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         // When a tunnel is connected or reconnected, this func (if
  77         // not nil) will be called with the InternalURL of the
  78         // controller process at the other end of the tunnel.
  79         UpdateTunnelURL func(url string)
  80
  81         sshConfig   ssh.ServerConfig
  82         requestAuth string
  83         respondAuth string
  84 }
  85
  86 // Start starts an http server that allows authenticated clients to open an
  87 // interactive "docker exec" session and (in future) connect to tcp ports
  88 // inside the docker container.
  89 func (gw *Gateway) Start() error {
  90         gw.sshConfig = ssh.ServerConfig{
  91                 NoClientAuth: true,
  92                 PasswordCallback: func(c ssh.ConnMetadata, pass []byte) (*ssh.Permissions, error) {
  93                         if c.User() == "_" {
  94                                 return nil, nil
  95                         }
  96                         return nil, fmt.Errorf("cannot specify user %q via ssh client", c.User())
  97                 },
  98                 PublicKeyCallback: func(c ssh.ConnMetadata, pubKey ssh.PublicKey) (*ssh.Permissions, error) {
  99                         if c.User() == "_" {
 100                                 return &ssh.Permissions{
 101                                         Extensions: map[string]string{
 102                                                 "pubkey-fp": ssh.FingerprintSHA256(pubKey),
 103                                         },
 104                                 }, nil
 105                         }
 106                         return nil, fmt.Errorf("cannot specify user %q via ssh client", c.User())
 107                 },
 108         }
 109         pvt, err := rsa.GenerateKey(rand.Reader, 2048)
 110         if err != nil {
 111                 return err
 112         }
 113         err = pvt.Validate()
 114         if err != nil {
 115                 return err
 116         }
 117         signer, err := ssh.NewSignerFromKey(pvt)
 118         if err != nil {
 119                 return err
 120         }
 121         gw.sshConfig.AddHostKey(signer)
 122
 123         // Address (typically provided by arvados-dispatch-cloud) is
 124         // HOST:PORT where HOST is our IP address or hostname as seen
 125         // from arvados-controller, and PORT is either the desired
 126         // port where we should run our gateway server, or "0" if we
 127         // should choose an available port.
 128         extAddr := gw.Address
 129         // Generally we can't know which local interface corresponds
 130         // to an externally reachable IP address, so if we expect to
 131         // be reachable by external hosts, we listen on all
 132         // interfaces.
 133         listenHost := ""
 134         if extAddr == "" {
 135                 // If the dispatcher doesn't tell us our external IP
 136                 // address, controller will only be able to connect
 137                 // through the tunnel (see runTunnel), so our gateway
 138                 // server only needs to listen on the loopback
 139                 // interface.
 140                 extAddr = "127.0.0.1:0"
 141                 listenHost = "127.0.0.1"
 142         }
 143         extHost, extPort, err := net.SplitHostPort(extAddr)
 144         if err != nil {
 145                 return err
 146         }
 147         cert, err := selfsigned.CertGenerator{}.Generate()
 148         if err != nil {
 149                 return err
 150         }
 151         h := hmac.New(sha256.New, []byte(gw.AuthSecret))
 152         h.Write(cert.Certificate[0])
 153         gw.requestAuth = fmt.Sprintf("%x", h.Sum(nil))
 154         h.Reset()
 155         h.Write([]byte(gw.requestAuth))
 156         gw.respondAuth = fmt.Sprintf("%x", h.Sum(nil))
 157
 158         srv := &httpserver.Server{
 159                 Server: http.Server{
 160                         Handler: http.HandlerFunc(gw.handleSSH),
 161                         TLSConfig: &tls.Config{
 162                                 Certificates: []tls.Certificate{cert},
 163                         },
 164                 },
 165                 Addr: net.JoinHostPort(listenHost, extPort),
 166         }
 167         err = srv.Start()
 168         if err != nil {
 169                 return err
 170         }
 171         go func() {
 172                 err := srv.Wait()
 173                 gw.Log.Printf("gateway server stopped: %s", err)
 174         }()
 175         // Get the port number we are listening on (extPort might be
 176         // "0" or a port name, in which case this will be different).
