openssh unix dev - May 2002 - [Bug 223] ProxyCommand commands don't exit

http://bugzilla.mindrot.org/show_bug.cgi?id=223

dtucker at zip.com.au changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         OS/Version|FreeBSD                     |All
           Platform|ix86                        |All
            Version|3.0.1p1                     |-current



------- Additional Comments From dtucker at zip.com.au  2002-05-23 16:27 -------
Also observed on Solaris 7 & 8 with OpenSSH 3.2.2p1. You end up with an
orphaned
sh -c:
$ ps -eaf | grep nc
root 219 218 0 16:18:27 pts/4  0:01 ssh relayhost nc 10.3.1.1 22
root 218   1 0 16:18:27 pts/4  0:00 /bin/sh -c  ssh relayhost nc 10.3.1.1 22



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------- Additional Comments From dtucker at zip.com.au  2002-05-23 20:02 -------
Created an attachment (id=103)
Kill ProxyCommand child process




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------- Additional Comments From dtucker at zip.com.au  2002-05-23 20:05 -------
I had a poke around and came up with the attached patch to send a SIGTERM to the
ProxyCommand child when ssh exits. I also added an explicit exec to the shell 
command passed to sh -c, which prevents the shell hanging around on Solaris. 
This problem doesn't seem to exist on Linux but I think the exec is safe for
any
platform.

The remaining problem is that the child process can send an error message to 
stderr after the SIGTERM. I'm not sure what (if anything) can be done about 
that:

$ ./ssh -o 'ProxyCommand nc localhost 22' localhost echo
 punt!

Feedback welcome but since this is my first attempt to actually modify openssh 
please be nice :-).



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------- Additional Comments From markus at openbsd.org  2002-05-25 17:49 -------
so 'ProxyCommand exec nc localhost 22' works
without any patches?



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------- Additional Comments From dtucker at zip.com.au  2002-05-25 18:39 -------
It works but still leaves an orphaned nc (on Solaris anyway):

$ ssh -o 'ProxyCommand exec nc localhost 22' localhost echo

$ ps -eaf | grep nc
dtucker  9919  9049  0 18:23:45 pts/2    0:00 grep nc
dtucker  9912     1  1 18:23:40 pts/2    0:00 nc localhost 22

After some more investigation I think there's 2 issues:
1) On all platforms, the child process isn't signalled when ssh exits,
leaving
them orphaned.
2) On Solaris (and possibly other platforms), running the ProxyCommand without
"exec" also leaves an extra "sh -c". Additionally, the
"sh -c" ignores SIGHUP
and doesn't propogate SIGTERM, so even if ssh kills its child you're
still left
with 1 orphan rather than 2.

FWIW, I've been working on a better patch that fixes 1 by always using exec
and
fixes 2 by sending SIGHUP (then SIGTERM then SIGKILL) to the child. This seems
to be a clean solution.

I'm cleaning the patch up for posting now.



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------- Additional Comments From dtucker at zip.com.au  2002-05-25 19:33 -------
Created an attachment (id=104)
Updated patch to kill proxycommand child process




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------- Additional Comments From dtucker at zip.com.au  2002-05-25 19:41 -------
OK the new patch seems to work (on Solaris anyway) even in the pathological
case. (nc-nosig is netcat modified to ignore all signals).

$ ./ssh -v -o 'ProxyCommand ./nc-nosig localhost 22' localhost echo
[snip]
debug1: Exit status 0
debug1: Terminating ProxyCommand child process pid:10203
debug1: ProxyCommand terminated with signal 9

Neither nc-nosig or the normal netcat leave orphaned processes.

The timeout is currently hardcoded at 2 seconds per signal. Is this enough?




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