There is one much more point against automated renewal from server. If an attacker can gain access to one server he can not only steal the private key for this server (certificate compromised) but also can steal the account credentials for letsencrypt. And this is an much higher security risk.
Seeing as the “account credentials” consist of a keypair, easily cycled, and you can revoke a certificate with either the account key or the certificate key, there are two problems I see remaining:
- the attacker can request the Registration Object and get your phone number/email
- the attacker can use MAC-Based Recovery to transfer your authorizations to their account
So, it looks like the conclusion is that to recover from an account key compromise, we need a way to revoke domain authorizations?
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I agree that there should be a way to revoke domain authorizations in situations like this. However this should be a last resort type thing as your server should have a perimeter of defense in its security plans. But then again not everyone secures their servers the same way. So yeah definitely agree.
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And for stateless clients, they can generate certificates for such domains even if there is no currently valid authorizations, if I’m not mistaken: XSS via ACME implementations
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