 177         _, listenPort, err := net.SplitHostPort(srv.Addr)
 178         if err != nil {
 179                 return err
 180         }
 181         // When changing state to Running, the caller will want to set
 182         // gateway_address to a "HOST:PORT" that, if controller
 183         // connects to it, will reach this gateway server.
 184         //
 185         // The most likely thing to work is: HOST is our external
 186         // hostname/IP as provided by the caller
 187         // (arvados-dispatch-cloud) or 127.0.0.1 to indicate
 188         // non-tunnel connections aren't available; and PORT is the
 189         // port number we are listening on.
 190         gw.Address = net.JoinHostPort(extHost, listenPort)
 191         gw.Log.Printf("gateway server listening at %s", gw.Address)
 192         if gw.ArvadosClient != nil {
 193                 go gw.maintainTunnel(gw.Address)
 194         }
 195         return nil
 196 }
 197
 198 func (gw *Gateway) maintainTunnel(addr string) {
 199         for ; ; time.Sleep(5 * time.Second) {
 200                 err := gw.runTunnel(addr)
 201                 gw.Log.Printf("runTunnel: %s", err)
 202         }
 203 }
 204
 205 // runTunnel connects to controller and sets up a tunnel through
 206 // which controller can connect to the gateway server at the given
 207 // addr.
 208 func (gw *Gateway) runTunnel(addr string) error {
 209         ctx := auth.NewContext(context.Background(), auth.NewCredentials(gw.ArvadosClient.AuthToken))
 210         arpc := rpc.NewConn("", &url.URL{Scheme: "https", Host: gw.ArvadosClient.APIHost}, gw.ArvadosClient.Insecure, rpc.PassthroughTokenProvider)
 211         tun, err := arpc.ContainerGatewayTunnel(ctx, arvados.ContainerGatewayTunnelOptions{
 212                 UUID:       gw.ContainerUUID,
 213                 AuthSecret: gw.AuthSecret,
 214         })
 215         if err != nil {
 216                 return fmt.Errorf("error creating gateway tunnel: %s", err)
 217         }
 218         mux, err := yamux.Client(tun.Conn, nil)
 219         if err != nil {
 220                 return fmt.Errorf("error setting up mux client end: %s", err)
 221         }
 222         if url := tun.Header.Get("X-Arvados-Internal-Url"); url != "" && gw.UpdateTunnelURL != nil {
 223                 gw.UpdateTunnelURL(url)
 224         }
 225         for {
 226                 muxconn, err := mux.AcceptStream()
 227                 if err != nil {
 228                         return err
 229                 }
 230                 gw.Log.Printf("tunnel connection %d started", muxconn.StreamID())
 231                 go func() {
 232                         defer muxconn.Close()
 233                         gwconn, err := net.Dial("tcp", addr)
 234                         if err != nil {
 235                                 gw.Log.Printf("tunnel connection %d: error connecting to %s: %s", muxconn.StreamID(), addr, err)
 236                                 return
 237                         }
 238                         defer gwconn.Close()
 239                         var wg sync.WaitGroup
 240                         wg.Add(2)
 241                         go func() {
 242                                 defer wg.Done()
 243                                 _, err := io.Copy(gwconn, muxconn)
 244                                 if err != nil {
 245                                         gw.Log.Printf("tunnel connection %d: mux end: %s", muxconn.StreamID(), err)
 246                                 }
 247                                 gwconn.Close()
 248                         }()
 249                         go func() {
 250                                 defer wg.Done()
 251                                 _, err := io.Copy(muxconn, gwconn)
 252                                 if err != nil {
 253                                         gw.Log.Printf("tunnel connection %d: gateway end: %s", muxconn.StreamID(), err)
 254                                 }
 255                                 muxconn.Close()
 256                         }()
 257                         wg.Wait()
 258                         gw.Log.Printf("tunnel connection %d finished", muxconn.StreamID())
 259                 }()
 260         }
 261 }
 262
 263 // handleSSH connects to an SSH server that allows the caller to run
 264 // interactive commands as root (or any other desired user) inside the
 265 // container. The tunnel itself can only be created by an
 266 // authenticated caller, so the SSH server itself is wide open (any
 267 // password or key will be accepted).
