lib/controller/localdb/container_gateway.go

   1 // Copyright (C) The Arvados Authors. All rights reserved.
   2 //
   3 // SPDX-License-Identifier: AGPL-3.0
   4
   5 package localdb
   6
   7 import (
   8         "bufio"
   9         "bytes"
  10         "context"
  11         "crypto/hmac"
  12         "crypto/sha256"
  13         "crypto/subtle"
  14         "crypto/tls"
  15         "crypto/x509"
  16         "errors"
  17         "fmt"
  18         "io"
  19         "io/ioutil"
  20         "net"
  21         "net/http"
  22         "net/http/httputil"
  23         "net/url"
  24         "os"
  25         "strings"
  26
  27         "git.arvados.org/arvados.git/lib/controller/rpc"
  28         "git.arvados.org/arvados.git/lib/service"
  29         "git.arvados.org/arvados.git/lib/webdavfs"
  30         "git.arvados.org/arvados.git/sdk/go/arvados"
  31         "git.arvados.org/arvados.git/sdk/go/auth"
  32         "git.arvados.org/arvados.git/sdk/go/ctxlog"
  33         "git.arvados.org/arvados.git/sdk/go/httpserver"
  34         "github.com/hashicorp/yamux"
  35         "golang.org/x/net/webdav"
  36 )
  37
  38 var (
  39         forceProxyForTest       = false
  40         forceInternalURLForTest *arvados.URL
  41 )
  42
  43 // ContainerRequestLog returns a WebDAV handler that reads logs from
  44 // the indicated container request. It works by proxying the incoming
  45 // HTTP request to
  46 //
  47 //   - the container gateway, if there is an associated container that
  48 //     is running
  49 //
  50 //   - a different controller process, if there is a running container
  51 //     whose gateway is accessible through a tunnel to a different
  52 //     controller process
  53 //
  54 //   - keep-web, if saved logs exist and there is no gateway (or the
  55 //     associated container is finished)
  56 //
  57 //   - an empty-collection stub, if there is no gateway and no saved
  58 //     log
  59 //
  60 // For an incoming request
  61 //
  62 //      GET /arvados/v1/container_requests/{cr_uuid}/log/{c_uuid}{/c_log_path}
  63 //
  64 // The upstream request may be to {c_uuid}'s container gateway
  65 //
  66 //      GET /arvados/v1/container_requests/{cr_uuid}/log/{c_uuid}{/c_log_path}
  67 //      X-Webdav-Prefix: /arvados/v1/container_requests/{cr_uuid}/log/{c_uuid}
  68 //      X-Webdav-Source: /log
  69 //
  70 // ...or the upstream request may be to keep-web (where {cr_log_uuid}
  71 // is the container request log collection UUID)
  72 //
  73 //      GET /arvados/v1/container_requests/{cr_uuid}/log/{c_uuid}{/c_log_path}
  74 //      Host: {cr_log_uuid}.internal
  75 //      X-Webdav-Prefix: /arvados/v1/container_requests/{cr_uuid}/log
  76 //      X-Arvados-Container-Uuid: {c_uuid}
  77 //
  78 // ...or the request may be handled locally using an empty-collection
  79 // stub.
  80 func (conn *Conn) ContainerRequestLog(ctx context.Context, opts arvados.ContainerLogOptions) (http.Handler, error) {
  81         cr, err := conn.railsProxy.ContainerRequestGet(ctx, arvados.GetOptions{UUID: opts.UUID, Select: []string{"uuid", "container_uuid", "log_uuid"}})
  82         if err != nil {
  83                 if se := httpserver.HTTPStatusError(nil); errors.As(err, &se) && se.HTTPStatus() == http.StatusUnauthorized {
  84                         // Hint to WebDAV client that we accept HTTP basic auth.
