urllib https implementation does not verify ssl certificates

[dave b.]

Because pycurl isn't a dependency only a "suggestion" it will not be installed with bzr on ubuntu.
This is bad because the https implementation is broken as per bug http://bugs.python.org/issue1589
as bzr seems not to verify the common name (etc.) --> (see http://bazaar.launchpad.net/~bzr-pqm/bzr/bzr.dev/annotate/head%3A/bzrlib/transport/http/_urllib2_wrappers.py)

So your application is vulnerable, as long as I have a certificate signed by ca in the ca store, I can MITM bzr by default - as pycurl isn't a dep. Iff pycurl is installed you are not vulnerable.
Please let me know if I am wrong :)

[Martin Pool (mbp)]

By this logic we should

1- require pycurl on Ubuntu
2- give some kind of user warning or opt-in before using non-pycurl
https to cover other platforms

or if it is feasible, verify the CN ourselves?

What do you think, Vincent?
--
Martin

[Vincent Ladeuil (vila)]

First:
- pycurl is still the default https implementation used if it is installed,
- users concerned with security are better served by using ssh and signing their revisions.

That being said, I suspect the more likely potential victims may not be aware of the problem at all and may not install pycurl nor use ssh nor sign their revisions.

Now, setting up a mitm attacjk alone is not enough, you also need to inject malicious code in a repo while still faking the signatures and sha1 associated with the revisions and that nobody check the code nor inspect the merge results.

That sill leave a narrow window for people not signing and I'm not sure we check the sha1 in all scenarios either.

But given the work involved on our side to even diagnose if such an attack is feasible, I think we should just implement https support properly for our urllib-based implementation.

I think most of our users are using python2.6 now, so supporting 2.4 and 2.5 is less concerning than it was last time I worked on the subject.

[dave b. (d+b)]

The hg guys fixed this ... perhaps you could do what they do. (also see the python bug for the new ssl methods that now exist in 3.2)
Simply dropping the non-pycurl method maybe a good idea ? / adding a warning to the non-pycurl version.
So by default on ubuntu pycurl seems to be installed but on other distributions this may not be the case.

[Jelmer Vernooij (jelmer)]

Shouldn't this be possible now with the ssl module in python 2.7?