoiler: set the user’s shell to any old binary, like a chat app.

Or in the authorized_keys file, prepend the public key with a specified command. This is then the only command that the user can execute when logging in with that particular key. To wit:

  command="/usr/bin/foo" ssh-ed25519 AAAA....

i had no idea about that, thank you!

I suppose this will also lock the user out of sftp and scp? Because otherwise they might be able to edit the authorized_keys file and run any command.

"I suppose this will also lock the user out of sftp and scp?"

No it wont! The specified command might provide sftp, scp, telnet or stream a film.

I stream a film at funky.nondeterministic.computer on port 22

hah

made me laugh

I'd recommend using https://github.com/gliderlabs/ssh instead, no chance of some shell escape that way.

I use a fork of that!

Pretty neat! We implemented something similar with an IRC chat app (senpai) in our SSH app (pico.sh). After the user creates an account, it lets users connect to our public IRC bouncer with a single command (`ssh pico.sh -t chat`).

ref: https://pico.sh/irc

See also: ssh-chat by shazow from ~10 years ago written in Go

  ssh chat.shazow.net

The most amazing part is perhaps the fact that this one is still around, 10 years later! Try it yourself and you’ll see :)

Discussion at the time:

https://news.ycombinator.com/item?id=8743374

Source code in GitHub repo here:

https://github.com/shazow/ssh-chat

ssh-chat sort of inspired devzat. here's the story: I used to live in dubai at the time and for some odd dns reasons I could never actually join ssh-chat, but it acted as proof that ssh chats are possible, and so I decided to make my own version of it. then I moved to the us and was actually able to use both ssh-chat and devzat.

That’s so cool and nice :D

Any idea what we could do to allow all of the people still in Dubai to join chats over ssh too?

> odd dns reasons

I would love to hear more about this

I'd be curious whether there's any security concerns on this one. Could an attacker craft a message that gets access to execute commands into a client terminal?

Yeah, though SSH is already very mature at processing text, so it's a surprisingly good fit for a chat. I would also remember that any machine you SSH from is going to give the server some metadata like IP address, public keys (which aren't useful as creds but can be for tracking). Really fun little project though

SSH might be, but maybe not your terminal. Which the very least can possibly trick you using escape codes. Also, unless my memory fails me 'cat'ing an untrusted file isn't recommended for security reasons.

Additionally you should disable SSH forwarding. Relevant thread from the startup selling coffee over SSH: https://news.ycombinator.com/item?id=40227624

This is not sshd, this is a golang binary that uses the stdlib ssh lib. You would have to either a) figure out how to escape out of a golang binary, or b) if the go code executes shell commands with some user provided text, trying to shell inject something in there.

Or convince the ssh daemon to pass on terminal escape codes to another user.

https://nvd.nist.gov/vuln/detail/CVE-2021-33477

whoa

yup, not an extensive list, but further demonstrative:

  - terminal emulators are not security hardened clients against malicious actors
  - ssh lacks PKI and is inconvenient so users never do prekeying in practice, so it's TOFU / zero server assertion in most practical cases (i.e. easy to mitm)
  - ssh channel features are a constant concern, for server resources and for client features like agents, agents are easy to disable
  - most ssh implementations don't scale that well, it wasn't ever really a goal to do so
  - there are few tools for auditing and monitoring, unlike the common protocols/services/clients

fun for toys, but i wouldn't put credit card details in there, unlike some streamers started doing lately.

ssh definitely supports PKI, it's just not the standard workflow for individuals

     ssh-keygen (1):  

     ssh-keygen supports signing of keys to produce certificates that may be used for user or host authentication.
     Certificates consist of a public key, some identity information, zero or more principal (user or host) names and
     a set of options that are signed by a Certification Authority (CA) key.  Clients or servers may then trust only
     the CA key and verify its signature on a certificate rather than trusting many user/host keys.  Note that
     OpenSSH certificates are a different, and much simpler, format to the X.509 certificates used in ssl(8)

I'm not talking about supporting public key cryptography, I'm talking about having a specific and usable deployment of a PKI. The closest thing SSH has is SSHFP, which depends on DNSSEC, which is according to many opinions, DOA.

TIL about PKIX-SSH, OpenSSH + X.509.

https://gitlab.com/secsh/pkixssh

http://tech.ciges.net/blog/openssh-with-x509-certificates-ho...

Right now I'd stick with something like Gravitational Teleport (overkill); Warpgate may become the perfect fit for this niche soon.

https://github.com/warp-tech/warpgate

It's also worth knowing about SSH clients that can use X.509 certificate keys as normal pre-shared keys with any SSH server, like PuttyCAC and built-in for macOS High Sierra and later.

https://www.idmanagement.gov/implement/scl-ssh/

OpenBAO and Hashicorp Vault also have built-in support for SSH certs: https://openbao.org/docs/secrets/ssh/signed-ssh-certificates...

PKI, with I in bold quotation marks.

While it supports serial numbers, expiration dates and key revocation lists, it does not allow certificate chaining. That means whoever signs keys for end users has implicit access to the master key.

I'm also interested. Setting up a passwordless SSH account for some public service sounds like a good way to give your machine away to North Korean hackers, because you forgot to set someting in /etc/sshd to "no".

Is there a usable description somewhere on how to do this safely?

i'd be interested in seeing that. here its ok because it doesnt use sshd at all

So it's using a new stack that hasn't been vetted like OpenSSH? I'd rather use OpenSSH + LibreSSL for this application.

https://news.ycombinator.com/item?id=41002245

You may not want the chat server owner to know which public ssh key you are using for privacy reasons.

