Having read the post mortem, I disagree. Slack engineers did something dumb, under pressure during an outage. Even if they hadn't, they still would have been in a degraded state until they could properly remove their DNSSEC records and/or get the Route53 bug they hit fixed. In other words, they still would have had a 24+ hour outage, albeit with a smaller blast radius.

The design of DNSSEC is simply not fit for purpose for zone operators. It is far too easy to screw your zone up for far too marginal a benefit, to say nothing of the huge increase in CPU resource required to authenticate DNSSEC record chains.

The story for implementers is just as bad - the specifications are baroque, filled with lousy crypto and poorly thought-out options.

To give just one example, consider the NSEC3 iteration limit field. NSEC3 itself was designed mostly[0] to prevent zone enumeration when validating negative responses (which is trivial to perform with NSEC.) The iteration count was designed to give zone operators the ability to increase the cost to an attacker of generating a dictionary of nsec3 names[1]. Of course, a high iteration count also raises the cost to a non-malicious resolver of validating a negative response for a nsec3-enabled zone.

In good old DNSSEC fashion, the iterations field is a single number that is subject to a... wide variety of potential limits:

* 16 bits by the wire protocol

* 150 for 1,024 bit keys (RFC 5155 10.3[2])

* 500 for 2,048 bit keys (RFC 5155 10.3[2])

* 2,500 for 4,096 bit keys (RFC 5155 10.3[2])

* 0 (RFC 9276 3.2)

Why 0? It was noted -- after publishing the NSEC3 spec -- that high iterations just don't provide that much benefit, and come with a high cost to throughput. Appendix B of RFC 9276 shows a roughly 50% performance degradation with an iteration count of 100. So, RFC 9276 3.2 says:

  Validating resolvers MAY also return a SERVFAIL response when processing NSEC3 records with iterations larger than 0.

Of course, their guidance to implementers is to set the limits a bit higher, returning insecure responses at 100 iterations and SERVFAIL at 500. That said, if you want to be maximally interoperable, as a zone operator, you should pretend like the iteration count field doesn't exist: it is standards compliant for a validating resolver to refuse an nsec3 response with more than a single hash round.

As I said, this is one example, but I'm not cherry picking here. The whole of the DNSSEC spec corpus is filled with incomprehensible verbiage and opportunities for conflicting interpretations, far beyond what you see in most protocol specs.

0 - also to reduce the size of signed top-level zones

1 - all NSEC and NSEC3 records, while responsive to queries about names that don't exist, consist of obfuscated names that do exist.

2 - According to the letter of the standard, the limits applied to the iterations field should be 149, 499, and 2,499. Implementations are inconsistent about this.