Cryptography: ImportError in a python-for-android app

[wexi]

I raised the following issue with the P4A guys but I think (hope) that you may be of greater help.
Perhaps you have encountered this problem before. Here I copy and paste.

Thanks, Enoch.

cryptography is an essential module in my kivy / twisted / pyOpenSSL based app.
Building finally succeeded (it wasn't straightforward) but now we are run time testing.
Thanks to a tip from "tshirtman" I had a meaningful rpdb interactive session as follows:

$ telnet 192.168.1.254 4444
Trying 192.168.1.254...
Connected to 192.168.1.254.
Escape character is '^]'.
> /home/enoch/private/gsld/build/bdist.android-armeabi-v7a/gsld/main.py(38)<module>()
(Pdb) import cryptography
(Pdb) cryptography.__file__
'/data/data/info.gencon.gsld/files/app/lib/python2.7/site-packages/cryptography/__init__.pyo'
(Pdb) os.listdir('/data/data/info.gencon.gsld/files/app/lib/python2.7/site-packages/cryptography')
['utils.pyo', '__init__.pyo', '__about__.pyo', 'fernet.pyo', 'exceptions.pyo', 'x509', 'hazmat']
(Pdb) import cryptography.hazmat
(Pdb) import cryptography.x509
***** ImportError: cannot import name certificate_transparency**
(Pdb) os.listdir('/data/data/info.gencon.gsld/files/app/lib/python2.7/site-packages/cryptography/x509')
['general_name.pyo', 'name.pyo', 'oid.pyo', '__init__.pyo', 'extensions.pyo', 'base.pyo', 'certificate_transparency.pyo']

This ImportError indicates that python was not able to get the module code! Not that a file is missing...
Since the same cryptography module (github master) works well in Linux I tend to believe that our stale Python version 2.7.2 is to blame... (Ubuntu is using 2.7.14). Or, do you have another idea?

[alex]

You're not the first person to run into an issue importing cryptography.x509.certificate_transparency, however I have no clue what the issue is :-(

[wexi]

cryptography now works in my Python-for-Android setting:

The problem was that all its shared objects (_padding.so, _openssl.so, _constant_time.so), as well as CFFI's _cffi_backend.so, could not find at run-time the libpython2.7.so.

What helped was building those shared objects with extra LDFLAGS arguments:
-lpython and -rpath=/data/data/_app-name_/lib (where libpython2.7.so resides).

It would have better if ImportError advises why it failed importing.

[ReckyXXX]

@wexi

What helped was building those shared objects with extra LDFLAGS arguments:
-lpython and -rpath=/data/data/app-name/lib (where libpython2.7.so resides).

Sorry for my incompetence, but could you write the full command to build them, please.
I have the similar issue..

[gene1wood]

@wexi Can you share more detail about what you did in regards to LDFLAGS to workaround this problem?

[ScottEAdams]

Was getting the same importerror in docker using pipenv but thx to @wexi comment I fixed it by building CFFI from source as recommended in cffi docs http://cffi.readthedocs.io/en/latest/installation.html#platform-specific-instructions:

virtualenv ~/venv
cd ~/path/to/sources/of/cffi
~/venv/bin/python setup.py build --force # forcing a rebuild to make sure
~/venv/bin/python setup.py install

For me that meant:

RUN wget https://pypi.python.org/packages/e7/a7/4cd50e57cc6f436f1cc3a7e8fa700ff9b8b4d471620629074913e3735fb2/cffi-1.11.5.tar.gz#md5=ac8492f4ad952360737413e82d661908 \
    && tar -vxf cffi-1.11.5.tar.gz \
    && cd cffi-1.11.5 && python setup.py build --force \
    && python setup.py install