services/keep-web/s3.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         "crypto/hmac"
   9         "crypto/sha256"
  10         "encoding/xml"
  11         "errors"
  12         "fmt"
  13         "hash"
  14         "io"
  15         "net/http"
  16         "net/url"
  17         "os"
  18         "path/filepath"
  19         "regexp"
  20         "sort"
  21         "strconv"
  22         "strings"
  23         "time"
  24
  25         "git.arvados.org/arvados.git/sdk/go/arvados"
  26         "git.arvados.org/arvados.git/sdk/go/ctxlog"
  27         "github.com/AdRoll/goamz/s3"
  28 )
  29
  30 const (
  31         s3MaxKeys       = 1000
  32         s3SignAlgorithm = "AWS4-HMAC-SHA256"
  33         s3MaxClockSkew  = 5 * time.Minute
  34 )
  35
  36 func hmacstring(msg string, key []byte) []byte {
  37         h := hmac.New(sha256.New, key)
  38         io.WriteString(h, msg)
  39         return h.Sum(nil)
  40 }
  41
  42 func hashdigest(h hash.Hash, payload string) string {
  43         io.WriteString(h, payload)
  44         return fmt.Sprintf("%x", h.Sum(nil))
  45 }
  46
  47 // Signing key for given secret key and request attrs.
  48 func s3signatureKey(key, datestamp, regionName, serviceName string) []byte {
  49         return hmacstring("aws4_request",
  50                 hmacstring(serviceName,
  51                         hmacstring(regionName,
  52                                 hmacstring(datestamp, []byte("AWS4"+key)))))
  53 }
  54
  55 // Canonical query string for S3 V4 signature: sorted keys, spaces
  56 // escaped as %20 instead of +, keyvalues joined with &.
  57 func s3querystring(u *url.URL) string {
  58         keys := make([]string, 0, len(u.Query()))
  59         values := make(map[string]string, len(u.Query()))
  60         for k, vs := range u.Query() {
  61                 k = strings.Replace(url.QueryEscape(k), "+", "%20", -1)
  62                 keys = append(keys, k)
  63                 for _, v := range vs {
  64                         v = strings.Replace(url.QueryEscape(v), "+", "%20", -1)
  65                         if values[k] != "" {
  66                                 values[k] += "&"
  67                         }
  68                         values[k] += k + "=" + v
  69                 }
  70         }
  71         sort.Strings(keys)
  72         for i, k := range keys {
  73                 keys[i] = values[k]
  74         }
  75         return strings.Join(keys, "&")
  76 }
  77
  78 var reMultipleSlashChars = regexp.MustCompile(`//+`)
  79
  80 func s3stringToSign(alg, scope, signedHeaders string, r *http.Request) (string, error) {
  81         timefmt, timestr := "20060102T150405Z", r.Header.Get("X-Amz-Date")
  82         if timestr == "" {
  83                 timefmt, timestr = time.RFC1123, r.Header.Get("Date")
  84         }
  85         t, err := time.Parse(timefmt, timestr)
  86         if err != nil {
  87                 return "", fmt.Errorf("invalid timestamp %q: %s", timestr, err)
  88         }
  89         if skew := time.Now().Sub(t); skew < -s3MaxClockSkew || skew > s3MaxClockSkew {
  90                 return "", errors.New("exceeded max clock skew")
  91         }
  92
  93         var canonicalHeaders string
  94         for _, h := range strings.Split(signedHeaders, ";") {
  95                 if h == "host" {
  96                         canonicalHeaders += h + ":" + r.Host + "\n"
  97                 } else {
  98                         canonicalHeaders += h + ":" + r.Header.Get(h) + "\n"
  99                 }
 100         }
 101
 102         normalizedURL := *r.URL
 103         normalizedURL.RawPath = ""
 104         normalizedURL.Path = reMultipleSlashChars.ReplaceAllString(normalizedURL.Path, "/")
 105         ctxlog.FromContext(r.Context()).Infof("escapedPath %s", normalizedURL.EscapedPath())
 106         canonicalRequest := fmt.Sprintf("%s\n%s\n%s\n%s\n%s\n%s", r.Method, normalizedURL.EscapedPath(), s3querystring(r.URL), canonicalHeaders, signedHeaders, r.Header.Get("X-Amz-Content-Sha256"))
 107         ctxlog.FromContext(r.Context()).Debugf("s3stringToSign: canonicalRequest %s", canonicalRequest)
 108         return fmt.Sprintf("%s\n%s\n%s\n%s", alg, r.Header.Get("X-Amz-Date"), scope, hashdigest(sha256.New(), canonicalRequest)), nil
 109 }
 110
 111 func s3signature(secretKey, scope, signedHeaders, stringToSign string) (string, error) {
 112         // scope is {datestamp}/{region}/{service}/aws4_request
 113         drs := strings.Split(scope, "/")
 114         if len(drs) != 4 {
 115                 return "", fmt.Errorf("invalid scope %q", scope)
 116         }
 117         key := s3signatureKey(secretKey, drs[0], drs[1], drs[2])
 118         return hashdigest(hmac.New(sha256.New, key), stringToSign), nil
 119 }
 120
 121 // checks3signature verifies the given S3 V4 signature and returns the
 122 // Arvados token that corresponds to the given accessKey. An error is
 123 // returned if accessKey is not a valid token UUID or the signature
 124 // does not match.
