1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 /* 3 * Landlock - Credential hooks 4 * 5 * Copyright © 2019-2020 Mickaël Salaün <mic@digikod.net> 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 */ 33 struct 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. */ 59 static_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 65 static inline struct landlock_cred_security * 66 landlock_cred(const struct cred *cred) 67 { 68 return cred->security + landlock_blob_sizes.lbs_cred; 69 } 70 71 static 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 81 static 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. */ 87 static inline const struct landlock_domain * 88 landlock_get_task_domain(const struct task_struct *const task) 89 { 90 return landlock_cred(__task_cred(task))->domain; 91 } 92 93 static 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 */ 120 static inline const struct landlock_cred_security * 121 landlock_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 */ 158