1 // Copyright (C) The Arvados Authors. All rights reserved.
3 // SPDX-License-Identifier: AGPL-3.0
25 "git.arvados.org/arvados.git/sdk/go/arvados"
26 "git.arvados.org/arvados.git/sdk/go/ctxlog"
27 "github.com/AdRoll/goamz/s3"
32 s3SignAlgorithm = "AWS4-HMAC-SHA256"
33 s3MaxClockSkew = 5 * time.Minute
36 func hmacstring(msg string, key []byte) []byte {
37 h := hmac.New(sha256.New, key)
38 io.WriteString(h, msg)
42 func hashdigest(h hash.Hash, payload string) string {
43 io.WriteString(h, payload)
44 return fmt.Sprintf("%x", h.Sum(nil))
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)))))
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)
68 values[k] += k + "=" + v
72 for i, k := range keys {
75 return strings.Join(keys, "&")
78 var reMultipleSlashChars = regexp.MustCompile(`//+`)
80 func s3stringToSign(alg, scope, signedHeaders string, r *http.Request) (string, error) {
81 timefmt, timestr := "20060102T150405Z", r.Header.Get("X-Amz-Date")
83 timefmt, timestr = time.RFC1123, r.Header.Get("Date")
85 t, err := time.Parse(timefmt, timestr)
87 return "", fmt.Errorf("invalid timestamp %q: %s", timestr, err)
89 if skew := time.Now().Sub(t); skew < -s3MaxClockSkew || skew > s3MaxClockSkew {
90 return "", errors.New("exceeded max clock skew")
93 var canonicalHeaders string
94 for _, h := range strings.Split(signedHeaders, ";") {
96 canonicalHeaders += h + ":" + r.Host + "\n"
98 canonicalHeaders += h + ":" + r.Header.Get(h) + "\n"
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
111 func s3signature(secretKey, scope, signedHeaders, stringToSign string) (string, error) {
112 // scope is {datestamp}/{region}/{service}/aws4_request
113 drs := strings.Split(scope, "/")
115 return "", fmt.Errorf("invalid scope %q", scope)
117 key := s3signatureKey(secretKey, drs[0], drs[1], drs[2])
118 return hashdigest(hmac.New(sha256.New, key), stringToSign), nil
121 var v2tokenUnderscore = regexp.MustCompile(`^v2_[a-z0-9]{5}-gj3su-[a-z0-9]{15}_`)
123 func unescapeKey(key string) string {
124 if v2tokenUnderscore.MatchString(key) {
125 // Entire Arvados token, with "/" replaced by "_" to
126 // avoid colliding with the Authorization header
128 return strings.Replace(key, "_", "/", -1)
129 } else if s, err := url.PathUnescape(key); err == nil {
136 // checks3signature verifies the given S3 V4 signature and returns the
137 // Arvados token that corresponds to the given accessKey. An error is
138 // returned if accessKey is not a valid token UUID or the signature
140 func (h *handler) checks3signature(r *http.Request) (string, error) {
141 var key, scope, signedHeaders, signature string
142 authstring := strings.TrimPrefix(r.Header.Get("Authorization"), s3SignAlgorithm+" ")
143 for _, cmpt := range strings.Split(authstring, ",") {
144 cmpt = strings.TrimSpace(cmpt)
145 split := strings.SplitN(cmpt, "=", 2)
147 case len(split) != 2:
149 case split[0] == "Credential":
150 keyandscope := strings.SplitN(split[1], "/", 2)
151 if len(keyandscope) == 2 {
152 key, scope = keyandscope[0], keyandscope[1]
154 case split[0] == "SignedHeaders":
155 signedHeaders = split[1]
156 case split[0] == "Signature":
161 client := (&arvados.Client{
162 APIHost: h.Config.cluster.Services.Controller.ExternalURL.Host,
163 Insecure: h.Config.cluster.TLS.Insecure,
164 }).WithRequestID(r.Header.Get("X-Request-Id"))
165 var aca arvados.APIClientAuthorization
168 if len(key) == 27 && key[5:12] == "-gj3su-" {
169 // Access key is the UUID of an Arvados token, secret
170 // key is the secret part.
