src/basic/selinux-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   Copyright 2010 Lennart Poettering
   4 ***/
   5
   6 #include <errno.h>
   7 #include <malloc.h>
   8 #include <stddef.h>
   9 #include <string.h>
  10 #include <sys/stat.h>
  11 #include <sys/time.h>
  12 #include <sys/un.h>
  13 #include <syslog.h>
  14
  15 #if HAVE_SELINUX
  16 #include <selinux/context.h>
  17 #include <selinux/label.h>
  18 #include <selinux/selinux.h>
  19 #endif
  20
  21 #include "alloc-util.h"
  22 #include "fd-util.h"
  23 #include "log.h"
  24 #include "macro.h"
  25 #include "path-util.h"
  26 #include "selinux-util.h"
  27 #include "stdio-util.h"
  28 #include "time-util.h"
  29 #include "util.h"
  30
  31 #if HAVE_SELINUX
  32 DEFINE_TRIVIAL_CLEANUP_FUNC(char*, freecon);
  33 DEFINE_TRIVIAL_CLEANUP_FUNC(context_t, context_free);
  34
  35 #define _cleanup_freecon_ _cleanup_(freeconp)
  36 #define _cleanup_context_free_ _cleanup_(context_freep)
  37
  38 static int cached_use = -1;
  39 static struct selabel_handle *label_hnd = NULL;
  40
  41 #define log_enforcing(...) log_full(security_getenforce() == 1 ? LOG_ERR : LOG_DEBUG, __VA_ARGS__)
  42 #define log_enforcing_errno(r, ...) log_full_errno(security_getenforce() == 1 ? LOG_ERR : LOG_DEBUG, r, __VA_ARGS__)
  43 #endif
  44
  45 bool mac_selinux_use(void) {
  46 #if HAVE_SELINUX
  47         if (cached_use < 0)
  48                 cached_use = is_selinux_enabled() > 0;
  49
  50         return cached_use;
  51 #else
  52         return false;
  53 #endif
  54 }
  55
  56 void mac_selinux_retest(void) {
  57 #if HAVE_SELINUX
  58         cached_use = -1;
  59 #endif
  60 }
  61
  62 int mac_selinux_init(void) {
  63         int r = 0;
  64
  65 #if HAVE_SELINUX
  66         usec_t before_timestamp, after_timestamp;
  67         struct mallinfo before_mallinfo, after_mallinfo;
  68
  69         if (label_hnd)
  70                 return 0;
  71
  72         if (!mac_selinux_use())
  73                 return 0;
  74
  75         before_mallinfo = mallinfo();
  76         before_timestamp = now(CLOCK_MONOTONIC);
  77
  78         label_hnd = selabel_open(SELABEL_CTX_FILE, NULL, 0);
  79         if (!label_hnd) {
  80                 log_enforcing_errno(errno, "Failed to initialize SELinux context: %m");
  81                 r = security_getenforce() == 1 ? -errno : 0;
  82         } else  {
  83                 char timespan[FORMAT_TIMESPAN_MAX];
  84                 int l;
  85
  86                 after_timestamp = now(CLOCK_MONOTONIC);
  87                 after_mallinfo = mallinfo();
  88
  89                 l = after_mallinfo.uordblks > before_mallinfo.uordblks ? after_mallinfo.uordblks - before_mallinfo.uordblks : 0;
  90
  91                 log_debug("Successfully loaded SELinux database in %s, size on heap is %iK.",
  92                           format_timespan(timespan, sizeof(timespan), after_timestamp - before_timestamp, 0),
  93                           (l+1023)/1024);
  94         }
  95 #endif
  96
  97         return r;
  98 }
  99
 100 void mac_selinux_finish(void) {
 101
 102 #if HAVE_SELINUX
 103         if (!label_hnd)
 104                 return;
 105
 106         selabel_close(label_hnd);
 107         label_hnd = NULL;
 108 #endif
 109 }
 110
 111 int mac_selinux_fix(const char *path, LabelFixFlags flags) {
 112
 113 #if HAVE_SELINUX
 114         char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
 115         _cleanup_freecon_ char* fcon = NULL;
 116         _cleanup_close_ int fd = -1;
 117         struct stat st;
 118         int r;
 119
 120         assert(path);
 121
 122         /* if mac_selinux_init() wasn't called before we are a NOOP */
 123         if (!label_hnd)
