[PATCH v11 08/12] landlock: Add network rules and TCP hooks support

[Konstantin Meskhidze <konstantin.meskhidze@huawei.com>]

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 enables to restrict TCP socket binding and connection
to specific ports.

Co-developed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
---

Changes since v10:
* Removes "packed" attribute.
* Applies Mickaёl's patch with some refactoring.
* Deletes get_port() and check_addrlen() helpers.
* Refactors check_socket_access() by squashing get_port() and
check_addrlen() helpers into it.
* Fixes commit message.

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                |  48 +++++
 security/landlock/Kconfig                    |   1 +
 security/landlock/Makefile                   |   2 +
 security/landlock/limits.h                   |   6 +-
 security/landlock/net.c                      | 174 +++++++++++++++++++
 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, 425 insertions(+), 23 deletions(-)
 create mode 100644 security/landlock/net.c
 create mode 100644 security/landlock/net.h

diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
index 81d09ef9aa50..93794759dad4 100644
--- a/include/uapi/linux/landlock.h
+++ b/include/uapi/linux/landlock.h
@@ -31,6 +31,13 @@ struct landlock_ruleset_attr {
 	 * this access right.
 	 */
 	__u64 handled_access_fs;
+
+	/**
+	 * @handled_access_net: Bitmask of actions (cf. `Network flags`_)
+	 * that is handled by this ruleset and should then be forbidden if no
+	 * rule explicitly allow them.
+	 */
+	__u64 handled_access_net;
 };

 /*
@@ -54,6 +61,11 @@ enum landlock_rule_type {
 	 * landlock_path_beneath_attr .
 	 */
 	LANDLOCK_RULE_PATH_BENEATH = 1,
+	/**
+	 * @LANDLOCK_RULE_NET_SERVICE: Type of a &struct
+	 * landlock_net_service_attr .
+	 */
+	LANDLOCK_RULE_NET_SERVICE = 2,
 };

 /**
@@ -79,6 +91,23 @@ struct landlock_path_beneath_attr {
 	 */
 } __attribute__((packed));

+/**
+ * struct landlock_net_service_attr - TCP subnet definition
+ *
+ * Argument of sys_landlock_add_rule().
+ */
+struct landlock_net_service_attr {
+	/**
+	 * @allowed_access: Bitmask of allowed access network for services
+	 * (cf. `Network flags`_).
+	 */
+	__u64 allowed_access;
+	/**
+	 * @port: Network port.
+	 */
+	__u64 port;
+};
+
 /**
  * DOC: fs_access
  *
@@ -189,4 +218,23 @@ struct landlock_path_beneath_attr {
 #define LANDLOCK_ACCESS_FS_TRUNCATE			(1ULL << 14)
 /* clang-format on */

+/**
+ * DOC: net_access
+ *
+ * Network flags
+ * ~~~~~~~~~~~~~~~~
+ *
+ * These flags enable to restrict a sandboxed process to a set of network
+ * actions.
+ *
+ * TCP sockets with allowed actions:
+ *
+ * - %LANDLOCK_ACCESS_NET_BIND_TCP: Bind a TCP socket to a local port.
+ * - %LANDLOCK_ACCESS_NET_CONNECT_TCP: Connect an active TCP socket to
+ *   a remote port.
+ */
+/* clang-format off */
+#define LANDLOCK_ACCESS_NET_BIND_TCP			(1ULL << 0)
+#define LANDLOCK_ACCESS_NET_CONNECT_TCP			(1ULL << 1)
+/* clang-format on */
 #endif /* _UAPI_LINUX_LANDLOCK_H */
diff --git a/security/landlock/Kconfig b/security/landlock/Kconfig
index 8e33c4e8ffb8..10c099097533 100644
--- a/security/landlock/Kconfig
+++ b/security/landlock/Kconfig
@@ -3,6 +3,7 @@
 config SECURITY_LANDLOCK
 	bool "Landlock support"
 	depends on SECURITY && !ARCH_EPHEMERAL_INODES
+	select SECURITY_NETWORK
 	select SECURITY_PATH
 	help
 	  Landlock is a sandboxing mechanism that enables processes to restrict
diff --git a/security/landlock/Makefile b/security/landlock/Makefile
index 7bbd2f413b3e..53d3c92ae22e 100644
--- a/security/landlock/Makefile
+++ b/security/landlock/Makefile
@@ -2,3 +2,5 @@ obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o

 landlock-y := setup.o syscalls.o object.o ruleset.o \
 	cred.o ptrace.o fs.o
+
+landlock-$(CONFIG_INET) += net.o
\ No newline at end of file
diff --git a/security/landlock/limits.h b/security/landlock/limits.h
index bafb3b8dc677..8a1a6463c64e 100644
--- a/security/landlock/limits.h
+++ b/security/landlock/limits.h
@@ -23,6 +23,10 @@
 #define LANDLOCK_NUM_ACCESS_FS		__const_hweight64(LANDLOCK_MASK_ACCESS_FS)
 #define LANDLOCK_SHIFT_ACCESS_FS	0

