retro-agent

We must be a little clandestine here since there's vulnerability in http cgi-bin applications.

http://holt.oso.chalmers.se/hgs/SCG/monitor-plot.html has a submit button. Look at the source code.
<form method="POST" action="http://holt.oso.chalmers.se/cgi-bin/SCG-monitor.cgi">
<input size="10" type=text name=name1 value="" >
&lt;= a date <tt><b>YYYY-MM-DD</b></tt><sup>1</sup>)
&nbsp;+&nbsp;an hour <tt><b>HH</b></tt>&nbsp;=&gt;
<input type=text name=name2 value="" size="2">
&nbsp;&nbsp;minute =&gt;
<input type=text name=name3 value="00" size="2">
                                      <!-- FIELD -->
<input type=submit><br>
<sup>1</sup>) or the word&nbsp;&nbsp;<tt><b>TODAY</b></tt>&nbsp;&nbsp;if less than 24 h ago.
<tt>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
</tt>Expect response time 10 s
<br>
</form>

In /cgi-bin/ perl-script SCG-monitor.cgi  receives the page with the parameters abutted to the address, e.g.
http://holt.oso.chalmers.se/cgi-bin/SCG-monitor.cgi?name1=2019-04-15&name2=04&name3=40&name4=10
(you could paste this into the URL-box of your browser too) and produces a new html-page editing what it has received. Which implies using the home-made markup in the form of comments to the right like
<!-- SKIP -->       for ignoring
<!-- INSERT -->     to insert the power spectrum for the requested hour 
<!-- EQWATCH -->    (and variants) to place earthquake information for the requested day
<!-- TPRENEW -->    (and a variant) to place the relevant tide-press-plot figure (upper-right diagram)

SCG-monitor.cgi doesn't have a help function nor a manual page. It is only supposed to be called by way of URL. 


The insertion of the power spectrum and other stuff associated with the requested date.
It might look overdone, but in fact the data occupies much less space than the graphics, so neither Holt or the broker would archive the diagrams. Therefore the script initiates the drawing routine. That's the part where a vulnerability might invite hackers. 
Read on at /home/hgs/Manuals/retro-agent.txt
-rw-rw---- 1 hgs users 1671 Jul 15  2018 /home/hgs/Manuals/retro-agent.txt

The short help text is

  USAGE:  
        retro-agent.pl [-q] [-one]
  PURPOSE:
           Catches requests from monitor-plot.html via the cgi-bin script
           for displaying old SCG data.

           Does only one trip if a file ONETRIPRETRO is present in that ominous, secret directory.
           Stops immediately if a file STOPRETRO is present.
           STOPRETRO is automatically removed,  ONETRIPRETRO not.

  OPTIONS:
    -q    - run quietly.
    -one  - do one trip and stop, for debug. -q isn't too cunning then.