src/basic/unit-name.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include <errno.h>
   4 #include <stddef.h>
   5 #include <stdint.h>
   6 #include <stdlib.h>
   7
   8 #include "sd-id128.h"
   9
  10 #include "alloc-util.h"
  11 #include "glob-util.h"
  12 #include "hexdecoct.h"
  13 #include "memory-util.h"
  14 #include "path-util.h"
  15 #include "random-util.h"
  16 #include "sparse-endian.h"
  17 #include "special.h"
  18 #include "stdio-util.h"
  19 #include "string-util.h"
  20 #include "strv.h"
  21 #include "unit-name.h"
  22
  23 /* Characters valid in a unit name. */
  24 #define VALID_CHARS                             \
  25         DIGITS                                  \
  26         LETTERS                                 \
  27         ":-_.\\"
  28
  29 /* The same, but also permits the single @ character that may appear */
  30 #define VALID_CHARS_WITH_AT                     \
  31         "@"                                     \
  32         VALID_CHARS
  33
  34 /* All chars valid in a unit name glob */
  35 #define VALID_CHARS_GLOB                        \
  36         VALID_CHARS_WITH_AT                     \
  37         "[]!-*?"
  38
  39 #define LONG_UNIT_NAME_HASH_KEY SD_ID128_MAKE(ec,f2,37,fb,58,32,4a,32,84,9f,06,9b,0d,21,eb,9a)
  40 #define UNIT_NAME_HASH_LENGTH_CHARS 16
  41
  42 bool unit_name_is_valid(const char *n, UnitNameFlags flags) {
  43         const char *e, *i, *at;
  44
  45         assert((flags & ~(UNIT_NAME_PLAIN|UNIT_NAME_INSTANCE|UNIT_NAME_TEMPLATE)) == 0);
  46
  47         if (_unlikely_(flags == 0))
  48                 return false;
  49
  50         if (isempty(n))
  51                 return false;
  52
  53         if (strlen(n) >= UNIT_NAME_MAX)
  54                 return false;
  55
  56         e = strrchr(n, '.');
  57         if (!e || e == n)
  58                 return false;
  59
  60         if (unit_type_from_string(e + 1) < 0)
  61                 return false;
  62
  63         for (i = n, at = NULL; i < e; i++) {
  64
  65                 if (*i == '@' && !at)
  66                         at = i;
  67
  68                 if (!strchr(VALID_CHARS_WITH_AT, *i))
  69                         return false;
  70         }
  71
  72         if (at == n)
  73                 return false;
  74
  75         if (flags & UNIT_NAME_PLAIN)
  76                 if (!at)
  77                         return true;
  78
  79         if (flags & UNIT_NAME_INSTANCE)
  80                 if (at && e > at + 1)
  81                         return true;
  82
  83         if (flags & UNIT_NAME_TEMPLATE)
  84                 if (at && e == at + 1)
  85                         return true;
  86
  87         return false;
  88 }
  89
  90 bool unit_prefix_is_valid(const char *p) {
  91
  92         /* We don't allow additional @ in the prefix string */
  93
  94         if (isempty(p))
  95                 return false;
  96
  97         return in_charset(p, VALID_CHARS);
  98 }
  99
 100 bool unit_instance_is_valid(const char *i) {
 101
 102         /* The max length depends on the length of the string, so we
 103          * don't really check this here. */
 104
 105         if (isempty(i))
 106                 return false;
 107
 108         /* We allow additional @ in the instance string, we do not
 109          * allow them in the prefix! */
 110
 111         return in_charset(i, "@" VALID_CHARS);
 112 }
 113
 114 bool unit_suffix_is_valid(const char *s) {
 115         if (isempty(s))
 116                 return false;
 117
 118         if (s[0] != '.')
