fix(artwork): only use image files as local artwork sources (#6180)

* fix(playlists): limit local cover paths to images in owner's libraries

A local #EXTALBUMARTURL path (absolute or file://) was only checked against the union of all
libraries. The artwork resolver then opened it with no further check and served the bytes as the
playlist cover, undecoded. Any user who can upload an M3U could read any file under any library
root, including libraries they were not granted, through getCoverArt (GHSA-vwq6-xrw5-phpg).

resolveImageURL now requires an image extension, and for uploaded playlists (no folder) the
library holding the cover must pass the owner's HasLibraryAccess. Scanner and CLI imports keep
the all-libraries check, since those files are admin-controlled.

resolveLocalFile, used by every file-backed artwork source, now ignores paths without an image
extension, which covers playlists stored before this fix that were not resolved yet. openOriginal
refuses a stored file-backed row whose path is not an image, so the existing dangling path
re-resolves it and the playlist falls back to the generated grid. No migration is needed.

* fix(artwork): skip non-image files matched by folder cover patterns

Album and disc folder sources opened any file in the folder's image list that matched a
cover pattern, without checking its extension. openOriginal now refuses to serve file-backed
rows whose path is not an image, so a stored row like that would be refused, re-resolved to
the same file, and refused again on every view. The list comes from the scanner, which only
records image files, but a database scanned where the OS mime table knows more image types
than the serving process could still reach this.

Both fromExternalFile variants now skip matches that are not image files, so the album falls
back to its next source instead. Also correct the parser comment: a playlist without a folder
can come from an API upload or from a CLI import of a file outside all libraries.

* fix(artwork): check stored source type before using the resize cache

The image-extension check for file-backed rows ran inside openOriginal, which the resize
cache skips on a hit. Before the fix, a resized request for a playlist pointing at a non-image
file cached the raw bytes, because a failed resize falls back to the original data. After the
upgrade the same request still hit that entry and returned the file.

serveHash now refuses a file-backed row whose path is not an image before calling serveSource,
so both full-size and resized requests go through dangling and re-resolve the item. The stale
cache entry is keyed by the old hash and is no longer reachable once the row changes.

* test: register mime_types.yaml in test binaries

Artwork resolution now skips candidates that are not image files, and model.IsImageFile answers
from the process mime table. The server registers the extra image types from
resources/mime_types.yaml through a conf hook, but a test binary only does that if it links
conf/mime, so the artwork e2e suite fell back to the host table: .jxl resolves on macOS and
Linux and does not on Windows, where the #5950 cover spec then found no source.

tests.Init now imports conf/mime for its side effect, so every suite that loads the test config
sees the same image types as the server.

* fix(artwork): drop the image-file guard from the disc art reader

The guard was added to both fromExternalFile variants, but disc artwork keeps no state row and
is never queued, so it cannot hit the refuse-and-re-resolve loop the guard exists to prevent.
The only case where it can fire is a real image whose extension this process's mime table does
not know, and there it drops a disc cover that used to work. The album variant keeps the guard,
since those resolutions are stored and re-served.

core/artwork/artwork.go

@@ -168,6 +168,11 @@ func (s *service) serveHash(ctx context.Context, artID model.ArtworkID, ia *mode
 	if !entityExists(ctx, s.ds, artID) {
 		return nil, ErrUnavailable
 	}
+	// Checked here, not in openOriginal: a resize-cache hit never opens the source.
+	if isFileBacked(ia.Source) && !model.IsImageFile(ia.SourcePath) {
+		log.Warn(ctx, "Artwork: Stored source is not an image file, re-resolving", "artID", artID, "path", ia.SourcePath)
+		return s.dangling(ctx, artID)
+	}
 	art, err := s.ds.Artwork(ctx).GetImage(ia.Hash)
 	if err != nil {
 		if errors.Is(err, model.ErrNotFound) {

core/artwork/artwork_test.go

@@ -159,6 +159,53 @@ var _ = Describe("Artwork", func() {
 			Expect(readAll(img)).To(Equal(coverBytes))
 		})
 