-/* clang-format on */
+#define LANDLOCK_LAST_ACCESS_NET	LANDLOCK_ACCESS_NET_CONNECT_TCP
+#define LANDLOCK_MASK_ACCESS_NET	((LANDLOCK_LAST_ACCESS_NET << 1) - 1)
+#define LANDLOCK_NUM_ACCESS_NET		__const_hweight64(LANDLOCK_MASK_ACCESS_NET)
+#define LANDLOCK_SHIFT_ACCESS_NET	LANDLOCK_NUM_ACCESS_FS

+/* clang-format on */
 #endif /* _SECURITY_LANDLOCK_LIMITS_H */
diff --git a/security/landlock/net.c b/security/landlock/net.c
new file mode 100644
index 000000000000..f8d2be53ac0d
--- /dev/null
+++ b/security/landlock/net.c
@@ -0,0 +1,174 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Landlock LSM - Network management and hooks
+ *
+ * Copyright © 2022 Huawei Tech. Co., Ltd.
+ * Copyright © 2022 Microsoft Corporation
+ */
+
+#include <linux/in.h>
+#include <linux/net.h>
+#include <linux/socket.h>
+#include <net/ipv6.h>
+
+#include "common.h"
+#include "cred.h"
+#include "limits.h"
+#include "net.h"
+#include "ruleset.h"
+
+int landlock_append_net_rule(struct landlock_ruleset *const ruleset,
+			     const u16 port, access_mask_t access_rights)
+{
+	int err;
+	const struct landlock_id id = {
+		.key.data = (__force uintptr_t)htons(port),
+		.type = LANDLOCK_KEY_NET_PORT,
+	};
+
+	BUILD_BUG_ON(sizeof(port) > sizeof(id.key.data));
+
+	/* Transforms relative access rights to absolute ones. */
+	access_rights |= LANDLOCK_MASK_ACCESS_NET &
+			 ~landlock_get_net_access_mask(ruleset, 0);
+
+	mutex_lock(&ruleset->lock);
+	err = landlock_insert_rule(ruleset, id, access_rights);
+	mutex_unlock(&ruleset->lock);
+
+	return err;
+}
+
+static access_mask_t
+get_raw_handled_net_accesses(const struct landlock_ruleset *const domain)
+{
+	access_mask_t access_dom = 0;
+	size_t layer_level;
+
+	for (layer_level = 0; layer_level < domain->num_layers; layer_level++)
+		access_dom |= landlock_get_net_access_mask(domain, layer_level);
+	return access_dom;
+}
+
+static const struct landlock_ruleset *get_current_net_domain(void)
+{
+	const struct landlock_ruleset *const dom =
+		landlock_get_current_domain();
+
+	if (!dom || !get_raw_handled_net_accesses(dom))
+		return NULL;
+
+	return dom;
+}
+
+static int check_socket_access(struct socket *const sock,
+			       struct sockaddr *const address,
+			       const int addrlen,
+			       const access_mask_t access_request)
+{
+	__be16 port;
+	layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_NET] = {};
+	const struct landlock_rule *rule;
+	access_mask_t handled_access;
+	struct landlock_id id = {
+		.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;
+
+	/* Checks if it's a TCP socket. */
+	if (sock->type != SOCK_STREAM)
+		return 0;
+
+	/* Checks for minimal header length. */
+	if (addrlen < offsetofend(struct sockaddr, sa_family))
+		return -EINVAL;
+
+	switch (address->sa_family) {
+	case AF_UNSPEC:
+	case AF_INET:
+		if (addrlen < sizeof(struct sockaddr_in))
+			return -EINVAL;
+		port = ((struct sockaddr_in *)address)->sin_port;
+		break;
+#if IS_ENABLED(CONFIG_IPV6)
+	case AF_INET6:
+		if (addrlen < SIN6_LEN_RFC2133)
+			return -EINVAL;
+		port = ((struct sockaddr_in6 *)address)->sin6_port;
+		break;
+#endif
+	default:
+		return 0;
+	}
+
+	/* Specific AF_UNSPEC handling. */
+	if (address->sa_family == 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;
