Fixed: Only send supported image data to calibre

src/NzbDrone.Core/Books/Calibre/CalibreImageValidator.cs

@@ -0,0 +1,66 @@
+using System;
+using System.Linq;
+using System.Text;
+
+namespace NzbDrone.Core.Books.Calibre
+{
+    // see https://github.com/kovidgoyal/calibre/blob/876290c600b26d6ce915c5449c641d98053b9037/src/calibre/utils/imghdr.py#L16
+    public static class CalibreImageValidator
+    {
+        private static readonly byte[] JFIF = Encoding.ASCII.GetBytes("JFIF");
+        private static readonly byte[] EXIF = Encoding.ASCII.GetBytes("Exif");
+        private static readonly byte[] BIM = Encoding.ASCII.GetBytes("8BIM");
+        private static readonly byte[] JPEG_MARKER = new byte[] { 255, 216 };
+
+        private static readonly byte[] GIF87 = Encoding.ASCII.GetBytes("GIF87a");
+        private static readonly byte[] GIF89 = Encoding.ASCII.GetBytes("GIF89a");
+
+        private static readonly byte[] PNG = new byte[] { 137, 80, 78, 71, 13, 10, 26, 10  };
+
+        public static bool IsValidImage(byte[] data)
+        {
+            //jpeg
+            var jpegRange = data.Skip(6).Take(4);
+
+            if (jpegRange.SequenceEqual(JFIF) ||
+                jpegRange.SequenceEqual(EXIF))
+            {
+                return true;
+            }
+
+            if (data.Take(2).SequenceEqual(JPEG_MARKER))
+            {
+                for (var i = 0; i < 28; i++)
+                {
+                    var sub = data.Skip(i).Take(4);
+                    if (sub.SequenceEqual(JFIF) || sub.SequenceEqual(BIM))
+                    {
+                        return true;
+                    }
+                }
+            }
+
+            // png
+            if (data.Take(8).SequenceEqual(PNG))
+            {
+                return true;
+            }
+
+            // gif (not supported by calibre)
+            var gifRange = data.Take(6);
+            if (gifRange.SequenceEqual(GIF87) ||
+                gifRange.SequenceEqual(GIF89))
+            {
+                return false;
+            }
+
+            // last ditch jpeg
+            if (data.Take(2).SequenceEqual(JPEG_MARKER))
+            {
+                return true;
+            }
+
+            return false;
+        }
+    }
+}

src/NzbDrone.Core/Books/Calibre/CalibreProxy.cs

@@ -177,7 +177,10 @@ namespace NzbDrone.Core.Books.Calibre
                 if (File.Exists(imageFile))
                 {
                     var imageData = File.ReadAllBytes(imageFile);
-                    image = Convert.ToBase64String(imageData);
+                    if (CalibreImageValidator.IsValidImage(imageData))
+                    {
+                        image = Convert.ToBase64String(imageData);
+                    }
                 }
             }