proxy/server/fwd/socks/server.go

package socks

import (
	"bufio"
	"context"
	"fmt"
	"io"
	"log"
	"log/slog"
	"net"
	"os"
	"proxy-server/pkg/utils"
	"strconv"
	"time"

	"github.com/pkg/errors"
)

const (
	Version = byte(5)
)

type Config struct {
	Name string

	Host string
	Port uint16

	// 认证方法
	AuthMethods []Authenticator

	// 域名解析
	Resolver NameResolver

	// 自定义认证规则
	Rules RuleSet

	// 地址重写
	Rewriter AddressRewriter

	// 用于 bind 和 associate
	BindIP net.IP

	// Logger
	Logger *log.Logger

	// 自定义连接流程
	Dial func(network, addr string) (net.Conn, error)
}

type Server struct {
	config *Config
	ctx    context.Context
	cancel context.CancelFunc
	wg     utils.CountWaitGroup
	Name   string
	Port   uint16
	Conn   chan ProxyData
}

// New 创建服务器
func New(conf *Config) (*Server, error) {
	if len(conf.AuthMethods) == 0 {
		return nil, ConfigError("认证方法不能为空")
	}

	if conf.Resolver == nil {
		conf.Resolver = DNSResolver{}
	}

	if conf.Rules == nil {
		conf.Rules = PermitAll()
	}

	if conf.Logger == nil {
		conf.Logger = log.New(os.Stdout, "", log.LstdFlags)
	}

	if conf.Dial == nil {
		conf.Dial = func(network, addr string) (net.Conn, error) {
			return net.Dial(network, addr)
		}
	}

	ctx, cancel := context.WithCancel(context.Background())
	return &Server{
		config: conf,
		ctx:    ctx,
		cancel: cancel,
		wg:     utils.CountWaitGroup{},
		Name:   conf.Name,
		Port:   conf.Port,
		Conn:   make(chan ProxyData, 100),
	}, nil
}

// Run 监听端口
func (s *Server) Run() error {
	slog.Info("启动 socks5 代理服务")

	// 监听端口
	host := s.config.Host
	port := s.config.Port
	addr := net.JoinHostPort(host, strconv.Itoa(int(port)))
	ls, err := net.Listen("tcp", addr)
	if err != nil {
		return errors.Wrap(err, "监听端口失败")
	}
	defer utils.Close(ls)
	slog.Info("正在监听端口", slog.Uint64("port", uint64(port)))

	// 处理连接
	connCh := utils.ChanConnAccept(s.ctx, ls)
	defer close(connCh)

	err = nil
	for loop := true; loop; {
		select {
		case <-s.ctx.Done():
			slog.Debug("服务主动停止")
			loop = false
		case conn, ok := <-connCh:
			if !ok {
				err = errors.New("意外错误，无法获取连接")
				loop = false
				break
			}
			s.wg.Add(1)
			go func() {
				defer s.wg.Done()
				err := s.serve(conn)
				if err != nil {
					slog.Error("处理连接失败", err)
				}
			}()
		}
	}
	if err != nil {
		s.Close()
	}

	// 关闭服务
	timeout, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()
	wgCh := utils.ChanWgWait(timeout, &s.wg)

	err = nil
	select {
	case <-timeout.Done():
		err = errors.New("关闭超时（强制关闭）")
	case <-wgCh:
	}

	if s.Conn != nil {
		close(s.Conn)
	}

	return err
}

// Close 关闭服务
func (s *Server) Close() {
	s.cancel()
}

// serve 建立连接
func (s *Server) serve(conn net.Conn) error {
	slog.Info("收到来自" + conn.RemoteAddr().String() + "的连接")

	reader := bufio.NewReader(conn)

	// 认证
	slog.Debug("开始认证流程")
	authContext, err := s.authenticate(reader, conn)
	if err != nil {
		utils.Close(conn)
		slog.Error("认证失败", err)
		return err
	} else {
		slog.Debug("认证完成")
	}

	// 处理连接请求
	slog.Debug("处理连接请求")
	request, err := s.request(reader, conn)
	if err != nil {
		slog.Error("连接请求处理失败", err)
		return err
	} else {
		slog.Debug("连接请求处理完成")
	}

	request.AuthContext = authContext
	client, ok := conn.RemoteAddr().(*net.TCPAddr)
	if !ok {
		return fmt.Errorf("获取客户端地址失败")
	}

	request.RemoteAddr = &AddrSpec{
		IP:   client.IP,
		Port: client.Port,
	}

	// 处理请求
	slog.Debug("开始代理流量")
	err = s.handle(request, conn)
	if err != nil {
		return err
	}

	return nil
}

// checkVersion 检查客户端版本
func checkVersion(reader io.Reader) error {
	version, err := utils.ReadByte(reader)
	if err != nil {
		return err
	}

	slog.Debug("客户端请求版本", "version", version)

	if version != Version {
		return errors.New("客户端版本不兼容")
	}

	return nil
}