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From: zimoun <zimon.toutoune@gmail.com>
To: "Ludovic Courtès" <ludo@gnu.org>
Cc: 44187-done@debbugs.gnu.org
Subject: bug#44187: Channel clones lack SWH fallback
Date: Mon, 20 Sep 2021 11:27:32 +0200	[thread overview]
Message-ID: <CAJ3okZ2XNXecc-Q0xCGcmJk99kJvk0coHSp+zpUwRGwbJSdOhg@mail.gmail.com> (raw)
In-Reply-To: <87pmt5si8b.fsf@gnu.org>

Hi,

On Sat, 18 Sept 2021 at 23:10, Ludovic Courtès <ludo@gnu.org> wrote:
> zimoun <zimon.toutoune@gmail.com> skribis:

> > and after more than 12h, the status is still: «SWH vault: Processing...»
> > and nothing is complete.
>
> Did it eventually succeed?  We obviously have no guarantee as to how
> long it might take to cook a bundle.

No, I stopped.  And I reported to #swh-devel.  It might be something
wrong on their side.
Yeah, cook a bundle could be long... especially with large repo as
Guix (lot of commits and couple of files).
I think it is ok to let the code as it is now.


> >> *Third, and this answers the asterisk above, we must keep in mind that
> >> this is content-addressibility *with SHA1*.  Generating a chosen-prefix
> >> collision is becoming affordable³, so users absolutely need an additional
> >> mechanism to authenticate code they fetched.
>
> [...]
>
> > How a chosen-prefix attack could work here?  I understand why the second
> > preimage attack is an issue.  But I miss how the SHA-1 chosen-prefix attack
> > could be exploited here to compromise the user, because this hash is provided
> > by this very same user.
>
> I think you’re right, it’s rather second-preimage attacks that would be
> a serious problem.  My point is: as time passes, assuming that a SHA1
> resolves to a single revision on SWH is becoming more and more
> questionable.

Well, SHA-1 is 2^160 (~10^48.2) and compared to 10^50 which is the
estimated number of atoms in Earth.  Speaking about
content-addressability, SHA-1 seems fine.  However, for security, yeah
time flies. :-)


> >>   swh: Support downloads of bare Git repositories.
> >>   git: 'update-cached-checkout' can fall back to SWH when cloning.
> >>   git: 'reference-available?' recognizes 'tag-or-commit'.
>
> I’ve pushed this after adding the warning as you suggested:
>
>   dce2cf311b * git: 'reference-available?' recognizes 'tag-or-commit'.
>   05f44c2d85 * git: 'update-cached-checkout' can fall back to SWH when cloning.
>   6ec81c31c0 * swh: Support downloads of bare Git repositories.

Cool!  I would deserve a --news entry. ;-)

Cheers,
simon




  reply	other threads:[~2021-09-20  9:28 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-23 22:17 bug#44187: whishlist: time-machine --channel falls back to SWH zimoun
2021-03-05 14:51 ` Ludovic Courtès
2021-09-10 14:34   ` bug#44187: [PATCH 0/3] Fall back to Software Heritage (SWH) for Git clones Ludovic Courtès
2021-09-10 14:34     ` bug#44187: [PATCH 1/3] swh: Support downloads of bare Git repositories Ludovic Courtès
2021-09-17 17:31       ` bug#44187: Channel clones lack SWH fallback zimoun
2021-09-18 10:05         ` Ludovic Courtès
2021-09-18 10:27           ` zimoun
2021-09-10 14:34     ` bug#44187: [PATCH 2/3] git: 'update-cached-checkout' can fall back to SWH when cloning Ludovic Courtès
2021-09-10 14:34     ` bug#44187: [PATCH 3/3] git: 'reference-available?' recognizes 'tag-or-commit' Ludovic Courtès
2021-09-13 16:07     ` bug#44187: [PATCH 0/3] Fall back to Software Heritage (SWH) for Git clones zimoun
2021-09-14 13:37       ` Ludovic Courtès
2021-09-17  8:02 ` bug#44187: Channel clones lack SWH fallback zimoun
2021-09-18 21:10   ` Ludovic Courtès
2021-09-20  9:27     ` zimoun [this message]
2021-09-22 10:03       ` Ludovic Courtès

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