Building pyOpenSSL on Windows

This document details the steps to build an pyOpenSSL egg with embedded OpenSSL library, for use by Tahoe-LAFS on Windows.

The instructions were tried on Windows 7 64-bit and Windows XP 32-bit. They should work on other versions of Windows, maybe with minor variations.

Download and install Microsoft Visual C++ compiler for Python 2.7

For reasons detailed in the Python documentation, Python extension modules need to be built using a compiler compatible with the same version of Visual C++ that was used to build Python itself. Until recently, this meant downloading Microsoft Visual Studio 2008 Express Edition and Windows SDK 3.5. The recent release of the Microsoft Visual C++ compiler for Python 2.7 made things a lot simpler.

So, the first step is to download and install the C++ compiler from Microsoft from this link.

Find the location where it installed the vcvarsall.bat file; depending on the version of Windows it could be either "%USERPROFILE%\AppData\Local\Programs\Common\Microsoft\Visual C++ for Python\9.0" or "%CommonProgramFiles%\Microsoft\Visual C++ for Python\9.0", for example. We’ll call this %VCDIR% below.

Download and install Perl

Download and install ActiveState Perl:

Download and install the latest OpenSSL version

  • Download the latest OpenSSL from the OpenSSL source download page and untar it. At the time of writing, the latest version was OpenSSL 1.0.1m.

  • Set up the build environment. For 64-bit Windows:

    "%VCDIR%\vcvarsall.bat" amd64

    or for 32-bit Windows:

    "%VCDIR%\vcvarsall.bat" x86
  • Go to the untar’ed OpenSSL source base directory. For 64-bit Windows, run:

    mkdir c:\dist
    perl Configure VC-WIN64A --prefix=c:\dist\openssl no-asm enable-tlsext
    nmake -f ms\ntdll.mak
    nmake -f ms\ntdll.mak install

    or for 32-bit Windows, run:

    mkdir c:\dist
    perl Configure VC-WIN32 --prefix=c:\dist\openssl no-asm enable-tlsext
    nmake -f ms\ntdll.mak
    nmake -f ms\ntdll.mak install

To check that it is working, run c:\dist\openssl\bin\openssl version.

Building PyOpenSSL

  • Download and untar pyOpenSSL 0.13.1 (see ticket #2221 for why we currently use this version). The MD5 hash of pyOpenSSL-0.13.1.tar.gz is e27a3b76734c39ea03952ca94cc56715.

  • Set up the build environment by running vcvarsall.bat as for building OpenSSL above.

  • Set OpenSSL LIB, INCLUDE and PATH:

    set LIB=c:\dist\openssl\lib;%LIB%
    set INCLUDE=c:\dist\openssl\include;%INCLUDE%
    set PATH=c:\dist\openssl\bin;%PATH%
  • A workaround is needed to ensure that the setuptools bdist_egg command is available. Edit pyOpenSSL’s around line 13 as follows:

    < from distutils.core import Extension, setup
    > from setuptools import setup
    > from distutils.core import Extension
  • Run python bdist_egg

The generated egg will be in the dist directory. It is a good idea to check that Tahoe-LAFS is able to use it before uploading the egg to This can be done by putting it in the tahoe-deps directory of a Tahoe-LAFS checkout or release, then running python test.