362 lines
10 KiB
Go
362 lines
10 KiB
Go
package socks5
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import (
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"context"
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"fmt"
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"io"
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"net"
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"strings"
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"sync"
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)
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var (
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unrecognizedAddrType = fmt.Errorf("Unrecognized address type")
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)
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// AddressRewriter is used to rewrite a destination transparently
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type AddressRewriter interface {
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Rewrite(ctx context.Context, request *Request) (context.Context, *AddrSpec)
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}
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// A Request represents request received by a server
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type Request struct {
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Header
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// AuthContext provided during negotiation
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AuthContext *AuthContext
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// AddrSpec of the the network that sent the request
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RemoteAddr *AddrSpec
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// AddrSpec of the desired destination
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DestAddr *AddrSpec
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// AddrSpec of the actual destination (might be affected by rewrite)
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realDestAddr *AddrSpec
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bufConn io.Reader
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}
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type conn interface {
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Write([]byte) (int, error)
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RemoteAddr() net.Addr
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}
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// NewRequest creates a new Request from the tcp connection
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func NewRequest(bufConn io.Reader) (*Request, error) {
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/*
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The SOCKS request is formed as follows:
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+----+-----+-------+------+----------+----------+
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|VER | CMD | RSV | ATYP | DST.ADDR | DST.PORT |
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+----+-----+-------+------+----------+----------+
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| 1 | 1 | X'00' | 1 | Variable | 2 |
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+----+-----+-------+------+----------+----------+
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*/
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hd, err := Parse(bufConn)
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if err != nil {
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return nil, err
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}
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return &Request{
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Header: hd,
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DestAddr: &hd.Address,
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bufConn: bufConn,
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}, nil
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}
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// handleRequest is used for request processing after authentication
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func (s *Server) handleRequest(write io.Writer, req *Request) error {
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ctx := context.Background()
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// Resolve the address if we have a FQDN
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dest := req.DestAddr
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if dest.FQDN != "" {
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ctx_, addr, err := s.config.Resolver.Resolve(ctx, dest.FQDN)
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if err != nil {
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if err := sendReply(write, req.Header, hostUnreachable); err != nil {
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return fmt.Errorf("failed to send reply, %v", err)
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}
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return fmt.Errorf("failed to resolve destination[%v], %v", dest.FQDN, err)
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}
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ctx = ctx_
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dest.IP = addr
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}
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// Apply any address rewrites
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req.realDestAddr = req.DestAddr
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if s.config.Rewriter != nil {
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ctx, req.realDestAddr = s.config.Rewriter.Rewrite(ctx, req)
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}
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// Switch on the command
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switch req.Command {
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case ConnectCommand:
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return s.handleConnect(ctx, write, req)
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case BindCommand:
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return s.handleBind(ctx, write, req)
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case AssociateCommand:
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return s.handleAssociate(ctx, write, req)
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default:
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if err := sendReply(write, req.Header, commandNotSupported); err != nil {
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return fmt.Errorf("failed to send reply, %v", err)
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}
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return fmt.Errorf("unsupported command[%v]", req.Command)
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}
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}
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// handleConnect is used to handle a connect command
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func (s *Server) handleConnect(ctx context.Context, writer io.Writer, req *Request) error {
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// Check if this is allowed
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if ctx_, ok := s.config.Rules.Allow(ctx, req); !ok {
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if err := sendReply(writer, req.Header, ruleFailure); err != nil {
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return fmt.Errorf("failed to send reply, %v", err)
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}
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return fmt.Errorf("connect to %v blocked by rules", req.DestAddr)
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} else {
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ctx = ctx_
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}
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// Attempt to connect
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dial := s.config.Dial
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if dial == nil {
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dial = func(ctx context.Context, net_, addr string) (net.Conn, error) {
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return net.Dial(net_, addr)
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}
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}
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target, err := dial(ctx, "tcp", req.realDestAddr.Address())
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if err != nil {
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msg := err.Error()
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resp := hostUnreachable
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if strings.Contains(msg, "refused") {
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resp = connectionRefused
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} else if strings.Contains(msg, "network is unreachable") {
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resp = networkUnreachable
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}
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if err := sendReply(writer, req.Header, resp); err != nil {
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return fmt.Errorf("failed to send reply, %v", err)
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}
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return fmt.Errorf("connect to %v failed, %v", req.DestAddr, err)
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}
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defer target.Close()
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// Send success
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if err := sendReply(writer, req.Header, successReply, target.LocalAddr()); err != nil {
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return fmt.Errorf("failed to send reply, %v", err)
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}
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// Start proxying
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errCh := make(chan error, 2)
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s.submit(func() { errCh <- s.proxy(target, req.bufConn) })
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s.submit(func() { errCh <- s.proxy(writer, target) })
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// Wait
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for i := 0; i < 2; i++ {
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e := <-errCh
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if e != nil {
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// return from this function closes target (and conn).