 125 func (h *handler) checks3signature(r *http.Request) (string, error) {
 126         var key, scope, signedHeaders, signature string
 127         authstring := strings.TrimPrefix(r.Header.Get("Authorization"), s3SignAlgorithm+" ")
 128         for _, cmpt := range strings.Split(authstring, ",") {
 129                 cmpt = strings.TrimSpace(cmpt)
 130                 split := strings.SplitN(cmpt, "=", 2)
 131                 switch {
 132                 case len(split) != 2:
 133                         // (?) ignore
 134                 case split[0] == "Credential":
 135                         keyandscope := strings.SplitN(split[1], "/", 2)
 136                         if len(keyandscope) == 2 {
 137                                 key, scope = keyandscope[0], keyandscope[1]
 138                         }
 139                 case split[0] == "SignedHeaders":
 140                         signedHeaders = split[1]
 141                 case split[0] == "Signature":
 142                         signature = split[1]
 143                 }
 144         }
 145
 146         client := (&arvados.Client{
 147                 APIHost:  h.Config.cluster.Services.Controller.ExternalURL.Host,
 148                 Insecure: h.Config.cluster.TLS.Insecure,
 149         }).WithRequestID(r.Header.Get("X-Request-Id"))
 150         var aca arvados.APIClientAuthorization
 151         var secret string
 152         var err error
 153         if len(key) == 27 && key[5:12] == "-gj3su-" {
 154                 // Access key is the UUID of an Arvados token, secret
 155                 // key is the secret part.
 156                 ctx := arvados.ContextWithAuthorization(r.Context(), "Bearer "+h.Config.cluster.SystemRootToken)
 157                 err = client.RequestAndDecodeContext(ctx, &aca, "GET", "arvados/v1/api_client_authorizations/"+key, nil, nil)
 158                 secret = aca.APIToken
 159         } else {
 160                 // Access key and secret key are both an entire
 161                 // Arvados token or OIDC access token.