 119                 return false;
 120
 121         if (unit_type_from_string(s + 1) < 0)
 122                 return false;
 123
 124         return true;
 125 }
 126
 127 int unit_name_to_prefix(const char *n, char **ret) {
 128         const char *p;
 129         char *s;
 130
 131         assert(n);
 132         assert(ret);
 133
 134         if (!unit_name_is_valid(n, UNIT_NAME_ANY))
 135                 return -EINVAL;
 136
 137         p = strchr(n, '@');
 138         if (!p)
 139                 p = strrchr(n, '.');
 140
 141         assert_se(p);
 142
 143         s = strndup(n, p - n);
 144         if (!s)
 145                 return -ENOMEM;
 146
 147         *ret = s;
 148         return 0;
 149 }
 150
 151 UnitNameFlags unit_name_to_instance(const char *n, char **ret) {
 152         const char *p, *d;
 153
 154         assert(n);
 155
 156         if (!unit_name_is_valid(n, UNIT_NAME_ANY))
 157                 return -EINVAL;
 158
 159         /* Everything past the first @ and before the last . is the instance */
 160         p = strchr(n, '@');
 161         if (!p) {
 162                 if (ret)
 163                         *ret = NULL;
 164                 return UNIT_NAME_PLAIN;
 165         }
 166
 167         p++;
 168
 169         d = strrchr(p, '.');
 170         if (!d)
 171                 return -EINVAL;
 172
 173         if (ret) {
 174                 char *i = strndup(p, d-p);
 175                 if (!i)
 176                         return -ENOMEM;
 177
 178                 *ret = i;
 179         }
 180         return d > p ? UNIT_NAME_INSTANCE : UNIT_NAME_TEMPLATE;
 181 }
 182
 183 int unit_name_to_prefix_and_instance(const char *n, char **ret) {
 184         const char *d;
 185         char *s;
 186
 187         assert(n);
 188         assert(ret);
 189
 190         if (!unit_name_is_valid(n, UNIT_NAME_ANY))
 191                 return -EINVAL;
 192
 193         d = strrchr(n, '.');
 194         if (!d)
 195                 return -EINVAL;
 196
 197         s = strndup(n, d - n);
 198         if (!s)
 199                 return -ENOMEM;
 200
 201         *ret = s;
 202         return 0;
 203 }
 204
 205 UnitType unit_name_to_type(const char *n) {
 206         const char *e;
 207
 208         assert(n);
 209
 210         if (!unit_name_is_valid(n, UNIT_NAME_ANY))
 211                 return _UNIT_TYPE_INVALID;
 212
 213         assert_se(e = strrchr(n, '.'));
 214
 215         return unit_type_from_string(e + 1);
 216 }
 217
 218 int unit_name_change_suffix(const char *n, const char *suffix, char **ret) {
 219         _cleanup_free_ char *s = NULL;
 220         size_t a, b;
 221         char *e;
 222
 223         assert(n);
 224         assert(suffix);
 225         assert(ret);
 226
 227         if (!unit_name_is_valid(n, UNIT_NAME_ANY))
 228                 return -EINVAL;
 229
 230         if (!unit_suffix_is_valid(suffix))
 231                 return -EINVAL;
 232
 233         assert_se(e = strrchr(n, '.'));
 234
 235         a = e - n;
 236         b = strlen(suffix);
 237
 238         s = new(char, a + b + 1);
 239         if (!s)
 240                 return -ENOMEM;
 241
 242         strcpy(mempcpy(s, n, a), suffix);
 243
 244         /* Make sure the name is still valid (i.e. didn't grow too large due to longer suffix) */
 245         if (!unit_name_is_valid(s, UNIT_NAME_ANY))
 246                 return -EINVAL;
 247
 248         *ret = TAKE_PTR(s);
 249         return 0;
 250 }
 251
 252 int unit_name_build(const char *prefix, const char *instance, const char *suffix, char **ret) {
 253         UnitType type;
 254
 255         assert(prefix);
 256         assert(suffix);
 257         assert(ret);
 258
 259         if (suffix[0] != '.')
