src/basic/fs-util.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright 2010 Lennart Poettering
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include <dirent.h>
  21 #include <errno.h>
  22 #include <stddef.h>
  23 #include <stdio.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <sys/stat.h>
  27 #include <time.h>
  28 #include <unistd.h>
  29
  30 #include "alloc-util.h"
  31 #include "dirent-util.h"
  32 #include "fd-util.h"
  33 #include "fileio.h"
  34 #include "fs-util.h"
  35 #include "log.h"
  36 #include "macro.h"
  37 #include "missing.h"
  38 #include "mkdir.h"
  39 #include "parse-util.h"
  40 #include "path-util.h"
  41 #include "stat-util.h"
  42 #include "stdio-util.h"
  43 #include "string-util.h"
  44 #include "strv.h"
  45 #include "time-util.h"
  46 #include "user-util.h"
  47 #include "util.h"
  48
  49 int unlink_noerrno(const char *path) {
  50         PROTECT_ERRNO;
  51         int r;
  52
  53         r = unlink(path);
  54         if (r < 0)
  55                 return -errno;
  56
  57         return 0;
  58 }
  59
  60 int rmdir_parents(const char *path, const char *stop) {
  61         size_t l;
  62         int r = 0;
  63
  64         assert(path);
  65         assert(stop);
  66
  67         l = strlen(path);
  68
  69         /* Skip trailing slashes */
  70         while (l > 0 && path[l-1] == '/')
  71                 l--;
  72
  73         while (l > 0) {
  74                 char *t;
  75
  76                 /* Skip last component */
  77                 while (l > 0 && path[l-1] != '/')
  78                         l--;
  79
  80                 /* Skip trailing slashes */
  81                 while (l > 0 && path[l-1] == '/')
  82                         l--;
  83
  84                 if (l <= 0)
  85                         break;
  86
  87                 t = strndup(path, l);
  88                 if (!t)
  89                         return -ENOMEM;
  90
  91                 if (path_startswith(stop, t)) {
  92                         free(t);
  93                         return 0;
  94                 }
  95
  96                 r = rmdir(t);
  97                 free(t);
  98
  99                 if (r < 0)
 100                         if (errno != ENOENT)
 101                                 return -errno;
 102         }
 103
 104         return 0;
 105 }
 106
 107
 108 int rename_noreplace(int olddirfd, const char *oldpath, int newdirfd, const char *newpath) {
 109         struct stat buf;
 110         int ret;
 111
 112         ret = renameat2(olddirfd, oldpath, newdirfd, newpath, RENAME_NOREPLACE);
 113         if (ret >= 0)
 114                 return 0;
 115
 116         /* renameat2() exists since Linux 3.15, btrfs added support for it later.
 117          * If it is not implemented, fallback to another method. */
 118         if (!IN_SET(errno, EINVAL, ENOSYS))
 119                 return -errno;
 120
 121         /* The link()/unlink() fallback does not work on directories. But
 122          * renameat() without RENAME_NOREPLACE gives the same semantics on
 123          * directories, except when newpath is an *empty* directory. This is
 124          * good enough. */
 125         ret = fstatat(olddirfd, oldpath, &buf, AT_SYMLINK_NOFOLLOW);
 126         if (ret >= 0 && S_ISDIR(buf.st_mode)) {
 127                 ret = renameat(olddirfd, oldpath, newdirfd, newpath);
 128                 return ret >= 0 ? 0 : -errno;
 129         }
 130
 131         /* If it is not a directory, use the link()/unlink() fallback. */
 132         ret = linkat(olddirfd, oldpath, newdirfd, newpath, 0);
 133         if (ret < 0)
 134                 return -errno;
 135
 136         ret = unlinkat(olddirfd, oldpath, 0);
 137         if (ret < 0) {
 138                 /* backup errno before the following unlinkat() alters it */
 139                 ret = errno;
 140                 (void) unlinkat(newdirfd, newpath, 0);
 141                 errno = ret;
 142                 return -errno;
 143         }
 144
 145         return 0;
 146 }
 147
 148 int readlinkat_malloc(int fd, const char *p, char **ret) {