171 ctx := arvados.ContextWithAuthorization(r.Context(), "Bearer "+h.Config.cluster.SystemRootToken)
172 err = client.RequestAndDecodeContext(ctx, &aca, "GET", "arvados/v1/api_client_authorizations/"+key, nil, nil)
173 secret = aca.APIToken
175 // Access key and secret key are both an entire
176 // Arvados token or OIDC access token.
177 ctx := arvados.ContextWithAuthorization(r.Context(), "Bearer "+unescapeKey(key))
178 err = client.RequestAndDecodeContext(ctx, &aca, "GET", "arvados/v1/api_client_authorizations/current", nil, nil)
182 ctxlog.FromContext(r.Context()).WithError(err).WithField("UUID", key).Info("token lookup failed")
183 return "", errors.New("invalid access key")
185 stringToSign, err := s3stringToSign(s3SignAlgorithm, scope, signedHeaders, r)
189 expect, err := s3signature(secret, scope, signedHeaders, stringToSign)
192 } else if expect != signature {
193 return "", fmt.Errorf("signature does not match (scope %q signedHeaders %q stringToSign %q)", scope, signedHeaders, stringToSign)
195 return aca.TokenV2(), nil
198 func s3ErrorResponse(w http.ResponseWriter, s3code string, message string, resource string, code int) {
199 w.Header().Set("Content-Type", "application/xml")
200 w.Header().Set("X-Content-Type-Options", "nosniff")
202 var errstruct struct {
208 errstruct.Code = s3code
209 errstruct.Message = message
210 errstruct.Resource = resource
211 errstruct.RequestId = ""
212 enc := xml.NewEncoder(w)
213 fmt.Fprint(w, xml.Header)
214 enc.EncodeElement(errstruct, xml.StartElement{Name: xml.Name{Local: "Error"}})
217 var NoSuchKey = "NoSuchKey"
218 var NoSuchBucket = "NoSuchBucket"
219 var InvalidArgument = "InvalidArgument"
220 var InternalError = "InternalError"
221 var UnauthorizedAccess = "UnauthorizedAccess"
222 var InvalidRequest = "InvalidRequest"
223 var SignatureDoesNotMatch = "SignatureDoesNotMatch"
225 var reRawQueryIndicatesAPI = regexp.MustCompile(`^[a-z]+(&|$)`)
227 // serveS3 handles r and returns true if r is a request from an S3
228 // client, otherwise it returns false.
229 func (h *handler) serveS3(w http.ResponseWriter, r *http.Request) bool {
231 if auth := r.Header.Get("Authorization"); strings.HasPrefix(auth, "AWS ") {
232 split := strings.SplitN(auth[4:], ":", 2)
234 s3ErrorResponse(w, InvalidRequest, "malformed Authorization header", r.URL.Path, http.StatusUnauthorized)
237 token = unescapeKey(split[0])
238 } else if strings.HasPrefix(auth, s3SignAlgorithm+" ") {
239 t, err := h.checks3signature(r)
241 s3ErrorResponse(w, SignatureDoesNotMatch, "signature verification failed: "+err.Error(), r.URL.Path, http.StatusForbidden)
250 var fs arvados.CustomFileSystem
251 if r.Method == http.MethodGet || r.Method == http.MethodHead {
252 // Use a single session (cached FileSystem) across
253 // multiple read requests.