 260                 return -EINVAL;
 261
 262         type = unit_type_from_string(suffix + 1);
 263         if (type < 0)
 264                 return type;
 265
 266         return unit_name_build_from_type(prefix, instance, type, ret);
 267 }
 268
 269 int unit_name_build_from_type(const char *prefix, const char *instance, UnitType type, char **ret) {
 270         _cleanup_free_ char *s = NULL;
 271         const char *ut;
 272
 273         assert(prefix);
 274         assert(type >= 0);
 275         assert(type < _UNIT_TYPE_MAX);
 276         assert(ret);
 277
 278         if (!unit_prefix_is_valid(prefix))
 279                 return -EINVAL;
 280
 281         ut = unit_type_to_string(type);
 282
 283         if (instance) {
 284                 if (!unit_instance_is_valid(instance))
 285                         return -EINVAL;
 286
 287                 s = strjoin(prefix, "@", instance, ".", ut);
 288         } else
 289                 s = strjoin(prefix, ".", ut);
 290         if (!s)
 291                 return -ENOMEM;
 292
 293         /* Verify that this didn't grow too large (or otherwise is invalid) */
 294         if (!unit_name_is_valid(s, instance ? UNIT_NAME_INSTANCE : UNIT_NAME_PLAIN))
 295                 return -EINVAL;
 296
 297         *ret = TAKE_PTR(s);
 298         return 0;
 299 }
 300
 301 static char *do_escape_char(char c, char *t) {
 302         assert(t);
 303
 304         *(t++) = '\\';
 305         *(t++) = 'x';
 306         *(t++) = hexchar(c >> 4);
 307         *(t++) = hexchar(c);
 308
 309         return t;
 310 }
 311
 312 static char *do_escape(const char *f, char *t) {
 313         assert(f);
 314         assert(t);
 315
 316         /* do not create units with a leading '.', like for "/.dotdir" mount points */
 317         if (*f == '.') {
 318                 t = do_escape_char(*f, t);
 319                 f++;
 320         }
 321
 322         for (; *f; f++) {
 323                 if (*f == '/')
 324                         *(t++) = '-';
 325                 else if (IN_SET(*f, '-', '\\') || !strchr(VALID_CHARS, *f))
 326                         t = do_escape_char(*f, t);
 327                 else
 328                         *(t++) = *f;
 329         }
 330
 331         return t;
 332 }
 333
 334 char *unit_name_escape(const char *f) {
 335         char *r, *t;
 336
 337         assert(f);
 338
 339         r = new(char, strlen(f)*4+1);
 340         if (!r)
 341                 return NULL;
 342
 343         t = do_escape(f, r);
 344         *t = 0;
 345
 346         return r;
 347 }
 348
 349 int unit_name_unescape(const char *f, char **ret) {
 350         _cleanup_free_ char *r = NULL;
 351         char *t;
 352
 353         assert(f);
 354
 355         r = strdup(f);
 356         if (!r)
 357                 return -ENOMEM;
 358
 359         for (t = r; *f; f++) {
 360                 if (*f == '-')
 361                         *(t++) = '/';
 362                 else if (*f == '\\') {
 363                         int a, b;
 364
 365                         if (f[1] != 'x')
 366                                 return -EINVAL;
 367
 368                         a = unhexchar(f[2]);
 369                         if (a < 0)
 370                                 return -EINVAL;
 371
 372                         b = unhexchar(f[3]);
 373                         if (b < 0)
 374                                 return -EINVAL;
 375
 376                         *(t++) = (char) (((uint8_t) a << 4U) | (uint8_t) b);
 377                         f += 3;
 378                 } else
 379                         *(t++) = *f;
 380         }
 381
 382         *t = 0;
 383
 384         *ret = TAKE_PTR(r);
 385
 386         return 0;
 387 }
 388
 389 int unit_name_path_escape(const char *f, char **ret) {
 390         _cleanup_free_ char *p = NULL;
 391         char *s;
 392
 393         assert(f);
 394         assert(ret);
 395
 396         p = strdup(f);
 397         if (!p)
 398                 return -ENOMEM;
 399
 400         path_simplify(p);
 401
 402         if (empty_or_root(p))
 403                 s = strdup("-");
 404         else {
