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1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * Landlock - Credential hooks
4 *
5 * Copyright © 2019-2020 Mickaël Salaün <[email protected]>
6 * Copyright © 2019-2020 ANSSI
7 * Copyright © 2021-2025 Microsoft Corporation
8 */
9
10#ifndef _SECURITY_LANDLOCK_CRED_H
11#define _SECURITY_LANDLOCK_CRED_H
12
13#include <linux/container_of.h>
14#include <linux/cred.h>
15#include <linux/init.h>
16#include <linux/rcupdate.h>
17
18#include "access.h"
19#include "domain.h"
20#include "limits.h"
21#include "ruleset.h"
22#include "setup.h"
23
24/**
25 * struct landlock_cred_security - Credential security blob
26 *
27 * This structure is packed to minimize the size of struct
28 * landlock_file_security. However, it is always aligned in the LSM cred blob,
29 * see lsm_set_blob_size().
30 *
31 * When updating this, also update landlock_cred_copy() if needed.
32 */
33struct landlock_cred_security {
34 /**
35 * @domain: Immutable domain enforced on a task.
36 */
37 struct landlock_domain *domain;
38
39#ifdef CONFIG_SECURITY_LANDLOCK_LOG
40 /**
41 * @domain_exec: Bitmask identifying the domain layers that were enforced by
42 * the current task's executed file (i.e. no new execve(2) since
43 * landlock_restrict_self(2)).
44 */
45 u16 domain_exec;
46 /**
47 * @log_subdomains_off: Set if the domain descendants's log_status should be
48 * set to %LANDLOCK_LOG_DISABLED. This is not a landlock_hierarchy
49 * configuration because it applies to future descendant domains and it does
50 * not require a current domain.
51 */
52 u8 log_subdomains_off : 1;
53#endif /* CONFIG_SECURITY_LANDLOCK_LOG */
54} __packed;
55
56#ifdef CONFIG_SECURITY_LANDLOCK_LOG
57
58/* Makes sure all layer executions can be stored. */
59static_assert(BITS_PER_TYPE(typeof_member(struct landlock_cred_security,
60 domain_exec)) >=
61 LANDLOCK_MAX_NUM_LAYERS);
62
63#endif /* CONFIG_SECURITY_LANDLOCK_LOG */
64
65static inline struct landlock_cred_security *
66landlock_cred(const struct cred *cred)
67{
68 return cred->security + landlock_blob_sizes.lbs_cred;
69}
70
71static inline void landlock_cred_copy(struct landlock_cred_security *dst,
72 const struct landlock_cred_security *src)
73{
74 landlock_put_domain(dst->domain);
75
76 *dst = *src;
77
78 landlock_get_domain(src->domain);
79}
80
81static inline struct landlock_domain *landlock_get_current_domain(void)
82{
83 return landlock_cred(current_cred())->domain;
84}
85
86/* The call needs to come from an RCU read-side critical section. */
87static inline const struct landlock_domain *
88landlock_get_task_domain(const struct task_struct *const task)
89{
90 return landlock_cred(__task_cred(task))->domain;
91}
92
93static inline bool landlocked(const struct task_struct *const task)
94{
95 bool has_dom;
96
97 if (task == current)
98 return !!landlock_get_current_domain();
99
100 rcu_read_lock();
101 has_dom = !!landlock_get_task_domain(task);
102 rcu_read_unlock();
103 return has_dom;
104}
105
106/**
107 * landlock_get_applicable_subject - Return the subject's Landlock credential
108 * if its enforced domain applies to (i.e.
109 * handles) at least one of the access rights
110 * specified in @masks
111 *
112 * @cred: credential
113 * @masks: access masks
114 * @handle_layer: returned youngest layer handling a subset of @masks. Not set
115 * if the function returns NULL.
116 *
117 * Return: landlock_cred(@cred) if any access rights specified in @masks is
118 * handled, or NULL otherwise.
119 */
120static inline const struct landlock_cred_security *
121landlock_get_applicable_subject(const struct cred *const cred,
122 const struct access_masks masks,
123 size_t *const handle_layer)
124{
125 const union access_masks_all masks_all = {
126 .masks = masks,
127 };
128 const struct landlock_domain *domain;
129 ssize_t layer_level;
130
131 if (!cred)
132 return NULL;
133
134 domain = landlock_cred(cred)->domain;
135 if (!domain)
136 return NULL;
137
138 for (layer_level = domain->num_layers - 1; layer_level >= 0;
139 layer_level--) {
140 union access_masks_all layer = {
141 .masks = domain->handled_masks[layer_level],
142 };
143
144 if (layer.all & masks_all.all) {
145 if (handle_layer)
146 *handle_layer = layer_level;
147
148 return landlock_cred(cred);
149 }
150 }
151
152 return NULL;
153}
154
155__init void landlock_add_cred_hooks(void);
156
157#endif /* _SECURITY_LANDLOCK_CRED_H */