src/basic/selinux-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   This file is part of systemd.
   4
   5   Copyright 2010 Lennart Poettering
   6 ***/
   7
   8 #include <errno.h>
   9 #include <malloc.h>
  10 #include <stddef.h>
  11 #include <string.h>
  12 #include <sys/stat.h>
  13 #include <sys/time.h>
  14 #include <sys/un.h>
  15 #include <syslog.h>
  16
  17 #if HAVE_SELINUX
  18 #include <selinux/context.h>
  19 #include <selinux/label.h>
  20 #include <selinux/selinux.h>
  21 #endif
  22
  23 #include "alloc-util.h"
  24 #include "fd-util.h"
  25 #include "log.h"
  26 #include "macro.h"
  27 #include "path-util.h"
  28 #include "selinux-util.h"
  29 #include "stdio-util.h"
  30 #include "time-util.h"
  31 #include "util.h"
  32
  33 #if HAVE_SELINUX
  34 DEFINE_TRIVIAL_CLEANUP_FUNC(char*, freecon);
  35 DEFINE_TRIVIAL_CLEANUP_FUNC(context_t, context_free);
  36
  37 #define _cleanup_freecon_ _cleanup_(freeconp)
  38 #define _cleanup_context_free_ _cleanup_(context_freep)
  39
  40 static int cached_use = -1;
  41 static struct selabel_handle *label_hnd = NULL;
  42
  43 #define log_enforcing(...) log_full(security_getenforce() == 1 ? LOG_ERR : LOG_DEBUG, __VA_ARGS__)
  44 #define log_enforcing_errno(r, ...) log_full_errno(security_getenforce() == 1 ? LOG_ERR : LOG_DEBUG, r, __VA_ARGS__)
  45 #endif
  46
  47 bool mac_selinux_use(void) {
  48 #if HAVE_SELINUX
  49         if (cached_use < 0)
  50                 cached_use = is_selinux_enabled() > 0;
  51
  52         return cached_use;
  53 #else
  54         return false;
  55 #endif
  56 }
  57
  58 void mac_selinux_retest(void) {
  59 #if HAVE_SELINUX
  60         cached_use = -1;
  61 #endif
  62 }
  63
  64 int mac_selinux_init(void) {
  65         int r = 0;
  66
  67 #if HAVE_SELINUX
  68         usec_t before_timestamp, after_timestamp;
  69         struct mallinfo before_mallinfo, after_mallinfo;
  70
  71         if (label_hnd)
  72                 return 0;
  73
  74         if (!mac_selinux_use())
  75                 return 0;
  76
  77         before_mallinfo = mallinfo();
  78         before_timestamp = now(CLOCK_MONOTONIC);
  79
  80         label_hnd = selabel_open(SELABEL_CTX_FILE, NULL, 0);
  81         if (!label_hnd) {
  82                 log_enforcing("Failed to initialize SELinux context: %m");
  83                 r = security_getenforce() == 1 ? -errno : 0;
  84         } else  {
  85                 char timespan[FORMAT_TIMESPAN_MAX];
  86                 int l;
  87
  88                 after_timestamp = now(CLOCK_MONOTONIC);
  89                 after_mallinfo = mallinfo();
  90
  91                 l = after_mallinfo.uordblks > before_mallinfo.uordblks ? after_mallinfo.uordblks - before_mallinfo.uordblks : 0;
  92
  93                 log_debug("Successfully loaded SELinux database in %s, size on heap is %iK.",
  94                           format_timespan(timespan, sizeof(timespan), after_timestamp - before_timestamp, 0),
  95                           (l+1023)/1024);
  96         }
  97 #endif
  98
  99         return r;
 100 }
 101
 102 void mac_selinux_finish(void) {
 103
 104 #if HAVE_SELINUX
 105         if (!label_hnd)
 106                 return;
 107
 108         selabel_close(label_hnd);
 109         label_hnd = NULL;
 110 #endif
 111 }
 112
 113 int mac_selinux_fix(const char *path, LabelFixFlags flags) {
 114
 115 #if HAVE_SELINUX
 116         char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
 117         _cleanup_freecon_ char* fcon = NULL;
 118         _cleanup_close_ int fd = -1;
 119         struct stat st;
 120         int r;
 121
 122         assert(path);
 123
 124         /* if mac_selinux_init() wasn't called before we are a NOOP */