+		}
+	}
+
+	id.key.data = (__force uintptr_t)port;
+	BUILD_BUG_ON(sizeof(port) > sizeof(id.key.data));
+
+	rule = landlock_find_rule(domain, id);
+	handled_access = landlock_init_layer_masks(
+		domain, access_request, &layer_masks, LANDLOCK_KEY_NET_PORT);
+	if (landlock_unmask_layers(rule, handled_access, &layer_masks,
+				   ARRAY_SIZE(layer_masks)))
+		return 0;
+
+	return -EACCES;
+}
+
+static int hook_socket_bind(struct socket *const sock,
+			    struct sockaddr *const address, const int addrlen)
+{
+	return check_socket_access(sock, address, addrlen,
+				   LANDLOCK_ACCESS_NET_BIND_TCP);
+}
+
+static int hook_socket_connect(struct socket *const sock,
+			       struct sockaddr *const address,
+			       const int addrlen)
+{
+	return check_socket_access(sock, address, addrlen,
+				   LANDLOCK_ACCESS_NET_CONNECT_TCP);
+}
+
+static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = {
+	LSM_HOOK_INIT(socket_bind, hook_socket_bind),
+	LSM_HOOK_INIT(socket_connect, hook_socket_connect),
+};
+
+__init void landlock_add_net_hooks(void)
+{
+	security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
+			   LANDLOCK_NAME);
+}
diff --git a/security/landlock/net.h b/security/landlock/net.h
new file mode 100644
index 000000000000..0da1d9dff5ab
--- /dev/null
+++ b/security/landlock/net.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Landlock LSM - Network management and hooks
+ *
+ * Copyright © 2022 Huawei Tech. Co., Ltd.
+ */
+
+#ifndef _SECURITY_LANDLOCK_NET_H
+#define _SECURITY_LANDLOCK_NET_H
+
+#include "common.h"
+#include "ruleset.h"
+#include "setup.h"
+
+#if IS_ENABLED(CONFIG_INET)
+__init void landlock_add_net_hooks(void);
+
+int landlock_append_net_rule(struct landlock_ruleset *const ruleset,
+			     const u16 port, access_mask_t access_rights);
+#else /* IS_ENABLED(CONFIG_INET) */
+static inline void landlock_add_net_hooks(void)
+{
+}
+#endif /* IS_ENABLED(CONFIG_INET) */
+
+#endif /* _SECURITY_LANDLOCK_NET_H */
diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index b07ad57ee40a..fa1f45587830 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -36,6 +36,9 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
 	refcount_set(&new_ruleset->usage, 1);
 	mutex_init(&new_ruleset->lock);
 	new_ruleset->root_inode = RB_ROOT;
+#if IS_ENABLED(CONFIG_INET)
+	new_ruleset->root_net_port = RB_ROOT;
+#endif /* IS_ENABLED(CONFIG_INET) */
 	new_ruleset->num_layers = num_layers;
 	/*
 	 * hierarchy = NULL
@@ -46,16 +49,21 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
 }

 struct landlock_ruleset *
-landlock_create_ruleset(const access_mask_t fs_access_mask)
+landlock_create_ruleset(const access_mask_t fs_access_mask,
+			const access_mask_t net_access_mask)
 {
 	struct landlock_ruleset *new_ruleset;

 	/* Informs about useless ruleset. */
-	if (!fs_access_mask)
+	if (!fs_access_mask && !net_access_mask)
 		return ERR_PTR(-ENOMSG);
 	new_ruleset = create_ruleset(1);
-	if (!IS_ERR(new_ruleset))
+	if (IS_ERR(new_ruleset))
+		return new_ruleset;
+	if (fs_access_mask)
 		landlock_add_fs_access_mask(new_ruleset, fs_access_mask, 0);
+	if (net_access_mask)
+		landlock_add_net_access_mask(new_ruleset, net_access_mask, 0);
 	return new_ruleset;
 }