 149         size_t l = 100;
 150         int r;
 151
 152         assert(p);
 153         assert(ret);
 154
 155         for (;;) {
 156                 char *c;
 157                 ssize_t n;
 158
 159                 c = new(char, l);
 160                 if (!c)
 161                         return -ENOMEM;
 162
 163                 n = readlinkat(fd, p, c, l-1);
 164                 if (n < 0) {
 165                         r = -errno;
 166                         free(c);
 167                         return r;
 168                 }
 169
 170                 if ((size_t) n < l-1) {
 171                         c[n] = 0;
 172                         *ret = c;
 173                         return 0;
 174                 }
 175
 176                 free(c);
 177                 l *= 2;
 178         }
 179 }
 180
 181 int readlink_malloc(const char *p, char **ret) {
 182         return readlinkat_malloc(AT_FDCWD, p, ret);
 183 }
 184
 185 int readlink_value(const char *p, char **ret) {
 186         _cleanup_free_ char *link = NULL;
 187         char *value;
 188         int r;
 189
 190         r = readlink_malloc(p, &link);
 191         if (r < 0)
 192                 return r;
 193
 194         value = basename(link);
 195         if (!value)
 196                 return -ENOENT;
 197
 198         value = strdup(value);
 199         if (!value)
 200                 return -ENOMEM;
 201
 202         *ret = value;
 203
 204         return 0;
 205 }
 206
 207 int readlink_and_make_absolute(const char *p, char **r) {
 208         _cleanup_free_ char *target = NULL;
 209         char *k;
 210         int j;
 211
 212         assert(p);
 213         assert(r);
 214
 215         j = readlink_malloc(p, &target);
 216         if (j < 0)
 217                 return j;
 218
 219         k = file_in_same_dir(p, target);
 220         if (!k)
 221                 return -ENOMEM;
 222
 223         *r = k;
 224         return 0;
 225 }
 226
 227 int readlink_and_canonicalize(const char *p, char **r) {
 228         char *t, *s;
 229         int j;
 230
 231         assert(p);
 232         assert(r);
 233
 234         j = readlink_and_make_absolute(p, &t);
 235         if (j < 0)
 236                 return j;
 237
 238         s = canonicalize_file_name(t);
 239         if (s) {
 240                 free(t);
 241                 *r = s;
 242         } else
 243                 *r = t;
 244
 245         path_kill_slashes(*r);
 246
 247         return 0;
 248 }
 249
 250 int readlink_and_make_absolute_root(const char *root, const char *path, char **ret) {
 251         _cleanup_free_ char *target = NULL, *t = NULL;
 252         const char *full;
 253         int r;
 254
 255         full = prefix_roota(root, path);
 256         r = readlink_malloc(full, &target);
 257         if (r < 0)
 258                 return r;
 259
 260         t = file_in_same_dir(path, target);
 261         if (!t)
 262                 return -ENOMEM;
 263
 264         *ret = t;
 265         t = NULL;
 266
 267         return 0;
 268 }
 269
 270 int chmod_and_chown(const char *path, mode_t mode, uid_t uid, gid_t gid) {
 271         assert(path);
 272
 273         /* Under the assumption that we are running privileged we
 274          * first change the access mode and only then hand out
 275          * ownership to avoid a window where access is too open. */
 276
 277         if (mode != MODE_INVALID)
 278                 if (chmod(path, mode) < 0)
 279                         return -errno;
 280
 281         if (uid != UID_INVALID || gid != GID_INVALID)
 282                 if (chown(path, uid, gid) < 0)
 283                         return -errno;
 284
 285         return 0;
 286 }
 287
 288 int fchmod_umask(int fd, mode_t m) {
 289         mode_t u;
 290         int r;
 291
 292         u = umask(0777);
 293         r = fchmod(fd, m & (~u)) < 0 ? -errno : 0;
 294         umask(u);
 295
 296         return r;
 297 }
 298
 299 int fd_warn_permissions(const char *path, int fd) {
 300         struct stat st;
 301
 302         if (fstat(fd, &st) < 0)
