src/basic/fileio.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   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 <sys/stat.h>
  12 #include <sys/types.h>
  13 #include <unistd.h>
  14
  15 #include "alloc-util.h"
  16 #include "fd-util.h"
  17 #include "fileio.h"
  18 #include "fs-util.h"
  19 #include "hexdecoct.h"
  20 #include "log.h"
  21 #include "macro.h"
  22 #include "mkdir.h"
  23 #include "parse-util.h"
  24 #include "path-util.h"
  25 #include "socket-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 int take_fdopen_unlocked(int *fd, const char *options, FILE **ret) {
  59         int     r;
  60
  61         assert(fd);
  62
  63         r = fdopen_unlocked(*fd, options, ret);
  64         if (r < 0)
  65                 return r;
  66
  67         *fd = -1;
  68
  69         return 0;
  70 }
  71
  72 FILE* take_fdopen(int *fd, const char *options) {
  73         assert(fd);
  74
  75         FILE *f = fdopen(*fd, options);
  76         if (!f)
  77                 return NULL;
  78
  79         *fd = -1;
  80
  81         return f;
  82 }
  83
  84 DIR* take_fdopendir(int *dfd) {
  85         assert(dfd);
  86
  87         DIR *d = fdopendir(*dfd);
  88         if (!d)
  89                 return NULL;
  90
  91         *dfd = -1;
  92
  93         return d;
  94 }
  95
  96 FILE* open_memstream_unlocked(char **ptr, size_t *sizeloc) {
  97         FILE *f = open_memstream(ptr, sizeloc);
  98         if (!f)
  99                 return NULL;
 100
 101         (void) __fsetlocking(f, FSETLOCKING_BYCALLER);
 102
 103         return f;
 104 }
 105
 106 FILE* fmemopen_unlocked(void *buf, size_t size, const char *mode) {
 107         FILE *f = fmemopen(buf, size, mode);
 108         if (!f)
 109                 return NULL;
 110
 111         (void) __fsetlocking(f, FSETLOCKING_BYCALLER);
 112
 113         return f;
 114 }
 115
 116 int write_string_stream_ts(
 117                 FILE *f,
 118                 const char *line,
 119                 WriteStringFileFlags flags,
 120                 const struct timespec *ts) {
 121
 122         bool needs_nl;
 123         int r, fd;
 124
 125         assert(f);
 126         assert(line);
 127
 128         if (ferror(f))
 129                 return -EIO;
 130
 131         if (ts) {
 132                 /* If we shall set the timestamp we need the fd. But fmemopen() streams generally don't have
 133                  * an fd. Let's fail early in that case. */
 134                 fd = fileno(f);
 135                 if (fd < 0)
 136                         return -EBADF;
 137         }
 138
 139         needs_nl = !(flags & WRITE_STRING_FILE_AVOID_NEWLINE) && !endswith(line, "\n");
 140
 141         if (needs_nl && (flags & WRITE_STRING_FILE_DISABLE_BUFFER)) {
 142                 /* If STDIO buffering was disabled, then let's append the newline character to the string itself, so
 143                  * that the write goes out in one go, instead of two */
 144
 145                 line = strjoina(line, "\n");
 146                 needs_nl = false;
 147         }
 148
 149         if (fputs(line, f) == EOF)
 150                 return -errno;
 151
 152         if (needs_nl)
 153                 if (fputc('\n', f) == EOF)
 154                         return -errno;
 155
 156         if (flags & WRITE_STRING_FILE_SYNC)
 157                 r = fflush_sync_and_check(f);
 158         else
 159                 r = fflush_and_check(f);
 160         if (r < 0)
 161                 return r;
 162
 163         if (ts) {
 164                 const struct timespec twice[2] = {*ts, *ts};
 165
 166                 if (futimens(fd, twice) < 0)
 167                         return -errno;
 168         }
 169
 170         return 0;
 171 }
 172
 173 static int write_string_file_atomic(
 174                 const char *fn,
 175                 const char *line,
 176                 WriteStringFileFlags flags,
 177                 const struct timespec *ts) {
 178
 179         _cleanup_fclose_ FILE *f = NULL;
 180         _cleanup_free_ char *p = NULL;
 181         int r;
 182
 183         assert(fn);
 184         assert(line);
 185
 186         /* Note that we'd really like to use O_TMPFILE here, but can't really, since we want replacement
 187          * semantics here, and O_TMPFILE can't offer that. i.e. rename() replaces but linkat() doesn't. */
 188
 189         r = fopen_temporary(fn, &f, &p);
 190         if (r < 0)
 191                 return r;
 192
 193         r = write_string_stream_ts(f, line, flags, ts);
 194         if (r < 0)
 195                 goto fail;
 196
 197         r = fchmod_umask(fileno(f), FLAGS_SET(flags, WRITE_STRING_FILE_MODE_0600) ? 0600 : 0644);
 198         if (r < 0)
