Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.ServiceModel/System/ServiceModel/Activation/Iis7Helper.cs

@@ -0,0 +1,62 @@
+//----------------------------------------------------------------------------
+// Copyright (c) Microsoft Corporation.  All rights reserved.
+//----------------------------------------------------------------------------
+
+namespace System.ServiceModel.Activation
+{
+    using System.Runtime;
+    using System.Security;
+    using System.Security.Permissions;
+    using Microsoft.Win32;
+
+    static class Iis7Helper
+    {
+        static int iisVersion;
+        static bool isIis7;
+
+        static Iis7Helper()
+        {
+            isIis7 = GetIsIis7();
+        }
+
+        internal static int IisVersion
+        {
+            get { return iisVersion; }
+        }
+
+        internal static bool IsIis7
+        {
+            get { return isIis7; }
+        }
+
+        [Fx.Tag.SecurityNote(Critical = "Uses SecurityCritical method to get version info from registry.",
+            Safe = "Processes registry info into a safe bool for return.")]
+        [SecuritySafeCritical]
+        static bool GetIsIis7()
+        {
+            iisVersion = -1;
+            object majorVersion = UnsafeGetMajorVersionFromRegistry();
+            if (majorVersion != null && majorVersion.GetType().Equals(typeof(int)))
+            {
+                iisVersion = (int)majorVersion;
+            }
+            return iisVersion >= 7;
+        }
+
+        const string subKey = @"Software\Microsoft\InetSTP";
+
+        [Fx.Tag.SecurityNote(Critical = "Asserts registry access to get a single value from the registry, caller should not leak value.")]
+        [SecurityCritical]
+        [RegistryPermission(SecurityAction.Assert, Read = @"HKEY_LOCAL_MACHINE\" + subKey)]
+        static object UnsafeGetMajorVersionFromRegistry()
+        {
+            using (RegistryKey localMachine = Registry.LocalMachine)
+            {
+                using (RegistryKey versionKey = localMachine.OpenSubKey(subKey))
+                {
+                    return versionKey != null ? versionKey.GetValue("MajorVersion") : null;
+                }
+            }
+        }
+    }
+}