From owner-freebsd-current@freebsd.org Mon Jan 4 19:32:46 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 7928D4C7877 for ; Mon, 4 Jan 2021 19:32:46 +0000 (UTC) (envelope-from jmg@gold.funkthat.com) Received: from gold.funkthat.com (gate2.funkthat.com [208.87.223.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "gate2.funkthat.com", Issuer "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4D8m4F4ZVYz3rqf for ; Mon, 4 Jan 2021 19:32:45 +0000 (UTC) (envelope-from jmg@gold.funkthat.com) Received: from gold.funkthat.com (localhost [127.0.0.1]) by gold.funkthat.com (8.15.2/8.15.2) with ESMTPS id 104JWb3P082219 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Mon, 4 Jan 2021 11:32:38 -0800 (PST) (envelope-from jmg@gold.funkthat.com) Received: (from jmg@localhost) by gold.funkthat.com (8.15.2/8.15.2/Submit) id 104JWbkh082218; Mon, 4 Jan 2021 11:32:37 -0800 (PST) (envelope-from jmg) Date: Mon, 4 Jan 2021 11:32:37 -0800 From: John-Mark Gurney To: RW Cc: freebsd-current@freebsd.org Subject: Re: HEADS UP: FreeBSD src repo transitioning to git this weekend Message-ID: <20210104193237.GD31099@funkthat.com> Mail-Followup-To: RW , freebsd-current@freebsd.org 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210101165651.7319af5a@gumby.homeunix.com> X-Operating-System: FreeBSD 11.3-STABLE amd64 X-PGP-Fingerprint: D87A 235F FB71 1F3F 55B7 ED9B D5FF 5A51 C0AC 3D65 X-Files: The truth is out there X-URL: https://www.funkthat.com/ X-Resume: https://www.funkthat.com/~jmg/resume.html X-TipJar: bitcoin:13Qmb6AeTgQecazTWph4XasEsP7nGRbAPE X-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? User-Agent: Mutt/1.6.1 (2016-04-27) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.4.3 (gold.funkthat.com [127.0.0.1]); Mon, 04 Jan 2021 11:32:38 -0800 (PST) X-Rspamd-Queue-Id: 4D8m4F4ZVYz3rqf X-Spamd-Bar: - X-Spamd-Result: default: False [-1.80 / 15.00]; RCVD_TLS_ALL(0.00)[]; ARC_NA(0.00)[]; FREEFALL_USER(0.00)[jmg]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; NEURAL_HAM_MEDIUM(-1.00)[-1.000]; MID_RHS_MATCH_FROM(0.00)[]; MIME_GOOD(-0.10)[text/plain]; DMARC_NA(0.00)[funkthat.com]; RBL_DBL_DONT_QUERY_IPS(0.00)[208.87.223.18:from]; AUTH_NA(1.00)[]; SPAMHAUS_ZRD(0.00)[208.87.223.18:from:127.0.2.255]; TO_MATCH_ENVRCPT_SOME(0.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; RCPT_COUNT_TWO(0.00)[2]; NEURAL_HAM_SHORT(-1.00)[-1.000]; R_SPF_NA(0.00)[no SPF record]; FREEMAIL_TO(0.00)[googlemail.com]; FORGED_SENDER(0.30)[jmg@funkthat.com,jmg@gold.funkthat.com]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:32354, ipnet:208.87.216.0/21, country:US]; FROM_NEQ_ENVFROM(0.00)[jmg@funkthat.com,jmg@gold.funkthat.com]; 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 19:32:46 -0000 RW wrote this message on Fri, Jan 01, 2021 at 16:56 +0000: > On Thu, 31 Dec 2020 21:25:08 -0500 > grarpamp wrote: > > > > Is there any reason to think [bittorrent] insecure? > > > > Cost under $50k of compute to break sha-1, > > AFAIK you cannot break SHA-1 in the sense of creating data that > matches a specific hash. What you can do is create a collision between > two blocks of data, varying both blocks in the process. This makes > SHA-1 unsuitable for digital signatures. TL;DR: No, SHA-1 is broken. PERIOD. SHAttered[1] (2017) created two valid PDF documents which had the same SHA-1 hash. The issue was that they were able to choose the entire document. The paper released in 2019[2] and implemented in 2020 allows for chosen-prefix attacks[3] which means that SHA-1 is broken. It allows the creation of a different message prefix, but results in the same hash. Before this, git was "secure" in that objects were prepended w/ length and size, but w/ this latest attack, those can now be changed as well, allowing someone to wholesale replace a file in git w/ a different length, and the SHA-1 hash being the same. > A *third-party* attacker cannot create a bogus torrent using a > collision attack against SHA-1 because the attacker would need to match > a specific hash value. Wrong, see above. > What may be possible is that the creator of the legitimate torrent > might create two torrents with the same hash, but this seems very > contrived and not very useful. It has all sorts of problems as a way of > delivering targeted malware. Again, wrong. [1] https://en.wikipedia.org/wiki/SHA-1#SHAttered_%E2%80%93_first_public_collision [2] https://en.wikipedia.org/wiki/SHA-1#Birthday-Near-Collision_Attack_%E2%80%93_first_practical_chosen-prefix_attack [3] https://en.wikipedia.org/wiki/Collision_attack#Chosen-prefix_collision_attack -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."