 268 //
 269 // Requests must have path "/ssh" and the following headers:
 270 //
 271 // Connection: upgrade
 272 // Upgrade: ssh
 273 // X-Arvados-Target-Uuid: uuid of container
 274 // X-Arvados-Authorization: must match
 275 // hmac(AuthSecret,certfingerprint) (this prevents other containers
 276 // and shell nodes from connecting directly)
 277 //
 278 // Optional headers:
 279 //
 280 // X-Arvados-Detach-Keys: argument to "docker exec --detach-keys",
 281 // e.g., "ctrl-p,ctrl-q"
 282 // X-Arvados-Login-Username: argument to "docker exec --user": account
 283 // used to run command(s) inside the container.
 284 func (gw *Gateway) handleSSH(w http.ResponseWriter, req *http.Request) {
 285         // In future we'll handle browser traffic too, but for now the
 286         // only traffic we expect is an SSH tunnel from
 287         // (*lib/controller/localdb.Conn)ContainerSSH()
 288         if req.Method != "POST" || req.Header.Get("Upgrade") != "ssh" {
 289                 http.Error(w, "path not found", http.StatusNotFound)
 290                 return
 291         }
 292         req.ParseForm()
 293         if want := req.Form.Get("uuid"); want != gw.ContainerUUID {
 294                 http.Error(w, fmt.Sprintf("misdirected request: meant for %q but received by crunch-run %q", want, gw.ContainerUUID), http.StatusBadGateway)
 295                 return
 296         }
 297         if req.Header.Get("X-Arvados-Authorization") != gw.requestAuth {
 298                 http.Error(w, "bad X-Arvados-Authorization header", http.StatusUnauthorized)
 299                 return
 300         }
 301         detachKeys := req.Form.Get("detach_keys")
 302         username := req.Form.Get("login_username")
 303         if username == "" {
 304                 username = "root"
 305         }
 306         hj, ok := w.(http.Hijacker)
 307         if !ok {
 308                 http.Error(w, "ResponseWriter does not support connection upgrade", http.StatusInternalServerError)
 309                 return
 310         }
 311         netconn, _, err := hj.Hijack()
 312         if !ok {
 313                 http.Error(w, err.Error(), http.StatusInternalServerError)
 314                 return
 315         }
 316         defer netconn.Close()
 317         w.Header().Set("Connection", "upgrade")
 318         w.Header().Set("Upgrade", "ssh")
 319         w.Header().Set("X-Arvados-Authorization-Response", gw.respondAuth)
 320         netconn.Write([]byte("HTTP/1.1 101 Switching Protocols\r\n"))
 321         w.Header().Write(netconn)
 322         netconn.Write([]byte("\r\n"))
 323
 324         ctx := req.Context()
 325
 326         conn, newchans, reqs, err := ssh.NewServerConn(netconn, &gw.sshConfig)
 327         if err == io.EOF {
 328                 return
 329         } else if err != nil {
 330                 gw.Log.Printf("ssh.NewServerConn: %s", err)
 331                 return
 332         }
 333         defer conn.Close()
 334         go ssh.DiscardRequests(reqs)
 335         for newch := range newchans {
 336                 switch newch.ChannelType() {
 337                 case "direct-tcpip":
 338                         go gw.handleDirectTCPIP(ctx, newch)
 339                 case "session":
 340                         go gw.handleSession(ctx, newch, detachKeys, username)
 341                 default:
 342                         go newch.Reject(ssh.UnknownChannelType, fmt.Sprintf("unsupported channel type %q", newch.ChannelType()))
 343                 }
 344         }
 345 }
 346
 347 func (gw *Gateway) handleDirectTCPIP(ctx context.Context, newch ssh.NewChannel) {
 348         ch, reqs, err := newch.Accept()
 349         if err != nil {
 350                 gw.Log.Printf("accept direct-tcpip channel: %s", err)
 351                 return
 352         }
 353         defer ch.Close()
 354         go ssh.DiscardRequests(reqs)
 355
 356         // RFC 4254 7.2 (copy of channelOpenDirectMsg in
 357         // golang.org/x/crypto/ssh)
 358         var msg struct {
 359                 Raddr string
 360                 Rport uint32
 361                 Laddr string
 362                 Lport uint32
 363         }
 364         err = ssh.Unmarshal(newch.ExtraData(), &msg)
 365         if err != nil {
 366                 fmt.Fprintf(ch.Stderr(), "unmarshal direct-tcpip extradata: %s\n", err)
 367                 return
 368         }
 369         switch msg.Raddr {
 370         case "localhost", "0.0.0.0", "127.0.0.1", "::1", "::":
 371         default:
 372                 fmt.Fprintf(ch.Stderr(), "cannot forward to ports on %q, only localhost\n", msg.Raddr)
 373                 return