 124                 return 0;
 125
 126         /* Open the file as O_PATH, to pin it while we determine and adjust the label */
 127         fd = open(path, O_NOFOLLOW|O_CLOEXEC|O_PATH);
 128         if (fd < 0) {
 129                 if ((flags & LABEL_IGNORE_ENOENT) && errno == ENOENT)
 130                         return 0;
 131
 132                 return -errno;
 133         }
 134
 135         if (fstat(fd, &st) < 0)
 136                 return -errno;
 137
 138         if (selabel_lookup_raw(label_hnd, &fcon, path, st.st_mode) < 0) {
 139                 r = -errno;
 140
 141                 /* If there's no label to set, then exit without warning */
 142                 if (r == -ENOENT)
 143                         return 0;
 144
 145                 goto fail;
 146         }
 147
 148         xsprintf(procfs_path, "/proc/self/fd/%i", fd);
 149         if (setfilecon_raw(procfs_path, fcon) < 0) {
 150                 _cleanup_freecon_ char *oldcon = NULL;
 151
 152                 r = -errno;
 153
 154                 /* If the FS doesn't support labels, then exit without warning */
 155                 if (r == -EOPNOTSUPP)
 156                         return 0;
 157
 158                 /* It the FS is read-only and we were told to ignore failures caused by that, suppress error */
 159                 if (r == -EROFS && (flags & LABEL_IGNORE_EROFS))
 160                         return 0;
 161
 162                 /* If the old label is identical to the new one, suppress any kind of error */
 163                 if (getfilecon_raw(procfs_path, &oldcon) >= 0 && streq(fcon, oldcon))
 164                         return 0;
 165
 166                 goto fail;
 167         }
 168
 169         return 0;
 170
 171 fail:
 172         log_enforcing_errno(r, "Unable to fix SELinux security context of %s: %m", path);
 173         if (security_getenforce() == 1)
 174                 return r;
 175 #endif
 176
 177         return 0;
 178 }
 179
 180 int mac_selinux_apply(const char *path, const char *label) {
 181
 182 #if HAVE_SELINUX
 183         if (!mac_selinux_use())
 184                 return 0;
 185
 186         assert(path);
 187         assert(label);
 188
 189         if (setfilecon(path, label) < 0) {
 190                 log_enforcing_errno(errno, "Failed to set SELinux security context %s on path %s: %m", label, path);
 191                 if (security_getenforce() > 0)
 192                         return -errno;
 193         }
 194 #endif
 195         return 0;
 196 }
 197
 198 int mac_selinux_get_create_label_from_exe(const char *exe, char **label) {
 199         int r = -EOPNOTSUPP;
 200
 201 #if HAVE_SELINUX
 202         _cleanup_freecon_ char *mycon = NULL, *fcon = NULL;
 203         security_class_t sclass;
 204
 205         assert(exe);
 206         assert(label);
 207
 208         if (!mac_selinux_use())
 209                 return -EOPNOTSUPP;
 210
 211         r = getcon_raw(&mycon);
 212         if (r < 0)
 213                 return -errno;
 214
 215         r = getfilecon_raw(exe, &fcon);
 216         if (r < 0)
 217                 return -errno;
 218
 219         sclass = string_to_security_class("process");
 220         r = security_compute_create_raw(mycon, fcon, sclass, label);
 221         if (r < 0)
 222                 return -errno;
 223 #endif
 224
 225         return r;
 226 }
 227
 228 int mac_selinux_get_our_label(char **label) {
 229         int r = -EOPNOTSUPP;
 230
 231         assert(label);
 232
 233 #if HAVE_SELINUX
 234         if (!mac_selinux_use())
 235                 return -EOPNOTSUPP;
 236
 237         r = getcon_raw(label);
 238         if (r < 0)
 239                 return -errno;
 240 #endif
 241
 242         return r;
 243 }
