Re: [PATCH v10 09/13] landlock: Add network rules and TCP hooks support

["Konstantin Meskhidze (A)" <konstantin.meskhidze@huawei.com>]

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@huawei.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.
> .