Re: Checking signatures on source tarballs

[Christopher Allan Webber <cwebber@dustycloud.org>]

Mark H Weaver writes:

> Alex Kost <alezost@gmail.com> writes:
>
>> Ludovic Courtès (2015-10-05 18:55 +0300) wrote:
>>
>>> Alex Kost <alezost@gmail.com> skribis:
>>>
>>>> Ludovic Courtès (2015-10-04 19:57 +0300) wrote:
>>>>
>>>>> However, if this is “too convenient”, I’m afraid this would give an
>>>>> incentive to not check OpenPGP signatures when they are available.
>>>>
>>>> Sorry, I have no idea what it means :-(
>>>
>>> When upstream digitally signs its source code tarballs, packagers should
>>> check those signatures to authenticate the code they have.
>>>
>>> If the tool makes it too easy to fill out the ‘sha256’ field without
>>> going through the trouble of downloading the ‘.sig’ file and checking
>>> it, then people will have an incentive not to check those signatures.
>>
>> Oh, now I see what you mean.  Well, I don't know, I think if a user has
>> a habbit to check a signature, he will check it anyway; and if not, then
>> not.
>
> I share Ludovic's concern.  It is a serious problem if packagers fail to
> check signatures.  We should not provide mechanisms that encourage such
> behavior.  It jeopardizes the security of every user of those packages.
>
> IMO, we should rather be going in the other direction, to formalize and
> automate the checking of signatures.  IMO, our 'origin' objects should
> include a set of fingerprints of acceptable GPG signing keys for that
> package, as well as information on how to find the signature (in cases
> where it cannot be guessed).
>
> This would have several beneficial effects:
>
> * If the packager downloaded a key belonging to a man-in-the-middle
>   (quite possible given that we rarely have a validated chain of trust
>   to the developer), then that bad key will be stored in our git repo
>   for all to see, allowing someone to notice that it's the wrong key.
>
> * When the package is later updated, it will not be possible for a new
>   man-in-the-middle attack to be made on us.  If a new signing key is
>   used, we cannot fail to notice it.  It will raise a red flag and we
>   can investigate.
>
> * It would strongly encourage packagers to do these checks, and make it
>   obvious to reviewers or users when the packager failed to do so.  It
>   would also make it easy to find unsigned packages, so that we can
>   encourage upstream to start signing the packages, at least for the
>   most important ones.
>
> Also, our linter should download and check the signature, so that it's
> easy for others to independently check the verification done by the
> original packager.
>
> What do you think?
>
>       Mark

This sounds great to me!