Prevent image decode panics, handle errors gracefully

cache-images.go

@@ -142,26 +142,12 @@ func cacheImage(imageURL, imageID string, imageType string) (string, bool, error
 		return cachedImagePath, true, nil
 	}
 
-	// Decode the image based on the content type
+	// Decode image
-	var img image.Image
+	img, err := safeDecodeImage(contentType, data)
-	switch contentType {
+	if err != nil {
-	case "image/x-icon", "image/vnd.microsoft.icon":
+		printErr("Failed to decode favicon: %s [%s] (%v)", imageURL, imageID, err)
-		img, err = ico.Decode(bytes.NewReader(data))
-	case "image/jpeg":
-		img, err = jpeg.Decode(bytes.NewReader(data))
-	case "image/png":
-		img, err = png.Decode(bytes.NewReader(data))
-	case "image/gif":
-		img, err = gif.Decode(bytes.NewReader(data))
-	case "image/webp":
-		img, err = webp.Decode(bytes.NewReader(data))
-	case "image/bmp":
-		img, err = bmp.Decode(bytes.NewReader(data))
-	case "image/tiff":
-		img, err = tiff.Decode(bytes.NewReader(data))
-	default:
 		recordInvalidImageID(imageID)
-		return "", false, fmt.Errorf("unsupported image type: %s", contentType)
+		return "", false, err
 	}
 
 	if err != nil {
@@ -522,6 +508,33 @@ func cleanupCache() {
 	}
 }
 
+func safeDecodeImage(contentType string, data []byte) (img image.Image, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			err = fmt.Errorf("image decode panic: %v", r)
+		}
+	}()
+	switch contentType {
+	case "image/x-icon", "image/vnd.microsoft.icon":
+		img, err = ico.Decode(bytes.NewReader(data))
+	case "image/jpeg":
+		img, err = jpeg.Decode(bytes.NewReader(data))
+	case "image/png":
+		img, err = png.Decode(bytes.NewReader(data))
+	case "image/gif":
+		img, err = gif.Decode(bytes.NewReader(data))
+	case "image/webp":
+		img, err = webp.Decode(bytes.NewReader(data))
+	case "image/bmp":
+		img, err = bmp.Decode(bytes.NewReader(data))
+	case "image/tiff":
+		img, err = tiff.Decode(bytes.NewReader(data))
+	default:
+		err = fmt.Errorf("unsupported image type: %s", contentType)
+	}
+	return
+}
+
 // Serve missing.svg
 func serveMissingImage(w http.ResponseWriter, r *http.Request) {
 	missingImagePath := filepath.Join("static", "images", "missing.svg")

favicon.go

@@ -1,16 +1,12 @@
 package main
 
 import (
-	"bytes"
 	"crypto/md5"
 	"crypto/tls"
 	"encoding/base64"
 	"encoding/hex"
 	"fmt"
 	"image"
-	"image/gif"
-	"image/jpeg"
-	"image/png"
 	"io"
 	"net/http"
 	"net/url"
@@ -21,10 +17,7 @@ import (
 	"time"
 
 	"github.com/chai2010/webp"
-	"github.com/fyne-io/image/ico"
-	"golang.org/x/image/bmp"
 	"golang.org/x/image/draw"
-	"golang.org/x/image/tiff"
 	"golang.org/x/net/html"
 )
 
@@ -504,28 +497,9 @@ func cacheFavicon(imageURL, imageID string) (string, bool, error) {
 	}
 
 	// Decode image
-	var img image.Image
+	img, err := safeDecodeImage(contentType, data)
-	var err error
-	switch contentType {
-	case "image/x-icon", "image/vnd.microsoft.icon":
-		img, err = ico.Decode(bytes.NewReader(data))
-	case "image/jpeg":
-		img, err = jpeg.Decode(bytes.NewReader(data))
-	case "image/png":
-		img, err = png.Decode(bytes.NewReader(data))
-	case "image/gif":
-		img, err = gif.Decode(bytes.NewReader(data))
-	case "image/webp":
-		img, err = webp.Decode(bytes.NewReader(data))
-	case "image/bmp":
-		img, err = bmp.Decode(bytes.NewReader(data))
-	case "image/tiff":
-		img, err = tiff.Decode(bytes.NewReader(data))
-	default:
-		recordInvalidImageID(imageID)
-		return "", false, fmt.Errorf("unsupported image type: %s", contentType)
-	}
 	if err != nil {
+		printErr("Failed to decode favicon: %s [%s] (%v)", imageURL, imageID, err)
 		recordInvalidImageID(imageID)
 		return "", false, err
 	}