src/shared/acl-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include <errno.h>
   4 #include <stdbool.h>
   5 #include <sys/stat.h>
   6 #include <sys/types.h>
   7
   8 #include "acl-util.h"
   9 #include "alloc-util.h"
  10 #include "string-util.h"
  11 #include "strv.h"
  12 #include "user-util.h"
  13 #include "util.h"
  14
  15 int acl_find_uid(acl_t acl, uid_t uid, acl_entry_t *ret_entry) {
  16         acl_entry_t i;
  17         int r;
  18
  19         assert(acl);
  20         assert(uid_is_valid(uid));
  21         assert(ret_entry);
  22
  23         for (r = acl_get_entry(acl, ACL_FIRST_ENTRY, &i);
  24              r > 0;
  25              r = acl_get_entry(acl, ACL_NEXT_ENTRY, &i)) {
  26
  27                 acl_tag_t tag;
  28                 uid_t *u;
  29                 bool b;
  30
  31                 if (acl_get_tag_type(i, &tag) < 0)
  32                         return -errno;
  33
  34                 if (tag != ACL_USER)
  35                         continue;
  36
  37                 u = acl_get_qualifier(i);
  38                 if (!u)
  39                         return -errno;
  40
  41                 b = *u == uid;
  42                 acl_free(u);
  43
  44                 if (b) {
  45                         *ret_entry = i;
  46                         return 1;
  47                 }
  48         }
  49         if (r < 0)
  50                 return -errno;
  51
  52         *ret_entry = NULL;
  53         return 0;
  54 }
  55
  56 int calc_acl_mask_if_needed(acl_t *acl_p) {
  57         acl_entry_t i;
  58         int r;
  59         bool need = false;
  60
  61         assert(acl_p);
  62
  63         for (r = acl_get_entry(*acl_p, ACL_FIRST_ENTRY, &i);
  64              r > 0;
  65              r = acl_get_entry(*acl_p, ACL_NEXT_ENTRY, &i)) {
  66                 acl_tag_t tag;
  67
  68                 if (acl_get_tag_type(i, &tag) < 0)
  69                         return -errno;
  70
  71                 if (tag == ACL_MASK)
  72                         return 0;
  73
  74                 if (IN_SET(tag, ACL_USER, ACL_GROUP))
  75                         need = true;
  76         }
  77         if (r < 0)
  78                 return -errno;
  79
  80         if (need && acl_calc_mask(acl_p) < 0)
  81                 return -errno;
  82
  83         return need;
  84 }
  85
  86 int add_base_acls_if_needed(acl_t *acl_p, const char *path) {
  87         acl_entry_t i;
  88         int r;
  89         bool have_user_obj = false, have_group_obj = false, have_other = false;
  90         struct stat st;
  91         _cleanup_(acl_freep) acl_t basic = NULL;
  92
  93         assert(acl_p);
  94
  95         for (r = acl_get_entry(*acl_p, ACL_FIRST_ENTRY, &i);
  96              r > 0;
  97              r = acl_get_entry(*acl_p, ACL_NEXT_ENTRY, &i)) {
  98                 acl_tag_t tag;
  99
 100                 if (acl_get_tag_type(i, &tag) < 0)
 101                         return -errno;
 102
 103                 if (tag == ACL_USER_OBJ)
 104                         have_user_obj = true;
 105                 else if (tag == ACL_GROUP_OBJ)
 106                         have_group_obj = true;
 107                 else if (tag == ACL_OTHER)
 108                         have_other = true;
 109                 if (have_user_obj && have_group_obj && have_other)
 110                         return 0;
 111         }
 112         if (r < 0)
 113                 return -errno;
 114
 115         r = stat(path, &st);
 116         if (r < 0)
 117                 return -errno;
 118
 119         basic = acl_from_mode(st.st_mode);
 120         if (!basic)
 121                 return -errno;
 122
 123         for (r = acl_get_entry(basic, ACL_FIRST_ENTRY, &i);
 124              r > 0;
 125              r = acl_get_entry(basic, ACL_NEXT_ENTRY, &i)) {
 126                 acl_tag_t tag;
 127                 acl_entry_t dst;
 128
 129                 if (acl_get_tag_type(i, &tag) < 0)
 130                         return -errno;
 131
 132                 if ((tag == ACL_USER_OBJ && have_user_obj) ||
 133                     (tag == ACL_GROUP_OBJ && have_group_obj) ||
 134                     (tag == ACL_OTHER && have_other))
 135                         continue;
 136
 137                 r = acl_create_entry(acl_p, &dst);
 138                 if (r < 0)
 139                         return -errno;
 140
 141                 r = acl_copy_entry(dst, i);
 142                 if (r < 0)
 143                         return -errno;
 144         }
 145         if (r < 0)
 146                 return -errno;
 147         return 0;
 148 }
 149
 150 int acl_search_groups(const char *path, char ***ret_groups) {
 151         _cleanup_strv_free_ char **g = NULL;
