From e1741d06f79a18aedc461a5188df5357be9275ef Mon Sep 17 00:00:00 2001
From: morkt <morkt@users.noreply.github.com>
Date: Thu, 7 Sep 2023 12:20:36 +0400
Subject: [PATCH] (Unity): decrypt Utage data.dsm script.

---
 ArcFormats/Unity/ScriptDSM.cs | 87 +++++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)
 create mode 100644 ArcFormats/Unity/ScriptDSM.cs

diff --git a/ArcFormats/Unity/ScriptDSM.cs b/ArcFormats/Unity/ScriptDSM.cs
new file mode 100644
index 00000000..4254a350
--- /dev/null
+++ b/ArcFormats/Unity/ScriptDSM.cs
@@ -0,0 +1,87 @@
+//! \file       ScriptDSM.cs
+//! \date       2023 Sep 03
+//! \brief      Decrypt data.dsm script.
+//
+// Copyright (C) 2023 by morkt
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to
+// deal in the Software without restriction, including without limitation the
+// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+// sell copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+// IN THE SOFTWARE.
+//
+
+using System;
+using System.ComponentModel.Composition;
+using System.IO;
+using System.Security.Cryptography;
+using System.Text;
+
+namespace GameRes.Formats.NScripter
+{
+    [Export(typeof(ScriptFormat))]
+    public class DsmConverter : GenericScriptFormat
+    {
+        public override string         Tag { get => "DSM/UTAGE"; }
+        public override string Description { get => "UTAGE Unity engine script file"; }
+        public override uint     Signature { get => 0; }
+
+        public override bool IsScript (IBinaryStream file)
+        {
+            return VFS.IsPathEqualsToFileName (file.Name, "data.dsm");
+        }
+
+        public override Stream ConvertFrom (IBinaryStream file)
+        {
+            using (var reader = new StreamReader (file.AsStream))
+            {
+                var sourceString = reader.ReadToEnd();
+                var text = DsmDecryptor.DecryptString (sourceString, "pass");
+                return new BinMemoryStream (text, file.Name);
+            }
+        }
+        
+        public override Stream ConvertBack (IBinaryStream file)
+        {
+            throw new NotSupportedException();
+        }
+    }
+
+    internal static class DsmDecryptor
+    {
+        internal static void GenerateKeyFromPassword (string password, int keySize, out byte[] key, int blockSize, out byte[] iv)
+        {
+            var bytes = Encoding.UTF8.GetBytes ("saltは必ず8バイト以上");
+            var derive = new Rfc2898DeriveBytes (password, bytes);
+            derive.IterationCount = 1000;
+            key = derive.GetBytes (keySize / 8);
+            iv = derive.GetBytes (blockSize / 8);
+        }
+
+        internal static byte[] DecryptString (string sourceString, string password)
+        {
+            var rij = new RijndaelManaged();
+            byte[] key, iv;
+            GenerateKeyFromPassword (password, rij.KeySize, out key, rij.BlockSize, out iv);
+            rij.Key = key;
+            rij.IV = iv;
+            var array = Convert.FromBase64String (sourceString);
+            using (var cryptoTransform = rij.CreateDecryptor())
+            {
+                return cryptoTransform.TransformFinalBlock (array, 0, array.Length);
+            }
+        }
+    }
+}