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

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/devel@lists.fedoraproject.org/thread/VVLHQAWI3IQ7NRLKMUHJ27JV3V2JAFDP/#W73IMPJVK3DNCRXS5OZXELVWJRDRT6KN

-- 
Petr Menšík
Software Engineer
Red Hat, http://www.redhat.com/
email: pemensik@redhat.com
PGP: DFCF908DB7C87E8E529925BC4931CA5B6C9FC5CB