@@ -73,6 +81,10 @@ static bool is_object_pointer(const enum landlock_key_type key_type)
 	switch (key_type) {
 	case LANDLOCK_KEY_INODE:
 		return true;
+#if IS_ENABLED(CONFIG_INET)
+	case LANDLOCK_KEY_NET_PORT:
+		return false;
+#endif /* IS_ENABLED(CONFIG_INET) */
 	}
 	WARN_ON_ONCE(1);
 	return false;
@@ -126,6 +138,11 @@ static struct rb_root *get_root(struct landlock_ruleset *const ruleset,
 	case LANDLOCK_KEY_INODE:
 		root = &ruleset->root_inode;
 		break;
+#if IS_ENABLED(CONFIG_INET)
+	case LANDLOCK_KEY_NET_PORT:
+		root = &ruleset->root_net_port;
+		break;
+#endif /* IS_ENABLED(CONFIG_INET) */
 	}
 	if (WARN_ON_ONCE(!root))
 		return ERR_PTR(-EINVAL);
@@ -154,7 +171,8 @@ static void build_check_ruleset(void)
 	BUILD_BUG_ON(ruleset.num_rules < LANDLOCK_MAX_NUM_RULES);
 	BUILD_BUG_ON(ruleset.num_layers < LANDLOCK_MAX_NUM_LAYERS);
 	BUILD_BUG_ON(access_masks <
-		     (LANDLOCK_MASK_ACCESS_FS << LANDLOCK_SHIFT_ACCESS_FS));
+		     ((LANDLOCK_MASK_ACCESS_FS << LANDLOCK_SHIFT_ACCESS_FS) |
+		      (LANDLOCK_MASK_ACCESS_NET << LANDLOCK_SHIFT_ACCESS_NET)));
 }

 /**
@@ -373,6 +391,12 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
 	if (err)
 		goto out_unlock;

+#if IS_ENABLED(CONFIG_INET)
+	/* Merges the @src network port tree. */
+	err = merge_tree(dst, src, LANDLOCK_KEY_NET_PORT);
+	if (err)
+		goto out_unlock;
+#endif /* IS_ENABLED(CONFIG_INET) */
 out_unlock:
 	mutex_unlock(&src->lock);
 	mutex_unlock(&dst->lock);
@@ -429,6 +453,12 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,
 	if (err)
 		goto out_unlock;

+#if IS_ENABLED(CONFIG_INET)
+	/* Copies the @parent network port tree. */
+	err = inherit_tree(parent, child, LANDLOCK_KEY_NET_PORT);
+	if (err)
+		goto out_unlock;
+#endif /* IS_ENABLED(CONFIG_INET) */
 	if (WARN_ON_ONCE(child->num_layers <= parent->num_layers)) {
 		err = -EINVAL;
 		goto out_unlock;
@@ -461,6 +491,11 @@ static void free_ruleset(struct landlock_ruleset *const ruleset)
 	rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root_inode,
 					     node)
 		free_rule(freeme, LANDLOCK_KEY_INODE);
+#if IS_ENABLED(CONFIG_INET)
+	rbtree_postorder_for_each_entry_safe(freeme, next,
+					     &ruleset->root_net_port, node)
+		free_rule(freeme, LANDLOCK_KEY_NET_PORT);
+#endif /* IS_ENABLED(CONFIG_INET) */
 	put_hierarchy(ruleset->hierarchy);
 	kfree(ruleset);
 }
@@ -641,7 +676,8 @@ get_access_mask_t(const struct landlock_ruleset *const ruleset,
  *
  * @domain: The domain that defines the current restrictions.
  * @access_request: The requested access rights to check.
- * @layer_masks: The layer masks to populate.
+ * @layer_masks: It must contain LANDLOCK_NUM_ACCESS_FS or LANDLOCK_NUM_ACCESS_NET
+ * elements according to @key_type.
  * @key_type: The key type to switch between access masks of different types.
  *
  * Returns: An access mask where each access right bit is set which is handled
@@ -662,6 +698,12 @@ landlock_init_layer_masks(const struct landlock_ruleset *const domain,
 		get_access_mask = landlock_get_fs_access_mask;
 		num_access = LANDLOCK_NUM_ACCESS_FS;
 		break;
+#if IS_ENABLED(CONFIG_INET)
+	case LANDLOCK_KEY_NET_PORT:
+		get_access_mask = landlock_get_net_access_mask;
+		num_access = LANDLOCK_NUM_ACCESS_NET;
+		break;
+#endif /* IS_ENABLED(CONFIG_INET) */
 	default:
 		WARN_ON_ONCE(1);
 		return 0;
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index 2251e6048ccf..dcf7fbac8367 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -33,13 +33,16 @@
 typedef u16 access_mask_t;
 /* Makes sure all filesystem access rights can be stored. */
 static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS);
+/* Makes sure all network access rights can be stored. */
+static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_NET);
 /* Makes sure for_each_set_bit() and for_each_clear_bit() calls are OK. */
 static_assert(sizeof(unsigned long) >= sizeof(access_mask_t));