254 fs, err = h.Config.Cache.GetSession(token)
256 s3ErrorResponse(w, InternalError, err.Error(), r.URL.Path, http.StatusInternalServerError)
260 // Create a FileSystem for this request, to avoid
261 // exposing incomplete write operations to concurrent
263 _, kc, client, release, err := h.getClients(r.Header.Get("X-Request-Id"), token)
265 s3ErrorResponse(w, InternalError, err.Error(), r.URL.Path, http.StatusInternalServerError)
269 fs = client.SiteFileSystem(kc)
270 fs.ForwardSlashNameSubstitution(h.Config.cluster.Collections.ForwardSlashNameSubstitution)
273 var objectNameGiven bool
274 var bucketName string
276 if id := parseCollectionIDFromDNSName(r.Host); id != "" {
279 objectNameGiven = strings.Count(strings.TrimSuffix(r.URL.Path, "/"), "/") > 0
281 bucketName = strings.SplitN(strings.TrimPrefix(r.URL.Path, "/"), "/", 2)[0]
282 objectNameGiven = strings.Count(strings.TrimSuffix(r.URL.Path, "/"), "/") > 1
284 fspath += reMultipleSlashChars.ReplaceAllString(r.URL.Path, "/")
287 case r.Method == http.MethodGet && !objectNameGiven:
288 // Path is "/{uuid}" or "/{uuid}/", has no object name
289 if _, ok := r.URL.Query()["versioning"]; ok {
290 // GetBucketVersioning
291 w.Header().Set("Content-Type", "application/xml")
292 io.WriteString(w, xml.Header)
293 fmt.Fprintln(w, `<VersioningConfiguration xmlns="http://s3.amazonaws.com/doc/2006-03-01/"/>`)
294 } else if _, ok = r.URL.Query()["location"]; ok {
296 w.Header().Set("Content-Type", "application/xml")
297 io.WriteString(w, xml.Header)
298 fmt.Fprintln(w, `<LocationConstraint><LocationConstraint xmlns="http://s3.amazonaws.com/doc/2006-03-01/">`+
299 h.Config.cluster.ClusterID+
300 `</LocationConstraint></LocationConstraint>`)
301 } else if reRawQueryIndicatesAPI.MatchString(r.URL.RawQuery) {
302 // GetBucketWebsite ("GET /bucketid/?website"), GetBucketTagging, etc.
303 s3ErrorResponse(w, InvalidRequest, "API not supported", r.URL.Path+"?"+r.URL.RawQuery, http.StatusBadRequest)
306 h.s3list(bucketName, w, r, fs)
309 case r.Method == http.MethodGet || r.Method == http.MethodHead:
310 if reRawQueryIndicatesAPI.MatchString(r.URL.RawQuery) {
311 // GetObjectRetention ("GET /bucketid/objectid?retention&versionID=..."), etc.
312 s3ErrorResponse(w, InvalidRequest, "API not supported", r.URL.Path+"?"+r.URL.RawQuery, http.StatusBadRequest)
315 fi, err := fs.Stat(fspath)
316 if r.Method == "HEAD" && !objectNameGiven {
318 if err == nil && fi.IsDir() {
319 w.WriteHeader(http.StatusOK)
320 } else if os.IsNotExist(err) {
321 s3ErrorResponse(w, NoSuchBucket, "The specified bucket does not exist.", r.URL.Path, http.StatusNotFound)
323 s3ErrorResponse(w, InternalError, err.Error(), r.URL.Path, http.StatusBadGateway)
327 if err == nil && fi.IsDir() && objectNameGiven && strings.HasSuffix(fspath, "/") && h.Config.cluster.Collections.S3FolderObjects {
328 w.Header().Set("Content-Type", "application/x-directory")
329 w.WriteHeader(http.StatusOK)
332 if os.IsNotExist(err) ||
333 (err != nil && err.Error() == "not a directory") ||
334 (fi != nil && fi.IsDir()) {
335 s3ErrorResponse(w, NoSuchKey, "The specified key does not exist.", r.URL.Path, http.StatusNotFound)
338 // shallow copy r, and change URL path
341 http.FileServer(fs).ServeHTTP(w, &r)
343 case r.Method == http.MethodPut:
344 if reRawQueryIndicatesAPI.MatchString(r.URL.RawQuery) {
345 // PutObjectAcl ("PUT /bucketid/objectid?acl&versionID=..."), etc.
