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