 303                 return -errno;
 304
 305         if (st.st_mode & 0111)
 306                 log_warning("Configuration file %s is marked executable. Please remove executable permission bits. Proceeding anyway.", path);
 307
 308         if (st.st_mode & 0002)
 309                 log_warning("Configuration file %s is marked world-writable. Please remove world writability permission bits. Proceeding anyway.", path);
 310
 311         if (getpid() == 1 && (st.st_mode & 0044) != 0044)
 312                 log_warning("Configuration file %s is marked world-inaccessible. This has no effect as configuration data is accessible via APIs without restrictions. Proceeding anyway.", path);
 313
 314         return 0;
 315 }
 316
 317 int touch_file(const char *path, bool parents, usec_t stamp, uid_t uid, gid_t gid, mode_t mode) {
 318         _cleanup_close_ int fd;
 319         int r;
 320
 321         assert(path);
 322
 323         if (parents)
 324                 mkdir_parents(path, 0755);
 325
 326         fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY,
 327                         (mode == 0 || mode == MODE_INVALID) ? 0644 : mode);
 328         if (fd < 0)
 329                 return -errno;
 330
 331         if (mode != MODE_INVALID) {
 332                 r = fchmod(fd, mode);
 333                 if (r < 0)
 334                         return -errno;
 335         }
 336
 337         if (uid != UID_INVALID || gid != GID_INVALID) {
 338                 r = fchown(fd, uid, gid);
 339                 if (r < 0)
 340                         return -errno;
 341         }
 342
 343         if (stamp != USEC_INFINITY) {
 344                 struct timespec ts[2];
 345
 346                 timespec_store(&ts[0], stamp);
 347                 ts[1] = ts[0];
 348                 r = futimens(fd, ts);
 349         } else
 350                 r = futimens(fd, NULL);
 351         if (r < 0)
 352                 return -errno;
 353
 354         return 0;
 355 }
 356
 357 int touch(const char *path) {
 358         return touch_file(path, false, USEC_INFINITY, UID_INVALID, GID_INVALID, MODE_INVALID);
 359 }
 360
 361 int symlink_idempotent(const char *from, const char *to) {
 362         _cleanup_free_ char *p = NULL;
 363         int r;
 364
 365         assert(from);
 366         assert(to);
 367
 368         if (symlink(from, to) < 0) {
 369                 if (errno != EEXIST)
 370                         return -errno;
 371
 372                 r = readlink_malloc(to, &p);
 373                 if (r < 0)
 374                         return r;
 375
 376                 if (!streq(p, from))
 377                         return -EINVAL;
 378         }
 379
 380         return 0;
 381 }
 382
 383 int symlink_atomic(const char *from, const char *to) {
 384         _cleanup_free_ char *t = NULL;
 385         int r;
 386
 387         assert(from);
 388         assert(to);
 389
 390         r = tempfn_random(to, NULL, &t);
 391         if (r < 0)
 392                 return r;
 393
 394         if (symlink(from, t) < 0)
 395                 return -errno;
 396
 397         if (rename(t, to) < 0) {
 398                 unlink_noerrno(t);
 399                 return -errno;
 400         }
 401
 402         return 0;
 403 }
 404
 405 int mknod_atomic(const char *path, mode_t mode, dev_t dev) {
 406         _cleanup_free_ char *t = NULL;
 407         int r;
 408
 409         assert(path);
 410
 411         r = tempfn_random(path, NULL, &t);
 412         if (r < 0)
 413                 return r;
 414
 415         if (mknod(t, mode, dev) < 0)
 416                 return -errno;
 417
 418         if (rename(t, path) < 0) {
 419                 unlink_noerrno(t);
 420                 return -errno;
 421         }
 422
 423         return 0;
 424 }
 425
 426 int mkfifo_atomic(const char *path, mode_t mode) {
 427         _cleanup_free_ char *t = NULL;
 428         int r;
 429
 430         assert(path);
 431
 432         r = tempfn_random(path, NULL, &t);
 433         if (r < 0)
 434                 return r;
 435
 436         if (mkfifo(t, mode) < 0)
