x/crypto/openpgp: pointer usage for rsa.PublicKey is inconsistent with crypto/x509

[mattmoyer]

What version of Go are you using (go version)?

go version go1.11 darwin/amd64

Also golang/crypto@0e37d00.

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOOS="darwin"

What did you do?

I wrote some code which implements crypto.Signer. My original use case for this was to plug into golang.org/x/crypto/openpgp so I can perform PGP signatures using my signer. To do this, I had to make my PublicKey() method return a rsa.PublicKey (no pointer) so I can pass the type check in NewSignerPrivateKey().

So far, so good.

What did you expect to see?

I expected my crypto.Signer implementation to work, without changes, with crypto/x509.

What did you see instead?

crypto/x509 also has a type check, but it checks for *rsa.PublicKey (pointer) rather than rsa.PublicKey.

It doesn't seem that I can implement one crypto.Signer that will work with both golang.org/x/crypto/openpgp and crypto/x509. I think we can fix this and keep backwards compatibility by extending the the type check in golang.org/x/crypto/openpgp 's NewSignerPrivateKey() to treat *rsa.PublicKey the same as rsa.PublicKey.

Thanks to @joemiller for originally reporting this downstream (vmware-archive/google-kms-pgp#2).

[gopherbot]

Change https://golang.org/cl/137895 mentions this issue: openpgp: allow RSA signers to return a pointer

[Merovius]

I ran into the same issue. Sorry for jumping the gun, but I didn't see this issue until after I already had the CL prepared :)