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Path: utzoo!mnetor!seismo!columbia!cheshire.columbia.edu!francus
From: francus@cheshire.columbia.edu (Yoseff Francus)
Newsgroups: comp.unix.wizards
Subject: Re: Built-in login command (/bin/lo
Message-ID: <4705@columbia.UUCP>
Date: Thu, 18-Jun-87 10:33:20 EDT
Article-I.D.: columbia.4705
Posted: Thu Jun 18 10:33:20 1987
Date-Received: Sun, 21-Jun-87 12:53:01 EDT
References: <91@decvax.UUCP> <142700003@tiger.UUCP>
Sender: nobody@columbia.UUCP
Reply-To: francus@cheshire.columbia.edu.UUCP (Yoseff Francus)
Organization: Columbia University CS Department
Lines: 34

In article <142700003@tiger.UUCP> rjd@tiger.UUCP writes:
>
>> 	Back at U. of NH, I discovered by accident that if
>> 	I ran /bin/login directly (not "exec" it, which the
>> 	builtin shell command "login" does) and logged into
>> 	an account with no password (they had a captive
>> 	account which ran /bin/who), when /bin/login exited
>> 	the entry in the /etc/utmp kept the new login name.
>> 
>> 	Then (I don't know if it is true anymore) mail used
>> 	to use the /etc/utmp entry (given by: who am i)
>> 	instead of by uid (given by: whoami).
>
>   Interesting, AT&T Sys V, release 2.0 and 3.0 's mail command uses your
>LOGNAME variable as a first choice as your ID when sending mail.  (Probably
>and unimportant bug...)
>
>rjd

Actually the LOGNAME bug was fairly serious.  LOGNAME is a shell 
variable which can normally be changed by a user.  A user could chang
their LOGNAME variable and then send mail as someone else.  On Sys V
if you look at /etc/profile you will notice that in many cases
after LOGNAME is set it is made into a readonly variable.  There are ways
around this too, but enough said.

yoseff



******************************************************************
yf
In Xanadu did Kubla Khan a stately pleasure dome decree
But only if the NFL to a franchise would agree.