src/basic/selinux-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <errno.h>
   4 #include <fcntl.h>
   5 #include <malloc.h>
   6 #include <stddef.h>
   7 #include <string.h>
   8 #include <sys/stat.h>
   9 #include <sys/time.h>
  10 #include <sys/types.h>
  11 #include <sys/un.h>
  12 #include <syslog.h>
  13
  14 #if HAVE_SELINUX
  15 #include <selinux/avc.h>
  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 "errno-util.h"
  23 #include "fd-util.h"
  24 #include "log.h"
  25 #include "macro.h"
  26 #include "path-util.h"
  27 #include "selinux-util.h"
  28 #include "stdio-util.h"
  29 #include "time-util.h"
  30
  31 #if HAVE_SELINUX
  32 DEFINE_TRIVIAL_CLEANUP_FUNC(context_t, context_free);
  33 #define _cleanup_context_free_ _cleanup_(context_freep)
  34
  35 static int mac_selinux_reload(int seqno);
  36
  37 static int cached_use = -1;
  38 static struct selabel_handle *label_hnd = NULL;
  39
  40 #define log_enforcing(...) log_full(security_getenforce() == 1 ? LOG_ERR : LOG_WARNING, __VA_ARGS__)
  41 #define log_enforcing_errno(r, ...) log_full_errno(security_getenforce() == 1 ? LOG_ERR : LOG_WARNING, r, __VA_ARGS__)
  42 #endif
  43
  44 bool mac_selinux_use(void) {
  45 #if HAVE_SELINUX
  46         if (cached_use < 0)
  47                 cached_use = is_selinux_enabled() > 0;
  48
  49         return cached_use;
  50 #else
  51         return false;
  52 #endif
  53 }
  54
  55 void mac_selinux_retest(void) {
  56 #if HAVE_SELINUX
  57         cached_use = -1;
  58 #endif
  59 }
  60
  61 int mac_selinux_init(void) {
  62         int r = 0;
  63
  64 #if HAVE_SELINUX
  65         usec_t before_timestamp, after_timestamp;
  66         struct mallinfo before_mallinfo, after_mallinfo;
  67
  68         selinux_set_callback(SELINUX_CB_POLICYLOAD, (union selinux_callback) mac_selinux_reload);
  69
  70         if (label_hnd)
  71                 return 0;
  72
  73         if (!mac_selinux_use())
  74                 return 0;
  75
  76         before_mallinfo = mallinfo();
  77         before_timestamp = now(CLOCK_MONOTONIC);
  78
  79         label_hnd = selabel_open(SELABEL_CTX_FILE, NULL, 0);
  80         if (!label_hnd) {
  81                 log_enforcing_errno(errno, "Failed to initialize SELinux context: %m");
  82                 r = security_getenforce() == 1 ? -errno : 0;
  83         } else  {
  84                 char timespan[FORMAT_TIMESPAN_MAX];
  85                 int l;
  86
  87                 after_timestamp = now(CLOCK_MONOTONIC);
  88                 after_mallinfo = mallinfo();
  89
  90                 l = after_mallinfo.uordblks > before_mallinfo.uordblks ? after_mallinfo.uordblks - before_mallinfo.uordblks : 0;
  91
  92                 log_debug("Successfully loaded SELinux database in %s, size on heap is %iK.",
  93                           format_timespan(timespan, sizeof(timespan), after_timestamp - before_timestamp, 0),
  94                           (l+1023)/1024);
  95         }
  96 #endif
  97
  98         return r;
  99 }
 100
 101 void mac_selinux_finish(void) {
 102
 103 #if HAVE_SELINUX
 104         if (!label_hnd)
 105                 return;
 106
 107         selabel_close(label_hnd);
 108         label_hnd = NULL;
 109 #endif
 110 }
 111
 112 #if HAVE_SELINUX
 113 static int mac_selinux_reload(int seqno) {
 114         struct selabel_handle *backup_label_hnd;
 115
 116         if (!label_hnd)
 117                 return 0;
 118
 119         backup_label_hnd = TAKE_PTR(label_hnd);
 120
 121         /* try to initialize new handle
 122          *    on success close backup
 123          *    on failure restore backup */
 124         if (mac_selinux_init() == 0)
 125                 selabel_close(backup_label_hnd);
 126         else
 127                 label_hnd = backup_label_hnd;
 128
 129         return 0;
 130 }
 131 #endif
 132
 133 int mac_selinux_fix(const char *path, LabelFixFlags flags) {
 134
 135 #if HAVE_SELINUX
 136         char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
 137         _cleanup_freecon_ char* fcon = NULL;
 138         _cleanup_close_ int fd = -1;
 139         struct stat st;
 140         int r;
 141
 142         assert(path);
 143
 144         /* if mac_selinux_init() wasn't called before we are a NOOP */