 405                 if (!path_is_normalized(p))
 406                         return -EINVAL;
 407
 408                 /* Truncate trailing slashes and skip leading slashes */
 409                 delete_trailing_chars(p, "/");
 410                 s = unit_name_escape(skip_leading_chars(p, "/"));
 411         }
 412         if (!s)
 413                 return -ENOMEM;
 414
 415         *ret = s;
 416         return 0;
 417 }
 418
 419 int unit_name_path_unescape(const char *f, char **ret) {
 420         _cleanup_free_ char *s = NULL;
 421         int r;
 422
 423         assert(f);
 424
 425         if (isempty(f))
 426                 return -EINVAL;
 427
 428         if (streq(f, "-")) {
 429                 s = strdup("/");
 430                 if (!s)
 431                         return -ENOMEM;
 432         } else {
 433                 _cleanup_free_ char *w = NULL;
 434
 435                 r = unit_name_unescape(f, &w);
 436                 if (r < 0)
 437                         return r;
 438
 439                 /* Don't accept trailing or leading slashes */
 440                 if (startswith(w, "/") || endswith(w, "/"))
 441                         return -EINVAL;
 442
 443                 /* Prefix a slash again */
 444                 s = strjoin("/", w);
 445                 if (!s)
 446                         return -ENOMEM;
 447
 448                 if (!path_is_normalized(s))
 449                         return -EINVAL;
 450         }
 451
 452         if (ret)
 453                 *ret = TAKE_PTR(s);
 454
 455         return 0;
 456 }
 457
 458 int unit_name_replace_instance(const char *f, const char *i, char **ret) {
 459         _cleanup_free_ char *s = NULL;
 460         const char *p, *e;
 461         size_t a, b;
 462
 463         assert(f);
 464         assert(i);
 465         assert(ret);
 466
 467         if (!unit_name_is_valid(f, UNIT_NAME_INSTANCE|UNIT_NAME_TEMPLATE))
 468                 return -EINVAL;
 469         if (!unit_instance_is_valid(i))
 470                 return -EINVAL;
 471
 472         assert_se(p = strchr(f, '@'));
 473         assert_se(e = strrchr(f, '.'));
 474
 475         a = p - f;
 476         b = strlen(i);
 477
 478         s = new(char, a + 1 + b + strlen(e) + 1);
 479         if (!s)
 480                 return -ENOMEM;
 481
 482         strcpy(mempcpy(mempcpy(s, f, a + 1), i, b), e);
 483
 484         /* Make sure the resulting name still is valid, i.e. didn't grow too large */
 485         if (!unit_name_is_valid(s, UNIT_NAME_INSTANCE))
 486                 return -EINVAL;
 487
 488         *ret = TAKE_PTR(s);
 489         return 0;
 490 }
 491
 492 int unit_name_template(const char *f, char **ret) {
 493         const char *p, *e;
 494         char *s;
 495         size_t a;
 496
 497         assert(f);
 498         assert(ret);
 499
 500         if (!unit_name_is_valid(f, UNIT_NAME_INSTANCE|UNIT_NAME_TEMPLATE))
 501                 return -EINVAL;
 502
 503         assert_se(p = strchr(f, '@'));
 504         assert_se(e = strrchr(f, '.'));
 505
 506         a = p - f;
 507
 508         s = new(char, a + 1 + strlen(e) + 1);
 509         if (!s)
 510                 return -ENOMEM;
 511
 512         strcpy(mempcpy(s, f, a + 1), e);
 513
 514         *ret = s;
 515         return 0;
 516 }
 517
 518 bool unit_name_is_hashed(const char *name) {
 519         char *s;
 520
 521         if (!unit_name_is_valid(name, UNIT_NAME_PLAIN))
 522                 return false;
 523
 524         assert_se(s = strrchr(name, '.'));
 525
 526         if (s - name < UNIT_NAME_HASH_LENGTH_CHARS + 1)
 527                 return false;
 528
 529         s -= UNIT_NAME_HASH_LENGTH_CHARS;
 530         if (s[-1] != '_')
 531                 return false;
 532
 533         for (size_t i = 0; i < UNIT_NAME_HASH_LENGTH_CHARS; i++)
 534                 if (!strchr(LOWERCASE_HEXDIGITS, s[i]))
 535                         return false;
 536
 537         return true;
 538 }
 539
 540 int unit_name_hash_long(const char *name, char **ret) {
 541         _cleanup_free_ char *n = NULL, *hash = NULL;
 542         char *suffix;
 543         le64_t h;
