lib/crunchrun/container_gateway.go

   1 // Copyright (C) The Arvados Authors. All rights reserved.
   2 //
   3 // SPDX-License-Identifier: AGPL-3.0
   4
   5 package crunchrun
   6
   7 import (
   8         "crypto/hmac"
   9         "crypto/rand"
  10         "crypto/rsa"
  11         "crypto/sha256"
  12         "crypto/tls"
  13         "fmt"
  14         "io"
  15         "net"
  16         "net/http"
  17         "net/url"
  18         "os"
  19         "os/exec"
  20         "sync"
  21         "syscall"
  22         "time"
  23
  24         "git.arvados.org/arvados.git/lib/controller/rpc"
  25         "git.arvados.org/arvados.git/lib/selfsigned"
  26         "git.arvados.org/arvados.git/sdk/go/arvados"
  27         "git.arvados.org/arvados.git/sdk/go/auth"
  28         "git.arvados.org/arvados.git/sdk/go/ctxlog"
  29         "git.arvados.org/arvados.git/sdk/go/httpserver"
  30         "github.com/creack/pty"
  31         "github.com/google/shlex"
  32         "github.com/hashicorp/yamux"
  33         "golang.org/x/crypto/ssh"
  34         "golang.org/x/net/context"
  35 )
  36
  37 type GatewayTarget interface {
  38         // Command that will execute cmd inside the container
  39         InjectCommand(ctx context.Context, detachKeys, username string, usingTTY bool, cmd []string) (*exec.Cmd, error)
  40
  41         // IP address inside container
  42         IPAddress() (string, error)
  43 }
  44
  45 type GatewayTargetStub struct{}
  46
  47 func (GatewayTargetStub) IPAddress() (string, error) { return "127.0.0.1", nil }
  48 func (GatewayTargetStub) InjectCommand(ctx context.Context, detachKeys, username string, usingTTY bool, cmd []string) (*exec.Cmd, error) {
  49         return exec.CommandContext(ctx, cmd[0], cmd[1:]...), nil
  50 }
  51
  52 type Gateway struct {
  53         ContainerUUID string
  54         // Caller should set Address to "", or "host:0" or "host:port"
  55         // where host is a known external IP address; port is a
  56         // desired port number to listen on; and ":0" chooses an
  57         // available dynamic port.
  58         //
  59         // If Address is "", Start() listens only on the loopback
  60         // interface (and changes Address to "127.0.0.1:port").
  61         // Otherwise it listens on all interfaces.
  62         //
  63         // If Address is "host:0", Start() updates Address to
  64         // "host:port".
  65         Address    string
  66         AuthSecret string
  67         Target     GatewayTarget
  68         Log        interface {
  69                 Printf(fmt string, args ...interface{})
  70         }
  71         // If non-nil, set up a ContainerGatewayTunnel, so that the
  72         // controller can connect to us even if our external IP
  73         // address is unknown or not routable from controller.
  74         ArvadosClient *arvados.Client
  75
  76         sshConfig   ssh.ServerConfig
  77         requestAuth string
  78         respondAuth string
  79 }
  80
  81 // Start starts an http server that allows authenticated clients to open an
  82 // interactive "docker exec" session and (in future) connect to tcp ports
  83 // inside the docker container.
  84 func (gw *Gateway) Start() error {
  85         gw.sshConfig = ssh.ServerConfig{
  86                 NoClientAuth: true,
  87                 PasswordCallback: func(c ssh.ConnMetadata, pass []byte) (*ssh.Permissions, error) {
  88                         if c.User() == "_" {
  89                                 return nil, nil
  90                         }
  91                         return nil, fmt.Errorf("cannot specify user %q via ssh client", c.User())
  92                 },
  93                 PublicKeyCallback: func(c ssh.ConnMetadata, pubKey ssh.PublicKey) (*ssh.Permissions, error) {
  94                         if c.User() == "_" {
  95                                 return &ssh.Permissions{
  96                                         Extensions: map[string]string{
  97                                                 "pubkey-fp": ssh.FingerprintSHA256(pubKey),
  98                                         },
  99                                 }, nil
 100                         }
 101                         return nil, fmt.Errorf("cannot specify user %q via ssh client", c.User())
 102                 },
 103         }
 104         pvt, err := rsa.GenerateKey(rand.Reader, 2048)
 105         if err != nil {
 106                 return err
 107         }
 108         err = pvt.Validate()
 109         if err != nil {
 110                 return err
 111         }
 112         signer, err := ssh.NewSignerFromKey(pvt)
 113         if err != nil {
 114                 return err
 115         }
 116         gw.sshConfig.AddHostKey(signer)
 117
 118         // Address (typically provided by arvados-dispatch-cloud) is
 119         // HOST:PORT where HOST is our IP address or hostname as seen
 120         // from arvados-controller, and PORT is either the desired
 121         // port where we should run our gateway server, or "0" if we
 122         // should choose an available port.
