Unity: Allow version selection from asset file

Il2CppInspector.CLI/Program.cs

@@ -109,6 +109,9 @@ namespace Il2CppInspector.CLI
             [Option("unity-version", Required = false, HelpText = "Version of Unity used to create the input files, if known. Used to enhance Python, C++ and JSON output. If not specified, a close match will be inferred automatically.", Default = null)]
             public UnityVersion UnityVersion { get; set; }
 
+            [Option("unity-version-from-asset", Required = false, HelpText = "A Unity asset file used to determine the exact Unity version. Overrides --unity-version.", Default = null)]
+            public string UnityVersionAsset { get; set; }
+
             [Option("plugins", Required = false, HelpText = "Specify options for plugins. Enclose each plugin's configuration in quotes as follows: --plugins \"pluginone --option1 value1 --option2 value2\" \"plugintwo --option...\". Use --plugins <name> to get help on a specific plugin")]
             public IEnumerable<string> PluginOptions { get; set; }
         }
@@ -192,6 +195,21 @@ namespace Il2CppInspector.CLI
                 }
             }
 
+            // Check Unity asset
+            if (options.UnityVersionAsset != null) {
+                try {
+                    options.UnityVersion = UnityVersion.FromAssetFile(options.UnityVersionAsset);
+
+                    Console.WriteLine("Unity asset file has version " + options.UnityVersion);
+                }
+                catch (FileNotFoundException) {
+                    Console.Error.WriteLine($"Unity asset file {options.UnityVersionAsset} does not exist");
+                    return 1;
+                } catch (ArgumentException) {
+                    Console.Error.WriteLine("Could not determine Unity version from asset file - ignoring");
+                }
+            }
+
             // Check excluded namespaces
             if (options.ExcludedNamespaces.Count() == 1 && options.ExcludedNamespaces.First().ToLower() == "none")
                 options.ExcludedNamespaces = new List<string>();

Il2CppInspector.Common/Cpp/UnityHeaders/UnityVersion.cs

@@ -6,8 +6,11 @@
 */
 
 using System;
+using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Text.RegularExpressions;
+using NoisyCowStudios.Bin2Object;
 
 namespace Il2CppInspector.Cpp.UnityHeaders
 {
@@ -65,6 +68,26 @@ namespace Il2CppInspector.Cpp.UnityHeaders
             BuildNumber = match.Groups[5].Success ? int.Parse(match.Groups[5].Value) : 0;
         }
 
+        // Get a Unity version from a Unity asset file
+        public static UnityVersion FromAssetFile(string filePath) {
+            // Don't use BinaryObjectStream because we'd have to read the entire file into memory
+            using var file = File.Open(filePath, FileMode.Open, FileAccess.Read, FileShare.Read);
+            using var reader = new BinaryReader(file, System.Text.Encoding.UTF8);
+
+            // Position of Unity version string in asset files
+            file.Position = 0x14;
+
+            // Read null-terminated string
+            var bytes = new List<byte>();
+            var maxLength = 15;
+            byte b;
+            while ((b = reader.ReadByte()) != 0 && bytes.Count < maxLength)
+                bytes.Add(b);
+
+            var unityString = System.Text.Encoding.UTF8.GetString(bytes.ToArray());
+            return new UnityVersion(unityString);
+        }
+
         public static implicit operator UnityVersion(string versionString) => new UnityVersion(versionString);
 
         public override string ToString() {

Il2CppInspector.GUI/MainWindow.xaml

@@ -113,6 +113,9 @@
                     <Label Grid.Row="8" Grid.Column="1" Content="{Binding Path=Binary.RegistrationFunctionPointer}" ContentStringFormat="0x{0:x8}"></Label>
                 </Grid>
                 
+                <!-- Unity asset file button -->
+                <Button Name="btnUnityAsset" Click="BtnUnityAsset_Click" DockPanel.Dock="Top" Margin="10" Padding="5" HorizontalAlignment="Left" VerticalAlignment="Top" FontSize="14" Width="260" Content="Get Unity version from asset file..." Style="{StaticResource LightBoxButton}"/>
+
                 <!-- Save file buttons -->
                 <Button Name="btnSaveMetadata" Click="BtnSaveMetadata_OnClick" DockPanel.Dock="Top" Margin="10" Padding="5" HorizontalAlignment="Left" VerticalAlignment="Top" FontSize="14" Width="260" Content="Save extracted/decrypted metadata...">
                     <Button.Style>

Il2CppInspector.GUI/MainWindow.xaml.cs

@@ -212,6 +212,42 @@ namespace Il2CppInspectorGUI
             ((App) Application.Current).ResetLoadOptions();
         }
 
