src/basic/fileio.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <ctype.h>
   4 #include <errno.h>
   5 #include <fcntl.h>
   6 #include <limits.h>
   7 #include <stdarg.h>
   8 #include <stdint.h>
   9 #include <stdio_ext.h>
  10 #include <stdlib.h>
  11 #include <string.h>
  12 #include <sys/stat.h>
  13 #include <sys/types.h>
  14 #include <unistd.h>
  15
  16 #include "alloc-util.h"
  17 #include "fd-util.h"
  18 #include "fileio.h"
  19 #include "fs-util.h"
  20 #include "hexdecoct.h"
  21 #include "log.h"
  22 #include "macro.h"
  23 #include "missing.h"
  24 #include "parse-util.h"
  25 #include "path-util.h"
  26 #include "stdio-util.h"
  27 #include "string-util.h"
  28 #include "tmpfile-util.h"
  29
  30 #define READ_FULL_BYTES_MAX (4U*1024U*1024U)
  31
  32 int fopen_unlocked(const char *path, const char *options, FILE **ret) {
  33         assert(ret);
  34
  35         FILE *f = fopen(path, options);
  36         if (!f)
  37                 return -errno;
  38
  39         (void) __fsetlocking(f, FSETLOCKING_BYCALLER);
  40
  41         *ret = f;
  42         return 0;
  43 }
  44
  45 int fdopen_unlocked(int fd, const char *options, FILE **ret) {
  46         assert(ret);
  47
  48         FILE *f = fdopen(fd, options);
  49         if (!f)
  50                 return -errno;
  51
  52         (void) __fsetlocking(f, FSETLOCKING_BYCALLER);
  53
  54         *ret = f;
  55         return 0;
  56 }
  57
  58 FILE* open_memstream_unlocked(char **ptr, size_t *sizeloc) {
  59         FILE *f = open_memstream(ptr, sizeloc);
  60         if (!f)
  61                 return NULL;
  62
  63         (void) __fsetlocking(f, FSETLOCKING_BYCALLER);
  64
  65         return f;
  66 }
  67
  68 FILE* fmemopen_unlocked(void *buf, size_t size, const char *mode) {
  69         FILE *f = fmemopen(buf, size, mode);
  70         if (!f)
  71                 return NULL;
  72
  73         (void) __fsetlocking(f, FSETLOCKING_BYCALLER);
  74
  75         return f;
  76 }
  77
  78 int write_string_stream_ts(
  79                 FILE *f,
  80                 const char *line,
  81                 WriteStringFileFlags flags,
  82                 struct timespec *ts) {
  83
  84         bool needs_nl;
  85         int r;
  86
  87         assert(f);
  88         assert(line);
  89
  90         if (ferror(f))
  91                 return -EIO;
  92
  93         needs_nl = !(flags & WRITE_STRING_FILE_AVOID_NEWLINE) && !endswith(line, "\n");
  94
  95         if (needs_nl && (flags & WRITE_STRING_FILE_DISABLE_BUFFER)) {
  96                 /* If STDIO buffering was disabled, then let's append the newline character to the string itself, so
  97                  * that the write goes out in one go, instead of two */
  98
  99                 line = strjoina(line, "\n");
 100                 needs_nl = false;
 101         }
 102
 103         if (fputs(line, f) == EOF)
 104                 return -errno;
 105
 106         if (needs_nl)
 107                 if (fputc('\n', f) == EOF)
 108                         return -errno;
 109
 110         if (flags & WRITE_STRING_FILE_SYNC)
 111                 r = fflush_sync_and_check(f);
 112         else
 113                 r = fflush_and_check(f);
 114         if (r < 0)
 115                 return r;
 116
 117         if (ts) {
 118                 struct timespec twice[2] = {*ts, *ts};
 119
 120                 if (futimens(fileno(f), twice) < 0)
 121                         return -errno;
 122         }
 123
 124         return 0;
 125 }
 126
 127 static int write_string_file_atomic(
 128                 const char *fn,
 129                 const char *line,
 130                 WriteStringFileFlags flags,
 131                 struct timespec *ts) {
 132
 133         _cleanup_fclose_ FILE *f = NULL;
 134         _cleanup_free_ char *p = NULL;
 135         int r;
 136
 137         assert(fn);
 138         assert(line);
 139
 140         r = fopen_temporary(fn, &f, &p);
 141         if (r < 0)
 142                 return r;
 143
 144         (void) fchmod_umask(fileno(f), 0644);