  85                         return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
  86                                 w.Header().Set("Www-Authenticate", "Basic realm=\"collections\"")
  87                                 w.WriteHeader(http.StatusUnauthorized)
  88                         }), nil
  89                 }
  90                 return nil, err
  91         }
  92         ctr, err := conn.railsProxy.ContainerGet(ctx, arvados.GetOptions{UUID: cr.ContainerUUID, Select: []string{"uuid", "state", "gateway_address"}})
  93         if err != nil {
  94                 return nil, err
  95         }
  96         // .../log/{ctr.UUID} is a directory where the currently
  97         // assigned container's log data [will] appear (as opposed to
  98         // previous attempts in .../log/{previous_ctr_uuid}). Requests
  99         // that are outside that directory, and requests on a
 100         // non-running container, are proxied to keep-web instead of
 101         // going through the container gateway system.
 102         //
 103         // Side note: a depth>1 directory tree listing starting at
 104         // .../{cr_uuid}/log will only include subdirectories for
 105         // finished containers, i.e., will not include a subdirectory
 106         // with log data for a current (unfinished) container UUID.
 107         // In order to access live logs, a client must look up the
 108         // container_uuid field of the container request record, and
 109         // explicitly request a path under .../{cr_uuid}/log/{c_uuid}.
 110         if ctr.GatewayAddress == "" ||
 111                 (ctr.State != arvados.ContainerStateLocked && ctr.State != arvados.ContainerStateRunning) ||
 112                 !(opts.Path == "/"+ctr.UUID || strings.HasPrefix(opts.Path, "/"+ctr.UUID+"/")) {
 113                 return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 114                         conn.serveContainerRequestLogViaKeepWeb(opts, cr, w, r)
 115                 }), nil
 116         }
 117         dial, arpc, err := conn.findGateway(ctx, ctr, opts.NoForward)
 118         if err != nil {
 119                 return nil, err
 120         }
 121         if arpc != nil {
 122                 opts.NoForward = true
 123                 return arpc.ContainerRequestLog(ctx, opts)
 124         }
 125         return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 126                 r = r.WithContext(ctx)
 127                 var proxyReq *http.Request
 128                 var proxyErr error
 129                 var expectRespondAuth string
 130                 proxy := &httputil.ReverseProxy{
 131                         // Our custom Transport:
 132                         //
 133                         // - Uses a custom dialer to connect to the
 134                         // gateway (either directly or through a
 135                         // tunnel set up though ContainerTunnel)
 136                         //
 137                         // - Verifies the gateway's TLS certificate
 138                         // using X-Arvados-Authorization headers.
 139                         //
 140                         // This involves modifying the outgoing
 141                         // request header in DialTLSContext.
 142                         // (ReverseProxy certainly doesn't expect us
 143                         // to do this, but it works.)
 144                         Transport: &http.Transport{
 145                                 DialTLSContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
 146                                         tlsconn, requestAuth, respondAuth, err := dial()
 147                                         if err != nil {
 148                                                 return nil, err
 149                                         }
 150                                         proxyReq.Header.Set("X-Arvados-Authorization", requestAuth)
 151                                         expectRespondAuth = respondAuth
 152                                         return tlsconn, nil
 153                                 },
 154                         },
 155                         Director: func(r *http.Request) {
 156                                 // Scheme/host of incoming r.URL are
 157                                 // irrelevant now, and may even be
 158                                 // missing. Host is ignored by our
 159                                 // DialTLSContext, but we need a
 160                                 // generic syntactically correct URL
 161                                 // for net/http to work with.
 162                                 r.URL.Scheme = "https"
 163                                 r.URL.Host = "0.0.0.0:0"
 164                                 r.Header.Set("X-Arvados-Container-Gateway-Uuid", ctr.UUID)
 165                                 r.Header.Set("X-Webdav-Prefix", "/arvados/v1/container_requests/"+cr.UUID+"/log/"+ctr.UUID)
 166                                 r.Header.Set("X-Webdav-Source", "/log")
 167                                 proxyReq = r
 168                         },
 169                         ModifyResponse: func(resp *http.Response) error {
 170                                 if resp.Header.Get("X-Arvados-Authorization-Response") != expectRespondAuth {
 171                                         // Note this is how we detect
 172                                         // an attacker-in-the-middle.