 123         extAddr := gw.Address
 124         // Generally we can't know which local interface corresponds
 125         // to an externally reachable IP address, so if we expect to
 126         // be reachable by external hosts, we listen on all
 127         // interfaces.
 128         listenHost := ""
 129         if extAddr == "" {
 130                 // If the dispatcher doesn't tell us our external IP
 131                 // address, controller will only be able to connect
 132                 // through the tunnel (see runTunnel), so our gateway
 133                 // server only needs to listen on the loopback
 134                 // interface.
 135                 extAddr = "127.0.0.1:0"
 136                 listenHost = "127.0.0.1"
 137         }
 138         extHost, extPort, err := net.SplitHostPort(extAddr)
 139         if err != nil {
 140                 return err
 141         }
 142         cert, err := selfsigned.CertGenerator{}.Generate()
 143         if err != nil {
 144                 return err
 145         }
 146         h := hmac.New(sha256.New, []byte(gw.AuthSecret))
 147         h.Write(cert.Certificate[0])
 148         gw.requestAuth = fmt.Sprintf("%x", h.Sum(nil))
 149         h.Reset()
 150         h.Write([]byte(gw.requestAuth))
 151         gw.respondAuth = fmt.Sprintf("%x", h.Sum(nil))
 152
 153         srv := &httpserver.Server{
 154                 Server: http.Server{
 155                         Handler: http.HandlerFunc(gw.handleSSH),
 156                         TLSConfig: &tls.Config{
 157                                 Certificates: []tls.Certificate{cert},
 158                         },
 159                 },
 160                 Addr: net.JoinHostPort(listenHost, extPort),
 161         }
 162         err = srv.Start()
 163         if err != nil {
 164                 return err
 165         }
 166         // Get the port number we are listening on (extPort might be
 167         // "0" or a port name, in which case this will be different).
 168         _, listenPort, err := net.SplitHostPort(srv.Addr)
 169         if err != nil {
 170                 return err
 171         }
 172         // When changing state to Running, the caller will want to set
 173         // gateway_address to a "HOST:PORT" that, if controller
 174         // connects to it, will reach this gateway server.
 175         //
 176         // The most likely thing to work is: HOST is our external
 177         // hostname/IP as provided by the caller
 178         // (arvados-dispatch-cloud) or 127.0.0.1 to indicate
 179         // non-tunnel connections aren't available; and PORT is the
 180         // port number we are listening on.
 181         gw.Address = net.JoinHostPort(extHost, listenPort)
 182         if gw.ArvadosClient != nil {
 183                 go gw.maintainTunnel(gw.Address)
 184         }
 185         return nil
 186 }
 187
 188 func (gw *Gateway) maintainTunnel(addr string) {
 189         for ; ; time.Sleep(5 * time.Second) {
 190                 err := gw.runTunnel(addr)
 191                 gw.Log.Printf("runTunnel: %s", err)
 192         }
 193 }
 194
 195 // runTunnel connects to controller and sets up a tunnel through
 196 // which controller can connect to the gateway server at the given
 197 // addr.
