[RFC PATCH v1 02/10] landlock: Add hook on socket_create()

[Ivanov Mikhail]

Add hook on socket_create() method. Since it'll be better to have control
over possible socket changes after family-related create() call, hook is
called on socket_post_create(). Handler only checks if the socket type
and family are allowed by domain.

Signed-off-by: Ivanov Mikhail <ivanov.mikhail1 at huawei-partners.com>
Reviewed-by: Konstantin Meskhidze <konstantin.meskhidze at huawei.com>
---
 security/landlock/setup.c  |  2 ++
 security/landlock/socket.c | 72 ++++++++++++++++++++++++++++++++++++++
 security/landlock/socket.h |  2 ++
 3 files changed, 76 insertions(+)

diff --git a/security/landlock/setup.c b/security/landlock/setup.c
index 28519a45b..fd4e7e8f3 100644
--- a/security/landlock/setup.c
+++ b/security/landlock/setup.c
@@ -14,6 +14,7 @@
 #include "cred.h"
 #include "fs.h"
 #include "net.h"
+#include "socket.h"
 #include "setup.h"
 #include "task.h"
 
@@ -37,6 +38,7 @@ static int __init landlock_init(void)
 	landlock_add_task_hooks();
 	landlock_add_fs_hooks();
 	landlock_add_net_hooks();
+	landlock_add_socket_hooks();
 	landlock_initialized = true;
 	pr_info("Up and running.\n");
 	return 0;
diff --git a/security/landlock/socket.c b/security/landlock/socket.c
index 88b4ef3a1..cba584543 100644
--- a/security/landlock/socket.c
+++ b/security/landlock/socket.c
@@ -5,6 +5,10 @@
  * Copyright © 2024 Huawei Tech. Co., Ltd.
  */
 
+#include <linux/net.h>
+#include <net/sock.h>
+
+#include "cred.h"
 #include "limits.h"
 #include "ruleset.h"
 #include "socket.h"
@@ -41,3 +45,71 @@ int landlock_append_socket_rule(struct landlock_ruleset *const ruleset,
 
 	return err;
 }
+
+static access_mask_t
+get_raw_handled_socket_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_socket_access_mask(domain, layer_level);
+	return access_dom;
+}
+
+static const struct landlock_ruleset *get_current_socket_domain(void)
+{
+	const struct landlock_ruleset *const dom =
+		landlock_get_current_domain();
+
+	if (!dom || !get_raw_handled_socket_accesses(dom))
+		return NULL;
+
+	return dom;
+}
+
+static int current_check_access_socket(struct socket *const sock,
+				       const access_mask_t access_request)
+{
+	union socket_key socket_key;
+	layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_SOCKET] = {};
+	const struct landlock_rule *rule;
+	access_mask_t handled_access;
+	struct landlock_id id = {
+		.type = LANDLOCK_KEY_SOCKET,
+	};
+	const struct landlock_ruleset *const dom = get_current_socket_domain();
+
+	if (!dom)
+		return 0;
+	if (WARN_ON_ONCE(dom->num_layers < 1))
+		return -EACCES;
+
+	socket_key.content.type = sock->type;
+	socket_key.content.domain = sock->sk->__sk_common.skc_family;
+	id.key.data = socket_key.val;
+
+	rule = landlock_find_rule(dom, id);
+	handled_access = landlock_init_layer_masks(
+		dom, access_request, &layer_masks, LANDLOCK_KEY_SOCKET);
+	if (landlock_unmask_layers(rule, handled_access, &layer_masks,
+				   ARRAY_SIZE(layer_masks)))
+		return 0;
+	return -EACCES;
+}
+
+static int hook_socket_create(struct socket *const sock,
+			    int family, int type, int protocol, int kern)
+{
+	return current_check_access_socket(sock, LANDLOCK_ACCESS_SOCKET_CREATE);
+}
+
+static struct security_hook_list landlock_hooks[] __ro_after_init = {
+	LSM_HOOK_INIT(socket_post_create, hook_socket_create),
+};
+
+__init void landlock_add_socket_hooks(void)
+{
+	security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
+			   &landlock_lsmid);
+}
diff --git a/security/landlock/socket.h b/security/landlock/socket.h
index 2b8f9ae7d..152f4d427 100644
--- a/security/landlock/socket.h
+++ b/security/landlock/socket.h
@@ -10,6 +10,8 @@
 
 #include "ruleset.h"
 
+__init void landlock_add_socket_hooks(void);
+
 int landlock_append_socket_rule(struct landlock_ruleset *const ruleset,
 				 const int domain, const int type,
 				 access_mask_t access_rights);
-- 
2.34.1