 173                                         return httpserver.ErrorWithStatus(errors.New("bad X-Arvados-Authorization-Response header"), http.StatusBadGateway)
 174                                 }
 175                                 return nil
 176                         },
 177                         ErrorHandler: func(w http.ResponseWriter, r *http.Request, err error) {
 178                                 proxyErr = err
 179                         },
 180                 }
 181                 proxy.ServeHTTP(w, r)
 182                 if proxyErr == nil {
 183                         // proxy succeeded
 184                         return
 185                 }
 186                 // If proxying to the container gateway fails, it
 187                 // might be caused by a race where crunch-run exited
 188                 // after we decided (above) the log was not final.
 189                 // In that case we should proxy to keep-web.
 190                 ctr, err := conn.railsProxy.ContainerGet(ctx, arvados.GetOptions{
 191                         UUID:   ctr.UUID,
 192                         Select: []string{"uuid", "state", "gateway_address", "log"},
 193                 })
 194                 if err != nil {
 195                         // Lost access to the container record?
 196                         httpserver.Error(w, "error re-fetching container record: "+err.Error(), http.StatusServiceUnavailable)
 197                 } else if ctr.State == arvados.ContainerStateLocked || ctr.State == arvados.ContainerStateRunning {
 198                         // No race, proxyErr was the best we can do
 199                         httpserver.Error(w, "proxy error: "+proxyErr.Error(), http.StatusServiceUnavailable)
 200                 } else {
 201                         conn.serveContainerRequestLogViaKeepWeb(opts, cr, w, r)
 202                 }
 203         }), nil
 204 }
 205
 206 // serveContainerLogViaKeepWeb handles a request for saved container
 207 // log content by proxying to one of the configured keep-web servers.
 208 //
 209 // It tries to choose a keep-web server that is running on this host.
 210 func (conn *Conn) serveContainerRequestLogViaKeepWeb(opts arvados.ContainerLogOptions, cr arvados.ContainerRequest, w http.ResponseWriter, r *http.Request) {
 211         if cr.LogUUID == "" {
 212                 // Special case: if no log data exists yet, we serve
 213                 // an empty collection by ourselves instead of
 214                 // proxying to keep-web.
 215                 conn.serveEmptyDir("/arvados/v1/container_requests/"+cr.UUID+"/log", w, r)
 216                 return
 217         }
 218         myURL, _ := service.URLFromContext(r.Context())
 219         u := url.URL(myURL)
 220         myHostname := u.Hostname()
 221         var webdavBase arvados.URL
 222         var ok bool
 223         for webdavBase = range conn.cluster.Services.WebDAV.InternalURLs {
 224                 ok = true
 225                 u := url.URL(webdavBase)
 226                 if h := u.Hostname(); h == "127.0.0.1" || h == "0.0.0.0" || h == "::1" || h == myHostname {
 227                         // Prefer a keep-web service running on the
 228                         // same host as us. (If we don't find one, we
 229                         // pick one arbitrarily.)
 230                         break
 231                 }
 232         }
 233         if !ok {
 234                 httpserver.Error(w, "no internalURLs configured for WebDAV service", http.StatusInternalServerError)
 235                 return
 236         }
 237         proxy := &httputil.ReverseProxy{
 238                 Director: func(r *http.Request) {
 239                         r.URL.Scheme = webdavBase.Scheme
 240                         r.URL.Host = webdavBase.Host
 241                         // Outgoing Host header specifies the
 242                         // collection ID.
 243                         r.Host = cr.LogUUID + ".internal"
 244                         // We already checked permission on the
 245                         // container, so we can use a root token here
 246                         // instead of counting on the "access to log
 247                         // via container request and container"
 248                         // permission check, which can be racy when a
 249                         // request gets retried with a new container.