 244
 245 int mac_selinux_get_child_mls_label(int socket_fd, const char *exe, const char *exec_label, char **label) {
 246         int r = -EOPNOTSUPP;
 247
 248 #if HAVE_SELINUX
 249         _cleanup_freecon_ char *mycon = NULL, *peercon = NULL, *fcon = NULL;
 250         _cleanup_context_free_ context_t pcon = NULL, bcon = NULL;
 251         security_class_t sclass;
 252         const char *range = NULL;
 253
 254         assert(socket_fd >= 0);
 255         assert(exe);
 256         assert(label);
 257
 258         if (!mac_selinux_use())
 259                 return -EOPNOTSUPP;
 260
 261         r = getcon_raw(&mycon);
 262         if (r < 0)
 263                 return -errno;
 264
 265         r = getpeercon_raw(socket_fd, &peercon);
 266         if (r < 0)
 267                 return -errno;
 268
 269         if (!exec_label) {
 270                 /* If there is no context set for next exec let's use context
 271                    of target executable */
 272                 r = getfilecon_raw(exe, &fcon);
 273                 if (r < 0)
 274                         return -errno;
 275         }
 276
 277         bcon = context_new(mycon);
 278         if (!bcon)
 279                 return -ENOMEM;
 280
 281         pcon = context_new(peercon);
 282         if (!pcon)
 283                 return -ENOMEM;
 284
 285         range = context_range_get(pcon);
 286         if (!range)
 287                 return -errno;
 288
 289         r = context_range_set(bcon, range);
 290         if (r)
 291                 return -errno;
 292
 293         freecon(mycon);
 294         mycon = strdup(context_str(bcon));
 295         if (!mycon)
 296                 return -ENOMEM;
 297
 298         sclass = string_to_security_class("process");
 299         r = security_compute_create_raw(mycon, fcon, sclass, label);
 300         if (r < 0)
 301                 return -errno;
 302 #endif
 303
 304         return r;
 305 }
 306
 307 char* mac_selinux_free(char *label) {
 308
 309 #if HAVE_SELINUX
 310         if (!label)
 311                 return NULL;
 312
 313         if (!mac_selinux_use())
 314                 return NULL;
 315
 316         freecon(label);
 317 #endif
 318
 319         return NULL;
 320 }
 321
 322 int mac_selinux_create_file_prepare(const char *path, mode_t mode) {
 323
 324 #if HAVE_SELINUX
 325         _cleanup_freecon_ char *filecon = NULL;
 326         int r;
 327
 328         assert(path);
 329
 330         if (!label_hnd)
 331                 return 0;
 332
 333         if (path_is_absolute(path))
 334                 r = selabel_lookup_raw(label_hnd, &filecon, path, mode);
 335         else {
 336                 _cleanup_free_ char *newpath = NULL;
 337
 338                 r = path_make_absolute_cwd(path, &newpath);
 339                 if (r < 0)
 340                         return r;
 341
 342                 r = selabel_lookup_raw(label_hnd, &filecon, newpath, mode);
 343         }
 344
 345         if (r < 0) {
 346                 /* No context specified by the policy? Proceed without setting it. */
 347                 if (errno == ENOENT)
 348                         return 0;
 349
 350                 log_enforcing_errno(errno, "Failed to determine SELinux security context for %s: %m", path);
 351         } else {
 352                 if (setfscreatecon_raw(filecon) >= 0)
 353                         return 0; /* Success! */
 354
 355                 log_enforcing_errno(errno, "Failed to set SELinux security context %s for %s: %m", filecon, path);
 356         }
 357
 358         if (security_getenforce() > 0)
 359                 return -errno;
 360
 361 #endif
 362         return 0;
 363 }
 364
 365 void mac_selinux_create_file_clear(void) {
