[SR-Users] Debian, dnssec.so, and missing dnsval.conf

[Daniel-Constantin Mierla]

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


On 13/05/16 20:48, David Holl wrote:
> 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 at 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
http://twitter.com/#!/miconda - http://www.linkedin.com/in/miconda
Kamailio World Conference, Berlin, May 18-20, 2016 - http://www.kamailioworld.com

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