493 lines
10 KiB
Go
493 lines
10 KiB
Go
package tun2
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import (
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"bytes"
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"context"
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"crypto/tls"
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"encoding/json"
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"errors"
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"fmt"
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"io/ioutil"
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"math/rand"
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"net"
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"net/http"
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"os"
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"sync"
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"time"
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"github.com/Xe/ln"
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failure "github.com/dgryski/go-failure"
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"github.com/mtneug/pkg/ulid"
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cmap "github.com/streamrail/concurrent-map"
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kcp "github.com/xtaci/kcp-go"
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"github.com/xtaci/smux"
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)
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// Error values
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var (
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ErrNoSuchBackend = errors.New("tun2: there is no such backend")
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ErrAuthMismatch = errors.New("tun2: authenication doesn't match database records")
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ErrCantRemoveWhatDoesntExist = errors.New("tun2: this connection does not exist, cannot remove it")
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)
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// gen502Page creates the page that is shown when a backend is not connected to a given route.
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func gen502Page(req *http.Request) *http.Response {
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template := `<html><head><title>no backends connected</title></head><body><h1>no backends connected</h1><p>Please ensure a backend is running for ${HOST}. This is request ID ${REQ_ID}.</p></body></html>`
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resbody := []byte(os.Expand(template, func(in string) string {
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switch in {
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case "HOST":
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return req.Host
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case "REQ_ID":
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return req.Header.Get("X-Request-Id")
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}
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return "<unknown>"
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}))
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reshdr := req.Header
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reshdr.Set("Content-Type", "text/html; charset=utf-8")
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resp := &http.Response{
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Status: fmt.Sprintf("%d Bad Gateway", http.StatusBadGateway),
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StatusCode: http.StatusBadGateway,
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Body: ioutil.NopCloser(bytes.NewBuffer(resbody)),
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Proto: req.Proto,
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ProtoMajor: req.ProtoMajor,
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ProtoMinor: req.ProtoMinor,
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Header: reshdr,
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ContentLength: int64(len(resbody)),
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Close: true,
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Request: req,
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}
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return resp
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}
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// ServerConfig ...
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type ServerConfig struct {
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TCPAddr string
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KCPAddr string
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TLSConfig *tls.Config
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SmuxConf *smux.Config
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Storage Storage
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}
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// Storage is the minimal subset of features that tun2's Server needs out of a
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// persistence layer.
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type Storage interface {
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HasToken(token string) (user string, scopes []string, err error)
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HasRoute(domain string) (user string, err error)
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}
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// Server routes frontend HTTP traffic to backend TCP traffic.
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type Server struct {
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cfg *ServerConfig
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connlock sync.Mutex
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conns map[net.Conn]*Connection
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domains cmap.ConcurrentMap
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}
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// NewServer creates a new Server instance with a given config, acquiring all
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// relevant resources.
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func NewServer(cfg *ServerConfig) (*Server, error) {
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if cfg == nil {
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return nil, errors.New("tun2: config must be specified")
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}
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if cfg.SmuxConf == nil {
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cfg.SmuxConf = smux.DefaultConfig()
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}
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cfg.SmuxConf.KeepAliveInterval = time.Second
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cfg.SmuxConf.KeepAliveTimeout = 15 * time.Second
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server := &Server{
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cfg: cfg,
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conns: map[net.Conn]*Connection{},
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domains: cmap.New(),
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}
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return server, nil
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}
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// Listen passes this Server a given net.Listener to accept backend connections.
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func (s *Server) Listen(l net.Listener, isKCP bool) {
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ctx := context.Background()
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for {
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conn, err := l.Accept()
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if err != nil {
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ln.Error(ctx, err, ln.F{
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"addr": l.Addr().String(),
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"network": l.Addr().Network(),
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})
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continue
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}
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ln.Log(ctx, ln.F{
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"action": "new_client",
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"network": conn.RemoteAddr().Network(),
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"addr": conn.RemoteAddr(),
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"list": conn.LocalAddr(),
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})
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go s.HandleConn(conn, isKCP)
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}
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}
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// ListenAndServe starts the backend TCP/KCP listeners and relays backend
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// traffic to and from them.
