*BSD News Article 21354


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Newsgroups: comp.unix.bsd
Path: sserve!newshost.anu.edu.au!munnari.oz.au!news.Hawaii.Edu!ames!elroy.jpl.nasa.gov!decwrl!netcomsv!netcom.com!netcomsv!resonex!michael
From: michael@resonex.com (Michael Bryan)
Subject: Re: Major security hole with getty, please help!
Message-ID: <1993Sep22.163651.19550@resonex.com>
Keywords: getty,security,deathtobarny
Organization: Resonex Inc., Fremont CA
References: <27noq0$lb5@news.u.washington.edu>
Date: Wed, 22 Sep 1993 16:36:51 GMT
Lines: 31

In article <27noq0$lb5@news.u.washington.edu> micah@stein1.u.washington.edu (Micah Anderson) writes:
>idle-out... So I was disconnected... I then simply call back to log in
>again, but WHOA! I didnt get a login, I was instantly connected back
>to my tty

Another reply includes the information to correct this one (making sure
your modem and system are configured properly to allow a dropped carrier
to cause SIGHUP to be delivered to all of your processes.)

>On the subject of getty I also noticed (this might offer a clue to the
>above) that when I call in utmp is NOT updated. I login and do a 'w'
>and find that noone is logged in... hmmm, all the permissions look
>right.
>
>-rw-rw-rw-  1 bin            72 Sep 21 08:39 /etc/utmp
>
>and wtmp DOES get updated...

Unless your flavor of Unix has some odd peculiarities in this regard, the
permissions on /etc/utmp and /etc/wtmp should be -rw-r--r--, so that
general users will not be able to update the files.  (When login runs,
it starts out as "root", and should update these files before switching
to your login uid.)  It's not a major issue unless you're concerned
about the security aspects of having these records modified.  And it
doesn't explain why utmp isn't updated in the first place.

-- 
Michael Bryan          michael@resonex.com         +1 510 249 9600   Ext 325
Resonex, Inc.                    ____                              ____
47911 Westinghouse Dr.           \  /    B3/4 f t- w c g++ k+ s+   \  /
Fremont, CA  94539                \/   Hate is not a family value.  \/