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 5D052C433DF for ; Wed, 13 May 2020 19:56:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E7ED0205ED for ; Wed, 13 May 2020 19:56:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="fhdJx2rq" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390827AbgEMT4o (ORCPT ); Wed, 13 May 2020 15:56:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59498 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S2390687AbgEMT4o (ORCPT ); Wed, 13 May 2020 15:56:44 -0400 Received: from mail-qk1-x729.google.com (mail-qk1-x729.google.com [IPv6:2607:f8b0:4864:20::729]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A1852C061A0C for ; Wed, 13 May 2020 12:56:42 -0700 (PDT) Received: by mail-qk1-x729.google.com with SMTP id g185so606944qke.7 for ; Wed, 13 May 2020 12:56:42 -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=0GFIUDstFYl47OE0S5dumvGBoOXhEcqpXzIXXnwWLGc=; b=fhdJx2rqzk2VBm+S7aXWXMmQoqgSad2dGTC9La2Q5wWNYw+nk3ue4Z3AltjDtKqRZw jdcTmQZ9OH4JyCaL2AlyHcZmTLxW3OSA6x26BPXwaVK0brgB1igUXWRQBmf/nRW8h104 DUW2JF36mXR31JLaL2LyzvcWDMGwdyKAH45WdiYsCE011NTLvi6s+gpxV/IwWplmDBCK NVtbBkoPE0SU636I9eASJjoNxwz4jh60gCITGok8yl0oI4n5880jLJ3WZ7WnnzwywgRl 6jFbxySy5bYHMHM2wK/FsC/7bNfWBXYzT6j96LzaCS8VFAGGRyGCrl4vgGClcwVypg6G KMCg== 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=0GFIUDstFYl47OE0S5dumvGBoOXhEcqpXzIXXnwWLGc=; b=GX3I1GtgqRE3f/KJrH84APXjTdvJmC5Vgaf0/Gcddr8QcdOaRb94fa5v8KZL/lzY8j DxYfWYwvm81jJwsqDXU6X3OmCeD8otdBv5xCmXRWjBJU+iNjfipfi+DahmNfTR74LYxJ kLPb2haMmmmz5DkpXI7/eUN9tDnDmJuN/OZABUZXTq7W634EvzQDYa2EAnIFA1Yj7zQr GJZ0jwVVpjhhZyCs7A60cMySJ3kAcqHpqLS+Wi7FvQzRShFoR0Jm4IXumBaINiKVa67Q DWNY7rPpqq4cMde0g85xwfbDsrkoiJl7x8AyoJ9hhMrqMZx/qBBdrEP8jZw5GjMoXTIn 3A7A== X-Gm-Message-State: AOAM531oYqGhXQDV/XFz+Jvi1Gnk0ZrwwVaW229IDsy4qzEoRmrHlMIS JJGYGY2ELQZi9ryDvcphwVZ7aEAZz+8mLP5W2wqRjw== X-Google-Smtp-Source: ABdhPJwdY2fxfp0XGP0xEvkEmLoMrHZlMceoFvX/apNQdlp9i1pSKwGUYVCY4+UsXOtNif0KPeoGoP7bAPi8hE1mUDs= X-Received: by 2002:a25:8182:: with SMTP id p2mr1189542ybk.408.1589399801510; Wed, 13 May 2020 12:56:41 -0700 (PDT) MIME-Version: 1.0 References: <341326348.19635.1589398715534.JavaMail.zimbra@efficios.com> In-Reply-To: From: Eric Dumazet Date: Wed, 13 May 2020 12:56:30 -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 On Wed, May 13, 2020 at 12:49 PM Eric Dumazet wrote: > > 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. Also the RFC states : "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" It means the key can be changed, but this does not imply the option can be turned on/off dynamically. > > 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