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Date: Mon, 22 Apr 2013 10:52:00 +1000
From: Allan McRae <allan@...hlinux.org>
To: oss-security@...ts.openwall.com
Subject: Re: upstream source code authenticity checking
On 22/04/13 09:27, Alistair Crooks wrote:
> On Sun, Apr 21, 2013 at 12:39:39AM +0400, Solar Designer wrote:
>> Hi,
>>
>> I just found this recent blog post by Allan McRae of Arch Linux:
>>
>> http://allanmcrae.com/2012/04/how-secure-is-the-source-code/
>>
>> Thank you for doing this, Allan! Are you contacting the upstream
>> authors to request that they start to properly sign their releases?
>> (I've been doing that on some occasions, sometimes with success.)
>>
>> I think that placing both "MD5 checksum provided on same site as
>> download" and "PGP signature, key difficult to verify" in the same
>> "yellow" category is inconvenient for us. "MD5 checksum provided on
>> same site as download" only helps verify downloads from mirrors against
>> the master site, whereas "PGP signature, key difficult to verify"
>> achieves a lot more - once a distro is already including the package
>> (and has already taken the risk of it having been tampered with), then
>> verifying further updates to the package becomes almost as reliable as
>> it would have been with proper signing (with a "readily verifiable" key).
>> So we need four categories, or simply "MD5 checksum provided on same
>> site as download" should be in "red", not in "yellow".
>
> The BSD ports and packages systems have had this checking in place
> since day 1, and with different checksums - FreeBSD now use sha256,
> pkgsrc uses sha1 and rmd160, and I don't know what OpenBSD uses;
> the digests are all held as part of the packaging system itself.
>
> One of the side benefits of this is recognising when upstream changes
> tarballs without changing version numbers.
>
> I think the Arch Linux people could leverage the work done here.
Arch Linux does have similar system (our package building infrastructure
uses PGP signature verification if available, any of a variety of
checksums).
The point of my post was that if upstream does not provide anything when
they release a tarball, then they really do not help that much... It
just verifies that the source the packager downloaded is the same as the
source you have. It does not save you if the source was altered before
the packager obtained it.
Allan
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