 544         size_t len;
 545
 546         if (strlen(name) < UNIT_NAME_MAX)
 547                 return -EMSGSIZE;
 548
 549         suffix = strrchr(name, '.');
 550         if (!suffix)
 551                 return -EINVAL;
 552
 553         if (unit_type_from_string(suffix+1) < 0)
 554                 return -EINVAL;
 555
 556         h = htole64(siphash24_string(name, LONG_UNIT_NAME_HASH_KEY.bytes));
 557
 558         hash = hexmem(&h, sizeof(h));
 559         if (!hash)
 560                 return -ENOMEM;
 561
 562         assert_se(strlen(hash) == UNIT_NAME_HASH_LENGTH_CHARS);
 563
 564         len = UNIT_NAME_MAX - 1 - strlen(suffix+1) - UNIT_NAME_HASH_LENGTH_CHARS - 2;
 565         assert(len > 0 && len < UNIT_NAME_MAX);
 566
 567         n = strndup(name, len);
 568         if (!n)
 569                 return -ENOMEM;
 570
 571         if (!strextend(&n, "_", hash, suffix))
 572                 return -ENOMEM;
 573         assert_se(unit_name_is_valid(n, UNIT_NAME_PLAIN));
 574
 575         *ret = TAKE_PTR(n);
 576
 577         return 0;
 578 }
 579
 580 int unit_name_from_path(const char *path, const char *suffix, char **ret) {
 581         _cleanup_free_ char *p = NULL, *s = NULL;
 582         int r;
 583
 584         assert(path);
 585         assert(suffix);
 586         assert(ret);
 587
 588         if (!unit_suffix_is_valid(suffix))
 589                 return -EINVAL;
 590
 591         r = unit_name_path_escape(path, &p);
 592         if (r < 0)
 593                 return r;
 594
 595         s = strjoin(p, suffix);
 596         if (!s)
 597                 return -ENOMEM;
 598
 599         if (strlen(s) >= UNIT_NAME_MAX) {
 600                 _cleanup_free_ char *n = NULL;
 601
 602                 log_debug("Unit name \"%s\" too long, falling back to hashed unit name.", s);
 603
 604                 r = unit_name_hash_long(s, &n);
 605                 if (r < 0)
 606                         return r;
 607
 608                 free_and_replace(s, n);
 609         }
 610
 611         /* Refuse if this for some other reason didn't result in a valid name */
 612         if (!unit_name_is_valid(s, UNIT_NAME_PLAIN))
 613                 return -EINVAL;
 614
 615         *ret = TAKE_PTR(s);
 616         return 0;
 617 }
 618
 619 int unit_name_from_path_instance(const char *prefix, const char *path, const char *suffix, char **ret) {
 620         _cleanup_free_ char *p = NULL, *s = NULL;
 621         int r;
 622
 623         assert(prefix);
 624         assert(path);
 625         assert(suffix);
 626         assert(ret);
 627
 628         if (!unit_prefix_is_valid(prefix))
 629                 return -EINVAL;
 630
 631         if (!unit_suffix_is_valid(suffix))
 632                 return -EINVAL;
 633
 634         r = unit_name_path_escape(path, &p);
 635         if (r < 0)
 636                 return r;
 637
 638         s = strjoin(prefix, "@", p, suffix);
 639         if (!s)
 640                 return -ENOMEM;
 641
 642         if (strlen(s) >= UNIT_NAME_MAX) /* Return a slightly more descriptive error for this specific condition */
 643                 return -ENAMETOOLONG;
 644
 645         /* Refuse if this for some other reason didn't result in a valid name */
 646         if (!unit_name_is_valid(s, UNIT_NAME_INSTANCE))
 647                 return -EINVAL;
 648
 649         *ret = TAKE_PTR(s);
 650         return 0;
 651 }
 652
 653 int unit_name_to_path(const char *name, char **ret) {
 654         _cleanup_free_ char *prefix = NULL;
 655         int r;
 656
 657         assert(name);
 658
 659         r = unit_name_to_prefix(name, &prefix);
 660         if (r < 0)
 661                 return r;
 662
 663         if (unit_name_is_hashed(name))
 664                 return -ENAMETOOLONG;
 665
 666         return unit_name_path_unescape(prefix, ret);
 667 }
 668
 669 static bool do_escape_mangle(const char *f, bool allow_globs, char *t) {
 670         const char *valid_chars;
 671         bool mangled = false;
 672
 673         assert(f);
 674         assert(t);
 675
 676         /* We'll only escape the obvious characters here, to play safe.
