services/keep-web/handler.go

   1 // Copyright (C) The Arvados Authors. All rights reserved.
   2 //
   3 // SPDX-License-Identifier: AGPL-3.0
   4
   5 package main
   6
   7 import (
   8         "encoding/json"
   9         "fmt"
  10         "html"
  11         "html/template"
  12         "io"
  13         "net/http"
  14         "net/url"
  15         "os"
  16         "path/filepath"
  17         "sort"
  18         "strconv"
  19         "strings"
  20         "sync"
  21
  22         "git.arvados.org/arvados.git/sdk/go/arvados"
  23         "git.arvados.org/arvados.git/sdk/go/arvadosclient"
  24         "git.arvados.org/arvados.git/sdk/go/auth"
  25         "git.arvados.org/arvados.git/sdk/go/ctxlog"
  26         "git.arvados.org/arvados.git/sdk/go/health"
  27         "git.arvados.org/arvados.git/sdk/go/httpserver"
  28         "git.arvados.org/arvados.git/sdk/go/keepclient"
  29         "github.com/sirupsen/logrus"
  30         "golang.org/x/net/webdav"
  31 )
  32
  33 type handler struct {
  34         Config        *Config
  35         MetricsAPI    http.Handler
  36         clientPool    *arvadosclient.ClientPool
  37         setupOnce     sync.Once
  38         healthHandler http.Handler
  39         webdavLS      webdav.LockSystem
  40 }
  41
  42 // parseCollectionIDFromDNSName returns a UUID or PDH if s begins with
  43 // a UUID or URL-encoded PDH; otherwise "".
  44 func parseCollectionIDFromDNSName(s string) string {
  45         // Strip domain.
  46         if i := strings.IndexRune(s, '.'); i >= 0 {
  47                 s = s[:i]
  48         }
  49         // Names like {uuid}--collections.example.com serve the same
  50         // purpose as {uuid}.collections.example.com but can reduce
  51         // cost/effort of using [additional] wildcard certificates.
  52         if i := strings.Index(s, "--"); i >= 0 {
  53                 s = s[:i]
  54         }
  55         if arvadosclient.UUIDMatch(s) {
  56                 return s
  57         }
  58         if pdh := strings.Replace(s, "-", "+", 1); arvadosclient.PDHMatch(pdh) {
  59                 return pdh
  60         }
  61         return ""
  62 }
  63
  64 var urlPDHDecoder = strings.NewReplacer(" ", "+", "-", "+")
  65
  66 var notFoundMessage = "404 Not found\r\n\r\nThe requested path was not found, or you do not have permission to access it.\r"
  67 var unauthorizedMessage = "401 Unauthorized\r\n\r\nA valid Arvados token must be provided to access this resource.\r"
  68
  69 // parseCollectionIDFromURL returns a UUID or PDH if s is a UUID or a
  70 // PDH (even if it is a PDH with "+" replaced by " " or "-");
  71 // otherwise "".
  72 func parseCollectionIDFromURL(s string) string {
  73         if arvadosclient.UUIDMatch(s) {
  74                 return s
  75         }
  76         if pdh := urlPDHDecoder.Replace(s); arvadosclient.PDHMatch(pdh) {
  77                 return pdh
  78         }
  79         return ""
  80 }
  81
  82 func (h *handler) setup() {
  83         // Errors will be handled at the client pool.
  84         arv, _ := arvados.NewClientFromConfig(h.Config.cluster)
  85         h.clientPool = arvadosclient.MakeClientPoolWith(arv)
  86
  87         keepclient.RefreshServiceDiscoveryOnSIGHUP()
  88         keepclient.DefaultBlockCache.MaxBlocks = h.Config.cluster.Collections.WebDAVCache.MaxBlockEntries
  89
  90         h.healthHandler = &health.Handler{
  91                 Token:  h.Config.cluster.ManagementToken,
  92                 Prefix: "/_health/",
  93         }
  94
  95         // Even though we don't accept LOCK requests, every webdav
  96         // handler must have a non-nil LockSystem.
  97         h.webdavLS = &noLockSystem{}
  98 }
  99
 100 func (h *handler) serveStatus(w http.ResponseWriter, r *http.Request) {
 101         json.NewEncoder(w).Encode(struct{ Version string }{version})
 102 }
 103
 104 // updateOnSuccess wraps httpserver.ResponseWriter. If the handler
 105 // sends an HTTP header indicating success, updateOnSuccess first
 106 // calls the provided update func. If the update func fails, a 500
 107 // response is sent, and the status code and body sent by the handler
 108 // are ignored (all response writes return the update error).
