thinking

lib/backend/backends/v0/server.go

 package backends
 
 import (
-	"log"
+	"errors"
 	"net"
 
 	"pggat2/lib/backend"
@@ -47,7 +47,40 @@ func (T *Server) accept() error {
 		return err
 	}
 
-	log.Printf("%#v", auth)
+	reader := packet.MakeReader(auth)
+	switch reader.Type() {
+	case packet.Authentication:
+		method, ok := reader.Int32()
+		if !ok {
+			return errors.New("expected authentication method")
+		}
+		// they have more authentication methods than there are pokemon
+		switch method {
+		case 0:
+			// we're good to go, that was easy
+		case 2:
+			return errors.New("kerberos v5 is not supported")
+		case 3:
+			return errors.New("cleartext is not supported")
+		case 5:
+			return errors.New("md5 password is not supported")
+		case 6:
+			return errors.New("scm credential is not supported")
+		case 7:
+			return errors.New("gss is not supported")
+		case 9:
+			return errors.New("sspi is not supported")
+		case 10:
+			return errors.New("sasl is not supported")
+		default:
+			return errors.New("unknown authentication method")
+		}
+	case packet.ErrorResponse:
+		return errors.New("backend errored")
+	case packet.NegotiateProtocolVersion:
+		// we only support 3.0 as of now
+		return errors.New("unsupported protocol version")
+	}
 
 	return nil
 }