 374         }
 375
 376         dstaddr, err := gw.Target.IPAddress()
 377         if err != nil {
 378                 fmt.Fprintf(ch.Stderr(), "container has no IP address: %s\n", err)
 379                 return
 380         } else if dstaddr == "" {
 381                 fmt.Fprintf(ch.Stderr(), "container has no IP address\n")
 382                 return
 383         }
 384
 385         dst := net.JoinHostPort(dstaddr, fmt.Sprintf("%d", msg.Rport))
 386         tcpconn, err := net.Dial("tcp", dst)
 387         if err != nil {
 388                 fmt.Fprintf(ch.Stderr(), "%s: %s\n", dst, err)
 389                 return
 390         }
 391         go func() {
 392                 n, _ := io.Copy(ch, tcpconn)
 393                 ctxlog.FromContext(ctx).Debugf("tcpip: sent %d bytes\n", n)
 394                 ch.CloseWrite()
 395         }()
 396         n, _ := io.Copy(tcpconn, ch)
 397         ctxlog.FromContext(ctx).Debugf("tcpip: received %d bytes\n", n)
 398 }
 399
 400 func (gw *Gateway) handleSession(ctx context.Context, newch ssh.NewChannel, detachKeys, username string) {
 401         ch, reqs, err := newch.Accept()
 402         if err != nil {
 403                 gw.Log.Printf("error accepting session channel: %s", err)
 404                 return
 405         }
 406         defer ch.Close()
 407
 408         var pty0, tty0 *os.File
 409         // Where to send errors/messages for the client to see
 410         logw := io.Writer(ch.Stderr())
 411         // How to end lines when sending errors/messages to the client
 412         // (changes to \r\n when using a pty)
 413         eol := "\n"
 414         // Env vars to add to child process
 415         termEnv := []string(nil)
 416
 417         started := 0
 418         wantClose := make(chan struct{})
 419         for {
 420                 var req *ssh.Request
 421                 select {
 422                 case r, ok := <-reqs:
 423                         if !ok {
 424                                 return
 425                         }
 426                         req = r
 427                 case <-wantClose:
 428                         return
 429                 }
 430                 ok := false
 431                 switch req.Type {
 432                 case "shell", "exec":
 433                         if started++; started != 1 {
 434                                 // RFC 4254 6.5: "Only one of these
 435                                 // requests can succeed per channel."
 436                                 break
 437                         }
 438                         ok = true
 439                         var payload struct {
 440                                 Command string
 441                         }
 442                         ssh.Unmarshal(req.Payload, &payload)
 443                         execargs, err := shlex.Split(payload.Command)
 444                         if err != nil {
 445                                 fmt.Fprintf(logw, "error parsing supplied command: %s"+eol, err)
 446                                 return
 447                         }
 448                         if len(execargs) == 0 {
 449                                 execargs = []string{"/bin/bash", "-login"}
 450                         }
 451                         go func() {
 452                                 var resp struct {
 453                                         Status uint32
 454                                 }
 455                                 defer func() {
 456                                         ch.SendRequest("exit-status", false, ssh.Marshal(&resp))
 457                                         close(wantClose)
 458                                 }()
 459
 460                                 cmd, err := gw.Target.InjectCommand(ctx, detachKeys, username, tty0 != nil, execargs)
 461                                 if err != nil {
 462                                         fmt.Fprintln(ch.Stderr(), err)
 463                                         ch.CloseWrite()
 464                                         resp.Status = 1
 465                                         return
 466                                 }
 467                                 if tty0 != nil {
 468                                         cmd.Stdin = tty0
 469                                         cmd.Stdout = tty0
 470                                         cmd.Stderr = tty0
 471                                         go io.Copy(ch, pty0)
 472                                         go io.Copy(pty0, ch)
 473                                         // Send our own debug messages to tty as well.
