Re: Sha1 is not exactly secure
Adam Majer <adamm@zombino.com> writes:
> On 7/7/24 21:53, Russ Allbery wrote:
>> I consider it an ethical obligation as someone who works in security to
>> object whenever people make these types of absolute statements about
>> security properties. Security is almost always a trade off. You can
>> usually get more security by trading off functionality, up to the
>> obvious end point of securing a computer by turning it off. The best
>> point to occupy on that trade-off curve is a hard question that always
>> involves more factors than only security.
> It was not an absolute statement, but simply a consequence where I tend
> to trust NIST recommendation over handwaving arguments. This is
> especially true since I'm no cryptographer and have to rely on other
> experts for these recommendations.
That makes very good sense to me. Since you don't have expertise in this
field, that's exactly what I would recommend you do. That is definitely
the safest approach.
Since I do have expertise in this area, my analysis was more complex than
trying to extrapolate from NIST guidance.
> Furthermore, did you read what was written in the Bitcoin repo link?
> It's simply adding a hash to the signed tag. Since this proposal here
> for push-to-upload is to use a script to generate the tag anyway, adding
> additional hash to the message is kind of a "no-brainer" --- it doesn't
> cost anything!
It does cost something: it requires custom code and local configuration
and requires us to use Git differently than everyone else uses Git. You
may or may not care about that cost, but it's a cost.
I didn't get into this because I think it's beside the point, but since
you're asking explicitly: I am also quite dubious of that specific
approach because it's adding an additional hash to only one specific type
of Git object, piecemeal, in a helper script that seems to only be used by
that one repository (and which they seem to have subsequently dropped).
If we're going to add richer hashes in a custom layer on top of Git, we
should use git-evtag or some other similarly comprehensive solution that
has thought through all of the implications, not try to apply hacks and
bandaids like that.
git-evtag was discussed earlier, so I won't go into the arguments there
again.
> Anyway, I've been forwarded this commit in git upstream recently.
> https://github.com/git/git/commit/6ccf041d1d73d69d05118f739c80f83c86caf0d6
Great! Hopefully this will mean GitLab will add support in the near
future.
--
Russ Allbery (rra@debian.org) <https://www.eyrie.org/~eagle/>
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