misc/183495: utx.active not being updated correctly
Ed Schouten
ed at 80386.nl
Wed Nov 13 21:00:02 UTC 2013
The following reply was made to PR misc/183495; it has been noted by GNATS.
From: Ed Schouten <ed at 80386.nl>
To: bug-followup at FreeBSD.org, rich at enterprisesystems.net
Cc: freebsd-hackers at freebsd.org
Subject: Re: misc/183495: utx.active not being updated correctly
Date: Wed, 13 Nov 2013 21:58:32 +0100
Hi there,
[ +freebsd-hackers, to see whether this change would go in the right direction ]
It seems that the regression described in misc/183495 is unrelated to
utmpx alone. Unlike utmp, utmpx allows multiple entries per TTY. This
causes the issue to become actually visible.
telnetd uses login(1) to provide a login prompt, interactive shell,
etc. Looking at the source code of login(1), it seems that it never
attempts to call pam_cleanup() whenever the process terminates with
SIGHUP, nor does it protect itself against SIGTERM properly. The
following patch should fix this issue partially:
http://80386.nl/pub/login-signal-fix.txt
Still, one issue that remains is that the parent process can still be
killed using SIGKILL, thereby allowing you to circumvent
pam_cleanup(). What would be the right approach to fix this? Changing
the effective UID would solve this, but I don't feel really
comfortable to modify these kind of pieces of software. It's easy to
introduce security bugs.
Thoughts?
--
Ed Schouten <ed at 80386.nl>
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