From 4c3c6e757ce7da4baed8fb31ac16bc6392adec11 Mon Sep 17 00:00:00 2001
From: atom0s <atom0s@live.com>
Date: Sun, 28 May 2023 02:07:05 -0700
Subject: [PATCH] API: (PE32) Adjusted 'Parse' method to exit early if the DOS
 stub is invalid. (Avoids attempting to read an invalid NT header block.) API:
 (PE64) Adjusted 'Parse' method to exit early if the DOS stub is invalid.
 (Avoids attempting to read an invalid NT header block.)

---
 Steamless.API/PE32/Pe32File.cs | 10 ++++++----
 Steamless.API/PE64/Pe64File.cs | 10 ++++++----
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/Steamless.API/PE32/Pe32File.cs b/Steamless.API/PE32/Pe32File.cs
index 1d849dc..b33259c 100644
--- a/Steamless.API/PE32/Pe32File.cs
+++ b/Steamless.API/PE32/Pe32File.cs
@@ -85,12 +85,14 @@ namespace Steamless.API.PE32
             if (this.FileData.Length < (Marshal.SizeOf(typeof(NativeApi32.ImageDosHeader32)) + Marshal.SizeOf(typeof(NativeApi32.ImageNtHeaders32))))
                 return false;
 
-            // Read the file headers..
+            // Read the file DOS header..
             this.DosHeader = Pe32Helpers.GetStructure<NativeApi32.ImageDosHeader32>(this.FileData);
-            this.NtHeaders = Pe32Helpers.GetStructure<NativeApi32.ImageNtHeaders32>(this.FileData, this.DosHeader.e_lfanew);
+            if (!this.DosHeader.IsValid)
+                return false;
 
-            // Validate the headers..
-            if (!this.DosHeader.IsValid || !this.NtHeaders.IsValid)
+            // Read the file NT headers..
+            this.NtHeaders = Pe32Helpers.GetStructure<NativeApi32.ImageNtHeaders32>(this.FileData, this.DosHeader.e_lfanew);
+            if (!this.NtHeaders.IsValid)
                 return false;
 
             // Read and store the dos header if it exists..
diff --git a/Steamless.API/PE64/Pe64File.cs b/Steamless.API/PE64/Pe64File.cs
index 366e0a2..a586b43 100644
--- a/Steamless.API/PE64/Pe64File.cs
+++ b/Steamless.API/PE64/Pe64File.cs
@@ -85,12 +85,14 @@ namespace Steamless.API.PE64
             if (this.FileData.Length < (Marshal.SizeOf(typeof(NativeApi64.ImageDosHeader64)) + Marshal.SizeOf(typeof(NativeApi64.ImageNtHeaders64))))
                 return false;
 
-            // Read the file headers..
+            // Read the file DOS header..
             this.DosHeader = Pe64Helpers.GetStructure<NativeApi64.ImageDosHeader64>(this.FileData);
-            this.NtHeaders = Pe64Helpers.GetStructure<NativeApi64.ImageNtHeaders64>(this.FileData, this.DosHeader.e_lfanew);
+            if (!this.DosHeader.IsValid)
+                return false;
 
-            // Validate the headers..
-            if (!this.DosHeader.IsValid || !this.NtHeaders.IsValid)
+            // Read the file NT headers..
+            this.NtHeaders = Pe64Helpers.GetStructure<NativeApi64.ImageNtHeaders64>(this.FileData, this.DosHeader.e_lfanew);
+            if (!this.NtHeaders.IsValid)
                 return false;
 
             // Read and store the dos header if it exists..