 162                 ctx := arvados.ContextWithAuthorization(r.Context(), "Bearer "+key)
 163                 err = client.RequestAndDecodeContext(ctx, &aca, "GET", "arvados/v1/api_client_authorizations/current", nil, nil)
 164                 secret = key
 165         }
 166         if err != nil {
 167                 ctxlog.FromContext(r.Context()).WithError(err).WithField("UUID", key).Info("token lookup failed")
 168                 return "", errors.New("invalid access key")
 169         }
 170         stringToSign, err := s3stringToSign(s3SignAlgorithm, scope, signedHeaders, r)
 171         if err != nil {
 172                 return "", err
 173         }
 174         expect, err := s3signature(secret, scope, signedHeaders, stringToSign)
 175         if err != nil {
 176                 return "", err
 177         } else if expect != signature {
 178                 return "", fmt.Errorf("signature does not match (scope %q signedHeaders %q stringToSign %q)", scope, signedHeaders, stringToSign)
 179         }
 180         return secret, nil
 181 }
 182
 183 func s3ErrorResponse(w http.ResponseWriter, s3code string, message string, resource string, code int) {
 184         w.Header().Set("Content-Type", "application/xml")
 185         w.Header().Set("X-Content-Type-Options", "nosniff")
 186         w.WriteHeader(code)
 187         var errstruct struct {
 188                 Code      string
 189                 Message   string
 190                 Resource  string
 191                 RequestId string
 192         }
 193         errstruct.Code = s3code
 194         errstruct.Message = message
 195         errstruct.Resource = resource
 196         errstruct.RequestId = ""
 197         enc := xml.NewEncoder(w)
 198         fmt.Fprint(w, xml.Header)
 199         enc.EncodeElement(errstruct, xml.StartElement{Name: xml.Name{Local: "Error"}})
 200 }
 201
 202 var NoSuchKey = "NoSuchKey"
 203 var NoSuchBucket = "NoSuchBucket"
 204 var InvalidArgument = "InvalidArgument"
 205 var InternalError = "InternalError"
 206 var UnauthorizedAccess = "UnauthorizedAccess"
 207 var InvalidRequest = "InvalidRequest"
 208 var SignatureDoesNotMatch = "SignatureDoesNotMatch"
 209
 210 var reRawQueryIndicatesAPI = regexp.MustCompile(`^[a-z]+(&|$)`)
 211
 212 // serveS3 handles r and returns true if r is a request from an S3
 213 // client, otherwise it returns false.
 214 func (h *handler) serveS3(w http.ResponseWriter, r *http.Request) bool {
 215         var token string
 216         if auth := r.Header.Get("Authorization"); strings.HasPrefix(auth, "AWS ") {
 217                 split := strings.SplitN(auth[4:], ":", 2)
 218                 if len(split) < 2 {
 219                         s3ErrorResponse(w, InvalidRequest, "malformed Authorization header", r.URL.Path, http.StatusUnauthorized)
 220                         return true
 221                 }
 222                 token = split[0]
 223         } else if strings.HasPrefix(auth, s3SignAlgorithm+" ") {
 224                 t, err := h.checks3signature(r)
 225                 if err != nil {
 226                         s3ErrorResponse(w, SignatureDoesNotMatch, "signature verification failed: "+err.Error(), r.URL.Path, http.StatusForbidden)
 227                         return true
 228                 }
 229                 token = t
 230         } else {
 231                 return false
 232         }
 233
 234         var err error
 235         var fs arvados.CustomFileSystem
 236         if r.Method == http.MethodGet || r.Method == http.MethodHead {
 237                 // Use a single session (cached FileSystem) across
 238                 // multiple read requests.
 239                 fs, err = h.Config.Cache.GetSession(token)
 240                 if err != nil {
 241                         s3ErrorResponse(w, InternalError, err.Error(), r.URL.Path, http.StatusInternalServerError)
 242                         return true
 243                 }
 244         } else {
 245                 // Create a FileSystem for this request, to avoid
 246                 // exposing incomplete write operations to concurrent
 247                 // requests.
