[BSD6] SSH Restriction

karim.bourenane at orange-ftgroup.com karim.bourenane at orange-ftgroup.com
Fri Aug 1 12:36:15 UTC 2008

For exactly description. 

We have one user (robot) connect on server with ssh command and telnet argment to access on some router.
The connection is not closed and cleaned properly. Also the CPU increases dangerously.


     Karim Bourenane
112 Av. Charles de Gaules
92520 Neuilly S/Seine
Phone:	+33156 76 35 52
Fax:	+33156 76 35 04

-----Original Message-----
From: Kostik Belousov [mailto:kostikbel at gmail.com] 
Sent: vendredi 1 août 2008 14:27
To: Ed Schouten
Subject: Re: [BSD6] SSH Restriction

On Fri, Aug 01, 2008 at 02:10:04PM +0200, Ed Schouten wrote:
> Hello Karim,
> * karim.bourenane at orange-ftgroup.com <karim.bourenane at orange-ftgroup.com> wrote:
> > I have one question. How i can restrict ( limit ) 1 user to have for 
> > exemple 5 ssh connection in simutanous time, no more ?
> It's quite funny you ask this question, because I've been working on 
> this last week.
> The new TTY code, which I'll commit next week, adds a new rlimit to 
> the kernel called RLIMIT_NPTS. This rlimit allows you to limit the 
> number of pseudo-terminals allocated by a single user. This means you 
> can limit the number of login sessions by tuning the "pseudoterminals" 
> field in /etc/login.conf.
> This seems to work with tools like screen(1), xterm(1), etc.
> Unfortunately I didn't get it working with OpenSSH, because OpenSSH 
> allocates terminals while been root. I've already contacted the 
> OpenSSH folks about this, but I haven't got any response (yet).

Limit on the allocation of the ptys is useful. Trying to use it to top the number of the "sessions" may be not.  There is a -T option for the ssh(1).

Without clear description of why the restriction is imposed, the question probably cannot be answered.

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