 474                                         logw = tty0
 475                                 } else {
 476                                         // StdinPipe may seem
 477                                         // superfluous here, but it's
 478                                         // not: it causes cmd.Run() to
 479                                         // return when the subprocess
 480                                         // exits. Without it, Run()
 481                                         // waits for stdin to close,
 482                                         // which causes "ssh ... echo
 483                                         // ok" (with the client's
 484                                         // stdin connected to a
 485                                         // terminal or something) to
 486                                         // hang.
 487                                         stdin, err := cmd.StdinPipe()
 488                                         if err != nil {
 489                                                 fmt.Fprintln(ch.Stderr(), err)
 490                                                 ch.CloseWrite()
 491                                                 resp.Status = 1
 492                                                 return
 493                                         }
 494                                         go func() {
 495                                                 io.Copy(stdin, ch)
 496                                                 stdin.Close()
 497                                         }()
 498                                         cmd.Stdout = ch
 499                                         cmd.Stderr = ch.Stderr()
 500                                 }
 501                                 cmd.SysProcAttr = &syscall.SysProcAttr{
 502                                         Setctty: tty0 != nil,
 503                                         Setsid:  true,
 504                                 }
 505                                 cmd.Env = append(os.Environ(), termEnv...)
 506                                 err = cmd.Run()
 507                                 if exiterr, ok := err.(*exec.ExitError); ok {
 508                                         if status, ok := exiterr.Sys().(syscall.WaitStatus); ok {
 509                                                 resp.Status = uint32(status.ExitStatus())
 510                                         }
 511                                 } else if err != nil {
 512                                         // Propagate errors like `exec: "docker": executable file not found in $PATH`
 513                                         fmt.Fprintln(ch.Stderr(), err)
 514                                 }
 515                                 errClose := ch.CloseWrite()
 516                                 if resp.Status == 0 && (err != nil || errClose != nil) {
 517                                         resp.Status = 1
 518                                 }
 519                         }()
 520                 case "pty-req":
 521                         eol = "\r\n"
 522                         p, t, err := pty.Open()
 523                         if err != nil {
 524                                 fmt.Fprintf(ch.Stderr(), "pty failed: %s"+eol, err)
 525                                 break
 526                         }
 527                         defer p.Close()
 528                         defer t.Close()
 529                         pty0, tty0 = p, t
 530                         ok = true
 531                         var payload struct {
 532                                 Term string
 533                                 Cols uint32
 534                                 Rows uint32
 535                                 X    uint32
 536                                 Y    uint32
 537                         }
 538                         ssh.Unmarshal(req.Payload, &payload)
 539                         termEnv = []string{"TERM=" + payload.Term, "USE_TTY=1"}
 540                         err = pty.Setsize(pty0, &pty.Winsize{Rows: uint16(payload.Rows), Cols: uint16(payload.Cols), X: uint16(payload.X), Y: uint16(payload.Y)})
 541                         if err != nil {
 542                                 fmt.Fprintf(logw, "pty-req: setsize failed: %s"+eol, err)
 543                         }
 544                 case "window-change":
 545                         var payload struct {
 546                                 Cols uint32
 547                                 Rows uint32
 548                                 X    uint32
 549                                 Y    uint32
 550                         }
 551                         ssh.Unmarshal(req.Payload, &payload)
 552                         err := pty.Setsize(pty0, &pty.Winsize{Rows: uint16(payload.Rows), Cols: uint16(payload.Cols), X: uint16(payload.X), Y: uint16(payload.Y)})
 553                         if err != nil {
 554                                 fmt.Fprintf(logw, "window-change: setsize failed: %s"+eol, err)
 555                                 break
 556                         }
 557                         ok = true
 558                 case "env":
 559                         // TODO: implement "env"
 560                         // requests by setting env
 561                         // vars in the docker-exec
 562                         // command (not docker-exec's
 563                         // own environment, which
 564                         // would be a gaping security
 565                         // hole).
 566                 default:
 567                         fmt.Fprintf(logw, "declined request %q on ssh channel"+eol, req.Type)
 568                 }
 569                 if req.WantReply {
 570                         req.Reply(ok, nil)
 571                 }
 572         }
 573 }