go.crypto/ssh server

[Vasiliy Tolstov]

Hi All. if i want to use go.crypto/ssh for writing small ssh server,
and provide interactive terminal for end user (user used openssh
client). What i need to do?
I can run commands from users by exec.Command and get ourput. But for
interactive commands i need to pty.
how can i create pty and use it in golang ssh server?
Thanks!

--
Vasiliy Tolstov,
e-mail: v.to...@selfip.ru
jabber: va...@selfip.ru

[agl]

On Monday, December 2, 2013 2:57:23 AM UTC-5, Vasiliy Tolstov wrote:

Hi All. if i want to use go.crypto/ssh for writing small ssh server,
and provide interactive terminal for end user (user used openssh
client). What i need to do?
I can run commands from users by exec.Command and get ourput. But for
interactive commands i need to pty.
how can i create pty and use it in golang ssh server?
Thanks!

See http://godoc.org/code.google.com/p/go.crypto/ssh#example-Listen

(Although note that the ssh/ package is likely to have major work done in the Go 1.3 timespan.) 

Cheers

AGL 

[Vasiliy Tolstov]

2013/12/2 agl <a...@golang.org>:

> See http://godoc.org/code.google.com/p/go.crypto/ssh#example-Listen
>
> (Although note that the ssh/ package is likely to have major work done in
> the Go 1.3 timespan.)
>
>
> Cheers

Thanks. Exammple listen very good. But then i try to exec mc i can't
move keys up/down. I think that because readline usage in example...
But i may miss somethink more...

[chend...@gmail.com]

hello, 

  I'm writting small ssh server use pty, but I can not work out.

  So you can mail your ssh server code to me?

  Best Wish. Thank you very much

  by the way,  http://godoc.org/code.google.com/p/go.crypto/ssh#example-Listen can not open

在 2013年12月2日星期一UTC+8下午3时57分23秒，Vasiliy Tolstov写道：

[jpil...@gmail.com]

+1

I think I've nearly got it, see the following gist: https://gist.github.com/jpillora/b480fde82bff51a06238

Though I'm getting "PTY allocation request failed on channel 0" when I connect to it

Any tips?

[Dave Cheney]

Hmm, can you look at the log from the server's end ? It should be /var/log/secure or /var/log/auth.log from memory of the common places that distros set their syslog to.

[Jaime Pillora]

Hi Dave, currently testing on Ubuntu 14.04.1 LTS (GNU/Linux 3.13.0-39-generic x86_64) – log/secure doesn’t exist and log/auth.log only contains contains the system sshd logs. I thought a crypto/ssh server was a complete implementation or does it depend on the system sshd? Also I seem to be able to log in okay, though maybe the crypto/ssh/terminal package is failing to get a pty, see https://gist.github.com/jpillora/b480fde82bff51a06238#comment-1347606

[Dave Cheney]

Os, my mistake, I thoght you were using the client against sshd. I'm not sure if or where the os would log an issue if a process couldn't allocate a new tty. Ada guess, have you run out of file descriptors?

[Dave Cheney]

Ah, figured it out, the go ssh terminal doesn't support allocating a
pty (so no concept of screen size, raw vs cooked etc), by default
openssh will request a pty _unless_ you pass a command, ie

ssh someone@somewhere /bin/ls

Won't allocate a pty, you can check this by doing ssh somewhere top,
top will whinge because there isn't proper terminal control.

However, when there is no command supplies, ssh requests a shell
session, and a pty, this is what is failing. You can disable the
automatic pty setting with -T, or in .ssh/config, or a bunch of other
ways

% ssh foo@localhost -T -p 2022

foo@localhost's password:

> hello

hello

On Tue, Dec 2, 2014 at 1:48 PM, Dave Cheney <da...@cheney.net> wrote:
> Os, my mistake, I thoght you were using the client against sshd. I'm not sure if or where the os would log an issue if a process couldn't allocate a new tty. Ada guess, have you run out of file descriptors?
>

> --
> You received this message because you are subscribed to a topic in the Google Groups "golang-nuts" group.
> To unsubscribe from this topic, visit https://groups.google.com/d/topic/golang-nuts/rIWZIjsXoqg/unsubscribe.
> To unsubscribe from this group and all its topics, send an email to golang-nuts...@googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.

[Rob Pike]

Wait, teletypes are finally gone so we need pseudo teletypes?

-rob

You received this message because you are subscribed to the Google Groups "golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts...@googlegroups.com.

[Dave Cheney]

Gotta virtualize everything rob, this is the future.

[Jaime Pillora]

Sorry, I’ve been just replying to Dave – for completeness:

$ sysctl fs.file-nr

fs.file-nr = 768 0 400048

Do you get the same result when you run https://gist.githubusercontent.com/jpillora/b480fde82bff51a06238/raw/8cf42960783ccaef3d00da9af7a9452767c3fec4/sshd.go ?

[Dave reports that ssh/terminal doesn’t support allocating ptys]

ah I see, so it’s not supported, I’ll try mixing in https://github.com/kr/pty and report back - thanks dave

On Tue, Dec 2, 2014 at 1:48 PM, Dave Cheney <da...@cheney.net> wrote:

Os, my mistake, I thoght you were using the client against sshd. I'm not sure if or where the os would log an issue if a process couldn't allocate a new tty. Ada guess, have you run out of file descriptors?

[Rob Pike]

If we're typing on teletypes, pseudo or otherwise, it may be the future but we are living in the past.

OK, I'll stop now. I started complaining about this long ago and nobody cared then, either.

-rob

[jpil...@gmail.com]

Thanks Dave, all working now https://gist.github.com/jpillora/b480fde82bff51a06238 (with window resizes too! give 'top' a try)

[Dave Cheney]

Awesome work.

I had a look at ssh/terminal to see if it should really be doing the
pty handling, but my impression is that facility is beyond the remit
of the terminal package.

With that said, this is the sort of knowledge that should be shared.
How much would I have to twist your arm to blog about this ? If you
don't have a convenient spot to blog this can I gratuitously plug the
Go Advent series we're running over at blog.gopheracademy.com ?

Cheers

Dave

[Jaime Pillora]

I don’t have a blog myself, though I’d be happy to write up a few paragraphs on gopheracademy. Send through an email with the details and I’ll get on it.

[Nick Craig-Wood]

On 02/12/14 09:08, jpil...@gmail.com wrote:
> https://gist.github.com/jpillora/b480fde82bff51a06238 (with window
> resizes too! give 'top' a try)

Very nice!

It seems to be leaving behind zombies. ps axf looked like this after 3
logins and exits

6772 pts/73 Sl+ 0:00 | | \_ ./go-sshd-example
6786 ? Zs 0:00 | | \_ [bash] <defunct>
6806 ? Zs 0:00 | | \_ [bash] <defunct>
6817 ? Zs 0:00 | | \_ [bash] <defunct>

--
Nick Craig-Wood <ni...@craig-wood.com> -- http://www.craig-wood.com/nick

[Gyu-Ho Lee]

Thanks! This happens to be the one that I need right now.

[jpil...@gmail.com]

> You need to call Wait() to reap the zombies.

Thanks Nick, Wait() did the trick – updated the gist