proposal: crypto/x509: create typed versions of ParsePKCS8PrivateKey

[HaraldNordgren]

It bothers me that me as an end-user of ParsePKCS8PrivateKey have to do type assertion logic on the key even when you know what you expect.

We should utilize Go's strong type system to create type-specific functions called for example

• ParsePKCS8PrivateKeyRSA(der []byte) (key *rsa.PrivateKey, err error)
• ParsePKCS8PrivateKeyECDSA(der []byte) (key *ecdsa.PrivateKey, err error)

[gopherbot]

Change https://golang.org/cl/125056 mentions this issue: crypto/x509: create typed versions of ParsePKCS8PrivateKey

[bcmills]

CC @FiloSottile

[adamdecaf]

I'm indifferent, but adding new methods adds to the overall api surface, which has its own problems with maintenance.

[adamdecaf]

@gopherbot proposal-crypto

[odeke-em]

I've retitled this as a proposal as it hasn't been looked at since Go1.11 but it is a proposal that we have to examine and decide on.

[FiloSottile]

I agree with Adam (https://go-review.googlesource.com/c/go/+/125056/4#message-46b6bcfdedbc7383393b0e37c5a640be477bd615) that the increased API surface is not worth it. There is already a dizzying array of Parse functions in crypto/x509, and the type assertion is not much more work than checking the error.