 145
 146         r = write_string_stream_ts(f, line, flags, ts);
 147         if (r < 0)
 148                 goto fail;
 149
 150         if (rename(p, fn) < 0) {
 151                 r = -errno;
 152                 goto fail;
 153         }
 154
 155         return 0;
 156
 157 fail:
 158         (void) unlink(p);
 159         return r;
 160 }
 161
 162 int write_string_file_ts(
 163                 const char *fn,
 164                 const char *line,
 165                 WriteStringFileFlags flags,
 166                 struct timespec *ts) {
 167
 168         _cleanup_fclose_ FILE *f = NULL;
 169         int q, r;
 170
 171         assert(fn);
 172         assert(line);
 173
 174         /* We don't know how to verify whether the file contents was already on-disk. */
 175         assert(!((flags & WRITE_STRING_FILE_VERIFY_ON_FAILURE) && (flags & WRITE_STRING_FILE_SYNC)));
 176
 177         if (flags & WRITE_STRING_FILE_ATOMIC) {
 178                 assert(flags & WRITE_STRING_FILE_CREATE);
 179
 180                 r = write_string_file_atomic(fn, line, flags, ts);
 181                 if (r < 0)
 182                         goto fail;
 183
 184                 return r;
 185         } else
 186                 assert(!ts);
 187
 188         if (flags & WRITE_STRING_FILE_CREATE) {
 189                 r = fopen_unlocked(fn, "we", &f);
 190                 if (r < 0)
 191                         goto fail;
 192         } else {
 193                 int fd;
 194
 195                 /* We manually build our own version of fopen(..., "we") that
 196                  * works without O_CREAT */
 197                 fd = open(fn, O_WRONLY|O_CLOEXEC|O_NOCTTY | ((flags & WRITE_STRING_FILE_NOFOLLOW) ? O_NOFOLLOW : 0));
 198                 if (fd < 0) {
 199                         r = -errno;
 200                         goto fail;
 201                 }
 202
 203                 r = fdopen_unlocked(fd, "w", &f);
 204                 if (r < 0) {
 205                         safe_close(fd);
 206                         goto fail;
 207                 }
 208         }
 209
 210         if (flags & WRITE_STRING_FILE_DISABLE_BUFFER)
 211                 setvbuf(f, NULL, _IONBF, 0);
 212
 213         r = write_string_stream_ts(f, line, flags, ts);
 214         if (r < 0)
 215                 goto fail;
 216
 217         return 0;
 218
 219 fail:
 220         if (!(flags & WRITE_STRING_FILE_VERIFY_ON_FAILURE))
 221                 return r;
 222
 223         f = safe_fclose(f);
 224
 225         /* OK, the operation failed, but let's see if the right
 226          * contents in place already. If so, eat up the error. */
 227
 228         q = verify_file(fn, line, !(flags & WRITE_STRING_FILE_AVOID_NEWLINE));
 229         if (q <= 0)
 230                 return r;
 231
 232         return 0;
 233 }
 234
 235 int write_string_filef(
 236                 const char *fn,
 237                 WriteStringFileFlags flags,
 238                 const char *format, ...) {
 239
 240         _cleanup_free_ char *p = NULL;
 241         va_list ap;
 242         int r;
 243
 244         va_start(ap, format);
 245         r = vasprintf(&p, format, ap);
 246         va_end(ap);
 247
 248         if (r < 0)
 249                 return -ENOMEM;
 250
 251         return write_string_file(fn, p, flags);
 252 }
 253
 254 int read_one_line_file(const char *fn, char **line) {
 255         _cleanup_fclose_ FILE *f = NULL;
 256         int r;
 257
 258         assert(fn);
 259         assert(line);
 260
 261         r = fopen_unlocked(fn, "re", &f);
 262         if (r < 0)
 263                 return r;
 264
 265         return read_line(f, LONG_LINE_MAX, line);
 266 }
 267
 268 int verify_file(const char *fn, const char *blob, bool accept_extra_nl) {
 269         _cleanup_fclose_ FILE *f = NULL;
 270         _cleanup_free_ char *buf = NULL;
 271         size_t l, k;
 272         int r;
 273
 274         assert(fn);
 275         assert(blob);
 276
 277         l = strlen(blob);
 278
 279         if (accept_extra_nl && endswith(blob, "\n"))
