openssh bugs - Feb 2005 - [Bug 984] Hangup to script while forced command ...

http://bugzilla.mindrot.org/show_bug.cgi?id=984

           Summary: Hangup to script while forced command ...
           Product: Portable OpenSSH
           Version: 3.9p1
          Platform: All
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: sshd
        AssignedTo: openssh-bugs at mindrot.org
        ReportedBy: webmyster at addoc.u-psud.fr


I have an account named demo. In its $(HOME)/.ssh/authorized_keys, I entered my
public key with a forced command that is a script. This script allows the user
to make a choice to launch a nohup backgrounded X-window (forked, without hang
up signal and without standard I/O). Then, the script leaves, that close the ssh
connection.
If I connect through ssh to this account without any command (ie : "ssh
user at computer"), xinit receives a hangup signal, causing X-window to
shut down.
However, if i connect to this account with whatever string as command (ie :
"ssh
user at computer foo"), my script is executed as expected : xinit don't
receive any
hangup and X-window don't shutdown unless I do it explicitely.



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------- Additional Comments From djm at mindrot.org  2005-02-17 23:18 -------
Try setting setting no-pty on the key too. E.g.

no-pty,command="xscript" ssh-rsa ....

Does that help? HUP is only sent to shells with a controlling terminal



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------- Additional Comments From webmyster at addoc.u-psud.fr  2005-02-18 19:26
-------
(In reply to comment #1)
> Try setting setting no-pty on the key too. E.g.
> 
> no-pty,command="xscript" ssh-rsa ....
> 
> Does that help? HUP is only sent to shells with a controlling terminal
Actually no, because this script is asking the user through the read bash
command inside the script.
The most important problem, I think, is the strange behaviour that whenever I
specify one command (whatever command), it don't hang up my xinit. However,
when
I don't give any command, a hangup is send to the xinit causing X-window to
shutdown.



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------- Additional Comments From dtucker at zip.com.au  2005-02-18 19:44 -------
(In reply to comment #2)
> > no-pty,command="xscript" ssh-rsa ....
> 
> Actually no, because this script is asking the user through the read bash
> command inside the script.
Did you try it?  "read" just reads from stdin and doesn't need a
controlling
terminal.
> The most important problem, I think, is the strange behaviour that whenever
I
> specify one command (whatever command), it don't hang up my xinit.
However,
> when I don't give any command, a hangup is send
By default, when you "ssh yourserver" you get a pty and when you
"ssh yourserver
somecommand" you don't.  Try "ssh -T yourserver" to prevent
allocation of a pty.

You could also launch the command in your script with nohup.



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------- Additional Comments From webmyster at addoc.u-psud.fr  2005-02-18 20:10
-------
Created an attachment (id=829)
 --> (http://bugzilla.mindrot.org/attachment.cgi?id=829&action=view)
script running as forced-command

Here is the script I am running as forced-command. As you can see, there is
already nohup to launch commands.
The problem when I set no-pty in the authorized-files, is that the display
seems strange (loosing the width of the term). But the most important problem
is the fact that I can't type anything. I must kill this script from another
console.

However, the command "ssh -t user at computer" works fine !



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