From owner-freebsd-current@freebsd.org Mon Jan 4 21:44:12 2021 Return-Path: Delivered-To: freebsd-current@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id C6F5A4CDEF8 for ; Mon, 4 Jan 2021 21:44:12 +0000 (UTC) (envelope-from rysto32@gmail.com) Received: from mail-pf1-x433.google.com (mail-pf1-x433.google.com [IPv6:2607:f8b0:4864:20::433]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "smtp.gmail.com", Issuer "GTS CA 1O1" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4D8pzw0c62z4Yc1 for ; Mon, 4 Jan 2021 21:44:11 +0000 (UTC) (envelope-from rysto32@gmail.com) Received: by mail-pf1-x433.google.com with SMTP id a188so4519986pfa.11 for ; Mon, 04 Jan 2021 13:44:11 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=proIcBY+X8bI2RkviIOFM7wU17UUMI7DT3GKYdv2FxA=; b=JJ6y/IbQbOaof0yFKz7nWvCbrEXphuToBxi7MJP7V7gJyW7NUpyau2cD5UF562NCzs 4ak1pa8MQozd/oee37NiIHPE65xQnd/K2KIRinn7bhQhWyAo2oVfj7znQjrTu5RndNLX maC/+RDoVYyZxbBRQclUeEsLn88yIEppsKgepFxBcS+MPfx5d0p19MAWk/8qUVg/uK2c ptrHThmT+DcACpdRy8RrMyY6ZFSA14XLONlsF5aLlTlukBrFXdT13KWBJEUqLmaK8Pv8 LBvos1+MO3TXDm/s1nlrWfH2Ga84BtuhyAf5tqnjvT/KeNkPPHIaqbJgnV2jBZAREoWy IGng== X-Gm-Message-State: AOAM53148JQnvZswV6pEzkHyCS9+N6bZpQLRlvZ/fgehBzktQYN2BHgE 3DF/evm89YRuHJTBHS6N3qk8wYlhT6MDRX5affY= X-Google-Smtp-Source: ABdhPJyzdtQhfjFQBx03a4Ifs/kcohLmJyV0Oe5Ecz2UjXye5K0h8VzxR8YpU/Gtp5YnXirILpmZEfgIOejcUnl6sDw= X-Received: by 2002:a62:19cb:0:b029:19e:75c2:61ec with SMTP id 194-20020a6219cb0000b029019e75c261ecmr46536086pfz.19.1609796650774; Mon, 04 Jan 2021 13:44:10 -0800 (PST) MIME-Version: 1.0 References: <20201218182820.1P0tK%steffen@sdaoden.eu> <20201223023242.GG31099@funkthat.com> <20201223162417.v7Ce6%steffen@sdaoden.eu> <20201229011939.GU31099@funkthat.com> <20201229210454.Lh4y_%steffen@sdaoden.eu> <20201230004620.GB31099@funkthat.com> <20201231193908.GC31099@funkthat.com> <20210101165651.7319af5a@gumby.homeunix.com> <20210104193237.GD31099@funkthat.com> <95361.1609793029@critter.freebsd.dk> In-Reply-To: <95361.1609793029@critter.freebsd.dk> From: Ryan Stone Date: Mon, 4 Jan 2021 16:43:59 -0500 Message-ID: Subject: Re: HEADS UP: FreeBSD src repo transitioning to git this weekend To: Poul-Henning Kamp Cc: John-Mark Gurney , RW , FreeBSD Current Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 4D8pzw0c62z4Yc1 X-Spamd-Bar: --- X-Spamd-Result: default: False [-4.00 / 15.00]; R_SPF_ALLOW(-0.20)[+ip6:2607:f8b0:4000::/36:c]; FREEMAIL_FROM(0.00)[gmail.com]; TO_DN_ALL(0.00)[]; DKIM_TRACE(0.00)[gmail.com:+]; DMARC_POLICY_ALLOW(-0.50)[gmail.com,none]; NEURAL_HAM_SHORT(-1.00)[-1.000]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; RBL_DBL_DONT_QUERY_IPS(0.00)[2607:f8b0:4864:20::433:from]; FREEMAIL_ENVFROM(0.00)[gmail.com]; ASN(0.00)[asn:15169, ipnet:2607:f8b0::/32, country:US]; DWL_DNSWL_NONE(0.00)[gmail.com:dkim]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[gmail.com:s=20161025]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; NEURAL_HAM_LONG(-1.00)[-1.000]; MIME_GOOD(-0.10)[text/plain]; PREVIOUSLY_DELIVERED(0.00)[freebsd-current@freebsd.org]; SPAMHAUS_ZRD(0.00)[2607:f8b0:4864:20::433:from:127.0.2.255]; TO_MATCH_ENVRCPT_SOME(0.00)[]; RCVD_IN_DNSWL_NONE(0.00)[2607:f8b0:4864:20::433:from]; FREEMAIL_CC(0.00)[funkthat.com,googlemail.com,freebsd.org]; RCVD_TLS_ALL(0.00)[]; MAILMAN_DEST(0.00)[freebsd-current]; RCVD_COUNT_TWO(0.00)[2] X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 04 Jan 2021 21:44:12 -0000 On Mon, Jan 4, 2021 at 3:44 PM Poul-Henning Kamp wrote: > Shattered is less impressive when you take into account that you > can stuff as much much garbage into a PDF file as you need, without > affecting the files normal function. > > Compact data formats, formats which leave no wiggle-room and do not > offer extension-space for "attic-junk", are much harder to produce > *meaningful* collisions for. > > (I take no opinion in where git is on that spectrum.) FWIW, a coworker of mine had a little hobby of introducing commits into our internal repro that had hashes that all started with deadc0de. As I understand it, it was able to do this by adding an bogus attribute with the right value to the commit object. Now, brute-forcing 8 digits in the hash is one thing and doing it for all 40 is quite another, but I suspect that this demonstrates that it's *possible* to do it for a git hash, given enough computing resources.