 /* Ruleset access masks. */
-typedef u16 access_masks_t;
+typedef u32 access_masks_t;
 /* Makes sure all ruleset access rights can be stored. */
-static_assert(BITS_PER_TYPE(access_masks_t) >= LANDLOCK_NUM_ACCESS_FS);
+static_assert(BITS_PER_TYPE(access_masks_t) >=
+	      LANDLOCK_NUM_ACCESS_FS + LANDLOCK_NUM_ACCESS_NET);

 typedef u16 layer_mask_t;
 /* Makes sure all layers can be checked. */
@@ -84,6 +87,13 @@ enum landlock_key_type {
 	 * keys.
 	 */
 	LANDLOCK_KEY_INODE = 1,
+#if IS_ENABLED(CONFIG_INET)
+	/**
+	 * @LANDLOCK_KEY_NET_PORT: Type of &landlock_ruleset.root_net_port's
+	 * node keys.
+	 */
+	LANDLOCK_KEY_NET_PORT = 2,
+#endif /* IS_ENABLED(CONFIG_INET) */
 };

 /**
@@ -158,6 +168,15 @@ struct landlock_ruleset {
 	 * reaches zero.
 	 */
 	struct rb_root root_inode;
+#if IS_ENABLED(CONFIG_INET)
+	/**
+	 * @root_net_port: Root of a red-black tree containing &struct
+	 * landlock_rule nodes with network port. Once a ruleset is tied to a
+	 * process (i.e. as a domain), this tree is immutable until @usage
+	 * reaches zero.
+	 */
+	struct rb_root root_net_port;
+#endif /* IS_ENABLED(CONFIG_INET) */
 	/**
 	 * @hierarchy: Enables hierarchy identification even when a parent
 	 * domain vanishes.  This is needed for the ptrace protection.
@@ -196,13 +215,13 @@ struct landlock_ruleset {
 			 */
 			u32 num_layers;
 			/**
-			 * @access_masks: Contains the subset of filesystem
-			 * actions that are restricted by a ruleset.  A domain
-			 * saves all layers of merged rulesets in a stack
-			 * (FAM), starting from the first layer to the last
-			 * one.  These layers are used when merging rulesets,
-			 * for user space backward compatibility (i.e.
-			 * future-proof), and to properly handle merged
+			 * @access_masks: Contains the subset of filesystem and
+			 * network actions that are restricted by a ruleset.
+			 * A domain saves all layers of merged rulesets in a
+			 * stack (FAM), starting from the first layer to the
+			 * last one.  These layers are used when merging
+			 * rulesets, for user space backward compatibility
+			 * (i.e. future-proof), and to properly handle merged
 			 * rulesets without overlapping access rights.  These
 			 * layers are set once and never changed for the
 			 * lifetime of the ruleset.
@@ -213,7 +232,8 @@ struct landlock_ruleset {
 };

 struct landlock_ruleset *
-landlock_create_ruleset(const access_mask_t access_mask);
+landlock_create_ruleset(const access_mask_t access_mask_fs,
+			const access_mask_t access_mask_net);

 void landlock_put_ruleset(struct landlock_ruleset *const ruleset);
 void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset);
@@ -249,6 +269,19 @@ landlock_add_fs_access_mask(struct landlock_ruleset *const ruleset,
 		(fs_mask << LANDLOCK_SHIFT_ACCESS_FS);
 }