 152         _cleanup_(acl_freep) acl_t acl = NULL;
 153         bool ret = false;
 154         acl_entry_t entry;
 155         int r;
 156
 157         assert(path);
 158
 159         acl = acl_get_file(path, ACL_TYPE_DEFAULT);
 160         if (!acl)
 161                 return -errno;
 162
 163         r = acl_get_entry(acl, ACL_FIRST_ENTRY, &entry);
 164         for (;;) {
 165                 _cleanup_(acl_free_gid_tpp) gid_t *gid = NULL;
 166                 acl_tag_t tag;
 167
 168                 if (r < 0)
 169                         return -errno;
 170                 if (r == 0)
 171                         break;
 172
 173                 if (acl_get_tag_type(entry, &tag) < 0)
 174                         return -errno;
 175
 176                 if (tag != ACL_GROUP)
 177                         goto next;
 178
 179                 gid = acl_get_qualifier(entry);
 180                 if (!gid)
 181                         return -errno;
 182
 183                 if (in_gid(*gid) > 0) {
 184                         if (!ret_groups)
 185                                 return true;
 186
 187                         ret = true;
 188                 }
 189
 190                 if (ret_groups) {
 191                         char *name;
 192
 193                         name = gid_to_name(*gid);
 194                         if (!name)
 195                                 return -ENOMEM;
 196
 197                         r = strv_consume(&g, name);
 198                         if (r < 0)
 199                                 return r;
 200                 }
 201
 202         next:
 203                 r = acl_get_entry(acl, ACL_NEXT_ENTRY, &entry);
 204         }
 205
 206         if (ret_groups)
 207                 *ret_groups = TAKE_PTR(g);
 208
 209         return ret;
 210 }
 211
 212 int parse_acl(const char *text, acl_t *acl_access, acl_t *acl_default, bool want_mask) {
 213         _cleanup_free_ char **a = NULL, **d = NULL; /* strings are not freed */
 214         _cleanup_strv_free_ char **split;
 215         char **entry;
 216         int r = -EINVAL;
 217         _cleanup_(acl_freep) acl_t a_acl = NULL, d_acl = NULL;
 218
 219         split = strv_split(text, ",");
 220         if (!split)
 221                 return -ENOMEM;
 222
 223         STRV_FOREACH(entry, split) {
 224                 char *p;
 225
 226                 p = STARTSWITH_SET(*entry, "default:", "d:");
 227                 if (p)
 228                         r = strv_push(&d, p);
 229                 else
 230                         r = strv_push(&a, *entry);
 231                 if (r < 0)
 232                         return r;
 233         }
 234
 235         if (!strv_isempty(a)) {
 236                 _cleanup_free_ char *join;
 237
 238                 join = strv_join(a, ",");
 239                 if (!join)
 240                         return -ENOMEM;
 241
 242                 a_acl = acl_from_text(join);
 243                 if (!a_acl)
 244                         return -errno;
 245
 246                 if (want_mask) {
 247                         r = calc_acl_mask_if_needed(&a_acl);
 248                         if (r < 0)
 249                                 return r;
 250                 }
 251         }
 252
 253         if (!strv_isempty(d)) {
 254                 _cleanup_free_ char *join;
 255
 256                 join = strv_join(d, ",");
 257                 if (!join)
 258                         return -ENOMEM;
 259
 260                 d_acl = acl_from_text(join);
 261                 if (!d_acl)
 262                         return -errno;
 263
 264                 if (want_mask) {
 265                         r = calc_acl_mask_if_needed(&d_acl);
 266                         if (r < 0)
 267                                 return r;
 268                 }
 269         }
 270
 271         *acl_access = TAKE_PTR(a_acl);
 272         *acl_default = TAKE_PTR(d_acl);
 273
 274         return 0;
 275 }
 276
 277 static int acl_entry_equal(acl_entry_t a, acl_entry_t b) {
 278         acl_tag_t tag_a, tag_b;
 279
 280         if (acl_get_tag_type(a, &tag_a) < 0)
 281                 return -errno;
 282
 283         if (acl_get_tag_type(b, &tag_b) < 0)
 284                 return -errno;
 285
 286         if (tag_a != tag_b)
 287                 return false;
 288
 289         switch (tag_a) {
 290         case ACL_USER_OBJ:
 291         case ACL_GROUP_OBJ:
 292         case ACL_MASK:
 293         case ACL_OTHER:
 294                 /* can have only one of those */
 295                 return true;
 296         case ACL_USER: {
 297                 _cleanup_(acl_free_uid_tpp) uid_t *uid_a = NULL, *uid_b = NULL;
 298