 248                 _, kc, client, release, err := h.getClients(r.Header.Get("X-Request-Id"), token)
 249                 if err != nil {
 250                         s3ErrorResponse(w, InternalError, err.Error(), r.URL.Path, http.StatusInternalServerError)
 251                         return true
 252                 }
 253                 defer release()
 254                 fs = client.SiteFileSystem(kc)
 255                 fs.ForwardSlashNameSubstitution(h.Config.cluster.Collections.ForwardSlashNameSubstitution)
 256         }
 257
 258         var objectNameGiven bool
 259         var bucketName string
 260         fspath := "/by_id"
 261         if id := parseCollectionIDFromDNSName(r.Host); id != "" {
 262                 fspath += "/" + id
 263                 bucketName = id
 264                 objectNameGiven = strings.Count(strings.TrimSuffix(r.URL.Path, "/"), "/") > 0
 265         } else {
 266                 bucketName = strings.SplitN(strings.TrimPrefix(r.URL.Path, "/"), "/", 2)[0]
 267                 objectNameGiven = strings.Count(strings.TrimSuffix(r.URL.Path, "/"), "/") > 1
 268         }
 269         fspath += reMultipleSlashChars.ReplaceAllString(r.URL.Path, "/")
 270
 271         switch {
 272         case r.Method == http.MethodGet && !objectNameGiven:
 273                 // Path is "/{uuid}" or "/{uuid}/", has no object name
 274                 if _, ok := r.URL.Query()["versioning"]; ok {
 275                         // GetBucketVersioning
 276                         w.Header().Set("Content-Type", "application/xml")
 277                         io.WriteString(w, xml.Header)
 278                         fmt.Fprintln(w, `<VersioningConfiguration xmlns="http://s3.amazonaws.com/doc/2006-03-01/"/>`)
 279                 } else if _, ok = r.URL.Query()["location"]; ok {
 280                         // GetBucketLocation
 281                         w.Header().Set("Content-Type", "application/xml")
 282                         io.WriteString(w, xml.Header)
 283                         fmt.Fprintln(w, `<LocationConstraint><LocationConstraint xmlns="http://s3.amazonaws.com/doc/2006-03-01/">`+
 284                                 h.Config.cluster.ClusterID+
 285                                 `</LocationConstraint></LocationConstraint>`)
 286                 } else if reRawQueryIndicatesAPI.MatchString(r.URL.RawQuery) {
 287                         // GetBucketWebsite ("GET /bucketid/?website"), GetBucketTagging, etc.
 288                         s3ErrorResponse(w, InvalidRequest, "API not supported", r.URL.Path+"?"+r.URL.RawQuery, http.StatusBadRequest)
 289                 } else {
 290                         // ListObjects
 291                         h.s3list(bucketName, w, r, fs)
 292                 }
 293                 return true
 294         case r.Method == http.MethodGet || r.Method == http.MethodHead:
 295                 if reRawQueryIndicatesAPI.MatchString(r.URL.RawQuery) {
 296                         // GetObjectRetention ("GET /bucketid/objectid?retention&versionID=..."), etc.
 297                         s3ErrorResponse(w, InvalidRequest, "API not supported", r.URL.Path+"?"+r.URL.RawQuery, http.StatusBadRequest)
 298                         return true
 299                 }
 300                 fi, err := fs.Stat(fspath)
 301                 if r.Method == "HEAD" && !objectNameGiven {
 302                         // HeadBucket
 303                         if err == nil && fi.IsDir() {
 304                                 w.WriteHeader(http.StatusOK)
 305                         } else if os.IsNotExist(err) {
 306                                 s3ErrorResponse(w, NoSuchBucket, "The specified bucket does not exist.", r.URL.Path, http.StatusNotFound)
 307                         } else {
 308                                 s3ErrorResponse(w, InternalError, err.Error(), r.URL.Path, http.StatusBadGateway)
 309                         }
 310                         return true
 311                 }
 312                 if err == nil && fi.IsDir() && objectNameGiven && strings.HasSuffix(fspath, "/") && h.Config.cluster.Collections.S3FolderObjects {
 313                         w.Header().Set("Content-Type", "application/x-directory")
 314                         w.WriteHeader(http.StatusOK)
 315                         return true
 316                 }
 317                 if os.IsNotExist(err) ||
 318                         (err != nil && err.Error() == "not a directory") ||
 319                         (fi != nil && fi.IsDir()) {
 320                         s3ErrorResponse(w, NoSuchKey, "The specified key does not exist.", r.URL.Path, http.StatusNotFound)
 321                         return true
 322                 }
 323                 // shallow copy r, and change URL path
 324                 r := *r
 325                 r.URL.Path = fspath
 326                 http.FileServer(fs).ServeHTTP(w, &r)
 327                 return true
 328         case r.Method == http.MethodPut:
 329                 if reRawQueryIndicatesAPI.MatchString(r.URL.RawQuery) {
 330                         // PutObjectAcl ("PUT /bucketid/objectid?acl&versionID=..."), etc.