+static inline void
+landlock_add_net_access_mask(struct landlock_ruleset *const ruleset,
+			     const access_mask_t net_access_mask,
+			     const u16 layer_level)
+{
+	access_mask_t net_mask = net_access_mask & LANDLOCK_MASK_ACCESS_NET;
+
+	/* Should already be checked in sys_landlock_create_ruleset(). */
+	WARN_ON_ONCE(net_access_mask != net_mask);
+	ruleset->access_masks[layer_level] |=
+		(net_mask << LANDLOCK_SHIFT_ACCESS_NET);
+}
+
 static inline access_mask_t
 landlock_get_raw_fs_access_mask(const struct landlock_ruleset *const ruleset,
 				const u16 layer_level)
@@ -266,6 +299,16 @@ landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
 	return landlock_get_raw_fs_access_mask(ruleset, layer_level) |
 	       LANDLOCK_ACCESS_FS_INITIALLY_DENIED;
 }
+
+static inline access_mask_t
+landlock_get_net_access_mask(const struct landlock_ruleset *const ruleset,
+			     const u16 layer_level)
+{
+	return (ruleset->access_masks[layer_level] >>
+		LANDLOCK_SHIFT_ACCESS_NET) &
+	       LANDLOCK_MASK_ACCESS_NET;
+}
+
 bool landlock_unmask_layers(const struct landlock_rule *const rule,
 			    const access_mask_t access_request,
 			    layer_mask_t (*const layer_masks)[],
diff --git a/security/landlock/setup.c b/security/landlock/setup.c
index 3f196d2ce4f9..7e4a598177b8 100644
--- a/security/landlock/setup.c
+++ b/security/landlock/setup.c
@@ -14,6 +14,7 @@
 #include "fs.h"
 #include "ptrace.h"
 #include "setup.h"
+#include "net.h"

 bool landlock_initialized __lsm_ro_after_init = false;

@@ -29,6 +30,7 @@ static int __init landlock_init(void)
 	landlock_add_cred_hooks();
 	landlock_add_ptrace_hooks();
 	landlock_add_fs_hooks();
+	landlock_add_net_hooks();
 	landlock_initialized = true;
 	pr_info("Up and running.\n");
 	return 0;
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index 8a54e87dbb17..5cb0a1bc6ec0 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -29,6 +29,7 @@
 #include "cred.h"
 #include "fs.h"
 #include "limits.h"
+#include "net.h"
 #include "ruleset.h"
 #include "setup.h"

@@ -74,7 +75,8 @@ static void build_check_abi(void)
 {
 	struct landlock_ruleset_attr ruleset_attr;
 	struct landlock_path_beneath_attr path_beneath_attr;
-	size_t ruleset_size, path_beneath_size;
+	struct landlock_net_service_attr net_service_attr;
+	size_t ruleset_size, path_beneath_size, net_service_size;

 	/*
 	 * For each user space ABI structures, first checks that there is no
@@ -82,13 +84,19 @@ static void build_check_abi(void)
 	 * struct size.
 	 */
 	ruleset_size = sizeof(ruleset_attr.handled_access_fs);
+	ruleset_size += sizeof(ruleset_attr.handled_access_net);
 	BUILD_BUG_ON(sizeof(ruleset_attr) != ruleset_size);
-	BUILD_BUG_ON(sizeof(ruleset_attr) != 8);
+	BUILD_BUG_ON(sizeof(ruleset_attr) != 16);

 	path_beneath_size = sizeof(path_beneath_attr.allowed_access);
 	path_beneath_size += sizeof(path_beneath_attr.parent_fd);
 	BUILD_BUG_ON(sizeof(path_beneath_attr) != path_beneath_size);
 	BUILD_BUG_ON(sizeof(path_beneath_attr) != 12);
+
+	net_service_size = sizeof(net_service_attr.allowed_access);
+	net_service_size += sizeof(net_service_attr.port);
+	BUILD_BUG_ON(sizeof(net_service_attr) != net_service_size);
+	BUILD_BUG_ON(sizeof(net_service_attr) != 16);
 }

 /* Ruleset handling */
@@ -129,7 +137,7 @@ static const struct file_operations ruleset_fops = {
 	.write = fop_dummy_write,
 };

-#define LANDLOCK_ABI_VERSION 3
+#define LANDLOCK_ABI_VERSION 4

 /**
  * sys_landlock_create_ruleset - Create a new ruleset
@@ -188,8 +196,14 @@ SYSCALL_DEFINE3(landlock_create_ruleset,
 	    LANDLOCK_MASK_ACCESS_FS)
 		return -EINVAL;

