Hickory-DNS 0.26.0 before 0.26.2 DNSSEC Nonexistence Forgery via Wraparound NSEC

The DNSSEC validation in the Hickory DNS hickory-net crate 0.26.0 before 0.26.2 identifies wraparound NSEC records by comparing the next domain name to an SOA record in the response, accepting that SOA even if it fails validation. Attackers who can supply DNS responses can combine a genuine NSEC record and its RRSIG with a crafted SOA record to forge nonexistence of any RRset.

The DNSSEC validation in the Hickory DNS hickory-net crate 0.26.0 before 0.26.2 identifies wraparound NSEC records by comparing the next domain name to an SOA record in the response, accepting that SOA even if it fails validation. Attackers who can supply DNS responses can combine a genuine NSEC record and its RRSIG with a crafted SOA record to forge nonexistence of any RRset.

The DNSSEC validation in the Hickory DNS hickory-net crate 0.26.0 before 0.26.2 identifies wraparound NSEC records by comparing the next domain name to an SOA record in the response, accepting that SOA even if it fails validation. Attackers who can supply DNS responses can combine a genuine NSEC record and its RRSIG with a crafted SOA record to forge nonexistence of any RRset.

The last NSEC record in a zone points back to the zone apex. To recognise it, DNSSEC validation treated an NSEC record as covering every name after its owner when its next domain name equalled the owner name of an SOA record in the response. That SOA record did not have to pass validation. An attacker who can answer or modify DNS responses can replay a genuine NSEC record and its RRSIG, add a forged SOA record whose name equals that NSEC record's next domain name, and so make the validator accept that any name sorting after the NSEC owner does not exist. This affects DNSSEC validation through `DnssecDnsHandle` when built with `dnssec-ring` or `dnssec-aws-lc-rs`. The fix recognises a wraparound NSEC record from the chain itself (its next domain name sorts at or before its owner and is the zone of the queried name) and only uses validated SOA records. It is in 0.26.2.