+		It("treats a file-backed row pointing at a non-image file as dangling", func() {
+			dir := GinkgoT().TempDir()
+			secretPath := filepath.Join(dir, "config.ini")
+			Expect(os.WriteFile(secretPath, []byte("password=secret"), 0600)).To(Succeed())
+			Expect(artRepo.PutImage(&model.Artwork{Hash: "dddddddddddddddd", Mime: "image/jpeg"})).To(Succeed())
+			seedEntity("al", "alni")
+			Expect(artRepo.PutItemArtwork(&model.ItemArtwork{
+				ItemKind: "al", ItemID: "alni", Hash: "dddddddddddddddd",
+				Source: "folder", SourcePath: secretPath, RefMtime: fileMtime(secretPath),
+			})).To(Succeed())
+
+			_, err := svc.Get(ctx, model.MustParseArtworkID("al-alni"), 0, false)
+			Expect(err).To(MatchError(ErrUnavailable))
+			Expect(queueRepo.Data[primaryKey("al", "alni")].Priority).To(Equal(model.ArtworkPriorityScan))
+		})
+
+		It("refuses a non-image file-backed row even when a resized copy is already cached", func() {
+			secret := []byte("password=secret")
+			dir := GinkgoT().TempDir()
+			secretPath := filepath.Join(dir, "config.ini")
+			Expect(os.WriteFile(secretPath, secret, 0600)).To(Succeed())
+			Expect(artRepo.PutImage(&model.Artwork{Hash: "eeeeeeeeeeeeeeee", Mime: "image/jpeg"})).To(Succeed())
+			seedEntity("al", "alnic")
+			Expect(artRepo.PutItemArtwork(&model.ItemArtwork{
+				ItemKind: "al", ItemID: "alnic", Hash: "eeeeeeeeeeeeeeee",
+				Source: "folder", SourcePath: secretPath, RefMtime: fileMtime(secretPath),
+			})).To(Succeed())
+
+			// Older versions cached the raw bytes when the resize failed.
+			seed := func() (io.ReadCloser, error) { return io.NopCloser(bytes.NewReader(secret)), nil }
+			stream, err := imgCache.Get(ctx, &resizedItem{hash: "eeeeeeeeeeeeeeee", size: 100, open: seed, ffmpeg: ffm})
+			Expect(err).ToNot(HaveOccurred())
+			Expect(io.ReadAll(stream)).To(Equal(secret))
+			Expect(stream.Close()).To(Succeed())
+			Eventually(func(g Gomega) {
+				s, err := imgCache.Get(ctx, &resizedItem{hash: "eeeeeeeeeeeeeeee", size: 100, ffmpeg: ffm,
+					open: func() (io.ReadCloser, error) { return nil, os.ErrNotExist }})
+				g.Expect(err).ToNot(HaveOccurred())
+				g.Expect(s.Cached).To(BeTrue())
+				_ = s.Close()
+			}).Should(Succeed())
+
+			_, err = svc.Get(ctx, model.MustParseArtworkID("al-alnic"), 100, false)
+			Expect(err).To(MatchError(ErrUnavailable))
+			Expect(queueRepo.Data[primaryKey("al", "alnic")].Priority).To(Equal(model.ArtworkPriorityScan))
+		})
+
 		It("treats a full-size mtime mismatch as dangling: unavailable, re-enqueued at Scan, state untouched", func() {
 			dir := GinkgoT().TempDir()
 			imgPath := filepath.Join(dir, "cover.jpg")

core/artwork/resolve.go

@@ -572,7 +572,7 @@ func resolveArtistFolderPattern(ctx context.Context, lib libraryView, artistFold
 // resolveLocalFile opens an absolute path directly. A missing path is "no source"; any other
 // open failure says nothing about whether the image exists.
 func resolveLocalFile(path, source string) (resolution, bool) {
-	if path == "" {
+	if path == "" || !model.IsImageFile(path) {
 		return resolution{}, false
 	}
 	f, err := os.Open(path)

core/artwork/resolve_test.go

@@ -498,6 +498,23 @@ var _ = Describe("resolveItem", func() {
 			Expect(res.refMtime).To(BeNumerically(">", 0))
 		})
 
