Pythons M2Crypto raises exception in ssl_ctx_load_verify_locations when loading certificates

Question

M2Crypto raises a TypeError when loading SSL CA certificates. I'm getting the path of an SSL certificate from an instance of a Django model. My code worked perfectly because I was pulling the path of the certificate from a Django model

My code:

from M2Crypto import SSL
from django.db import models

class MyModel(models.Model):
    ca_file = models.FilePathField(path='/path/to/my/certificates/')

m = MyModel(ca_file='/path/to/my/certificates/certificate.cer')
m.save()

ctx = SSL.Context()
ctx.load_verify_locations(m.ca_file)

Raises:

Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/home/django/lib/datalivelib/utils/https.py", line 51, in do_https
    if ctx.load_verify_locations(ca_file) != 1:
  File "/usr/lib/pymodules/python2.6/M2Crypto/SSL/Context.py", line 131, in load_verify_locations
    return m2.ssl_ctx_load_verify_locations(self.ctx, cafile, capath)
TypeError: in method 'ssl_ctx_load_verify_locations', argument 2 of type 'char const *'

However this code works fine

from M2Crypto import SSL
ctx = SSL.Context()
ctx.load_verify_locations('/path/to/my/certificates/certificate.cer')

Answer 1

Just worked it out!

The load_verify_locations() function is expecting a string object, not a unicode object.

Django uses unicode by default, so the certificate path needs to be converted to a string before passed into load_verify_locations(). So:

ctx.load_verify_locations(str(m.ca_file))