 109 type updateOnSuccess struct {
 110         httpserver.ResponseWriter
 111         logger     logrus.FieldLogger
 112         update     func() error
 113         sentHeader bool
 114         err        error
 115 }
 116
 117 func (uos *updateOnSuccess) Write(p []byte) (int, error) {
 118         if !uos.sentHeader {
 119                 uos.WriteHeader(http.StatusOK)
 120         }
 121         if uos.err != nil {
 122                 return 0, uos.err
 123         }
 124         return uos.ResponseWriter.Write(p)
 125 }
 126
 127 func (uos *updateOnSuccess) WriteHeader(code int) {
 128         if !uos.sentHeader {
 129                 uos.sentHeader = true
 130                 if code >= 200 && code < 400 {
 131                         if uos.err = uos.update(); uos.err != nil {
 132                                 code := http.StatusInternalServerError
 133                                 if err, ok := uos.err.(*arvados.TransactionError); ok {
 134                                         code = err.StatusCode
 135                                 }
 136                                 uos.logger.WithError(uos.err).Errorf("update() returned error type %T, changing response to HTTP %d", uos.err, code)
 137                                 http.Error(uos.ResponseWriter, uos.err.Error(), code)
 138                                 return
 139                         }
 140                 }
 141         }
 142         uos.ResponseWriter.WriteHeader(code)
 143 }
 144
 145 var (
 146         corsAllowHeadersHeader = strings.Join([]string{
 147                 "Authorization", "Content-Type", "Range",
 148                 // WebDAV request headers:
 149                 "Depth", "Destination", "If", "Lock-Token", "Overwrite", "Timeout",
 150         }, ", ")
 151         writeMethod = map[string]bool{
 152                 "COPY":      true,
 153                 "DELETE":    true,
 154                 "LOCK":      true,
 155                 "MKCOL":     true,
 156                 "MOVE":      true,
 157                 "PROPPATCH": true,
 158                 "PUT":       true,
 159                 "RMCOL":     true,
 160                 "UNLOCK":    true,
 161         }
 162         webdavMethod = map[string]bool{
 163                 "COPY":      true,
 164                 "DELETE":    true,
 165                 "LOCK":      true,
 166                 "MKCOL":     true,
 167                 "MOVE":      true,
 168                 "OPTIONS":   true,
 169                 "PROPFIND":  true,
 170                 "PROPPATCH": true,
 171                 "PUT":       true,
 172                 "RMCOL":     true,
 173                 "UNLOCK":    true,
 174         }
 175         browserMethod = map[string]bool{
 176                 "GET":  true,
 177                 "HEAD": true,
 178                 "POST": true,
 179         }
 180         // top-level dirs to serve with siteFS
 181         siteFSDir = map[string]bool{
 182                 "":      true, // root directory
 183                 "by_id": true,
 184                 "users": true,
 185         }
 186 )
 187
 188 func StripDefaultPort(host string) string {
 189         // Will consider port 80 and port 443 to be the same vhost.  I think that's fine.
 190         if strings.HasSuffix(host, ":80") || strings.HasSuffix(host, ":443") {
 191                 return host[0:strings.Index(host, ":")]
 192         }
 193         return host
 194 }
 195
 196 // ServeHTTP implements http.Handler.