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func (s *Server) ListenAndServe() error {
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel()
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ln.Log(ctx, ln.F{
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"action": "listen_and_serve_called",
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})
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if s.cfg.TCPAddr != "" {
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go func() {
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l, err := tls.Listen("tcp", s.cfg.TCPAddr, s.cfg.TLSConfig)
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if err != nil {
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panic(err)
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}
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ln.Log(ctx, ln.F{
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"action": "tcp+tls_listening",
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"addr": l.Addr(),
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})
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for {
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conn, err := l.Accept()
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if err != nil {
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ln.Error(ctx, err, ln.F{"kind": "tcp", "addr": l.Addr().String()})
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continue
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}
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ln.Log(ctx, ln.F{
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"action": "new_client",
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"kcp": false,
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"addr": conn.RemoteAddr(),
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})
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go s.HandleConn(conn, false)
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}
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}()
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}
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if s.cfg.KCPAddr != "" {
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go func() {
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l, err := kcp.Listen(s.cfg.KCPAddr)
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if err != nil {
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panic(err)
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}
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ln.Log(ctx, ln.F{
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"action": "kcp+tls_listening",
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"addr": l.Addr(),
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})
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for {
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conn, err := l.Accept()
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if err != nil {
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ln.Error(ctx, err, ln.F{"kind": "kcp", "addr": l.Addr().String()})
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}
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ln.Log(ctx, ln.F{
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"action": "new_client",
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"kcp": true,
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"addr": conn.RemoteAddr(),
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})
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tc := tls.Server(conn, s.cfg.TLSConfig)
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go s.HandleConn(tc, true)
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}
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}()
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}
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// XXX experimental, might get rid of this inside this process
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go func() {
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for {
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time.Sleep(time.Second)
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now := time.Now()
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s.connlock.Lock()
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for _, c := range s.conns {
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failureChance := c.detector.Phi(now)
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if failureChance > 0.8 {
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ln.Log(ctx, c.F(), ln.F{
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"action": "phi_failure_detection",
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"value": failureChance,
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})
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}
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}
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s.connlock.Unlock()
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}
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}()
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return nil
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}
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// HandleConn starts up the needed mechanisms to relay HTTP traffic to/from
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// the currently connected backend.
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func (s *Server) HandleConn(c net.Conn, isKCP bool) {
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// XXX TODO clean this up it's really ugly.
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defer c.Close()
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel()
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f := ln.F{
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"local": c.LocalAddr().String(),
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"remote": c.RemoteAddr().String(),
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}
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session, err := smux.Server(c, s.cfg.SmuxConf)
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if err != nil {
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ln.Error(ctx, err, f, ln.Action("establish server side of smux"))
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return
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}
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defer session.Close()
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f["stage"] = "smux_setup"
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controlStream, err := session.OpenStream()
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if err != nil {
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ln.Error(ctx, err, f, ln.Action("opening control stream"))
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return
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}
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defer controlStream.Close()
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f["stage"] = "control_stream_open"
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csd := json.NewDecoder(controlStream)
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auth := &Auth{}
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err = csd.Decode(auth)
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if err != nil {
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ln.Error(ctx, err, f, ln.Action("decode control stream authenication message"))
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return
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}
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f["stage"] = "checking_domain"
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routeUser, err := s.cfg.Storage.HasRoute(auth.Domain)
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if err != nil {
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ln.Error(ctx, err, f, ln.Action("no such domain when checking client auth"))
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return
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}
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f["route_user"] = routeUser
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f["stage"] = "checking_token"
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tokenUser, scopes, err := s.cfg.Storage.HasToken(auth.Token)
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if err != nil {
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ln.Error(ctx, err, f, ln.Action("no such token exists or other token error"))
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return
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}
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f["token_user"] = tokenUser
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f["stage"] = "checking_token_scopes"
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ok := false
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for _, sc := range scopes {
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if sc == "connect" {
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ok = true
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break
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}
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}
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if !ok {
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ln.Error(ctx, ErrAuthMismatch, f, ln.Action("token not authorized to connect"))
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return
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}
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f["stage"] = "user_verification"
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if routeUser != tokenUser {
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ln.Error(ctx, ErrAuthMismatch, f, ln.Action("auth mismatch"))
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return
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}
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connection := &Connection{
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id: ulid.New().String(),
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conn: c,
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isKCP: isKCP,
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session: session,
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user: tokenUser,
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domain: auth.Domain,
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cf: cancel,
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detector: failure.New(15, 1),
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Auth: auth,
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}
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defer func() {
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if r := recover(); r != nil {
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ln.Log(ctx, connection, ln.F{"action": "connection handler panic", "err": r})
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}
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}()
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ln.Log(ctx, connection, ln.Action("backend successfully connected"))
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// TODO: put these lines in a function?