 125         if (!label_hnd)
 126                 return 0;
 127
 128         /* Open the file as O_PATH, to pin it while we determine and adjust the label */
 129         fd = open(path, O_NOFOLLOW|O_CLOEXEC|O_PATH);
 130         if (fd < 0) {
 131                 if ((flags & LABEL_IGNORE_ENOENT) && errno == ENOENT)
 132                         return 0;
 133
 134                 return -errno;
 135         }
 136
 137         if (fstat(fd, &st) < 0)
 138                 return -errno;
 139
 140         if (selabel_lookup_raw(label_hnd, &fcon, path, st.st_mode) < 0) {
 141                 r = -errno;
 142
 143                 /* If there's no label to set, then exit without warning */
 144                 if (r == -ENOENT)
 145                         return 0;
 146
 147                 goto fail;
 148         }
 149
 150         xsprintf(procfs_path, "/proc/self/fd/%i", fd);
 151         if (setfilecon_raw(procfs_path, fcon) < 0) {
 152                 _cleanup_freecon_ char *oldcon = NULL;
 153
 154                 r = -errno;
 155
 156                 /* If the FS doesn't support labels, then exit without warning */
 157                 if (r == -EOPNOTSUPP)
 158                         return 0;
 159
 160                 /* It the FS is read-only and we were told to ignore failures caused by that, suppress error */
 161                 if (r == -EROFS && (flags & LABEL_IGNORE_EROFS))
 162                         return 0;
 163
 164                 /* If the old label is identical to the new one, suppress any kind of error */
 165                 if (getfilecon_raw(procfs_path, &oldcon) >= 0 && streq(fcon, oldcon))
 166                         return 0;
 167
 168                 goto fail;
 169         }
 170
 171         return 0;
 172
 173 fail:
 174         log_enforcing_errno(r, "Unable to fix SELinux security context of %s: %m", path);
 175         if (security_getenforce() == 1)
 176                 return r;
 177 #endif
 178
 179         return 0;
 180 }
 181
 182 int mac_selinux_apply(const char *path, const char *label) {
 183
 184 #if HAVE_SELINUX
 185         if (!mac_selinux_use())
 186                 return 0;
 187
 188         assert(path);
 189         assert(label);
 190
 191         if (setfilecon(path, label) < 0) {
 192                 log_enforcing("Failed to set SELinux security context %s on path %s: %m", label, path);
 193                 if (security_getenforce() > 0)
 194                         return -errno;
 195         }
 196 #endif
 197         return 0;
 198 }
 199
 200 int mac_selinux_get_create_label_from_exe(const char *exe, char **label) {
 201         int r = -EOPNOTSUPP;
 202
 203 #if HAVE_SELINUX
 204         _cleanup_freecon_ char *mycon = NULL, *fcon = NULL;
 205         security_class_t sclass;
 206
 207         assert(exe);
 208         assert(label);
 209
 210         if (!mac_selinux_use())
 211                 return -EOPNOTSUPP;
 212
 213         r = getcon_raw(&mycon);
 214         if (r < 0)
 215                 return -errno;
 216
 217         r = getfilecon_raw(exe, &fcon);
 218         if (r < 0)
 219                 return -errno;
 220
 221         sclass = string_to_security_class("process");
 222         r = security_compute_create_raw(mycon, fcon, sclass, label);
 223         if (r < 0)
 224                 return -errno;
 225 #endif
 226
 227         return r;
 228 }
 229
 230 int mac_selinux_get_our_label(char **label) {
 231         int r = -EOPNOTSUPP;
 232
 233         assert(label);
 234
 235 #if HAVE_SELINUX
 236         if (!mac_selinux_use())
 237                 return -EOPNOTSUPP;
 238
 239         r = getcon_raw(label);
 240         if (r < 0)
 241                 return -errno;
 242 #endif