 199                 goto fail;
 200
 201         if (rename(p, fn) < 0) {
 202                 r = -errno;
 203                 goto fail;
 204         }
 205
 206         if (FLAGS_SET(flags, WRITE_STRING_FILE_SYNC)) {
 207                 /* Sync the rename, too */
 208                 r = fsync_directory_of_file(fileno(f));
 209                 if (r < 0)
 210                         return r;
 211         }
 212
 213         return 0;
 214
 215 fail:
 216         (void) unlink(p);
 217         return r;
 218 }
 219
 220 int write_string_file_ts(
 221                 const char *fn,
 222                 const char *line,
 223                 WriteStringFileFlags flags,
 224                 const struct timespec *ts) {
 225
 226         _cleanup_fclose_ FILE *f = NULL;
 227         int q, r, fd;
 228
 229         assert(fn);
 230         assert(line);
 231
 232         /* We don't know how to verify whether the file contents was already on-disk. */
 233         assert(!((flags & WRITE_STRING_FILE_VERIFY_ON_FAILURE) && (flags & WRITE_STRING_FILE_SYNC)));
 234
 235         if (flags & WRITE_STRING_FILE_MKDIR_0755) {
 236                 r = mkdir_parents(fn, 0755);
 237                 if (r < 0)
 238                         return r;
 239         }
 240
 241         if (flags & WRITE_STRING_FILE_ATOMIC) {
 242                 assert(flags & WRITE_STRING_FILE_CREATE);
 243
 244                 r = write_string_file_atomic(fn, line, flags, ts);
 245                 if (r < 0)
 246                         goto fail;
 247
 248                 return r;
 249         } else
 250                 assert(!ts);
 251
 252         /* We manually build our own version of fopen(..., "we") that works without O_CREAT and with O_NOFOLLOW if needed. */
 253         fd = open(fn, O_WRONLY|O_CLOEXEC|O_NOCTTY |
 254                   (FLAGS_SET(flags, WRITE_STRING_FILE_NOFOLLOW) ? O_NOFOLLOW : 0) |
 255                   (FLAGS_SET(flags, WRITE_STRING_FILE_CREATE) ? O_CREAT : 0) |
 256                   (FLAGS_SET(flags, WRITE_STRING_FILE_TRUNCATE) ? O_TRUNC : 0),
 257                   (FLAGS_SET(flags, WRITE_STRING_FILE_MODE_0600) ? 0600 : 0666));
 258         if (fd < 0) {
 259                 r = -errno;
 260                 goto fail;
 261         }
 262
 263         r = fdopen_unlocked(fd, "w", &f);
 264         if (r < 0) {
 265                 safe_close(fd);
 266                 goto fail;
 267         }
 268
 269         if (flags & WRITE_STRING_FILE_DISABLE_BUFFER)
 270                 setvbuf(f, NULL, _IONBF, 0);
 271
 272         r = write_string_stream_ts(f, line, flags, ts);
 273         if (r < 0)
 274                 goto fail;
 275
 276         return 0;
 277
 278 fail:
 279         if (!(flags & WRITE_STRING_FILE_VERIFY_ON_FAILURE))
 280                 return r;
 281
 282         f = safe_fclose(f);
 283
 284         /* OK, the operation failed, but let's see if the right
 285          * contents in place already. If so, eat up the error. */
 286
 287         q = verify_file(fn, line, !(flags & WRITE_STRING_FILE_AVOID_NEWLINE));
 288         if (q <= 0)
 289                 return r;
 290
 291         return 0;
 292 }
 293
 294 int write_string_filef(
 295                 const char *fn,
 296                 WriteStringFileFlags flags,
 297                 const char *format, ...) {
 298
 299         _cleanup_free_ char *p = NULL;
 300         va_list ap;
 301         int r;
 302
 303         va_start(ap, format);
 304         r = vasprintf(&p, format, ap);
 305         va_end(ap);
 306
 307         if (r < 0)
 308                 return -ENOMEM;
 309
 310         return write_string_file(fn, p, flags);
 311 }
 312
 313 int read_one_line_file(const char *fn, char **line) {
 314         _cleanup_fclose_ FILE *f = NULL;
 315         int r;
 316
 317         assert(fn);
 318         assert(line);
 319
 320         r = fopen_unlocked(fn, "re", &f);
 321         if (r < 0)
 322                 return r;
 323
 324         return read_line(f, LONG_LINE_MAX, line);
 325 }
 326
 327 int verify_file(const char *fn, const char *blob, bool accept_extra_nl) {
 328         _cleanup_fclose_ FILE *f = NULL;
 329         _cleanup_free_ char *buf = NULL;
 330         size_t l, k;
 331         int r;
 332
 333         assert(fn);
 334         assert(blob);
 335
 336         l = strlen(blob);
 337
 338         if (accept_extra_nl && endswith(blob, "\n"))
 339                 accept_extra_nl = false;
 340
 341         buf = malloc(l + accept_extra_nl + 1);
 342         if (!buf)
 343                 return -ENOMEM;
 344
 345         r = fopen_unlocked(fn, "re", &f);
 346         if (r < 0)
 347                 return r;
 348