 331                         s3ErrorResponse(w, InvalidRequest, "API not supported", r.URL.Path+"?"+r.URL.RawQuery, http.StatusBadRequest)
 332                         return true
 333                 }
 334                 if !objectNameGiven {
 335                         s3ErrorResponse(w, InvalidArgument, "Missing object name in PUT request.", r.URL.Path, http.StatusBadRequest)
 336                         return true
 337                 }
 338                 var objectIsDir bool
 339                 if strings.HasSuffix(fspath, "/") {
 340                         if !h.Config.cluster.Collections.S3FolderObjects {
 341                                 s3ErrorResponse(w, InvalidArgument, "invalid object name: trailing slash", r.URL.Path, http.StatusBadRequest)
 342                                 return true
 343                         }
 344                         n, err := r.Body.Read(make([]byte, 1))
 345                         if err != nil && err != io.EOF {
 346                                 s3ErrorResponse(w, InternalError, fmt.Sprintf("error reading request body: %s", err), r.URL.Path, http.StatusInternalServerError)
 347                                 return true
 348                         } else if n > 0 {
 349                                 s3ErrorResponse(w, InvalidArgument, "cannot create object with trailing '/' char unless content is empty", r.URL.Path, http.StatusBadRequest)
 350                                 return true
 351                         } else if strings.SplitN(r.Header.Get("Content-Type"), ";", 2)[0] != "application/x-directory" {
 352                                 s3ErrorResponse(w, InvalidArgument, "cannot create object with trailing '/' char unless Content-Type is 'application/x-directory'", r.URL.Path, http.StatusBadRequest)
 353                                 return true
 354                         }
 355                         // Given PUT "foo/bar/", we'll use "foo/bar/."
 356                         // in the "ensure parents exist" block below,
 357                         // and then we'll be done.
 358                         fspath += "."
 359                         objectIsDir = true
 360                 }
 361                 fi, err := fs.Stat(fspath)
 362                 if err != nil && err.Error() == "not a directory" {
 363                         // requested foo/bar, but foo is a file
 364                         s3ErrorResponse(w, InvalidArgument, "object name conflicts with existing object", r.URL.Path, http.StatusBadRequest)
 365                         return true
 366                 }
 367                 if strings.HasSuffix(r.URL.Path, "/") && err == nil && !fi.IsDir() {
 368                         // requested foo/bar/, but foo/bar is a file
 369                         s3ErrorResponse(w, InvalidArgument, "object name conflicts with existing object", r.URL.Path, http.StatusBadRequest)
 370                         return true
 371                 }
 372                 // create missing parent/intermediate directories, if any
 373                 for i, c := range fspath {
 374                         if i > 0 && c == '/' {
 375                                 dir := fspath[:i]
 376                                 if strings.HasSuffix(dir, "/") {
 377                                         err = errors.New("invalid object name (consecutive '/' chars)")
 378                                         s3ErrorResponse(w, InvalidArgument, err.Error(), r.URL.Path, http.StatusBadRequest)
 379                                         return true
 380                                 }
 381                                 err = fs.Mkdir(dir, 0755)
 382                                 if err == arvados.ErrInvalidArgument {
 383                                         // Cannot create a directory
 384                                         // here.
 385                                         err = fmt.Errorf("mkdir %q failed: %w", dir, err)
 386                                         s3ErrorResponse(w, InvalidArgument, err.Error(), r.URL.Path, http.StatusBadRequest)
 387                                         return true
 388                                 } else if err != nil && !os.IsExist(err) {
 389                                         err = fmt.Errorf("mkdir %q failed: %w", dir, err)
 390                                         s3ErrorResponse(w, InternalError, err.Error(), r.URL.Path, http.StatusInternalServerError)
 391                                         return true
 392                                 }
 393                         }
 394                 }
 395                 if !objectIsDir {
 396                         f, err := fs.OpenFile(fspath, os.O_WRONLY|os.O_TRUNC|os.O_CREATE, 0644)
 397                         if os.IsNotExist(err) {
 398                                 f, err = fs.OpenFile(fspath, os.O_WRONLY|os.O_TRUNC|os.O_CREATE, 0644)
 399                         }
 400                         if err != nil {
 401                                 err = fmt.Errorf("open %q failed: %w", r.URL.Path, err)
 402                                 s3ErrorResponse(w, InvalidArgument, err.Error(), r.URL.Path, http.StatusBadRequest)
 403                                 return true
 404                         }
 405                         defer f.Close()
 406                         _, err = io.Copy(f, r.Body)
 407                         if err != nil {
 408                                 err = fmt.Errorf("write to %q failed: %w", r.URL.Path, err)
 409                                 s3ErrorResponse(w, InternalError, err.Error(), r.URL.Path, http.StatusBadGateway)
 410                                 return true
 411                         }
 412                         err = f.Close()
 413                         if err != nil {
 414                                 err = fmt.Errorf("write to %q failed: close: %w", r.URL.Path, err)
 415                                 s3ErrorResponse(w, InternalError, err.Error(), r.URL.Path, http.StatusBadGateway)
 416                                 return true
 417                         }
 418                 }
 419                 err = fs.Sync()
 420                 if err != nil {
 421                         err = fmt.Errorf("sync failed: %w", err)
 422                         s3ErrorResponse(w, InternalError, err.Error(), r.URL.Path, http.StatusInternalServerError)
 423                         return true
 424                 }
 425                 // Ensure a subsequent read operation will see the changes.