 243
 244         return r;
 245 }
 246
 247 int mac_selinux_get_child_mls_label(int socket_fd, const char *exe, const char *exec_label, char **label) {
 248         int r = -EOPNOTSUPP;
 249
 250 #if HAVE_SELINUX
 251         _cleanup_freecon_ char *mycon = NULL, *peercon = NULL, *fcon = NULL;
 252         _cleanup_context_free_ context_t pcon = NULL, bcon = NULL;
 253         security_class_t sclass;
 254         const char *range = NULL;
 255
 256         assert(socket_fd >= 0);
 257         assert(exe);
 258         assert(label);
 259
 260         if (!mac_selinux_use())
 261                 return -EOPNOTSUPP;
 262
 263         r = getcon_raw(&mycon);
 264         if (r < 0)
 265                 return -errno;
 266
 267         r = getpeercon_raw(socket_fd, &peercon);
 268         if (r < 0)
 269                 return -errno;
 270
 271         if (!exec_label) {
 272                 /* If there is no context set for next exec let's use context
 273                    of target executable */
 274                 r = getfilecon_raw(exe, &fcon);
 275                 if (r < 0)
 276                         return -errno;
 277         }
 278
 279         bcon = context_new(mycon);
 280         if (!bcon)
 281                 return -ENOMEM;
 282
 283         pcon = context_new(peercon);
 284         if (!pcon)
 285                 return -ENOMEM;
 286
 287         range = context_range_get(pcon);
 288         if (!range)
 289                 return -errno;
 290
 291         r = context_range_set(bcon, range);
 292         if (r)
 293                 return -errno;
 294
 295         freecon(mycon);
 296         mycon = strdup(context_str(bcon));
 297         if (!mycon)
 298                 return -ENOMEM;
 299
 300         sclass = string_to_security_class("process");
 301         r = security_compute_create_raw(mycon, fcon, sclass, label);
 302         if (r < 0)
 303                 return -errno;
 304 #endif
 305
 306         return r;
 307 }
 308
 309 char* mac_selinux_free(char *label) {
 310
 311 #if HAVE_SELINUX
 312         if (!label)
 313                 return NULL;
 314
 315         if (!mac_selinux_use())
 316                 return NULL;
 317
 318
 319         freecon(label);
 320 #endif
 321
 322         return NULL;
 323 }
 324
 325 int mac_selinux_create_file_prepare(const char *path, mode_t mode) {
 326
 327 #if HAVE_SELINUX
 328         _cleanup_freecon_ char *filecon = NULL;
 329         int r;
 330
 331         assert(path);
 332
 333         if (!label_hnd)
 334                 return 0;
 335
 336         if (path_is_absolute(path))
 337                 r = selabel_lookup_raw(label_hnd, &filecon, path, mode);
 338         else {
 339                 _cleanup_free_ char *newpath = NULL;
 340
 341                 r = path_make_absolute_cwd(path, &newpath);
 342                 if (r < 0)
 343                         return r;
 344
 345                 r = selabel_lookup_raw(label_hnd, &filecon, newpath, mode);
 346         }
 347
 348         if (r < 0) {
 349                 /* No context specified by the policy? Proceed without setting it. */
 350                 if (errno == ENOENT)
 351                         return 0;
 352
 353                 log_enforcing("Failed to determine SELinux security context for %s: %m", path);
 354         } else {
 355                 if (setfscreatecon_raw(filecon) >= 0)
 356                         return 0; /* Success! */
 357
 358                 log_enforcing("Failed to set SELinux security context %s for %s: %m", filecon, path);
 359         }
 360
 361         if (security_getenforce() > 0)
 362                 return -errno;
 363
 364 #endif
 365         return 0;
 366 }
 367
