src/basic/path-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <errno.h>
   4 #include <limits.h>
   5 #include <stdio.h>
   6 #include <stdlib.h>
   7 #include <unistd.h>
   8
   9 /* When we include libgen.h because we need dirname() we immediately
  10  * undefine basename() since libgen.h defines it as a macro to the
  11  * POSIX version which is really broken. We prefer GNU basename(). */
  12 #include <libgen.h>
  13 #undef basename
  14
  15 #include "alloc-util.h"
  16 #include "extract-word.h"
  17 #include "fs-util.h"
  18 #include "glob-util.h"
  19 #include "log.h"
  20 #include "macro.h"
  21 #include "nulstr-util.h"
  22 #include "parse-util.h"
  23 #include "path-util.h"
  24 #include "stat-util.h"
  25 #include "string-util.h"
  26 #include "strv.h"
  27 #include "time-util.h"
  28 #include "utf8.h"
  29
  30 bool path_is_absolute(const char *p) {
  31         return p[0] == '/';
  32 }
  33
  34 bool is_path(const char *p) {
  35         return !!strchr(p, '/');
  36 }
  37
  38 int path_split_and_make_absolute(const char *p, char ***ret) {
  39         char **l;
  40         int r;
  41
  42         assert(p);
  43         assert(ret);
  44
  45         l = strv_split(p, ":");
  46         if (!l)
  47                 return -ENOMEM;
  48
  49         r = path_strv_make_absolute_cwd(l);
  50         if (r < 0) {
  51                 strv_free(l);
  52                 return r;
  53         }
  54
  55         *ret = l;
  56         return r;
  57 }
  58
  59 char *path_make_absolute(const char *p, const char *prefix) {
  60         assert(p);
  61
  62         /* Makes every item in the list an absolute path by prepending
  63          * the prefix, if specified and necessary */
  64
  65         if (path_is_absolute(p) || isempty(prefix))
  66                 return strdup(p);
  67
  68         return path_join(prefix, p);
  69 }
  70
  71 int safe_getcwd(char **ret) {
  72         char *cwd;
  73
  74         cwd = get_current_dir_name();
  75         if (!cwd)
  76                 return negative_errno();
  77
  78         /* Let's make sure the directory is really absolute, to protect us from the logic behind
  79          * CVE-2018-1000001 */
  80         if (cwd[0] != '/') {
  81                 free(cwd);
  82                 return -ENOMEDIUM;
  83         }
  84
  85         *ret = cwd;
  86         return 0;
  87 }
  88
  89 int path_make_absolute_cwd(const char *p, char **ret) {
  90         char *c;
  91         int r;
  92
  93         assert(p);
  94         assert(ret);
  95
  96         /* Similar to path_make_absolute(), but prefixes with the
  97          * current working directory. */
  98
  99         if (path_is_absolute(p))
 100                 c = strdup(p);
 101         else {
 102                 _cleanup_free_ char *cwd = NULL;
 103
 104                 r = safe_getcwd(&cwd);
 105                 if (r < 0)
 106                         return r;
 107
 108                 c = path_join(cwd, p);
 109         }
 110         if (!c)
 111                 return -ENOMEM;
 112
 113         *ret = c;
 114         return 0;
 115 }
 116
 117 int path_make_relative(const char *from_dir, const char *to_path, char **_r) {
 118         char *f, *t, *r, *p;
 119         unsigned n_parents = 0;
 120
 121         assert(from_dir);
 122         assert(to_path);
 123         assert(_r);
 124
 125         /* Strips the common part, and adds ".." elements as necessary. */
 126
 127         if (!path_is_absolute(from_dir) || !path_is_absolute(to_path))
 128                 return -EINVAL;
 129
 130         f = strdupa(from_dir);
 131         t = strdupa(to_path);
 132
 133         path_simplify(f, true);
 134         path_simplify(t, true);
 135
 136         /* Skip the common part. */
 137         for (;;) {
 138                 size_t a, b;
 139
 140                 f += *f == '/';
 141                 t += *t == '/';
 142
 143                 if (!*f) {
 144                         if (!*t)
 145                                 /* from_dir equals to_path. */
 146                                 r = strdup(".");
 147                         else
 148                                 /* from_dir is a parent directory of to_path. */
 149                                 r = strdup(t);
 150                         if (!r)
 151                                 return -ENOMEM;
 152
 153                         *_r = r;
 154                         return 0;
 155                 }
 156
 157                 if (!*t)
 158                         break;
 159
 160                 a = strcspn(f, "/");
 161                 b = strcspn(t, "/");
 162
 163                 if (a != b || memcmp(f, t, a) != 0)
 164                         break;
 165
 166                 f += a;
 167                 t += b;
 168         }
 169
 170         /* If we're here, then "from_dir" has one or more elements that need to
 171          * be replaced with "..". */
 172
 173         /* Count the number of necessary ".." elements. */
 174         for (; *f;) {
 175                 size_t w;
 176
 177                 w = strcspn(f, "/");
 178
 179                 /* If this includes ".." we can't do a simple series of "..", refuse */
 180                 if (w == 2 && f[0] == '.' && f[1] == '.')
