From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7B2F1C4332F for ; Mon, 7 Nov 2022 21:24:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233341AbiKGVYB (ORCPT ); Mon, 7 Nov 2022 16:24:01 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46660 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232952AbiKGVXa (ORCPT ); Mon, 7 Nov 2022 16:23:30 -0500 Received: from mail-ed1-x52e.google.com (mail-ed1-x52e.google.com [IPv6:2a00:1450:4864:20::52e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2361E63F3 for ; Mon, 7 Nov 2022 13:23:29 -0800 (PST) Received: by mail-ed1-x52e.google.com with SMTP id v17so19644233edc.8 for ; Mon, 07 Nov 2022 13:23:28 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=S4A5U71pUqFrLPNtPdNvyjbt9IUVm6mWuZej8FN1CNA=; b=YCxNYUbs84TIQMP6S82WiehkIumNiCKJ4Ido1W6MIZwhKLIPz9OXJxM/Onkh/i+Y0k HRhwGJAyvIeWKY9HTwVlDPf2/oQTYzjB4fuha9VYaAvGkQN8P2nWas2NaB/hf/OUAsmw FyA0lAqp6DbcI5VpFD58LO2RmSCz4XOapCfZDbsGQ6KWFbC4MjywnVNbcSUAtRT4SzcD FFz2jNqmav/BPiONYN2tqeyxOU3y6x6iIex3hjZeqZ8UXI+anheroOCazWXGx11qxXLI zZTRYV+cZmBeLjtajn/twapY50vcpaFSMiLNYGNfpit5gCRnB4v00Kbz9aYp/S+T7jjL V8eA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=S4A5U71pUqFrLPNtPdNvyjbt9IUVm6mWuZej8FN1CNA=; b=IjRDoXzZte+wNIpBBFUYilkC38oI7IATACEU0Sy8WSEzXiIKoDOlYXN6UgCYo0ljRg 65ru670Ha3eFr0TIR7u22hTqY+Tg/ZlipCH7yQC934W4Dg01h5APwhvnCRocDSSs1qfK Cg3jrO4cQ3RY8upC0vEEd1jfXP5N3NhUIFhek5el+kWlN+bijL7w9sM7IudyPwZXui4O lDY9NDLlNRZjvp9aGZgVa2vBzoL2XRXK/WwuAtjQcByCnr67abDjW9q0QMMl9vNZMdnI nilxiBONddXcowIlEDZDU3GMVFeQhXq3HMo92VdnGQ2D44e308YF0DaxJ4ci9S/Nb84a EwPw== X-Gm-Message-State: ACrzQf2Gv2f+sdNatDsSQAlHv0bPQTf6hDVO2WqnmBuoX2wdmcmZm5X1 aaBcjzxnMBBDxgd5VvYV6x8jVs/zT6+3bQ== X-Google-Smtp-Source: AMsMyM7PdlmG9Ayj03uFFgzjrR32kQWtJEDyBWSyYCCxcipAbcsDInVsBIQQa3pqdmNaM+yJL5odtw== X-Received: by 2002:a05:6402:c07:b0:461:87ab:78aa with SMTP id co7-20020a0564020c0700b0046187ab78aamr53115063edb.258.1667856207176; Mon, 07 Nov 2022 13:23:27 -0800 (PST) Received: from vm.nix.is (vm.nix.is. [2a01:4f8:120:2468::2]) by smtp.gmail.com with ESMTPSA id gg3-20020a170906e28300b0077d6f628e14sm3834418ejb.83.2022.11.07.13.23.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Nov 2022 13:23:26 -0800 (PST) From: =?UTF-8?q?=C3=86var=20Arnfj=C3=B6r=C3=B0=20Bjarmason?= To: git@vger.kernel.org Cc: Junio C Hamano , Mike Hommey , "brian m . carlson" , =?UTF-8?q?Carlo=20Marcelo=20Arenas=20Bel=C3=B3n?= , Eric Sunshine , Glen Choo , Eric DeCosta , =?UTF-8?q?=C3=86var=20Arnfj=C3=B6r=C3=B0=20Bjarmason?= Subject: [PATCH v5 10/10] Makefile: discuss SHAttered in *_SHA{1,256} discussion Date: Mon, 7 Nov 2022 22:23:12 +0100 Message-Id: X-Mailer: git-send-email 2.38.0.1464.gea6794aacbc In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Let's mention the SHAttered attack and more generally why we use the sha1collisiondetection backend by default, and note that for SHA-256 the user should feel free to pick any of the supported backends as far as hashing security is concerned. Signed-off-by: Ævar Arnfjörð Bjarmason --- Makefile | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/Makefile b/Makefile index 7d0fa7adb61..91596bac4c0 100644 --- a/Makefile +++ b/Makefile @@ -481,6 +481,17 @@ include shared.mak # # === SHA-1 backend === # +# ==== Security ==== +# +# Due to the SHAttered (https://shattered.io) attack vector on SHA-1 +# it's strongly recommended to use the sha1collisiondetection +# counter-cryptanalysis library for SHA-1 hashing. +# +# If you know that you can trust the repository contents, or where +# potential SHA-1 attacks are otherwise mitigated the other backends +# listed in "SHA-1 implementations" are faster than +# sha1collisiondetection. +# # ==== Default SHA-1 backend ==== # # If no *_SHA1 backend is picked, the first supported one listed in @@ -525,6 +536,11 @@ include shared.mak # # === SHA-256 backend === # +# ==== Security ==== +# +# Unlike SHA-1 the SHA-256 algorithm does not suffer from any known +# vulnerabilities, so any implementation will do. +# # ==== SHA-256 implementations ==== # # Define OPENSSL_SHA256 to use the SHA-256 routines in OpenSSL. -- 2.38.0.1464.gea6794aacbc