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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 69BB7C07E9D for ; Sat, 3 Jul 2021 11:01:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4521461626 for ; Sat, 3 Jul 2021 11:01:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230196AbhGCLDm (ORCPT ); Sat, 3 Jul 2021 07:03:42 -0400 Received: from mout.gmx.net ([212.227.17.21]:53219 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230114AbhGCLDm (ORCPT ); Sat, 3 Jul 2021 07:03:42 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1625309984; bh=x6a2MKj2i7ny1X6EqqStry+6FExFMd0ABQRz2nQeLYo=; h=X-UI-Sender-Class:Date:From:To:Cc:Subject:References:In-Reply-To; b=Wiw7YHneNAj0vRJgTC3prnFX86jII+xEDVN++I+m01JfvLFWKYMxNJThVpPmfNaMr 0l1XkxxecRdMGd/ExVwB/L5tXY2XP/EGhE0aQbXZspLThbZgfj0sACe7WncRlHxXDF B6jPov8MEaN5iDIh2XMcRMHpdZpAmshp2gYuSPWM= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from ubuntu ([83.52.228.41]) by mail.gmx.net (mrgmx104 [212.227.17.174]) with ESMTPSA (Nemesis) id 1MC34X-1luSIn2S7R-00CSAc; Sat, 03 Jul 2021 12:59:44 +0200 Date: Sat, 3 Jul 2021 12:59:28 +0200 From: John Wood To: Alexander Lobakin Cc: John Wood , Kees Cook , Jann Horn , Jonathan Corbet , James Morris , "Serge E. Hallyn" , Shuah Khan , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Arnd Bergmann , Andi Kleen , valdis.kletnieks@vt.edu, Greg Kroah-Hartman , Randy Dunlap , Andrew Morton , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-arch@vger.kernel.org, linux-hardening@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: Re: [PATCH v8 3/8] security/brute: Detect a brute force attack Message-ID: <20210703105928.GA2830@ubuntu> References: <20210701234807.50453-1-alobakin@pm.me> <20210702145954.GA4513@ubuntu> <20210702170101.16116-1-alobakin@pm.me> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210702170101.16116-1-alobakin@pm.me> X-Provags-ID: V03:K1:IYa/f7HkDU74IlmbpIDqxZ4UnHLocuh2xK/SRcmGwjgHVE0HPwO uvk+ZKPo3XYM/EQ0BhfLQneFfb/z4C4sbQPYymJxVpCLHfTj4keZV746Dag/i+ohT+Tx1/V AzMPePnTmSZE/IiVBtMBldhthrEDhpmLHPUvlxEw3x6L7ewUJ/S8yXJnOJgUuMKIApCRwsB 4agKpfVPAEAY+DauJZ2HA== X-UI-Out-Filterresults: notjunk:1;V03:K0:DDK8tn1k2vk=:EF86SSfY5Vi1KOs8AADY/a 3Cq2nb4xqxxZWH6qOL0VjCqZO9d4DZ7Xx/yAQlHXGZaBU+BQ//fuZI6ljkHqeWhwUkyLivscc qJgrFJ313EhAax10IlN6i1M2HXjw7HFxHekHYXtWwHUYHiWGVHeFwp3HWdCHEbX21FM/z6bXL zbscFiWSbWbcUUPbI4VBKkn12UFjq4r/w+sJ3Wkjny6xTDMx8wbkpoSBxAt0PC2QPFtFZPuM2 sSm+saVCm0M1Eiqc9eizWMW64iyInEgBFtl/OJgcUzWq32x9bffwJ2rRgCSnXY24TrNgA0eo9 JuqFZjKk3zr/20QNa8alL/Szxz+uUm5vc26NKd1EUyj67cJ+MxBKjcZfRJ4UMeSWIz2rK2H/Y uNP6v0PiZxFM2+MrI8UWw4WB74DT8jySibpghnRylZJs0Zpxj488MnwjJpEcugPNQyH6TkvoV XyV+/H9qAca+7u803Q3j9Vd/CFiLjyg7/nNcVpWALQe2Yu6R/6OE8VjwSTFFj37xS7ZDhtQ29 xdJuoIZO7calbQyUhmUsCL2R38DX+T5ozjbZMc9nKiaTIWhqS70cw/HDnyAi+SYt+STd8Dc3h xeIMzJmj5dh47yDhj3YDLxvhLR1toQzatbzLPCnFzt8FflC/wTt5aLeCUlhgUjQXmEqCPKtKb 7klmaSE/q595gmB8f2vi9R2LVvqG1UnyniXMCPW8nK0M0fLu4A45lUI3YpltthQPiHyO6nFKq Q/EeJiCLhjlyXwrEVTEE0KXA0n7zeYn6YN8h+xbC5dVYHOuiyi/eHBVur9KI9YV8lvxIYngGL VhgBJG4qW9KikFkNqMW1vmycs/t4n3KK0LaIZ0mIWF9WbTi7L5Vmd5EddLHnus9fnZQ9uUMcJ Knw313I1cIzVHCWrbb2vGYEOmMWa+3833cxeeRkazB2b9GD8HV4otN6tlw0/5zPjSVSoNlDhn Vevn56H0Y2whovHFCeakw8UqVk0gBkGsJSAMKzdVigvQcZYJ1B2lvCBf4/KiJYCrBwLPc0M/t CVgINq6H165/dOQ56gS1Fn1YxsFGT8XM0HMzCXZPplvjeA2uDcschlVNk3gPtiXpax5kZoD76 SG2hbzUGdtKbMfttCXBP3mz/FXlbgtHans7 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org Hi, On Fri, Jul 02, 2021 at 05:08:09PM +0000, Alexander Lobakin wrote: > > On the other hand, it leaves a potentional window for attackers to > perform brute force from xattr-incapable filesystems. So at the end > of the day I think that the current implementation (a strong > rejection of such filesystems) is way more secure than having > a fallback I proposed. I've been thinking more about this: that the Brute LSM depends on xattr support and I don't like this part. I want that brute force attacks can be detected and mitigated on every system (with minimal dependencies). So, now I am working in a solution without this drawback. I have some ideas but I need to work on it. > I'm planning to make a patch which will eliminate such weird rootfs > type selection and just always use more feature-rich tmpfs if it's > compiled in. So, as an alternative, you could add it to your series > as a preparatory change and just add a Kconfig dependency on > CONFIG_TMPFS && CONFIG_TMPFS_XATTR to CONFIG_SECURITY_FORK_BRUTE > without messing with any fallbacks at all. > What do you think? Great. But I hope this patch will not be necessary for Brute LSM :) Thanks, John Wood