 280                 accept_extra_nl = false;
 281
 282         buf = malloc(l + accept_extra_nl + 1);
 283         if (!buf)
 284                 return -ENOMEM;
 285
 286         r = fopen_unlocked(fn, "re", &f);
 287         if (r < 0)
 288                 return r;
 289
 290         /* We try to read one byte more than we need, so that we know whether we hit eof */
 291         errno = 0;
 292         k = fread(buf, 1, l + accept_extra_nl + 1, f);
 293         if (ferror(f))
 294                 return errno > 0 ? -errno : -EIO;
 295
 296         if (k != l && k != l + accept_extra_nl)
 297                 return 0;
 298         if (memcmp(buf, blob, l) != 0)
 299                 return 0;
 300         if (k > l && buf[l] != '\n')
 301                 return 0;
 302
 303         return 1;
 304 }
 305
 306 int read_full_stream_full(
 307                 FILE *f,
 308                 const char *filename,
 309                 ReadFullFileFlags flags,
 310                 char **ret_contents,
 311                 size_t *ret_size) {
 312
 313         _cleanup_free_ char *buf = NULL;
 314         struct stat st;
 315         size_t n, n_next, l;
 316         int fd, r;
 317
 318         assert(f);
 319         assert(ret_contents);
 320         assert(!FLAGS_SET(flags, READ_FULL_FILE_UNBASE64 | READ_FULL_FILE_UNHEX));
 321         assert(!(flags & (READ_FULL_FILE_UNBASE64 | READ_FULL_FILE_UNHEX)) || ret_size);
 322
 323         n_next = LINE_MAX; /* Start size */
 324
 325         fd = fileno(f);
 326         if (fd >= 0) { /* If the FILE* object is backed by an fd (as opposed to memory or such, see fmemopen(), let's
 327                         * optimize our buffering) */
 328
 329                 if (fstat(fd, &st) < 0)
 330                         return -errno;
 331
 332                 if (S_ISREG(st.st_mode)) {
 333
 334                         /* Safety check */
 335                         if (st.st_size > READ_FULL_BYTES_MAX)
 336                                 return -E2BIG;
 337
 338                         /* Start with the right file size, but be prepared for files from /proc which generally report a file
 339                          * size of 0. Note that we increase the size to read here by one, so that the first read attempt
 340                          * already makes us notice the EOF. */
 341                         if (st.st_size > 0)
 342                                 n_next = st.st_size + 1;
 343
 344                         if (flags & READ_FULL_FILE_SECURE)
 345                                 (void) warn_file_is_world_accessible(filename, &st, NULL, 0);
 346                 }
 347         }
 348
 349         n = l = 0;
 350         for (;;) {
 351                 char *t;
 352                 size_t k;
 353
 354                 if (flags & READ_FULL_FILE_SECURE) {
 355                         t = malloc(n_next + 1);
 356                         if (!t) {
 357                                 r = -ENOMEM;
 358                                 goto finalize;
 359                         }
 360                         memcpy_safe(t, buf, n);
 361                         explicit_bzero_safe(buf, n);
 362                         buf = mfree(buf);
 363                 } else {
 364                         t = realloc(buf, n_next + 1);
 365                         if (!t)
 366                                 return -ENOMEM;
 367                 }
 368
 369                 buf = t;
 370                 n = n_next;
 371
 372                 errno = 0;
 373                 k = fread(buf + l, 1, n - l, f);
 374                 if (k > 0)
 375                         l += k;
 376
 377                 if (ferror(f)) {
 378                         r = errno > 0 ? -errno : -EIO;
 379                         goto finalize;
 380                 }
 381
 382                 if (feof(f))
 383                         break;
 384
 385                 /* We aren't expecting fread() to return a short read outside
 386                  * of (error && eof), assert buffer is full and enlarge buffer.
