Add additional restrictions on the TLS certificate

[Demi-Marie]

• Require the NamedCurve encoding of elliptic curve parameters to prevent “Whose Curve Is It Anyway” attacks.
• Forbid the subjectUniqueId and issuerUniqueId fields in certificates. These fields are essentially unused, and the Rust implementation rejects certificates that have them.
• Require that optional NULL parameters of RSA-PSS AlgorithmIds be omitted. This corresponds to a SHOULD in RFC8017 and simplifies verification.
• Forbid hash algorithms with output length less than 256 bits to prevent collision attacks.

[Demi-Marie]

Require that optional NULL parameters of RSA-PSS AlgorithmIds be omitted. This corresponds to a SHOULD in RFC8017 and simplifies verification.

Why do we make this a MUST? I'm not sure how I would implement a check for that in Go.

It’s a MUST on the generation side, not on the use side. The behavior on the use side is unspecified. libp2p-go-tls doesn’t use RSA-PSS for generating certificates, so it isn’t affected.

That said, this isn’t particularly important, as libp2p-quic now supports all four valid encodings. I will remove it.

[Demi-Marie]

@marten-seemann can you re-review?

[Demi-Marie]

@marten-seemann ping

[Stebalien]

Thank you both! :heart: