From: "Mickaël Salaün" <mic@digikod.net>
To: Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Cc: linux-security-module@vger.kernel.org, netdev@vger.kernel.org,
netfilter@vger.kernel.org, yusongping@huawei.com,
artem.kuzin@huawei.com
Subject: Re: [RFC PATCH 1/2] landlock: TCP network hooks implementation
Date: Tue, 1 Feb 2022 13:33:46 +0100 [thread overview]
Message-ID: <0d33f7cd-6846-5e7e-62b9-fbd0b28ecea9@digikod.net> (raw)
In-Reply-To: <CA+FuTSeVhLdeXokyG4x__HGJyNOwsSicLOb4NKJA-gNp59S5uA@mail.gmail.com>
On 31/01/2022 18:14, Willem de Bruijn wrote:
> On Fri, Jan 28, 2022 at 10:12 PM Konstantin Meskhidze
> <konstantin.meskhidze@huawei.com> wrote:
>>
>>
>>
>> 1/26/2022 5:15 PM, Willem de Bruijn пишет:
>>> On Wed, Jan 26, 2022 at 3:06 AM Konstantin Meskhidze
>>> <konstantin.meskhidze@huawei.com> wrote:
>>>>
>>>>
>>>>
>>>> 1/25/2022 5:17 PM, Willem de Bruijn пишет:
>>>>> On Mon, Jan 24, 2022 at 3:02 AM Konstantin Meskhidze
>>>>> <konstantin.meskhidze@huawei.com> 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 <konstantin.meskhidze@huawei.com>
>>>>>
>>>>>> +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?
next prev parent reply other threads:[~2022-02-01 12:33 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-24 8:02 [RFC PATCH 0/2] landlock network implementation cover letter Konstantin Meskhidze
2022-01-24 8:02 ` [RFC PATCH 1/2] landlock: TCP network hooks implementation Konstantin Meskhidze
2022-01-25 14:17 ` Willem de Bruijn
2022-01-26 8:05 ` Konstantin Meskhidze
2022-01-26 14:15 ` Willem de Bruijn
2022-01-29 3:12 ` Konstantin Meskhidze
2022-01-31 17:14 ` Willem de Bruijn
2022-02-01 12:33 ` Mickaël Salaün [this message]
2022-02-07 2:31 ` Konstantin Meskhidze
2022-02-07 16:00 ` Willem de Bruijn
2022-02-07 16:17 ` Willem de Bruijn
2022-02-10 2:05 ` Konstantin Meskhidze
2022-02-10 2:04 ` Konstantin Meskhidze
2022-02-01 12:28 ` Mickaël Salaün
2022-02-07 2:35 ` Konstantin Meskhidze
2022-02-01 12:13 ` Mickaël Salaün
2022-02-07 13:09 ` Konstantin Meskhidze
2022-02-07 14:17 ` Mickaël Salaün
2022-02-08 7:55 ` Konstantin Meskhidze
2022-02-08 12:09 ` Mickaël Salaün
2022-02-09 3:06 ` Konstantin Meskhidze
2022-01-24 8:02 ` [RFC PATCH 2/2] landlock: selftests for bind and connect hooks Konstantin Meskhidze
2022-02-01 18:31 ` Mickaël Salaün
2022-02-07 7:11 ` Konstantin Meskhidze
2022-02-07 12:49 ` Mickaël Salaün
2022-02-08 3:01 ` Konstantin Meskhidze
2022-02-08 12:17 ` Mickaël Salaün
2022-02-09 3:03 ` Konstantin Meskhidze
2022-02-10 10:16 ` Mickaël Salaün
2022-02-24 3:18 ` Konstantin Meskhidze
2022-02-24 9:55 ` Mickaël Salaün
2022-02-24 12:03 ` Konstantin Meskhidze
2022-02-24 14:15 ` Mickaël Salaün
2022-02-25 2:44 ` Konstantin Meskhidze
2022-02-01 17:53 ` [RFC PATCH 0/2] landlock network implementation cover letter Mickaël Salaün
2022-02-07 13:18 ` Konstantin Meskhidze
2022-02-07 13:35 ` Mickaël Salaün
2022-02-08 3:53 ` Konstantin Meskhidze
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