BUG?: Assigning a Perl script as user shell + sending commands on ssh connect

[Brandon Simmons]

On 7/26/07, Darren Tucker <dtucker at zip.com.au> wrote:
> On Thu, Jul 26, 2007 at 06:30:03PM -0400, Brandon Simmons wrote:
> > Hi,
> > This is sort of a strange issue. But I am experimenting with ways to
> > have a user log in and be presented with a perl script to interact
> > with. When I do either or both of the following:
> >
> >      1) set the user's shell to /usr/bin/myperlscript
> >
> >      2) specify ForceCommand /usr/bin/myperlscript, applied to my user
> >
> > ...I get strange behavior when a command is appended to the client
> > connect command in this way:
> >
> >      ssh -l user 192.168.1.2 ls /etc
> >
> > The output from the perl script is not printed immediately but waits
> > for a carriage return from the user before it is printed to the
> > screen> Here is an example using a test perl script:
> [...]
> > You can see that what I type is taken as <STDIN> by the script, so I
> > guess the output is stuck in a buffer somewhere. not sure if this is a
> > bug in OpenSSH or a perl oddity. Or maybe I really shouldn't be
> > setting my user's shell to be a script.
>
> Try setting stdin/out to unbuffered in your perl script:
>
>         select STDERR; $| = 1;
>         select STDOUT; $| = 1;
>
> --
> Darren Tucker (dtucker at zip.com.au)
> GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4  37C9 C982 80C7 8FF4 FA69
>     Good judgement comes with experience. Unfortunately, the experience
> usually comes from bad judgement.
>

Thanks, that did it. While we're on the subject, is what I'm doing
with setting a user's shell to a perl script a kosher thing to do. Are
there any security problems that you know of? I've been trying to
break it, but haven't been able to at this point.

thanks