 250                         r.Header.Set("Authorization", "Bearer "+conn.cluster.SystemRootToken)
 251                         // We can't change r.URL.Path without
 252                         // confusing WebDAV (request body and response
 253                         // headers refer to the same paths) so we tell
 254                         // keep-web to map the log collection onto the
 255                         // containers/X/log/ namespace.
 256                         r.Header.Set("X-Webdav-Prefix", "/arvados/v1/container_requests/"+cr.UUID+"/log")
 257                         if len(opts.Path) >= 28 && opts.Path[6:13] == "-dz642-" {
 258                                 // "/arvados/v1/container_requests/{crUUID}/log/{cUUID}..."
 259                                 // proxies to
 260                                 // "/log for container {cUUID}..."
 261                                 r.Header.Set("X-Webdav-Prefix", "/arvados/v1/container_requests/"+cr.UUID+"/log/"+opts.Path[1:28])
 262                                 r.Header.Set("X-Webdav-Source", "/log for container "+opts.Path[1:28]+"/")
 263                         }
 264                 },
 265         }
 266         if conn.cluster.TLS.Insecure {
 267                 proxy.Transport = &http.Transport{
 268                         TLSClientConfig: &tls.Config{
 269                                 InsecureSkipVerify: conn.cluster.TLS.Insecure,
 270                         },
 271                 }
 272         }
 273         proxy.ServeHTTP(w, r)
 274 }
 275
 276 // serveEmptyDir handles read-only webdav requests as if there was an
 277 // empty collection rooted at the given path. It's equivalent to
 278 // proxying to an empty collection in keep-web, but avoids the extra
 279 // hop.
 280 func (conn *Conn) serveEmptyDir(path string, w http.ResponseWriter, r *http.Request) {
 281         wh := webdav.Handler{
 282                 Prefix:     path,
 283                 FileSystem: webdav.NewMemFS(),
 284                 LockSystem: webdavfs.NoLockSystem,
 285                 Logger: func(r *http.Request, err error) {
 286                         if err != nil && !os.IsNotExist(err) {
 287                                 ctxlog.FromContext(r.Context()).WithError(err).Info("webdav error on empty collection fs")
 288                         }
 289                 },
 290         }
 291         wh.ServeHTTP(w, r)
 292 }
 293
 294 // ContainerSSH returns a connection to the SSH server in the
 295 // appropriate crunch-run process on the worker node where the
 296 // specified container is running.
 297 //
 298 // If the returned error is nil, the caller is responsible for closing
 299 // sshconn.Conn.
 300 func (conn *Conn) ContainerSSH(ctx context.Context, opts arvados.ContainerSSHOptions) (sshconn arvados.ConnectionResponse, err error) {
 301         user, err := conn.railsProxy.UserGetCurrent(ctx, arvados.GetOptions{})
 302         if err != nil {
 303                 return sshconn, err
 304         }
 305         ctr, err := conn.railsProxy.ContainerGet(ctx, arvados.GetOptions{UUID: opts.UUID, Select: []string{"uuid", "state", "gateway_address", "interactive_session_started"}})
 306         if err != nil {
 307                 return sshconn, err
 308         }
 309         ctxRoot := auth.NewContext(ctx, &auth.Credentials{Tokens: []string{conn.cluster.SystemRootToken}})
 310         if !user.IsAdmin || !conn.cluster.Containers.ShellAccess.Admin {
 311                 if !conn.cluster.Containers.ShellAccess.User {
 312                         return sshconn, httpserver.ErrorWithStatus(errors.New("shell access is disabled in config"), http.StatusServiceUnavailable)
 313                 }