 387                  */
 388                 assert(l == n);
 389
 390                 /* Safety check */
 391                 if (n >= READ_FULL_BYTES_MAX) {
 392                         r = -E2BIG;
 393                         goto finalize;
 394                 }
 395
 396                 n_next = MIN(n * 2, READ_FULL_BYTES_MAX);
 397         }
 398
 399         if (flags & (READ_FULL_FILE_UNBASE64 | READ_FULL_FILE_UNHEX)) {
 400                 buf[l++] = 0;
 401                 if (flags & READ_FULL_FILE_UNBASE64)
 402                         r = unbase64mem_full(buf, l, flags & READ_FULL_FILE_SECURE, (void **) ret_contents, ret_size);
 403                 else
 404                         r = unhexmem_full(buf, l, flags & READ_FULL_FILE_SECURE, (void **) ret_contents, ret_size);
 405                 goto finalize;
 406         }
 407
 408         if (!ret_size) {
 409                 /* Safety check: if the caller doesn't want to know the size of what we just read it will rely on the
 410                  * trailing NUL byte. But if there's an embedded NUL byte, then we should refuse operation as otherwise
 411                  * there'd be ambiguity about what we just read. */
 412
 413                 if (memchr(buf, 0, l)) {
 414                         r = -EBADMSG;
 415                         goto finalize;
 416                 }
 417         }
 418
 419         buf[l] = 0;
 420         *ret_contents = TAKE_PTR(buf);
 421
 422         if (ret_size)
 423                 *ret_size = l;
 424
 425         return 0;
 426
 427 finalize:
 428         if (flags & READ_FULL_FILE_SECURE)
 429                 explicit_bzero_safe(buf, n);
 430
 431         return r;
 432 }
 433
 434 int read_full_file_full(const char *filename, ReadFullFileFlags flags, char **contents, size_t *size) {
 435         _cleanup_fclose_ FILE *f = NULL;
 436         int r;
 437
 438         assert(filename);
 439         assert(contents);
 440
 441         r = fopen_unlocked(filename, "re", &f);
 442         if (r < 0)
 443                 return r;
 444
 445         return read_full_stream_full(f, filename, flags, contents, size);
 446 }
 447
 448 int executable_is_script(const char *path, char **interpreter) {
 449         _cleanup_free_ char *line = NULL;
 450         size_t len;
 451         char *ans;
 452         int r;
 453
 454         assert(path);
 455
 456         r = read_one_line_file(path, &line);
 457         if (r == -ENOBUFS) /* First line overly long? if so, then it's not a script */
 458                 return 0;
 459         if (r < 0)
 460                 return r;
 461
 462         if (!startswith(line, "#!"))
 463                 return 0;
 464
 465         ans = strstrip(line + 2);
 466         len = strcspn(ans, " \t");
 467
 468         if (len == 0)
 469                 return 0;
 470
 471         ans = strndup(ans, len);
 472         if (!ans)
 473                 return -ENOMEM;
 474
 475         *interpreter = ans;
 476         return 1;
 477 }
 478
 479 /**
 480  * Retrieve one field from a file like /proc/self/status.  pattern
 481  * should not include whitespace or the delimiter (':'). pattern matches only
 482  * the beginning of a line. Whitespace before ':' is skipped. Whitespace and
 483  * zeros after the ':' will be skipped. field must be freed afterwards.
 484  * terminator specifies the terminating characters of the field value (not
 485  * included in the value).
