Ctls is a fork of go crypto/tls to add the TLS Extension into ClientHello info as implemented there : https://go-review.googlesource.com/c/go/+/471396
You can then retrieve it by GetCertificat or GetConfigForClient or directly in tls.Con callback from tls.Config :
package main
func main(){
cer, err := tls.LoadX509KeyPair("cert.crt", "key.key")
if err != nil {
return nil, err
}
tlsConfig := &tls.Config{
Certificates: []tls.Certificate{cer},
}
tlsConfig.GetConfigForClient = func(chi *tls.ClientHelloInfo) (*tls.Config, error) {
CipherSuites := chi.CipherSuites
ServerName := chi.ServerName
SupportedCurves := chi.SupportedCurves
SupportedPoints := chi.SupportedPoints
SupportedVersions := chi.SupportedVersions
Extensions := chi.Extensions
/* ... */
}
}in tls.Con
if tlsCon, ok := con.(*tls.Conn); ok && tlsCon != nil {
chi := tlsCon.ClientHelloInfo
/* ... */
}