[stunnel-users] Fw: Reverse DNS lookup in stunnel log possible?

Michael D. Setzer II mikes at kuentos.guam.net
Fri Jul 26 23:17:38 CEST 2013

On 26 Jul 2013 at 11:16, mkanet at yahoo.com wrote:

Date sent:	Fri, 26 Jul 2013 11:16:22 -0700 (PDT)
From:	"mkanet at yahoo.com" <mkanet at yahoo.com>
To:	"stunnel-users at stunnel.org" <stunnel-users at stunnel.org>
Subject:	[stunnel-users] Fw: Reverse DNS lookup in stunnel log possible?
Send reply to:	"mkanet at yahoo.com" <mkanet at yahoo.com>
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> I haven't posted on this mail list in a while.  Is there anyone still
> out there?  I hope I'm sending to the correct mail-list.  Is there a
> better place I can ask my question below?
> I'm pretty sure I can't be the first person who wanted to see reverse
> DNS name lookup in the stunnel log.  I tried looking in the settings
> and documentation; but, didn't see anything related to this.
> ----- Forwarded Message -----
> I currently have stunnel strip SSL from incoming https connections;
> which then passes the connections to a proxy before ultimately
> reaching my web server.  So, the only easy way to see where incoming
> connections are coming from are in the stunnel log.
> Below, is a small example of what my stunnel log looks like (no, those
> arent the real IPs *:) happy).  The information below would be much
> more useful to me if it included the DNS names in addition to their
> numeric IP.
> I currently have the latest Windows version of stunnel installed.  It
> would be great to know how to get it to resolve DNS names as well in
> the log file; preferably without impeding general stunnel
> performance.  I tried several debug levels; but none them did reverse
> DNS lookup.  Hopefully someone know how to do this on a Windows
> stunnel setup.
> 2013.07.23 10:16:00 LOG5[10152:15136]: Service [stunnel-sslh]
> connected remote server from 2013.07.23 10:16:00
> LOG3[10152:15136]: SSL_read: Connection reset by peer (WSAECONNRESET)
> (10054) 2013.07.23 10:16:00 LOG5[10152:15136]: Connection reset: 272
> byte(s) sent to SSL, 96 byte(s) sent to socket 2013.07.23 10:17:53
> LOG5[10152:4000]: Service [stunnel-sslh] accepted connection from
> 2013.07.23 10:17:53 LOG5[10152:4000]:
> connect_blocking: connected 2013.07.23 10:17:53
> LOG5[10152:4000]: Service [stunnel-sslh] connected remote server from
> 2013.07.23 10:17:53 LOG5[10152:13212]: Service
> [stunnel-sslh] accepted connection from 2013.07.23
> 10:17:53 LOG5[10152:3348]: Service [stunnel-sslh] accepted connection
> from 2013.07.23 10:17:53 LOG5[10152:2884]: Service
> [stunnel-sslh] accepted connection from

Don't know on windows, but did a little test with a script to get the 
hostnames. First did a test using you records, and then used my 
current stunnel.log

script stlog.chk
grep -Eo '([0-9]{1,3}\.){3}[0-9]{1,3}' /var/log/stunnel.log | sort | uniq 

echo "" >stout2
for a in `cat stout` ; do 
  echo -n $a " ">>stout2; 
  host $a | awk '{print $5}' >>stout2; 

The results of stout2 are  localhost.  qe-in-f108.1e100.net.  qe-in-f109.1e100.net.  3(NXDOMAIN)  pa-in-f108.1e100.net.  pa-in-f109.1e100.net.

Probable would want to add some code to filter out private 

Final step would be to scan original log and add the name on 
each of the lines with an ip. 
  Michael D. Setzer II -  Computer Science Instructor      
  Guam Community College  Computer Center                  
  mailto:mikes at kuentos.guam.net                            
  mailto:msetzerii at gmail.com
  Guam - Where America's Day Begins                        
  G4L Disk Imaging Project maintainer 

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