 486  */
 487 int get_proc_field(const char *filename, const char *pattern, const char *terminator, char **field) {
 488         _cleanup_free_ char *status = NULL;
 489         char *t, *f;
 490         size_t len;
 491         int r;
 492
 493         assert(terminator);
 494         assert(filename);
 495         assert(pattern);
 496         assert(field);
 497
 498         r = read_full_file(filename, &status, NULL);
 499         if (r < 0)
 500                 return r;
 501
 502         t = status;
 503
 504         do {
 505                 bool pattern_ok;
 506
 507                 do {
 508                         t = strstr(t, pattern);
 509                         if (!t)
 510                                 return -ENOENT;
 511
 512                         /* Check that pattern occurs in beginning of line. */
 513                         pattern_ok = (t == status || t[-1] == '\n');
 514
 515                         t += strlen(pattern);
 516
 517                 } while (!pattern_ok);
 518
 519                 t += strspn(t, " \t");
 520                 if (!*t)
 521                         return -ENOENT;
 522
 523         } while (*t != ':');
 524
 525         t++;
 526
 527         if (*t) {
 528                 t += strspn(t, " \t");
 529
 530                 /* Also skip zeros, because when this is used for
 531                  * capabilities, we don't want the zeros. This way the
 532                  * same capability set always maps to the same string,
 533                  * irrespective of the total capability set size. For
 534                  * other numbers it shouldn't matter. */
 535                 t += strspn(t, "0");
 536                 /* Back off one char if there's nothing but whitespace
 537                    and zeros */
 538                 if (!*t || isspace(*t))
 539                         t--;
 540         }
 541
 542         len = strcspn(t, terminator);
 543
 544         f = strndup(t, len);
 545         if (!f)
 546                 return -ENOMEM;
 547
 548         *field = f;
 549         return 0;
 550 }
 551
 552 DIR *xopendirat(int fd, const char *name, int flags) {
 553         int nfd;
 554         DIR *d;
 555
 556         assert(!(flags & O_CREAT));
 557
 558         nfd = openat(fd, name, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|flags, 0);
 559         if (nfd < 0)
 560                 return NULL;
 561
 562         d = fdopendir(nfd);
 563         if (!d) {
 564                 safe_close(nfd);
 565                 return NULL;
 566         }
 567
 568         return d;
 569 }
 570
 571 static int search_and_fopen_internal(const char *path, const char *mode, const char *root, char **search, FILE **_f) {
 572         char **i;
 573
 574         assert(path);
 575         assert(mode);
 576         assert(_f);
 577
 578         if (!path_strv_resolve_uniq(search, root))
 579                 return -ENOMEM;
 580
 581         STRV_FOREACH(i, search) {
 582                 _cleanup_free_ char *p = NULL;
 583                 FILE *f;
 584
 585                 if (root)
 586                         p = strjoin(root, *i, "/", path);
 587                 else
 588                         p = strjoin(*i, "/", path);
 589                 if (!p)
 590                         return -ENOMEM;
 591
 592                 f = fopen(p, mode);
 593                 if (f) {
 594                         *_f = f;
 595                         return 0;
 596                 }
 597
 598                 if (errno != ENOENT)
 599                         return -errno;
 600         }
 601
 602         return -ENOENT;
 603 }
 604
 605 int search_and_fopen(const char *path, const char *mode, const char *root, const char **search, FILE **_f) {
 606         _cleanup_strv_free_ char **copy = NULL;
 607
 608         assert(path);
 609         assert(mode);
 610         assert(_f);
 611
 612         if (path_is_absolute(path)) {
 613                 FILE *f;
 614
 615                 f = fopen(path, mode);
 616                 if (f) {
 617                         *_f = f;
 618                         return 0;
 619                 }
 620
 621                 return -errno;
 622         }
 623
 624         copy = strv_copy((char**) search);
 625         if (!copy)
 626                 return -ENOMEM;
 627
 628         return search_and_fopen_internal(path, mode, root, copy, _f);
 629 }
 630
 631 int search_and_fopen_nulstr(const char *path, const char *mode, const char *root, const char *search, FILE **_f) {
 632         _cleanup_strv_free_ char **s = NULL;
 633
 634         if (path_is_absolute(path)) {
 635                 FILE *f;
 636
 637                 f = fopen(path, mode);
 638                 if (f) {
 639                         *_f = f;
 640                         return 0;
 641                 }
 642
 643                 return -errno;
 644         }
 645
 646         s = strv_split_nulstr(search);
 647         if (!s)
 648                 return -ENOMEM;
 649