 677          *
 678          * Returns true if any characters were mangled, false otherwise.
 679          */
 680
 681         valid_chars = allow_globs ? VALID_CHARS_GLOB : VALID_CHARS_WITH_AT;
 682
 683         for (; *f; f++)
 684                 if (*f == '/') {
 685                         *(t++) = '-';
 686                         mangled = true;
 687                 } else if (!strchr(valid_chars, *f)) {
 688                         t = do_escape_char(*f, t);
 689                         mangled = true;
 690                 } else
 691                         *(t++) = *f;
 692         *t = 0;
 693
 694         return mangled;
 695 }
 696
 697 /**
 698  *  Convert a string to a unit name. /dev/blah is converted to dev-blah.device,
 699  *  /blah/blah is converted to blah-blah.mount, anything else is left alone,
 700  *  except that @suffix is appended if a valid unit suffix is not present.
 701  *
 702  *  If @allow_globs, globs characters are preserved. Otherwise, they are escaped.
 703  */
 704 int unit_name_mangle_with_suffix(const char *name, const char *operation, UnitNameMangle flags, const char *suffix, char **ret) {
 705         _cleanup_free_ char *s = NULL;
 706         bool mangled, suggest_escape = true;
 707         int r;
 708
 709         assert(name);
 710         assert(suffix);
 711         assert(ret);
 712
 713         if (isempty(name)) /* We cannot mangle empty unit names to become valid, sorry. */
 714                 return -EINVAL;
 715
 716         if (!unit_suffix_is_valid(suffix))
 717                 return -EINVAL;
 718
 719         /* Already a fully valid unit name? If so, no mangling is necessary... */
 720         if (unit_name_is_valid(name, UNIT_NAME_ANY))
 721                 goto good;
 722
 723         /* Already a fully valid globbing expression? If so, no mangling is necessary either... */
 724         if (string_is_glob(name) && in_charset(name, VALID_CHARS_GLOB)) {
 725                 if (flags & UNIT_NAME_MANGLE_GLOB)
 726                         goto good;
 727                 log_full(flags & UNIT_NAME_MANGLE_WARN ? LOG_NOTICE : LOG_DEBUG,
 728                          "Glob pattern passed%s%s, but globs are not supported for this.",
 729                          operation ? " " : "", strempty(operation));
 730                 suggest_escape = false;
 731         }
 732
 733         if (is_device_path(name)) {
 734                 r = unit_name_from_path(name, ".device", ret);
 735                 if (r >= 0)
 736                         return 1;
 737                 if (r != -EINVAL)
 738                         return r;
 739         }
 740
 741         if (path_is_absolute(name)) {
 742                 r = unit_name_from_path(name, ".mount", ret);
 743                 if (r >= 0)
 744                         return 1;
 745                 if (r != -EINVAL)
 746                         return r;
 747         }
 748
 749         s = new(char, strlen(name) * 4 + strlen(suffix) + 1);
 750         if (!s)
 751                 return -ENOMEM;
 752
 753         mangled = do_escape_mangle(name, flags & UNIT_NAME_MANGLE_GLOB, s);
 754         if (mangled)
 755                 log_full(flags & UNIT_NAME_MANGLE_WARN ? LOG_NOTICE : LOG_DEBUG,
 756                          "Invalid unit name \"%s\" escaped as \"%s\"%s.",
 757                          name, s,
 758                          suggest_escape ? " (maybe you should use systemd-escape?)" : "");
 759
 760         /* Append a suffix if it doesn't have any, but only if this is not a glob, so that we can allow
 761          * "foo.*" as a valid glob. */
 762         if ((!(flags & UNIT_NAME_MANGLE_GLOB) || !string_is_glob(s)) && unit_name_to_type(s) < 0)
 763                 strcat(s, suffix);
 764
 765         /* Make sure mangling didn't grow this too large (but don't do this check if globbing is allowed,
 766          * since globs generally do not qualify as valid unit names) */
