Add compound file magic header validation

Author: emako

QuickLook.Plugin/QuickLook.Plugin.ArchiveViewer/CompoundFileBinary/CompoundFileExtractor.cs

@@ -18,6 +18,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 using System.Runtime.InteropServices.ComTypes;
 
 namespace QuickLook.Plugin.ArchiveViewer.CompoundFileBinary;
@@ -42,6 +43,22 @@ public static void ExtractToDirectory(string compoundFilePath, string destinatio
             Directory.CreateDirectory(destinationDirectory);
         }
 
+        // Ensure the compound file exists
+        if (!File.Exists(compoundFilePath))
+            throw new FileNotFoundException("Compound file not found.", compoundFilePath);
+
+        // Validate magic header for OLE compound file: D0 CF 11 E0 A1 B1 1A E1
+        byte[] magicHeader = [0xD0, 0xCF, 0x11, 0xE0, 0xA1, 0xB1, 0x1A, 0xE1];
+        byte[] header = new byte[8];
+        using (FileStream fs = new(compoundFilePath, FileMode.Open, FileAccess.Read, FileShare.Read))
+        {
+            int read = fs.Read(header, 0, header.Length);
+            if (read < header.Length || !header.SequenceEqual(magicHeader))
+            {
+                throw new InvalidDataException("The specified file does not appear to be an OLE Compound File (invalid header).");
+            }
+        }
+
         // Open the compound file as an IStorage implementation wrapped by DisposableIStorage.
         using DisposableIStorage storage = new(compoundFilePath, STGM.DIRECT | STGM.READ | STGM.SHARE_EXCLUSIVE, IntPtr.Zero);
         IEnumerator<STATSTG> enumerator = storage.EnumElements();