Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_acl_posix1e.c
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1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright (c) 1999-2006 Robert N. M. Watson 5 * All rights reserved. 6 * 7 * This software was developed by Robert Watson for the TrustedBSD Project. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 */ 30 /* 31 * Developed by the TrustedBSD Project. 32 * 33 * ACL support routines specific to POSIX.1e access control lists. These are 34 * utility routines for code common across file systems implementing POSIX.1e 35 * ACLs. 36 */ 37 38 #include <sys/cdefs.h> 39 #if 0 40 __FBSDID("$FreeBSD: head/sys/kern/subr_acl_posix1e.c 341827 2018-12-11 19:32:16Z mjg $"); 41 #endif 42 __KERNEL_RCSID(0, "$NetBSD: subr_acl_posix1e.c,v 1.1 2020/05/16 18:31:50 christos Exp $"); 43 44 #include <sys/param.h> 45 #include <sys/kernel.h> 46 #include <sys/module.h> 47 #include <sys/systm.h> 48 #include <sys/mount.h> 49 #include <sys/vnode.h> 50 #include <sys/kauth.h> 51 #include <sys/errno.h> 52 #include <sys/stat.h> 53 #include <sys/acl.h> 54 55 /* 56 * For the purposes of filesystems maintaining the _OBJ entries in an inode 57 * with a mode_t field, this routine converts a mode_t entry to an 58 * acl_perm_t. 59 */ 60 acl_perm_t 61 acl_posix1e_mode_to_perm(acl_tag_t tag, mode_t mode) 62 { 63 acl_perm_t perm = 0; 64 65 switch(tag) { 66 case ACL_USER_OBJ: 67 if (mode & S_IXUSR) 68 perm |= ACL_EXECUTE; 69 if (mode & S_IRUSR) 70 perm |= ACL_READ; 71 if (mode & S_IWUSR) 72 perm |= ACL_WRITE; 73 return (perm); 74 75 case ACL_GROUP_OBJ: 76 if (mode & S_IXGRP) 77 perm |= ACL_EXECUTE; 78 if (mode & S_IRGRP) 79 perm |= ACL_READ; 80 if (mode & S_IWGRP) 81 perm |= ACL_WRITE; 82 return (perm); 83 84 case ACL_OTHER: 85 if (mode & S_IXOTH) 86 perm |= ACL_EXECUTE; 87 if (mode & S_IROTH) 88 perm |= ACL_READ; 89 if (mode & S_IWOTH) 90 perm |= ACL_WRITE; 91 return (perm); 92 93 default: 94 printf("%s: invalid tag (%u)\n", __func__, tag); 95 return (0); 96 } 97 } 98 99 /* 100 * Given inode information (uid, gid, mode), return an acl entry of the 101 * appropriate type. 102 */ 103 struct acl_entry 104 acl_posix1e_mode_to_entry(acl_tag_t tag, uid_t uid, gid_t gid, mode_t mode) 105 { 106 struct acl_entry acl_entry; 107 108 acl_entry.ae_tag = tag; 109 acl_entry.ae_perm = acl_posix1e_mode_to_perm(tag, mode); 110 acl_entry.ae_entry_type = 0; 111 acl_entry.ae_flags = 0; 112 switch(tag) { 113 case ACL_USER_OBJ: 114 acl_entry.ae_id = uid; 115 break; 116 117 case ACL_GROUP_OBJ: 118 acl_entry.ae_id = gid; 119 break; 120 121 case ACL_OTHER: 122 acl_entry.ae_id = ACL_UNDEFINED_ID; 123 break; 124 125 default: 126 acl_entry.ae_id = ACL_UNDEFINED_ID; 127 printf("acl_posix1e_mode_to_entry: invalid tag (%d)\n", tag); 128 } 129 130 return (acl_entry); 131 } 132 133 /* 134 * Utility function to generate a file mode given appropriate ACL entries. 