 437                 return -errno;
 438
 439         if (rename(t, path) < 0) {
 440                 unlink_noerrno(t);
 441                 return -errno;
 442         }
 443
 444         return 0;
 445 }
 446
 447 int get_files_in_directory(const char *path, char ***list) {
 448         _cleanup_closedir_ DIR *d = NULL;
 449         size_t bufsize = 0, n = 0;
 450         _cleanup_strv_free_ char **l = NULL;
 451
 452         assert(path);
 453
 454         /* Returns all files in a directory in *list, and the number
 455          * of files as return value. If list is NULL returns only the
 456          * number. */
 457
 458         d = opendir(path);
 459         if (!d)
 460                 return -errno;
 461
 462         for (;;) {
 463                 struct dirent *de;
 464
 465                 errno = 0;
 466                 de = readdir(d);
 467                 if (!de && errno > 0)
 468                         return -errno;
 469                 if (!de)
 470                         break;
 471
 472                 dirent_ensure_type(d, de);
 473
 474                 if (!dirent_is_file(de))
 475                         continue;
 476
 477                 if (list) {
 478                         /* one extra slot is needed for the terminating NULL */
 479                         if (!GREEDY_REALLOC(l, bufsize, n + 2))
 480                                 return -ENOMEM;
 481
 482                         l[n] = strdup(de->d_name);
 483                         if (!l[n])
 484                                 return -ENOMEM;
 485
 486                         l[++n] = NULL;
 487                 } else
 488                         n++;
 489         }
 490
 491         if (list) {
 492                 *list = l;
 493                 l = NULL; /* avoid freeing */
 494         }
 495
 496         return n;
 497 }
 498
 499 static int getenv_tmp_dir(const char **ret_path) {
 500         const char *n;
 501         int r, ret = 0;
 502
 503         assert(ret_path);
 504
 505         /* We use the same order of environment variables python uses in tempfile.gettempdir():
 506          * https://docs.python.org/3/library/tempfile.html#tempfile.gettempdir */
 507         FOREACH_STRING(n, "TMPDIR", "TEMP", "TMP") {
 508                 const char *e;
 509
 510                 e = secure_getenv(n);
 511                 if (!e)
 512                         continue;
 513                 if (!path_is_absolute(e)) {
 514                         r = -ENOTDIR;
 515                         goto next;
 516                 }
 517                 if (!path_is_safe(e)) {
 518                         r = -EPERM;
 519                         goto next;
 520                 }
 521
 522                 r = is_dir(e, true);
 523                 if (r < 0)
 524                         goto next;
 525                 if (r == 0) {
 526                         r = -ENOTDIR;
 527                         goto next;
 528                 }
 529
 530                 *ret_path = e;
 531                 return 1;
 532
 533         next:
 534                 /* Remember first error, to make this more debuggable */
 535                 if (ret >= 0)
 536                         ret = r;
 537         }
 538
 539         if (ret < 0)
 540                 return ret;
 541
 542         *ret_path = NULL;
 543         return ret;
 544 }
 545
 546 static int tmp_dir_internal(const char *def, const char **ret) {
 547         const char *e;
 548         int r, k;
 549
 550         assert(def);
 551         assert(ret);
 552
 553         r = getenv_tmp_dir(&e);
 554         if (r > 0) {
 555                 *ret = e;
 556                 return 0;
 557         }
 558
 559         k = is_dir(def, true);
 560         if (k == 0)
 561                 k = -ENOTDIR;
 562         if (k < 0)
 563                 return r < 0 ? r : k;
 564
 565         *ret = def;
 566         return 0;
 567 }
 568
 569 int var_tmp_dir(const char **ret) {
 570
 571         /* Returns the location for "larger" temporary files, that is backed by physical storage if available, and thus
