[Pkg-ltsp-devel] Bug#490897: tcsh logins

[Daniel Nilsson]

On Sat, Aug 16, 2008 at 07:59:20PM -0700, Vagrant Cascadian wrote:
> >      cmd[i++] = ";";
> > +    cmd[i++] = "exec";
> > +    cmd[i++] = "sh";
> >      cmd[i++] = "kill";
> >      cmd[i++] = "-1";
> >      cmd[i++] = "$PPID";
> 
> no probably about it, in my tests, it definitely solved the issue.
> 
> because it uses exec, it gets the proper value for $PPID, which should
> be the sshd process used to log in (yes, it's an ugly hack, but that's
> how it works for now). at least on lenny.
> 
> to reproduce: ssh to the server, with a user with the default shell of
> tcsh. run "exec /bin/sh". "echo $PPID". the $PPID is the pid of sshd.

I did more test, and this works as you said:

daniel at oden:~$ ssh -l labtcsh oden 'exec /bin/sh'
Password:
echo $PPID
9741

However, I've tried various forms of this and I can't get to work:

daniel at oden:~$ ssh -l labtcsh oden 'exec /bin/sh -c echo \$PPID'
Password:

daniel at oden:~$ ssh -l labtcsh oden 'exec /bin/sh -c echo $PPID'
Password:
PPID: Undefined variable.

I also tried your complete dpatch as is and it does not solve the
problem in my test setup, logouts fails and I need to kill the sshd
process on the server in order for logout to complete. My only guess
is that it has something to do with the above shell escaping issues.

I have attached a dpatch formatted version of the method I used where
PPID is retrieved using ps. So far this is the only method I've found
that solves the problem together with an etch based server. Are you
testing against a lenny server?

> there's definitely resistance to applying any of these patches upstream:
> 
>   http://sourceforge.net/mailarchive/forum.php?thread_name=20080815201358.GF12833%40ryukin.fglan&forum_name=ltsp-developer

Sure, I can understand this. This tends to become a hot topic due to
matter of preferences. I ended up a tcsh user since that was the
standard at the university back in the SunOS 4 days. There are
probably many advantages using bash over tcsh, but that is a different
topic. Since users are able to switch the shell to their preference,
and tcsh is still widely used, I think this bug needs to be handled
somehow since the result for a tcsh user is just a failed login with
no error messages. This will burden the sysadmins a lot trying to
figure out why a particular user can't log in when other can.

> one idea is to actually log in using /bin/sh, so that we can have a
> known login shell, as supporting multiple incompatible shell syntaxes is
> a rather difficult task...

Sounds like a better approach, agreed.

Regards
-- 
Daniel Nilsson
-------------- next part --------------
#! /bin/sh /usr/share/dpatch/dpatch-run
## fix_tcsh_logins_daniel.dpatch by  <daniel at oden.home.dnil.se>
##
## All lines beginning with `## DP:' are a description of the patch.
## DP: No description.

@DPATCH@
diff -urNad ldm-2.0.6~/src/ldm.c ldm-2.0.6/src/ldm.c
--- ldm-2.0.6~/src/ldm.c	2008-05-31 00:41:45.000000000 +0200
+++ ldm-2.0.6/src/ldm.c	2008-08-17 11:31:38.000000000 +0200
@@ -258,6 +258,7 @@
     cmd[i++] = "-l";
     cmd[i++] = ldminfo.username;
     cmd[i++] = ldminfo.server;
+    cmd[i++] = "env";
     cmd[i++] = ltspclienv;
 
     /*
@@ -315,7 +316,7 @@
     cmd[i++] = ";";
     cmd[i++] = "kill";
     cmd[i++] = "-1";
-    cmd[i++] = "$PPID";
+    cmd[i++] = "`ps -o ppid -p $$ | tail -1`";
     cmd[i++] = NULL;
 
     xsessionpid = ldm_spawn(cmd);
diff -urNad ldm-2.0.6~/src/sshutils.c ldm-2.0.6/src/sshutils.c
--- ldm-2.0.6~/src/sshutils.c	2008-05-31 00:41:45.000000000 +0200
+++ ldm-2.0.6/src/sshutils.c	2008-08-17 11:30:50.000000000 +0200
@@ -68,6 +68,7 @@
     sshcmd[i++] = "echo";
     sshcmd[i++] = SENTINEL;
     sshcmd[i++] = ";";
+    sshcmd[i++] = "env";
     sshcmd[i++] = "LANG=C";
     sshcmd[i++] = "/bin/sh";
     sshcmd[i++] = "-";