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Diffstat (limited to 'security/landlock/ruleset.h')
| -rw-r--r-- | security/landlock/ruleset.h | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h new file mode 100644 index 0000000000..55b1df8f66 --- /dev/null +++ b/security/landlock/ruleset.h @@ -0,0 +1,180 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Landlock LSM - Ruleset management + * + * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net> + * Copyright © 2018-2020 ANSSI + */ + +#ifndef _SECURITY_LANDLOCK_RULESET_H +#define _SECURITY_LANDLOCK_RULESET_H + +#include <linux/bitops.h> +#include <linux/build_bug.h> +#include <linux/mutex.h> +#include <linux/rbtree.h> +#include <linux/refcount.h> +#include <linux/workqueue.h> + +#include "limits.h" +#include "object.h" + +typedef u16 access_mask_t; +/* Makes sure all filesystem access rights can be stored. */ +static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS); +/* Makes sure for_each_set_bit() and for_each_clear_bit() calls are OK. */ +static_assert(sizeof(unsigned long) >= sizeof(access_mask_t)); + +typedef u16 layer_mask_t; +/* Makes sure all layers can be checked. */ +static_assert(BITS_PER_TYPE(layer_mask_t) >= LANDLOCK_MAX_NUM_LAYERS); + +/** + * struct landlock_layer - Access rights for a given layer + */ +struct landlock_layer { + /** + * @level: Position of this layer in the layer stack. + */ + u16 level; + /** + * @access: Bitfield of allowed actions on the kernel object. They are + * relative to the object type (e.g. %LANDLOCK_ACTION_FS_READ). + */ + access_mask_t access; +}; + +/** + * struct landlock_rule - Access rights tied to an object + */ +struct landlock_rule { + /** + * @node: Node in the ruleset's red-black tree. + */ + struct rb_node node; + /** + * @object: Pointer to identify a kernel object (e.g. an inode). This + * is used as a key for this ruleset element. This pointer is set once + * and never modified. It always points to an allocated object because + * each rule increments the refcount of its object. + */ + struct landlock_object *object; + /** + * @num_layers: Number of entries in @layers. + */ + u32 num_layers; + /** + * @layers: Stack of layers, from the latest to the newest, implemented + * as a flexible array member (FAM). + */ + struct landlock_layer layers[] __counted_by(num_layers); +}; + +/** + * struct landlock_hierarchy - Node in a ruleset hierarchy + */ +struct landlock_hierarchy { + /** + * @parent: Pointer to the parent node, or NULL if it is a root + * Landlock domain. + */ + struct landlock_hierarchy *parent; + /** + * @usage: Number of potential children domains plus their parent + * domain. + */ + refcount_t usage; +}; + +/** + * struct landlock_ruleset - Landlock ruleset + * + * This data structure must contain unique entries, be updatable, and quick to + * match an object. + */ +struct landlock_ruleset { + /** + * @root: Root of a red-black tree containing &struct landlock_rule + * nodes. Once a ruleset is tied to a process (i.e. as a domain), this + * tree is immutable until @usage reaches zero. + */ + struct rb_root root; + /** + * @hierarchy: Enables hierarchy identification even when a parent + * domain vanishes. This is needed for the ptrace protection. + */ + struct landlock_hierarchy *hierarchy; + union { + /** + * @work_free: Enables to free a ruleset within a lockless + * section. This is only used by + * landlock_put_ruleset_deferred() when @usage reaches zero. + * The fields @lock, @usage, @num_rules, @num_layers and + * @fs_access_masks are then unused. + */ + struct work_struct work_free; + struct { + /** + * @lock: Protects against concurrent modifications of + * @root, if @usage is greater than zero. + */ + struct mutex lock; + /** + * @usage: Number of processes (i.e. domains) or file + * descriptors referencing this ruleset. + */ + refcount_t usage; + /** + * @num_rules: Number of non-overlapping (i.e. not for + * the same object) rules in this ruleset. + */ + u32 num_rules; + /** + * @num_layers: Number of layers that are used in this + * ruleset. This enables to check that all the layers + * allow an access request. A value of 0 identifies a + * non-merged ruleset (i.e. not a domain). + */ + u32 num_layers; + /** + * @fs_access_masks: Contains the subset of filesystem + * actions that are restricted by a ruleset. A domain + * saves all layers of merged rulesets in a stack + * (FAM), starting from the first layer to the last + * one. These layers are used when merging rulesets, + * for user space backward compatibility (i.e. + * future-proof), and to properly handle merged + * rulesets without overlapping access rights. These + * layers are set once and never changed for the + * lifetime of the ruleset. + */ + access_mask_t fs_access_masks[]; + }; + }; +}; + +struct landlock_ruleset * +landlock_create_ruleset(const access_mask_t fs_access_mask); + +void landlock_put_ruleset(struct landlock_ruleset *const ruleset); +void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset); + +int landlock_insert_rule(struct landlock_ruleset *const ruleset, + struct landlock_object *const object, + const access_mask_t access); + +struct landlock_ruleset * +landlock_merge_ruleset(struct landlock_ruleset *const parent, + struct landlock_ruleset *const ruleset); + +const struct landlock_rule * +landlock_find_rule(const struct landlock_ruleset *const ruleset, + const struct landlock_object *const object); + +static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset) +{ + if (ruleset) + refcount_inc(&ruleset->usage); +} + +#endif /* _SECURITY_LANDLOCK_RULESET_H */ |