 426                 h.Config.Cache.ResetSession(token)
 427                 w.WriteHeader(http.StatusOK)
 428                 return true
 429         case r.Method == http.MethodDelete:
 430                 if reRawQueryIndicatesAPI.MatchString(r.URL.RawQuery) {
 431                         // DeleteObjectTagging ("DELETE /bucketid/objectid?tagging&versionID=..."), etc.
 432                         s3ErrorResponse(w, InvalidRequest, "API not supported", r.URL.Path+"?"+r.URL.RawQuery, http.StatusBadRequest)
 433                         return true
 434                 }
 435                 if !objectNameGiven || r.URL.Path == "/" {
 436                         s3ErrorResponse(w, InvalidArgument, "missing object name in DELETE request", r.URL.Path, http.StatusBadRequest)
 437                         return true
 438                 }
 439                 if strings.HasSuffix(fspath, "/") {
 440                         fspath = strings.TrimSuffix(fspath, "/")
 441                         fi, err := fs.Stat(fspath)
 442                         if os.IsNotExist(err) {
 443                                 w.WriteHeader(http.StatusNoContent)
 444                                 return true
 445                         } else if err != nil {
 446                                 s3ErrorResponse(w, InternalError, err.Error(), r.URL.Path, http.StatusInternalServerError)
 447                                 return true
 448                         } else if !fi.IsDir() {
 449                                 // if "foo" exists and is a file, then
 450                                 // "foo/" doesn't exist, so we say
 451                                 // delete was successful.
 452                                 w.WriteHeader(http.StatusNoContent)
 453                                 return true
 454                         }
 455                 } else if fi, err := fs.Stat(fspath); err == nil && fi.IsDir() {
 456                         // if "foo" is a dir, it is visible via S3
 457                         // only as "foo/", not "foo" -- so we leave
 458                         // the dir alone and return 204 to indicate
 459                         // that "foo" does not exist.
 460                         w.WriteHeader(http.StatusNoContent)
 461                         return true
 462                 }
 463                 err = fs.Remove(fspath)
 464                 if os.IsNotExist(err) {
 465                         w.WriteHeader(http.StatusNoContent)
 466                         return true
 467                 }
 468                 if err != nil {
 469                         err = fmt.Errorf("rm failed: %w", err)
 470                         s3ErrorResponse(w, InvalidArgument, err.Error(), r.URL.Path, http.StatusBadRequest)
 471                         return true
 472                 }
 473                 err = fs.Sync()
 474                 if err != nil {
 475                         err = fmt.Errorf("sync failed: %w", err)
 476                         s3ErrorResponse(w, InternalError, err.Error(), r.URL.Path, http.StatusInternalServerError)
 477                         return true
 478                 }
 479                 // Ensure a subsequent read operation will see the changes.
 480                 h.Config.Cache.ResetSession(token)
 481                 w.WriteHeader(http.StatusNoContent)
 482                 return true
 483         default:
 484                 s3ErrorResponse(w, InvalidRequest, "method not allowed", r.URL.Path, http.StatusMethodNotAllowed)
 485                 return true
 486         }
 487 }
 488
 489 // Call fn on the given path (directory) and its contents, in
 490 // lexicographic order.
 491 //
 492 // If isRoot==true and path is not a directory, return nil.
