Add MakeConnWithCompleteHandshake function (#18)

Add MakeConnWithCompleteHandshake function + regression test and usage example

u_conn.go

@@ -496,6 +496,62 @@ func (uconn *UConn) SetTLSVers(minTLSVers, maxTLSVers uint16) error {
 	return nil
 }
 
+func (uconn *UConn) SetUnderlyingConn(c net.Conn) {
+	uconn.Conn.conn = c
+}
+
+func (uconn *UConn) SetNetConn(c net.Conn) {
+	uconn.Conn.conn = c
+}
+
+// MakeConnWithCompleteHandshake allows to forge both server and client side TLS connections.
+// Major Hack Alert.
+func MakeConnWithCompleteHandshake(tcpConn net.Conn, version uint16, cipherSuite uint16, masterSecret []byte, clientRandom []byte, serverRandom []byte, isClient bool) *Conn {
+	tlsConn := &Conn{conn: tcpConn, config: &Config{}, isClient: isClient}
+	cs := cipherSuiteByID(cipherSuite)
+
+	// This is mostly borrowed from establishKeys()
+	clientMAC, serverMAC, clientKey, serverKey, clientIV, serverIV :=
+		keysFromMasterSecret(version, cs, masterSecret, clientRandom, serverRandom,
+			cs.macLen, cs.keyLen, cs.ivLen)
+
+	var clientCipher, serverCipher interface{}
+	var clientHash, serverHash macFunction
+	if cs.cipher != nil {
+		clientCipher = cs.cipher(clientKey, clientIV, true /* for reading */)
+		clientHash = cs.mac(version, clientMAC)
+		serverCipher = cs.cipher(serverKey, serverIV, false /* not for reading */)
+		serverHash = cs.mac(version, serverMAC)
+	} else {
+		clientCipher = cs.aead(clientKey, clientIV)
+		serverCipher = cs.aead(serverKey, serverIV)
+	}
+
+	if isClient {
+		tlsConn.in.prepareCipherSpec(version, serverCipher, serverHash)
+		tlsConn.out.prepareCipherSpec(version, clientCipher, clientHash)
+	} else {
+		tlsConn.in.prepareCipherSpec(version, clientCipher, clientHash)
+		tlsConn.out.prepareCipherSpec(version, serverCipher, serverHash)
+	}
+
+	// skip the handshake states
+	tlsConn.handshakeStatus = 1
+	tlsConn.cipherSuite = cipherSuite
+	tlsConn.haveVers = true
+	tlsConn.vers = version
+
+	// Update to the new cipher specs
+	// and consume the finished messages
+	tlsConn.in.changeCipherSpec()
+	tlsConn.out.changeCipherSpec()
+
+	tlsConn.in.incSeq()
+	tlsConn.out.incSeq()
+
+	return tlsConn
+}
+
 func makeSupportedVersions(minVers, maxVers uint16) []uint16 {
 	a := make([]uint16, maxVers-minVers+1)
 	for i := range a {