[[TOC(inline, depth=1)]]

= Introduction =

TAP-Windows is an [https://github.com/OpenVPN/tap-windows OpenVPN subproject] in [https://github.com/ GitHub]. TAP-Windows is built on a Windows box, and the [wiki:BuildingUsingGenericBuildsystem OpenVPN cross-compile buildsystem] takes care of embedding the produced TAP-Windows installer into the OpenVPN Windows installer.

= Setting up the Windows build computer =

First install a recent version of Windows DDK and [http://nsis.sourceforge.net NSIS].

Next clone the ''tap-windows'' repository, e.g. using ''Git Bash'':

{{{
$ git clone https://github.com/OpenVPN/tap-windows
}}}

Next you need to set some environment variables. For self-signed test certificates use something like this:

{{{
set CODESIGN_PKCS12=c:\Users\John\tap-windows\my-self-signed-certificate.p12
set CODESIGN_PASS=mypassphrase
set CODESIGN_ISTEST=yes
}}}

For paid-for software publisher certificates (SPC) you'd use something like this:

{{{
set CODESIGN_PKCS12="c:\Users\John\tap-windows\my-software-publisher-certificate.p12"
set CODESIGN_PASS=mypassphrase
set CODESIGN_ISTEST=no
set CODESIGN_CROSS="C:\Users\John\tap-windows\ca-cross-certificate.crt"
set CODESIGN_TIMESTAMP="http://timestamp.domain.com"
}}}

If you imported the kernel-mode code-signing certicate using Internet Explorer, you can use ''certmgr.exe'' to export it in PFX (=PKCS12) format. Just make sure to include the private key in the file and to give it a sufficiently strong password, which you then define using ''CODESIGN_PASS'' variable. The CA cross certificate can be obtained from your CA and most likely needs no modifications. The URL for the timestamping service is CA-specific, but trivial to locate.

= Building TAP-windows =

First you need to configure the tap-windows build to use these using a Visual Studio command prompt:

{{{
> configure
}}}

This copies the variables to ''tap-windows\config-env.bat'', which is included during build. All that's left is to build the tap-windows drivers:

{{{
> build
}}}

Further customization for MSVC can be done using ''config-local.m4'' file which overrides variables or with environment variables which override auto detection code. This can be used, for example, to specify a custom DDK location. For details, see

{{{
> configure --help
}}}

Finally, if you're generating an OpenVPN installer with the your modified TAP-Windows driver, put the TAP-Windows installer on a webserver and point the [wiki:BuildingUsingGenericBuildsystem OpenVPN cross-compile buildsystem] to it.