135 */ 136 mode_t 137 acl_posix1e_perms_to_mode(struct acl_entry *acl_user_obj_entry, 138 struct acl_entry *acl_group_obj_entry, struct acl_entry *acl_other_entry) 139 { 140 mode_t mode; 141 142 mode = 0; 143 if (acl_user_obj_entry->ae_perm & ACL_EXECUTE) 144 mode |= S_IXUSR; 145 if (acl_user_obj_entry->ae_perm & ACL_READ) 146 mode |= S_IRUSR; 147 if (acl_user_obj_entry->ae_perm & ACL_WRITE) 148 mode |= S_IWUSR; 149 if (acl_group_obj_entry->ae_perm & ACL_EXECUTE) 150 mode |= S_IXGRP; 151 if (acl_group_obj_entry->ae_perm & ACL_READ) 152 mode |= S_IRGRP; 153 if (acl_group_obj_entry->ae_perm & ACL_WRITE) 154 mode |= S_IWGRP; 155 if (acl_other_entry->ae_perm & ACL_EXECUTE) 156 mode |= S_IXOTH; 157 if (acl_other_entry->ae_perm & ACL_READ) 158 mode |= S_IROTH; 159 if (acl_other_entry->ae_perm & ACL_WRITE) 160 mode |= S_IWOTH; 161 162 return (mode); 163 } 164 165 /* 166 * Utility function to generate a file mode given a complete POSIX.1e access 167 * ACL. Note that if the ACL is improperly formed, this may result in a 168 * panic. 169 */ 170 mode_t 171 acl_posix1e_acl_to_mode(struct acl *acl) 172 { 173 struct acl_entry *acl_mask, *acl_user_obj, *acl_group_obj, *acl_other; 174 int i; 175 176 /* 177 * Find the ACL entries relevant to a POSIX permission mode. 178 */ 179 acl_user_obj = acl_group_obj = acl_other = acl_mask = NULL; 180 for (i = 0; i < acl->acl_cnt; i++) { 181 switch (acl->acl_entry[i].ae_tag) { 182 case ACL_USER_OBJ: 183 acl_user_obj = &acl->acl_entry[i]; 184 break; 185 186 case ACL_GROUP_OBJ: 187 acl_group_obj = &acl->acl_entry[i]; 188 break; 189 190 case ACL_OTHER: 191 acl_other = &acl->acl_entry[i]; 192 break; 193 194 case ACL_MASK: 195 acl_mask = &acl->acl_entry[i]; 196 break; 197 198 case ACL_USER: 199 case ACL_GROUP: 200 break; 201 202 default: 203 panic("acl_posix1e_acl_to_mode: bad ae_tag"); 204 } 205 } 206 207 if (acl_user_obj == NULL || acl_group_obj == NULL || acl_other == NULL) 208 panic("acl_posix1e_acl_to_mode: missing base ae_tags"); 209 210 /* 211 * POSIX.1e specifies that if there is an ACL_MASK entry, we replace 212 * the mode "group" bits with its permissions. If there isn't, we 213 * use the ACL_GROUP_OBJ permissions. 214 */ 215 if (acl_mask != NULL) 216 return (acl_posix1e_perms_to_mode(acl_user_obj, acl_mask, 217 acl_other)); 218 else 219 return (acl_posix1e_perms_to_mode(acl_user_obj, acl_group_obj, 220 acl_other)); 221 } 222 223 /* 224 * Perform a syntactic check of the ACL, sufficient to allow an implementing 225 * filesystem to determine if it should accept this and rely on the POSIX.1e 226 * ACL properties. 227 */ 228 int 229 acl_posix1e_check(struct acl *acl) 230 { 231 int num_acl_user_obj, num_acl_user, num_acl_group_obj, num_acl_group; 232 int num_acl_mask, num_acl_other, i; 233 234 /* 235 * Verify that the number of entries does not exceed the maximum 236 * defined for acl_t. 237 * 238 * Verify that the correct number of various sorts of ae_tags are 239 * present: 240 * Exactly one ACL_USER_OBJ 241 * Exactly one ACL_GROUP_OBJ 242 * Exactly one ACL_OTHER 243 * If any ACL_USER or ACL_GROUP entries appear, then exactly one 244 * ACL_MASK entry must also appear. 