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<TITLE>The Answer Guy 39: Seeing Stars During Login</TITLE>
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<H4>"The Linux Gazette...<I>making Linux just a little more fun!</I>"</H4>
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<H4>By James T. Dennis,
<a href="mailto:answerguy@ssc.com">answerguy@ssc.com</a><BR>
LinuxCare,
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<H3 align="left"><img src="../../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>Seeing Stars During Login</H3>
<h4 align="center">Re: login source code</h4>
<p><strong>From john walshe on Tue, 09 Mar 1999
</strong></p>
<!-- ::
Seeing Stars During Login
~~~~~~~~~~~~~~~~~~~~~~~~~
:: -->
<P><STRONG>
Hi Jim,
</STRONG></P>
<P><STRONG>
I am wondering how you would get the <tt>*</tt> to come up on a screen
for each character pressed when someone is entering a login password on
a unix platform.
</STRONG></P>
<P><STRONG>
Thanks,
John.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
As your subject suggests, you'd have to modify the sources
to the '<tt>login</tt>' program. You'd have to put the terminal
in a particular mode so you're getting each character
(rather than getting whole lines at a time). This is
possible on any terminal through which one can run '<tt>vi</tt>'
'<tt>emacs</tt>' or any other full screen text program. However,
the existing '<tt>login</tt>' programs, and your shell, and
the '<tt>ex</tt>' (or '<tt>ed</tt>') line editors don't require this ---
so they can still be used with teletype devices.
</BLOCKQUOTE>
<BLOCKQUOTE>
I suspect that this is at least one reason why the
login program doesn't provide visual cues for each
character you type. Another is that it would reveal
the length of your password to any shoulder surfers
in your vicinity any time you logged in.
</BLOCKQUOTE>
<BLOCKQUOTE>
I was amused that the Lotus Notes login dialog (under
Windows) would spit out a random number of <tt>*</tt>'s for every
keystroke you entered in the password field of the dialog.
So you knew that the keyboard was responding --- but
couldn't tell if you'd "bounced" some keys. That
doesn't seem like much of a "solution."
</BLOCKQUOTE>
<BLOCKQUOTE>
In any event --- feel free to play with it. Understand
that '<tt>login</tt>' is a security sensitive program. The slightest
mistake you make there can probably be exploited to
take over your whole system. So, I wouldn't deploy this
on exposed servers unless you are <EM>very</EM> sure of your
programming skills (or very foolhardy --- as the case
would more likely be).
</BLOCKQUOTE>
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<H5 align="center"><a href="http://www.linuxgazette.com/ssc.copying.html"
>Copyright ©</a> 1999, James T. Dennis
<BR>Published in <I>The Linux Gazette</I> Issue 39 April 1999</H5>
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