1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 /* 3 * Landlock - Access types and helpers 4 * 5 * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net> 6 * Copyright © 2018-2020 ANSSI 7 * Copyright © 2024-2025 Microsoft Corporation 8 */ 9 10 #ifndef _SECURITY_LANDLOCK_ACCESS_H 11 #define _SECURITY_LANDLOCK_ACCESS_H 12 13 #include <linux/bitops.h> 14 #include <linux/build_bug.h> 15 #include <linux/kernel.h> 16 #include <uapi/linux/landlock.h> 17 18 #include "limits.h" 19 20 /* 21 * All access rights that are denied by default whether they are handled or not 22 * by a ruleset/layer. This must be ORed with the .handled field of all 23 * domain->layers[] entries when we need to get the absolute handled access 24 * masks, see landlock_upgrade_handled_layer_config(). 25 */ 26 /* clang-format off */ 27 #define _LANDLOCK_ACCESS_FS_INITIALLY_DENIED ( \ 28 LANDLOCK_ACCESS_FS_REFER) 29 /* clang-format on */ 30 31 /* clang-format off */ 32 #define _LANDLOCK_ACCESS_FS_OPTIONAL ( \ 33 LANDLOCK_ACCESS_FS_TRUNCATE | \ 34 LANDLOCK_ACCESS_FS_IOCTL_DEV) 35 /* clang-format on */ 36 37 typedef u32 access_mask_t; 38 39 /* Makes sure all filesystem access rights can be stored. */ 40 static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS); 41 /* Makes sure all network access rights can be stored. */ 42 static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_NET); 43 /* Makes sure all scoped rights can be stored. */ 44 static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_SCOPE); 45 /* Makes sure all permissions can be stored. */ 46 static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_PERMISSION); 47 /* Makes sure for_each_set_bit() and for_each_clear_bit() calls are OK. */ 48 static_assert(sizeof(unsigned long) >= sizeof(access_mask_t)); 49 50 /* Access and permission masks (bitfields only). */ 51 struct access_masks { 52 access_mask_t fs : LANDLOCK_NUM_ACCESS_FS; 53 access_mask_t net : LANDLOCK_NUM_ACCESS_NET; 54 access_mask_t scope : LANDLOCK_NUM_SCOPE; 55 access_mask_t permissions : LANDLOCK_NUM_PERMISSION; 56 } __packed __aligned(sizeof(u32)); 57 58 union access_masks_all { 59 struct access_masks masks; 60 u32 all; 61 }; 62 63 /* Makes sure all fields are covered. */ 64 static_assert(sizeof(typeof_member(union access_masks_all, masks)) == 65 sizeof(typeof_member(union access_masks_all, all))); 66 67 /** 68 * struct permission_masks - Per-permission member bitmasks 69 */ 70 struct permission_masks { 71 /** 72 * @ns_types: Namespace type member mask, indexed in FOR_EACH_NS_TYPE() 73 * order. 74 */ 75 u64 ns_types : LANDLOCK_NUM_NAMESPACE_TYPE; 76 /** 77 * @caps: Capability member mask, indexed by CAP_* values. 78 */ 79 u64 caps : LANDLOCK_NUM_CAPABILITY; 80 } __packed __aligned(sizeof(u64)); 81 82 static_assert(sizeof(struct permission_masks) == sizeof(u64)); 83 /* All permission_masks bitfields must fit in a single u64. */ 84 static_assert(LANDLOCK_NUM_CAPABILITY + LANDLOCK_NUM_NAMESPACE_TYPE <= 85 BITS_PER_TYPE(u64)); 86 87 /** 88 * struct layer_config - Per-layer access configuration 89 * 90 * A ruleset stores one mutable layer and a domain stores a flexible array of 91 * immutable layers. Unlike filesystem and network access rights, namespace 92 * types and capabilities use flat bitmasks because their keyspaces are small 93 * and bounded. 94 */ 95 struct layer_config { 96 /** 97 * @allowed: Members allowed by each handled permission. 98 */ 99 struct permission_masks allowed; 100 /** 101 * @handled: Bitmask of access rights and permissions handled (i.e. 102 * restricted) by this layer. 