 572          * even might survive a boot: /var/tmp. If $TMPDIR (or related environment variables) are set, its value is
 573          * returned preferably however. Note that both this function and tmp_dir() below are affected by $TMPDIR,
 574          * making it a variable that overrides all temporary file storage locations. */
 575
 576         return tmp_dir_internal("/var/tmp", ret);
 577 }
 578
 579 int tmp_dir(const char **ret) {
 580
 581         /* Similar to var_tmp_dir() above, but returns the location for "smaller" temporary files, which is usually
 582          * backed by an in-memory file system: /tmp. */
 583
 584         return tmp_dir_internal("/tmp", ret);
 585 }
 586
 587 int inotify_add_watch_fd(int fd, int what, uint32_t mask) {
 588         char path[strlen("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1];
 589         int r;
 590
 591         /* This is like inotify_add_watch(), except that the file to watch is not referenced by a path, but by an fd */
 592         xsprintf(path, "/proc/self/fd/%i", what);
 593
 594         r = inotify_add_watch(fd, path, mask);
 595         if (r < 0)
 596                 return -errno;
 597
 598         return r;
 599 }
 600
 601 int chase_symlinks(const char *path, const char *_root, char **ret) {
 602         _cleanup_free_ char *buffer = NULL, *done = NULL, *root = NULL;
 603         _cleanup_close_ int fd = -1;
 604         unsigned max_follow = 32; /* how many symlinks to follow before giving up and returning ELOOP */
 605         char *todo;
 606         int r;
 607
 608         assert(path);
 609
 610         /* This is a lot like canonicalize_file_name(), but takes an additional "root" parameter, that allows following
 611          * symlinks relative to a root directory, instead of the root of the host.
 612          *
 613          * Note that "root" matters only if we encounter an absolute symlink, it's unused otherwise. Most importantly
 614          * this means the path parameter passed in is not prefixed by it.
 615          *
 616          * Algorithmically this operates on two path buffers: "done" are the components of the path we already
 617          * processed and resolved symlinks, "." and ".." of. "todo" are the components of the path we still need to
 618          * process. On each iteration, we move one component from "todo" to "done", processing it's special meaning
 619          * each time. The "todo" path always starts with at least one slash, the "done" path always ends in no
 620          * slash. We always keep an O_PATH fd to the component we are currently processing, thus keeping lookup races
 621          * at a minimum. */
 622
 623         r = path_make_absolute_cwd(path, &buffer);
 624         if (r < 0)
 625                 return r;
 626
 627         if (_root) {
 628                 r = path_make_absolute_cwd(_root, &root);
 629                 if (r < 0)
 630                         return r;
 631         }
 632
 633         fd = open("/", O_CLOEXEC|O_NOFOLLOW|O_PATH);
 634         if (fd < 0)
 635                 return -errno;
 636
 637         todo = buffer;
 638         for (;;) {
 639                 _cleanup_free_ char *first = NULL;
 640                 _cleanup_close_ int child = -1;
 641                 struct stat st;
 642                 size_t n, m;
 643
 644                 /* Determine length of first component in the path */
 645                 n = strspn(todo, "/");                  /* The slashes */
 646                 m = n + strcspn(todo + n, "/");         /* The entire length of the component */
 647
 648                 /* Extract the first component. */
 649                 first = strndup(todo, m);
 650                 if (!first)
 651                         return -ENOMEM;
 652
 653                 todo += m;
 654
 655                 /* Just a single slash? Then we reached the end. */
 656                 if (isempty(first) || path_equal(first, "/"))
 657                         break;
 658
 659                 /* Just a dot? Then let's eat this up. */
 660                 if (path_equal(first, "/."))