 198 func (gw *Gateway) runTunnel(addr string) error {
 199         ctx := auth.NewContext(context.Background(), auth.NewCredentials(gw.ArvadosClient.AuthToken))
 200         arpc := rpc.NewConn("", &url.URL{Scheme: "https", Host: gw.ArvadosClient.APIHost}, gw.ArvadosClient.Insecure, rpc.PassthroughTokenProvider)
 201         tun, err := arpc.ContainerGatewayTunnel(ctx, arvados.ContainerGatewayTunnelOptions{
 202                 UUID:       gw.ContainerUUID,
 203                 AuthSecret: gw.AuthSecret,
 204         })
 205         if err != nil {
 206                 return fmt.Errorf("error creating gateway tunnel: %s", err)
 207         }
 208         mux, err := yamux.Client(tun.Conn, nil)
 209         if err != nil {
 210                 return fmt.Errorf("error setting up mux client end: %s", err)
 211         }
 212         for {
 213                 muxconn, err := mux.Accept()
 214                 if err != nil {
 215                         return err
 216                 }
 217                 gw.Log.Printf("receiving connection from tunnel, remoteAddr %s", muxconn.RemoteAddr().String())
 218                 go func() {
 219                         defer muxconn.Close()
 220                         gwconn, err := net.Dial("tcp", addr)
 221                         if err != nil {
 222                                 gw.Log.Printf("error connecting to %s on behalf of tunnel connection: %s", addr, err)
 223                                 return
 224                         }
 225                         defer gwconn.Close()
 226                         var wg sync.WaitGroup
 227                         wg.Add(2)
 228                         go func() {
 229                                 defer wg.Done()
 230                                 io.Copy(gwconn, muxconn)
 231                         }()
 232                         go func() {
 233                                 defer wg.Done()
 234                                 io.Copy(muxconn, gwconn)
 235                         }()
 236                         wg.Wait()
 237                 }()
 238         }
 239 }
 240
 241 // handleSSH connects to an SSH server that allows the caller to run
 242 // interactive commands as root (or any other desired user) inside the
 243 // container. The tunnel itself can only be created by an
 244 // authenticated caller, so the SSH server itself is wide open (any
 245 // password or key will be accepted).
 246 //
 247 // Requests must have path "/ssh" and the following headers:
 248 //
 249 // Connection: upgrade
 250 // Upgrade: ssh
 251 // X-Arvados-Target-Uuid: uuid of container
 252 // X-Arvados-Authorization: must match
 253 // hmac(AuthSecret,certfingerprint) (this prevents other containers
 254 // and shell nodes from connecting directly)
 255 //
 256 // Optional headers:
 257 //
 258 // X-Arvados-Detach-Keys: argument to "docker exec --detach-keys",
 259 // e.g., "ctrl-p,ctrl-q"
 260 // X-Arvados-Login-Username: argument to "docker exec --user": account
 261 // used to run command(s) inside the container.
 262 func (gw *Gateway) handleSSH(w http.ResponseWriter, req *http.Request) {
 263         // In future we'll handle browser traffic too, but for now the
 264         // only traffic we expect is an SSH tunnel from
 265         // (*lib/controller/localdb.Conn)ContainerSSH()
 266         if req.Method != "POST" || req.Header.Get("Upgrade") != "ssh" {
 267                 http.Error(w, "path not found", http.StatusNotFound)
 268                 return
 269         }
 270         req.ParseForm()
 271         if want := req.Form.Get("uuid"); want != gw.ContainerUUID {
 272                 http.Error(w, fmt.Sprintf("misdirected request: meant for %q but received by crunch-run %q", want, gw.ContainerUUID), http.StatusBadGateway)
 273                 return
 274         }
 275         if req.Header.Get("X-Arvados-Authorization") != gw.requestAuth {
 276                 http.Error(w, "bad X-Arvados-Authorization header", http.StatusUnauthorized)
 277                 return
 278         }
 279         detachKeys := req.Form.Get("detach_keys")
 280         username := req.Form.Get("login_username")
 281         if username == "" {
 282                 username = "root"
 283         }
 284         hj, ok := w.(http.Hijacker)
 285         if !ok {
 286                 http.Error(w, "ResponseWriter does not support connection upgrade", http.StatusInternalServerError)
 287                 return
 288         }
 289         netconn, _, err := hj.Hijack()
 290         if !ok {
 291                 http.Error(w, err.Error(), http.StatusInternalServerError)
 292                 return
 293         }
 294         defer netconn.Close()
 295         w.Header().Set("Connection", "upgrade")
 296         w.Header().Set("Upgrade", "ssh")
 297         w.Header().Set("X-Arvados-Authorization-Response", gw.respondAuth)
 298         netconn.Write([]byte("HTTP/1.1 101 Switching Protocols\r\n"))
 299         w.Header().Write(netconn)
 300         netconn.Write([]byte("\r\n"))
 301
 302         ctx := req.Context()
 303
 304         conn, newchans, reqs, err := ssh.NewServerConn(netconn, &gw.sshConfig)
 305         if err == io.EOF {
 306                 return
 307         } else if err != nil {
 308                 gw.Log.Printf("ssh.NewServerConn: %s", err)
 309                 return
 310         }
 311         defer conn.Close()
 312         go ssh.DiscardRequests(reqs)
 313         for newch := range newchans {
 314                 switch newch.ChannelType() {
 315                 case "direct-tcpip":
 316                         go gw.handleDirectTCPIP(ctx, newch)
 317                 case "session":
