/
handler.go
261 lines (216 loc) · 5.89 KB
/
handler.go
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package ssh
import (
"context"
"encoding/binary"
"errors"
"fmt"
"net"
"strconv"
"time"
"github.com/go-gost/core/chain"
"github.com/go-gost/core/handler"
"github.com/go-gost/core/logger"
md "github.com/go-gost/core/metadata"
netpkg "github.com/wznpp1/gost_x/internal/net"
sshd_util "github.com/wznpp1/gost_x/internal/util/sshd"
"github.com/wznpp1/gost_x/registry"
"golang.org/x/crypto/ssh"
)
// Applicable SSH Request types for Port Forwarding - RFC 4254 7.X
const (
ForwardedTCPReturnRequest = "forwarded-tcpip" // RFC 4254 7.2
)
func init() {
registry.HandlerRegistry().Register("sshd", NewHandler)
}
type forwardHandler struct {
router *chain.Router
md metadata
options handler.Options
}
func NewHandler(opts ...handler.Option) handler.Handler {
options := handler.Options{}
for _, opt := range opts {
opt(&options)
}
return &forwardHandler{
options: options,
}
}
func (h *forwardHandler) Init(md md.Metadata) (err error) {
if err = h.parseMetadata(md); err != nil {
return
}
h.router = h.options.Router
if h.router == nil {
h.router = chain.NewRouter(chain.LoggerRouterOption(h.options.Logger))
}
return nil
}
func (h *forwardHandler) Handle(ctx context.Context, conn net.Conn, opts ...handler.HandleOption) error {
defer conn.Close()
log := h.options.Logger.WithFields(map[string]any{
"remote": conn.RemoteAddr().String(),
"local": conn.LocalAddr().String(),
})
if !h.checkRateLimit(conn.RemoteAddr()) {
return nil
}
switch cc := conn.(type) {
case *sshd_util.DirectForwardConn:
return h.handleDirectForward(ctx, cc, log)
case *sshd_util.RemoteForwardConn:
return h.handleRemoteForward(ctx, cc, log)
default:
err := errors.New("sshd: wrong connection type")
log.Error(err)
return err
}
}
func (h *forwardHandler) handleDirectForward(ctx context.Context, conn *sshd_util.DirectForwardConn, log logger.Logger) error {
targetAddr := conn.DstAddr()
log = log.WithFields(map[string]any{
"dst": fmt.Sprintf("%s/%s", targetAddr, "tcp"),
"cmd": "connect",
})
log.Debugf("%s >> %s", conn.RemoteAddr(), targetAddr)
if h.options.Bypass != nil && h.options.Bypass.Contains(targetAddr) {
log.Debugf("bypass %s", targetAddr)
return nil
}
cc, err := h.router.Dial(ctx, "tcp", targetAddr)
if err != nil {
return err
}
defer cc.Close()
t := time.Now()
log.Debugf("%s <-> %s", cc.LocalAddr(), targetAddr)
netpkg.Transport(conn, cc)
log.WithFields(map[string]any{
"duration": time.Since(t),
}).Debugf("%s >-< %s", cc.LocalAddr(), targetAddr)
return nil
}
func (h *forwardHandler) handleRemoteForward(ctx context.Context, conn *sshd_util.RemoteForwardConn, log logger.Logger) error {
req := conn.Request()
t := tcpipForward{}
if err := ssh.Unmarshal(req.Payload, &t); err != nil {
log.Error(err)
return err
}
network := "tcp"
addr := net.JoinHostPort(t.Host, strconv.Itoa(int(t.Port)))
log = log.WithFields(map[string]any{
"dst": fmt.Sprintf("%s/%s", addr, network),
"cmd": "bind",
})
log.Debugf("%s >> %s", conn.RemoteAddr(), addr)
// tie to the client connection
ln, err := net.Listen(network, addr)
if err != nil {
log.Error(err)
req.Reply(false, nil)
return err
}
defer ln.Close()
log = log.WithFields(map[string]any{
"bind": fmt.Sprintf("%s/%s", ln.Addr(), ln.Addr().Network()),
})
log.Debugf("bind on %s OK", ln.Addr())
err = func() error {
if t.Port == 0 && req.WantReply { // Client sent port 0. let them know which port is actually being used
_, port, err := getHostPortFromAddr(ln.Addr())
if err != nil {
return err
}
var b [4]byte
binary.BigEndian.PutUint32(b[:], uint32(port))
t.Port = uint32(port)
return req.Reply(true, b[:])
}
return req.Reply(true, nil)
}()
if err != nil {
log.Error(err)
return err
}
sshConn := conn.Conn()
go func() {
for {
cc, err := ln.Accept()
if err != nil { // Unable to accept new connection - listener is likely closed
return
}
go func(conn net.Conn) {
defer conn.Close()
log := log.WithFields(map[string]any{
"local": conn.LocalAddr().String(),
"remote": conn.RemoteAddr().String(),
})
p := directForward{}
var err error
var portnum int
p.Host1 = t.Host
p.Port1 = t.Port
p.Host2, portnum, err = getHostPortFromAddr(conn.RemoteAddr())
if err != nil {
return
}
p.Port2 = uint32(portnum)
ch, reqs, err := sshConn.OpenChannel(ForwardedTCPReturnRequest, ssh.Marshal(p))
if err != nil {
log.Error("open forwarded channel: ", err)
return
}
defer ch.Close()
go ssh.DiscardRequests(reqs)
t := time.Now()
log.Debugf("%s <-> %s", conn.LocalAddr(), conn.RemoteAddr())
netpkg.Transport(ch, conn)
log.WithFields(map[string]any{
"duration": time.Since(t),
}).Debugf("%s >-< %s", conn.LocalAddr(), conn.RemoteAddr())
}(cc)
}
}()
tm := time.Now()
log.Debugf("%s <-> %s", conn.RemoteAddr(), addr)
<-conn.Done()
log.WithFields(map[string]any{
"duration": time.Since(tm),
}).Debugf("%s >-< %s", conn.RemoteAddr(), addr)
return nil
}
func (h *forwardHandler) checkRateLimit(addr net.Addr) bool {
if h.options.RateLimiter == nil {
return true
}
host, _, _ := net.SplitHostPort(addr.String())
if limiter := h.options.RateLimiter.Limiter(host); limiter != nil {
return limiter.Allow(1)
}
return true
}
func getHostPortFromAddr(addr net.Addr) (host string, port int, err error) {
host, portString, err := net.SplitHostPort(addr.String())
if err != nil {
return
}
port, err = strconv.Atoi(portString)
return
}
// directForward is structure for RFC 4254 7.2 - can be used for "forwarded-tcpip" and "direct-tcpip"
type directForward struct {
Host1 string
Port1 uint32
Host2 string
Port2 uint32
}
func (p directForward) String() string {
return fmt.Sprintf("%s:%d -> %s:%d", p.Host2, p.Port2, p.Host1, p.Port1)
}
// tcpipForward is structure for RFC 4254 7.1 "tcpip-forward" request
type tcpipForward struct {
Host string
Port uint32
}