admin: view images and PDFs inline in the file browser (#9751)

The viewer embedded images and PDFs through the download URL, which sent
Content-Disposition: attachment, so the browser downloaded them instead of
rendering. Add an inline mode to the download endpoint, limited to images and
PDFs so a hostile upload (HTML, SVG) can't run as same-origin script, set
X-Content-Type-Options: nosniff, and resolve the MIME the same way the viewer
does. The viewer now requests the inline URL.

weed/admin/handlers/file_browser_grpc.go

@@ -9,8 +9,10 @@ import (
 	"net/http"
 	"path"
 	"strconv"
+	"strings"
 	"time"
 
+	"github.com/seaweedfs/seaweedfs/weed/admin/dash"
 	"github.com/seaweedfs/seaweedfs/weed/filer"
 	"github.com/seaweedfs/seaweedfs/weed/glog"
 	"github.com/seaweedfs/seaweedfs/weed/operation"
@@ -67,7 +69,7 @@ func (h *FileBrowserHandlers) fetchFileContentGrpc(ctx context.Context, filePath
 // response writer receives the canonical attachment headers and the raw
 // bytes; this replaces the HTTP-to-filer proxy that used to run in
 // DownloadFile.
-func (h *FileBrowserHandlers) downloadFileGrpc(ctx context.Context, filePath string, w http.ResponseWriter) error {
+func (h *FileBrowserHandlers) downloadFileGrpc(ctx context.Context, filePath string, w http.ResponseWriter, inline bool) error {
 	cleanFilePath, err := h.validateAndCleanFilePath(filePath)
 	if err != nil {
 		return err
@@ -84,16 +86,19 @@ func (h *FileBrowserHandlers) downloadFileGrpc(ctx context.Context, filePath str
 	size := int64(filer.FileSize(entry))
 
 	fileName := path.Base(cleanFilePath)
-	w.Header().Set("Content-Disposition", mime.FormatMediaType("attachment", map[string]string{"filename": fileName}))
 
-	contentType := ""
-	if entry.Attributes != nil {
-		contentType = entry.Attributes.Mime
-	}
-	if contentType == "" {
-		contentType = "application/octet-stream"
+	// Resolve mime like the viewer does so Content-Type and the inline check agree.
+	contentType := dash.ResolveEntryMime(entry)
+
+	// Only inline images and PDFs; serve the rest as attachments so a hostile upload
+	// (HTML, SVG) can't run as same-origin script. nosniff locks the declared type.
+	disposition := "attachment"
+	if inline && (strings.HasPrefix(contentType, "image/") || contentType == "application/pdf") {
+		disposition = "inline"
 	}
+	w.Header().Set("Content-Disposition", mime.FormatMediaType(disposition, map[string]string{"filename": fileName}))
 	w.Header().Set("Content-Type", contentType)
+	w.Header().Set("X-Content-Type-Options", "nosniff")
 	w.Header().Set("Content-Length", strconv.FormatInt(size, 10))
 	w.WriteHeader(http.StatusOK)
 

weed/admin/handlers/file_browser_handlers.go

@@ -397,8 +397,9 @@ func (h *FileBrowserHandlers) DownloadFile(w http.ResponseWriter, r *http.Reques
 		writeJSONError(w, http.StatusBadRequest, "File path is required")
 		return
 	}
+	inline := r.URL.Query().Get("inline") == "true"
 	tracker := &responseWriteTracker{ResponseWriter: w}
-	if err := h.downloadFileGrpc(r.Context(), filePath, tracker); err != nil {
+	if err := h.downloadFileGrpc(r.Context(), filePath, tracker, inline); err != nil {
 		// Once bytes have been written we can't switch to a JSON error body
 		// without corrupting the partial response — log and stop. Before any
 		// write the response is still uncommitted, so a 502 with details is

weed/admin/static/js/admin.js

@@ -1788,7 +1788,7 @@ function createFileViewerContent(file, content) {
     if (file.mime.startsWith('image/')) {
         return `
             <div class="text-center">
-                <img src="${basePath('/api/files/download?path=' + encodeURIComponent(file.full_path))}"
+                <img src="${basePath('/api/files/download?path=' + encodeURIComponent(file.full_path) + '&inline=true')}"
                      class="img-fluid" alt="${file.name}" style="max-height: 500px;">
             </div>
         `;
@@ -1806,7 +1806,7 @@ function createFileViewerContent(file, content) {
     } else if (file.mime === 'application/pdf') {
         return `
             <div class="text-center">
-                <embed src="${basePath('/api/files/download?path=' + encodeURIComponent(file.full_path))}"
+                <embed src="${basePath('/api/files/download?path=' + encodeURIComponent(file.full_path) + '&inline=true')}"
                        type="application/pdf" width="100%" height="500px">
             </div>
         `;