 314                 crs, err := conn.railsProxy.ContainerRequestList(ctxRoot, arvados.ListOptions{Limit: -1, Filters: []arvados.Filter{{"container_uuid", "=", opts.UUID}}})
 315                 if err != nil {
 316                         return sshconn, err
 317                 }
 318                 for _, cr := range crs.Items {
 319                         if cr.ModifiedByUserUUID != user.UUID {
 320                                 return sshconn, httpserver.ErrorWithStatus(errors.New("permission denied: container is associated with requests submitted by other users"), http.StatusForbidden)
 321                         }
 322                 }
 323                 if crs.ItemsAvailable != len(crs.Items) {
 324                         return sshconn, httpserver.ErrorWithStatus(errors.New("incomplete response while checking permission"), http.StatusInternalServerError)
 325                 }
 326         }
 327
 328         if ctr.State == arvados.ContainerStateQueued || ctr.State == arvados.ContainerStateLocked {
 329                 return sshconn, httpserver.ErrorWithStatus(fmt.Errorf("container is not running yet (state is %q)", ctr.State), http.StatusServiceUnavailable)
 330         } else if ctr.State != arvados.ContainerStateRunning {
 331                 return sshconn, httpserver.ErrorWithStatus(fmt.Errorf("container has ended (state is %q)", ctr.State), http.StatusGone)
 332         }
 333
 334         dial, arpc, err := conn.findGateway(ctx, ctr, opts.NoForward)
 335         if err != nil {
 336                 return sshconn, err
 337         }
 338         if arpc != nil {
 339                 opts.NoForward = true
 340                 return arpc.ContainerSSH(ctx, opts)
 341         }
 342
 343         tlsconn, requestAuth, respondAuth, err := dial()
 344         if err != nil {
 345                 return sshconn, err
 346         }
 347         bufr := bufio.NewReader(tlsconn)
 348         bufw := bufio.NewWriter(tlsconn)
 349
 350         u := url.URL{
 351                 Scheme: "http",
 352                 Host:   tlsconn.RemoteAddr().String(),
 353                 Path:   "/ssh",
 354         }
 355         postform := url.Values{
 356                 // uuid is only needed for older crunch-run versions
 357                 // (current version uses X-Arvados-* header below)
 358                 "uuid":           {opts.UUID},
 359                 "detach_keys":    {opts.DetachKeys},
 360                 "login_username": {opts.LoginUsername},
 361                 "no_forward":     {fmt.Sprintf("%v", opts.NoForward)},
 362         }
 363         postdata := postform.Encode()
 364         bufw.WriteString("POST " + u.String() + " HTTP/1.1\r\n")
 365         bufw.WriteString("Host: " + u.Host + "\r\n")
 366         bufw.WriteString("Upgrade: ssh\r\n")
 367         bufw.WriteString("X-Arvados-Container-Gateway-Uuid: " + opts.UUID + "\r\n")
 368         bufw.WriteString("X-Arvados-Authorization: " + requestAuth + "\r\n")
 369         bufw.WriteString("Content-Type: application/x-www-form-urlencoded\r\n")
 370         fmt.Fprintf(bufw, "Content-Length: %d\r\n", len(postdata))
 371         bufw.WriteString("\r\n")
 372         bufw.WriteString(postdata)
 373         bufw.Flush()
 374         resp, err := http.ReadResponse(bufr, &http.Request{Method: "POST"})
 375         if err != nil {
 376                 tlsconn.Close()
 377                 return sshconn, httpserver.ErrorWithStatus(fmt.Errorf("error reading http response from gateway: %w", err), http.StatusBadGateway)
 378         }
 379         defer resp.Body.Close()
 380         if resp.StatusCode != http.StatusSwitchingProtocols {
 381                 body, _ := ioutil.ReadAll(io.LimitReader(resp.Body, 1000))
