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

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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@xxxxxxxxxx>
---

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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