 181                         return -EINVAL;
 182
 183                 /* Count number of elements */
 184                 n_parents++;
 185
 186                 f += w;
 187                 f += *f == '/';
 188         }
 189
 190         r = new(char, n_parents * 3 + strlen(t) + 1);
 191         if (!r)
 192                 return -ENOMEM;
 193
 194         for (p = r; n_parents > 0; n_parents--)
 195                 p = mempcpy(p, "../", 3);
 196
 197         if (*t)
 198                 strcpy(p, t);
 199         else
 200                 /* Remove trailing slash */
 201                 *(--p) = 0;
 202
 203         *_r = r;
 204         return 0;
 205 }
 206
 207 char* path_startswith_strv(const char *p, char **set) {
 208         char **s, *t;
 209
 210         STRV_FOREACH(s, set) {
 211                 t = path_startswith(p, *s);
 212                 if (t)
 213                         return t;
 214         }
 215
 216         return NULL;
 217 }
 218
 219 int path_strv_make_absolute_cwd(char **l) {
 220         char **s;
 221         int r;
 222
 223         /* Goes through every item in the string list and makes it
 224          * absolute. This works in place and won't rollback any
 225          * changes on failure. */
 226
 227         STRV_FOREACH(s, l) {
 228                 char *t;
 229
 230                 r = path_make_absolute_cwd(*s, &t);
 231                 if (r < 0)
 232                         return r;
 233
 234                 path_simplify(t, false);
 235                 free_and_replace(*s, t);
 236         }
 237
 238         return 0;
 239 }
 240
 241 char **path_strv_resolve(char **l, const char *root) {
 242         char **s;
 243         unsigned k = 0;
 244         bool enomem = false;
 245         int r;
 246
 247         if (strv_isempty(l))
 248                 return l;
 249
 250         /* Goes through every item in the string list and canonicalize
 251          * the path. This works in place and won't rollback any
 252          * changes on failure. */
 253
 254         STRV_FOREACH(s, l) {
 255                 _cleanup_free_ char *orig = NULL;
 256                 char *t, *u;
 257
 258                 if (!path_is_absolute(*s)) {
 259                         free(*s);
 260                         continue;
 261                 }
 262
 263                 if (root) {
 264                         orig = *s;
 265                         t = path_join(root, orig);
 266                         if (!t) {
 267                                 enomem = true;
 268                                 continue;
 269                         }
 270                 } else
 271                         t = *s;
 272
 273                 r = chase_symlinks(t, root, 0, &u, NULL);
 274                 if (r == -ENOENT) {
 275                         if (root) {
 276                                 u = TAKE_PTR(orig);
 277                                 free(t);
 278                         } else
 279                                 u = t;
 280                 } else if (r < 0) {
 281                         free(t);
 282
 283                         if (r == -ENOMEM)
 284                                 enomem = true;
 285
 286                         continue;
 287                 } else if (root) {
 288                         char *x;
 289
 290                         free(t);
 291                         x = path_startswith(u, root);
 292                         if (x) {
 293                                 /* restore the slash if it was lost */
 294                                 if (!startswith(x, "/"))
 295                                         *(--x) = '/';
 296
 297                                 t = strdup(x);
 298                                 free(u);
 299                                 if (!t) {
 300                                         enomem = true;
 301                                         continue;
 302                                 }
 303                                 u = t;
 304                         } else {
 305                                 /* canonicalized path goes outside of
 306                                  * prefix, keep the original path instead */
 307                                 free_and_replace(u, orig);
 308                         }
 309                 } else
 310                         free(t);
 311
 312                 l[k++] = u;
 313         }
 314
 315         l[k] = NULL;
 316
 317         if (enomem)
 318                 return NULL;
 319
 320         return l;
 321 }
 322
 323 char **path_strv_resolve_uniq(char **l, const char *root) {
 324
 325         if (strv_isempty(l))
 326                 return l;
 327
 328         if (!path_strv_resolve(l, root))
 329                 return NULL;
 330
 331         return strv_uniq(l);
 332 }
 333
 334 char *path_simplify(char *path, bool kill_dots) {
 335         char *f, *t;
 336         bool slash = false, ignore_slash = false, absolute;
 337
 338         assert(path);
 339
 340         /* Removes redundant inner and trailing slashes. Also removes unnecessary dots
 341          * if kill_dots is true. Modifies the passed string in-place.