 382                 tlsconn.Close()
 383                 return sshconn, httpserver.ErrorWithStatus(fmt.Errorf("unexpected status %s %q", resp.Status, body), http.StatusBadGateway)
 384         }
 385         if strings.ToLower(resp.Header.Get("Upgrade")) != "ssh" ||
 386                 strings.ToLower(resp.Header.Get("Connection")) != "upgrade" {
 387                 tlsconn.Close()
 388                 return sshconn, httpserver.ErrorWithStatus(errors.New("bad upgrade"), http.StatusBadGateway)
 389         }
 390         if resp.Header.Get("X-Arvados-Authorization-Response") != respondAuth {
 391                 tlsconn.Close()
 392                 return sshconn, httpserver.ErrorWithStatus(errors.New("bad X-Arvados-Authorization-Response header"), http.StatusBadGateway)
 393         }
 394
 395         if !ctr.InteractiveSessionStarted {
 396                 _, err = conn.railsProxy.ContainerUpdate(ctxRoot, arvados.UpdateOptions{
 397                         UUID: opts.UUID,
 398                         Attrs: map[string]interface{}{
 399                                 "interactive_session_started": true,
 400                         },
 401                 })
 402                 if err != nil {
 403                         tlsconn.Close()
 404                         return sshconn, httpserver.ErrorWithStatus(err, http.StatusInternalServerError)
 405                 }
 406         }
 407
 408         sshconn.Conn = tlsconn
 409         sshconn.Bufrw = &bufio.ReadWriter{Reader: bufr, Writer: bufw}
 410         sshconn.Logger = ctxlog.FromContext(ctx)
 411         sshconn.Header = http.Header{"Upgrade": {"ssh"}}
 412         return sshconn, nil
 413 }
 414
 415 // ContainerGatewayTunnel sets up a tunnel enabling us (controller) to
 416 // connect to the caller's (crunch-run's) gateway server.
 417 func (conn *Conn) ContainerGatewayTunnel(ctx context.Context, opts arvados.ContainerGatewayTunnelOptions) (resp arvados.ConnectionResponse, err error) {
 418         h := hmac.New(sha256.New, []byte(conn.cluster.SystemRootToken))
 419         fmt.Fprint(h, opts.UUID)
 420         authSecret := fmt.Sprintf("%x", h.Sum(nil))
 421         if subtle.ConstantTimeCompare([]byte(authSecret), []byte(opts.AuthSecret)) != 1 {
 422                 ctxlog.FromContext(ctx).Info("received incorrect auth_secret")
 423                 return resp, httpserver.ErrorWithStatus(errors.New("authentication error"), http.StatusUnauthorized)
 424         }
 425
 426         muxconn, clientconn := net.Pipe()
 427         tunnel, err := yamux.Server(muxconn, nil)
 428         if err != nil {
 429                 clientconn.Close()
 430                 return resp, httpserver.ErrorWithStatus(err, http.StatusInternalServerError)
 431         }
 432
 433         conn.gwTunnelsLock.Lock()
 434         if conn.gwTunnels == nil {
 435                 conn.gwTunnels = map[string]*yamux.Session{opts.UUID: tunnel}
 436         } else {
 437                 conn.gwTunnels[opts.UUID] = tunnel
 438         }
 439         conn.gwTunnelsLock.Unlock()
 440
 441         go func() {
 442                 <-tunnel.CloseChan()
 443                 conn.gwTunnelsLock.Lock()
 444                 if conn.gwTunnels[opts.UUID] == tunnel {
 445                         delete(conn.gwTunnels, opts.UUID)
 446                 }
 447                 conn.gwTunnelsLock.Unlock()
 448         }()
 449
 450         // Assuming we're acting as the backend of an http server,
 451         // lib/controller/router will call resp's ServeHTTP handler,
 452         // which upgrades the incoming http connection to a raw socket
 453         // and connects it to our yamux.Server through our net.Pipe().