245 * 246 * Verify that all ae_perm entries are in ACL_PERM_BITS. 247 * 248 * Verify all ae_tag entries are understood by this implementation. 249 * 250 * Note: Does not check for uniqueness of qualifier (ae_id) field. 251 */ 252 num_acl_user_obj = num_acl_user = num_acl_group_obj = num_acl_group = 253 num_acl_mask = num_acl_other = 0; 254 if (acl->acl_cnt > ACL_MAX_ENTRIES) 255 return (EINVAL); 256 for (i = 0; i < acl->acl_cnt; i++) { 257 struct acl_entry *ae = &acl->acl_entry[i]; 258 /* 259 * Check for a valid tag. 260 */ 261 switch(ae->ae_tag) { 262 case ACL_USER_OBJ: 263 ae->ae_id = ACL_UNDEFINED_ID; /* XXX */ 264 if (ae->ae_id != ACL_UNDEFINED_ID) 265 return (EINVAL); 266 num_acl_user_obj++; 267 break; 268 case ACL_GROUP_OBJ: 269 ae->ae_id = ACL_UNDEFINED_ID; /* XXX */ 270 if (ae->ae_id != ACL_UNDEFINED_ID) 271 return (EINVAL); 272 num_acl_group_obj++; 273 break; 274 case ACL_USER: 275 if (ae->ae_id == ACL_UNDEFINED_ID) 276 return (EINVAL); 277 num_acl_user++; 278 break; 279 case ACL_GROUP: 280 if (ae->ae_id == ACL_UNDEFINED_ID) 281 return (EINVAL); 282 num_acl_group++; 283 break; 284 case ACL_OTHER: 285 ae->ae_id = ACL_UNDEFINED_ID; /* XXX */ 286 if (ae->ae_id != ACL_UNDEFINED_ID) 287 return (EINVAL); 288 num_acl_other++; 289 break; 290 case ACL_MASK: 291 ae->ae_id = ACL_UNDEFINED_ID; /* XXX */ 292 if (ae->ae_id != ACL_UNDEFINED_ID) 293 return (EINVAL); 294 num_acl_mask++; 295 break; 296 default: 297 return (EINVAL); 298 } 299 /* 300 * Check for valid perm entries. 301 */ 302 if ((acl->acl_entry[i].ae_perm | ACL_PERM_BITS) != 303 ACL_PERM_BITS) 304 return (EINVAL); 305 } 306 if ((num_acl_user_obj != 1) || (num_acl_group_obj != 1) || 307 (num_acl_other != 1) || (num_acl_mask != 0 && num_acl_mask != 1)) 308 return (EINVAL); 309 if (((num_acl_group != 0) || (num_acl_user != 0)) && 310 (num_acl_mask != 1)) 311 return (EINVAL); 312 return (0); 313 } 314 315 /* 316 * Given a requested mode for a new object, and a default ACL, combine the 317 * two to produce a new mode. Be careful not to clear any bits that aren't 318 * intended to be affected by the POSIX.1e ACL. Eventually, this might also 319 * take the cmask as an argument, if we push that down into 320 * per-filesystem-code. 321 */ 322 mode_t 323 acl_posix1e_newfilemode(mode_t cmode, struct acl *dacl) 324 { 325 mode_t mode; 326 327 mode = cmode; 328 /* 329 * The current composition policy is that a permission bit must be 330 * set in *both* the ACL and the requested creation mode for it to 331 * appear in the resulting mode/ACL. First clear any possibly 332 * effected bits, then reconstruct. 333 */ 334 mode &= ACL_PRESERVE_MASK; 335 mode |= (ACL_OVERRIDE_MASK & cmode & acl_posix1e_acl_to_mode(dacl)); 336 337 return (mode); 338 }
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