 197 func (h *handler) ServeHTTP(wOrig http.ResponseWriter, r *http.Request) {
 198         h.setupOnce.Do(h.setup)
 199
 200         if xfp := r.Header.Get("X-Forwarded-Proto"); xfp != "" && xfp != "http" {
 201                 r.URL.Scheme = xfp
 202         }
 203
 204         w := httpserver.WrapResponseWriter(wOrig)
 205
 206         if strings.HasPrefix(r.URL.Path, "/_health/") && r.Method == "GET" {
 207                 h.healthHandler.ServeHTTP(w, r)
 208                 return
 209         }
 210
 211         if method := r.Header.Get("Access-Control-Request-Method"); method != "" && r.Method == "OPTIONS" {
 212                 if !browserMethod[method] && !webdavMethod[method] {
 213                         w.WriteHeader(http.StatusMethodNotAllowed)
 214                         return
 215                 }
 216                 w.Header().Set("Access-Control-Allow-Headers", corsAllowHeadersHeader)
 217                 w.Header().Set("Access-Control-Allow-Methods", "COPY, DELETE, GET, LOCK, MKCOL, MOVE, OPTIONS, POST, PROPFIND, PROPPATCH, PUT, RMCOL, UNLOCK")
 218                 w.Header().Set("Access-Control-Allow-Origin", "*")
 219                 w.Header().Set("Access-Control-Max-Age", "86400")
 220                 return
 221         }
 222
 223         if !browserMethod[r.Method] && !webdavMethod[r.Method] {
 224                 w.WriteHeader(http.StatusMethodNotAllowed)
 225                 return
 226         }
 227
 228         if r.Header.Get("Origin") != "" {
 229                 // Allow simple cross-origin requests without user
 230                 // credentials ("user credentials" as defined by CORS,
 231                 // i.e., cookies, HTTP authentication, and client-side
 232                 // SSL certificates. See
 233                 // http://www.w3.org/TR/cors/#user-credentials).
 234                 w.Header().Set("Access-Control-Allow-Origin", "*")
 235                 w.Header().Set("Access-Control-Expose-Headers", "Content-Range")
 236         }
 237
 238         if h.serveS3(w, r) {
 239                 return
 240         }
 241
 242         pathParts := strings.Split(r.URL.Path[1:], "/")
 243
 244         var stripParts int
 245         var collectionID string
 246         var tokens []string
 247         var reqTokens []string
 248         var pathToken bool
 249         var attachment bool
 250         var useSiteFS bool
 251         credentialsOK := h.Config.cluster.Collections.TrustAllContent
 252         reasonNotAcceptingCredentials := ""
 253
 254         if r.Host != "" && StripDefaultPort(r.Host) == StripDefaultPort(h.Config.cluster.Services.WebDAVDownload.ExternalURL.Host) {
 255                 credentialsOK = true
 256                 attachment = true
 257         } else if r.FormValue("disposition") == "attachment" {
 258                 attachment = true
 259         }
 260
 261         if !credentialsOK {
 262                 reasonNotAcceptingCredentials = fmt.Sprintf("Collections.TrustAllContent is false and provided virtual host '%s' did not match either Services.WebDAV or Services.WebDAVDownload", r.Host)
 263         }
 264
 265         if collectionID = parseCollectionIDFromDNSName(r.Host); collectionID != "" {
 266                 // http://ID.collections.example/PATH...
 267                 credentialsOK = true
 268         } else if r.URL.Path == "/status.json" {
 269                 h.serveStatus(w, r)
 270                 return
 271         } else if strings.HasPrefix(r.URL.Path, "/metrics") {
 272                 h.MetricsAPI.ServeHTTP(w, r)
 273                 return
 274         } else if siteFSDir[pathParts[0]] {
 275                 useSiteFS = true
 276         } else if len(pathParts) >= 1 && strings.HasPrefix(pathParts[0], "c=") {
 277                 // /c=ID[/PATH...]
 278                 collectionID = parseCollectionIDFromURL(pathParts[0][2:])
 279                 stripParts = 1
 280         } else if len(pathParts) >= 2 && pathParts[0] == "collections" {
 281                 if len(pathParts) >= 4 && pathParts[1] == "download" {
 282                         // /collections/download/ID/TOKEN/PATH...
 283                         collectionID = parseCollectionIDFromURL(pathParts[2])
 284                         tokens = []string{pathParts[3]}
 285                         stripParts = 4
 286                         pathToken = true
 287                 } else {
 288                         // /collections/ID/PATH...
 289                         collectionID = parseCollectionIDFromURL(pathParts[1])
 290                         stripParts = 2
 291                         // This path is only meant to work for public
 292                         // data. Tokens provided with the request are
 293                         // ignored.
 294                         credentialsOK = false
 295                         reasonNotAcceptingCredentials = "the '/collections/UUID/PATH' form only works for public data"
 296                 }
 297         }
 298
 299         if collectionID == "" && !useSiteFS {
 300                 http.Error(w, notFoundMessage, http.StatusNotFound)
 301                 return
 302         }
 303
 304         forceReload := false
 305         if cc := r.Header.Get("Cache-Control"); strings.Contains(cc, "no-cache") || strings.Contains(cc, "must-revalidate") {
 306                 forceReload = true
 307         }
 308
 309         if credentialsOK {
 310                 reqTokens = auth.CredentialsFromRequest(r).Tokens
 311         }
 312
 313         formToken := r.FormValue("api_token")
 314         origin := r.Header.Get("Origin")
 315         cors := origin != "" && !strings.HasSuffix(origin, "://"+r.Host)
 316         safeAjax := cors && (r.Method == http.MethodGet || r.Method == http.MethodHead)
 317         safeAttachment := attachment && r.URL.Query().Get("api_token") == ""
 318         if formToken == "" {
 319                 // No token to use or redact.