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s.connlock.Lock()
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s.conns[c] = connection
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s.connlock.Unlock()
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var conns []*Connection
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val, ok := s.domains.Get(auth.Domain)
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if ok {
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conns, ok = val.([]*Connection)
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if !ok {
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conns = nil
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s.domains.Remove(auth.Domain)
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}
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}
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conns = append(conns, connection)
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s.domains.Set(auth.Domain, conns)
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connection.usable = true // XXX set this to true once health checks pass?
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ticker := time.NewTicker(5 * time.Second)
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defer ticker.Stop()
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for {
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select {
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case <-ticker.C:
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err := connection.Ping()
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if err != nil {
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connection.cancel()
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}
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case <-ctx.Done():
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s.RemoveConn(ctx, connection)
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connection.Close()
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return
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}
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}
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}
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// RemoveConn removes a connection.
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func (s *Server) RemoveConn(ctx context.Context, connection *Connection) {
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s.connlock.Lock()
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delete(s.conns, connection.conn)
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s.connlock.Unlock()
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auth := connection.Auth
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var conns []*Connection
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val, ok := s.domains.Get(auth.Domain)
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if ok {
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conns, ok = val.([]*Connection)
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if !ok {
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ln.Error(ctx, ErrCantRemoveWhatDoesntExist, connection, ln.Action("looking up for disconnect removal"))
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return
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}
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}
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for i, cntn := range conns {
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if cntn.id == connection.id {
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conns[i] = conns[len(conns)-1]
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conns = conns[:len(conns)-1]
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}
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}
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if len(conns) != 0 {
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s.domains.Set(auth.Domain, conns)
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} else {
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s.domains.Remove(auth.Domain)
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}
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ln.Log(ctx, connection, ln.Action("backend disconnect"))
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}
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// RoundTrip sends a HTTP request to a backend and then returns its response.
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func (s *Server) RoundTrip(req *http.Request) (*http.Response, error) {
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var conns []*Connection
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ctx := req.Context()
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val, ok := s.domains.Get(req.Host)
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if ok {
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conns, ok = val.([]*Connection)
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if !ok {
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ln.Error(ctx, ErrNoSuchBackend, ln.F{
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"action": "no_backend_connected",
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"remote": req.RemoteAddr,
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"host": req.Host,
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"uri": req.RequestURI,
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})
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return gen502Page(req), nil
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}
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}
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var goodConns []*Connection
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for _, conn := range conns {
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if conn.usable {
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goodConns = append(goodConns, conn)
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}
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}
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if len(goodConns) == 0 {
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ln.Error(ctx, ErrNoSuchBackend, ln.F{
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"action": "no_backend_connected",
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"remote": req.RemoteAddr,
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"host": req.Host,
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"uri": req.RequestURI,
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})
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return gen502Page(req), nil
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}
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c := goodConns[rand.Intn(len(goodConns))]
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resp, err := c.RoundTrip(req)
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if err != nil {
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ln.Error(ctx, err, c, ln.F{
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"action": "connection_roundtrip",
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})
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defer c.cancel()
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return nil, err
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}
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ln.Log(ctx, c, ln.F{
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"action": "http traffic",
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"remote_addr": req.RemoteAddr,
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"host": req.Host,
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"uri": req.URL.Path,
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"status": resp.Status,
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"status_code": resp.StatusCode,
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"content_length": resp.ContentLength,
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})
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return resp, nil
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}
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// Auth is the authentication info the client passes to the server.
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type Auth struct {
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Token string `json:"token"`
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Domain string `json:"domain"`
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}
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const defaultUser = "Cadey"
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