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Date:      Sun, 13 Apr 2014 22:24:45 -0700
From:      Xin Li <delphij@delphij.net>
To:        David.I.Noel@gmail.com, =?ISO-8859-1?Q?Dag-Erling_Sm=F8rgrav?= <des@des.no>
Cc:        Lowell Gilbert <freebsd-security-local@be-well.ilk.org>, freebsd-security@freebsd.org, security@freebsd.org
Subject:   Re: Retiring portsnap [was MITM attacks against portsnap and freebsd-update]
Message-ID:  <534B711D.5060109@delphij.net>
In-Reply-To: <CAHAXwYCYq6_S6P3Z56LNdpVgUj2y53U0Xd3_aOQfXECQ73FzJQ@mail.gmail.com>
References:  <CAHAXwYCGkP-o0VvMXj5S8-KNA45aTvy%2BsrjDL_=8-x9Dza5z5Q@mail.gmail.com> <53472B7F.5090001@FreeBSD.org> <CAHAXwYDdxbRimwjvPf%2B5odYUUN4u4rNzdEkEmWwZN97mi1riEg@mail.gmail.com> <53483074.1050100@delphij.net> <CAHAXwYDhxmEwxtBLyZF1R1F8XENsq4FbpzVy89BN8f%2BRYU74KA@mail.gmail.com> <44bnw5uwmm.fsf@lowell-desk.lan> <CAHAXwYBDWEUH2yDR59Aurbsrjn4W0JAH87Qk7Oumncwagu45Bg@mail.gmail.com> <86zjjosxyy.fsf@nine.des.no> <CAHAXwYBWScbTOkdYFDRrh0faKb3BjX2gXmWhNbG-Gjfn4DLf0A@mail.gmail.com> <CAHAXwYCYq6_S6P3Z56LNdpVgUj2y53U0Xd3_aOQfXECQ73FzJQ@mail.gmail.com>

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On 4/13/14, 10:04 PM, David Noel wrote:
> On 4/13/14, David Noel <david.i.noel@gmail.com> wrote:
>>> So by your definition, every single Apache server on the planet
>>> runs "a closed source fork of the open source Apache project"
>>> because they do not use the exact same httpd.conf?
>> 
>> Ah, you're right. That's from build.conf. My mistake.
> 
> Though if it's using spiped I'm not sure how it would doing that
> from purely a config file change.

Let's focus on the more important points :)

To answer your question -- The actual portsnap build server setup is
more complex than the one in svn repository.  Using spiped needs the
other side of server (which serves svn repository).  So no, it's not a
pure configuration change, but a configuration change plus other setup
to support it.

That's said, we can confidently say "Yes" if the question is whether
portsnap build server have trustworthy direct access to FreeBSD ports
subversion repository.  No MITM attack can happen without being
noticed almost immediately in this chain.

The other points you have raised are more important, though.

One thing that we can easily implement to mitigate the freeze attack
would probably to make portsnap snapshots expire after a reasonable
amount of time (that is, publish a timestamp signed with the portsnap
key, e.g. expires after 4 hours, so instead of "No updates found" you
get "Snapshot was expired, something bad happen"), but that only
narrows down the window and does not fully eliminate it.

For freebsd-update I don't have a good idea at this time for the
freeze attack.

Cheers,
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