 320         } else if safeAjax || safeAttachment {
 321                 // If this is a cross-origin request, the URL won't
 322                 // appear in the browser's address bar, so
 323                 // substituting a clipboard-safe URL is pointless.
 324                 // Redirect-with-cookie wouldn't work anyway, because
 325                 // it's not safe to allow third-party use of our
 326                 // cookie.
 327                 //
 328                 // If we're supplying an attachment, we don't need to
 329                 // convert POST to GET to avoid the "really resubmit
 330                 // form?" problem, so provided the token isn't
 331                 // embedded in the URL, there's no reason to do
 332                 // redirect-with-cookie in this case either.
 333                 reqTokens = append(reqTokens, formToken)
 334         } else if browserMethod[r.Method] {
 335                 // If this is a page view, and the client provided a
 336                 // token via query string or POST body, we must put
 337                 // the token in an HttpOnly cookie, and redirect to an
 338                 // equivalent URL with the query param redacted and
 339                 // method = GET.
 340                 h.seeOtherWithCookie(w, r, "", credentialsOK)
 341                 return
 342         }
 343
 344         if useSiteFS {
 345                 h.serveSiteFS(w, r, reqTokens, credentialsOK, attachment)
 346                 return
 347         }
 348
 349         targetPath := pathParts[stripParts:]
 350         if tokens == nil && len(targetPath) > 0 && strings.HasPrefix(targetPath[0], "t=") {
 351                 // http://ID.example/t=TOKEN/PATH...
 352                 // /c=ID/t=TOKEN/PATH...
 353                 //
 354                 // This form must only be used to pass scoped tokens
 355                 // that give permission for a single collection. See
 356                 // FormValue case above.
 357                 tokens = []string{targetPath[0][2:]}
 358                 pathToken = true
 359                 targetPath = targetPath[1:]
 360                 stripParts++
 361         }
 362
 363         if tokens == nil {
 364                 tokens = reqTokens
 365                 if h.Config.cluster.Users.AnonymousUserToken != "" {
 366                         tokens = append(tokens, h.Config.cluster.Users.AnonymousUserToken)
 367                 }
 368         }
 369
 370         if tokens == nil {
 371                 if !credentialsOK {
 372                         http.Error(w, fmt.Sprintf("Authorization tokens were not accepted because %v, and no anonymous user token is configured.", reasonNotAcceptingCredentials), http.StatusUnauthorized)
 373                 } else {
 374                         http.Error(w, fmt.Sprintf("No authorization token in request, and no anonymous user token is configured."), http.StatusUnauthorized)
 375                 }
 376                 return
 377         }
 378
 379         if len(targetPath) > 0 && targetPath[0] == "_" {
 380                 // If a collection has a directory called "t=foo" or
 381                 // "_", it can be served at
 382                 // //collections.example/_/t=foo/ or
 383                 // //collections.example/_/_/ respectively:
 384                 // //collections.example/t=foo/ won't work because
 385                 // t=foo will be interpreted as a token "foo".
 386                 targetPath = targetPath[1:]
 387                 stripParts++
 388         }
 389
 390         arv := h.clientPool.Get()
 391         if arv == nil {
 392                 http.Error(w, "client pool error: "+h.clientPool.Err().Error(), http.StatusInternalServerError)
 393                 return
 394         }
 395         defer h.clientPool.Put(arv)
 396
 397         var collection *arvados.Collection
 398         tokenResult := make(map[string]int)
 399         for _, arv.ApiToken = range tokens {
 400                 var err error
 401                 collection, err = h.Config.Cache.Get(arv, collectionID, forceReload)
 402                 if err == nil {
 403                         // Success
 404                         break
 405                 }
 406                 if srvErr, ok := err.(arvadosclient.APIServerError); ok {
 407                         switch srvErr.HttpStatusCode {
 408                         case 404, 401:
 409                                 // Token broken or insufficient to
 410                                 // retrieve collection
 411                                 tokenResult[arv.ApiToken] = srvErr.HttpStatusCode
 412                                 continue
 413                         }
 414                 }
 415                 // Something more serious is wrong
 416                 http.Error(w, "cache error: "+err.Error(), http.StatusInternalServerError)
 417                 return
 418         }
 419         if collection == nil {
 420                 if pathToken || !credentialsOK {
 421                         // Either the URL is a "secret sharing link"
 422                         // that didn't work out (and asking the client
 423                         // for additional credentials would just be
 424                         // confusing), or we don't even accept
 425                         // credentials at this path.
