SSHD creates defunct process

[Darren Tucker]

Peter Stuge wrote:
> On Wed, May 11, 2005 at 12:17:34AM +0530, Chidanand Gangur wrote:
>>When started with strace SSHD waits in select loop.
> 
> Ok, so you're on Linux.
> Try strace -fF sshd -D

Be aware that strace on Linux will change some of the behaviour of the 
parent/child relationships, so while it may help it's not an ideal 
diagnostic.

[and from the original posting]
 >> PAM [dlerror: /lib/security/$ISA/pam_deny.so: cannot open shared
 >>object file: No such file or directory]

It looks like you are missing the pam_deny.so file, or the path is wrong 
in /etc/pam.d/system-auth.

>>I have placed various log messages in sshd source code .what  I can
>>see  is after calling do_pam_converse  function from do_pam_account
>>function sshd does nothing. that is creates zombie.
> 
> Hm, I'm not too familiar with the workings of the PAM but perhaps the
> trace output could help nail the problem down.

There's a bug in some versions of LinuxPAM that prevents an app from 
changing of the conversation function.  It's possible that PAM is 
calling the wrong conversation function:
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=126985

I wrote a tool for figuring out what PAM is doing underneath the covers, 
based in part on sshd's PAM interface code.

It's available here:
http://www.zip.com.au/~dtucker/patches/pam-test-harness.c

The documentation, such as it is, is here:
http://www.zip.com.au/~dtucker/patches/#pamtest

-- 
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.