+	/* Checks network content (and 32-bits cast). */
+	if ((ruleset_attr.handled_access_net | LANDLOCK_MASK_ACCESS_NET) !=
+	    LANDLOCK_MASK_ACCESS_NET)
+		return -EINVAL;
+
 	/* Checks arguments and transforms to kernel struct. */
-	ruleset = landlock_create_ruleset(ruleset_attr.handled_access_fs);
+	ruleset = landlock_create_ruleset(ruleset_attr.handled_access_fs,
+					  ruleset_attr.handled_access_net);
 	if (IS_ERR(ruleset))
 		return PTR_ERR(ruleset);

@@ -315,13 +329,54 @@ static int add_rule_path_beneath(struct landlock_ruleset *const ruleset,
 	return err;
 }

+static int add_rule_net_service(struct landlock_ruleset *ruleset,
+				const void __user *const rule_attr)
+{
+#if IS_ENABLED(CONFIG_INET)
+	struct landlock_net_service_attr net_service_attr;
+	int res;
+	access_mask_t mask;
+
+	/* Copies raw user space buffer, only one type for now. */
+	res = copy_from_user(&net_service_attr, rule_attr,
+			     sizeof(net_service_attr));
+	if (res)
+		return -EFAULT;
+
+	/*
+	 * Informs about useless rule: empty allowed_access (i.e. deny rules)
+	 * are ignored by network actions.
+	 */
+	if (!net_service_attr.allowed_access)
+		return -ENOMSG;
+
+	/*
+	 * Checks that allowed_access matches the @ruleset constraints
+	 * (ruleset->access_masks[0] is automatically upgraded to 64-bits).
+	 */
+	mask = landlock_get_net_access_mask(ruleset, 0);
+	if ((net_service_attr.allowed_access | mask) != mask)
+		return -EINVAL;
+
+	/* Denies inserting a rule with port 0 or higher than 65535. */
+	if ((net_service_attr.port == 0) || (net_service_attr.port > U16_MAX))
+		return -EINVAL;
+
+	/* Imports the new rule. */
+	return landlock_append_net_rule(ruleset, net_service_attr.port,
+					net_service_attr.allowed_access);
+#else /* IS_ENABLED(CONFIG_INET) */
+	return -EAFNOSUPPORT;
+#endif /* IS_ENABLED(CONFIG_INET) */
+}
+
 /**
  * sys_landlock_add_rule - Add a new rule to a ruleset
  *
  * @ruleset_fd: File descriptor tied to the ruleset that should be extended
  *		with the new rule.
- * @rule_type: Identify the structure type pointed to by @rule_attr (only
- *             %LANDLOCK_RULE_PATH_BENEATH for now).
+ * @rule_type: Identify the structure type pointed to by @rule_attr:
+ *             %LANDLOCK_RULE_PATH_BENEATH or %LANDLOCK_RULE_NET_SERVICE.
  * @rule_attr: Pointer to a rule (only of type &struct
  *             landlock_path_beneath_attr for now).
  * @flags: Must be 0.
@@ -332,6 +387,8 @@ static int add_rule_path_beneath(struct landlock_ruleset *const ruleset,
  * Possible returned errors are:
  *
  * - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time;
+ * - %EAFNOSUPPORT: @rule_type is LANDLOCK_RULE_NET_SERVICE but TCP/IP is not
+ *   supported by the running kernel;
  * - %EINVAL: @flags is not 0, or inconsistent access in the rule (i.e.
  *   &landlock_path_beneath_attr.allowed_access is not a subset of the
  *   ruleset handled accesses);
@@ -366,6 +423,9 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
 	case LANDLOCK_RULE_PATH_BENEATH:
 		err = add_rule_path_beneath(ruleset, rule_attr);
 		break;
+	case LANDLOCK_RULE_NET_SERVICE:
+		err = add_rule_net_service(ruleset, rule_attr);
+		break;
 	default:
 		err = -EINVAL;
 		break;
diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c
index 792c3f0a59b4..646f778dfb1e 100644
--- a/tools/testing/selftests/landlock/base_test.c
+++ b/tools/testing/selftests/landlock/base_test.c
@@ -75,7 +75,7 @@ TEST(abi_version)
 	const struct landlock_ruleset_attr ruleset_attr = {
 		.handled_access_fs = LANDLOCK_ACCESS_FS_READ_FILE,
 	};
-	ASSERT_EQ(3, landlock_create_ruleset(NULL, 0,
+	ASSERT_EQ(4, landlock_create_ruleset(NULL, 0,
 					     LANDLOCK_CREATE_RULESET_VERSION));

 	ASSERT_EQ(-1, landlock_create_ruleset(&ruleset_attr, 0,
--
2.25.1