+		It("never opens a local ExternalImageURL that is not an image file", func() {
+			folderRepo.result = nil // no grid tiles, so only the local file could produce a reader
+			dir := GinkgoT().TempDir()
+			secretPath := filepath.Join(dir, "config.ini")
+			Expect(os.WriteFile(secretPath, []byte("password=secret"), 0600)).To(Succeed())
+
+			plRepo := tests.CreateMockPlaylistRepo()
+			plRepo.SetData(model.Playlists{{ID: "plni", Name: "Playlist", ExternalImageURL: secretPath}})
+			plRepo.TracksRepo = &tests.MockPlaylistTrackRepo{AlbumIDs: []string{"t1"}}
+			ds.MockedPlaylist = plRepo
+
+			res, err := newResolver(ds, ag, ffm, nil).resolve(ctx, model.ArtworkQueueItem{ItemKind: "pl", ItemID: "plni"})
+			Expect(err).ToNot(HaveOccurred())
+			Expect(res.reader).To(BeNil())
+			Expect(res.sourcePath).ToNot(Equal(secretPath))
+		})
+
 		It("routes ExternalImageURL through extGate and sets extError on transient failure", func() {
 			conf.Server.EnableM3UExternalAlbumArt = true
 			folderRepo.result = nil // no grid tiles, so the external failure is what surfaces

core/artwork/sources.go

@@ -37,7 +37,7 @@ func fromExternalFile(ctx context.Context, libFS fs.FS, files []string, pattern
 				log.Warn(ctx, "Artwork: Error matching cover art file to pattern", "pattern", pattern, "file", file)
 				continue
 			}
-			if !match {
+			if !match || !model.IsImageFile(name) {
 				continue
 			}
 			f, err := libFS.Open(file)

core/artwork/sources_internal_test.go

@@ -48,6 +48,18 @@ var _ = Describe("fromExternalFile", func() {
 		Expect(b).To(Equal([]byte("a")))
 		Expect(path).To(Equal("a/cover.jpg"))
 	})
+
+	It("skips a matching file that is not an image", func() {
+		fsys := fstest.MapFS{
+			"a/cover.ini": &fstest.MapFile{Data: []byte("password=secret")},
+			"a/cover.jpg": &fstest.MapFile{Data: []byte("a")},
+		}
+		f := fromExternalFile(GinkgoT().Context(), fsys, []string{"a/cover.ini", "a/cover.jpg"}, "cover.*")
+		r, path, err := f()
+		Expect(err).ToNot(HaveOccurred())
+		defer r.Close()
+		Expect(path).To(Equal("a/cover.jpg"))
+	})
 })
 
 var _ = Describe("fromTag", func() {

core/playlists/import_test.go

@@ -236,6 +236,24 @@ var _ = Describe("Playlists - Import", func() {
 				Expect(pls.ExternalImageURL).To(BeEmpty())
 			})
 
+			It("rejects #EXTALBUMARTURL pointing at a non-image file inside the library", func() {
+				tmpDir := GinkgoT().TempDir()
+				Expect(os.WriteFile(filepath.Join(tmpDir, "config.ini"), []byte("password=secret"), 0600)).To(Succeed())
+
+				m3u := "#EXTALBUMARTURL:config.ini\ntest.mp3\n"
+				plsFile := filepath.Join(tmpDir, "test.m3u")
+				Expect(os.WriteFile(plsFile, []byte(m3u), 0600)).To(Succeed())
+
+				mockLibRepo.SetData([]model.Library{{ID: 1, Path: tmpDir}})
+				ds.MockedMediaFile = &mockedMediaFileFromListRepo{data: []string{"test.mp3"}}
+				ps = playlists.NewPlaylists(ds, artwork.NewUploader(ds))
+
+				plsFolder := &model.Folder{ID: "1", LibraryID: 1, LibraryPath: tmpDir, Path: "", Name: ""}
+				pls, err := ps.ImportFromFolder(ctx, plsFolder, "test.m3u")
+				Expect(err).ToNot(HaveOccurred())
+				Expect(pls.ExternalImageURL).To(BeEmpty())
+			})
+
 			It("ignores HTTP #EXTALBUMARTURL when EnableM3UExternalAlbumArt is false", func() {
 				conf.Server.EnableM3UExternalAlbumArt = false
 
