send non-default curve during a handshake

cert/cert_v2.go

@@ -231,7 +231,16 @@ func (c *certificateV2) MarshalForHandshakes() ([]byte, error) {
 		//TODO: panic on nil rawDetails
 		b.AddBytes(c.rawDetails)
 
-		// Skipping the curve and public key since those come across in a different part of the handshake
+		// Skipping public key since those come across in a different part of the handshake
+
+		//todo is curve skippable? I don't think so?
+
+		// Add the curve only if its not the default value
+		if c.curve != Curve_CURVE25519 {
+			b.AddASN1(TagCertCurve, func(b *cryptobyte.Builder) {
+				b.AddBytes([]byte{byte(c.curve)})
+			})
+		}
 
 		// Add the signature
 		b.AddASN1(TagCertSignature, func(b *cryptobyte.Builder) {