 650         return search_and_fopen_internal(path, mode, root, s, _f);
 651 }
 652
 653 int fflush_and_check(FILE *f) {
 654         assert(f);
 655
 656         errno = 0;
 657         fflush(f);
 658
 659         if (ferror(f))
 660                 return errno > 0 ? -errno : -EIO;
 661
 662         return 0;
 663 }
 664
 665 int fflush_sync_and_check(FILE *f) {
 666         int r;
 667
 668         assert(f);
 669
 670         r = fflush_and_check(f);
 671         if (r < 0)
 672                 return r;
 673
 674         if (fsync(fileno(f)) < 0)
 675                 return -errno;
 676
 677         r = fsync_directory_of_file(fileno(f));
 678         if (r < 0)
 679                 return r;
 680
 681         return 0;
 682 }
 683
 684 int write_timestamp_file_atomic(const char *fn, usec_t n) {
 685         char ln[DECIMAL_STR_MAX(n)+2];
 686
 687         /* Creates a "timestamp" file, that contains nothing but a
 688          * usec_t timestamp, formatted in ASCII. */
 689
 690         if (n <= 0 || n >= USEC_INFINITY)
 691                 return -ERANGE;
 692
 693         xsprintf(ln, USEC_FMT "\n", n);
 694
 695         return write_string_file(fn, ln, WRITE_STRING_FILE_CREATE|WRITE_STRING_FILE_ATOMIC);
 696 }
 697
 698 int read_timestamp_file(const char *fn, usec_t *ret) {
 699         _cleanup_free_ char *ln = NULL;
 700         uint64_t t;
 701         int r;
 702
 703         r = read_one_line_file(fn, &ln);
 704         if (r < 0)
 705                 return r;
 706
 707         r = safe_atou64(ln, &t);
 708         if (r < 0)
 709                 return r;
 710
 711         if (t <= 0 || t >= (uint64_t) USEC_INFINITY)
 712                 return -ERANGE;
 713
 714         *ret = (usec_t) t;
 715         return 0;
 716 }
 717
 718 int fputs_with_space(FILE *f, const char *s, const char *separator, bool *space) {
 719         int r;
 720
 721         assert(s);
 722
 723         /* Outputs the specified string with fputs(), but optionally prefixes it with a separator. The *space parameter
 724          * when specified shall initially point to a boolean variable initialized to false. It is set to true after the
 725          * first invocation. This call is supposed to be use in loops, where a separator shall be inserted between each
 726          * element, but not before the first one. */
 727
 728         if (!f)
 729                 f = stdout;
 730
 731         if (space) {
 732                 if (!separator)
 733                         separator = " ";
 734
 735                 if (*space) {
 736                         r = fputs(separator, f);
 737                         if (r < 0)
 738                                 return r;
 739                 }
 740
 741                 *space = true;
 742         }
 743
 744         return fputs(s, f);
 745 }
 746
 747 /* A bitmask of the EOL markers we know */
 748 typedef enum EndOfLineMarker {
 749         EOL_NONE     = 0,
 750         EOL_ZERO     = 1 << 0,  /* \0 (aka NUL) */
 751         EOL_TEN      = 1 << 1,  /* \n (aka NL, aka LF)  */
 752         EOL_THIRTEEN = 1 << 2,  /* \r (aka CR)  */
 753 } EndOfLineMarker;
 754
 755 static EndOfLineMarker categorize_eol(char c, ReadLineFlags flags) {
 756
 757         if (!IN_SET(flags, READ_LINE_ONLY_NUL)) {
 758                 if (c == '\n')
 759                         return EOL_TEN;
 760                 if (c == '\r')
 761                         return EOL_THIRTEEN;
 762         }
 763
 764         if (c == '\0')
 765                 return EOL_ZERO;
 766
 767         return EOL_NONE;
 768 }
 769
 770 DEFINE_TRIVIAL_CLEANUP_FUNC(FILE*, funlockfile);
 771
 772 int read_line_full(FILE *f, size_t limit, ReadLineFlags flags, char **ret) {
 773         size_t n = 0, allocated = 0, count = 0;
 774         _cleanup_free_ char *buffer = NULL;
 775         int r;
 776
 777         assert(f);
 778
 779         /* Something like a bounded version of getline().
 780          *
 781          * Considers EOF, \n, \r and \0 end of line delimiters (or combinations of these), and does not include these
 782          * delimiters in the string returned. Specifically, recognizes the following combinations of markers as line
 783          * endings:
 784          *
 785          *     • \n        (UNIX)
 786          *     • \r        (old MacOS)
 787          *     • \0        (C strings)
 788          *     • \n\0
 789          *     • \r\0
 790          *     • \r\n      (Windows)
 791          *     • \n\r
 792          *     • \r\n\0
 793          *     • \n\r\0
 794          *
 795          * Returns the number of bytes read from the files (i.e. including delimiters — this hence usually differs from
 796          * the number of characters in the returned string). When EOF is hit, 0 is returned.
 797          *
 798          * The input parameter limit is the maximum numbers of characters in the returned string, i.e. excluding
 799          * delimiters. If the limit is hit we fail and return -ENOBUFS.
