Signing Windows Drivers

By Alasdair Lumsden on 6 Jul 2010

We were signing some Open Source GPL Windows drivers to use on Windows Server 2008 x64 edition (which only accepts signed drivers) and were encountering the following Windows boot error after installing our supposedly successfully signed drivers:

Windows cannot verify digital signature for this file

We have an official Verisign code signing certificate, and were a bit stumped/confused. The files seemed to be signed and everything seemed to be okay.

The problem was that we were not adding a cross-certificate. A cross certificate basically provides a chain of authority so that Windows is able to trust your certificate. You can find out more information about this from this helpful blog post over here.

If we had bothered to TRFM, the Code Signing walkthrough does kind of tell you you need to sign your drivers with a cross certificate, so we probably could have saved ourselves a lot of time by reading this first.

Anyway, you can obtain the cross certs from here, and the option to use with signtool.exe is /ac, so for example you’d type:

signtool.exe sign /v /ac MSCV-VSClass3.cer /s my /n "Every City Limited" /t

Hopefully this post will help other people save some time, as we spent all day trying to figure this one out.