Hi,
Apart from DNSSEC validation, have you also tested DNS servers hosting
DNSSEC signed zones with NSEC3? This is since NSEC3 only has SHA1
specified
<https://www.iana.org/assignments/dnssec-nsec3-parameters/dnssec-nsec3-parameters.xhtml>
and this may cause the DNS server unable to update the zone to create
new NSEC3 records. This will mean that even if the zone is signed with
ECDSA algorithms but use NSEC3 then they are going to fail.
Regards,
*Shreyas Zare*
Technitium <https://technitium.com/>
On 4/13/2022 10:36 PM, Petr Menšík wrote:
Hello DNS users,
I have already created some bugs to inform some affected software
packages. But I would like to notify also here with prepared plan to
obsolete SHA-1 in upcoming RHEL 9.0. Final documentation is not yet
created for it, but it could be tested already on centos container:
docker pull quay.io/centos/centos:stream9
delv command from bind-utils or unbound-host -D from unbound can test
it. delv would still fail, because it does not follow crypto-policy
configuration which named consumes.
I have filled tracker bug for EPEL9 components I know on bug #2073066
[1]. If your software validates DNSSEC signatures, it might start
failing on domain names signed with RSASHA1 or NSEC3RSASHA1
algorithms. If you have package validating DNSSEC on EPEL9 which I
have not mentioned and it is affected, please create a bug blocking
this tracker bug. If have created the bug but is not affected, please
close it with NOTABUG.
Crypto-policy DEFAULT makes some openssl or gnutls methods to fail,
when RSASHA-1 key is used. That includes openssl function
EVP_VerifyFinal (used in bind) and EVP_DigestVerifyInit (used in
unbound). Because used crypto policy DEFAULT prevents such signature
verification, DNSSEC validators may start to return failures on those
names.
A simple workaround would be switching to crypto policy DEFAULT:SHA1:
update-crypto-policies --set DEFAULT:SHA1
I have created list to TLD affected and attached them to the bug [2].
But it includes many more names, such as icann.org, ietf.org or
paypal.com.
I know it violates still active RFC 8624 [3], but because it is
enforced by lower-level API, it is possible just to follow or fail. I
think so far every crypto call failure results in bogus result and
returns status SERVFAIL on the reply. Would it make sense to create
some common cases, where the result would be fallback to insecure
reply without AD bit, but no failure?
Supported bind and unbound packages will start considering those names
as insecure to prevent validation failures. There has been interesting
conversation on mattermost Town Square [4] on this topic. Worth noting
might be also threads on unbound [5] and Fedora discussion about
implementing the same way [6].
Best Regards,
Petr
1. https://bugzilla.redhat.com/show_bug.cgi?id=2073066
2. https://bugzilla.redhat.com/show_bug.cgi?id=2073066#c7
3. https://datatracker.ietf.org/doc/html/rfc8624#section-3.1
4. https://chat.dns-oarc.net/community/channels/town-square
5.
https://lists.nlnetlabs.nl/pipermail/unbound-users/2022-April/007709.html
6.
https://lists.fedoraproject.org/archives/list/[email protected]/thread/VVLHQAWI3IQ7NRLKMUHJ27JV3V2JAFDP/#W73IMPJVK3DNCRXS5OZXELVWJRDRT6KN
--
Petr Menšík
Software Engineer
Red Hat,http://www.redhat.com/
email:[email protected]
PGP: DFCF908DB7C87E8E529925BC4931CA5B6C9FC5CB
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