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Date: Thu, 6 Apr 2023 13:37:58 +0300
From: "Konstantin Meskhidze (A)" <konstantin.meskhidze@...wei.com>
To: Mickaël Salaün <mic@...ikod.net>
CC: <willemdebruijn.kernel@...il.com>, <gnoack3000@...il.com>,
<linux-security-module@...r.kernel.org>, <netdev@...r.kernel.org>,
<netfilter-devel@...r.kernel.org>, <yusongping@...wei.com>,
<artem.kuzin@...wei.com>
Subject: Re: [PATCH v10 09/13] landlock: Add network rules and TCP hooks
support
4/6/2023 1:31 PM, Mickaël Salaün пишет:
>
> On 05/04/2023 21:19, Konstantin Meskhidze (A) wrote:
>>
>>
>> 4/4/2023 8:02 PM, Mickaël Salaün пишет:
>>>
>>> On 04/04/2023 18:42, Mickaël Salaün wrote:
>>>>
>>>> On 04/04/2023 11:31, Konstantin Meskhidze (A) wrote:
>>>>>
>>>>>
>>>>> 3/31/2023 8:24 PM, Mickaël Salaün пишет:
>>>>>>
>>>>>> On 23/03/2023 09:52, Konstantin Meskhidze wrote:
>>>>>>> This commit adds network rules support in the ruleset management
>>>>>>> helpers and the landlock_create_ruleset syscall.
>>>>>>> Refactor user space API to support network actions. Add new network
>>>>>>> access flags, network rule and network attributes. Increment Landlock
>>>>>>> ABI version. Expand access_masks_t to u32 to be sure network access
>>>>>>> rights can be stored. Implement socket_bind() and socket_connect()
>>>>>>> LSM hooks, which enable to restrict TCP socket binding and connection
>>>>>>> to specific ports.
>>>>>>>
>>>>>>> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
>>>>>>> ---
>>>>>>>
>>>>>>> Changes since v9:
>>>>>>> * Changes UAPI port field to __u64.
>>>>>>> * Moves shared code into check_socket_access().
>>>>>>> * Adds get_raw_handled_net_accesses() and
>>>>>>> get_current_net_domain() helpers.
>>>>>>> * Minor fixes.
>>>>>>>
>>>>>>> Changes since v8:
>>>>>>> * Squashes commits.
>>>>>>> * Refactors commit message.
>>>>>>> * Changes UAPI port field to __be16.
>>>>>>> * Changes logic of bind/connect hooks with AF_UNSPEC families.
>>>>>>> * Adds address length checking.
>>>>>>> * Minor fixes.
>>>>>>>
>>>>>>> Changes since v7:
>>>>>>> * Squashes commits.
>>>>>>> * Increments ABI version to 4.
>>>>>>> * Refactors commit message.
>>>>>>> * Minor fixes.
>>>>>>>
>>>>>>> Changes since v6:
>>>>>>> * Renames landlock_set_net_access_mask() to landlock_add_net_access_mask()
>>>>>>> because it OR values.
>>>>>>> * Makes landlock_add_net_access_mask() more resilient incorrect values.
>>>>>>> * Refactors landlock_get_net_access_mask().
>>>>>>> * Renames LANDLOCK_MASK_SHIFT_NET to LANDLOCK_SHIFT_ACCESS_NET and use
>>>>>>> LANDLOCK_NUM_ACCESS_FS as value.
>>>>>>> * Updates access_masks_t to u32 to support network access actions.
>>>>>>> * Refactors landlock internal functions to support network actions with
>>>>>>> landlock_key/key_type/id types.
>>>>>>>
>>>>>>> Changes since v5:
>>>>>>> * Gets rid of partial revert from landlock_add_rule
>>>>>>> syscall.
>>>>>>> * Formats code with clang-format-14.
>>>>>>>
>>>>>>> Changes since v4:
>>>>>>> * Refactors landlock_create_ruleset() - splits ruleset and
>>>>>>> masks checks.
>>>>>>> * Refactors landlock_create_ruleset() and landlock mask
>>>>>>> setters/getters to support two rule types.
>>>>>>> * Refactors landlock_add_rule syscall add_rule_path_beneath
>>>>>>> function by factoring out get_ruleset_from_fd() and
>>>>>>> landlock_put_ruleset().
>>>>>>>
>>>>>>> Changes since v3:
>>>>>>> * Splits commit.
>>>>>>> * Adds network rule support for internal landlock functions.
>>>>>>> * Adds set_mask and get_mask for network.
>>>>>>> * Adds rb_root root_net_port.
>>>>>>>
>>>>>>> ---
>>>>>>> include/uapi/linux/landlock.h | 49 +++++
>>>>>>> security/landlock/Kconfig | 1 +
>>>>>>> security/landlock/Makefile | 2 +
>>>>>>> security/landlock/limits.h | 6 +-
>>>>>>> security/landlock/net.c | 198 +++++++++++++++++++
>>>>>>> security/landlock/net.h | 26 +++
>>>>>>> security/landlock/ruleset.c | 52 ++++-
>>>>>>> security/landlock/ruleset.h | 63 +++++-
>>>>>>> security/landlock/setup.c | 2 +
>>>>>>> security/landlock/syscalls.c | 72 ++++++-
>>>>>>> tools/testing/selftests/landlock/base_test.c | 2 +-
>>>>>>> 11 files changed, 450 insertions(+), 23 deletions(-)
>>>>>>> create mode 100644 security/landlock/net.c
>>>>>>> create mode 100644 security/landlock/net.h
>>>>>>
>>>>>> [...]
