From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-5.0 required=3.0 tests=AWL,BAYES_00, FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS, RCVD_IN_DNSWL_HI,RP_MATCHES_RCVD shortcircuit=no autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id B5C101F744 for ; Tue, 19 Jul 2016 07:22:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753218AbcGSHWS (ORCPT ); Tue, 19 Jul 2016 03:22:18 -0400 Received: from mout.gmx.net ([212.227.17.21]:65166 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752883AbcGSHWR (ORCPT ); Tue, 19 Jul 2016 03:22:17 -0400 Received: from virtualbox ([37.24.142.100]) by mail.gmx.com (mrgmx103) with ESMTPSA (Nemesis) id 0MRXVc-1bna4p1cO8-00ShB5; Tue, 19 Jul 2016 09:21:47 +0200 Date: Tue, 19 Jul 2016 09:21:46 +0200 (CEST) From: Johannes Schindelin X-X-Sender: virtualbox@virtualbox To: Herczeg Zsolt cc: "brian m. carlson" , Theodore Ts'o , Duy Nguyen , Git Mailing List Subject: Re: Git and SHA-1 security (again) In-Reply-To: Message-ID: References: <20160716201313.GA298717@vauxhall.crustytoothpaste.net> <20160717142157.GA6644@vauxhall.crustytoothpaste.net> <20160717154234.GC6644@vauxhall.crustytoothpaste.net> <20160717162349.GB11276@thunk.org> <20160717220417.GE6644@vauxhall.crustytoothpaste.net> <1468804249.2037.0@smtp.gmail.com> User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Provags-ID: V03:K0:ox4Ianwbf6MbJpM/QLt6QVKTyE+bF+o5qZkpFvioGHuI3oBrXv8 gCSwuihZqCSw+ZfZJXiKw7kHkY1+NEmFJFpTeObDDcK9wQxSN/rjtGzHOFCul8o+724fSEp WZ14nV8IC278ZSfUnIHRDZYErvsjPLpitbSapjac4A7NMMhUBIonBPS38tjz0yJDn7PYEwO rTGa7xOYfQKsu5IkGHpPw== X-UI-Out-Filterresults: notjunk:1;V01:K0:7xwaM+RJjk8=:bskonoVVoiYQcFZ9KqfbUB t5YVeq9oAXGMicLn0PwvOd5cuEh3H0ELXX0F0f1+DiBF2ptdBWj4ZSN5r+GteLMw1nEWZGuta BX/FI9W9JILSUU0Vxrr7NrREEo5jsyWa3Mf4vH2NaHTx8/vjYZxxp9Ztbk3S9YoxchVbC2fc5 9c3agawzXtXAxUx9Nw4qMNIZva+HbtB5kZNe60zUcmDJUT2553QLoHlAE+g6bmt690wOMznvx XMj6JtiLkQyXWPtLoHM0b3aDJXRsw0xgvmxNOT8mX4UaQe4ncdeXupXQ1wFyzBrrEbv5o6Nh1 uUd/M0XvLtvKdFv47F7o5XyjJAeJUR1Gu2xAq3GUhjduoAvAoS3itTTbVBi+e1UTeuAqGo0aB RnHbD2ziyYK10tZQt+q/ZlBDthNHhlaiG7og7GWVKSXpNKd0XrETXWW5N/Pf/WlyBK3TP3GmK SKjPj6cviTie72K9H8PoEZgHUZulIpjviioqP7GXP7lpSz48q3FE/DwQpELwk/1D9fD5mv7Km FyUY5uaC9M5aKCmBtKUWpnK1oPe94b52p0Zz/Oinh5UxMKWU5TGGjp3sIvG1pry7+zHjpYD5j /FaYRpddmz+OITzagWUbEpQUZVvjQw71yQ2jHMD1sKhaPL72BoX/GlJPtpRBqS6dsYkdY27ya /NoVvSOHZKPPOBdD+QWvOKwBmIJRqB8zKdWMAtUXUxnWNjm3fBgVKPlxBR5UeQnbkngr0skZ/ BCo4REWpmecc8S93xnPsHfblpBCgvD38YJDl8GDuM+LNc9JK7Lod60SsGY+DLdIXqT/idqX1Z QOa+0u5 Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Hi Zsolt, On Mon, 18 Jul 2016, Herczeg Zsolt wrote: > >> My point is not to throw out old hashes and break signatures. My point > >> is to convert the data storage, and use mapping to resolve problems > >> with those old hashes and signatures. > > > > If you convert the data storage, then the SHA-1s listed in the commit > > objects will have to be rewritten, and then the GPG signature will not > > match anymore. > > > > Call e.g. `git cat-file commit 44cc742a8ca17b9c279be4cc195a93a6ef7a320e` > > to see the anatomy of a gpg-signed commit object. > > > > Yes and no. That's the reason you need the two-way lookup table. If > you need to verify a commit which was signed as SHA-1, you must use > the lookup table in reverse. That pretends that it is both easy and trustworthy to know when (and how) to recreate the SHA-1-ified version of the commit object. Neither is the case, though. Ciao, Johannes