 318                         go gw.handleSession(ctx, newch, detachKeys, username)
 319                 default:
 320                         go newch.Reject(ssh.UnknownChannelType, fmt.Sprintf("unsupported channel type %q", newch.ChannelType()))
 321                 }
 322         }
 323 }
 324
 325 func (gw *Gateway) handleDirectTCPIP(ctx context.Context, newch ssh.NewChannel) {
 326         ch, reqs, err := newch.Accept()
 327         if err != nil {
 328                 gw.Log.Printf("accept direct-tcpip channel: %s", err)
 329                 return
 330         }
 331         defer ch.Close()
 332         go ssh.DiscardRequests(reqs)
 333
 334         // RFC 4254 7.2 (copy of channelOpenDirectMsg in
 335         // golang.org/x/crypto/ssh)
 336         var msg struct {
 337                 Raddr string
 338                 Rport uint32
 339                 Laddr string
 340                 Lport uint32
 341         }
 342         err = ssh.Unmarshal(newch.ExtraData(), &msg)
 343         if err != nil {
 344                 fmt.Fprintf(ch.Stderr(), "unmarshal direct-tcpip extradata: %s\n", err)
 345                 return
 346         }
 347         switch msg.Raddr {
 348         case "localhost", "0.0.0.0", "127.0.0.1", "::1", "::":
 349         default:
 350                 fmt.Fprintf(ch.Stderr(), "cannot forward to ports on %q, only localhost\n", msg.Raddr)
 351                 return
 352         }
 353
 354         dstaddr, err := gw.Target.IPAddress()
 355         if err != nil {
 356                 fmt.Fprintf(ch.Stderr(), "container has no IP address: %s\n", err)
 357                 return
 358         } else if dstaddr == "" {
 359                 fmt.Fprintf(ch.Stderr(), "container has no IP address\n")
 360                 return
 361         }
 362
 363         dst := net.JoinHostPort(dstaddr, fmt.Sprintf("%d", msg.Rport))
 364         tcpconn, err := net.Dial("tcp", dst)
 365         if err != nil {
 366                 fmt.Fprintf(ch.Stderr(), "%s: %s\n", dst, err)
 367                 return
 368         }
 369         go func() {
 370                 n, _ := io.Copy(ch, tcpconn)
 371                 ctxlog.FromContext(ctx).Debugf("tcpip: sent %d bytes\n", n)
 372                 ch.CloseWrite()
 373         }()
 374         n, _ := io.Copy(tcpconn, ch)
 375         ctxlog.FromContext(ctx).Debugf("tcpip: received %d bytes\n", n)
 376 }
 377
 378 func (gw *Gateway) handleSession(ctx context.Context, newch ssh.NewChannel, detachKeys, username string) {
 379         ch, reqs, err := newch.Accept()
 380         if err != nil {
 381                 gw.Log.Printf("accept session channel: %s", err)
 382                 return
 383         }
 384         var pty0, tty0 *os.File
 385         // Where to send errors/messages for the client to see
 386         logw := io.Writer(ch.Stderr())
 387         // How to end lines when sending errors/messages to the client
 388         // (changes to \r\n when using a pty)
 389         eol := "\n"
 390         // Env vars to add to child process
 391         termEnv := []string(nil)
 392         for req := range reqs {
 393                 ok := false
 394                 switch req.Type {
 395                 case "shell", "exec":
 396                         ok = true
 397                         var payload struct {
 398                                 Command string
 399                         }
 400                         ssh.Unmarshal(req.Payload, &payload)
 401                         execargs, err := shlex.Split(payload.Command)
 402                         if err != nil {
 403                                 fmt.Fprintf(logw, "error parsing supplied command: %s"+eol, err)
 404                                 return
 405                         }
 406                         if len(execargs) == 0 {
 407                                 execargs = []string{"/bin/bash", "-login"}
 408                         }
 409                         go func() {
 410                                 var resp struct {
 411                                         Status uint32
 412                                 }
 413                                 defer func() {
 414                                         ch.SendRequest("exit-status", false, ssh.Marshal(&resp))
 415                                         ch.Close()
 416                                 }()
 417
 418                                 cmd, err := gw.Target.InjectCommand(ctx, detachKeys, username, tty0 != nil, execargs)
 419                                 if err != nil {
 420                                         fmt.Fprintln(ch.Stderr(), err)
 421                                         ch.CloseWrite()
 422                                         resp.Status = 1
 423                                         return
 424                                 }
 425                                 cmd.Stdin = ch
 426                                 cmd.Stdout = ch
 427                                 cmd.Stderr = ch.Stderr()
 428                                 if tty0 != nil {
 429                                         cmd.Stdin = tty0
 430                                         cmd.Stdout = tty0
 431                                         cmd.Stderr = tty0
 432                                         var wg sync.WaitGroup
 433                                         defer wg.Wait()
 434                                         wg.Add(2)
 435                                         go func() { io.Copy(ch, pty0); wg.Done() }()
 436                                         go func() { io.Copy(pty0, ch); wg.Done() }()
 437                                         // Send our own debug messages to tty as well.
