[RFC PATCH v2 13/14] landlock: Log scoped denials

[Mickaël Salaün]

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

Audit record sample:

  DENY:    domain=4533720578 blockers=scope_abstract_unix_socket path=00666F6F
  SYSCALL: arch=c000003e syscall=42 success=no exit=-1 ...

Cc: Günther Noack <gnoack at google.com>
Cc: Tahera Fahimi <fahimitahera at gmail.com>
Signed-off-by: Mickaël Salaün <mic at digikod.net>
Link: https://lore.kernel.org/r/20241022161009.982584-14-mic@digikod.net
---
 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 c31a4a8719ee..b551812b8bc9 100644
--- a/security/landlock/audit.c
+++ b/security/landlock/audit.c
@@ -69,6 +69,14 @@ 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 1075b0c8401f..1e0a9164bacc 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 8c4468fb86bf..ddcb993bd53a 100644
--- a/security/landlock/task.c
+++ b/security/landlock/task.c
@@ -262,13 +262,27 @@ static int hook_unix_stream_connect(struct sock *const sock,
 {
 	const struct landlock_ruleset *const dom = landlock_match_ruleset(
 		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;
 }
@@ -278,6 +292,16 @@ static int hook_unix_may_send(struct socket *const sock,
 {
 	const struct landlock_ruleset *const dom = landlock_match_ruleset(
 		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;
@@ -289,8 +313,12 @@ 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;
 }
@@ -305,6 +333,13 @@ 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. */
@@ -322,8 +357,12 @@ 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;
 }
@@ -332,6 +371,13 @@ 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(). */
@@ -347,8 +393,12 @@ 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;
 }
-- 
2.47.0