[Python-Dev] dynamic linking, libssl.1.0.0.dylib, libcrypto.1.0.0.dylib and Mac OS X

[Chris Withers]

Hi All,

I hit this every time I install packages on Mac OS X that use libssl, it 
looks like extensions are built linking to .dylib's that are not 
resolveable when the library is actually used:

 >>> from OpenSSL import SSL
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
   File "python2.7/site-packages/OpenSSL/__init__.py", line 8, in <module>
     from OpenSSL import rand, crypto, SSL
   File "python2.7/site-packages/OpenSSL/rand.py", line 11, in <module>
     from OpenSSL._util import (
   File "python2.7/site-packages/OpenSSL/_util.py", line 6, in <module>
     from cryptography.hazmat.bindings.openssl.binding import Binding
   File 
"python2.7/site-packages/cryptography/hazmat/bindings/openssl/binding.py", 
line 13, in <module>
     from cryptography.hazmat.bindings._openssl import ffi, lib
ImportError: 
dlopen(python2.7/site-packages/cryptography/hazmat/bindings/_openssl.so, 
2): Library not loaded: libssl.1.0.0.dylib
   Referenced from: 
python2.7/site-packages/cryptography/hazmat/bindings/_openssl.so
   Reason: image not found

Looking at what this links to, I see:

$ otool -L 
lib/python2.7/site-packages/cryptography/hazmat/bindings/_openssl.so
lib/python2.7/site-packages/cryptography/hazmat/bindings/_openssl.so:
     libssl.1.0.0.dylib (compatibility version 1.0.0, current version 1.0.0)

Whereas the functional _ssl that ships with Python distributions on Mac 
OS X look like this:

$ otool -L .../lib/python2.7/lib-dynload/_ssl.so
.../lib/python2.7/lib-dynload/_ssl.so:
     @loader_path/../../libssl.1.0.0.dylib (compatibility version 1.0.0, 
current version 1.0.0)

What's going wrong here and what can be done differently to have
'pip install package_using_libssl' build a usable binary installation?

Here's a couple of examples of this problem in the wild:

https://github.com/alekstorm/backports.ssl/issues/9
http://stackoverflow.com/questions/32978365/how-do-i-run-psycopg2-on-el-capitan-without-hitting-a-libssl-error
https://github.com/psycopg/psycopg2/issues/385

I'm well out of my depth here, I just want to use these libraries, but 
I'm happy to try and do the work to make the world a better place for 
Mac users of these libraries...

Chris