 800          *
 801          * If a line shall be skipped ret may be initialized as NULL. */
 802
 803         if (ret) {
 804                 if (!GREEDY_REALLOC(buffer, allocated, 1))
 805                         return -ENOMEM;
 806         }
 807
 808         {
 809                 _unused_ _cleanup_(funlockfilep) FILE *flocked = f;
 810                 EndOfLineMarker previous_eol = EOL_NONE;
 811                 flockfile(f);
 812
 813                 for (;;) {
 814                         EndOfLineMarker eol;
 815                         char c;
 816
 817                         if (n >= limit)
 818                                 return -ENOBUFS;
 819
 820                         if (count >= INT_MAX) /* We couldn't return the counter anymore as "int", hence refuse this */
 821                                 return -ENOBUFS;
 822
 823                         r = safe_fgetc(f, &c);
 824                         if (r < 0)
 825                                 return r;
 826                         if (r == 0) /* EOF is definitely EOL */
 827                                 break;
 828
 829                         eol = categorize_eol(c, flags);
 830
 831                         if (FLAGS_SET(previous_eol, EOL_ZERO) ||
 832                             (eol == EOL_NONE && previous_eol != EOL_NONE) ||
 833                             (eol != EOL_NONE && (previous_eol & eol) != 0)) {
 834                                 /* Previous char was a NUL? This is not an EOL, but the previous char was? This type of
 835                                  * EOL marker has been seen right before?  In either of these three cases we are
 836                                  * done. But first, let's put this character back in the queue. (Note that we have to
 837                                  * cast this to (unsigned char) here as ungetc() expects a positive 'int', and if we
 838                                  * are on an architecture where 'char' equals 'signed char' we need to ensure we don't
 839                                  * pass a negative value here. That said, to complicate things further ungetc() is
 840                                  * actually happy with most negative characters and implicitly casts them back to
 841                                  * positive ones as needed, except for \xff (aka -1, aka EOF), which it refuses. What a
 842                                  * godawful API!) */
 843                                 assert_se(ungetc((unsigned char) c, f) != EOF);
 844                                 break;
 845                         }
 846
 847                         count++;
 848
 849                         if (eol != EOL_NONE) {
 850                                 previous_eol |= eol;
 851                                 continue;
 852                         }
 853
 854                         if (ret) {
 855                                 if (!GREEDY_REALLOC(buffer, allocated, n + 2))
 856                                         return -ENOMEM;
 857
 858                                 buffer[n] = c;
 859                         }
 860
 861                         n++;
 862                 }
 863         }
 864
 865         if (ret) {
 866                 buffer[n] = 0;
 867
 868                 *ret = TAKE_PTR(buffer);
 869         }
 870
 871         return (int) count;
 872 }
 873
 874 int safe_fgetc(FILE *f, char *ret) {
 875         int k;
 876
 877         assert(f);
 878
 879         /* A safer version of plain fgetc(): let's propagate the error that happened while reading as such, and
 880          * separate the EOF condition from the byte read, to avoid those confusion signed/unsigned issues fgetc()
 881          * has. */
 882
 883         errno = 0;
 884         k = fgetc(f);
 885         if (k == EOF) {
 886                 if (ferror(f))
 887                         return errno > 0 ? -errno : -EIO;
 888
 889                 if (ret)
 890                         *ret = 0;
 891
 892                 return 0;
 893         }
 894
 895         if (ret)
 896                 *ret = k;
 897
 898         return 1;
 899 }
 900
 901 int warn_file_is_world_accessible(const char *filename, struct stat *st, const char *unit, unsigned line) {
 902         struct stat _st;
 903
 904         if (!filename)
 905                 return 0;
 906
 907         if (!st) {
 908                 if (stat(filename, &_st) < 0)
 909                         return -errno;
 910                 st = &_st;
 911         }
 912
 913         if ((st->st_mode & S_IRWXO) == 0)
 914                 return 0;
 915
 916         if (unit)
 917                 log_syntax(unit, LOG_WARNING, filename, line, 0,
 918                            "%s has %04o mode that is too permissive, please adjust the access mode.",
 919                            filename, st->st_mode & 07777);
 920         else
 921                 log_warning("%s has %04o mode that is too permissive, please adjust the access mode.",
 922                             filename, st->st_mode & 07777);
 923         return 0;
 924 }