295 lines
7.0 KiB
Go
295 lines
7.0 KiB
Go
package ssh
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import (
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"context"
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"encoding/binary"
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"fmt"
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"net"
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"strconv"
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"time"
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"github.com/go-gost/gost/pkg/auth"
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"github.com/go-gost/gost/pkg/bypass"
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"github.com/go-gost/gost/pkg/chain"
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"github.com/go-gost/gost/pkg/handler"
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ssh_util "github.com/go-gost/gost/pkg/internal/util/ssh"
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"github.com/go-gost/gost/pkg/logger"
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md "github.com/go-gost/gost/pkg/metadata"
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"github.com/go-gost/gost/pkg/registry"
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"golang.org/x/crypto/ssh"
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)
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// Applicable SSH Request types for Port Forwarding - RFC 4254 7.X
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const (
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DirectForwardRequest = "direct-tcpip" // RFC 4254 7.2
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RemoteForwardRequest = "tcpip-forward" // RFC 4254 7.1
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ForwardedTCPReturnRequest = "forwarded-tcpip" // RFC 4254 7.2
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CancelRemoteForwardRequest = "cancel-tcpip-forward" // RFC 4254 7.1
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)
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func init() {
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registry.RegisterHandler("sshd", NewHandler)
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}
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type forwardHandler struct {
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bypass bypass.Bypass
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config *ssh.ServerConfig
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router *chain.Router
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authenticator auth.Authenticator
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logger logger.Logger
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md metadata
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}
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func NewHandler(opts ...handler.Option) handler.Handler {
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options := &handler.Options{}
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for _, opt := range opts {
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opt(options)
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}
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return &forwardHandler{
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bypass: options.Bypass,
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router: options.Router,
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logger: options.Logger,
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}
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}
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func (h *forwardHandler) Init(md md.Metadata) (err error) {
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if err = h.parseMetadata(md); err != nil {
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return
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}
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config := &ssh.ServerConfig{
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PasswordCallback: ssh_util.PasswordCallback(h.authenticator),
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PublicKeyCallback: ssh_util.PublicKeyCallback(h.md.authorizedKeys),
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}
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config.AddHostKey(h.md.signer)
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if h.authenticator == nil && len(h.md.authorizedKeys) == 0 {
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config.NoClientAuth = true
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}
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h.config = config
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return nil
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}
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func (h *forwardHandler) Handle(ctx context.Context, conn net.Conn) {
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defer conn.Close()
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start := time.Now()
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h.logger = h.logger.WithFields(map[string]interface{}{
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"remote": conn.RemoteAddr().String(),
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"local": conn.LocalAddr().String(),
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})
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h.logger.Infof("%s <> %s", conn.RemoteAddr(), conn.LocalAddr())
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defer func() {
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h.logger.WithFields(map[string]interface{}{
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"duration": time.Since(start),
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}).Infof("%s >< %s", conn.RemoteAddr(), conn.LocalAddr())
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}()
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sshConn, chans, reqs, err := ssh.NewServerConn(conn, h.config)
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if err != nil {
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h.logger.Error(err)
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return
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}
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h.handleForward(ctx, sshConn, chans, reqs)
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}
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func (h *forwardHandler) handleForward(ctx context.Context, conn ssh.Conn, chans <-chan ssh.NewChannel, reqs <-chan *ssh.Request) {
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quit := make(chan struct{})
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defer close(quit) // quit signal
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go func() {
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for req := range reqs {
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switch req.Type {
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case RemoteForwardRequest:
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go h.tcpipForwardRequest(conn, req, quit)
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default:
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h.logger.Warnf("unsupported request type: %s, want reply: %v", req.Type, req.WantReply)
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if req.WantReply {
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req.Reply(false, nil)
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}
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}
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}
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}()
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go func() {
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for newChannel := range chans {
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// Check the type of channel
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t := newChannel.ChannelType()
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switch t {
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case DirectForwardRequest:
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channel, requests, err := newChannel.Accept()
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if err != nil {
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h.logger.Warnf("could not accept channel: %s", err.Error())
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continue
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}
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p := directForward{}
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ssh.Unmarshal(newChannel.ExtraData(), &p)
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h.logger.Debug(p.String())
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if p.Host1 == "<nil>" {
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p.Host1 = ""
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}
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go ssh.DiscardRequests(requests)
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go h.directPortForwardChannel(ctx, channel, net.JoinHostPort(p.Host1, strconv.Itoa(int(p.Port1))))
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default:
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h.logger.Warnf("unsupported channel type: %s", t)
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newChannel.Reject(ssh.Prohibited, fmt.Sprintf("unsupported channel type: %s", t))
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}
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}
