From owner-freebsd-questions  Tue Mar  2  8:26:51 1999
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Date: Tue, 02 Mar 1999 09:26:25 -0700
To: questions@freebsd.org
From: Brett Glass <brett@lariat.org>
Subject: Segfault when executing "Kerberized" su
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[Note: I first sent this question to the "security" list, but didn't
receive a copy back from the listserv. (Is something broken?) So, I'm
posting it to "questions" in the hope that I might get a quicker answer. -BG]

I recently set up FreeBSD 2.2.8-RELEASE on a new system, bringing over most
of the users from an older one that had suffered a security compromise.
After installing FreeBSD with Kerberos, I secured the system by removing
most of the daemons in inetd, adding S/key, adding TCP wrappers, and
installing sshd for remote logins. I then added a random password
generation script, merged in entries from the old system's password and
group files, and nuked the users' old passwords so they'd have to be
reassigned by the sysadmin via the random password generator. I used a Perl
script to read the password file and create fresh home directories for all
of the users I'd just  merged in (that is, whose home directories didn't
exist yet).

After doing this, I logged off to go to lunch. When I logged back on and
attempted to su to root, I discovered that su was taking a long time to run
and then aborting with a segfault! Experimentation showed that if I used su
-K, I could su to root as usual. So the problem appears to have something
to do with Kerberos.

Why is su segfaulting? Searching the mailing list archives, I found at

http://www.freebsd.org/cgi/getmsg.cgi?fetch=208472+211455+/usr/local/www/db/
text/1997/freebsd-bugs/19970615.freebsd-bugs

that there was once a bug with similar symptoms that was supposedly fixed.

I thought at first that su might have been coughing on a large group
containing 108 users, but removing the group from /etc/group didn't help.
Could Kerberos be choking on the large number of users with "*" in their
password fields in /etc/master.passwd? What else might be wrong?

If the bug seems difficult to track down, I may want to de-Kerberize the
system for now. Is there an easy way to do this? It looks as if the
Kerberos installation overwrites the original, non-Kerberized versions of
several utilities, so I can't just delete and rename some files here.
What's the best way to regress to the non-Kerberos versions if I want to do
that?

--Brett 


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