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 313DBC433F5 for ; Tue, 1 Feb 2022 12:33:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238140AbiBAMdt (ORCPT ); Tue, 1 Feb 2022 07:33:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55144 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237872AbiBAMdr (ORCPT ); Tue, 1 Feb 2022 07:33:47 -0500 Received: from smtp-8fab.mail.infomaniak.ch (smtp-8fab.mail.infomaniak.ch [IPv6:2001:1600:3:17::8fab]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8865EC061714 for ; Tue, 1 Feb 2022 04:33:47 -0800 (PST) Received: from smtp-2-0000.mail.infomaniak.ch (unknown [10.5.36.107]) by smtp-2-3000.mail.infomaniak.ch (Postfix) with ESMTPS id 4Jp49N58W8zMqFsJ; Tue, 1 Feb 2022 13:33:44 +0100 (CET) Received: from ns3096276.ip-94-23-54.eu (unknown [23.97.221.149]) by smtp-2-0000.mail.infomaniak.ch (Postfix) with ESMTPA id 4Jp49N1htQzlhSM8; Tue, 1 Feb 2022 13:33:44 +0100 (CET) Message-ID: <0d33f7cd-6846-5e7e-62b9-fbd0b28ecea9@digikod.net> Date: Tue, 1 Feb 2022 13:33:46 +0100 MIME-Version: 1.0 User-Agent: Content-Language: en-US To: Willem de Bruijn , Konstantin Meskhidze Cc: linux-security-module@vger.kernel.org, netdev@vger.kernel.org, netfilter@vger.kernel.org, yusongping@huawei.com, artem.kuzin@huawei.com References: <20220124080215.265538-1-konstantin.meskhidze@huawei.com> <20220124080215.265538-2-konstantin.meskhidze@huawei.com> <0934a27a-d167-87ea-97d2-b3ac952832ff@huawei.com> From: =?UTF-8?Q?Micka=c3=abl_Sala=c3=bcn?= Subject: Re: [RFC PATCH 1/2] landlock: TCP network hooks implementation In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 31/01/2022 18:14, Willem de Bruijn wrote: > On Fri, Jan 28, 2022 at 10:12 PM Konstantin Meskhidze > wrote: >> >> >> >> 1/26/2022 5:15 PM, Willem de Bruijn пишет: >>> On Wed, Jan 26, 2022 at 3:06 AM Konstantin Meskhidze >>> wrote: >>>> >>>> >>>> >>>> 1/25/2022 5:17 PM, Willem de Bruijn пишет: >>>>> On Mon, Jan 24, 2022 at 3:02 AM Konstantin Meskhidze >>>>> wrote: >>>>>> >>>>>> Support of socket_bind() and socket_connect() hooks. >>>>>> Current prototype can restrict binding and connecting of TCP >>>>>> types of sockets. Its just basic idea how Landlock could support >>>>>> network confinement. >>>>>> >>>>>> Changes: >>>>>> 1. Access masks array refactored into 1D one and changed >>>>>> to 32 bits. Filesystem masks occupy 16 lower bits and network >>>>>> masks reside in 16 upper bits. >>>>>> 2. Refactor API functions in ruleset.c: >>>>>> 1. Add void *object argument. >>>>>> 2. Add u16 rule_type argument. >>>>>> 3. Use two rb_trees in ruleset structure: >>>>>> 1. root_inode - for filesystem objects >>>>>> 2. root_net_port - for network port objects >>>>>> >>>>>> Signed-off-by: Konstantin Meskhidze >>>>> >>>>>> +static int hook_socket_connect(struct socket *sock, struct sockaddr *address, int addrlen) >>>>>> +{ >>>>>> + short socket_type; >>>>>> + struct sockaddr_in *sockaddr; >>>>>> + u16 port; >>>>>> + const struct landlock_ruleset *const dom = landlock_get_current_domain(); >>>>>> + >>>>>> + /* Check if the hook is AF_INET* socket's action */ >>>>>> + if ((address->sa_family != AF_INET) && (address->sa_family != AF_INET6)) >>>>>> + return 0; >>>>> >>>>> Should this be a check on the socket family (sock->ops->family) >>>>> instead of the address family? >>>> >>>> Actually connect() function checks address family: >>>> >>>> int __inet_stream_connect(... ,struct sockaddr *uaddr ,...) { >>>> ... >>>> if (uaddr) { >>>> if (addr_len < sizeof(uaddr->sa_family)) >>>> return -EINVAL; >>>> >>>> if (uaddr->sa_family == AF_UNSPEC) { >>>> err = sk->sk_prot->disconnect(sk, flags); >>>> sock->state = err ? SS_DISCONNECTING : >>>> SS_UNCONNECTED; >>>> goto out; >>>> } >>>> } >>>> >>>> ... >>>> } >>> >>> Right. My question is: is the intent of this feature to be limited to >>> sockets of type AF_INET(6) or to addresses? >>> >>> I would think the first. Then you also want to catch operations on >>> such sockets that may pass a different address family. AF_UNSPEC is >>> the known offender that will effect a state change on AF_INET(6) >>> sockets. >> >> The intent is to restrict INET sockets to bind/connect to some ports. >> You can apply some number of Landlock rules with port defenition: >> 1. Rule 1 allows to connect to sockets with port X. >> 2. Rule 2 forbids to connect to socket with port Y. >> 3. Rule 3 forbids to bind a socket to address with port Z. >> >> and so on... >>> >>>>> >>>>> It is valid to pass an address with AF_UNSPEC to a PF_INET(6) socket. >>>>> And there are legitimate reasons to want to deny this. Such as passing >>>>> a connection to a unprivileged process and disallow it from disconnect >>>>> and opening a different new connection. >>>> >>>> As far as I know using AF_UNSPEC to unconnect takes effect on >>>> UDP(DATAGRAM) sockets. >>>> To unconnect a UDP socket, we call connect but set the family member of >>>> the socket address structure (sin_family for IPv4 or sin6_family for >>>> IPv6) to AF_UNSPEC. It is the process of calling connect on an already >>>> connected UDP socket that causes the socket to become unconnected. >>>> >>>> This RFC patch just supports TCP connections. I need to check the logic >>>> if AF_UNSPEC provided in connenct() function for TCP(STREAM) sockets. >>>> Does it disconnect already established TCP connection? >>>> >>>> Thank you for noticing about this issue. Need to think through how >>>> to manage it with Landlock network restrictions for both TCP and UDP >>>> sockets. >>> >>> AF_UNSPEC also disconnects TCP. >> >> So its possible to call connect() with AF_UNSPEC and make a socket >> unconnected. If you want to establish another connection to a socket >> with port Y, and if there is a landlock rule has applied to a process >> (or container) which restricts to connect to a socket with port Y, it >> will be banned. >> Thats the basic logic. > > Understood, and that works fine for connect. It would be good to also > ensure that a now-bound socket cannot call listen. Possibly for > follow-on work. Are you thinking about a new access right for listen? What would be the use case vs. the bind access right?