 493 //
 494 // If fn returns filepath.SkipDir when called on a directory, don't
 495 // descend into that directory.
 496 func walkFS(fs arvados.CustomFileSystem, path string, isRoot bool, fn func(path string, fi os.FileInfo) error) error {
 497         if isRoot {
 498                 fi, err := fs.Stat(path)
 499                 if os.IsNotExist(err) || (err == nil && !fi.IsDir()) {
 500                         return nil
 501                 } else if err != nil {
 502                         return err
 503                 }
 504                 err = fn(path, fi)
 505                 if err == filepath.SkipDir {
 506                         return nil
 507                 } else if err != nil {
 508                         return err
 509                 }
 510         }
 511         f, err := fs.Open(path)
 512         if os.IsNotExist(err) && isRoot {
 513                 return nil
 514         } else if err != nil {
 515                 return fmt.Errorf("open %q: %w", path, err)
 516         }
 517         defer f.Close()
 518         if path == "/" {
 519                 path = ""
 520         }
 521         fis, err := f.Readdir(-1)
 522         if err != nil {
 523                 return err
 524         }
 525         sort.Slice(fis, func(i, j int) bool { return fis[i].Name() < fis[j].Name() })
 526         for _, fi := range fis {
 527                 err = fn(path+"/"+fi.Name(), fi)
 528                 if err == filepath.SkipDir {
 529                         continue
 530                 } else if err != nil {
 531                         return err
 532                 }
 533                 if fi.IsDir() {
 534                         err = walkFS(fs, path+"/"+fi.Name(), false, fn)
 535                         if err != nil {
 536                                 return err
 537                         }
 538                 }
 539         }
 540         return nil
 541 }
 542
 543 var errDone = errors.New("done")
 544
 545 func (h *handler) s3list(bucket string, w http.ResponseWriter, r *http.Request, fs arvados.CustomFileSystem) {
 546         var params struct {
 547                 delimiter string
 548                 marker    string
 549                 maxKeys   int
 550                 prefix    string
 551         }
 552         params.delimiter = r.FormValue("delimiter")
 553         params.marker = r.FormValue("marker")
 554         if mk, _ := strconv.ParseInt(r.FormValue("max-keys"), 10, 64); mk > 0 && mk < s3MaxKeys {
 555                 params.maxKeys = int(mk)
 556         } else {
 557                 params.maxKeys = s3MaxKeys
 558         }
 559         params.prefix = r.FormValue("prefix")
 560
 561         bucketdir := "by_id/" + bucket
 562         // walkpath is the directory (relative to bucketdir) we need
 563         // to walk: the innermost directory that is guaranteed to
 564         // contain all paths that have the requested prefix. Examples:
 565         // prefix "foo/bar"  => walkpath "foo"
 566         // prefix "foo/bar/" => walkpath "foo/bar"
 567         // prefix "foo"      => walkpath ""
 568         // prefix ""         => walkpath ""
 569         walkpath := params.prefix
 570         if cut := strings.LastIndex(walkpath, "/"); cut >= 0 {
 571                 walkpath = walkpath[:cut]
 572         } else {
 573                 walkpath = ""
 574         }
 575
 576         type commonPrefix struct {
 577                 Prefix string
 578         }
 579         type listResp struct {
 580                 XMLName string `xml:"http://s3.amazonaws.com/doc/2006-03-01/ ListBucketResult"`
 581                 s3.ListResp
 582                 // s3.ListResp marshals an empty tag when
 583                 // CommonPrefixes is nil, which confuses some clients.
 584                 // Fix by using this nested struct instead.
 585                 CommonPrefixes []commonPrefix
 586                 // Similarly, we need omitempty here, because an empty
 587                 // tag confuses some clients (e.g.,
 588                 // github.com/aws/aws-sdk-net never terminates its
 589                 // paging loop).
 590                 NextMarker string `xml:"NextMarker,omitempty"`
 591                 // ListObjectsV2 has a KeyCount response field.
