8245686: Ed25519 and Ed448 present in handshake messages

[Anthony Scarpino]

Hi,

I need a code review of this very simple change for a situation that I'm 
not sure is a problem in the real world.

The original TLS 1.3 putback added EdDSA to the TLS signature extensions 
enumeration before there was an EdDSA JCE implementation or JSSE 
support.  Without an implementation, a signature checks would not 
include EdDSA for TLS extensions, signature_algorithms and 
signature_algorithm_cert.  Now with JCE EdDSA support, the signature 
check adds EdDSA to the extension, despite JSSE not having support yet 
(JDK-8166596).  This causes a signature scheme authentication failure, 
and JSSE moves onto the next certificate provided.

The only time this is a problem is if EdDSA is the only cert provided. 
I'm not sure how realistic it is for one certificate to be provided.  If 
someone knows multiple certificates are always available, I'm happy to 
not make this change.

The fix is a simple check in the constructor to set the curves 
unavailable after the signature check.  This code can be deleted when 
JDK-8166596 is fixed in jdk16.  I had thought about commenting out the 
enums, but then the logging code would not know what the id's were when 
other clients and servers passed them to JSSE.

https://cr.openjdk.java.net/~ascarpino/8245686/webrev/

Tony