add PKCS11 support (#1153)

* add PKCS11 support

* add pkcs11 build option to the makefile, add a stub pkclient to avoid forcing CGO onto people

* don't print the pkcs11 option on nebula-cert keygen if not compiled in

* remove linux-arm64-pkcs11 from the all target to fix CI

* correctly serialize ec keys

* nebula-cert: support PKCS#11 for sign and ca

* fix gofmt lint

* clean up some logic with regard to closing sessions

* pkclient: handle empty correctly for TPM2

* Update Makefile and Actions

---------

Co-authored-by: Morgan Jones <me@numin.it>
Co-authored-by: John Maguire <contact@johnmaguire.me>

connection_state.go

@@ -32,7 +32,11 @@ func NewConnectionState(l *logrus.Logger, cipher string, certState *CertState, i
 	case cert.Curve_CURVE25519:
 		dhFunc = noise.DH25519
 	case cert.Curve_P256:
-		dhFunc = noiseutil.DHP256
+		if certState.Certificate.Pkcs11Backed {
+			dhFunc = noiseutil.DHP256PKCS11
+		} else {
+			dhFunc = noiseutil.DHP256
+		}
 	default:
 		l.Errorf("invalid curve: %s", certState.Certificate.Details.Curve)
 		return nil