Accessing 64 bit registry from a 32 bit process

As you may know, Windows is virtualizing some parts of the registry under 64 bit. So if you try to open, for example, this key : “HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\90″, from a 32 bit C# application running on a 6

As you may know, Windows is virtualizing some parts of the registry under 64 bit.

So if you try to open, for example, this key : “HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\90″, from a 32 bit C# application running on a 64 bit system, you will be redirected to : “HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Microsoft SQL Server\90″

Why ? Because Windows uses the Wow6432Node registry entry to present a separate view of HKEY_LOCAL_MACHINE\SOFTWARE for 32 bit applications that runs on a 64 bit systems.

If you want to explicitly open the 64 bit view of the registry, here is what you have to perform :

You are using VS 2010 and version 4.x of the .NET framework

It’s really simple, all you need to do is, instead of doing :

//will redirect you to the 32 bit view

RegistryKey sqlsrvKey = Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Microsoft\Microsoft SQL Server\90");

do the following :

RegistryKey localMachineX64View = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, RegistryView.Registry64);

RegistryKey sqlsrvKey = localMachineX64View.OpenSubKey(@"SOFTWARE\Microsoft\Microsoft SQL Server\90");

Prior versions of the .NET framework

For the prior versions of the framework, we have to use P/Invoke and call the function RegOpenKeyExW with parameter KEY_WOW64_64KEY

enum RegWow64Options

{

    None = 0,

    KEY_WOW64_64KEY = 0x0100,

    KEY_WOW64_32KEY = 0x0200

}

enum RegistryRights

{

    ReadKey = 131097,

    WriteKey = 131078

}

/// <summary></summary>

/// Open a registry key using the Wow64 node instead of the default 32-bit node.

///

/// <param name="parentKey">Parent key to the key to be opened.

/// <param name="subKeyName">Name of the key to be opened

/// <param name="writable">Whether or not this key is writable

/// <param name="options">32-bit node or 64-bit node

/// <returns></returns>

static RegistryKey _openSubKey(RegistryKey parentKey, string subKeyName, bool writable, RegWow64Options options)

{

    //Sanity check

    if (parentKey == null || _getRegistryKeyHandle(parentKey) == IntPtr.Zero)

    {

        return null;

    }

    //Set rights

    int rights = (int)RegistryRights.ReadKey;

    if (writable)

        rights = (int)RegistryRights.WriteKey;

    //Call the native function >.

    int subKeyHandle, result = RegOpenKeyEx(_getRegistryKeyHandle(parentKey), subKeyName, 0, rights | (int)options, out subKeyHandle);

    //If we errored, return null

    if (result != 0)

    {

        return null;

    }

    //Get the key represented by the pointer returned by RegOpenKeyEx

    RegistryKey subKey = _pointerToRegistryKey((IntPtr)subKeyHandle, writable, false);

    return subKey;

}

/// <summary></summary>

/// Get a pointer to a registry key.

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///

/// <param name="registryKey">Registry key to obtain the pointer of.

/// <returns>Pointer to the given registry key.</returns>

static IntPtr _getRegistryKeyHandle(RegistryKey registryKey)

{

    //Get the type of the RegistryKey

    Type registryKeyType = typeof(RegistryKey);

    //Get the FieldInfo of the 'hkey' member of RegistryKey

    System.Reflection.FieldInfo fieldInfo =

    registryKeyType.GetField("hkey", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);

    //Get the handle held by hkey

    SafeHandle handle = (SafeHandle)fieldInfo.GetValue(registryKey);

    //Get the unsafe handle

    IntPtr dangerousHandle = handle.DangerousGetHandle();

    return dangerousHandle;

}

/// <summary></summary>

/// Get a registry key from a pointer.

///

/// <param name="hKey">Pointer to the registry key

/// <param name="writable">Whether or not the key is writable.

/// <param name="ownsHandle">Whether or not we own the handle.

/// <returns>Registry key pointed to by the given pointer.</returns>

static RegistryKey _pointerToRegistryKey(IntPtr hKey, bool writable, bool ownsHandle)

{

    //Get the BindingFlags for private contructors

    System.Reflection.BindingFlags privateConstructors = System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic;

    //Get the Type for the SafeRegistryHandle

    Type safeRegistryHandleType = typeof(Microsoft.Win32.SafeHandles.SafeHandleZeroOrMinusOneIsInvalid).Assembly.GetType("Microsoft.Win32.SafeHandles.SafeRegistryHandle");

    //Get the array of types matching the args of the ctor we want

    Type[] safeRegistryHandleCtorTypes = new Type[] { typeof(IntPtr), typeof(bool) };

    //Get the constructorinfo for our object

    System.Reflection.ConstructorInfo safeRegistryHandleCtorInfo = safeRegistryHandleType.GetConstructor(

    privateConstructors, null, safeRegistryHandleCtorTypes, null);

    //Invoke the constructor, getting us a SafeRegistryHandle

    Object safeHandle = safeRegistryHandleCtorInfo.Invoke(new Object[] { hKey, ownsHandle });

    //Get the type of a RegistryKey

    Type registryKeyType = typeof(RegistryKey);

    //Get the array of types matching the args of the ctor we want

    Type[] registryKeyConstructorTypes = new Type[] { safeRegistryHandleType, typeof(bool) };

    //Get the constructorinfo for our object

    System.Reflection.ConstructorInfo registryKeyCtorInfo = registryKeyType.GetConstructor(

    privateConstructors, null, registryKeyConstructorTypes, null);

    //Invoke the constructor, getting us a RegistryKey

    RegistryKey resultKey = (RegistryKey)registryKeyCtorInfo.Invoke(new Object[] { safeHandle, writable });

    //return the resulting key

    return resultKey;

}

[DllImport("advapi32.dll", CharSet = CharSet.Auto)]

public static extern int RegOpenKeyEx(IntPtr hKey, string subKey, int ulOptions, int samDesired, out int phkResult);

Then we can open our registry key like this :

RegistryKey sqlsrvKey = _openSubKey(Registry.LocalMachine, @"SOFTWARE\Microsoft\Microsoft SQL Server\90", false, RegWow64Options.KEY_WOW64_64KEY);

As you can see, the framework 4 make our life easier.

Referenced from: http://dotnetgalactics.wordpress.com/2010/05/10/accessing-64-bit-registry-from-a-32-bit-process/