346 s3ErrorResponse(w, InvalidRequest, "API not supported", r.URL.Path+"?"+r.URL.RawQuery, http.StatusBadRequest)
349 if !objectNameGiven {
350 s3ErrorResponse(w, InvalidArgument, "Missing object name in PUT request.", r.URL.Path, http.StatusBadRequest)
354 if strings.HasSuffix(fspath, "/") {
355 if !h.Config.cluster.Collections.S3FolderObjects {
356 s3ErrorResponse(w, InvalidArgument, "invalid object name: trailing slash", r.URL.Path, http.StatusBadRequest)
359 n, err := r.Body.Read(make([]byte, 1))
360 if err != nil && err != io.EOF {
361 s3ErrorResponse(w, InternalError, fmt.Sprintf("error reading request body: %s", err), r.URL.Path, http.StatusInternalServerError)
364 s3ErrorResponse(w, InvalidArgument, "cannot create object with trailing '/' char unless content is empty", r.URL.Path, http.StatusBadRequest)
366 } else if strings.SplitN(r.Header.Get("Content-Type"), ";", 2)[0] != "application/x-directory" {
367 s3ErrorResponse(w, InvalidArgument, "cannot create object with trailing '/' char unless Content-Type is 'application/x-directory'", r.URL.Path, http.StatusBadRequest)
370 // Given PUT "foo/bar/", we'll use "foo/bar/."
371 // in the "ensure parents exist" block below,
372 // and then we'll be done.
376 fi, err := fs.Stat(fspath)
377 if err != nil && err.Error() == "not a directory" {
378 // requested foo/bar, but foo is a file
379 s3ErrorResponse(w, InvalidArgument, "object name conflicts with existing object", r.URL.Path, http.StatusBadRequest)
382 if strings.HasSuffix(r.URL.Path, "/") && err == nil && !fi.IsDir() {
383 // requested foo/bar/, but foo/bar is a file
384 s3ErrorResponse(w, InvalidArgument, "object name conflicts with existing object", r.URL.Path, http.StatusBadRequest)
387 // create missing parent/intermediate directories, if any
388 for i, c := range fspath {
389 if i > 0 && c == '/' {
391 if strings.HasSuffix(dir, "/") {
392 err = errors.New("invalid object name (consecutive '/' chars)")
393 s3ErrorResponse(w, InvalidArgument, err.Error(), r.URL.Path, http.StatusBadRequest)
396 err = fs.Mkdir(dir, 0755)
397 if err == arvados.ErrInvalidArgument {
398 // Cannot create a directory
400 err = fmt.Errorf("mkdir %q failed: %w", dir, err)
401 s3ErrorResponse(w, InvalidArgument, err.Error(), r.URL.Path, http.StatusBadRequest)
403 } else if err != nil && !os.IsExist(err) {
404 err = fmt.Errorf("mkdir %q failed: %w", dir, err)
405 s3ErrorResponse(w, InternalError, err.Error(), r.URL.Path, http.StatusInternalServerError)
411 f, err := fs.OpenFile(fspath, os.O_WRONLY|os.O_TRUNC|os.O_CREATE, 0644)
412 if os.IsNotExist(err) {
413 f, err = fs.OpenFile(fspath, os.O_WRONLY|os.O_TRUNC|os.O_CREATE, 0644)
416 err = fmt.Errorf("open %q failed: %w", r.URL.Path, err)
417 s3ErrorResponse(w, InvalidArgument, err.Error(), r.URL.Path, http.StatusBadRequest)
421 _, err = io.Copy(f, r.Body)
423 err = fmt.Errorf("write to %q failed: %w", r.URL.Path, err)
424 s3ErrorResponse(w, InternalError, err.Error(), r.URL.Path, http.StatusBadGateway)
429 err = fmt.Errorf("write to %q failed: close: %w", r.URL.Path, err)
430 s3ErrorResponse(w, InternalError, err.Error(), r.URL.Path, http.StatusBadGateway)
436 err = fmt.Errorf("sync failed: %w", err)
437 s3ErrorResponse(w, InternalError, err.Error(), r.URL.Path, http.StatusInternalServerError)
440 // Ensure a subsequent read operation will see the changes.
441 h.Config.Cache.ResetSession(token)
442 w.WriteHeader(http.StatusOK)
444 case r.Method == http.MethodDelete:
445 if reRawQueryIndicatesAPI.MatchString(r.URL.RawQuery) {
446 // DeleteObjectTagging ("DELETE /bucketid/objectid?tagging&versionID=..."), etc.
