Try to decrypt files inside FPK archives if they begin with 0x1B or 0x1C

emoose · Sep 30, 2015 · a136f02 · a136f02
1 parent f884ec6
commit a136f02
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Showing 2 changed files with 31 additions and 2 deletions.
diff --git a/GzsTool/Fpk/FpkEntry.cs b/GzsTool/Fpk/FpkEntry.cs
@@ -75,11 +75,40 @@ private Func<Stream> ReadDataLazy(Stream input)
             };
         }
 
+        private bool DecryptCryptedFile(byte[] fileData, string filePath, out byte[] decryptedData)
+        {
+            var filename = Path.GetFileName(filePath);
+            var hash = Hashing.HashFileNameLegacy(filename, false);
+            var key = BitConverter.GetBytes(~hash);
+
+            var decData = new byte[fileData.Length - 1];
+
+            for (int i = 0; i < fileData.Length - 1; i++)
+            {
+                key[i & 7] ^= fileData[i + 1];
+                decData[i] = key[i & 7];
+            }
+
+            var success = decData[decData.Length - 1] == 0;
+            if (!success)
+            {
+                decryptedData = fileData;
+                return false;
+            }
+
+            Array.Resize(ref decData, decData.Length - 1);
+            decryptedData = decData;
+            return true;
+        }
+
         private Stream ReadData(Stream input)
         {
             input.Position = DataOffset;
             byte[] result = new byte[DataSize];
             input.Read(result, 0, (int)DataSize);
+            if (result[0] == 0x1B || result[0] == 0x1C)
+                DecryptCryptedFile(result, GetFpkEntryFileName(), out result);
+
             return new MemoryStream(result);
         }
 

diff --git a/GzsTool/Utility/Hashing.cs b/GzsTool/Utility/Hashing.cs
@@ -279,7 +279,7 @@ private static ulong HashFileExtension(string fileExtension)
             return HashFileName(fileExtension, false) & 0x1FFF;
         }
 
-        private static ulong HashFileName(string text, bool removeExtension = true)
+        public static ulong HashFileName(string text, bool removeExtension = true)
         {
             if (removeExtension)
             {
@@ -305,7 +305,7 @@ private static ulong HashFileName(string text, bool removeExtension = true)
             return setFlag ? maskedHash | 0x4000000000000 : maskedHash;
         }
 
-        private static ulong HashFileNameLegacy(string text, bool removeExtension = true)
+        public static ulong HashFileNameLegacy(string text, bool removeExtension = true)
         {
             if (removeExtension)
             {