Subject: bug#27437: Source downloader accepts X.509 certificate for incorrect domain

From: [email-masked] (Ludovic Courtès)
Date: Thu, 22 Jun 2017 09:57:23 +0200

Leo Famulari <[email-masked]> skribis:

> On Wed, Jun 21, 2017 at 12:50:15PM +0200, Ludovic Courtès wrote:
>> Leo Famulari <[email-masked]> skribis:
>> > While working on some package updates, I found that the source code
>> > downloader will accept an X.509 certificate for an incorrect site.
>
> [...]
>
>> IOW, since we’re checking the integrity of the tarball anyway, and we
>> assume developers checked its authenticity when writing the recipe, then
>> who cares whether downloads.xiph.org has a valid certificate?
>> 
>> Does it make sense?
>
> Yeah, I think it makes sense if checking the certificates would add too
> much complexity for what I think is a minor benefit: protecting against
> exploitation of bugs by MITM (but not xiph.org) in whatever code runs
> after the connection is initiated and before the hash is calculated.
>
> Perhaps a MITM could send a huge file and fill up the disk or something
> like that.

I’m generally in favor of relying on X.509 certificates as little as
possible, and in this case, while I agree that it could protect us
against the scenario you describe, I think it’s a bit of a stretch.

However, we’d very likely have bug reports of people for which downloads
fail because of various issues in the X.509 infrastructure and/or in how
the they set up their system (‘nss-certs’ uninstalled or too old,
SSL_CERT_DIR unset, etc.)

Thoughts?

Thanks,
Ludo’.