/* 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().
 *
 * When updating this, also update landlock_cred_copy() if needed.
 */
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 void landlock_cred_copy(struct landlock_cred_security *dst,
                                      const struct landlock_cred_security *src)
{
        landlock_put_ruleset(dst->domain);

        *dst = *src;

        landlock_get_ruleset(src->domain);
}

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 */