We need to change some settings to the HKEY_LOCAL_MACHINE at runtime.
Is it possible to prompt for uac elevation if needed at runtime, or do I have to launch a second elevated process to do 'the dirty work'?
We need to change some settings to the HKEY_LOCAL_MACHINE at runtime.
Is it possible to prompt for uac elevation if needed at runtime, or do I have to launch a second elevated process to do 'the dirty work'?
You can't "elevate" an existing process. Elevated processes under UAC have a different token with a different LUID, different mandatory integrity level, and different group membership. This level of change can't be done within a running process - and it would be a security problem if that could happen.
You need to launch a second process elevated that would do the work or by creating a COM object that runs in an elevated dllhost.
http://msdn.microsoft.com/en-us/library/bb756922.aspx gives an example "RunAsAdmin" function and a "CoCreateInstanceAsAdmin" function.
EDIT: I just saw "Delphi" in your title. Everything I listed is obviously native, but if Delphi provides access to ShellExecute-like functionality you should be able to adapt the code from the link.
A sample of ready-to-use code:
Usage example:
And support unit itself:
Usually, putting the text "Setup" or "Install" somewhere in your EXE name is enough to make Windows run with elevated privileges automatically, and is well worth doing if it is a setup utility you are writing, as it's so easy to do.
I am now running into problems though on Windows 7, when not logged in as an Administrator, and am having to use the right-click Run As Administrator when running manually (running the program via Wise installation wizard is still fine)
I see though that Delphi 10.1 Berlin has a very easy to use new option under Project Options | Application. Just tick Enable Administrator Privileges, and the manifest is done for you, so easy!
NB. make sure you only do these kind of changes via a separate setup program, running your application with elevated privileges all the time can cause problems with other things, for example e-mail, where the default mail profile no longer gets picked up.
Edit: Jan 2018: since writing this answer in August 2017, it seems a lot of Windows updates have come out, that now require the user to right-click and Run As Administrator on just about everything, even on installation exe's built with Wise. Even Outlook is no longer installing properly without running as administrator. There is no more automated elevation at all it seems.
i would relaunch yourself as elevated, passing command line parameters indicating what elevated thing you want to do. You can then jump right to the appropriate form, or just save your HKLM stuff.
The other Microsoft suggested solution is to create an COM object out of process (using the specially created CoCreateInstanceAsAdmin function). i don't like this idea because you have to write and register a COM object.
Note: There is no "CoCreateInstanceAsAdmin" API call. It's just some code floating around. Here's the Dephi version i stumbled around for. It is apparently based on the trick of prefixing a class guid string with the "Elevation:Administrator!new:" prefix when normally hidden code internally calls CoGetObject:
One other question: How do you handle someone running as standard user in Windows XP?