initial commit

connector/sni/conn.go

@@ -0,0 +1,128 @@
+package sni
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/base64"
+	"encoding/binary"
+	"hash/crc32"
+	"io"
+	"net"
+	"strings"
+
+	dissector "github.com/go-gost/tls-dissector"
+)
+
+type sniClientConn struct {
+	host       string
+	obfuscated bool
+	net.Conn
+}
+
+func (c *sniClientConn) Write(p []byte) (int, error) {
+	b, err := c.obfuscate(p)
+	if err != nil {
+		return 0, err
+	}
+	if _, err = c.Conn.Write(b); err != nil {
+		return 0, err
+	}
+	return len(p), nil
+}
+
+func (c *sniClientConn) obfuscate(p []byte) ([]byte, error) {
+	if c.host == "" {
+		return p, nil
+	}
+
+	if c.obfuscated {
+		return p, nil
+	}
+
+	if p[0] == dissector.Handshake {
+		b, err := readClientHelloRecord(bytes.NewReader(p), c.host)
+		if err != nil {
+			return nil, err
+		}
+		c.obfuscated = true
+		return b, nil
+	}
+
+	buf := &bytes.Buffer{}
+	br := bufio.NewReader(bytes.NewReader(p))
+	for {
+		s, err := br.ReadString('\n')
+		if err != nil {
+			if err != io.EOF {
+				return nil, err
+			}
+			if s != "" {
+				buf.Write([]byte(s))
+			}
+			break
+		}
+
+		// end of HTTP header
+		if s == "\r\n" {
+			buf.Write([]byte(s))
+			// drain the remain bytes.
+			io.Copy(buf, br)
+			break
+		}
+
+		if strings.HasPrefix(s, "Host") {
+			s = strings.TrimSpace(strings.TrimSuffix(strings.TrimPrefix(s, "Host:"), "\r\n"))
+			host := encodeServerName(s)
+			buf.WriteString("Host: " + c.host + "\r\n")
+			buf.WriteString("Gost-Target: " + host + "\r\n")
+			// drain the remain bytes.
+			io.Copy(buf, br)
+			break
+		}
+		buf.Write([]byte(s))
+	}
+	c.obfuscated = true
+	return buf.Bytes(), nil
+}
+
+func readClientHelloRecord(r io.Reader, host string) ([]byte, error) {
+	record, err := dissector.ReadRecord(r)
+	if err != nil {
+		return nil, err
+	}
+	clientHello := dissector.ClientHelloMsg{}
+	if err := clientHello.Decode(record.Opaque); err != nil {
+		return nil, err
+	}
+
+	for _, ext := range clientHello.Extensions {
+		if ext.Type() == dissector.ExtServerName {
+			snExtension := ext.(*dissector.ServerNameExtension)
+			if host != "" {
+				e, _ := dissector.NewExtension(0xFFFE, []byte(encodeServerName(snExtension.Name)))
+				clientHello.Extensions = append(clientHello.Extensions, e)
+				snExtension.Name = host
+			}
+
+			break
+		}
+	}
+	record.Opaque, err = clientHello.Encode()
+	if err != nil {
+		return nil, err
+	}
+
+	buf := &bytes.Buffer{}
+	if _, err := record.WriteTo(buf); err != nil {
+		return nil, err
+	}
+
+	return buf.Bytes(), nil
+}
+
+func encodeServerName(name string) string {
+	buf := &bytes.Buffer{}
+	binary.Write(buf, binary.BigEndian, crc32.ChecksumIEEE([]byte(name)))
+	buf.WriteString(base64.RawURLEncoding.EncodeToString([]byte(name)))
+	return base64.RawURLEncoding.EncodeToString(buf.Bytes())
+}