From: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
To: "Mickaël Salaün" <mic@digikod.net>
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 2/2] landlock: selftests for bind and connect hooks
Date: Wed, 9 Feb 2022 06:03:58 +0300 [thread overview]
Message-ID: <2aae376f-14df-2c69-204a-0de8e4b0dd74@huawei.com> (raw)
In-Reply-To: <d09ac689-b1bf-86fa-4da5-3a0ade7fd552@digikod.net>
2/8/2022 3:17 PM, Mickaël Salaün пишет:
>
> On 08/02/2022 04:01, Konstantin Meskhidze wrote:
>>
>>
>> 2/7/2022 3:49 PM, Mickaël Salaün пишет:
>
>>> [...]
>>>
>>>>>> + /* Create a socket 3 */
>>>>>> + sockfd_3 = socket(AF_INET, SOCK_STREAM, 0);
>>>>>> + ASSERT_LE(0, sockfd_3);
>>>>>> + /* Allow reuse of local addresses */
>>>>>> + ASSERT_EQ(0, setsockopt(sockfd_3, SOL_SOCKET, SO_REUSEADDR,
>>>>>> &one, sizeof(one)));
>>>>>> +
>>>>>> + /* Set socket 3 address parameters */
>>>>>> + addr_3.sin_family = AF_INET;
>>>>>> + addr_3.sin_port = htons(SOCK_PORT_3);
>>>>>> + addr_3.sin_addr.s_addr = inet_addr(IP_ADDRESS);
>>>>>> + memset(&(addr_3.sin_zero), '\0', 8);
>>>>>> + /* Bind the socket 3 to IP address */
>>>>>> + ASSERT_EQ(0, bind(sockfd_3, (struct sockaddr *)&addr_3,
>>>>>> sizeof(addr_3)));
>>>>>
>>>>> Why is it allowed to bind to SOCK_PORT_3 whereas net_service_3
>>>>> forbids it?
>>>>
>>>> It's allowed cause net_service_3 has empty access field.
>>>>
>>>> /* Empty allowed_access (i.e. deny rules) are ignored in network
>>>> * actions for SOCK_PORT_3 socket "object"
>>>> */
>>>> ASSERT_EQ(-1, landlock_add_rule(ruleset_fd,
>>>> LANDLOCK_RULE_NET_SERVICE,
>>>> &net_service_3, 0));
>>>> ASSERT_EQ(ENOMSG, errno);
>>>>
>>>> Applying this rule returns ENOMSG errno:
>>>>
>>>> /* Informs about useless rule: empty allowed_access (i.e. deny
>>>> rules)
>>>> * are ignored in network actions
>>>> */
>>>> if (!net_service_attr.allowed_access) {
>>>> err = -ENOMSG;
>>>> goto out_put_ruleset;
>>>> }
>>>> This means binding socket 3 is not restricted.
>>>> For path_beneath_attr.allowed_access = 0 there is the same logic.
>>>
>>> I missed the ENOMSG check; the third rule has nothing to do with it.
>>> However, because the ruleset handles bind and connect actions, they
>>> must be denied by default. There is no rule allowing binding to
>>> SOCK_PORT_3. Why is it allowed?
>>>
>>> You can test with another SOCK_PORT_4, not covered by any rule. As
>>> for SOCK_PORT_3, it must be forbidden to bind on it.
>>
>> Apllying the third rule (net_service_3.access is empty) returns ENOMSG
>> error. That means a process hasn't been restricted by the third rule,
>> cause during search process in network rb_tree the process won't find
>> the third rule, so binding to SOCK_PORT_3 is allowed.
>
> Landlock is designed to deny every access rights that are handled (by a
> ruleset) by default. All rules added to a ruleset are exceptions to
> allow a subset of the handled access rights on a specific object/port.
>
> With the current networking code, a sandboxed process can still bind or
> connect to any port except, in this test, partially for two ports. This
> approach doesn't help to isolate a process from the network.
I got it. Thanks.
>
>>
>> Maybe there is a misunderstanding here. You mean that if there is just
>> only one network rule for a particular port has been applied to a
>> process, other ports' networks actions are automatically restricted
>> until they will be added into landlock newtwork rb_tree?
>
> Right! That is how it should be.
So it possible to check network rb_tree for emptiness before
every rule search caused by bind/connect hooks.
Am I corrent that if there is a proccess with Landlcok restrictions
applied for the filesystem, but landlock networtk rb_tree is empty
that means the proccess is not isolated from the network? I suppose it
would be an additional test case.
> .
next prev parent reply other threads:[~2022-02-09 3:09 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
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 [this message]
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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