How to call NtUserPostMessage from kernel-mode WFP callout driver?

Question

In order to fit a WFP (Windows Filtering Platform) callout driver into an existing product, I need to have it send window messages to an existing application. Is there a way to do this from a kernel-mode WFP driver?

There's a technique here for calling NtUserPostMessage from kernel-mode drivers, but I'm not sure if it applies to a WFP driver and it predates Windows 8 so it doesn't have the right syscall address for the new OS.

I'm open to any method of sending window messages (or, more precisely, posting them so there won't be a delay) because it would keep me from having to recode part of the existing app.

Answer 1

I think best method would be to have IOCTL interface between user and kernel mode. You can use this method https://www.osr.com/nt-insider/2013-issue1/inverted-call-model-kmdf/ . This allows you to send data also between user & kernel mode.