 454         resp.Conn = clientconn
 455         resp.Bufrw = &bufio.ReadWriter{Reader: bufio.NewReader(&bytes.Buffer{}), Writer: bufio.NewWriter(&bytes.Buffer{})}
 456         resp.Logger = ctxlog.FromContext(ctx)
 457         resp.Header = http.Header{"Upgrade": {"tunnel"}}
 458         if u, ok := service.URLFromContext(ctx); ok {
 459                 resp.Header.Set("X-Arvados-Internal-Url", u.String())
 460         } else if forceInternalURLForTest != nil {
 461                 resp.Header.Set("X-Arvados-Internal-Url", forceInternalURLForTest.String())
 462         }
 463         return
 464 }
 465
 466 type gatewayDialer func() (conn net.Conn, requestAuth, respondAuth string, err error)
 467
 468 // findGateway figures out how to connect to ctr's gateway.
 469 //
 470 // If the gateway can be contacted directly or through a tunnel on
 471 // this instance, the first return value is a non-nil dialer.
 472 //
 473 // If the gateway is only accessible through a tunnel through a
 474 // different controller process, the second return value is a non-nil
 475 // *rpc.Conn for that controller.
 476 func (conn *Conn) findGateway(ctx context.Context, ctr arvados.Container, noForward bool) (gatewayDialer, *rpc.Conn, error) {
 477         conn.gwTunnelsLock.Lock()
 478         tunnel := conn.gwTunnels[ctr.UUID]
 479         conn.gwTunnelsLock.Unlock()
 480
 481         myURL, _ := service.URLFromContext(ctx)
 482
 483         if host, _, splitErr := net.SplitHostPort(ctr.GatewayAddress); splitErr == nil && host != "" && host != "127.0.0.1" {
 484                 // If crunch-run provided a GatewayAddress like
 485                 // "ipaddr:port", that means "ipaddr" is one of the
 486                 // external interfaces where the gateway is
 487                 // listening. In that case, it's the most
 488                 // reliable/direct option, so we use it even if a
 489                 // tunnel might also be available.
 490                 return func() (net.Conn, string, string, error) {
 491                         rawconn, err := (&net.Dialer{}).DialContext(ctx, "tcp", ctr.GatewayAddress)
 492                         if err != nil {
 493                                 return nil, "", "", httpserver.ErrorWithStatus(err, http.StatusServiceUnavailable)
 494                         }
 495                         return conn.dialGatewayTLS(ctx, ctr, rawconn)
 496                 }, nil, nil
 497         }
 498         if tunnel != nil && !(forceProxyForTest && !noForward) {
 499                 // If we can't connect directly, and the gateway has
 500                 // established a yamux tunnel with us, connect through
 501                 // the tunnel.
 502                 //
 503                 // ...except: forceProxyForTest means we are emulating
 504                 // a situation where the gateway has established a
 505                 // yamux tunnel with controller B, and the
 506                 // ContainerSSH request arrives at controller A. If
 507                 // noForward==false then we are acting as A, so
 508                 // we pretend not to have a tunnel, and fall through
 509                 // to the "tunurl" case below. If noForward==true
 510                 // then the client is A and we are acting as B, so we
 511                 // connect to our tunnel.
 512                 return func() (net.Conn, string, string, error) {
 513                         rawconn, err := tunnel.Open()
 514                         if err != nil {
 515                                 return nil, "", "", httpserver.ErrorWithStatus(err, http.StatusServiceUnavailable)
 516                         }
 517                         return conn.dialGatewayTLS(ctx, ctr, rawconn)
 518                 }, nil, nil
 519         }
 520         if tunurl := strings.TrimPrefix(ctr.GatewayAddress, "tunnel "); tunurl != ctr.GatewayAddress &&
 521                 tunurl != "" &&
 522                 tunurl != myURL.String() &&
 523                 !noForward {
 524                 // If crunch-run provided a GatewayAddress like
 525                 // "tunnel https://10.0.0.10:1010/", that means the
 526                 // gateway has established a yamux tunnel with the
 527                 // controller process at the indicated InternalURL
 528                 // (which isn't us, otherwise we would have had
 529                 // "tunnel != nil" above). We need to proxy through to
 530                 // the other controller process in order to use the
 531                 // tunnel.
