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 13:28:07 +0100 [thread overview]
Message-ID: <9442f950-4d9e-cd76-0fc1-1c5f68f7f909@digikod.net> (raw)
In-Reply-To: <CA+FuTSc8ZAeaHWVYf-zmn6i5QLJysYGJppAEfb7tRbtho7_DKA@mail.gmail.com>
On 26/01/2022 15:15, Willem de Bruijn wrote:
> 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?
This feature should handle all "TCP" sockets/ports, IPv4 or IPv6 or
unspecified, the same way. What do you suggest to not miss corner cases?
What are the guarantees about socket types we can trust/rely on?
>
> 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.
Indeed, Landlock needs to handle this case to avoid bypasses. This must
be part of the tests.
>
>>>
>>> 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.
>
>>>
>>>> +
>>>> + 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);
>>>> +}
>>> .
next prev parent reply other threads:[~2022-02-01 12:28 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
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 [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=9442f950-4d9e-cd76-0fc1-1c5f68f7f909@digikod.net \
--to=mic@digikod.net \
--cc=artem.kuzin@huawei.com \
--cc=konstantin.meskhidze@huawei.com \
--cc=linux-security-module@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=netfilter@vger.kernel.org \
--cc=willemdebruijn.kernel@gmail.com \
--cc=yusongping@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).