Introduction

In the Lviv hackathon the we agreed on the following things:

• OpenVPN 2.5 Windows installer should be MSI-based
• We won't provide NSIS installers for 2.5 unless there are major issues in the MSI
• The installer should include OpenVPN, OpenVPNService, tap-windows6 etc. each as separate MSI feature
• People who want to install just tap-windows6 can disable the OpenVPN features
• We should not try to embed MSI installers into MSI installers due to lack of good documentation
• Each installation architecture/target will get its own MSI installer
• We should bundle all the MSI installer into a thin wrapper executable, such as a self-extracting p7zip archive with a script hook that detect which MSI to launch
• The individual MSI files should also be made available for more technical users as well as system administrators
• The custom action DLL used in the tap-windows6 MSI installation logic could be included in openvpn.git, so that openvpn-build could easily build and sign it, just as is done with openvpn.exe and openvpnserv.exe. Having it in tap-windows6 repository would make signing that DLL slightly more problematic, as we don't really sign anything with the tap-windows6 buildsystem anymore.
• The MSI (WiX) code can be placed into a subdirectory in openvpn-build Git repository alongside "generic", "msvc" and "windows-nsis". The MSI should consume the artefacts that openvpn-build cross-compile process produces.

Installer targets

There are several "targets" for the installer. We not only have the architecture split (i386, x64, amd64), but also different types of kernel-mode signatures for tap-windows6:

Operating system	KM signature	i386	x64	arm64
Windows 7/8	Cross-signed	X	X
Windows 10	Attestation-signed[1]	X	X	X
Windows Server 2012r2	Cross-signed		X
Windows Server 2016	WHQL-certified		X
Windows Server 2019	WHQL-certified		X

So we have the following architecture-signature combinations:

1. i386/x64 cross-signed
2. i386/x64/arm64 attestation signed
3. x64 WHQL certified

The user-mode signatures for openvpn.exe, openvpnserv.exe etc. can be created with standard, non-EV authenticode keys on all platforms.

Notes

[1] The requirement for attestation signatures in kernel-mode code came into Windows 10 quite early. It is not know if really old Windows 10 version can load attestation-signed drivers, but that seems likely. Even if they don't we may not want to support those