 145         if (!label_hnd)
 146                 return 0;
 147
 148         /* Open the file as O_PATH, to pin it while we determine and adjust the label */
 149         fd = open(path, O_NOFOLLOW|O_CLOEXEC|O_PATH);
 150         if (fd < 0) {
 151                 if ((flags & LABEL_IGNORE_ENOENT) && errno == ENOENT)
 152                         return 0;
 153
 154                 return -errno;
 155         }
 156
 157         if (fstat(fd, &st) < 0)
 158                 return -errno;
 159
 160         /* Check for policy reload so 'label_hnd' is kept up-to-date by callbacks */
 161         (void) avc_netlink_check_nb();
 162
 163         if (selabel_lookup_raw(label_hnd, &fcon, path, st.st_mode) < 0) {
 164                 r = -errno;
 165
 166                 /* If there's no label to set, then exit without warning */
 167                 if (r == -ENOENT)
 168                         return 0;
 169
 170                 goto fail;
 171         }
 172
 173         xsprintf(procfs_path, "/proc/self/fd/%i", fd);
 174         if (setfilecon_raw(procfs_path, fcon) < 0) {
 175                 _cleanup_freecon_ char *oldcon = NULL;
 176
 177                 r = -errno;
 178
 179                 /* If the FS doesn't support labels, then exit without warning */
 180                 if (r == -EOPNOTSUPP)
 181                         return 0;
 182
 183                 /* It the FS is read-only and we were told to ignore failures caused by that, suppress error */
 184                 if (r == -EROFS && (flags & LABEL_IGNORE_EROFS))
 185                         return 0;
 186
 187                 /* If the old label is identical to the new one, suppress any kind of error */
 188                 if (getfilecon_raw(procfs_path, &oldcon) >= 0 && streq(fcon, oldcon))
 189                         return 0;
 190
 191                 goto fail;
 192         }
 193
 194         return 0;
 195
 196 fail:
 197         log_enforcing_errno(r, "Unable to fix SELinux security context of %s: %m", path);
 198         if (security_getenforce() == 1)
 199                 return r;
 200 #endif
 201
 202         return 0;
 203 }
 204
 205 int mac_selinux_apply(const char *path, const char *label) {
 206
 207 #if HAVE_SELINUX
 208         if (!mac_selinux_use())
 209                 return 0;
 210
 211         assert(path);
 212         assert(label);
 213
 214         if (setfilecon(path, label) < 0) {
 215                 log_enforcing_errno(errno, "Failed to set SELinux security context %s on path %s: %m", label, path);
 216                 if (security_getenforce() > 0)
 217                         return -errno;
 218         }
 219 #endif
 220         return 0;
 221 }
 222
 223 int mac_selinux_get_create_label_from_exe(const char *exe, char **label) {
 224         int r = -EOPNOTSUPP;
 225
 226 #if HAVE_SELINUX
 227         _cleanup_freecon_ char *mycon = NULL, *fcon = NULL;
 228         security_class_t sclass;
 229
 230         assert(exe);
 231         assert(label);
 232
 233         if (!mac_selinux_use())
 234                 return -EOPNOTSUPP;
 235
 236         r = getcon_raw(&mycon);
 237         if (r < 0)
 238                 return -errno;
 239
 240         r = getfilecon_raw(exe, &fcon);
 241         if (r < 0)
 242                 return -errno;
 243
 244         sclass = string_to_security_class("process");
 245         if (sclass == 0)
 246                 return -ENOSYS;
 247
 248         r = security_compute_create_raw(mycon, fcon, sclass, label);
 249         if (r < 0)
 250                 return -errno;
 251 #endif
 252
 253         return r;
 254 }
 255
 256 int mac_selinux_get_our_label(char **label) {
 257         int r = -EOPNOTSUPP;
 258
 259         assert(label);
 260
 261 #if HAVE_SELINUX
 262         if (!mac_selinux_use())
 263                 return -EOPNOTSUPP;
 264
 265         r = getcon_raw(label);
 266         if (r < 0)
 267                 return -errno;
 268 #endif
 269
 270         return r;
 271 }
 272
 273 int mac_selinux_get_child_mls_label(int socket_fd, const char *exe, const char *exec_label, char **label) {
 274         int r = -EOPNOTSUPP;
 275
 276 #if HAVE_SELINUX
 277         _cleanup_freecon_ char *mycon = NULL, *peercon = NULL, *fcon = NULL;
 278         _cleanup_context_free_ context_t pcon = NULL, bcon = NULL;