 366
 367 #if HAVE_SELINUX
 368         PROTECT_ERRNO;
 369
 370         if (!mac_selinux_use())
 371                 return;
 372
 373         setfscreatecon_raw(NULL);
 374 #endif
 375 }
 376
 377 int mac_selinux_create_socket_prepare(const char *label) {
 378
 379 #if HAVE_SELINUX
 380         if (!mac_selinux_use())
 381                 return 0;
 382
 383         assert(label);
 384
 385         if (setsockcreatecon(label) < 0) {
 386                 log_enforcing_errno(errno, "Failed to set SELinux security context %s for sockets: %m", label);
 387
 388                 if (security_getenforce() == 1)
 389                         return -errno;
 390         }
 391 #endif
 392
 393         return 0;
 394 }
 395
 396 void mac_selinux_create_socket_clear(void) {
 397
 398 #if HAVE_SELINUX
 399         PROTECT_ERRNO;
 400
 401         if (!mac_selinux_use())
 402                 return;
 403
 404         setsockcreatecon_raw(NULL);
 405 #endif
 406 }
 407
 408 int mac_selinux_bind(int fd, const struct sockaddr *addr, socklen_t addrlen) {
 409
 410         /* Binds a socket and label its file system object according to the SELinux policy */
 411
 412 #if HAVE_SELINUX
 413         _cleanup_freecon_ char *fcon = NULL;
 414         const struct sockaddr_un *un;
 415         bool context_changed = false;
 416         char *path;
 417         int r;
 418
 419         assert(fd >= 0);
 420         assert(addr);
 421         assert(addrlen >= sizeof(sa_family_t));
 422
 423         if (!label_hnd)
 424                 goto skipped;
 425
 426         /* Filter out non-local sockets */
 427         if (addr->sa_family != AF_UNIX)
 428                 goto skipped;
 429
 430         /* Filter out anonymous sockets */
 431         if (addrlen < offsetof(struct sockaddr_un, sun_path) + 1)
 432                 goto skipped;
 433
 434         /* Filter out abstract namespace sockets */
 435         un = (const struct sockaddr_un*) addr;
 436         if (un->sun_path[0] == 0)
 437                 goto skipped;
 438
 439         path = strndupa(un->sun_path, addrlen - offsetof(struct sockaddr_un, sun_path));
 440
 441         if (path_is_absolute(path))
 442                 r = selabel_lookup_raw(label_hnd, &fcon, path, S_IFSOCK);
 443         else {
 444                 _cleanup_free_ char *newpath = NULL;
 445
 446                 r = path_make_absolute_cwd(path, &newpath);
 447                 if (r < 0)
 448                         return r;
 449
 450                 r = selabel_lookup_raw(label_hnd, &fcon, newpath, S_IFSOCK);
 451         }
 452
 453         if (r < 0) {
 454                 /* No context specified by the policy? Proceed without setting it */
 455                 if (errno == ENOENT)
 456                         goto skipped;
 457
 458                 log_enforcing_errno(errno, "Failed to determine SELinux security context for %s: %m", path);
 459                 if (security_getenforce() > 0)
 460                         return -errno;
 461
 462         } else {
 463                 if (setfscreatecon_raw(fcon) < 0) {
 464                         log_enforcing_errno(errno, "Failed to set SELinux security context %s for %s: %m", fcon, path);
 465                         if (security_getenforce() > 0)
 466                                 return -errno;
 467                 } else
 468                         context_changed = true;
 469         }
 470
 471         r = bind(fd, addr, addrlen) < 0 ? -errno : 0;
 472
 473         if (context_changed)
 474                 setfscreatecon_raw(NULL);
 475
 476         return r;
 477
 478 skipped:
 479 #endif
 480         if (bind(fd, addr, addrlen) < 0)
 481                 return -errno;
 482
 483         return 0;
 484 }