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return e
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}
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}
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return nil
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}
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// handleBind is used to handle a connect command
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func (s *Server) handleBind(ctx context.Context, writer io.Writer, req *Request) error {
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// Check if this is allowed
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if ctx_, ok := s.config.Rules.Allow(ctx, req); !ok {
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if err := sendReply(writer, req.Header, ruleFailure); err != nil {
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return fmt.Errorf("failed to send reply, %v", err)
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}
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return fmt.Errorf("bind to %v blocked by rules", req.DestAddr)
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} else {
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ctx = ctx_
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}
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// TODO: Support bind
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if err := sendReply(writer, req.Header, commandNotSupported); err != nil {
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return fmt.Errorf("failed to send reply: %v", err)
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}
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return nil
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}
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// handleAssociate is used to handle a connect command
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func (s *Server) handleAssociate(ctx context.Context, writer io.Writer, req *Request) error {
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/*
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The SOCKS associate request/response is formed as follows:
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+-----+------+-------+----------+----------+----------+
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| RSV | FRAG | ATYP | DST.ADDR | DST.PORT | DATA |
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+-----+------+-------+----------+----------+----------+
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| 2 | 1 | X'00' | 1 | 2 | Variable |
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+-----+------+-------+----------+----------+----------+
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*/
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// Check if this is allowed
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if ctx_, ok := s.config.Rules.Allow(ctx, req); !ok {
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if err := sendReply(writer, req.Header, ruleFailure); err != nil {
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return fmt.Errorf("failed to send reply, %v", err)
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}
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return fmt.Errorf("associate to %v blocked by rules", req.DestAddr)
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} else {
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ctx = ctx_
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}
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// Attempt to connect
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dial := s.config.Dial
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if dial == nil {
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dial = func(ctx context.Context, net_, addr string) (net.Conn, error) {
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return net.Dial(net_, addr)
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}
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}
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target, err := dial(ctx, "udp", req.realDestAddr.Address())
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if err != nil {
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msg := err.Error()
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resp := hostUnreachable
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if strings.Contains(msg, "refused") {
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resp = connectionRefused
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} else if strings.Contains(msg, "network is unreachable") {
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resp = networkUnreachable
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}
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if err := sendReply(writer, req.Header, resp); err != nil {
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return fmt.Errorf("failed to send reply, %v", err)
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}
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return fmt.Errorf("connect to %v failed, %v", req.DestAddr, err)
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}
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defer target.Close()
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targetUdp, ok := target.(*net.UDPConn)
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if !ok {
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if err := sendReply(writer, req.Header, serverFailure); err != nil {
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return fmt.Errorf("failed to send reply, %v", err)
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}
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return fmt.Errorf("dial udp invalid")
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}
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lAddr, _ := net.ResolveUDPAddr("udp", ":0")
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bindLn, err := net.ListenUDP("udp4", lAddr)
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if err != nil {
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if err := sendReply(writer, req.Header, serverFailure); err != nil {
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return fmt.Errorf("failed to send reply, %v", err)
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}
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return fmt.Errorf("listen udp failed, %v", err)
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}
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s.config.Logger.Errorf("target addr %v, listen addr: %s", targetUdp.RemoteAddr(), bindLn.LocalAddr())
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// send BND.ADDR and BND.PORT, client must
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if err = sendReply(writer, req.Header, successReply, bindLn.LocalAddr()); err != nil {
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return fmt.Errorf("failed to send reply, %v", err)
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}
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s.submit(func() {
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// read from client and write to remote server
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conns := sync.Map{}
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buf := s.bufferPool.Get()
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defer s.bufferPool.Put(buf)
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for {
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n, srcAddr, err := bindLn.ReadFrom(buf[:cap(buf)])
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if err != nil {
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s.config.Logger.Errorf("read data from bind listen address %s failed, %v", bindLn.LocalAddr(), err)