 342          *
 343          * ///foo//./bar/.   becomes /foo/./bar/.      (if kill_dots is false)
 344          * ///foo//./bar/.   becomes /foo/bar          (if kill_dots is true)
 345          * .//./foo//./bar/. becomes ././foo/./bar/.   (if kill_dots is false)
 346          * .//./foo//./bar/. becomes foo/bar           (if kill_dots is true)
 347          */
 348
 349         if (isempty(path))
 350                 return path;
 351
 352         absolute = path_is_absolute(path);
 353
 354         f = path;
 355         if (kill_dots && *f == '.' && IN_SET(f[1], 0, '/')) {
 356                 ignore_slash = true;
 357                 f++;
 358         }
 359
 360         for (t = path; *f; f++) {
 361
 362                 if (*f == '/') {
 363                         slash = true;
 364                         continue;
 365                 }
 366
 367                 if (slash) {
 368                         if (kill_dots && *f == '.' && IN_SET(f[1], 0, '/'))
 369                                 continue;
 370
 371                         slash = false;
 372                         if (ignore_slash)
 373                                 ignore_slash = false;
 374                         else
 375                                 *(t++) = '/';
 376                 }
 377
 378                 *(t++) = *f;
 379         }
 380
 381         /* Special rule, if we stripped everything, we either need a "/" (for the root directory)
 382          * or "." for the current directory */
 383         if (t == path) {
 384                 if (absolute)
 385                         *(t++) = '/';
 386                 else
 387                         *(t++) = '.';
 388         }
 389
 390         *t = 0;
 391         return path;
 392 }
 393
 394 int path_simplify_and_warn(
 395                 char *path,
 396                 unsigned flag,
 397                 const char *unit,
 398                 const char *filename,
 399                 unsigned line,
 400                 const char *lvalue) {
 401
 402         bool fatal = flag & PATH_CHECK_FATAL;
 403
 404         assert(!FLAGS_SET(flag, PATH_CHECK_ABSOLUTE | PATH_CHECK_RELATIVE));
 405
 406         if (!utf8_is_valid(path))
 407                 return log_syntax_invalid_utf8(unit, LOG_ERR, filename, line, path);
 408
 409         if (flag & (PATH_CHECK_ABSOLUTE | PATH_CHECK_RELATIVE)) {
 410                 bool absolute;
 411
 412                 absolute = path_is_absolute(path);
 413
 414                 if (!absolute && (flag & PATH_CHECK_ABSOLUTE))
 415                         return log_syntax(unit, LOG_ERR, filename, line, SYNTHETIC_ERRNO(EINVAL),
 416                                           "%s= path is not absolute%s: %s",
 417                                           lvalue, fatal ? "" : ", ignoring", path);
 418
 419                 if (absolute && (flag & PATH_CHECK_RELATIVE))
 420                         return log_syntax(unit, LOG_ERR, filename, line, SYNTHETIC_ERRNO(EINVAL),
 421                                           "%s= path is absolute%s: %s",
 422                                           lvalue, fatal ? "" : ", ignoring", path);
 423         }
 424
 425         path_simplify(path, true);
 426
 427         if (!path_is_valid(path))
 428                 return log_syntax(unit, LOG_ERR, filename, line, SYNTHETIC_ERRNO(EINVAL),
 429                                   "%s= path has invalid length (%zu bytes)%s.",
 430                                   lvalue, strlen(path), fatal ? "" : ", ignoring");
 431
 432         if (!path_is_normalized(path))
 433                 return log_syntax(unit, LOG_ERR, filename, line, SYNTHETIC_ERRNO(EINVAL),
 434                                   "%s= path is not normalized%s: %s",
 435                                   lvalue, fatal ? "" : ", ignoring", path);
 436
 437         return 0;
 438 }
 439
 440 char* path_startswith(const char *path, const char *prefix) {
 441         assert(path);
 442         assert(prefix);
 443
 444         /* Returns a pointer to the start of the first component after the parts matched by
 445          * the prefix, iff
 446          * - both paths are absolute or both paths are relative,
 447          * and
 448          * - each component in prefix in turn matches a component in path at the same position.