 592                 KeyCount int
 593         }
 594         resp := listResp{
 595                 ListResp: s3.ListResp{
 596                         Name:      bucket,
 597                         Prefix:    params.prefix,
 598                         Delimiter: params.delimiter,
 599                         Marker:    params.marker,
 600                         MaxKeys:   params.maxKeys,
 601                 },
 602         }
 603         commonPrefixes := map[string]bool{}
 604         err := walkFS(fs, strings.TrimSuffix(bucketdir+"/"+walkpath, "/"), true, func(path string, fi os.FileInfo) error {
 605                 if path == bucketdir {
 606                         return nil
 607                 }
 608                 path = path[len(bucketdir)+1:]
 609                 filesize := fi.Size()
 610                 if fi.IsDir() {
 611                         path += "/"
 612                         filesize = 0
 613                 }
 614                 if len(path) <= len(params.prefix) {
 615                         if path > params.prefix[:len(path)] {
 616                                 // with prefix "foobar", walking "fooz" means we're done
 617                                 return errDone
 618                         }
 619                         if path < params.prefix[:len(path)] {
 620                                 // with prefix "foobar", walking "foobag" is pointless
 621                                 return filepath.SkipDir
 622                         }
 623                         if fi.IsDir() && !strings.HasPrefix(params.prefix+"/", path) {
 624                                 // with prefix "foo/bar", walking "fo"
 625                                 // is pointless (but walking "foo" or
 626                                 // "foo/bar" is necessary)
 627                                 return filepath.SkipDir
 628                         }
 629                         if len(path) < len(params.prefix) {
 630                                 // can't skip anything, and this entry
 631                                 // isn't in the results, so just
 632                                 // continue descent
 633                                 return nil
 634                         }
 635                 } else {
 636                         if path[:len(params.prefix)] > params.prefix {
 637                                 // with prefix "foobar", nothing we
 638                                 // see after "foozzz" is relevant
 639                                 return errDone
 640                         }
 641                 }
 642                 if path < params.marker || path < params.prefix {
 643                         return nil
 644                 }
 645                 if fi.IsDir() && !h.Config.cluster.Collections.S3FolderObjects {
 646                         // Note we don't add anything to
 647                         // commonPrefixes here even if delimiter is
 648                         // "/". We descend into the directory, and
 649                         // return a commonPrefix only if we end up
 650                         // finding a regular file inside it.
 651                         return nil
 652                 }
 653                 if params.delimiter != "" {
 654                         idx := strings.Index(path[len(params.prefix):], params.delimiter)
 655                         if idx >= 0 {
 656                                 // with prefix "foobar" and delimiter
 657                                 // "z", when we hit "foobar/baz", we
 658                                 // add "/baz" to commonPrefixes and
 659                                 // stop descending.
 660                                 commonPrefixes[path[:len(params.prefix)+idx+1]] = true
 661                                 return filepath.SkipDir
 662                         }
 663                 }
 664                 if len(resp.Contents)+len(commonPrefixes) >= params.maxKeys {
 665                         resp.IsTruncated = true
 666                         if params.delimiter != "" {
 667                                 resp.NextMarker = path
 668                         }
 669                         return errDone
 670                 }
 671                 resp.Contents = append(resp.Contents, s3.Key{
 672                         Key:          path,
 673                         LastModified: fi.ModTime().UTC().Format("2006-01-02T15:04:05.999") + "Z",
 674                         Size:         filesize,
 675                 })
 676                 return nil
 677         })
 678         if err != nil && err != errDone {
 679                 http.Error(w, err.Error(), http.StatusInternalServerError)
 680                 return
 681         }
 682         if params.delimiter != "" {
 683                 resp.CommonPrefixes = make([]commonPrefix, 0, len(commonPrefixes))
 684                 for prefix := range commonPrefixes {
 685                         resp.CommonPrefixes = append(resp.CommonPrefixes, commonPrefix{prefix})
 686                 }
 687                 sort.Slice(resp.CommonPrefixes, func(i, j int) bool { return resp.CommonPrefixes[i].Prefix < resp.CommonPrefixes[j].Prefix })
 688         }
 689         resp.KeyCount = len(resp.Contents)
 690         w.Header().Set("Content-Type", "application/xml")
 691         io.WriteString(w, xml.Header)
 692         if err := xml.NewEncoder(w).Encode(resp); err != nil {
 693                 ctxlog.FromContext(r.Context()).WithError(err).Error("error writing xml response")
 694         }
 695 }