447 s3ErrorResponse(w, InvalidRequest, "API not supported", r.URL.Path+"?"+r.URL.RawQuery, http.StatusBadRequest)
450 if !objectNameGiven || r.URL.Path == "/" {
451 s3ErrorResponse(w, InvalidArgument, "missing object name in DELETE request", r.URL.Path, http.StatusBadRequest)
454 if strings.HasSuffix(fspath, "/") {
455 fspath = strings.TrimSuffix(fspath, "/")
456 fi, err := fs.Stat(fspath)
457 if os.IsNotExist(err) {
458 w.WriteHeader(http.StatusNoContent)
460 } else if err != nil {
461 s3ErrorResponse(w, InternalError, err.Error(), r.URL.Path, http.StatusInternalServerError)
463 } else if !fi.IsDir() {
464 // if "foo" exists and is a file, then
465 // "foo/" doesn't exist, so we say
466 // delete was successful.
467 w.WriteHeader(http.StatusNoContent)
470 } else if fi, err := fs.Stat(fspath); err == nil && fi.IsDir() {
471 // if "foo" is a dir, it is visible via S3
472 // only as "foo/", not "foo" -- so we leave
473 // the dir alone and return 204 to indicate
474 // that "foo" does not exist.
475 w.WriteHeader(http.StatusNoContent)
478 err = fs.Remove(fspath)
479 if os.IsNotExist(err) {
480 w.WriteHeader(http.StatusNoContent)
484 err = fmt.Errorf("rm failed: %w", err)
485 s3ErrorResponse(w, InvalidArgument, err.Error(), r.URL.Path, http.StatusBadRequest)
490 err = fmt.Errorf("sync failed: %w", err)
491 s3ErrorResponse(w, InternalError, err.Error(), r.URL.Path, http.StatusInternalServerError)
494 // Ensure a subsequent read operation will see the changes.
495 h.Config.Cache.ResetSession(token)
496 w.WriteHeader(http.StatusNoContent)
499 s3ErrorResponse(w, InvalidRequest, "method not allowed", r.URL.Path, http.StatusMethodNotAllowed)
504 // Call fn on the given path (directory) and its contents, in
505 // lexicographic order.
507 // If isRoot==true and path is not a directory, return nil.
509 // If fn returns filepath.SkipDir when called on a directory, don't
510 // descend into that directory.
511 func walkFS(fs arvados.CustomFileSystem, path string, isRoot bool, fn func(path string, fi os.FileInfo) error) error {
513 fi, err := fs.Stat(path)
514 if os.IsNotExist(err) || (err == nil && !fi.IsDir()) {
516 } else if err != nil {
520 if err == filepath.SkipDir {
522 } else if err != nil {
526 f, err := fs.Open(path)
527 if os.IsNotExist(err) && isRoot {
529 } else if err != nil {
530 return fmt.Errorf("open %q: %w", path, err)
536 fis, err := f.Readdir(-1)
540 sort.Slice(fis, func(i, j int) bool { return fis[i].Name() < fis[j].Name() })
541 for _, fi := range fis {
542 err = fn(path+"/"+fi.Name(), fi)
543 if err == filepath.SkipDir {
545 } else if err != nil {
549 err = walkFS(fs, path+"/"+fi.Name(), false, fn)
558 var errDone = errors.New("done")
560 func (h *handler) s3list(bucket string, w http.ResponseWriter, r *http.Request, fs arvados.CustomFileSystem) {
567 params.delimiter = r.FormValue("delimiter")
568 params.marker = r.FormValue("marker")
569 if mk, _ := strconv.ParseInt(r.FormValue("max-keys"), 10, 64); mk > 0 && mk < s3MaxKeys {
570 params.maxKeys = int(mk)
572 params.maxKeys = s3MaxKeys
574 params.prefix = r.FormValue("prefix")
576 bucketdir := "by_id/" + bucket
577 // walkpath is the directory (relative to bucketdir) we need
578 // to walk: the innermost directory that is guaranteed to
579 // contain all paths that have the requested prefix. Examples:
580 // prefix "foo/bar" => walkpath "foo"
581 // prefix "foo/bar/" => walkpath "foo/bar"
582 // prefix "foo" => walkpath ""
583 // prefix "" => walkpath ""
584 walkpath := params.prefix
585 if cut := strings.LastIndex(walkpath, "/"); cut >= 0 {
586 walkpath = walkpath[:cut]
591 type commonPrefix struct {
594 type listResp struct {
595 XMLName string `xml:"http://s3.amazonaws.com/doc/2006-03-01/ ListBucketResult"`
597 // s3.ListResp marshals an empty tag when
598 // CommonPrefixes is nil, which confuses some clients.