 426                         http.Error(w, notFoundMessage, http.StatusNotFound)
 427                         return
 428                 }
 429                 for _, t := range reqTokens {
 430                         if tokenResult[t] == 404 {
 431                                 // The client provided valid token(s), but the
 432                                 // collection was not found.
 433                                 http.Error(w, notFoundMessage, http.StatusNotFound)
 434                                 return
 435                         }
 436                 }
 437                 // The client's token was invalid (e.g., expired), or
 438                 // the client didn't even provide one.  Propagate the
 439                 // 401 to encourage the client to use a [different]
 440                 // token.
 441                 //
 442                 // TODO(TC): This response would be confusing to
 443                 // someone trying (anonymously) to download public
 444                 // data that has been deleted.  Allow a referrer to
 445                 // provide this context somehow?
 446                 w.Header().Add("WWW-Authenticate", "Basic realm=\"collections\"")
 447                 http.Error(w, unauthorizedMessage, http.StatusUnauthorized)
 448                 return
 449         }
 450
 451         kc, err := keepclient.MakeKeepClient(arv)
 452         if err != nil {
 453                 http.Error(w, "error setting up keep client: "+err.Error(), http.StatusInternalServerError)
 454                 return
 455         }
 456         kc.RequestID = r.Header.Get("X-Request-Id")
 457
 458         var basename string
 459         if len(targetPath) > 0 {
 460                 basename = targetPath[len(targetPath)-1]
 461         }
 462         applyContentDispositionHdr(w, r, basename, attachment)
 463
 464         client := (&arvados.Client{
 465                 APIHost:   arv.ApiServer,
 466                 AuthToken: arv.ApiToken,
 467                 Insecure:  arv.ApiInsecure,
 468         }).WithRequestID(r.Header.Get("X-Request-Id"))
 469
 470         fs, err := collection.FileSystem(client, kc)
 471         if err != nil {
 472                 http.Error(w, "error creating collection filesystem: "+err.Error(), http.StatusInternalServerError)
 473                 return
 474         }
 475
 476         writefs, writeOK := fs.(arvados.CollectionFileSystem)
 477         targetIsPDH := arvadosclient.PDHMatch(collectionID)
 478         if (targetIsPDH || !writeOK) && writeMethod[r.Method] {
 479                 http.Error(w, errReadOnly.Error(), http.StatusMethodNotAllowed)
 480                 return
 481         }
 482
 483         if webdavMethod[r.Method] {
 484                 if writeMethod[r.Method] {
 485                         // Save the collection only if/when all
 486                         // webdav->filesystem operations succeed --
 487                         // and send a 500 error if the modified
 488                         // collection can't be saved.
 489                         w = &updateOnSuccess{
 490                                 ResponseWriter: w,
 491                                 logger:         ctxlog.FromContext(r.Context()),
 492                                 update: func() error {
 493                                         return h.Config.Cache.Update(client, *collection, writefs)
 494                                 }}
 495                 }
 496                 h := webdav.Handler{
 497                         Prefix: "/" + strings.Join(pathParts[:stripParts], "/"),
 498                         FileSystem: &webdavFS{
 499                                 collfs:        fs,
 500                                 writing:       writeMethod[r.Method],
 501                                 alwaysReadEOF: r.Method == "PROPFIND",
 502                         },
 503                         LockSystem: h.webdavLS,
 504                         Logger: func(_ *http.Request, err error) {
 505                                 if err != nil {
 506                                         ctxlog.FromContext(r.Context()).WithError(err).Error("error reported by webdav handler")
 507                                 }
 508                         },
 509                 }
 510                 h.ServeHTTP(w, r)
 511                 return
 512         }
 513
 514         openPath := "/" + strings.Join(targetPath, "/")
 515         f, err := fs.Open(openPath)
 516         if os.IsNotExist(err) {
 517                 // Requested non-existent path
 518                 http.Error(w, notFoundMessage, http.StatusNotFound)
 519                 return
 520         } else if err != nil {
 521                 // Some other (unexpected) error
 522                 http.Error(w, "open: "+err.Error(), http.StatusInternalServerError)
 523                 return
 524         }
 525         defer f.Close()
 526         if stat, err := f.Stat(); err != nil {
 527                 // Can't get Size/IsDir (shouldn't happen with a collectionFS!)