+        /// <summary>
+        /// Select Unity version from asset file
+        /// </summary>
+        private void BtnUnityAsset_Click(object sender, RoutedEventArgs e) {
+            var openFileDialog = new OpenFileDialog {
+                Filter = "Unity asset files (*.*)|*.*",
+                CheckFileExists = true
+            };
+
+            if (openFileDialog.ShowDialog() != true)
+                return;
+
+            try {
+                var unityVersion = UnityVersion.FromAssetFile(openFileDialog.FileName);
+
+                var done = false;
+                foreach (UnityHeaders header in cboPyUnityVersion.Items) {
+                    if (header.VersionRange.Contains(unityVersion)) {
+                        cboPyUnityVersion.SelectedItem = header;
+                        cboCppUnityVersion.SelectedItem = header;
+                        cboJsonUnityVersion.SelectedItem = header;
+                        done = true;
+                        break;
+                    }
+                }
+
+                if (done)
+                    MessageBox.Show(this, $"Selected Unity version {unityVersion}", "Unity version detected", MessageBoxButton.OK, MessageBoxImage.Information);
+                else
+                    MessageBox.Show(this, $"Asset file Unity version {unityVersion} is not compatible with the loaded IL2CPP application", "Incompatible Unity version", MessageBoxButton.OK, MessageBoxImage.Error);
+            }
+            catch (ArgumentException) {
+                MessageBox.Show(this, "Could not determine Unity version from this asset file", "Unity version could not be detected", MessageBoxButton.OK, MessageBoxImage.Error);
+            }
+        }
+
         /// <summary>
         /// User has selected an image
         /// </summary>

README.md

@@ -208,6 +208,8 @@ File format and architecture are automatically detected.
 
   --unity-version             Version of Unity used to create the input files, if known. Used to enhance Python, C++ and JSON output. If not specified, a close match will be inferred automatically.
 
+  --unity-version-from-asset  A Unity asset file used to determine the exact Unity version. Overrides --unity-version.
+
   --plugins                   Specify options for plugins. Enclose each plugin's configuration in quotes as follows: --plugins "pluginone --option1 value1 --option2 value2" "plugintwo --option...". Use --plugins <name> to get help on a specific plugin
 
   --help                      Display this help screen.
@@ -280,7 +282,7 @@ Simply run Il2CppInspector with the `-p` switch to choose the IDA script output
 
 Three files are generated by Il2CppInspector for IDAPython: the Python script itself, a JSON metadata file and a C++ type header file (this is `cpp/appdata/il2cpp-types.h` by default if you used the CLI, or `il2cpp.h` if you used the GUI). These files must be present for the script to run successfully.
 
-If you know which version of Unity the binary was compiled with, you can improve the output by specifying this with `--unity-version`, for example `--unity-version 2019.3.1f1`. Otherwise Il2CppInspector will make an educated guess based on the contents of the binary.
+If you know which version of Unity the binary was compiled with, you can improve the output by specifying this with `--unity-version`, for example `--unity-version 2019.3.1f1`. You can also supply any asset file from the application to detect the Unity version with `--unity-version-from-asset`. Otherwise Il2CppInspector will make an educated guess based on the contents of the binary.
 
 Il2CppInspector generates the following data for IDA projects:
 
@@ -308,7 +310,7 @@ Run Il2CppInspector with the `-p` switch to choose the Ghidra script output file
 
 Three files are generated by Il2CppInspector for Ghidra: the Python script itself, a JSON metadata file and a C++ type header file. These files must be present for the script to run successfully.
 
-If you know which version of Unity the binary was compiled with, you can improve the output by specifying this with `--unity-version`, for example `--unity-version 2019.3.1f1`. Otherwise Il2CppInspector will make an educated guess based on the contents of the binary.
+If you know which version of Unity the binary was compiled with, you can improve the output by specifying this with `--unity-version`, for example `--unity-version 2019.3.1f1`. You can also supply any asset file from the application to detect the Unity version with `--unity-version-from-asset`. Otherwise Il2CppInspector will make an educated guess based on the contents of the binary.
 
 **NOTE:** For best results, choose No when Ghidra asks if you would like to perform auto-analysis when the binary is first loaded. If you receive a `Conflicting data exists at address` error when running the script below, re-load the binary into the project and choose No at the auto-analysis prompt.
 
@@ -346,7 +348,7 @@ Il2CppInspector generates a series of C++ source files which you can use in a va
 
 Run Il2CppInspector with the `-h` switch to choose the C++ output folder.
 
-If you know which version of Unity the binary was compiled with, you can improve the output by specifying this with `--unity-version`, for example `--unity-version 2019.3.1f1`. Otherwise Il2CppInspector will make an educated guess based on the contents of the binary.
+If you know which version of Unity the binary was compiled with, you can improve the output by specifying this with `--unity-version`, for example `--unity-version 2019.3.1f1`. You can also supply any asset file from the application to detect the Unity version with `--unity-version-from-asset`. Otherwise Il2CppInspector will make an educated guess based on the contents of the binary.
 
 You can target which C++ compiler you wish to use the output files with: specify `--cpp-compiler MSVC` for Visual Studio and `--cpp-compiler GCC` for gcc or clang.