Support loading PEM files without rehash names

[arilou]

Before I go on and send a PR about this, I wanted to make sure you guys agree with this change.

Basically today rustls-native-certs follows the same logic as OpenSSL in regards of loading certificates only if they have a value
rehash name.

As far as I understand from OpenSSL this is used mainly as a performance reasons for the case there are many certificates in
a given directory and it will help "identify" the correct one.

Looking at other implementations for loading certificates from the SSL_CERT_DIR you can see here in Go
https://go.dev/src/crypto/x509/root_unix.go
That they dont enforce the rehash names, and simply loads all the certificates in the directory.

I was wondering if you will be willing to have the same type logic as the Go variant which is more permissive.

[djc]

Why? What's your use case?

[arilou]

We've encountered environments, often customer setups where the base image is optimized for Go applications. These images typically work out-of-the-box with Go's certificate loading logic. However, when running Rust applications in the same images, no certificates are loaded at all, leading to TLS failures.

[djc]

Sounds reasonable (who's we?). Would you be able to submit a PR in this direction?

[arilou]

Wiz (https://www.wiz.io/) and sure ill build some PR, just to make sure we are clear on the direction, I'm removing the re_hash requirements on the loading of the PEMs
Basically remove the check of is_hash_file_name(file_name) in the function load_pem_certs_from_dir

[djc]

Makes sense. We might want to consider if this should be optional behavior and if so, whether it should be opt-in or opt-out.