 528                 http.Error(w, "stat: "+err.Error(), http.StatusInternalServerError)
 529         } else if stat.IsDir() && !strings.HasSuffix(r.URL.Path, "/") {
 530                 // If client requests ".../dirname", redirect to
 531                 // ".../dirname/". This way, relative links in the
 532                 // listing for "dirname" can always be "fnm", never
 533                 // "dirname/fnm".
 534                 h.seeOtherWithCookie(w, r, r.URL.Path+"/", credentialsOK)
 535         } else if stat.IsDir() {
 536                 h.serveDirectory(w, r, collection.Name, fs, openPath, true)
 537         } else {
 538                 http.ServeContent(w, r, basename, stat.ModTime(), f)
 539                 if wrote := int64(w.WroteBodyBytes()); wrote != stat.Size() && w.WroteStatus() == http.StatusOK {
 540                         // If we wrote fewer bytes than expected, it's
 541                         // too late to change the real response code
 542                         // or send an error message to the client, but
 543                         // at least we can try to put some useful
 544                         // debugging info in the logs.
 545                         n, err := f.Read(make([]byte, 1024))
 546                         ctxlog.FromContext(r.Context()).Errorf("stat.Size()==%d but only wrote %d bytes; read(1024) returns %d, %v", stat.Size(), wrote, n, err)
 547                 }
 548         }
 549 }
 550
 551 func (h *handler) getClients(reqID, token string) (arv *arvadosclient.ArvadosClient, kc *keepclient.KeepClient, client *arvados.Client, release func(), err error) {
 552         arv = h.clientPool.Get()
 553         if arv == nil {
 554                 err = h.clientPool.Err()
 555                 return
 556         }
 557         release = func() { h.clientPool.Put(arv) }
 558         arv.ApiToken = token
 559         kc, err = keepclient.MakeKeepClient(arv)
 560         if err != nil {
 561                 release()
 562                 return
 563         }
 564         kc.RequestID = reqID
 565         client = (&arvados.Client{
 566                 APIHost:   arv.ApiServer,
 567                 AuthToken: arv.ApiToken,
 568                 Insecure:  arv.ApiInsecure,
 569         }).WithRequestID(reqID)
 570         return
 571 }
 572
 573 func (h *handler) serveSiteFS(w http.ResponseWriter, r *http.Request, tokens []string, credentialsOK, attachment bool) {
 574         if len(tokens) == 0 {
 575                 w.Header().Add("WWW-Authenticate", "Basic realm=\"collections\"")
 576                 http.Error(w, unauthorizedMessage, http.StatusUnauthorized)
 577                 return
 578         }
 579         if writeMethod[r.Method] {
 580                 http.Error(w, errReadOnly.Error(), http.StatusMethodNotAllowed)
 581                 return
 582         }
 583         fs, err := h.Config.Cache.GetSession(tokens[0])
 584         if err != nil {
 585                 http.Error(w, err.Error(), http.StatusInternalServerError)
 586                 return
 587         }
 588         fs.ForwardSlashNameSubstitution(h.Config.cluster.Collections.ForwardSlashNameSubstitution)
 589         f, err := fs.Open(r.URL.Path)
 590         if os.IsNotExist(err) {
 591                 http.Error(w, err.Error(), http.StatusNotFound)
 592                 return
 593         } else if err != nil {
 594                 http.Error(w, err.Error(), http.StatusInternalServerError)
 595                 return
 596         }
 597         defer f.Close()
 598         if fi, err := f.Stat(); err == nil && fi.IsDir() && r.Method == "GET" {
 599                 if !strings.HasSuffix(r.URL.Path, "/") {
 600                         h.seeOtherWithCookie(w, r, r.URL.Path+"/", credentialsOK)
 601                 } else {
 602                         h.serveDirectory(w, r, fi.Name(), fs, r.URL.Path, false)
 603                 }
 604                 return
 605         }
 606         if r.Method == "GET" {
 607                 _, basename := filepath.Split(r.URL.Path)
 608                 applyContentDispositionHdr(w, r, basename, attachment)
 609         }
 610         wh := webdav.Handler{
 611                 Prefix: "/",
 612                 FileSystem: &webdavFS{
 613                         collfs:        fs,
 614                         writing:       writeMethod[r.Method],
 615                         alwaysReadEOF: r.Method == "PROPFIND",