 661                         continue;
 662
 663                 /* Two dots? Then chop off the last bit of what we already found out. */
 664                 if (path_equal(first, "/..")) {
 665                         _cleanup_free_ char *parent = NULL;
 666                         int fd_parent = -1;
 667
 668                         if (isempty(done) || path_equal(done, "/"))
 669                                 return -EINVAL;
 670
 671                         parent = dirname_malloc(done);
 672                         if (!parent)
 673                                 return -ENOMEM;
 674
 675                         /* Don't allow this to leave the root dir */
 676                         if (root &&
 677                             path_startswith(done, root) &&
 678                             !path_startswith(parent, root))
 679                                 return -EINVAL;
 680
 681                         free_and_replace(done, parent);
 682
 683                         fd_parent = openat(fd, "..", O_CLOEXEC|O_NOFOLLOW|O_PATH);
 684                         if (fd_parent < 0)
 685                                 return -errno;
 686
 687                         safe_close(fd);
 688                         fd = fd_parent;
 689
 690                         continue;
 691                 }
 692
 693                 /* Otherwise let's see what this is. */
 694                 child = openat(fd, first + n, O_CLOEXEC|O_NOFOLLOW|O_PATH);
 695                 if (child < 0)
 696                         return -errno;
 697
 698                 if (fstat(child, &st) < 0)
 699                         return -errno;
 700
 701                 if (S_ISLNK(st.st_mode)) {
 702                         _cleanup_free_ char *destination = NULL;
 703
 704                         /* This is a symlink, in this case read the destination. But let's make sure we don't follow
 705                          * symlinks without bounds. */
 706                         if (--max_follow <= 0)
 707                                 return -ELOOP;
 708
 709                         r = readlinkat_malloc(fd, first + n, &destination);
 710                         if (r < 0)
 711                                 return r;
 712                         if (isempty(destination))
 713                                 return -EINVAL;
 714
 715                         if (path_is_absolute(destination)) {
 716
 717                                 /* An absolute destination. Start the loop from the beginning, but use the root
 718                                  * directory as base. */
 719
 720                                 safe_close(fd);
 721                                 fd = open(root ?: "/", O_CLOEXEC|O_NOFOLLOW|O_PATH);
 722                                 if (fd < 0)
 723                                         return -errno;
 724
 725                                 free_and_replace(buffer, destination);
 726
 727                                 todo = buffer;
 728                                 free(done);
 729
 730                                 /* Note that we do not revalidate the root, we take it as is. */
 731                                 if (isempty(root))
 732                                         done = NULL;
 733                                 else {
 734                                         done = strdup(root);
 735                                         if (!done)
 736                                                 return -ENOMEM;
 737                                 }
 738
 739                         } else {
 740                                 char *joined;
 741
 742                                 /* A relative destination. If so, this is what we'll prefix what's left to do with what
 743                                  * we just read, and start the loop again, but remain in the current directory. */
 744
 745                                 joined = strjoin("/", destination, todo, NULL);
 746                                 if (!joined)
 747                                         return -ENOMEM;
 748
 749                                 free(buffer);
 750                                 todo = buffer = joined;
 751                         }
 752
 753                         continue;
 754                 }
 755
 756                 /* If this is not a symlink, then let's just add the name we read to what we already verified. */
 757                 if (!done) {
 758                         done = first;
 759                         first = NULL;
 760                 } else {
 761                         if (!strextend(&done, first, NULL))
 762                                 return -ENOMEM;
 763                 }
 764
 765                 /* And iterate again, but go one directory further down. */
 766                 safe_close(fd);
 767                 fd = child;
 768                 child = -1;
 769         }
 770
 771         if (!done) {
 772                 /* Special case, turn the empty string into "/", to indicate the root directory. */
 773                 done = strdup("/");
 774                 if (!done)
 775                         return -ENOMEM;
 776         }
 777
 778         *ret = done;
 779         done = NULL;
 780
 781         return 0;
 782 }