 299                 uid_a = acl_get_qualifier(a);
 300                 if (!uid_a)
 301                         return -errno;
 302
 303                 uid_b = acl_get_qualifier(b);
 304                 if (!uid_b)
 305                         return -errno;
 306
 307                 return *uid_a == *uid_b;
 308         }
 309         case ACL_GROUP: {
 310                 _cleanup_(acl_free_gid_tpp) gid_t *gid_a = NULL, *gid_b = NULL;
 311
 312                 gid_a = acl_get_qualifier(a);
 313                 if (!gid_a)
 314                         return -errno;
 315
 316                 gid_b = acl_get_qualifier(b);
 317                 if (!gid_b)
 318                         return -errno;
 319
 320                 return *gid_a == *gid_b;
 321         }
 322         default:
 323                 assert_not_reached("Unknown acl tag type");
 324         }
 325 }
 326
 327 static int find_acl_entry(acl_t acl, acl_entry_t entry, acl_entry_t *out) {
 328         acl_entry_t i;
 329         int r;
 330
 331         for (r = acl_get_entry(acl, ACL_FIRST_ENTRY, &i);
 332              r > 0;
 333              r = acl_get_entry(acl, ACL_NEXT_ENTRY, &i)) {
 334
 335                 r = acl_entry_equal(i, entry);
 336                 if (r < 0)
 337                         return r;
 338                 if (r > 0) {
 339                         *out = i;
 340                         return 1;
 341                 }
 342         }
 343         if (r < 0)
 344                 return -errno;
 345         return 0;
 346 }
 347
 348 int acls_for_file(const char *path, acl_type_t type, acl_t new, acl_t *acl) {
 349         _cleanup_(acl_freep) acl_t old;
 350         acl_entry_t i;
 351         int r;
 352
 353         old = acl_get_file(path, type);
 354         if (!old)
 355                 return -errno;
 356
 357         for (r = acl_get_entry(new, ACL_FIRST_ENTRY, &i);
 358              r > 0;
 359              r = acl_get_entry(new, ACL_NEXT_ENTRY, &i)) {
 360
 361                 acl_entry_t j;
 362
 363                 r = find_acl_entry(old, i, &j);
 364                 if (r < 0)
 365                         return r;
 366                 if (r == 0)
 367                         if (acl_create_entry(&old, &j) < 0)
 368                                 return -errno;
 369
 370                 if (acl_copy_entry(j, i) < 0)
 371                         return -errno;
 372         }
 373         if (r < 0)
 374                 return -errno;
 375
 376         *acl = TAKE_PTR(old);
 377
 378         return 0;
 379 }
 380
 381 /* POSIX says that ACL_{READ,WRITE,EXECUTE} don't have to be bitmasks. But that is a natural thing to do and
 382  * all extant implementations do it. Let's make sure that we fail verbosely in the (imho unlikely) scenario
 383  * that we get a new implementation that does not satisfy this. */
 384 assert_cc(!(ACL_READ & ACL_WRITE));
 385 assert_cc(!(ACL_WRITE & ACL_EXECUTE));
 386 assert_cc(!(ACL_EXECUTE & ACL_READ));
 387 assert_cc((unsigned) ACL_READ == ACL_READ);
 388 assert_cc((unsigned) ACL_WRITE == ACL_WRITE);
 389 assert_cc((unsigned) ACL_EXECUTE == ACL_EXECUTE);
 390
 391 int fd_add_uid_acl_permission(
 392                 int fd,
 393                 uid_t uid,
 394                 unsigned mask) {
 395
 396         _cleanup_(acl_freep) acl_t acl = NULL;
 397         acl_permset_t permset;
 398         acl_entry_t entry;
 399         int r;
 400
 401         /* Adds an ACL entry for the specified file to allow the indicated access to the specified
 402          * user. Operates purely incrementally. */
 403
 404         assert(fd >= 0);
 405         assert(uid_is_valid(uid));
 406
 407         acl = acl_get_fd(fd);
 408         if (!acl)
 409                 return -errno;
 410
 411         r = acl_find_uid(acl, uid, &entry);
 412         if (r <= 0) {
 413                 if (acl_create_entry(&acl, &entry) < 0 ||
 414                     acl_set_tag_type(entry, ACL_USER) < 0 ||
 415                     acl_set_qualifier(entry, &uid) < 0)
 416                         return -errno;
 417         }
 418
 419         if (acl_get_permset(entry, &permset) < 0)
 420                 return -errno;
 421
 422         if ((mask & ACL_READ) && acl_add_perm(permset, ACL_READ) < 0)
 423                 return -errno;
 424         if ((mask & ACL_WRITE) && acl_add_perm(permset, ACL_WRITE) < 0)
 425                 return -errno;
 426         if ((mask & ACL_EXECUTE) && acl_add_perm(permset, ACL_EXECUTE) < 0)
 427                 return -errno;
 428
 429         r = calc_acl_mask_if_needed(&acl);
 430         if (r < 0)
 431                 return r;
 432
 433         if (acl_set_fd(fd, acl) < 0)
 434                 return -errno;
 435
 436         return 0;
 437 }