>>>>>>
>>>>>>> diff --git a/security/landlock/net.c b/security/landlock/net.c
>>>>>>
>>>>>> [...]
>>>
>>>
>>>>>>> +static int check_socket_access(struct socket *sock, struct sockaddr *address, int addrlen, u16 port,
>>>>>>> + access_mask_t access_request)
>>>>>>> +{
>>>>>>> + int ret;
>>>>>>> + bool allowed = false;
>>>>>>> + layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_NET] = {};
>>>>>>> + const struct landlock_rule *rule;
>>>>>>> + access_mask_t handled_access;
>>>>>>> + const struct landlock_id id = {
>>>>>>> + .key.data = port,
>>>>>>> + .type = LANDLOCK_KEY_NET_PORT,
>>>>>>> + };
>>>>>>> + const struct landlock_ruleset *const domain = get_current_net_domain();
>>>>>>> +
>>>>>>> + if (WARN_ON_ONCE(!domain))
>>>>>>> + return 0;
>>>>>>> + if (WARN_ON_ONCE(domain->num_layers < 1))
>>>>>>> + return -EACCES;
>>>>>>> + /* Check if it's a TCP socket. */
>>>>>>> + if (sock->type != SOCK_STREAM)
>>>>>>> + return 0;
>>>>>>> +
>>>>>>> + ret = check_addrlen(address, addrlen);
>>>>>>> + if (ret)
>>>>>>> + return ret;
>>>>>>> +
>>>>>>> + switch (address->sa_family) {
>>>>>>> + case AF_UNSPEC:
>>>>>>> + /*
>>>>>>> + * Connecting to an address with AF_UNSPEC dissolves the TCP
>>>>>>> + * association, which have the same effect as closing the
>>>>>>> + * connection while retaining the socket object (i.e., the file
>>>>>>> + * descriptor). As for dropping privileges, closing
>>>>>>> + * connections is always allowed.
>>>>>>> + */
>>>>>>> + if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP)
>>>>>>> + return 0;
>>>>>>> +
>>>>>>> + /*
>>>>>>> + * For compatibility reason, accept AF_UNSPEC for bind
>>>>>>> + * accesses (mapped to AF_INET) only if the address is
>>>>>>> + * INADDR_ANY (cf. __inet_bind). Checking the address is
>>>>>>> + * required to not wrongfully return -EACCES instead of
>>>>>>> + * -EAFNOSUPPORT.
>>>>>>> + */
>>>>>>> + if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP) {
>>>>>>> + const struct sockaddr_in *const sockaddr =
>>>>>>> + (struct sockaddr_in *)address;
>>>>>>> +
>>>>>>> + if (sockaddr->sin_addr.s_addr != htonl(INADDR_ANY))
>>>>>>> + return -EAFNOSUPPORT;
>>>>>>> + }
>>>>>>> +
>>>>>>> + fallthrough;
>>>>>>> + case AF_INET:
>>>>>>> +#if IS_ENABLED(CONFIG_IPV6)
>>>>>>> + case AF_INET6:
>>>>>>> +#endif
>>>
>>> Some more fixes:
>>>
>>> You can move the port/id.key.data block from my patch here, where it is
>>> actually used.
>>>
>> Ok. Thank you. I will apply it.
>>>
>>>>>>> + rule = landlock_find_rule(domain, id);
>>>>>>> + handled_access = landlock_init_layer_masks(
>>>>>>> + domain, access_request, &layer_masks,
>>>>>>> + LANDLOCK_KEY_NET_PORT);
>>>>>>> + allowed = landlock_unmask_layers(rule, handled_access,
>>>>>>> + &layer_masks,
>>>>>>> + ARRAY_SIZE(layer_masks));
>>>
>>> The `return allowed ? 0 : -EACCES;` should be here.
>>>
>>>>>>> + }
>>>>>>> + return allowed ? 0 : -EACCES;
>>>
>>> We should have `return 0;` here.
>>>
>> Got it. Thanks
>>
>>> We need a test for an sa_family different than AF_UNSPEC, AF_INET, and
>>> AF_INET6 to make sure everything else is allowed (e.g. AF_UNIX with
>>> SOCK_STREAM and another test with SOCK_DGRAM). Please make sure this new
>>> test will not pass with SOCK_STREAM and the current patch series, but of
>>> course it should pass with the next one.
>>
>> Do you mean AF_UNIX with SOCK_STREAM will not be passed as well as
>> AF_UNIX with SOCK_DGRAM?
>
> AF_UNIX with SOCK_STREAM would be denied with this patch series, which
> is a bug. AF_UNIX with SOCK_DGRAM should always be allowed with this
> patch series, which is correct.
>
> AF_UNIX with SOCK_STREAM or SOCK_DGRAM should always be allowed, and the
> next patch series should come with a new test to check this two kind of
> sockets.
Got it. Thanks.
> .
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