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No, it's because the SCTs in the certificate have invalid signatures.

Ah, that makes sense!

I wonder if we should be doing some basic sanity checks on newly obtained certificates in Caddy, and treat this as a failure, and try the next configured CA instead.

(Obviously SCT signatures will require some external resource so we would have to weigh that a bit more, maybe make it configurable...)

Issue opened here to discuss, though it does sound troublesome/tedious: https://github.com/caddyserver/certmagic/issues/240

Yeah, the question is how far you want to go. To be safe against every possible CA screwup, you basically have to re-implement every browser's entire certificate validation engine and run certificates through each one. That would obviously be very hard, and could do more harm than good if it falls out-of-sync with browsers.

It would make sense to try to check this, if there's a reasonable way to access a database of trusted certificate logs. If not, it's going to be tricky; I wouldn't fail a certificate that had a SCT from an unknown log, because it might be valid and you don't know. Etc.

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