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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 B4DC5C433E1 for ; Mon, 15 Jun 2020 20:40:02 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7DAB5207D4 for ; Mon, 15 Jun 2020 20:40:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Mc7VwHDi" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7DAB5207D4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:33084 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jkvth-0001XL-Hc for qemu-devel@archiver.kernel.org; Mon, 15 Jun 2020 16:40:01 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:32804) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jkvsk-0000jW-HJ for qemu-devel@nongnu.org; Mon, 15 Jun 2020 16:39:02 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:28862 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jkvsh-0000EQ-MJ for qemu-devel@nongnu.org; Mon, 15 Jun 2020 16:39:02 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1592253537; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=GScIE0T57EzY0KODXhaabdjUxQFXnaCqRSQsDm3R8lo=; b=Mc7VwHDi3n/s7+g5WysOJmJaKibTTgp0TdKK1/Oo0T/L4mjHX7Lex66odlsbF5l6oA2TfQ REwSCW7TwZ2cZdz3p4nxsr63X4CIfK2U91xqmQdu6Ku30aNp5lRglG5f1xq57kZIutximg jXeOeC+Ka3aEihkdM1PsQmWJzz0FHdY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-444-yQNXFTlvPHaZR_IygzOELA-1; Mon, 15 Jun 2020 16:38:41 -0400 X-MC-Unique: yQNXFTlvPHaZR_IygzOELA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AB7241091320; Mon, 15 Jun 2020 20:38:40 +0000 (UTC) Received: from [10.3.112.27] (ovpn-112-27.phx2.redhat.com [10.3.112.27]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 021D419C79; Mon, 15 Jun 2020 20:38:39 +0000 (UTC) Subject: Re: [PATCH v2 1/2] nbd/server: Avoid long error message assertions CVE-2020-10761 From: Eric Blake To: qemu-devel@nongnu.org References: <20200610163741.3745251-1-eblake@redhat.com> <20200610163741.3745251-2-eblake@redhat.com> Organization: Red Hat, Inc. Message-ID: <1b590b1f-08b8-678f-c53d-794ca3dea812@redhat.com> Date: Mon, 15 Jun 2020 15:38:39 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200610163741.3745251-2-eblake@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=205.139.110.61; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/15 15:33:00 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , vsementsov@virtuozzo.com, qemu-block@nongnu.org, xuwei@redhat.com, qemu-stable@nongnu.org, Max Reitz , ppandit@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 6/10/20 11:37 AM, Eric Blake wrote: > We may later want to further sanitize the user-supplied strings we > place into our error messages, such as scrubbing out control > characters, but that is less important to the CVE fix, so it can be a > later patch to the new nbd_sanitize_name. > > +static char * > +nbd_sanitize_name(const char *name) > +{ > + if (strnlen(name, 80) < 80) { > + return g_strdup(name); > + } > + /* XXX Should we also try to sanitize any control characters? */ > + return g_strdup_printf("%.80s...", name); Max pointed out off-list that this can take a valid UTF-8 name from the client and truncate it mid-character to make our reply NOT valid UTF-8, which is a (minor) violation of the NBD protocol. We have not yet implemented strict UTF-8 enforcement in qemu (neither our client nor server code takes pains to only send UTF-8, nor validates that incoming strings are valid UTF-8); and while the server would previously echo non-UTF-8 (where the client violated protocol first), this is now a case where the server can be coerced into violating protocol first. I guess I may end up doing a followup patch that adds incoming validation and in the process avoids chopping a multi-byte character, but that's just as easy to fold in with my question about sanitizing control characters. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org