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 D2E50C433F5 for ; Sat, 29 Jan 2022 03:12:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1352267AbiA2DMY (ORCPT ); Fri, 28 Jan 2022 22:12:24 -0500 Received: from frasgout.his.huawei.com ([185.176.79.56]:4558 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240864AbiA2DMY (ORCPT ); Fri, 28 Jan 2022 22:12:24 -0500 Received: from fraeml704-chm.china.huawei.com (unknown [172.18.147.226]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4JlzrV1LHzz67MLx; Sat, 29 Jan 2022 11:11:54 +0800 (CST) Received: from [10.122.132.241] (10.122.132.241) by fraeml704-chm.china.huawei.com (10.206.15.53) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2308.21; Sat, 29 Jan 2022 04:12:20 +0100 Message-ID: Date: Sat, 29 Jan 2022 06:12:19 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.4.1 Subject: Re: [RFC PATCH 1/2] landlock: TCP network hooks implementation Content-Language: ru To: Willem de Bruijn CC: , , , , , References: <20220124080215.265538-1-konstantin.meskhidze@huawei.com> <20220124080215.265538-2-konstantin.meskhidze@huawei.com> <0934a27a-d167-87ea-97d2-b3ac952832ff@huawei.com> From: Konstantin Meskhidze In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.122.132.241] X-ClientProxiedBy: lhreml754-chm.china.huawei.com (10.201.108.204) To fraeml704-chm.china.huawei.com (10.206.15.53) X-CFilter-Loop: Reflected Precedence: bulk List-ID: 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. > >>> >>>> + >>>> + socket_type = sock->type; >>>> + /* Check if it's a TCP socket */ >>>> + if (socket_type != SOCK_STREAM) >>>> + return 0; >>>> + >>>> + if (!dom) >>>> + return 0; >>>> + >>>> + /* Get port value in host byte order */ >>>> + sockaddr = (struct sockaddr_in *)address; >>>> + port = ntohs(sockaddr->sin_port); >>>> + >>>> + return check_socket_access(dom, port, LANDLOCK_ACCESS_NET_CONNECT_TCP); >>>> +} >>> . > .