@@ -1011,6 +1029,19 @@ var _ = Describe("Playlists - Import", func() {
 			Expect(pls.ExternalImageURL).To(BeEmpty())
 		})
 
+		DescribeTable("restricts a local #EXTALBUMARTURL to the owner's libraries",
+			func(imageURL, expected string) {
+				ctx = request.WithUser(ctx, model.User{ID: "123", Libraries: model.Libraries{{ID: 1, Path: "/music"}}})
+				repo.data = []string{"tests/test.mp3"}
+				m3u := "#EXTALBUMARTURL:" + imageURL + "\n/music/tests/test.mp3\n"
+				pls, err := ps.ImportM3U(ctx, strings.NewReader(m3u))
+				Expect(err).ToNot(HaveOccurred())
+				Expect(pls.ExternalImageURL).To(Equal(expected))
+			},
+			Entry("accepts a library the owner can access", "file:///music/cover.jpg", filepath.Clean("/music/cover.jpg")),
+			Entry("ignores a library the owner cannot access", "file:///new/cover.jpg", ""),
+		)
+
 		// Fullwidth characters (e.g., ＡＢＣＤ) are not handled by SQLite's NOCASE collation,
 		// so we need exact matching for non-ASCII characters.
 		It("matches fullwidth characters exactly (SQLite NOCASE limitation)", func() {

core/playlists/parse_m3u.go

@@ -14,6 +14,7 @@ import (
 	"github.com/navidrome/navidrome/conf"
 	"github.com/navidrome/navidrome/log"
 	"github.com/navidrome/navidrome/model"
+	"github.com/navidrome/navidrome/model/request"
 	"github.com/navidrome/navidrome/utils/slice"
 	"golang.org/x/text/unicode/norm"
 )
@@ -36,7 +37,8 @@ func (s *playlists) parseM3U(ctx context.Context, pls *model.Playlist, folder *m
 				continue
 			}
 			if after, ok := strings.CutPrefix(line, "#EXTALBUMARTURL:"); ok {
-				pls.ExternalImageURL = resolveImageURL(after, folder, resolver.matcher)
+				owner, _ := request.UserFrom(ctx)
+				pls.ExternalImageURL = resolveImageURL(after, folder, resolver.matcher, owner)
 				continue
 			}
 			// Skip empty lines and extended info
@@ -286,7 +288,7 @@ func (r *pathResolver) resolvePaths(ctx context.Context, folder *model.Folder, l
 // HTTP(S) URLs are stored as-is (gated by EnableM3UExternalAlbumArt).
 // Local paths (file://, absolute, or relative) are resolved to an absolute path
 // and validated against known library boundaries via matcher.
-func resolveImageURL(value string, folder *model.Folder, matcher *libraryMatcher) string {
+func resolveImageURL(value string, folder *model.Folder, matcher *libraryMatcher, owner model.User) string {
 	value = strings.TrimSpace(value)
 	if value == "" {
 		return ""
@@ -302,12 +304,13 @@ func resolveImageURL(value string, folder *model.Folder, matcher *libraryMatcher
 
 	// Resolve to local absolute path
 	localPath, ok := resolveLocalPath(value, folder)
-	if !ok {
+	if !ok || !model.IsImageFile(localPath) {
 		return ""
 	}
 
-	// Validate path is within a known library
-	if libID, _ := matcher.findLibraryForPath(localPath); libID == 0 {
+	lib, ok := matcher.findLibrary(localPath)
+	// A playlist without a folder (API upload, or CLI import from outside all libraries) may only use the owner's libraries.
+	if !ok || (folder == nil && !owner.HasLibraryAccess(lib.ID)) {
 		return ""
 	}
 	return localPath

tests/init_tests.go

@@ -8,6 +8,7 @@ import (
 	"testing"
 
 	"github.com/navidrome/navidrome/conf"
+	_ "github.com/navidrome/navidrome/conf/mime" // registers mime_types.yaml, so tests see the same image types as the server
 	"github.com/navidrome/navidrome/log"
 )