How to link python to the manually compiled OpenSSL rather than the system's one

Question

I need to manually compile OpenSSL from source. I use Ubuntu 18. The OpenSSL shipped with Ubuntu 18 does not support specific cipher I need. But it can be enabled if I compile OpenSSL manually. I found this manual. However, how can I link python ssl to take the manually installed OpenSSL not the OS one?

Answer 1

You can't relink the existing Python installation and need to build another Python distribution from source. When building Python, you need to adapt CPPFLAGS, LDFLAGS and LD_LIBRARY_PATH env variables. Assuming you installed the custom OpenSSL in /path/to/openssl:

$ cd /path/with/Python/sources/unpacked/
$ export LDFLAGS="-L/path/to/openssl/lib/ -L/path/to/openssl/lib64/"
$ export LD_LIBRARY_PATH="/path/to/openssl/lib/:/path/to/openssl/lib64/"
$ export CPPFLAGS="-I/path/to/openssl/include -I/path/to/openssl/include/openssl"
$ ./configure --prefix=/path/to/custom/python/
$ make
$ make install

Now Python in /path/to/custom/python/ will use the custom OpenSSL:

$ /path/to/custom/python/bin/python -c "import ssl; print(ssl.OPENSSL_VERSION)"
OpenSSL 1.1.0h  27 Mar 2018