media: never project zero image/video dimensions (crashes Telegram Desktop on reactions)

internal/rpc/convert_media.go

@@ -353,6 +353,11 @@ func tgPhotoSizes(sizes []domain.PhotoSize) []tg.PhotoSizeClass {
 func tgPhotoSize(s domain.PhotoSize) tg.PhotoSizeClass {
 	switch s.Kind {
 	case domain.PhotoSizeKindDefault:
+		if s.W <= 0 || s.H <= 0 {
+			// A zero-dimension photoSize is malformed and divides to a crash on
+			// the client; dropping it lets clients fall back to another size.
+			return nil
+		}
 		return &tg.PhotoSize{Type: s.Type, W: s.W, H: s.H, Size: s.Size}
 	case domain.PhotoSizeKindStripped:
 		return &tg.PhotoStrippedSize{Type: s.Type, Bytes: s.Bytes}
@@ -450,12 +455,47 @@ func compactPhotoSizeClasses(in []tg.PhotoSizeClass) []tg.PhotoSizeClass {
 	return out
 }
 
+// stickerCanvasSize is the square canvas a sticker / custom emoji is laid out on.
+// It is the fallback dimension when stored metadata carries a zero, which clients
+// divide by while sizing the render (a 0 there crashes Telegram Desktop).
+const stickerCanvasSize = 512
+
+func stickerLikeMime(mimeType string) bool {
+	switch mimeType {
+	case mimeApplicationXTGSticker, "image/webp", "video/webm":
+		return true
+	default:
+		return false
+	}
+}
+
+// safeMediaDimension replaces a non-positive width/height with a usable value:
+// the sticker canvas for sticker-like documents, otherwise 1, so no projected
+// attribute ever carries a zero a client would divide by.
+func safeMediaDimension(v int, mimeType string) int {
+	if v > 0 {
+		return v
+	}
+	if stickerLikeMime(mimeType) {
+		return stickerCanvasSize
+	}
+	return 1
+}
+
 func tgDocumentAttributes(mimeType string, attrs []domain.DocumentAttribute) []tg.DocumentAttributeClass {
 	out := make([]tg.DocumentAttributeClass, 0, len(attrs))
 	for _, a := range attrs {
 		switch a.Kind {
 		case domain.DocAttrImageSize:
-			out = append(out, &tg.DocumentAttributeImageSize{W: a.W, H: a.H})
+			if (a.W <= 0 || a.H <= 0) && !stickerLikeMime(mimeType) {
+				// Malformed size on a plain image: drop it rather than emit a zero.
+				// Clients cope with a missing imageSize; a zero one crashes them.
+				continue
+			}
+			out = append(out, &tg.DocumentAttributeImageSize{
+				W: safeMediaDimension(a.W, mimeType),
+				H: safeMediaDimension(a.H, mimeType),
+			})
 		case domain.DocAttrAnimated:
 			if mimeType == mimeApplicationXTGSticker {
 				continue
@@ -473,8 +513,8 @@ func tgDocumentAttributes(mimeType string, attrs []domain.DocumentAttribute) []t
 				SupportsStreaming: a.SupportsStreaming,
 				Nosound:           a.NoSound,
 				Duration:          a.Duration,
-				W:                 a.W,
-				H:                 a.H,
+				W:                 safeMediaDimension(a.W, mimeType),
+				H:                 safeMediaDimension(a.H, mimeType),
 			}
 			if a.VideoCodec != "" {
 				video.SetVideoCodec(a.VideoCodec)

internal/rpc/stickers_test.go

@@ -721,6 +721,64 @@ func TestTGDocumentDoesNotEmitAnimatedAttributeForTGSSticker(t *testing.T) {
 	}
 }
 
+func TestTGDocumentNeverEmitsZeroImageOrVideoDimensions(t *testing.T) {
+	// A sticker / custom emoji whose stored metadata carries a zero dimension
+	// must not reach the client as documentAttributeImageSize#0 -- Telegram
+	// Desktop divides by it and crashes when the emoji is used as a reaction.
+	sticker := tgDocument(domain.Document{
+		ID: 100, AccessHash: 1, DCID: 2, MimeType: "application/x-tgsticker",
+		Attributes: []domain.DocumentAttribute{
+			{Kind: domain.DocAttrImageSize, W: 0, H: 0},
+			{Kind: domain.DocAttrCustomEmoji, Alt: "🙂", StickerSetID: 10, StickerSetAccessHash: 20},
+		},
+	}).(*tg.Document)
+	var gotImage bool
+	for _, attr := range sticker.Attributes {
+		if a, ok := attr.(*tg.DocumentAttributeImageSize); ok {
+			gotImage = true
+			if a.W != 512 || a.H != 512 {
+				t.Fatalf("sticker imageSize = %dx%d, want 512x512 fallback", a.W, a.H)
+			}
+		}
+	}
+	if !gotImage {
+		t.Fatal("sticker lost its imageSize attribute entirely")
+	}
+
+	video := tgDocument(domain.Document{
+		ID: 101, AccessHash: 1, DCID: 2, MimeType: "video/webm",
+		Attributes: []domain.DocumentAttribute{
+			{Kind: domain.DocAttrVideo, W: 0, H: 0, Duration: 3},
+			{Kind: domain.DocAttrSticker, Alt: "😀", StickerSetID: 10, StickerSetAccessHash: 20},
+		},
+	}).(*tg.Document)
+	for _, attr := range video.Attributes {
+		if a, ok := attr.(*tg.DocumentAttributeVideo); ok && (a.W <= 0 || a.H <= 0) {
+			t.Fatalf("video sticker attribute has zero dimension: %+v", a)
+		}
+	}
+
+	// A malformed plain image drops the attribute rather than emitting a zero.
+	plain := tgDocument(domain.Document{
+		ID: 102, AccessHash: 1, DCID: 2, MimeType: "image/jpeg",
+		Attributes: []domain.DocumentAttribute{{Kind: domain.DocAttrImageSize, W: 0, H: 480}},
+	}).(*tg.Document)
+	for _, attr := range plain.Attributes {
+		if _, ok := attr.(*tg.DocumentAttributeImageSize); ok {
+			t.Fatalf("plain image kept a malformed imageSize: %+v", attr)
+		}
+	}
+
+	// A zero-dimension thumbnail is dropped, not emitted.
+	thumbed := tgDocument(domain.Document{
+		ID: 103, AccessHash: 1, DCID: 2, MimeType: "image/webp",
+		Thumbs: []domain.PhotoSize{{Kind: domain.PhotoSizeKindDefault, Type: "s", W: 0, H: 0, Size: 10}},
+	}).(*tg.Document)
+	if len(thumbed.Thumbs) != 0 {
+		t.Fatalf("kept a zero-dimension thumb: %#v", thumbed.Thumbs)
+	}
+}
+
 func TestTGDocumentUsesDomainDocumentID(t *testing.T) {
 	const documentID int64 = 1382305375846410902