Email Name Constraints

[jonahromero]

Hello I saw that currently name constraints aren't implemented to handle email sans. Was wondering if there'd be any problems if I were to make a PR for this? It seems the main work is just to specify what a valid email is and whether it follows said naming constraints.

For defining a valid email, implementing parsing for "Mailbox": https://datatracker.ietf.org/doc/html/rfc2821#section-4.1.2

Then the name constraints portion referring to emails: https://datatracker.ietf.org/doc/html/rfc5280#section-4.2.1.10

It seems like there's at least one other library implementing email parsing: https://docs.rs/email_address/latest/email_address/index.html, but it seems to encapsulate more than what the x509 RFC specifies, so I imagine it'd be better to just write it from scratch here. Also wasn't sure if there were any rules about introducing dependencies.

[djc]

What do you need this for?

We're definitely going to be reluctant to introduce new dependencies, especially for niche features.

[jonahromero]

I have a use case for verifying certs with email sans. Not wanting a dependency makes sense, like I mentioned no issue with that, just wanted to double check.

[djc]

I have a use case for verifying certs with email sans.

I inferred as much, and was asking for more context, so we can judge how niche your use case is and if/how it relates specifically to the web PKI.