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=-8.3 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 6D292C433DF for ; Wed, 13 May 2020 19:50:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 12AAE205ED for ; Wed, 13 May 2020 19:50:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="AtuhJVK/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2403800AbgEMTuL (ORCPT ); Wed, 13 May 2020 15:50:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58478 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S2390793AbgEMTuK (ORCPT ); Wed, 13 May 2020 15:50:10 -0400 Received: from mail-qk1-x72f.google.com (mail-qk1-x72f.google.com [IPv6:2607:f8b0:4864:20::72f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C18C0C061A0E for ; Wed, 13 May 2020 12:50:10 -0700 (PDT) Received: by mail-qk1-x72f.google.com with SMTP id f83so529351qke.13 for ; Wed, 13 May 2020 12:50:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=AUaD8zHVYLcIfWsl1FLc6ajJYNyiXfBdqAf26hlsdlk=; b=AtuhJVK/9EjCL98+Yw35pZxzbfKOIo8uwjsEyXJI73TCo6OdEmzRCB6GafnVR/udUd Oms1h6C0cS889ZeX4eeSwZwBhQIVEU9SU8IYOM8rncYKW3ylm6QYFF4KFFFXDpgozwnv Im7XpENGDN0mEYdxgRWqZ62xHMtl34BWXWAClepMqE1OvqPrwLq47Z/fjJ/3HUP98gNt kikqlJQmIIqXPwC6TolLNm8BUOzrQrxfrrMKIl2ypWuYPn6QpCEcFpDswo13KpeiM5Io sFrmIkK9lmMTYHPLT/LBhLOZqT8dVZ4Z1cMeDO9fSQqy5v+vzLwBj70xlS5INn6B+5Zv lXkw== 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=AUaD8zHVYLcIfWsl1FLc6ajJYNyiXfBdqAf26hlsdlk=; b=Ir0sFdKnOpseLljsYwnZnWJBhMKt7Nt6vJhVVT8TPjooIT6ddD92jgEZj+0PhWmNTT yYRgAaPEu7HW8USoeL679Yri+tvCwOSloxDw2FOOKVlYrtksIEGVH0IDxkylNLpr7cV/ 2arCs7SUsw15v9p+T49RBTumV56/YUmW+FnHoQanH7SUT6YsCOFRcyTlKG6V9TpT5T94 gV+05szxlkWvfCewMCX0J0P7Y2NdEm7tvLqbkkViQQnym93PYX13ce026r5D3unsvn84 r24R+tmTjGeMd1Ed3rZ9mZtxb/A2oPXp4pBVygtrw8xMc+gP2JxSkfjZExVovBhiTF+B XQgA== X-Gm-Message-State: AOAM531i9+T9MdEgQNYqnJah3qFAxVoS24kKN9VYIIOb4wmC0EthMywx 1DMTcYRZdgNiTgT34GiTP0I4U4Kilbzz6ptRQiin8w== X-Google-Smtp-Source: ABdhPJzorgEMfRBdWZ+5yfHQMZz9u4bzScMyDeJDWPasebb9ILGmCbrD8VwbwlWw13jXYyklYFZf0RgLx00++YGlP34= X-Received: by 2002:a25:1484:: with SMTP id 126mr1118259ybu.380.1589399408708; Wed, 13 May 2020 12:50:08 -0700 (PDT) MIME-Version: 1.0 References: <341326348.19635.1589398715534.JavaMail.zimbra@efficios.com> In-Reply-To: <341326348.19635.1589398715534.JavaMail.zimbra@efficios.com> From: Eric Dumazet Date: Wed, 13 May 2020 12:49:57 -0700 Message-ID: Subject: Re: [regression] TC_MD5SIG on established sockets To: Mathieu Desnoyers Cc: "David S. Miller" , linux-kernel , netdev , Yuchung Cheng , Jonathan Rajotte-Julien Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I do not think we want to transition sockets in the middle. since packets can be re-ordered in the network. MD5 is about security (and a loose form of it), so better make sure all packets have it from the beginning of the flow. A flow with TCP TS on can not suddenly be sending packets without TCP TS. Clearly, trying to support this operation is a can of worms, I do not want to maintain such atrocity. RFC can state whatever it wants, sometimes reality forces us to have sane operations. Thanks. On Wed, May 13, 2020 at 12:38 PM Mathieu Desnoyers wrote: > > Hi, > > I am reporting a regression with respect to use of TCP_MD5SIG/TCP_MD5SIG_EXT > on established sockets. It is observed by a customer. > > This issue is introduced by this commit: > > commit 721230326891 "tcp: md5: reject TCP_MD5SIG or TCP_MD5SIG_EXT on established sockets" > > The intent of this commit appears to be to fix a use of uninitialized value in > tcp_parse_options(). The change introduced by this commit is to disallow setting > the TCP_MD5SIG{,_EXT} socket options on an established socket. > > The justification for this change appears in the commit message: > > "I believe this was caused by a TCP_MD5SIG being set on live > flow. > > This is highly unexpected, since TCP option space is limited. > > For instance, presence of TCP MD5 option automatically disables > TCP TimeStamp option at SYN/SYNACK time, which we can not do > once flow has been established. > > Really, adding/deleting an MD5 key only makes sense on sockets > in CLOSE or LISTEN state." > > However, reading through RFC2385 [1], this justification does not appear > correct. Quoting to the RFC: > > "This password never appears in the connection stream, and the actual > form of the password is up to the application. It could even change > during the lifetime of a particular connection so long as this change > was synchronized on both ends" > > The paragraph above clearly underlines that changing the MD5 signature of > a live TCP socket is allowed. > > I also do not understand why it would be invalid to transition an established > TCP socket from no-MD5 to MD5, or transition from MD5 to no-MD5. Quoting the > RFC: > > "The total header size is also an issue. The TCP header specifies > where segment data starts with a 4-bit field which gives the total > size of the header (including options) in 32-byte words. This means > that the total size of the header plus option must be less than or > equal to 60 bytes -- this leaves 40 bytes for options." > > The paragraph above seems to be the only indication that some TCP options > cannot be combined on a given TCP socket: if the resulting header size does > not fit. However, I do not see anything in the specification preventing any > of the following use-cases on an established TCP socket: > > - Transition from no-MD5 to MD5, > - Transition from MD5 to no-MD5, > - Changing the MD5 key associated with a socket. > > As long as the resulting combination of options does not exceed the available > header space. > > Can we please fix this KASAN report in a way that does not break user-space > applications expectations about Linux' implementation of RFC2385 ? > > Thanks, > > Mathieu > > [1] RFC2385: https://tools.ietf.org/html/rfc2385 > > -- > Mathieu Desnoyers > EfficiOS Inc. > http://www.efficios.com