 616                 },
 617                 LockSystem: h.webdavLS,
 618                 Logger: func(_ *http.Request, err error) {
 619                         if err != nil {
 620                                 ctxlog.FromContext(r.Context()).WithError(err).Error("error reported by webdav handler")
 621                         }
 622                 },
 623         }
 624         wh.ServeHTTP(w, r)
 625 }
 626
 627 var dirListingTemplate = `<!DOCTYPE HTML>
 628 <HTML><HEAD>
 629   <META name="robots" content="NOINDEX">
 630   <TITLE>{{ .CollectionName }}</TITLE>
 631   <STYLE type="text/css">
 632     body {
 633       margin: 1.5em;
 634     }
 635     pre {
 636       background-color: #D9EDF7;
 637       border-radius: .25em;
 638       padding: .75em;
 639       overflow: auto;
 640     }
 641     .footer p {
 642       font-size: 82%;
 643     }
 644     ul {
 645       padding: 0;
 646     }
 647     ul li {
 648       font-family: monospace;
 649       list-style: none;
 650     }
 651   </STYLE>
 652 </HEAD>
 653 <BODY>
 654
 655 <H1>{{ .CollectionName }}</H1>
 656
 657 <P>This collection of data files is being shared with you through
 658 Arvados.  You can download individual files listed below.  To download
 659 the entire directory tree with wget, try:</P>
 660
 661 <PRE>$ wget --mirror --no-parent --no-host --cut-dirs={{ .StripParts }} https://{{ .Request.Host }}{{ .Request.URL.Path }}</PRE>
 662
 663 <H2>File Listing</H2>
 664
 665 {{if .Files}}
 666 <UL>
 667 {{range .Files}}
 668 {{if .IsDir }}
 669   <LI>{{" " | printf "%15s  " | nbsp}}<A href="{{print "./" .Name}}/">{{.Name}}/</A></LI>
 670 {{else}}
 671   <LI>{{.Size | printf "%15d  " | nbsp}}<A href="{{print "./" .Name}}">{{.Name}}</A></LI>
 672 {{end}}
 673 {{end}}
 674 </UL>
 675 {{else}}
 676 <P>(No files; this collection is empty.)</P>
 677 {{end}}
 678
 679 <HR noshade>
 680 <DIV class="footer">
 681   <P>
 682     About Arvados:
 683     Arvados is a free and open source software bioinformatics platform.
 684     To learn more, visit arvados.org.
 685     Arvados is not responsible for the files listed on this page.
 686   </P>
 687 </DIV>
 688
 689 </BODY>
 690 `
 691
 692 type fileListEnt struct {
 693         Name  string
 694         Size  int64
 695         IsDir bool
 696 }
 697
 698 func (h *handler) serveDirectory(w http.ResponseWriter, r *http.Request, collectionName string, fs http.FileSystem, base string, recurse bool) {
 699         var files []fileListEnt
 700         var walk func(string) error
 701         if !strings.HasSuffix(base, "/") {
 702                 base = base + "/"
 703         }
 704         walk = func(path string) error {
 705                 dirname := base + path
 706                 if dirname != "/" {
 707                         dirname = strings.TrimSuffix(dirname, "/")
 708                 }
 709                 d, err := fs.Open(dirname)
 710                 if err != nil {
 711                         return err
 712                 }
 713                 ents, err := d.Readdir(-1)
 714                 if err != nil {
 715                         return err
 716                 }
 717                 for _, ent := range ents {
 718                         if recurse && ent.IsDir() {
 719                                 err = walk(path + ent.Name() + "/")
 720                                 if err != nil {
 721                                         return err
 722                                 }
 723                         } else {
 724                                 files = append(files, fileListEnt{
 725                                         Name:  path + ent.Name(),
 726                                         Size:  ent.Size(),
 727                                         IsDir: ent.IsDir(),
 728                                 })
 729                         }
 730                 }
 731                 return nil
 732         }
 733         if err := walk(""); err != nil {
 734                 http.Error(w, "error getting directory listing: "+err.Error(), http.StatusInternalServerError)
 735                 return
 736         }
 737
 738         funcs := template.FuncMap{
 739                 "nbsp": func(s string) template.HTML {
 740                         return template.HTML(strings.Replace(s, " ", "&nbsp;", -1))
 741                 },
 742         }
 743         tmpl, err := template.New("dir").Funcs(funcs).Parse(dirListingTemplate)