 449          * An empty string will be returned when the prefix and path are equivalent.
 450          *
 451          * Returns NULL otherwise.
 452          */
 453
 454         if ((path[0] == '/') != (prefix[0] == '/'))
 455                 return NULL;
 456
 457         for (;;) {
 458                 size_t a, b;
 459
 460                 path += strspn(path, "/");
 461                 prefix += strspn(prefix, "/");
 462
 463                 if (*prefix == 0)
 464                         return (char*) path;
 465
 466                 if (*path == 0)
 467                         return NULL;
 468
 469                 a = strcspn(path, "/");
 470                 b = strcspn(prefix, "/");
 471
 472                 if (a != b)
 473                         return NULL;
 474
 475                 if (memcmp(path, prefix, a) != 0)
 476                         return NULL;
 477
 478                 path += a;
 479                 prefix += b;
 480         }
 481 }
 482
 483 int path_compare(const char *a, const char *b) {
 484         int d;
 485
 486         assert(a);
 487         assert(b);
 488
 489         /* A relative path and an absolute path must not compare as equal.
 490          * Which one is sorted before the other does not really matter.
 491          * Here a relative path is ordered before an absolute path. */
 492         d = (a[0] == '/') - (b[0] == '/');
 493         if (d != 0)
 494                 return d;
 495
 496         for (;;) {
 497                 size_t j, k;
 498
 499                 a += strspn(a, "/");
 500                 b += strspn(b, "/");
 501
 502                 if (*a == 0 && *b == 0)
 503                         return 0;
 504
 505                 /* Order prefixes first: "/foo" before "/foo/bar" */
 506                 if (*a == 0)
 507                         return -1;
 508                 if (*b == 0)
 509                         return 1;
 510
 511                 j = strcspn(a, "/");
 512                 k = strcspn(b, "/");
 513
 514                 /* Alphabetical sort: "/foo/aaa" before "/foo/b" */
 515                 d = memcmp(a, b, MIN(j, k));
 516                 if (d != 0)
 517                         return (d > 0) - (d < 0); /* sign of d */
 518
 519                 /* Sort "/foo/a" before "/foo/aaa" */
 520                 d = (j > k) - (j < k);  /* sign of (j - k) */
 521                 if (d != 0)
 522                         return d;
 523
 524                 a += j;
 525                 b += k;
 526         }
 527 }
 528
 529 bool path_equal(const char *a, const char *b) {
 530         return path_compare(a, b) == 0;
 531 }
 532
 533 bool path_equal_or_files_same(const char *a, const char *b, int flags) {
 534         return path_equal(a, b) || files_same(a, b, flags) > 0;
 535 }
 536
 537 char* path_join_internal(const char *first, ...) {
 538         char *joined, *q;
 539         const char *p;
 540         va_list ap;
 541         bool slash;
 542         size_t sz;
 543
 544         /* Joins all listed strings until the sentinel and places a "/" between them unless the strings end/begin
 545          * already with one so that it is unnecessary. Note that slashes which are already duplicate won't be
 546          * removed. The string returned is hence always equal to or longer than the sum of the lengths of each
 547          * individual string.
 548          *
 549          * Note: any listed empty string is simply skipped. This can be useful for concatenating strings of which some
 550          * are optional.
