Supporting X25519 and X448

[kazu-yamamoto]

https://tools.ietf.org/html/draft-ietf-tls-rfc4492bis defines:

         enum {
               deprecated(1..22),
               secp256r1 (23), secp384r1 (24), secp521r1 (25),
               x25519(29), x448(30),
               reserved (0xFE00..0xFEFF),
               deprecated(0xFF01..0xFF02),
               (0xFFFF)
           } NamedCurve;

So, I would like to do two things:

• Removing named curves from 1 to 22
• Supporting X25519 and X448 based on my TLS 1.3 branch

When my TLS 1.3 client sends a list of named curves including X25519, some TLS 1.2 server return it and the client got a pattern match failure.

% tls-simpleclient -O html-log.txt --http1.1 nghttp2.org 443          
groups = [X448,X25519,P256], keyshare = [X448]
tls-simpleclient: HandshakeFailed (Error_Misc "Network/TLS/Crypto/ECDH.hs:43:5-31: Irrefutable pattern failed for pattern Just name\n")

I want to fix this issue.

[kazu-yamamoto]

#205 resolved this.