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142 lines
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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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<P> <hr> <P>
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<H1><A NAME="answer">
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<font color="#B03060">The Answer Guy</font>
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<BR>
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<H4>By James T. Dennis,
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<a href="mailto:linux-questions-only@ssc.com">linux-questions-only@ssc.com</a><BR>
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LinuxCare,
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<A HREF="http://www.linuxcare.com/">http://www.linuxcare.com/</A>
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<H3 align="left"><img src="../../gx/dennis/qbubble.gif"
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height="50" width="60" alt="(?) " border="0"
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>Seeing Stars During Login</H3>
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<h4 align="center">Re: login source code</h4>
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<p><strong>From john walshe on Tue, 09 Mar 1999
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</strong></p>
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<!-- ::
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Seeing Stars During Login
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~~~~~~~~~~~~~~~~~~~~~~~~~
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:: -->
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<P><STRONG>
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Hi Jim,
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</STRONG></P>
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<P><STRONG>
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I am wondering how you would get the <tt>*</tt> to come up on a screen
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for each character pressed when someone is entering a login password on
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a unix platform.
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</STRONG></P>
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<P><STRONG>
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Thanks,
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John.
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</STRONG></P>
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<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
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HEIGHT="28" WIDTH="50" BORDER="0"
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>
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As your subject suggests, you'd have to modify the sources
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to the '<tt>login</tt>' program. You'd have to put the terminal
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in a particular mode so you're getting each character
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(rather than getting whole lines at a time). This is
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possible on any terminal through which one can run '<tt>vi</tt>'
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'<tt>emacs</tt>' or any other full screen text program. However,
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the existing '<tt>login</tt>' programs, and your shell, and
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the '<tt>ex</tt>' (or '<tt>ed</tt>') line editors don't require this ---
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so they can still be used with teletype devices.
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</BLOCKQUOTE>
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<BLOCKQUOTE>
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I suspect that this is at least one reason why the
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login program doesn't provide visual cues for each
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character you type. Another is that it would reveal
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the length of your password to any shoulder surfers
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in your vicinity any time you logged in.
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</BLOCKQUOTE>
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<BLOCKQUOTE>
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I was amused that the Lotus Notes login dialog (under
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Windows) would spit out a random number of <tt>*</tt>'s for every
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keystroke you entered in the password field of the dialog.
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So you knew that the keyboard was responding --- but
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couldn't tell if you'd "bounced" some keys. That
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doesn't seem like much of a "solution."
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</BLOCKQUOTE>
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<BLOCKQUOTE>
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In any event --- feel free to play with it. Understand
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that '<tt>login</tt>' is a security sensitive program. The slightest
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mistake you make there can probably be exploited to
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take over your whole system. So, I wouldn't deploy this
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on exposed servers unless you are <EM>very</EM> sure of your
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programming skills (or very foolhardy --- as the case
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would more likely be).
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</BLOCKQUOTE>
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<P> <hr> <P>
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<H5 align="center"><a href="http://www.linuxgazette.com/copying.html"
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>Copyright ©</a> 1999, James T. Dennis
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<BR>Published in <I>The Linux Gazette</I> Issue 39 April 1999</H5>
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