599 // Fix by using this nested struct instead.
600 CommonPrefixes []commonPrefix
601 // Similarly, we need omitempty here, because an empty
602 // tag confuses some clients (e.g.,
603 // github.com/aws/aws-sdk-net never terminates its
605 NextMarker string `xml:"NextMarker,omitempty"`
606 // ListObjectsV2 has a KeyCount response field.
610 ListResp: s3.ListResp{
612 Prefix: params.prefix,
613 Delimiter: params.delimiter,
614 Marker: params.marker,
615 MaxKeys: params.maxKeys,
618 commonPrefixes := map[string]bool{}
619 err := walkFS(fs, strings.TrimSuffix(bucketdir+"/"+walkpath, "/"), true, func(path string, fi os.FileInfo) error {
620 if path == bucketdir {
623 path = path[len(bucketdir)+1:]
624 filesize := fi.Size()
629 if len(path) <= len(params.prefix) {
630 if path > params.prefix[:len(path)] {
631 // with prefix "foobar", walking "fooz" means we're done
634 if path < params.prefix[:len(path)] {
635 // with prefix "foobar", walking "foobag" is pointless
636 return filepath.SkipDir
638 if fi.IsDir() && !strings.HasPrefix(params.prefix+"/", path) {
639 // with prefix "foo/bar", walking "fo"
640 // is pointless (but walking "foo" or
641 // "foo/bar" is necessary)
642 return filepath.SkipDir
644 if len(path) < len(params.prefix) {
645 // can't skip anything, and this entry
646 // isn't in the results, so just
651 if path[:len(params.prefix)] > params.prefix {
652 // with prefix "foobar", nothing we
653 // see after "foozzz" is relevant
657 if path < params.marker || path < params.prefix {
660 if fi.IsDir() && !h.Config.cluster.Collections.S3FolderObjects {
661 // Note we don't add anything to
662 // commonPrefixes here even if delimiter is
663 // "/". We descend into the directory, and
664 // return a commonPrefix only if we end up
665 // finding a regular file inside it.
668 if params.delimiter != "" {
669 idx := strings.Index(path[len(params.prefix):], params.delimiter)
671 // with prefix "foobar" and delimiter
672 // "z", when we hit "foobar/baz", we
673 // add "/baz" to commonPrefixes and
675 commonPrefixes[path[:len(params.prefix)+idx+1]] = true
676 return filepath.SkipDir
679 if len(resp.Contents)+len(commonPrefixes) >= params.maxKeys {
680 resp.IsTruncated = true
681 if params.delimiter != "" {
682 resp.NextMarker = path
686 resp.Contents = append(resp.Contents, s3.Key{
688 LastModified: fi.ModTime().UTC().Format("2006-01-02T15:04:05.999") + "Z",
693 if err != nil && err != errDone {
694 http.Error(w, err.Error(), http.StatusInternalServerError)
697 if params.delimiter != "" {
698 resp.CommonPrefixes = make([]commonPrefix, 0, len(commonPrefixes))
699 for prefix := range commonPrefixes {
700 resp.CommonPrefixes = append(resp.CommonPrefixes, commonPrefix{prefix})
702 sort.Slice(resp.CommonPrefixes, func(i, j int) bool { return resp.CommonPrefixes[i].Prefix < resp.CommonPrefixes[j].Prefix })
704 resp.KeyCount = len(resp.Contents)
705 w.Header().Set("Content-Type", "application/xml")
706 io.WriteString(w, xml.Header)
707 if err := xml.NewEncoder(w).Encode(resp); err != nil {
708 ctxlog.FromContext(r.Context()).WithError(err).Error("error writing xml response")