[PATCH v4 17/30] landlock: Log scoped denials

["Mickaël Salaün" <mic@digikod.net>]

Add audit support for unix_stream_connect, unix_may_send, task_kill, and
file_send_sigiotask hooks.

The related blockers are:
- scope.abstract_unix_socket
- scope.signal

Audit event sample for abstract unix socket:

  type=LANDLOCK_DENY msg=audit(1729738800.268:30): domain=195ba459b blockers=scope.abstract_unix_socket path=00666F6F

Audit event sample for signal:

  type=LANDLOCK_DENY msg=audit(1729738800.291:31): domain=195ba459b blockers=scope.signal opid=1 ocomm="systemd"

Cc: Günther Noack <gnoack@google.com>
Cc: Tahera Fahimi <fahimitahera@gmail.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20250108154338.1129069-18-mic@digikod.net
---

Changes since v3:
- Cosmetic change to the "scope.*" blocker names.
- Extend commit message.

Changes since v1:
- New patch.
---
 security/landlock/audit.c |  8 ++++++
 security/landlock/audit.h |  2 ++
 security/landlock/task.c  | 58 ++++++++++++++++++++++++++++++++++++---
 3 files changed, 64 insertions(+), 4 deletions(-)

diff --git a/security/landlock/audit.c b/security/landlock/audit.c
index 2744e3d4fe73..7a2183ac9add 100644
--- a/security/landlock/audit.c
+++ b/security/landlock/audit.c
@@ -70,6 +70,14 @@ get_blocker(const enum landlock_request_type type,
 		if (WARN_ON_ONCE(access_bit >= ARRAY_SIZE(net_access_strings)))
 			return "unknown";
 		return net_access_strings[access_bit];
+
+	case LANDLOCK_REQUEST_SCOPE_ABSTRACT_UNIX_SOCKET:
+		WARN_ON_ONCE(access_bit != -1);
+		return "scope.abstract_unix_socket";
+
+	case LANDLOCK_REQUEST_SCOPE_SIGNAL:
+		WARN_ON_ONCE(access_bit != -1);
+		return "scope.signal";
 	}
 
 	WARN_ON_ONCE(1);
diff --git a/security/landlock/audit.h b/security/landlock/audit.h
index 9a3697b901b5..dd5deaf7dc4d 100644
--- a/security/landlock/audit.h
+++ b/security/landlock/audit.h
@@ -19,6 +19,8 @@ enum landlock_request_type {
 	LANDLOCK_REQUEST_FS_CHANGE_LAYOUT,
 	LANDLOCK_REQUEST_FS_ACCESS,
 	LANDLOCK_REQUEST_NET_ACCESS,
+	LANDLOCK_REQUEST_SCOPE_ABSTRACT_UNIX_SOCKET,
+	LANDLOCK_REQUEST_SCOPE_SIGNAL,
 };
 
 /*
diff --git a/security/landlock/task.c b/security/landlock/task.c
index 4fef963274fd..1b3d5de89e14 100644
--- a/security/landlock/task.c
+++ b/security/landlock/task.c
@@ -263,13 +263,27 @@ static int hook_unix_stream_connect(struct sock *const sock,
 	const struct landlock_ruleset *const dom =
 		landlock_get_applicable_domain(landlock_get_current_domain(),
 					       unix_scope);
+	struct lsm_network_audit audit_net = {
+		.sk = other,
+	};
+	struct landlock_request request = {
+		.type = LANDLOCK_REQUEST_SCOPE_ABSTRACT_UNIX_SOCKET,
+		.audit = {
+			.type = LSM_AUDIT_DATA_NET,
+			.u.net = &audit_net,
+		},
+	};
 
 	/* Quick return for non-landlocked tasks. */
 	if (!dom)
 		return 0;
 
-	if (is_abstract_socket(other) && sock_is_scoped(other, dom))
+	if (is_abstract_socket(other) && sock_is_scoped(other, dom)) {
+		request.layer_plus_one =
+			landlock_match_layer_level(dom, unix_scope) + 1;
+		landlock_log_denial(dom, &request);
 		return -EPERM;
+	}
 
 	return 0;
 }
@@ -280,6 +294,16 @@ static int hook_unix_may_send(struct socket *const sock,
 	const struct landlock_ruleset *const dom =
 		landlock_get_applicable_domain(landlock_get_current_domain(),
 					       unix_scope);
+	struct lsm_network_audit audit_net = {
+		.sk = other->sk,
+	};
+	struct landlock_request request = {
+		.type = LANDLOCK_REQUEST_SCOPE_ABSTRACT_UNIX_SOCKET,
+		.audit = {
+			.type = LSM_AUDIT_DATA_NET,
+			.u.net = &audit_net,
+		},
+	};
 
 	if (!dom)
 		return 0;
@@ -291,8 +315,12 @@ static int hook_unix_may_send(struct socket *const sock,
 	if (unix_peer(sock->sk) == other->sk)
 		return 0;
 
-	if (is_abstract_socket(other->sk) && sock_is_scoped(other->sk, dom))
+	if (is_abstract_socket(other->sk) && sock_is_scoped(other->sk, dom)) {
+		request.layer_plus_one =
+			landlock_match_layer_level(dom, unix_scope) + 1;
+		landlock_log_denial(dom, &request);
 		return -EPERM;
+	}
 
 	return 0;
 }
@@ -307,6 +335,13 @@ static int hook_task_kill(struct task_struct *const p,
 {
 	bool is_scoped;
 	const struct landlock_ruleset *dom;
+	struct landlock_request request = {
+		.type = LANDLOCK_REQUEST_SCOPE_SIGNAL,
+		.audit = {
+			.type = LSM_AUDIT_DATA_TASK,
+			.u.tsk = p,
+		},
+	};
 
 	if (cred) {
 		/* Dealing with USB IO. */
@@ -324,8 +359,12 @@ static int hook_task_kill(struct task_struct *const p,
 	is_scoped = domain_is_scoped(dom, landlock_get_task_domain(p),
 				     LANDLOCK_SCOPE_SIGNAL);
 	rcu_read_unlock();
-	if (is_scoped)
+	if (is_scoped) {
+		request.layer_plus_one =
+			landlock_match_layer_level(dom, signal_scope) + 1;
+		landlock_log_denial(dom, &request);
 		return -EPERM;
+	}
 
 	return 0;
 }
@@ -334,6 +373,13 @@ static int hook_file_send_sigiotask(struct task_struct *tsk,
 				    struct fown_struct *fown, int signum)
 {
 	const struct landlock_ruleset *dom;
+	struct landlock_request request = {
+		.type = LANDLOCK_REQUEST_SCOPE_SIGNAL,
+		.audit = {
+			.type = LSM_AUDIT_DATA_TASK,
+			.u.tsk = tsk,
+		},
+	};
 	bool is_scoped = false;
 
 	/* Lock already held by send_sigio() and send_sigurg(). */
@@ -349,8 +395,12 @@ static int hook_file_send_sigiotask(struct task_struct *tsk,
 	is_scoped = domain_is_scoped(dom, landlock_get_task_domain(tsk),
 				     LANDLOCK_SCOPE_SIGNAL);
 	rcu_read_unlock();
-	if (is_scoped)
+	if (is_scoped) {
+		request.layer_plus_one =
+			landlock_match_layer_level(dom, signal_scope) + 1;
+		landlock_log_denial(dom, &request);
 		return -EPERM;
+	}
 
 	return 0;
 }
-- 
2.47.1