Use a mutex to guard cert creation on windows (#11546)

- It should prevent some test flakyness around importing certs in some cases.

src/Servers/Kestrel/shared/test/TestResources.cs

@@ -1,8 +1,12 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.IO;
+using System.Runtime.InteropServices;
 using System.Security.Cryptography.X509Certificates;
+using System.Threading;
+using Xunit;
 
 namespace Microsoft.AspNetCore.Testing
 {
@@ -13,14 +17,28 @@ namespace Microsoft.AspNetCore.Testing
         public static string TestCertificatePath { get; } = Path.Combine(_baseDir, "testCert.pfx");
         public static string GetCertPath(string name) => Path.Combine(_baseDir, name);
 
-        public static X509Certificate2 GetTestCertificate()
+        private const int MutexTimeout = 120 * 1000;
-        {
+        private static readonly Mutex importPfxMutex = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ?
-            return new X509Certificate2(TestCertificatePath, "testPassword");
+            new Mutex(initiallyOwned: false, "Global\\KestrelTests.Certificates.LoadPfxCertificate") :
-        }
+            null;
 
-        public static X509Certificate2 GetTestCertificate(string certName)
+        public static X509Certificate2 GetTestCertificate(string certName = "testCert.pfx")
         {
-            return new X509Certificate2(GetCertPath(certName), "testPassword");
+            // On Windows, applications should not import PFX files in parallel to avoid a known system-level
+            // race condition bug in native code which can cause crashes/corruption of the certificate state.
+            if (importPfxMutex != null)
+            {
+                Assert.True(importPfxMutex.WaitOne(MutexTimeout), "Cannot acquire the global certificate mutex.");
+            }
+
+            try
+            {
+                return new X509Certificate2(GetCertPath(certName), "testPassword");
+            }
+            finally
+            {
+                importPfxMutex?.ReleaseMutex();
+            }
         }
     }
 }