[Python-Dev] PEP 476: Enabling certificate validation by default!

R. David Murray rdmurray at bitdance.com
Sun Aug 31 16:16:27 CEST 2014

On Sun, 31 Aug 2014 16:45:42 +1000, Nick Coghlan <ncoghlan at gmail.com> wrote:
> On 31 August 2014 16:16, Donald Stufft <donald at stufft.io> wrote:
> >
> > On Aug 31, 2014, at 2:09 AM, Nick Coghlan <ncoghlan at gmail.com> wrote:
> >
> > At the same time, we need to account for the fact that most existing
> > organisations still trust in perimeter defence for their internal
> > network security, and hence tolerate (or even actively encourage) the
> > use of unsecured connections, or skipping certificate validation,
> > internally. This is actually a really terrible idea, but it's still
> > incredibly common due to the general failure of the technology
> > industry to take usability issues seriously when we design security
> > systems (at least until recently) - doing the wrong "unsafe" thing is
> > genuinely easier than doing things right.
> >
> >
> > Just a quick clarification in order to be a little clearer, this change will
> > (obviously) only effect those who trust perimeter security *and* decided to
> > install an invalid certificate instead of just using HTTP. I'm not saying
> > that
> > this doesn't happen, just being specific (I'm not actually sure why they
> > would
> > install a TLS certificate at all if they are trusting perimeter security,
> > but
> > I'm sure folks do).
> It's the end result when a company wide edict to use HTTPS isn't
> backed up by the necessary documentation and training on how to get a
> properly signed cert from your internal CA (or, even better, when such
> an edict comes down without setting up an internal CA first). Folks
> hit the internet instead, find instructions on creating a self-signed
> cert, install that, and tell their users to ignore the security
> warning and accept the cert. Historically, Python clients have "just
> worked" in environments that required a click-through on the browser
> side, since you had to opt in to checking the certificates properly.
> Self-signed certificates can also be really handy for doing local
> testing - you're not really aiming to authenticate the connection in
> that case, you're just aiming to test that the secure connection
> machinery is all working properly.

Self-signed certificates are not crazy in an internal corporate
environment even when properly playing the defense in depth game.  Once
you've acked the cert the first time, you will be warned if it changes
(like an ssh host key).  Sure, as Nick says the corp could set up an
internal signing authority and make sure everyone has their CA...and
they *should*...but realistically, that is probably relatively rare at
the moment, because it is not particularly easy to accomplish
(distributing the CA everywhere it needs to go is still a Hard Problem,
though it has gotten a lot better).

Given the reality of human nature, even when the documentation
accompanying the HTTPS initiative is good, there will *still* be someone
who hasn't followed the internal rules, yet you really need to talk to
the piece of infrastructure they are maintaining.  At least that one is
short term problem (for some definition of "short" that may be several
months long), but it does exist.

In addition, as has been mentioned before, self-signed certs are often
embedded in *devices* from vendors (I'm looking at you, Cisco).  This is
another area where security conciousness has gotten better (the cert
exists) but isn't good yet (the cert is self-signed and replacing it
isn't trivial when it is even possible; and, because the self-signed cert
happens by default....it gets left in place).  And in the case of those
embedded certs, the cert can wind up *invalid* (expired) as well as
self-signed.  (This last item is where my concern about being able
to talk to invalid certs comes from.)

And yes, I have encountered all of this in the wild.


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