 279         security_class_t sclass;
 280         const char *range = NULL;
 281
 282         assert(socket_fd >= 0);
 283         assert(exe);
 284         assert(label);
 285
 286         if (!mac_selinux_use())
 287                 return -EOPNOTSUPP;
 288
 289         r = getcon_raw(&mycon);
 290         if (r < 0)
 291                 return -errno;
 292
 293         r = getpeercon_raw(socket_fd, &peercon);
 294         if (r < 0)
 295                 return -errno;
 296
 297         if (!exec_label) {
 298                 /* If there is no context set for next exec let's use context
 299                    of target executable */
 300                 r = getfilecon_raw(exe, &fcon);
 301                 if (r < 0)
 302                         return -errno;
 303         }
 304
 305         bcon = context_new(mycon);
 306         if (!bcon)
 307                 return -ENOMEM;
 308
 309         pcon = context_new(peercon);
 310         if (!pcon)
 311                 return -ENOMEM;
 312
 313         range = context_range_get(pcon);
 314         if (!range)
 315                 return -errno;
 316
 317         r = context_range_set(bcon, range);
 318         if (r)
 319                 return -errno;
 320
 321         freecon(mycon);
 322         mycon = strdup(context_str(bcon));
 323         if (!mycon)
 324                 return -ENOMEM;
 325
 326         sclass = string_to_security_class("process");
 327         if (sclass == 0)
 328                 return -ENOSYS;
 329
 330         r = security_compute_create_raw(mycon, fcon, sclass, label);
 331         if (r < 0)
 332                 return -errno;
 333 #endif
 334
 335         return r;
 336 }
 337
 338 char* mac_selinux_free(char *label) {
 339
 340 #if HAVE_SELINUX
 341         if (!label)
 342                 return NULL;
 343
 344         if (!mac_selinux_use())
 345                 return NULL;
 346
 347         freecon(label);
 348 #endif
 349
 350         return NULL;
 351 }
 352
 353 #if HAVE_SELINUX
 354 static int selinux_create_file_prepare_abspath(const char *abspath, mode_t mode) {
 355         _cleanup_freecon_ char *filecon = NULL;
 356         int r;
 357
 358         assert(abspath);
 359         assert(path_is_absolute(abspath));
 360
 361         /* Check for policy reload so 'label_hnd' is kept up-to-date by callbacks */
 362         (void) avc_netlink_check_nb();
 363
 364         r = selabel_lookup_raw(label_hnd, &filecon, abspath, mode);
 365         if (r < 0) {
 366                 /* No context specified by the policy? Proceed without setting it. */
 367                 if (errno == ENOENT)
 368                         return 0;
 369
 370                 log_enforcing_errno(errno, "Failed to determine SELinux security context for %s: %m", abspath);
 371         } else {
 372                 if (setfscreatecon_raw(filecon) >= 0)
 373                         return 0; /* Success! */
 374
 375                 log_enforcing_errno(errno, "Failed to set SELinux security context %s for %s: %m", filecon, abspath);
 376         }
 377
 378         if (security_getenforce() > 0)
 379                 return -errno;
 380
 381         return 0;
 382 }
 383 #endif
 384
 385 int mac_selinux_create_file_prepare_at(int dirfd, const char *path, mode_t mode) {
 386         int r = 0;
 387
 388 #if HAVE_SELINUX
 389         _cleanup_free_ char *abspath = NULL;
 390
 391         assert(path);
 392
 393         if (!label_hnd)
 394                 return 0;
 395
 396         if (!path_is_absolute(path)) {
 397                 _cleanup_free_ char *p = NULL;
 398
 399                 if (dirfd == AT_FDCWD)
 400                         r = safe_getcwd(&p);
 401                 else
 402                         r = fd_get_path(dirfd, &p);
 403                 if (r < 0)
 404                         return r;
 405
 406                 path = abspath = path_join(p, path);
 407                 if (!path)
 408                         return -ENOMEM;
 409         }
 410
 411         r = selinux_create_file_prepare_abspath(path, mode);
 412 #endif
 413         return r;
 414 }
 415
 416 int mac_selinux_create_file_prepare(const char *path, mode_t mode) {
 417         int r = 0;
 418
 419 #if HAVE_SELINUX