 551          *
 552          * Examples:
 553          *
 554          * path_join("foo", "bar") → "foo/bar"
 555          * path_join("foo/", "bar") → "foo/bar"
 556          * path_join("", "foo", "", "bar", "") → "foo/bar" */
 557
 558         sz = strlen_ptr(first);
 559         va_start(ap, first);
 560         while ((p = va_arg(ap, char*)) != (const char*) -1)
 561                 if (!isempty(p))
 562                         sz += 1 + strlen(p);
 563         va_end(ap);
 564
 565         joined = new(char, sz + 1);
 566         if (!joined)
 567                 return NULL;
 568
 569         if (!isempty(first)) {
 570                 q = stpcpy(joined, first);
 571                 slash = endswith(first, "/");
 572         } else {
 573                 /* Skip empty items */
 574                 joined[0] = 0;
 575                 q = joined;
 576                 slash = true; /* no need to generate a slash anymore */
 577         }
 578
 579         va_start(ap, first);
 580         while ((p = va_arg(ap, char*)) != (const char*) -1) {
 581                 if (isempty(p))
 582                         continue;
 583
 584                 if (!slash && p[0] != '/')
 585                         *(q++) = '/';
 586
 587                 q = stpcpy(q, p);
 588                 slash = endswith(p, "/");
 589         }
 590         va_end(ap);
 591
 592         return joined;
 593 }
 594
 595 int find_binary(const char *name, char **ret) {
 596         int last_error, r;
 597         const char *p;
 598
 599         assert(name);
 600
 601         if (is_path(name)) {
 602                 if (access(name, X_OK) < 0)
 603                         return -errno;
 604
 605                 if (ret) {
 606                         r = path_make_absolute_cwd(name, ret);
 607                         if (r < 0)
 608                                 return r;
 609                 }
 610
 611                 return 0;
 612         }
 613
 614         /**
 615          * Plain getenv, not secure_getenv, because we want
 616          * to actually allow the user to pick the binary.
 617          */
 618         p = getenv("PATH");
 619         if (!p)
 620                 p = DEFAULT_PATH;
 621
 622         last_error = -ENOENT;
 623
 624         for (;;) {
 625                 _cleanup_free_ char *j = NULL, *element = NULL;
 626
 627                 r = extract_first_word(&p, &element, ":", EXTRACT_RELAX|EXTRACT_DONT_COALESCE_SEPARATORS);
 628                 if (r < 0)
 629                         return r;
 630                 if (r == 0)
 631                         break;
 632
 633                 if (!path_is_absolute(element))
 634                         continue;
 635
 636                 j = path_join(element, name);
 637                 if (!j)
 638                         return -ENOMEM;
 639
 640                 if (access(j, X_OK) >= 0) {
 641                         /* Found it! */
 642
 643                         if (ret)
 644                                 *ret = path_simplify(TAKE_PTR(j), false);
 645
 646                         return 0;
 647                 }
 648
 649                 /* PATH entries which we don't have access to are ignored, as per tradition. */
 650                 if (errno != EACCES)
 651                         last_error = -errno;
 652         }
 653
 654         return last_error;
 655 }
 656
 657 bool paths_check_timestamp(const char* const* paths, usec_t *timestamp, bool update) {
 658         bool changed = false;
 659         const char* const* i;
 660
 661         assert(timestamp);
 662
 663         if (!paths)
 664                 return false;
 665
 666         STRV_FOREACH(i, paths) {
 667                 struct stat stats;
 668                 usec_t u;
 669
 670                 if (stat(*i, &stats) < 0)
 671                         continue;
 672
 673                 u = timespec_load(&stats.st_mtim);
 674
 675                 /* first check */
 676                 if (*timestamp >= u)
 677                         continue;
 678
 679                 log_debug("timestamp of '%s' changed", *i);
 680
 681                 /* update timestamp */
 682                 if (update) {
 683                         *timestamp = u;
 684                         changed = true;
 685                 } else
 686                         return true;
 687         }
 688
 689         return changed;
 690 }
 691
 692 static int binary_is_good(const char *binary) {
 693         _cleanup_free_ char *p = NULL, *d = NULL;
 694         int r;
 695
 696         r = find_binary(binary, &p);
 697         if (r == -ENOENT)
 698                 return 0;
 699         if (r < 0)
 700                 return r;
 701
 702         /* An fsck that is linked to /bin/true is a non-existent
 703          * fsck */
 704
 705         r = readlink_malloc(p, &d);
 706         if (r == -EINVAL) /* not a symlink */
 707                 return 1;
 708         if (r < 0)
 709                 return r;
 710
 711         return !PATH_IN_SET(d, "true"
 712                                "/bin/true",
 713                                "/usr/bin/true",
 714                                "/dev/null");
 715 }
 716
 717 int fsck_exists(const char *fstype) {
 718         const char *checker;
 719
 720         assert(fstype);
 721
 722         if (streq(fstype, "auto"))
 723                 return -EINVAL;
 724
 725         checker = strjoina("fsck.", fstype);
 726         return binary_is_good(checker);
 727 }
 728
 729 int mkfs_exists(const char *fstype) {
 730         const char *mkfs;
 731
 732         assert(fstype);
 733
 734         if (streq(fstype, "auto"))
 735                 return -EINVAL;
 736
 737         mkfs = strjoina("mkfs.", fstype);
 738         return binary_is_good(mkfs);
 739 }
 740
 741 int parse_path_argument_and_warn(const char *path, bool suppress_root, char **arg) {
 742         char *p;
 743         int r;
 744
 745         /*
 746          * This function is intended to be used in command line
 747          * parsers, to handle paths that are passed in. It makes the
 748          * path absolute, and reduces it to NULL if omitted or
 749          * root (the latter optionally).
