1 files changed, 146 insertions, 0 deletions
diff --git a/security/landlock/cred.h b/security/landlock/cred.h
new file mode 100644
index 000000000000..c82fe63ec598
--- /dev/null
+++ b/security/landlock/cred.h
@@ -0,0 +1,146 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Landlock - Credential hooks
+ *
+ * Copyright © 2019-2020 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2019-2020 ANSSI
+ * Copyright © 2021-2025 Microsoft Corporation
+ */
+
+#ifndef _SECURITY_LANDLOCK_CRED_H
+#define _SECURITY_LANDLOCK_CRED_H
+
+#include <linux/container_of.h>
+#include <linux/cred.h>
+#include <linux/init.h>
+#include <linux/rcupdate.h>
+
+#include "access.h"
+#include "limits.h"
+#include "ruleset.h"
+#include "setup.h"
+
+/**
+ * struct landlock_cred_security - Credential security blob
+ *
+ * This structure is packed to minimize the size of struct
+ * landlock_file_security.  However, it is always aligned in the LSM cred blob,
+ * see lsm_set_blob_size().
+ */
+struct landlock_cred_security {
+	/**
+	 * @domain: Immutable ruleset enforced on a task.
+	 */
+	struct landlock_ruleset *domain;
+
+#ifdef CONFIG_AUDIT
+	/**
+	 * @domain_exec: Bitmask identifying the domain layers that were enforced by
+	 * the current task's executed file (i.e. no new execve(2) since
+	 * landlock_restrict_self(2)).
+	 */
+	u16 domain_exec;
+	/**
+	 * @log_subdomains_off: Set if the domain descendants's log_status should be
+	 * set to %LANDLOCK_LOG_DISABLED.  This is not a landlock_hierarchy
+	 * configuration because it applies to future descendant domains and it does
+	 * not require a current domain.
+	 */
+	u8 log_subdomains_off : 1;
+#endif /* CONFIG_AUDIT */
+} __packed;
+
+#ifdef CONFIG_AUDIT
+
+/* Makes sure all layer executions can be stored. */
+static_assert(BITS_PER_TYPE(typeof_member(struct landlock_cred_security,
+					  domain_exec)) >=
+	      LANDLOCK_MAX_NUM_LAYERS);
+
+#endif /* CONFIG_AUDIT */
+
+static inline struct landlock_cred_security *
+landlock_cred(const struct cred *cred)
+{
+	return cred->security + landlock_blob_sizes.lbs_cred;
+}
+
+static inline struct landlock_ruleset *landlock_get_current_domain(void)
+{
+	return landlock_cred(current_cred())->domain;
+}
+
+/*
+ * The call needs to come from an RCU read-side critical section.
+ */
+static inline const struct landlock_ruleset *
+landlock_get_task_domain(const struct task_struct *const task)
+{
+	return landlock_cred(__task_cred(task))->domain;
+}
+
+static inline bool landlocked(const struct task_struct *const task)
+{
+	bool has_dom;
+
+	if (task == current)
+		return !!landlock_get_current_domain();
+
+	rcu_read_lock();
+	has_dom = !!landlock_get_task_domain(task);
+	rcu_read_unlock();
+	return has_dom;
+}
+
+/**
+ * landlock_get_applicable_subject - Return the subject's Landlock credential
+ *                                   if its enforced domain applies to (i.e.
+ *                                   handles) at least one of the access rights
+ *                                   specified in @masks
+ *
+ * @cred: credential
+ * @masks: access masks
+ * @handle_layer: returned youngest layer handling a subset of @masks.  Not set
+ *                if the function returns NULL.
+ *
+ * Returns: landlock_cred(@cred) if any access rights specified in @masks is
+ * handled, or NULL otherwise.
+ */
+static inline const struct landlock_cred_security *
+landlock_get_applicable_subject(const struct cred *const cred,
+				const struct access_masks masks,
+				size_t *const handle_layer)
+{
+	const union access_masks_all masks_all = {
+		.masks = masks,
+	};
+	const struct landlock_ruleset *domain;
+	ssize_t layer_level;
+
+	if (!cred)
+		return NULL;
+
+	domain = landlock_cred(cred)->domain;
+	if (!domain)
+		return NULL;
+
+	for (layer_level = domain->num_layers - 1; layer_level >= 0;
+	     layer_level--) {
+		union access_masks_all layer = {
+			.masks = domain->access_masks[layer_level],
+		};
+
+		if (layer.all & masks_all.all) {
+			if (handle_layer)
+				*handle_layer = layer_level;
+
+			return landlock_cred(cred);
+		}
+	}
+
+	return NULL;
+}
+
+__init void landlock_add_cred_hooks(void);
+
+#endif /* _SECURITY_LANDLOCK_CRED_H */