From 8837f3e95cffe5fb1774321816d6bf1c72a06c0d Mon Sep 17 00:00:00 2001
From: antiduh <antiduh@e114e3f1-24f7-e311-a78f-001bfcf5e160>
Date: Tue, 24 Jun 2014 22:51:38 +0000
Subject: [PATCH] Implemented CERs for encryption and decryption.

---
 Contexts/Context.cs              | 83 +++++++++++++++++++++++++-------
 Contexts/ContextNativeMethods.cs |  4 +-
 2 files changed, 69 insertions(+), 18 deletions(-)

diff --git a/Contexts/Context.cs b/Contexts/Context.cs
index ab74bba..4dbfa1e 100644
--- a/Contexts/Context.cs
+++ b/Contexts/Context.cs
@@ -5,6 +5,7 @@ using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
 
 namespace NSspi
 {
@@ -89,7 +90,7 @@ namespace NSspi
             SecureBuffer paddingBuffer;
             SecureBufferAdapter adapter;
 
-            SecurityStatus status;
+            SecurityStatus status = SecurityStatus.InvalidHandle;
             byte[] result;
 
             trailerBuffer = new SecureBuffer( new byte[sizes.SecurityTrailer], BufferType.Token );
@@ -100,13 +101,37 @@ namespace NSspi
 
             using( adapter = new SecureBufferAdapter( new[] { trailerBuffer, dataBuffer, paddingBuffer } ) )
             {
-                // TODO SAFE_CER
-                status = ContextNativeMethods.EncryptMessage(
-                    ref this.ContextHandle.rawHandle,
-                    0,
-                    adapter.Handle,
-                    0
-                );
+                bool gotRef = false;
+
+                RuntimeHelpers.PrepareConstrainedRegions();
+                try
+                {
+                    this.ContextHandle.DangerousAddRef( ref gotRef );
+                }
+                catch( Exception )
+                {
+                    if( gotRef )
+                    {
+                        this.ContextHandle.DangerousRelease();
+                        gotRef = false;
+                    }
+
+                    throw;
+                }
+                finally
+                {
+                    if( gotRef )
+                    {
+                        status = ContextNativeMethods.EncryptMessage(
+                            ref this.ContextHandle.rawHandle,
+                            0,
+                            adapter.Handle,
+                            0
+                        );
+
+                        this.ContextHandle.DangerousRelease();
+                    }
+                }
             }
 
             if( status != SecurityStatus.OK )
@@ -152,8 +177,8 @@ namespace NSspi
             SecureBuffer dataBuffer;
             SecureBuffer paddingBuffer;
             SecureBufferAdapter adapter;
-            
-            SecurityStatus status;
+
+            SecurityStatus status = SecurityStatus.InvalidHandle;
             byte[] result = null;
             int remaining;
             int position;
@@ -217,13 +242,37 @@ namespace NSspi
 
             using( adapter = new SecureBufferAdapter( new [] { trailerBuffer, dataBuffer, paddingBuffer } ) )
             {
-                // TODO SAFE_CER
-                status = ContextNativeMethods.DecryptMessage(
-                    ref this.ContextHandle.rawHandle,
-                    adapter.Handle,
-                    0,
-                    0
-                );
+                bool gotRef = false;
+
+                RuntimeHelpers.PrepareConstrainedRegions();
+                try
+                {
+                    this.ContextHandle.DangerousAddRef( ref gotRef );
+                }
+                catch( Exception )
+                {
+                    if( gotRef )
+                    {
+                        this.ContextHandle.DangerousRelease();
+                        gotRef = false;
+                    }
+
+                    throw;
+                }
+                finally
+                {
+                    if( gotRef )
+                    {
+                        status = ContextNativeMethods.DecryptMessage(
+                            ref this.ContextHandle.rawHandle,
+                            adapter.Handle,
+                            0,
+                            0
+                        );
+
+                        this.ContextHandle.DangerousRelease();
+                    }
+                }
             }
 
             if( status != SecurityStatus.OK )
diff --git a/Contexts/ContextNativeMethods.cs b/Contexts/ContextNativeMethods.cs
index ef5bf47..c6375a7 100644
--- a/Contexts/ContextNativeMethods.cs
+++ b/Contexts/ContextNativeMethods.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Runtime.ConstrainedExecution;
 using System.Runtime.InteropServices;
 using System.Text;
 using System.Threading.Tasks;
@@ -105,6 +106,7 @@ namespace NSspi
         public static extern SecurityStatus DeleteSecurityContext( ref RawSspiHandle contextHandle );
 
 
+        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail )]
         [DllImport( "Secur32.dll", EntryPoint = "EncryptMessage", CharSet = CharSet.Unicode )]
         public static extern SecurityStatus EncryptMessage(
             ref RawSspiHandle contextHandle,
@@ -113,7 +115,7 @@ namespace NSspi
             int sequenceNumber
         );
 
-
+        [ReliabilityContract( Consistency.WillNotCorruptState, Cer.MayFail )]
         [DllImport( "Secur32.dll", EntryPoint = "DecryptMessage", CharSet = CharSet.Unicode )]
         public static extern SecurityStatus DecryptMessage(
             ref RawSspiHandle contextHandle,