 368 void mac_selinux_create_file_clear(void) {
 369
 370 #if HAVE_SELINUX
 371         PROTECT_ERRNO;
 372
 373         if (!mac_selinux_use())
 374                 return;
 375
 376         setfscreatecon_raw(NULL);
 377 #endif
 378 }
 379
 380 int mac_selinux_create_socket_prepare(const char *label) {
 381
 382 #if HAVE_SELINUX
 383         if (!mac_selinux_use())
 384                 return 0;
 385
 386         assert(label);
 387
 388         if (setsockcreatecon(label) < 0) {
 389                 log_enforcing("Failed to set SELinux security context %s for sockets: %m", label);
 390
 391                 if (security_getenforce() == 1)
 392                         return -errno;
 393         }
 394 #endif
 395
 396         return 0;
 397 }
 398
 399 void mac_selinux_create_socket_clear(void) {
 400
 401 #if HAVE_SELINUX
 402         PROTECT_ERRNO;
 403
 404         if (!mac_selinux_use())
 405                 return;
 406
 407         setsockcreatecon_raw(NULL);
 408 #endif
 409 }
 410
 411 int mac_selinux_bind(int fd, const struct sockaddr *addr, socklen_t addrlen) {
 412
 413         /* Binds a socket and label its file system object according to the SELinux policy */
 414
 415 #if HAVE_SELINUX
 416         _cleanup_freecon_ char *fcon = NULL;
 417         const struct sockaddr_un *un;
 418         bool context_changed = false;
 419         char *path;
 420         int r;
 421
 422         assert(fd >= 0);
 423         assert(addr);
 424         assert(addrlen >= sizeof(sa_family_t));
 425
 426         if (!label_hnd)
 427                 goto skipped;
 428
 429         /* Filter out non-local sockets */
 430         if (addr->sa_family != AF_UNIX)
 431                 goto skipped;
 432
 433         /* Filter out anonymous sockets */
 434         if (addrlen < offsetof(struct sockaddr_un, sun_path) + 1)
 435                 goto skipped;
 436
 437         /* Filter out abstract namespace sockets */
 438         un = (const struct sockaddr_un*) addr;
 439         if (un->sun_path[0] == 0)
 440                 goto skipped;
 441
 442         path = strndupa(un->sun_path, addrlen - offsetof(struct sockaddr_un, sun_path));
 443
 444         if (path_is_absolute(path))
 445                 r = selabel_lookup_raw(label_hnd, &fcon, path, S_IFSOCK);
 446         else {
 447                 _cleanup_free_ char *newpath = NULL;
 448
 449                 r = path_make_absolute_cwd(path, &newpath);
 450                 if (r < 0)
 451                         return r;
 452
 453                 r = selabel_lookup_raw(label_hnd, &fcon, newpath, S_IFSOCK);
 454         }
 455
 456         if (r < 0) {
 457                 /* No context specified by the policy? Proceed without setting it */
 458                 if (errno == ENOENT)
 459                         goto skipped;
 460
 461                 log_enforcing("Failed to determine SELinux security context for %s: %m", path);
 462                 if (security_getenforce() > 0)
 463                         return -errno;
 464
 465         } else {
 466                 if (setfscreatecon_raw(fcon) < 0) {
 467                         log_enforcing("Failed to set SELinux security context %s for %s: %m", fcon, path);
 468                         if (security_getenforce() > 0)
 469                                 return -errno;
 470                 } else
 471                         context_changed = true;
 472         }
 473
 474         r = bind(fd, addr, addrlen) < 0 ? -errno : 0;
 475
 476         if (context_changed)
 477                 setfscreatecon_raw(NULL);
 478
 479         return r;
 480
 481 skipped:
 482 #endif
 483         if (bind(fd, addr, addrlen) < 0)
 484                 return -errno;
 485
 486         return 0;
 487 }