 420         _cleanup_free_ char *abspath = NULL;
 421
 422         assert(path);
 423
 424         if (!label_hnd)
 425                 return 0;
 426
 427         r = path_make_absolute_cwd(path, &abspath);
 428         if (r < 0)
 429                 return r;
 430
 431         r = selinux_create_file_prepare_abspath(abspath, mode);
 432 #endif
 433         return r;
 434 }
 435
 436 void mac_selinux_create_file_clear(void) {
 437
 438 #if HAVE_SELINUX
 439         PROTECT_ERRNO;
 440
 441         if (!mac_selinux_use())
 442                 return;
 443
 444         setfscreatecon_raw(NULL);
 445 #endif
 446 }
 447
 448 int mac_selinux_create_socket_prepare(const char *label) {
 449
 450 #if HAVE_SELINUX
 451         if (!mac_selinux_use())
 452                 return 0;
 453
 454         assert(label);
 455
 456         if (setsockcreatecon(label) < 0) {
 457                 log_enforcing_errno(errno, "Failed to set SELinux security context %s for sockets: %m", label);
 458
 459                 if (security_getenforce() == 1)
 460                         return -errno;
 461         }
 462 #endif
 463
 464         return 0;
 465 }
 466
 467 void mac_selinux_create_socket_clear(void) {
 468
 469 #if HAVE_SELINUX
 470         PROTECT_ERRNO;
 471
 472         if (!mac_selinux_use())
 473                 return;
 474
 475         setsockcreatecon_raw(NULL);
 476 #endif
 477 }
 478
 479 int mac_selinux_bind(int fd, const struct sockaddr *addr, socklen_t addrlen) {
 480
 481         /* Binds a socket and label its file system object according to the SELinux policy */
 482
 483 #if HAVE_SELINUX
 484         _cleanup_freecon_ char *fcon = NULL;
 485         const struct sockaddr_un *un;
 486         bool context_changed = false;
 487         char *path;
 488         int r;
 489
 490         assert(fd >= 0);
 491         assert(addr);
 492         assert(addrlen >= sizeof(sa_family_t));
 493
 494         if (!label_hnd)
 495                 goto skipped;
 496
 497         /* Filter out non-local sockets */
 498         if (addr->sa_family != AF_UNIX)
 499                 goto skipped;
 500
 501         /* Filter out anonymous sockets */
 502         if (addrlen < offsetof(struct sockaddr_un, sun_path) + 1)
 503                 goto skipped;
 504
 505         /* Filter out abstract namespace sockets */
 506         un = (const struct sockaddr_un*) addr;
 507         if (un->sun_path[0] == 0)
 508                 goto skipped;
 509
 510         path = strndupa(un->sun_path, addrlen - offsetof(struct sockaddr_un, sun_path));
 511
 512         /* Check for policy reload so 'label_hnd' is kept up-to-date by callbacks */
 513         (void) avc_netlink_check_nb();
 514
 515         if (path_is_absolute(path))
 516                 r = selabel_lookup_raw(label_hnd, &fcon, path, S_IFSOCK);
 517         else {
 518                 _cleanup_free_ char *newpath = NULL;
 519
 520                 r = path_make_absolute_cwd(path, &newpath);
 521                 if (r < 0)
 522                         return r;
 523
 524                 r = selabel_lookup_raw(label_hnd, &fcon, newpath, S_IFSOCK);
 525         }
 526
 527         if (r < 0) {
 528                 /* No context specified by the policy? Proceed without setting it */
 529                 if (errno == ENOENT)
 530                         goto skipped;
 531
 532                 log_enforcing_errno(errno, "Failed to determine SELinux security context for %s: %m", path);
 533                 if (security_getenforce() > 0)
 534                         return -errno;
 535
 536         } else {
 537                 if (setfscreatecon_raw(fcon) < 0) {
 538                         log_enforcing_errno(errno, "Failed to set SELinux security context %s for %s: %m", fcon, path);
 539                         if (security_getenforce() > 0)
 540                                 return -errno;
 541                 } else
 542                         context_changed = true;
 543         }
 544
 545         r = bind(fd, addr, addrlen) < 0 ? -errno : 0;
 546
 547         if (context_changed)
 548                 setfscreatecon_raw(NULL);
 549
 550         return r;
 551
 552 skipped:
 553 #endif
 554         if (bind(fd, addr, addrlen) < 0)
 555                 return -errno;
 556
 557         return 0;
 558 }