Workaround: Specify another ssh keypair

I experimented with writing a shell replacement a while back. Turns out you can just run any old program. Here’s and example “hello world” shell replacement written in Go.

https://github.com/codazoda/goshell

> Turns out you can just run any old program.

It’s amazing how simple some things are. Similarly, an HTTP server can also run any old binary in response to an incoming request. As long as it produces output that looks like an HTTP response, the client will receive that response.

good old cgi

but nginx or caddy can't run CGIs, they want scalability to the billions.

Disclaimer: I build a personal social web server https://seppo.social like that on top of shared (apache) hosting requiring no root privileges to install and run.

Or with a few lines of sh you can turn many cli tools to web services like https://qr.mro.name/

so sorry for it being down right now. hn hug of death is real

Guess it’s only useful as a toy :)

I just have a really shit server

which is great for human scale! Don't serve billions and burn the planet doing so.

Or the person never expected more than a couple of hundred concurrent users and dimensioned the container or whatever after that.

I once wrote a similar chat, but much much worse in many ways, that could easily handle thousands of concurrent users, but hosted it on a 1mbit residential line. When Slashdot hit it I stood no chance.

Didn't think about that when posting - my bad

oh nonono thanks for posting lol

Amazing project, by the way!

There was a beginner friendly machine to hack on HackTheBox where you had to hack a Devzat instance

a devzat regular made that!

Cool, the source code is amazingly readable. Also love the sense of humor :-D such as https://github.com/quackduck/devzat/blob/main/commands.go#L1...

When I read this comment, thought good readability it’s got to be Go

The readability might be nice, but the way files are structured makes no sense to me.

In PHP/Typescript there’s always a direct correspondence between imports and file locations, but Go baffles me.

why is this downvoted?

As a gentle reminder, if you are forwarding your ssh-agent by default, you should connect with:

    ssh -o 'ForwardAgent no' $host

So your secure identities are not exposed to a random ssh server ...

Forwarding your agent by default (to all hosts!) sounds like a terrible idea.

I love stuff like this. I made a widget for MacOS where you can see incoming |hi messages sent to your Urbit, as a kind of poor man's p2p chat. But I didn't add a feature to send hi messages, so you still need a CLI for that.

You can see what it looks like here: https://www.youtube.com/watch?v=_bAx4Jx39jE&t=384s

(it's the widget in the bottom right of the screen)

Related: Does anyone by chance know how to configure an "anonymous" ssh account that always runs the same program? This would be great for making text mode games available to everyone without needing to support different platforms, now that windows actually ships with ssh.

customize https://github.com/gliderlabs/ssh

I use it for funky.nondeterministic.computer

Thanks for the link! However, I will not touch the Google programming language.

your loss. fwiw, It's not run by Google any more

Still tainted :-) Everything that Google touches is tainted.

lol

you can configure sshd to run any random executable when a user connects

Wouldn't it be possible to just change the shell via 'chsh' or editing /etc/passwd to point to the text mode game for a particular user

THats the theory. However, AIUI, you need a machine that only does this single application. Because if you have a user without password, that can be an issue for many other services. SMTP for instance.

Is this working for anybody else?

I created a throwaway ed25519 key, reconfigured ssh config, and tried to connect with ‘ssh chat’

Nothing loads. ‘ssh -v chat’ isn’t helpful either. ping and nc (on both 22 and 443) show the server (or load balancer) is accessible for me.

Maybe a “hnfp DoS” (hacker news front page DoS)?

Have you tried connecting with the actual hostname directly instead of an alias?

Edit: nvm the author said it’s down

back up now!

https://man.netbsd.org/authpf.8

https://man.openbsd.org/authpf

If you want to use my server, it might be a little more powerful than the current one. I would self host but to be honest I'd prefer helping out with the main instance. In case, I am here

Looks like ascii colors aren't being filtered correctly.. which is a pretty big issue. White on white isn't very readable... :-)

this sounds like a terminal thing. what terminal are you on.

what sort of server resource usage is this like right now as you are getting a ton of traffic?

also noticed that people were able to run commands but permission denied. that kinda freaked me out. eventually somebody is going to figure out how to escape the go binary

im not worried at all :)

This is actually cool!

But unless I'm missing something, what's the difference between this and IRC?

The in-network effect.

hmm? whats that

The market force that currently propels whatsapp.

Doesn't seem to be working, the chat is frozen and I can't type anything.

Same here, seems to have crashed.

working on bringing it back, hold on

Cool. Hanging!

This is great, now we just need a way to host it on our mobile phones.

I appear to have crashed the server with "tic 999", sorry guys!

that wasn't it but yeah lol

Chatting via SSH has given me a lot of insights. Thank you.

This makes my list for top of the year, nice work.

ssh: connect to host devzat.hackclub.com port 22: Connection refused

PORT STATE SERVICE

22/tcp closed ssh

Nmap done: 1 IP address (1 host up) scanned in 1.18 seconds

----

overloaded?

Normal talk in unices system can do that.

Irc have exange data between server and minimalize data trafic.

still irc is better, but meybe in future

There was also `write` [0]. It would literally parse /etc/utmp [1] to find out which terminal the recepient user was logged on, then it would open that terminal and write(2) the message to it. Ah, wonderful user isolation.

[0] https://man.cat-v.org/unix-6th/1/write

[1] https://man.cat-v.org/unix-6th/5/utmp

I still use posix write [1] if there is an incident and i want to talk to the other admins that all try to fix sth. Quite fünf AS the younger ones are always Quote puzzled and feel caught...

[1] https://manpages.org/write

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