Add base dialers module

mtglib/dialers/shadowsocks.go

@@ -0,0 +1,68 @@
+package dialers
+
+import (
+	"context"
+	"encoding/base64"
+	"fmt"
+	"net"
+	"net/url"
+	"strings"
+	"time"
+
+	shadowsocks "github.com/shadowsocks/go-shadowsocks2/core"
+)
+
+type shadowsocksBaseDialer struct {
+	base   BaseDialer
+	cipher shadowsocks.StreamConnCipher
+}
+
+func (s *shadowsocksBaseDialer) Dial(network, address string) (net.Conn, error) {
+	conn, err := s.base.Dial(network, address)
+	if err != nil {
+		return nil, err
+	}
+
+	return s.cipher.StreamConn(conn), nil
+}
+
+func (s *shadowsocksBaseDialer) DialContext(ctx context.Context,
+	network, address string) (net.Conn, error) {
+	conn, err := s.base.DialContext(ctx, network, address)
+	if err != nil {
+		return nil, err
+	}
+
+	return s.cipher.StreamConn(conn), nil
+}
+
+func NewShadowsocksBaseDialer(proxyUrl *url.URL,
+	timeout time.Duration, bufferSize int) (BaseDialer, error) {
+	username := proxyUrl.User.Username()
+
+	decoded, err := base64.RawURLEncoding.DecodeString(username)
+	if err != nil {
+		return nil, fmt.Errorf("cannot decode payload: %w", err)
+	}
+
+	chunks := strings.SplitN(string(decoded), ":", 2)
+	if len(chunks) != 2 {
+		return nil, fmt.Errorf("incorrect payload %s", username)
+	}
+
+	cipher, err := shadowsocks.PickCipher(chunks[0], nil, chunks[1])
+	if err != nil {
+		return nil, fmt.Errorf("cannot initialize shadowsocks cipher: %w", err)
+	}
+
+	baseDialer, err := NewDefaultBaseDialer(timeout, bufferSize)
+	if err != nil {
+		return nil, fmt.Errorf("cannot initialize a base dialer: %w", err)
+
+	}
+
+	return &shadowsocksBaseDialer{
+		base:   baseDialer,
+		cipher: cipher,
+	}, nil
+}