Success path for fake tls is implemented

tlstypes/server_hello.go

@@ -0,0 +1,92 @@
+package tlstypes
+
+import (
+	"bytes"
+	"crypto/hmac"
+	"crypto/rand"
+	"crypto/sha256"
+	"io"
+
+	"golang.org/x/crypto/curve25519"
+
+	"github.com/9seconds/mtg/config"
+)
+
+type ServerHello struct {
+	Handshake
+
+	clientHello *ClientHello
+}
+
+func (s ServerHello) WelcomePacket(hostCert []byte) []byte {
+	s.Random = [32]byte{}
+	rec := Record{
+		Type:    RecordTypeHandshake,
+		Version: Version12,
+		Data:    &s,
+	}
+	buf := bytes.NewBuffer(rec.Bytes())
+
+	recChangeCipher := Record{
+		Type:    RecordTypeChangeCipherSpec,
+		Version: Version12,
+		Data:    RawBytes([]byte{0x01}),
+	}
+	buf.Write(recChangeCipher.Bytes())
+
+	recData := Record{
+		Type:    RecordTypeApplicationData,
+		Version: Version12,
+		Data:    RawBytes(hostCert),
+	}
+	buf.Write(recData.Bytes())
+	packet := buf.Bytes()
+
+	mac := hmac.New(sha256.New, config.C.Secret)
+	mac.Write(s.clientHello.Random[:]) // nolint: errcheck
+	mac.Write(packet)                  // nolint: errcheck
+	copy(packet[11:], mac.Sum(nil))
+
+	return packet
+}
+
+func NewServerHello(clientHello *ClientHello) *ServerHello {
+	rv := &ServerHello{
+		clientHello: clientHello,
+	}
+
+	rv.Type = HandshakeTypeServer
+	rv.Version = Version12
+	rv.SessionID = make([]byte, len(clientHello.SessionID))
+	copy(rv.SessionID, clientHello.SessionID)
+
+	tail := bytes.NewBuffer(CipherSuiteType_TLS_AES_128_GCM_SHA256_Bytes)
+	tail.WriteByte(0x00) // no compression
+	makeTLSExtensions(tail)
+	rv.Tail = RawBytes(tail.Bytes())
+
+	return rv
+}
+
+func makeTLSExtensions(buf io.Writer) {
+	buf.Write([]byte{ // nolint: errcheck
+		0x00, 0x2e, // 46 bytes of data
+		0x00, 0x33, // Extension - Key Share
+		0x00, 0x24, // 36 bytes
+		0x00, 0x1d, // x25519 curve
+		0x00, 0x20, // 32 bytes of key
+	})
+
+	var dst, in, base [32]byte
+
+	rand.Read(in[:])   // nolint: errcheck
+	rand.Read(base[:]) // nolint: errcheck
+	curve25519.ScalarMult(&dst, &in, &base)
+	buf.Write(dst[:]) // nolint: errcheck
+
+	buf.Write([]byte{ // nolint: errcheck
+		0x00, 0x2b, // Extension - Supported Versions
+		0x00, 0x02, // 2 bytes are following
+		0x03, 0x04, // TLS 1.3
+	})
+}