x509-cert: Constructed `Certificate` profile is always RFC 5280, ignoring the `CertificateBuilder` profile

[str4d]

CertificateBuilder always returns Certificate, regardless of its P: Profile:

formats/x509-cert/src/builder.rs

Lines 339 to 343 in e0c3e08

	impl<P> Builder for CertificateBuilder<P>
	where
	P: Profile,
	{
	type Output = Certificate;

Certificate is currently by definition always interpreted using the RFC 5280 profile:

formats/x509-cert/src/certificate.rs

Line 183 in e0c3e08

pub type Certificate = CertificateInner<Rfc5280>;

This means that anyone building with an alternate Profile will be given a Certificate that claims to have been built using the RFC 5280 profile, which is a very problematic bug.

The builder impl should instead be:

impl<P> Builder for CertificateBuilder<P>
where
    P: Profile,
{
    type Output = CertificateInner<P>;

I expect this bug went unnoticed because the Profile on Certificate currently provides zero guarantees (#1486).

[baloo]

There are two profiles here x509_cert::builder::Profile and x509_cert::certificate::Profile.
The former is used to add extensions to a certificate when building them, the latter is for parsing. Would renaming the first one BuildProfile clear up the confusion?

[str4d]

Ah, I did not realise there were two different Profile traits, because @tarcieri told me that the Profile in Certificate enforces things when using the builder API. But it sounds like that's actually what builder::Profile does. Renaming one of them would help; ideally Profile should mean one consistent thing within the crate, if used as a trait name.

Is the intention that all Certificates produced by the builder will be valid under the RFC 5820 profile, regardless of what builder::Profile is set to? And if so, is this enforceable by the builder for all builder::Profiles?