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return
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}
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// 把消息写给remote sever
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if _, err := targetUdp.Write(buf[:n]); err != nil {
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s.config.Logger.Errorf("write data to remote %s failed, %v", targetUdp.RemoteAddr(), err)
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return
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}
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if _, ok := conns.LoadOrStore(srcAddr.String(), struct{}{}); !ok {
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s.submit(func() {
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// read from remote server and write to client
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buf := s.bufferPool.Get()
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defer s.bufferPool.Put(buf)
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for {
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n, _, err := targetUdp.ReadFrom(buf[:cap(buf)])
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if err != nil {
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s.config.Logger.Errorf("read data from remote %s failed, %v", targetUdp.RemoteAddr(), err)
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return
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}
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if _, err := bindLn.WriteTo(buf[:n], srcAddr); err != nil {
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s.config.Logger.Errorf("write data to client %s failed, %v", bindLn.LocalAddr(), err)
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return
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}
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}
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})
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}
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}
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})
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buf := s.bufferPool.Get()
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defer func() {
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s.bufferPool.Put(buf)
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}()
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for {
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_, err := req.bufConn.Read(buf)
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if err != nil {
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return err
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}
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}
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}
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// sendReply is used to send a reply message
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func sendReply(w io.Writer, head Header, resp uint8, bindAddr ...net.Addr) error {
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/*
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The SOCKS response is formed as follows:
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+----+-----+-------+------+----------+----------+
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|VER | CMD | RSV | ATYP | BND.ADDR | BND.PORT |
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+----+-----+-------+------+----------+----------+
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| 1 | 1 | X'00' | 1 | Variable | 2 |
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+----+-----+-------+------+----------+----------+
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*/
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head.Command = resp
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if len(bindAddr) == 0 {
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head.addrType = ipv4Address
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head.Address.IP = []byte{0, 0, 0, 0}
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head.Address.Port = 0
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} else {
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addrSpec := AddrSpec{}
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if tcpAddr, ok := bindAddr[0].(*net.TCPAddr); ok && tcpAddr != nil {
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addrSpec.IP = tcpAddr.IP
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addrSpec.Port = tcpAddr.Port
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} else if udpAddr, ok := bindAddr[0].(*net.UDPAddr); ok && udpAddr != nil {
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addrSpec.IP = udpAddr.IP
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addrSpec.Port = udpAddr.Port
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} else {
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addrSpec.IP = []byte{0, 0, 0, 0}
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addrSpec.Port = 0
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}
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switch {
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case addrSpec.FQDN != "":
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head.addrType = fqdnAddress
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head.Address.FQDN = addrSpec.FQDN
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head.Address.Port = addrSpec.Port
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case addrSpec.IP.To4() != nil:
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head.addrType = ipv4Address
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head.Address.IP = addrSpec.IP.To4()
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head.Address.Port = addrSpec.Port
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case addrSpec.IP.To16() != nil:
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head.addrType = ipv6Address
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head.Address.IP = addrSpec.IP.To16()
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head.Address.Port = addrSpec.Port
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default:
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return fmt.Errorf("failed to format address[%v]", bindAddr)
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}
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}
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// Send the message
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_, err := w.Write(head.Bytes())
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return err
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}
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type closeWriter interface {
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CloseWrite() error
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}
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// proxy is used to suffle data from src to destination, and sends errors
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// down a dedicated channel
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func (s *Server) proxy(dst io.Writer, src io.Reader) error {
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buf := s.bufferPool.Get()
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defer s.bufferPool.Put(buf)
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_, err := io.CopyBuffer(dst, src, buf[:cap(buf)])
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if tcpConn, ok := dst.(closeWriter); ok {
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tcpConn.CloseWrite()
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}
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return err
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}
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