CERs around the handle usage in MakeSignature and VerifySignature

Contexts/Context.cs

@@ -279,13 +279,37 @@ namespace NSspi.Contexts
 
             using ( adapter = new SecureBufferAdapter( new[] { dataBuffer, signatureBuffer } ) )
             {
-                // TODO CER
+                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.MakeSignature(
                             ref this.ContextHandle.rawHandle,
                             0,
                             adapter.Handle,
                             0
                         );
+
+                        this.ContextHandle.DangerousRelease();
+                    }
+                }
             }
 
             if ( status != SecurityStatus.OK )
@@ -359,6 +383,27 @@ namespace NSspi.Contexts
             position += sigLen;
 
             using ( adapter = new SecureBufferAdapter( new[] { dataBuffer, signatureBuffer } ) )
+            {
+                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.VerifySignature(
                             ref this.ContextHandle.rawHandle,
@@ -366,6 +411,10 @@ namespace NSspi.Contexts
                             0,
                             0
                         );
+
+                        this.ContextHandle.DangerousRelease();
+                    }
+                }
             }
 
             if ( status == SecurityStatus.OK )