 767         if (!FLAGS_SET(flags, UNIT_NAME_MANGLE_GLOB) && !unit_name_is_valid(s, UNIT_NAME_ANY))
 768                 return -EINVAL;
 769
 770         *ret = TAKE_PTR(s);
 771         return 1;
 772
 773 good:
 774         s = strdup(name);
 775         if (!s)
 776                 return -ENOMEM;
 777
 778         *ret = TAKE_PTR(s);
 779         return 0;
 780 }
 781
 782 int slice_build_parent_slice(const char *slice, char **ret) {
 783         _cleanup_free_ char *s = NULL;
 784         char *dash;
 785         int r;
 786
 787         assert(slice);
 788         assert(ret);
 789
 790         if (!slice_name_is_valid(slice))
 791                 return -EINVAL;
 792
 793         if (streq(slice, SPECIAL_ROOT_SLICE)) {
 794                 *ret = NULL;
 795                 return 0;
 796         }
 797
 798         s = strdup(slice);
 799         if (!s)
 800                 return -ENOMEM;
 801
 802         dash = strrchr(s, '-');
 803         if (dash)
 804                 strcpy(dash, ".slice");
 805         else {
 806                 r = free_and_strdup(&s, SPECIAL_ROOT_SLICE);
 807                 if (r < 0)
 808                         return r;
 809         }
 810
 811         *ret = TAKE_PTR(s);
 812         return 1;
 813 }
 814
 815 int slice_build_subslice(const char *slice, const char *name, char **ret) {
 816         char *subslice;
 817
 818         assert(slice);
 819         assert(name);
 820         assert(ret);
 821
 822         if (!slice_name_is_valid(slice))
 823                 return -EINVAL;
 824
 825         if (!unit_prefix_is_valid(name))
 826                 return -EINVAL;
 827
 828         if (streq(slice, SPECIAL_ROOT_SLICE))
 829                 subslice = strjoin(name, ".slice");
 830         else {
 831                 char *e;
 832
 833                 assert_se(e = endswith(slice, ".slice"));
 834
 835                 subslice = new(char, (e - slice) + 1 + strlen(name) + 6 + 1);
 836                 if (!subslice)
 837                         return -ENOMEM;
 838
 839                 stpcpy(stpcpy(stpcpy(mempcpy(subslice, slice, e - slice), "-"), name), ".slice");
 840         }
 841
 842         *ret = subslice;
 843         return 0;
 844 }
 845
 846 bool slice_name_is_valid(const char *name) {
 847         const char *p, *e;
 848         bool dash = false;
 849
 850         if (!unit_name_is_valid(name, UNIT_NAME_PLAIN))
 851                 return false;
 852
 853         if (streq(name, SPECIAL_ROOT_SLICE))
 854                 return true;
 855
 856         e = endswith(name, ".slice");
 857         if (!e)
 858                 return false;
 859
 860         for (p = name; p < e; p++) {
 861
 862                 if (*p == '-') {
 863
 864                         /* Don't allow initial dash */
 865                         if (p == name)
 866                                 return false;
 867
 868                         /* Don't allow multiple dashes */
 869                         if (dash)
 870                                 return false;
 871
 872                         dash = true;
 873                 } else
 874                         dash = false;
 875         }
 876
 877         /* Don't allow trailing hash */
 878         if (dash)
 879                 return false;
 880
 881         return true;
 882 }
 883
 884 bool unit_name_prefix_equal(const char *a, const char *b) {
 885         const char *p, *q;
 886
 887         assert(a);
 888         assert(b);
 889
 890         if (!unit_name_is_valid(a, UNIT_NAME_ANY) || !unit_name_is_valid(b, UNIT_NAME_ANY))
 891                 return false;
 892
 893         p = strchr(a, '@');
 894         if (!p)
 895                 p = strrchr(a, '.');
 896
 897         q = strchr(b, '@');
 898         if (!q)
 899                 q = strrchr(b, '.');
 900
 901         assert(p);
 902         assert(q);
 903
 904         return memcmp_nn(a, p - a, b, q - b) == 0;
 905 }