 438                                         logw = tty0
 439                                 }
 440                                 cmd.SysProcAttr = &syscall.SysProcAttr{
 441                                         Setctty: tty0 != nil,
 442                                         Setsid:  true,
 443                                 }
 444                                 cmd.Env = append(os.Environ(), termEnv...)
 445                                 err = cmd.Run()
 446                                 if exiterr, ok := err.(*exec.ExitError); ok {
 447                                         if status, ok := exiterr.Sys().(syscall.WaitStatus); ok {
 448                                                 resp.Status = uint32(status.ExitStatus())
 449                                         }
 450                                 } else if err != nil {
 451                                         // Propagate errors like `exec: "docker": executable file not found in $PATH`
 452                                         fmt.Fprintln(ch.Stderr(), err)
 453                                 }
 454                                 errClose := ch.CloseWrite()
 455                                 if resp.Status == 0 && (err != nil || errClose != nil) {
 456                                         resp.Status = 1
 457                                 }
 458                         }()
 459                 case "pty-req":
 460                         eol = "\r\n"
 461                         p, t, err := pty.Open()
 462                         if err != nil {
 463                                 fmt.Fprintf(ch.Stderr(), "pty failed: %s"+eol, err)
 464                                 break
 465                         }
 466                         defer p.Close()
 467                         defer t.Close()
 468                         pty0, tty0 = p, t
 469                         ok = true
 470                         var payload struct {
 471                                 Term string
 472                                 Cols uint32
 473                                 Rows uint32
 474                                 X    uint32
 475                                 Y    uint32
 476                         }
 477                         ssh.Unmarshal(req.Payload, &payload)
 478                         termEnv = []string{"TERM=" + payload.Term, "USE_TTY=1"}
 479                         err = pty.Setsize(pty0, &pty.Winsize{Rows: uint16(payload.Rows), Cols: uint16(payload.Cols), X: uint16(payload.X), Y: uint16(payload.Y)})
 480                         if err != nil {
 481                                 fmt.Fprintf(logw, "pty-req: setsize failed: %s"+eol, err)
 482                         }
 483                 case "window-change":
 484                         var payload struct {
 485                                 Cols uint32
 486                                 Rows uint32
 487                                 X    uint32
 488                                 Y    uint32
 489                         }
 490                         ssh.Unmarshal(req.Payload, &payload)
 491                         err := pty.Setsize(pty0, &pty.Winsize{Rows: uint16(payload.Rows), Cols: uint16(payload.Cols), X: uint16(payload.X), Y: uint16(payload.Y)})
 492                         if err != nil {
 493                                 fmt.Fprintf(logw, "window-change: setsize failed: %s"+eol, err)
 494                                 break
 495                         }
 496                         ok = true
 497                 case "env":
 498                         // TODO: implement "env"
 499                         // requests by setting env
 500                         // vars in the docker-exec
 501                         // command (not docker-exec's
 502                         // own environment, which
 503                         // would be a gaping security
 504                         // hole).
 505                 default:
 506                         // fmt.Fprintf(logw, "declining %q req"+eol, req.Type)
 507                 }
 508                 if req.WantReply {
 509                         req.Reply(ok, nil)
 510                 }
 511         }
 512 }