 750          *
 751          * NOTE THAT THIS WILL FREE THE PREVIOUS ARGUMENT POINTER ON
 752          * SUCCESS! Hence, do not pass in uninitialized pointers.
 753          */
 754
 755         if (isempty(path)) {
 756                 *arg = mfree(*arg);
 757                 return 0;
 758         }
 759
 760         r = path_make_absolute_cwd(path, &p);
 761         if (r < 0)
 762                 return log_error_errno(r, "Failed to parse path \"%s\" and make it absolute: %m", path);
 763
 764         path_simplify(p, false);
 765         if (suppress_root && empty_or_root(p))
 766                 p = mfree(p);
 767
 768         free_and_replace(*arg, p);
 769
 770         return 0;
 771 }
 772
 773 char* dirname_malloc(const char *path) {
 774         char *d, *dir, *dir2;
 775
 776         assert(path);
 777
 778         d = strdup(path);
 779         if (!d)
 780                 return NULL;
 781
 782         dir = dirname(d);
 783         assert(dir);
 784
 785         if (dir == d)
 786                 return d;
 787
 788         dir2 = strdup(dir);
 789         free(d);
 790
 791         return dir2;
 792 }
 793
 794 const char *last_path_component(const char *path) {
 795
 796         /* Finds the last component of the path, preserving the optional trailing slash that signifies a directory.
 797          *
 798          *    a/b/c → c
 799          *    a/b/c/ → c/
 800          *    x → x
 801          *    x/ → x/
 802          *    /y → y
 803          *    /y/ → y/
 804          *    / → /
 805          *    // → /
 806          *    /foo/a → a
 807          *    /foo/a/ → a/
 808          *
 809          *    Also, the empty string is mapped to itself.
 810          *
 811          * This is different than basename(), which returns "" when a trailing slash is present.
 812          */
 813
 814         unsigned l, k;
 815
 816         if (!path)
 817                 return NULL;
 818
 819         l = k = strlen(path);
 820         if (l == 0) /* special case — an empty string */
 821                 return path;
 822
 823         while (k > 0 && path[k-1] == '/')
 824                 k--;
 825
 826         if (k == 0) /* the root directory */
 827                 return path + l - 1;
 828
 829         while (k > 0 && path[k-1] != '/')
 830                 k--;
 831
 832         return path + k;
 833 }
 834
 835 int path_extract_filename(const char *p, char **ret) {
 836         _cleanup_free_ char *a = NULL;
 837         const char *c, *e = NULL, *q;
 838
 839         /* Extracts the filename part (i.e. right-most component) from a path, i.e. string that passes
 840          * filename_is_valid(). A wrapper around last_path_component(), but eats up trailing slashes. */
 841
 842         if (!p)
 843                 return -EINVAL;
 844
 845         c = last_path_component(p);
 846
 847         for (q = c; *q != 0; q++)
 848                 if (*q != '/')
 849                         e = q + 1;
 850
 851         if (!e) /* no valid character? */
 852                 return -EINVAL;
 853
 854         a = strndup(c, e - c);
 855         if (!a)
 856                 return -ENOMEM;
 857
 858         if (!filename_is_valid(a))
 859                 return -EINVAL;
 860
 861         *ret = TAKE_PTR(a);
 862
 863         return 0;
 864 }
 865
 866 bool filename_is_valid(const char *p) {
 867         const char *e;
 868
 869         if (isempty(p))
 870                 return false;
 871
 872         if (dot_or_dot_dot(p))
 873                 return false;
 874
 875         e = strchrnul(p, '/');
 876         if (*e != 0)
 877                 return false;
 878
 879         if (e - p > FILENAME_MAX) /* FILENAME_MAX is counted *without* the trailing NUL byte */
 880                 return false;
 881
 882         return true;
 883 }
 884
 885 bool path_is_valid(const char *p) {
 886
 887         if (isempty(p))
 888                 return false;
 889
 890         if (strlen(p) >= PATH_MAX) /* PATH_MAX is counted *with* the trailing NUL byte */
 891                 return false;
 892
 893         return true;
 894 }
 895
 896 bool path_is_normalized(const char *p) {
 897
 898         if (!path_is_valid(p))
 899                 return false;
 900
 901         if (dot_or_dot_dot(p))
 902                 return false;
 903
 904         if (startswith(p, "../") || endswith(p, "/..") || strstr(p, "/../"))
 905                 return false;
 906
 907         if (startswith(p, "./") || endswith(p, "/.") || strstr(p, "/./"))
 908                 return false;
 909
 910         if (strstr(p, "//"))
 911                 return false;
 912
 913         return true;
 914 }
 915
