Migrate SPKI parsing from OpenSSL to Rust

[alex]

TODO:

• Handle unsupported key types
• Handle un-named EC keys
• Figure out how to handle DHX stuff (DH_set_flags(dh, DH_FLAG_TYPE_DHX))
• More EC curves?
• rust-openssl release
• Figure out the RHEL issue
• Missing EC coverage
  • Private key with explicit curve parameters
  • Private key with an unsupported curve
  • Loading keys with obscure curves:
    • SECT163K1
    • SECT233K1
    • SECT163R2
    • SECT233R1

[tamird]

This seems to be stricter than OpenSSL. In particular, some keys with BEGIN RSA PUBLIC KEY which previously decoded without error no longer do until changed to BEGIN PUBLIC KEY.

[alex]

@tamird can you file a new ticket with the details of the issue and an example public key?

It sounds like this is a full SPKI but using the BEGIN RSA PUBLIC KEY header (which is usually for PKCS1 keys).

[tamird]

It looks like the key was indeed not correct, passing it through openssl rsa -pubin -pubout strips "RSA" from the header and footer.

Just flagging that this is a behavior change.