103 */ 104 struct access_masks handled; 105 }; 106 107 #define _LANDLOCK_LAYER_MASK_PADDING \ 108 (BITS_PER_TYPE(access_mask_t) - LANDLOCK_NUM_ACCESS_MAX - \ 109 IS_ENABLED(CONFIG_SECURITY_LANDLOCK_LOG)) 110 111 /** 112 * struct layer_mask - The access rights and rule flags for a layer. 113 * 114 * This has a bit for each access rights and rule flags. During access checks, 115 * it is used to represent the access rights for each layer which still need to 116 * be fulfilled. When all bits are 0, the access request is considered to be 117 * fulfilled. 118 */ 119 struct layer_mask { 120 /** 121 * @access: The unfulfilled access rights for this layer. 122 */ 123 access_mask_t access : LANDLOCK_NUM_ACCESS_MAX; 124 #ifdef CONFIG_SECURITY_LANDLOCK_LOG 125 /** 126 * @quiet: Whether we have encountered a rule with the quiet flag for 127 * this layer. Used to control logging. 128 */ 129 access_mask_t quiet : 1; 130 #endif /* CONFIG_SECURITY_LANDLOCK_LOG */ 131 /** 132 * @__pad: Padding for the compiler's bitfield initialization. 133 */ 134 access_mask_t __pad : _LANDLOCK_LAYER_MASK_PADDING; 135 } __packed __aligned(sizeof(access_mask_t)); 136 137 /* 138 * Make sure that we don't increase the size of struct layer_mask when storing 139 * rule flags. 140 */ 141 static_assert(sizeof(struct layer_mask) == sizeof(access_mask_t)); 142 143 /** 144 * struct layer_masks - An array of struct layer_mask, one per layer. 145 */ 146 struct layer_masks { 147 /** 148 * @layers: The unfulfilled access rights for each layer. 149 */ 150 struct layer_mask layers[LANDLOCK_MAX_NUM_LAYERS]; 151 }; 152 153 /* 154 * Tracks domains responsible of a denied access. This avoids storing in each 155 * object the full matrix of per-layer unfulfilled access rights, which is 156 * required by update_request(). 157 * 158 * Each nibble represents the layer index of the newest layer which denied a 159 * certain access right. For file system access rights, the upper four bits are 160 * the index of the layer which denies LANDLOCK_ACCESS_FS_IOCTL_DEV and the 161 * lower nibble represents LANDLOCK_ACCESS_FS_TRUNCATE. 162 */ 163 typedef u8 deny_masks_t; 164 165 /* 166 * Makes sure all optional access rights can be tied to a layer index (cf. 167 * get_deny_mask). 168 */ 169 static_assert(BITS_PER_TYPE(deny_masks_t) >= 170 (HWEIGHT(LANDLOCK_MAX_NUM_LAYERS - 1) * 171 HWEIGHT(_LANDLOCK_ACCESS_FS_OPTIONAL))); 172 173 /* LANDLOCK_MAX_NUM_LAYERS must be a power of two (cf. deny_masks_t assert). */ 174 static_assert(HWEIGHT(LANDLOCK_MAX_NUM_LAYERS) == 1); 175 176 /* Upgrades with all initially denied by default access rights. */ 177 static inline struct layer_config 178 landlock_upgrade_handled_layer_config(struct layer_config layer_config) 179 { 180 /* 181 * All access rights that are denied by default whether they are 182 * explicitly handled or not. 183 */ 184 if (layer_config.handled.fs) 185 layer_config.handled.fs |= _LANDLOCK_ACCESS_FS_INITIALLY_DENIED; 186 187 return layer_config; 188 } 189 190 /* Checks the subset relation between access masks. */ 191 static inline bool access_mask_subset(access_mask_t subset, 192 access_mask_t superset) 193 { 194 return (subset | superset) == superset; 195 } 196 197 /* A bitmask that is large enough to hold set of optional accesses. */ 198 typedef u8 optional_access_t; 199 static_assert(BITS_PER_TYPE(optional_access_t) >= 200 HWEIGHT(_LANDLOCK_ACCESS_FS_OPTIONAL)); 201 202 #endif /* _SECURITY_LANDLOCK_ACCESS_H */ 203