 916 char *file_in_same_dir(const char *path, const char *filename) {
 917         char *e, *ret;
 918         size_t k;
 919
 920         assert(path);
 921         assert(filename);
 922
 923         /* This removes the last component of path and appends
 924          * filename, unless the latter is absolute anyway or the
 925          * former isn't */
 926
 927         if (path_is_absolute(filename))
 928                 return strdup(filename);
 929
 930         e = strrchr(path, '/');
 931         if (!e)
 932                 return strdup(filename);
 933
 934         k = strlen(filename);
 935         ret = new(char, (e + 1 - path) + k + 1);
 936         if (!ret)
 937                 return NULL;
 938
 939         memcpy(mempcpy(ret, path, e + 1 - path), filename, k + 1);
 940         return ret;
 941 }
 942
 943 bool hidden_or_backup_file(const char *filename) {
 944         const char *p;
 945
 946         assert(filename);
 947
 948         if (filename[0] == '.' ||
 949             streq(filename, "lost+found") ||
 950             streq(filename, "aquota.user") ||
 951             streq(filename, "aquota.group") ||
 952             endswith(filename, "~"))
 953                 return true;
 954
 955         p = strrchr(filename, '.');
 956         if (!p)
 957                 return false;
 958
 959         /* Please, let's not add more entries to the list below. If external projects think it's a good idea to come up
 960          * with always new suffixes and that everybody else should just adjust to that, then it really should be on
 961          * them. Hence, in future, let's not add any more entries. Instead, let's ask those packages to instead adopt
 962          * one of the generic suffixes/prefixes for hidden files or backups, possibly augmented with an additional
 963          * string. Specifically: there's now:
 964          *
 965          *    The generic suffixes "~" and ".bak" for backup files
 966          *    The generic prefix "." for hidden files
 967          *
 968          * Thus, if a new package manager "foopkg" wants its own set of ".foopkg-new", ".foopkg-old", ".foopkg-dist"
 969          * or so registered, let's refuse that and ask them to use ".foopkg.new", ".foopkg.old" or ".foopkg~" instead.
 970          */
 971
 972         return STR_IN_SET(p + 1,
 973                           "rpmnew",
 974                           "rpmsave",
 975                           "rpmorig",
 976                           "dpkg-old",
 977                           "dpkg-new",
 978                           "dpkg-tmp",
 979                           "dpkg-dist",
 980                           "dpkg-bak",
 981                           "dpkg-backup",
 982                           "dpkg-remove",
 983                           "ucf-new",
 984                           "ucf-old",
 985                           "ucf-dist",
 986                           "swp",
 987                           "bak",
 988                           "old",
 989                           "new");
 990 }
 991
 992 bool is_device_path(const char *path) {
 993
 994         /* Returns true on paths that likely refer to a device, either by path in sysfs or to something in /dev */
 995
 996         return PATH_STARTSWITH_SET(path, "/dev/", "/sys/");
 997 }
 998
 999 bool valid_device_node_path(const char *path) {
1000
1001         /* Some superficial checks whether the specified path is a valid device node path, all without looking at the
1002          * actual device node. */
1003
1004         if (!PATH_STARTSWITH_SET(path, "/dev/", "/run/systemd/inaccessible/"))
1005                 return false;
1006
1007         if (endswith(path, "/")) /* can't be a device node if it ends in a slash */
1008                 return false;
1009
1010         return path_is_normalized(path);
1011 }
1012
1013 bool valid_device_allow_pattern(const char *path) {
1014         assert(path);
1015
1016         /* Like valid_device_node_path(), but also allows full-subsystem expressions, like DeviceAllow= and DeviceDeny=
1017          * accept it */
1018
1019         if (STARTSWITH_SET(path, "block-", "char-"))
1020                 return true;
1021
1022         return valid_device_node_path(path);
1023 }
1024
1025 int systemd_installation_has_version(const char *root, unsigned minimal_version) {
1026         const char *pattern;
1027         int r;
1028
1029         /* Try to guess if systemd installation is later than the specified version. This
1030          * is hacky and likely to yield false negatives, particularly if the installation
1031          * is non-standard. False positives should be relatively rare.