 349         /* We try to read one byte more than we need, so that we know whether we hit eof */
 350         errno = 0;
 351         k = fread(buf, 1, l + accept_extra_nl + 1, f);
 352         if (ferror(f))
 353                 return errno_or_else(EIO);
 354
 355         if (k != l && k != l + accept_extra_nl)
 356                 return 0;
 357         if (memcmp(buf, blob, l) != 0)
 358                 return 0;
 359         if (k > l && buf[l] != '\n')
 360                 return 0;
 361
 362         return 1;
 363 }
 364
 365 int read_full_virtual_file(const char *filename, char **ret_contents, size_t *ret_size) {
 366         _cleanup_free_ char *buf = NULL;
 367         _cleanup_close_ int fd = -1;
 368         struct stat st;
 369         size_t n, size;
 370         int n_retries;
 371         char *p;
 372
 373         assert(ret_contents);
 374
 375         /* Virtual filesystems such as sysfs or procfs use kernfs, and kernfs can work
 376          * with two sorts of virtual files. One sort uses "seq_file", and the results of
 377          * the first read are buffered for the second read. The other sort uses "raw"
 378          * reads which always go direct to the device. In the latter case, the content of
 379          * the virtual file must be retrieved with a single read otherwise a second read
 380          * might get the new value instead of finding EOF immediately. That's the reason
 381          * why the usage of fread(3) is prohibited in this case as it always performs a
 382          * second call to read(2) looking for EOF. See issue 13585. */
 383
 384         fd = open(filename, O_RDONLY|O_CLOEXEC);
 385         if (fd < 0)
 386                 return -errno;
 387
 388         /* Start size for files in /proc/ which usually report a file size of 0. (Files in /sys/ report a
 389          * file size of 4K, which is probably OK for sizing our initial buffer, and sysfs attributes can't be
 390          * larger anyway.) */
 391         size = LINE_MAX / 2;
 392
 393         /* Limit the number of attempts to read the number of bytes returned by fstat(). */
 394         n_retries = 3;
 395
 396         for (;;) {
 397                 if (n_retries <= 0)
 398                         return -EIO;
 399
 400                 if (fstat(fd, &st) < 0)
 401                         return -errno;
 402
 403                 if (!S_ISREG(st.st_mode))
 404                         return -EBADF;
 405
 406                 /* Be prepared for files from /proc which generally report a file size of 0. */
 407                 if (st.st_size > 0) {
 408                         size = st.st_size;
 409                         n_retries--;
 410                 } else
 411                         size = size * 2;
 412
 413                 if (size > READ_FULL_BYTES_MAX)
 414                         return -E2BIG;
 415
 416                 p = realloc(buf, size + 1);
 417                 if (!p)
 418                         return -ENOMEM;
 419                 buf = TAKE_PTR(p);
 420
 421                 for (;;) {
 422                         ssize_t k;
 423
 424                         /* Read one more byte so we can detect whether the content of the
 425                          * file has already changed or the guessed size for files from /proc
 426                          * wasn't large enough . */
 427                         k = read(fd, buf, size + 1);
 428                         if (k >= 0) {
 429                                 n = k;
 430                                 break;
 431                         }
 432
 433                         if (errno != EINTR)
 434                                 return -errno;
 435                 }
 436
 437                 /* Consider a short read as EOF */
 438                 if (n <= size)
 439                         break;
 440
 441                 /* Hmm... either we read too few bytes from /proc or less likely the content
 442                  * of the file might have been changed (and is now bigger) while we were
 443                  * processing, let's try again either with a bigger guessed size or the new
 444                  * file size. */
 445
 446                 if (lseek(fd, 0, SEEK_SET) < 0)
 447                         return -errno;
 448         }
 449
 450         if (n < size) {
 451                 p = realloc(buf, n + 1);
 452                 if (!p)
 453                         return -ENOMEM;
 454                 buf = TAKE_PTR(p);
 455         }
 456
 457         if (!ret_size) {
 458                 /* Safety check: if the caller doesn't want to know the size of what we
 459                  * just read it will rely on the trailing NUL byte. But if there's an
