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?
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.
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 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 had no idea about that, thank you!
I'd recommend using https://github.com/gliderlabs/ssh instead, no chance of some shell escape that way.
I use a fork of that!
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 :)
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!
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
lol
you can configure sshd to run any random executable when a user connects
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.
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.
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! :)
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!
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
why is this downvoted?
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.
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:
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.
odd dns reasons
I would love to hear more about this
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?
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.
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/
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!
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.
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...
There was a beginner friendly machine to hack on HackTheBox where you had to hack a Devzat instance
a devzat regular made that!
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 :)
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 appear to have crashed the server with "tic 999", sorry guys!
that wasn't it but yeah lol
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.
Chatting via SSH has given me a lot of insights. Thank you.
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
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)
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
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?
This is great, now we just need a way to host it on our mobile phones.
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
yup, not an extensive list, but further demonstrative:
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
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...
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.
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.
whoa
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
https://news.ycombinator.com/item?id=41002245
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
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