 744         if err != nil {
 745                 http.Error(w, "error parsing template: "+err.Error(), http.StatusInternalServerError)
 746                 return
 747         }
 748         sort.Slice(files, func(i, j int) bool {
 749                 return files[i].Name < files[j].Name
 750         })
 751         w.WriteHeader(http.StatusOK)
 752         tmpl.Execute(w, map[string]interface{}{
 753                 "CollectionName": collectionName,
 754                 "Files":          files,
 755                 "Request":        r,
 756                 "StripParts":     strings.Count(strings.TrimRight(r.URL.Path, "/"), "/"),
 757         })
 758 }
 759
 760 func applyContentDispositionHdr(w http.ResponseWriter, r *http.Request, filename string, isAttachment bool) {
 761         disposition := "inline"
 762         if isAttachment {
 763                 disposition = "attachment"
 764         }
 765         if strings.ContainsRune(r.RequestURI, '?') {
 766                 // Help the UA realize that the filename is just
 767                 // "filename.txt", not
 768                 // "filename.txt?disposition=attachment".
 769                 //
 770                 // TODO(TC): Follow advice at RFC 6266 appendix D
 771                 disposition += "; filename=" + strconv.QuoteToASCII(filename)
 772         }
 773         if disposition != "inline" {
 774                 w.Header().Set("Content-Disposition", disposition)
 775         }
 776 }
 777
 778 func (h *handler) seeOtherWithCookie(w http.ResponseWriter, r *http.Request, location string, credentialsOK bool) {
 779         if formToken := r.FormValue("api_token"); formToken != "" {
 780                 if !credentialsOK {
 781                         // It is not safe to copy the provided token
 782                         // into a cookie unless the current vhost
 783                         // (origin) serves only a single collection or
 784                         // we are in TrustAllContent mode.
 785                         http.Error(w, "cannot serve inline content at this URL (possible configuration error; see https://doc.arvados.org/install/install-keep-web.html#dns)", http.StatusBadRequest)
 786                         return
 787                 }
 788
 789                 // The HttpOnly flag is necessary to prevent
 790                 // JavaScript code (included in, or loaded by, a page
 791                 // in the collection being served) from employing the
 792                 // user's token beyond reading other files in the same
 793                 // domain, i.e., same collection.
 794                 //
 795                 // The 303 redirect is necessary in the case of a GET
 796                 // request to avoid exposing the token in the Location
 797                 // bar, and in the case of a POST request to avoid
 798                 // raising warnings when the user refreshes the
 799                 // resulting page.
 800                 http.SetCookie(w, &http.Cookie{
 801                         Name:     "arvados_api_token",
 802                         Value:    auth.EncodeTokenCookie([]byte(formToken)),
 803                         Path:     "/",
 804                         HttpOnly: true,
 805                         SameSite: http.SameSiteLaxMode,
 806                 })
 807         }
 808
 809         // Propagate query parameters (except api_token) from
 810         // the original request.
 811         redirQuery := r.URL.Query()
 812         redirQuery.Del("api_token")
 813
 814         u := r.URL
 815         if location != "" {
 816                 newu, err := u.Parse(location)
 817                 if err != nil {
 818                         http.Error(w, "error resolving redirect target: "+err.Error(), http.StatusInternalServerError)
 819                         return
 820                 }
 821                 u = newu
 822         }
 823         redir := (&url.URL{
 824                 Scheme:   r.URL.Scheme,
 825                 Host:     r.Host,
 826                 Path:     u.Path,
 827                 RawQuery: redirQuery.Encode(),
 828         }).String()
 829
 830         w.Header().Add("Location", redir)
 831         w.WriteHeader(http.StatusSeeOther)
 832         io.WriteString(w, `<A href="`)
 833         io.WriteString(w, html.EscapeString(redir))
 834         io.WriteString(w, `">Continue</A>`)
 835 }