The tls-alpn-01 responder currently hardcodes the supplied identifier as a dnsName SAN in the challenge certificate: https://github.com/letsencrypt/challtestsrv/blob/bcea93640e39bfad2dbe3465f08040b14aa0e9a9/tlsalpnone.go#L76 This doesn't work for IP identifiers, where it needs to be encoded as an ipAddress SAN.
The tls-alpn-01 responder currently hardcodes the supplied identifier as a dnsName SAN in the challenge certificate:
challtestsrv/tlsalpnone.go
Line 76 in bcea936
This doesn't work for IP identifiers, where it needs to be encoded as an ipAddress SAN.