Add post-handshake records detection (#17)

record_detect.go

@@ -0,0 +1,81 @@
+package reality
+
+import (
+	"bytes"
+	"crypto/tls"
+	"encoding/binary"
+	"io"
+	"net"
+	"time"
+)
+
+func DetectRecordFingerprint(target string) ([]int, error) {
+	NetConn, err := net.Dial("tcp", target)
+	if err != nil {
+		return nil, err
+	}
+	conn := &detectConn{
+		Conn:       NetConn,
+		resultChan: make(chan []int, 1),
+	}
+	host, _, err := net.SplitHostPort(target)
+	if err != nil {
+		return nil, err
+	}
+	tlsConfig := &tls.Config{
+		ServerName: host,
+	}
+	tlsConn := tls.Client(conn, tlsConfig)
+	err = tlsConn.Handshake()
+	if err != nil {
+		return nil, err
+	}
+	go func() {
+		io.Copy(io.Discard, tlsConn)
+	}()
+	select {
+	case result := <-conn.resultChan:
+		return result, nil
+	case <-time.After(2 * time.Second):
+		return nil, nil
+	}
+}
+
+type detectConn struct {
+	net.Conn
+	ccsSent    bool
+	done       bool
+	resultChan chan ([]int)
+}
+
+func (c *detectConn) Write(b []byte) (n int, err error) {
+	if len(b) >= 3 && bytes.Equal(b[:3], []byte{20, 3, 3}) {
+		c.ccsSent = true
+	}
+	return c.Conn.Write(b)
+}
+
+func (c *detectConn) Read(b []byte) (n int, err error) {
+	n, err = c.Conn.Read(b)
+	if c.ccsSent && !c.done {
+		data := make([]byte, len(b))
+		copy(data, b)
+		var result []int
+		for {
+			if len(data) > 3 && bytes.Equal(data[:3], []byte{23, 3, 3}) {
+				length := int(binary.BigEndian.Uint16(data[3:5]))
+				if len(data) > length+5 {
+					result = append(result, int(length))
+					data = data[length+5:]
+				}
+			} else {
+				break
+			}
+		}
+		if len(result) != 1 {
+			c.done = true
+			c.resultChan <- result
+		}
+	}
+	return n, err
+}