systemd-resolved DNSSEC root trust anchor outdated ?

[J Doe]

> On 2019-01-12 9:36 a.m., Marc Deslauriers wrote:
>> On 2019-01-11 11:01 p.m., J Doe wrote:
>>> Hello,
>>> 
>>> I currently run a server using Ubuntu 18.04.1 LTS with patches current to today (Jan 11, 2019).  I configured systemd-resolved to use DNSSEC validation by editing: /etc/systemd/resolved.conf and setting: DNSSEC=yes.
>>> 
>>> When I check my syslog, I note that systemd-resolved is logging that the positive trust anchor for the root has been revoked:
>>> 
>>> Jan 11 17:59:48 server systemd-resolved[728]: DNSSEC Trust anchor . IN DS 19036 8 2 49aac11d7b6f6446702e54a1607371607a1a41855200fd2ce1cdde32f24e8fb5 has been revoked. Please update the trust anchor, or upgrade your operating system.
>>> 
>>> I checked: man dnssec-trust-anchors.d and read:
>>> 
>>> "Note that systemd-resolved will automatically use a built-in trust anchor key for the Internet root domain if no positive trust anchors are defined for the root domain.”
>>> 
>>> I verified that: /etc/dnssec-trust-anchors.d/*.positive, /run/dnssec-trust-anchors.d/*.positive, /usr/lib/dnssec-trust-anchors.d/*.positive do *NOT* exist, which means that only the compiled in root trust anchor key is being used and that systemd-resolved has found that it has been revoked.
>>> 
>>> Does this require a new root trust anchor to be compiled in and then shipped in a systemd update or should I manually acquire the root trust anchor and place it in one of the directories mentioned in: man dnssec-trust-anchors.d ?
>>> 
>>> For the meantime, I have disabled DNSSEC validation in: /etc/systemd/resolved.conf
>>> 
>>> Thanks,
>>> 
>>> - J
>>> 
>> 
>> It looks like resolved in 18.04 does in fact contain both the old and new trusty
>> anchors hardcoded in resolved-dns-trusty-anchor.c. A quick look at the file
>> suggests the expired one then gets removed from the list and the warning is issued.
>> 
>> Do you only get the warning once?
>> 
>> Marc.
>> 
> 
> Wow, I managed to typo "trust" as "trusty" twice. Stupid muscle memory ;)
> 
> Marc.

Hi Marc,

Ha ha, that’s ok - I understood what you meant re: trust/trusty!

Yes, I receive the warning for the one expired trust anchor.  To test this I:

    * Enabled DNSSEC validation in: /etc/systemd/resolved.conf

    * Restarted systemd-resolved

    * Verified that DNSSEC validation was available via: sudo systemd-resolve --status

    * Exercised the DNSSEC validation functionality with a DNSSEC enabled site: systemd-resolve www.ietf.org

Upon the last step, this triggers the single warning message in syslog about the one outdated root trust anchor but as the result of that step I can see that the data was authenticated.

Originally, I thought after I ran that last step that DNSSEC validation *failed* but I was incorrect.

- J