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20fd295494
Add audit support to the file_truncate and file_ioctl hooks. Add a deny_masks_t type and related helpers to store the domain's layer level per optional access rights (i.e. LANDLOCK_ACCESS_FS_TRUNCATE and LANDLOCK_ACCESS_FS_IOCTL_DEV) when opening a file, which cannot be inferred later. In practice, the landlock_file_security aligned blob size is still 16 bytes because this new one-byte deny_masks field follows the existing two-bytes allowed_access field and precede the packed fown_subject. Implementing deny_masks_t with a bitfield instead of a struct enables a generic implementation to store and extract layer levels. Add KUnit tests to check the identification of a layer level from a deny_masks_t, and the computation of a deny_masks_t from an access right with its layer level or a layer_mask_t array. Audit event sample: type=LANDLOCK_DENY msg=audit(1729738800.349:44): domain=195ba459b blockers=fs.ioctl_dev path="/dev/tty" dev="devtmpfs" ino=9 ioctlcmd=0x5401 Cc: Günther Noack <gnoack@google.com> Link: https://lore.kernel.org/r/20250320190717.2287696-15-mic@digikod.net Signed-off-by: Mickaël Salaün <mic@digikod.net>
101 lines
3.0 KiB
C
101 lines
3.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Landlock - Access types and helpers
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*
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* Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
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* Copyright © 2018-2020 ANSSI
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* Copyright © 2024-2025 Microsoft Corporation
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*/
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#ifndef _SECURITY_LANDLOCK_ACCESS_H
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#define _SECURITY_LANDLOCK_ACCESS_H
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#include <linux/bitops.h>
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#include <linux/build_bug.h>
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#include <linux/kernel.h>
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#include <uapi/linux/landlock.h>
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#include "limits.h"
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/*
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* All access rights that are denied by default whether they are handled or not
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* by a ruleset/layer. This must be ORed with all ruleset->access_masks[]
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* entries when we need to get the absolute handled access masks, see
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* landlock_upgrade_handled_access_masks().
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*/
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/* clang-format off */
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#define _LANDLOCK_ACCESS_FS_INITIALLY_DENIED ( \
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LANDLOCK_ACCESS_FS_REFER)
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/* clang-format on */
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/* clang-format off */
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#define _LANDLOCK_ACCESS_FS_OPTIONAL ( \
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LANDLOCK_ACCESS_FS_TRUNCATE | \
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LANDLOCK_ACCESS_FS_IOCTL_DEV)
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/* clang-format on */
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typedef u16 access_mask_t;
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/* Makes sure all filesystem access rights can be stored. */
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static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS);
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/* Makes sure all network access rights can be stored. */
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static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_NET);
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/* Makes sure all scoped rights can be stored. */
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static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_SCOPE);
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/* Makes sure for_each_set_bit() and for_each_clear_bit() calls are OK. */
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static_assert(sizeof(unsigned long) >= sizeof(access_mask_t));
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/* Ruleset access masks. */
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struct access_masks {
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access_mask_t fs : LANDLOCK_NUM_ACCESS_FS;
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access_mask_t net : LANDLOCK_NUM_ACCESS_NET;
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access_mask_t scope : LANDLOCK_NUM_SCOPE;
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};
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union access_masks_all {
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struct access_masks masks;
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u32 all;
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};
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/* Makes sure all fields are covered. */
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static_assert(sizeof(typeof_member(union access_masks_all, masks)) ==
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sizeof(typeof_member(union access_masks_all, all)));
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typedef u16 layer_mask_t;
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/* Makes sure all layers can be checked. */
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static_assert(BITS_PER_TYPE(layer_mask_t) >= LANDLOCK_MAX_NUM_LAYERS);
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/*
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* Tracks domains responsible of a denied access. This is required to avoid
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* storing in each object the full layer_masks[] required by update_request().
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*/
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typedef u8 deny_masks_t;
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/*
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* Makes sure all optional access rights can be tied to a layer index (cf.
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* get_deny_mask).
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*/
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static_assert(BITS_PER_TYPE(deny_masks_t) >=
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(HWEIGHT(LANDLOCK_MAX_NUM_LAYERS - 1) *
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HWEIGHT(_LANDLOCK_ACCESS_FS_OPTIONAL)));
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/* LANDLOCK_MAX_NUM_LAYERS must be a power of two (cf. deny_masks_t assert). */
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static_assert(HWEIGHT(LANDLOCK_MAX_NUM_LAYERS) == 1);
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/* Upgrades with all initially denied by default access rights. */
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static inline struct access_masks
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landlock_upgrade_handled_access_masks(struct access_masks access_masks)
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{
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/*
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* All access rights that are denied by default whether they are
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* explicitly handled or not.
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*/
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if (access_masks.fs)
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access_masks.fs |= _LANDLOCK_ACCESS_FS_INITIALLY_DENIED;
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return access_masks;
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}
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#endif /* _SECURITY_LANDLOCK_ACCESS_H */
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