From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff King Subject: Re: Starting to think about sha-256? Date: Mon, 28 Aug 2006 14:32:52 -0400 Message-ID: <20060828183252.GC2950@coredump.intra.peff.net> References: <44F1DCB7.6020804@garzik.org> <656C30A1EFC89F6B2082D9B6@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: David Lang , Johannes Schindelin , Krzysztof Halasa , Jeff Garzik , Git Mailing List X-From: git-owner@vger.kernel.org Mon Aug 28 20:33:10 2006 Return-path: Envelope-to: gcvg-git@gmane.org Received: from vger.kernel.org ([209.132.176.167]) by ciao.gmane.org with esmtp (Exim 4.43) id 1GHlur-00038b-PJ for gcvg-git@gmane.org; Mon, 28 Aug 2006 20:32:58 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751208AbWH1Scy (ORCPT ); Mon, 28 Aug 2006 14:32:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751227AbWH1Scy (ORCPT ); Mon, 28 Aug 2006 14:32:54 -0400 Received: from 66-23-211-5.clients.speedfactory.net ([66.23.211.5]:61899 "HELO peff.net") by vger.kernel.org with SMTP id S1751208AbWH1Scy (ORCPT ); Mon, 28 Aug 2006 14:32:54 -0400 Received: (qmail 3451 invoked from network); 28 Aug 2006 14:32:14 -0400 Received: from unknown (HELO coredump.intra.peff.net) (10.0.0.2) by 66-23-211-5.clients.speedfactory.net with SMTP; 28 Aug 2006 14:32:14 -0400 Received: by coredump.intra.peff.net (sSMTP sendmail emulation); Mon, 28 Aug 2006 14:32:52 -0400 To: Linus Torvalds Content-Disposition: inline In-Reply-To: Sender: git-owner@vger.kernel.org Precedence: bulk X-Mailing-List: git@vger.kernel.org Archived-At: On Mon, Aug 28, 2006 at 10:56:01AM -0700, Linus Torvalds wrote: > However, the "earlier will override" is very much what you want from a > security standpoint: remember that the git model is that you should > primarily trust only your _own_ repository. So if you do a "git pull", the This concept breaks down somewhat if you are pulling from two repositories (one good and one evil). If I pull from the evil repo first, that will become my "earlier" object, and I will never get the colliding object from the good repo. Executing such an attack might not be that hard, either (once we get over that little hump of creating collisions at will!). The owner of 'evil' has to know a SHA1 that will be in 'good' before it makes it to 'good'. However, I imagine we frequently see SHA1s migrate from more central repos (like .../torvalds/linux-2.6.git) to less central ones (subsystem / port maintainers, etc). -Peff