1032          */
1033
1034         NULSTR_FOREACH(pattern,
1035                        /* /lib works for systems without usr-merge, and for systems with a sane
1036                         * usr-merge, where /lib is a symlink to /usr/lib. /usr/lib is necessary
1037                         * for Gentoo which does a merge without making /lib a symlink.
1038                         */
1039                        "lib/systemd/libsystemd-shared-*.so\0"
1040                        "lib64/systemd/libsystemd-shared-*.so\0"
1041                        "usr/lib/systemd/libsystemd-shared-*.so\0"
1042                        "usr/lib64/systemd/libsystemd-shared-*.so\0") {
1043
1044                 _cleanup_strv_free_ char **names = NULL;
1045                 _cleanup_free_ char *path = NULL;
1046                 char *c, **name;
1047
1048                 path = path_join(root, pattern);
1049                 if (!path)
1050                         return -ENOMEM;
1051
1052                 r = glob_extend(&names, path, 0);
1053                 if (r == -ENOENT)
1054                         continue;
1055                 if (r < 0)
1056                         return r;
1057
1058                 assert_se(c = endswith(path, "*.so"));
1059                 *c = '\0'; /* truncate the glob part */
1060
1061                 STRV_FOREACH(name, names) {
1062                         /* This is most likely to run only once, hence let's not optimize anything. */
1063                         char *t, *t2;
1064                         unsigned version;
1065
1066                         t = startswith(*name, path);
1067                         if (!t)
1068                                 continue;
1069
1070                         t2 = endswith(t, ".so");
1071                         if (!t2)
1072                                 continue;
1073
1074                         t2[0] = '\0'; /* truncate the suffix */
1075
1076                         r = safe_atou(t, &version);
1077                         if (r < 0) {
1078                                 log_debug_errno(r, "Found libsystemd shared at \"%s.so\", but failed to parse version: %m", *name);
1079                                 continue;
1080                         }
1081
1082                         log_debug("Found libsystemd shared at \"%s.so\", version %u (%s).",
1083                                   *name, version,
1084                                   version >= minimal_version ? "OK" : "too old");
1085                         if (version >= minimal_version)
1086                                 return true;
1087                 }
1088         }
1089
1090         return false;
1091 }
1092
1093 bool dot_or_dot_dot(const char *path) {
1094         if (!path)
1095                 return false;
1096         if (path[0] != '.')
1097                 return false;
1098         if (path[1] == 0)
1099                 return true;
1100         if (path[1] != '.')
1101                 return false;
1102
1103         return path[2] == 0;
1104 }
1105
1106 bool empty_or_root(const char *root) {
1107
1108         /* For operations relative to some root directory, returns true if the specified root directory is redundant,
1109          * i.e. either / or NULL or the empty string or any equivalent. */
1110
1111         if (!root)
1112                 return true;
1113
1114         return root[strspn(root, "/")] == 0;
1115 }
1116
1117 bool path_strv_contains(char **l, const char *path) {
1118         char **i;
1119
1120         STRV_FOREACH(i, l)
1121                 if (path_equal(*i, path))
1122                         return true;
1123
1124         return false;
1125 }
1126
1127 bool prefixed_path_strv_contains(char **l, const char *path) {
1128         char **i, *j;
1129
1130         STRV_FOREACH(i, l) {
1131                 j = *i;
1132                 if (*j == '-')
1133                         j++;
1134                 if (*j == '+')
1135                         j++;
1136                 if (path_equal(j, path))
1137                         return true;
1138         }
1139
1140         return false;
1141 }