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}()
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conn.Wait()
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}
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func (h *forwardHandler) directPortForwardChannel(ctx context.Context, channel ssh.Channel, raddr string) {
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defer channel.Close()
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// log.Logf("[ssh-tcp] %s - %s", h.options.Node.Addr, raddr)
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/*
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if !Can("tcp", raddr, h.options.Whitelist, h.options.Blacklist) {
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log.Logf("[ssh-tcp] Unauthorized to tcp connect to %s", raddr)
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return
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}
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*/
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if h.bypass != nil && h.bypass.Contains(raddr) {
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h.logger.Infof("bypass %s", raddr)
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return
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}
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conn, err := h.router.Dial(ctx, "tcp", raddr)
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if err != nil {
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return
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}
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defer conn.Close()
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t := time.Now()
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h.logger.Infof("%s <-> %s", conn.LocalAddr(), conn.RemoteAddr())
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handler.Transport(conn, channel)
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h.logger.WithFields(map[string]interface{}{
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"duration": time.Since(t),
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}).Infof("%s >-< %s", conn.LocalAddr(), conn.RemoteAddr())
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}
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// directForward is structure for RFC 4254 7.2 - can be used for "forwarded-tcpip" and "direct-tcpip"
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type directForward struct {
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Host1 string
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Port1 uint32
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Host2 string
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Port2 uint32
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}
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func (p directForward) String() string {
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return fmt.Sprintf("%s:%d -> %s:%d", p.Host2, p.Port2, p.Host1, p.Port1)
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}
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func getHostPortFromAddr(addr net.Addr) (host string, port int, err error) {
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host, portString, err := net.SplitHostPort(addr.String())
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if err != nil {
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return
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}
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port, err = strconv.Atoi(portString)
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return
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}
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// tcpipForward is structure for RFC 4254 7.1 "tcpip-forward" request
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type tcpipForward struct {
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Host string
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Port uint32
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}
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func (h *forwardHandler) tcpipForwardRequest(sshConn ssh.Conn, req *ssh.Request, quit <-chan struct{}) {
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t := tcpipForward{}
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ssh.Unmarshal(req.Payload, &t)
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addr := net.JoinHostPort(t.Host, strconv.Itoa(int(t.Port)))
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/*
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if !Can("rtcp", addr, h.options.Whitelist, h.options.Blacklist) {
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log.Logf("[ssh-rtcp] Unauthorized to tcp bind to %s", addr)
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req.Reply(false, nil)
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return
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}
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*/
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// tie to the client connection
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ln, err := net.Listen("tcp", addr)
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if err != nil {
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h.logger.Error(err)
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req.Reply(false, nil)
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return
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}
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defer ln.Close()
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h.logger.Debugf("bind on %s OK", ln.Addr())
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err = func() error {
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if t.Port == 0 && req.WantReply { // Client sent port 0. let them know which port is actually being used
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_, port, err := getHostPortFromAddr(ln.Addr())
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if err != nil {
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return err
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}
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var b [4]byte
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binary.BigEndian.PutUint32(b[:], uint32(port))
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t.Port = uint32(port)
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return req.Reply(true, b[:])
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}
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return req.Reply(true, nil)
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}()
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if err != nil {
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h.logger.Error(err)
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return
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}
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go func() {
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for {
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conn, err := ln.Accept()
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if err != nil { // Unable to accept new connection - listener is likely closed
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return
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}
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go func(conn net.Conn) {
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defer conn.Close()
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p := directForward{}
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var err error
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var portnum int
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p.Host1 = t.Host
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p.Port1 = t.Port
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p.Host2, portnum, err = getHostPortFromAddr(conn.RemoteAddr())
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if err != nil {
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return
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}
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p.Port2 = uint32(portnum)
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ch, reqs, err := sshConn.OpenChannel(ForwardedTCPReturnRequest, ssh.Marshal(p))
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if err != nil {
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h.logger.Error("open forwarded channel: ", err)
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return
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}
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defer ch.Close()
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go ssh.DiscardRequests(reqs)
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t := time.Now()
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h.logger.Infof("%s <-> %s", conn.RemoteAddr(), conn.LocalAddr())
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handler.Transport(ch, conn)
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h.logger.WithFields(map[string]interface{}{
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"duration": time.Since(t),
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}).Infof("%s >-< %s", conn.RemoteAddr(), conn.LocalAddr())
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}(conn)
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}
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}()
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<-quit
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}
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