From 1bdd96e657c20d367a82b8197d3a46660e8c6496 Mon Sep 17 00:00:00 2001
From: atom0s <atom0s@live.com>
Date: Sun, 24 Apr 2022 21:34:23 -0700
Subject: [PATCH] * Unpacker v2.1 (x86) - Updated the header to handle the
 StubData more correctly.

---
 .../Classes/SteamStubHeader.cs                 | 18 ++++++++++++++----
 Steamless.Unpacker.Variant21.x86/Main.cs       | 18 ++++++++++++++++++
 2 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/Steamless.Unpacker.Variant21.x86/Classes/SteamStubHeader.cs b/Steamless.Unpacker.Variant21.x86/Classes/SteamStubHeader.cs
index 9199612..0857670 100644
--- a/Steamless.Unpacker.Variant21.x86/Classes/SteamStubHeader.cs
+++ b/Steamless.Unpacker.Variant21.x86/Classes/SteamStubHeader.cs
@@ -54,8 +54,13 @@ namespace Steamless.Unpacker.Variant21.x86.Classes
         public uint SteamDRMPDllSize; // The offset inside of the payload data holding the size of the SteamDRMP.dll file data.
         public uint XTeaKeys; // The offset inside of the payload data holding the address to the Xtea keys to decrypt the SteamDRMP.dll file.
 
-        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 0x2B8)]
-        public byte[] StubData; // Misc stub data, such as strings, error messages, etc.
+        //
+        // The 'StubData' field is dynamically sized based on the needs of the stub version and used options. This is effectively
+        // impossible to 'size' correctly for all header versions, so instead it will be treated separately.
+        //
+        // [MarshalAs(UnmanagedType.ByValArray, SizeConst = ???)]
+        // public byte[] StubData; // Misc stub data, such as strings, error messages, etc.
+        //
     }
 
     /// <summary>
@@ -84,7 +89,12 @@ namespace Steamless.Unpacker.Variant21.x86.Classes
         public uint SteamDRMPDllSize; // The offset inside of the payload data holding the size of the SteamDRMP.dll file data.
         public uint XTeaKeys; // The offset inside of the payload data holding the address to the Xtea keys to decrypt the SteamDRMP.dll file.
 
-        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 0x31C)]
-        public byte[] StubData; // Misc stub data, such as strings, error messages, etc.
+        //
+        // The 'StubData' field is dynamically sized based on the needs of the stub version and used options. This is effectively
+        // impossible to 'size' correctly for all header versions, so instead it will be treated separately.
+        //
+        // [MarshalAs(UnmanagedType.ByValArray, SizeConst = ???)]
+        // public byte[] StubData; // Misc stub data, such as strings, error messages, etc.
+        //
     }
 }
\ No newline at end of file
diff --git a/Steamless.Unpacker.Variant21.x86/Main.cs b/Steamless.Unpacker.Variant21.x86/Main.cs
index df4cedf..d00bad6 100644
--- a/Steamless.Unpacker.Variant21.x86/Main.cs
+++ b/Steamless.Unpacker.Variant21.x86/Main.cs
@@ -187,6 +187,13 @@ namespace Steamless.Unpacker.Variant21.x86
         /// <returns></returns>
         private bool Step1()
         {
+            /**
+             * Note: This version of the stub has a variable length header due to how it builds the 
+             * header information. When the stub is generated, the header has additional string data
+             * that can be dynamically built based on the various options of the protection being used
+             * and other needed API imports. Inside of the stub header, this field is 'StubData'.
+             */
+
             // Obtain the file entry offset..
             var fileOffset = this.File.GetFileOffsetFromRva(this.File.NtHeaders.OptionalHeader.AddressOfEntryPoint);
 
@@ -207,9 +214,15 @@ namespace Steamless.Unpacker.Variant21.x86
 
             // Determine how to handle the header based on the size..
             if ((structSize / 4) == 0xD0)
+            {
                 this.StubHeader = Pe32Helpers.GetStructure<SteamStub32Var21Header_D0Variant>(headerData);
+                this.StubData = headerData.Skip(Marshal.SizeOf(typeof(SteamStub32Var21Header_D0Variant))).ToArray();
+            }
             else
+            {
                 this.StubHeader = Pe32Helpers.GetStructure<SteamStub32Var21Header>(headerData);
+                this.StubData = headerData.Skip(Marshal.SizeOf(typeof(SteamStub32Var21Header))).ToArray();
+            }
 
             return true;
         }
@@ -755,6 +768,11 @@ namespace Steamless.Unpacker.Variant21.x86
         /// </summary>
         private dynamic StubHeader { get; set; }
 
+        /// <summary>
+        /// Gets or sets the dynamic field 'StubData' from the header.
+        /// </summary>
+        private byte[] StubData { get; set; }
+
         /// <summary>
         /// Gets or sets the payload data.
         /// </summary>