Hello,

thanks for providing all the details getting the dnssec sorted out with dnsval.conf. It is really useful.

If you have the time, would be good to add those details in the readme file for dnssec -- you cna make a pull request for the file modules/dnssec/doc/dnssec_admin.xml

The alternative would be to add to the wiki:

  - https://www.kamailio.org/wiki/tutorials/dns/dnssec

Cheers,
Daniel

In the interest of sharing and promoting DNSSEC, I was recently stumped on a problem where I noticed I could not call sip:test.echo@sip5060.net without disabling the dnssec.so module in my kamailio.cfg.  The last time I had tried the sip5060 echo test was several months ago, and in the intervening time, I had applied the numerous debian package updates.  Thus, I could not isolate the cause of the problem to one of the many package updates such as kamailio 4.4.x, libval, my own DNSSEC dns server, etc...  My initial only clue was kamailio's syslog messages:

May 12 18:02:49 tensor /usr/sbin/kamailio[24128]: ERROR: tm [ut.h:296]: uri2dst2(): ERROR: uri2dst: failed to resolve "sip5060.net" :unresolvable A or AAAA request (-7)
May 12 18:02:49 tensor /usr/sbin/kamailio[24128]: ERROR: tm [t_fwd.c:1712]: t_forward_nonack(): ERROR: t_forward_nonack: failure to add branches

May 12 18:02:49 tensor /usr/sbin/kamailio[24128]: ERROR: sl [sl_funcs.c:363]: sl_reply_error(): ERROR: sl_reply_error used: Unresolvable destination (478/SL)



To summarize the problem, I found that kamailio's dnssec.so was failing queries to domains that were not DNSSEC protected such as sip5060.net.  This behavior is a bug, since sip5060.net is in this case, provably not participating in DNSSEC from the toplevel "net." zone [1].



The fix was to provide a default configuration file to libval, which was somehow not included in Debian's libval15 package.  I created the following configuration from the default dnsval.conf in the source distribution:
https://dnssec-tools.org/download/dnsval-2.2.tar.gz
https://dnssec-tools.org/download/dnsval-2.2.tar.gz.asc
as well as their wiki:
https://www.dnssec-tools.org/wiki/index.php/Dnsval.conf

cat << 'EOF' > /etc/dnssec-tools/dnsval.conf
##################################
# Global Options ##################################

global-options
   trust-oob-answers yes
   # I'm running a DNSSEC nameserver locally,
   # so 4 KiB queries to localhost should be OK:
   edns0-size 4096
   env-policy disable
   app-policy disable
   rec-fallback no
;

: trust-anchor
        .  DS  19036  8  2  49AAC11D7B6F6446702E54A1607371607A1A41855200FD2CE1CDDE32F24E8FB5
;

: zone-security-expectation
        . validate
;

: provably-insecure-status
        . trusted
;

: clock-skew
        . 0
;
EOF



In summary: I find it odd that a default dnsval.conf was not included with my system's normal installation of the "libval15:amd64" package, version 2.2-4.  After providing dnsval.conf, kamailio's dnssec.so was happy again.

Side notes:

*  To identify the directory for dnsval.conf, run
    libval-config --dnsval-config
On Debian, libval-config is in the libval-dev pacakge, and this package includes a man page for dnsval.conf as well.

*  To test your libval and dnsval.conf, try
    dt-validate -s
On Debian, dt-validate is in the libval-bin package.


- David


[1] -- Authenticated denial of existence:
https://tools.ietf.org/html/rfc5155
https://tools.ietf.org/html/rfc7129
And for sip5060.net, there's an NSEC3 record in the top level net. zone proving non-existance of sip5060.net DS records:
http://dnsviz.net/d/sip5060.net/dnssec/
Translation: sip5060.net provably not enabled DNSEC.

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-- 
Daniel-Constantin Mierla
http://www.asipto.com
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