 532                 for u := range conn.cluster.Services.Controller.InternalURLs {
 533                         if u.String() == tunurl {
 534                                 ctxlog.FromContext(ctx).Debugf("connecting to container gateway through other controller at %s", u)
 535                                 u := url.URL(u)
 536                                 return nil, rpc.NewConn(conn.cluster.ClusterID, &u, conn.cluster.TLS.Insecure, rpc.PassthroughTokenProvider), nil
 537                         }
 538                 }
 539                 ctxlog.FromContext(ctx).Warnf("container gateway provided a tunnel endpoint %s that is not one of Services.Controller.InternalURLs", tunurl)
 540                 return nil, nil, httpserver.ErrorWithStatus(errors.New("container gateway is running but tunnel endpoint is invalid"), http.StatusServiceUnavailable)
 541         }
 542         if ctr.GatewayAddress == "" {
 543                 return nil, nil, httpserver.ErrorWithStatus(errors.New("container is running but gateway is not available"), http.StatusServiceUnavailable)
 544         } else {
 545                 return nil, nil, httpserver.ErrorWithStatus(errors.New("container is running but tunnel is down"), http.StatusServiceUnavailable)
 546         }
 547 }
 548
 549 // dialGatewayTLS negotiates a TLS connection to a container gateway
 550 // over the given raw connection.
 551 func (conn *Conn) dialGatewayTLS(ctx context.Context, ctr arvados.Container, rawconn net.Conn) (*tls.Conn, string, string, error) {
 552         // crunch-run uses a self-signed / unverifiable TLS
 553         // certificate, so we use the following scheme to ensure we're
 554         // not talking to an attacker-in-the-middle.
 555         //
 556         // 1. Compute ctrKey = HMAC-SHA256(sysRootToken,ctrUUID) --
 557         // this will be the same ctrKey that a-d-c supplied to
 558         // crunch-run in the GatewayAuthSecret env var.
 559         //
 560         // 2. Compute requestAuth = HMAC-SHA256(ctrKey,serverCert) and
 561         // send it to crunch-run as the X-Arvados-Authorization
 562         // header, proving that we know ctrKey. (Note a MITM cannot
 563         // replay the proof to a real crunch-run server, because the
 564         // real crunch-run server would have a different cert.)
 565         //
 566         // 3. Compute respondAuth = HMAC-SHA256(ctrKey,requestAuth)
 567         // and ensure the server returns it in the
 568         // X-Arvados-Authorization-Response header, proving that the
 569         // server knows ctrKey.
 570         var requestAuth, respondAuth string
 571         tlsconn := tls.Client(rawconn, &tls.Config{
 572                 InsecureSkipVerify: true,
 573                 VerifyPeerCertificate: func(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error {
 574                         if len(rawCerts) == 0 {
 575                                 return errors.New("no certificate received, cannot compute authorization header")
 576                         }
 577                         h := hmac.New(sha256.New, []byte(conn.cluster.SystemRootToken))
 578                         fmt.Fprint(h, ctr.UUID)
 579                         authKey := fmt.Sprintf("%x", h.Sum(nil))
 580                         h = hmac.New(sha256.New, []byte(authKey))
 581                         h.Write(rawCerts[0])
 582                         requestAuth = fmt.Sprintf("%x", h.Sum(nil))
 583                         h.Reset()
 584                         h.Write([]byte(requestAuth))
 585                         respondAuth = fmt.Sprintf("%x", h.Sum(nil))
 586                         return nil
 587                 },
 588         })
 589         err := tlsconn.HandshakeContext(ctx)
 590         if err != nil {
 591                 return nil, "", "", httpserver.ErrorWithStatus(fmt.Errorf("TLS handshake failed: %w", err), http.StatusBadGateway)
 592         }
 593         if respondAuth == "" {
 594                 tlsconn.Close()
 595                 return nil, "", "", httpserver.ErrorWithStatus(errors.New("BUG: no respondAuth"), http.StatusInternalServerError)
 596         }
 597         return tlsconn, requestAuth, respondAuth, nil
 598 }