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39e2d4 Samuli Seppänen 2025-03-19 08:31:17 1 
**NOTE: this article refers to an outdated version of tap-windows that was used on Windows systems before Windows 7. The information here is interesting only for digital archaeologists and historians**
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# Introduction
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TAP-Windows is an [OpenVPN subproject](https://github.com/OpenVPN/tap-windows) in [GitHub](https://github.com/). TAP-Windows is built on a Windows box, and the [OpenVPN cross-compile buildsystem](/BuildingUsingGenericBuildsystem) takes care of embedding the produced TAP-Windows installer into the OpenVPN Windows installer.
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If you're building [tap-windows6](https://github.com/OpenVPN/tap-windows6) instead, please look [here](/BuildingTapWindows6).
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# Setting up the Windows build computer
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First install a recent version of Windows DDK and [http://nsis.sourceforge.net NSIS].
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Next clone the *tap-windows* repository, e.g. using *Git Bash*:
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```
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$ cd /c/users/myuser
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$ git clone https://github.com/OpenVPN/tap-windows
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```
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Now set some environment variables:
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```
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set DDK=c:\WINDDK\7600.16385.1
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set DEVCON32=c:\WINDDK\7600.16385.1\tools\devcon\i386\devcon.exe
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set DEVCON64=c:\WINDDK\7600.16385.1\tools\devcon\amd64\devcon.exe
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set DEVCON_BASENAME=devcon.exe
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set SIGNTOOL=c:\WINDDK\7600.16385.1\bin\x86\signtool.exe
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set MAKENSIS=C:\Program Files (x86)\NSIS
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set OUTDIR=c:\users\myuser\tap-windows
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```
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Some of these variables have sane default values, and you many not need to define all of them. If you use self-signed test certificates you also need these variables:
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```
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set CODESIGN_PKCS12=c:\Users\John\tap-windows\my-self-signed-certificate.p12
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set CODESIGN_PASS=mypassphrase
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set CODESIGN_ISTEST=yes
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```
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For paid-for software publisher certificates (SPC) you'd use something like this:
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```
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set CODESIGN_PKCS12="c:\Users\John\tap-windows\my-software-publisher-certificate.p12"
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set CODESIGN_PASS=mypassphrase
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set CODESIGN_ISTEST=no
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set CODESIGN_CROSS="C:\Users\John\tap-windows\ca-cross-certificate.crt"
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set CODESIGN_TIMESTAMP="http://timestamp.domain.com"
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```
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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.
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To simplify variable setting in the future, you can create a batch file with all the above commands and run it before running *configure.bat*. For details on available environment variables see
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```
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> configure --help
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```
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# Building TAP-windows
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First you need to configure the tap-windows build to use the variables you defined. Do this from a Visual Studio command prompt:
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```
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> configure
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```
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This copies the variables to *tap-windows\config-env.bat* and various other places. All that's left is to build the tap-windows drivers:
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```
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> build
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```
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If you want to customize the build further, e.g. to build a custom TAP-Windows driver that can coexist with stock OpenVPN TAP-Windows driver, you can edit the *version.m4* or create a separate *config-local.m4*. Any variables in *config-local.m4* should override those in *version.m4*.
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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 [OpenVPN cross-compile buildsystem](/BuildingUsingGenericBuildsystem) to it.