C# Registry SetValue throws UnauthorizedAccessException

Question

Before you try to answer this with, "Do a quick Google search." I'd like to point out that I have already. Here is the situation, I have the following method that attempts to modify a registry key value. The problem I'm getting is that when executed, it throws an UnauthorizedAccessException even though I've opened the key as writeable. I'm running Visual Studio as administrator and even tried to make a small .exe with a manifest file forcing it to run as admin that will execute the code with no luck. The key already exists, it doesn't try to go into the CreateKey method. Here is the block of code.

Path = "S-1-5-21-1644491937-1078145449-682003330-5490\Software\Microsoft\Windows\CurrentVersion\Policies\System"
Key = "DisableTaskMgr"
NewValue = 1

public OperationResult ModifyKey()
    {
        OperationResult result = new OperationResult();

        if (!Path.IsNullOrEmptyTrim())
        {
            if (!Key.IsNullOrEmptyTrim())
            {
                try
                {
                    var key = Microsoft.Win32.Registry.Users.OpenSubKey(Path, true);

                    if (key != null)
                    {
                        key.SetValue(Key, NewValue);

                        key.Close();
                    }
                    else
                    {
                        result = CreateKey();
                    }
                }
                catch (Exception ex)
                {
                    result.SetFail("Error accessing registry", ex);
                }
            }
            else
            {
                result.SetFail("Registry key was null");
            }
        }
        else
        {
            result.SetFail("Registry path was null");
        }

        return result;
    }

Do I have to manually walk down the registry tree setting each OpenSubKey call to writeable? I tried this as well, still threw the same error...

Answer 1

in the var for your key

var key = Microsoft.Win32.Registry.Users.OpenSubKey(Path, true);

change to

var key = Microsoft.Win32.Registry.Users.OpenSubKey(Path, RegistryKeyPermissionCheck.ReadWriteSubTree);  

Answer 2

One possible issue that I see with your code is that the Path variable is being set to a string that doesn't escape the \ characters. How about something like:

Path = @"S-1-5-21-1644491937-1078145449-682003330-5490\Software\Microsoft\Windows\CurrentVersion\Policies\System";

Answer 3

Have you tried setting the accessrule and permissions?

 string user = Environment.UserDomainName + "\\" + Environment.UserName
        RegistryAccessRule rule = new RegistryAccessRule(user,
        RegistryRights.FullControl,
        AccessControlType.Allow);        
        RegistrySecurity security = new RegistrySecurity();
        security.AddAccessRule(rule);
        var key = Microsoft.Win32.Registry.Users.OpenSubKey(Path, RegistryKeyPermissionCheck.ReadWriteSubTree, RegistryRights.FullControl);
        key.SetAccessControl(security);

Answer 4

As a last ditch effort to figure out what was going on, I created a simple service to test this code that will run as the local system account. It's the highest privileges I could think of to try and run the code with. Running the code with these permissions worked.

Special thanks go out to 0_____0 and Charleh for pointing out the anti-virus as well. I checked the logs and it turns out it was trying to quarantine my changes. I guess even it won't stop the System user from making these changes though.

Special thanks go out to Sorceri as well for helping me research this so much.

In conclusion, if you're having intermittent, extremely odd behavior, check your virus scanner and permissions.

Answer 5

Only set grants to dword. You must to open Registry and at the last folder path, rigth click over it and set Grants, and select All Aplications and check Total Control. I hope to help you.

Answer 6

just Registry.SetValue(sub_key, key, value);

Example:

Registry.SetValue(
            @"HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run",
            "MyApp",
            Application.ExecutablePath);