Updated recommendations regarding TOFU & TLS
sir at cmpwn.com
Thu Mar 4 16:43:49 GMT 2021
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Hello! I have recently announced some upcoming changes to my Gemini
software implementations with respect to TLS and TOFU:
I've also updated my older TOFU recommendations article to reflect the
In short, after listening to some feedback from the community on TOFU,
I'd like to make the following updated suggestions:
- Use long-lived certificates with the expiration set to the far future
- Client software should disregard notBefore/notAfter dates, and the
common name as well. Requiring strong algorithms and other technical
constraints is fine.
Any server software which wants to migrate to long-lived certificates
should let their current certificates expire and then automatically
issue a long-lived certificate to replace it when the time comes, rather
than switching immediately and causing your clients to flag your cert as
To re-state one of my previous recommendations, which I still figure is
a good idea: server software should handle certificate maintenance for
the user. Making the sysadmin generate certificates is cumbersome and
error prone, and because Gemini encourages TOFU and self-signed
certificates, we can remove that burden from server operators entirely
by generating certificates on-demand for the hosts we intend to service.
Aside: it might be a good idea to have a non-authoratitive TLS
best-practices document on gemini.circumlunar.space somewhere. I'd be
happy to draft up such a document if this is desirable.
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