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Date:      Fri, 6 Feb 2009 20:11:57 +0100
From:      cpghost <cpghost@cordula.ws>
To:        Giorgos Keramidas <keramida@ceid.upatras.gr>
Cc:        "freebsd-questions@freebsd.org" <freebsd-questions@freebsd.org>
Subject:   Re: OT: SVN checkout checksumming
Message-ID:  <20090206191157.GB2438@phenom.cordula.ws>
In-Reply-To: <871vubv66x.fsf@kobe.laptop>
References:  <4989B239.9090504@optiksecurite.com> <878wolpydl.fsf@kobe.laptop> <20090206165800.GB1444@phenom.cordula.ws> <871vubv66x.fsf@kobe.laptop>

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On Fri, Feb 06, 2009 at 07:14:14PM +0200, Giorgos Keramidas wrote:
> On Fri, 6 Feb 2009 17:58:00 +0100, cpghost <cpghost@cordula.ws> wrote:
> >> Let's assume for a moment that you install a post-commit hook that
> >> generates a SHA-256 checksum of all the files in the latest repo
> >> revision on the svn server.
> >>
> >> For the sake of simplicity, let's assume that this file is a simple,
> >> plain text file that is named db/revs/NUMBER.sha256 where 'NUMBER' is
> >> the revision number you are check-summing.
> >>
> >> How are you going to *safely* transmit those SHA-256 checksums to the
> >> client on 'svn checkout'?
> >
> > Well, sorry to bring this back up, but again: how about signing
> > NUMBER.sha256 with a GnuPG private key belonging to the FreeBSD
> > Project? If there's a way to *safely* get the corresponding
> > public key, checking the signature of the NUMBER.sha256 files
> > would be trivial.
> 
> If the signed data is not part of the actual repository, you have a
> signature for a numeric value, not a signature for the *contents* of the
> repository itself.

Hmmm... yes, you're right. Only the digest would be signed in this
case, and that's not enough. But if the (digest, revision) pair is
signed, that would at least be useful (somewhat).

So, let's say that NUMBER.sha256 starts with something like a comment:

# r123456
<path1 / digest1>
<path2 / digest2>
<path3 / digest3>
...

and all this signed, would it be enough?

Even if the repository isn't signed, one can compute the digests
locally and check them with the *signed* list of digests. It may
not catch everything because of possible collisions, but wouldn't
that be already better than nothing?

-cpghost.

-- 
Cordula's Web. http://www.cordula.ws/



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