 460                  * embedded NUL byte, then we should refuse operation as otherwise
 461                  * there'd be ambiguity about what we just read. */
 462
 463                 if (memchr(buf, 0, n))
 464                         return -EBADMSG;
 465         } else
 466                 *ret_size = n;
 467
 468         buf[n] = 0;
 469         *ret_contents = TAKE_PTR(buf);
 470
 471         return 0;
 472 }
 473
 474 int read_full_stream_full(
 475                 FILE *f,
 476                 const char *filename,
 477                 uint64_t offset,
 478                 size_t size,
 479                 ReadFullFileFlags flags,
 480                 char **ret_contents,
 481                 size_t *ret_size) {
 482
 483         _cleanup_free_ char *buf = NULL;
 484         size_t n, n_next, l;
 485         int fd, r;
 486
 487         assert(f);
 488         assert(ret_contents);
 489         assert(!FLAGS_SET(flags, READ_FULL_FILE_UNBASE64 | READ_FULL_FILE_UNHEX));
 490
 491         if (offset != UINT64_MAX && offset > LONG_MAX)
 492                 return -ERANGE;
 493
 494         n_next = size != SIZE_MAX ? size : LINE_MAX; /* Start size */
 495
 496         fd = fileno(f);
 497         if (fd >= 0) { /* If the FILE* object is backed by an fd (as opposed to memory or such, see
 498                         * fmemopen()), let's optimize our buffering */
 499                 struct stat st;
 500
 501                 if (fstat(fd, &st) < 0)
 502                         return -errno;
 503
 504                 if (S_ISREG(st.st_mode)) {
 505                         if (size == SIZE_MAX) {
 506                                 uint64_t rsize =
 507                                         LESS_BY((uint64_t) st.st_size, offset == UINT64_MAX ? 0 : offset);
 508
 509                                 /* Safety check */
 510                                 if (rsize > READ_FULL_BYTES_MAX)
 511                                         return -E2BIG;
 512
 513                                 /* Start with the right file size. Note that we increase the size to read
 514                                  * here by one, so that the first read attempt already makes us notice the
 515                                  * EOF. If the reported size of the file is zero, we avoid this logic
 516                                  * however, since quite likely it might be a virtual file in procfs that all
 517                                  * report a zero file size. */
 518                                 if (st.st_size > 0)
 519                                         n_next = rsize + 1;
 520                         }
 521
 522                         if (flags & READ_FULL_FILE_WARN_WORLD_READABLE)
 523                                 (void) warn_file_is_world_accessible(filename, &st, NULL, 0);
 524                 }
 525         }
 526
 527         if (offset != UINT64_MAX && fseek(f, offset, SEEK_SET) < 0)
 528                 return -errno;
 529
 530         n = l = 0;
 531         for (;;) {
 532                 char *t;
 533                 size_t k;
 534
 535                 if (flags & READ_FULL_FILE_SECURE) {
 536                         t = malloc(n_next + 1);
 537                         if (!t) {
 538                                 r = -ENOMEM;
 539                                 goto finalize;
 540                         }
 541                         memcpy_safe(t, buf, n);
 542                         explicit_bzero_safe(buf, n);
 543                         buf = mfree(buf);
 544                 } else {
 545                         t = realloc(buf, n_next + 1);
 546                         if (!t)
 547                                 return -ENOMEM;
 548                 }
 549
 550                 buf = t;
 551                 /* Unless a size has been explicitly specified, try to read as much as fits into the memory
 552                  * we allocated (minus 1, to leave one byte for the safety NUL byte) */
 553                 n = size == SIZE_MAX ? malloc_usable_size(buf) - 1 : n_next;
 554
 555                 errno = 0;
 556                 k = fread(buf + l, 1, n - l, f);
 557
 558                 assert(k <= n - l);
 559                 l += k;
 560
 561                 if (ferror(f)) {
 562                         r = errno_or_else(EIO);
 563                         goto finalize;
 564                 }
 565                 if (feof(f))
 566                         break;
 567
 568                 if (size != SIZE_MAX) { /* If we got asked to read some specific size, we already sized the buffer right, hence leave */
 569                         assert(l == size);
 570                         break;
 571                 }
 572
 573                 assert(k > 0); /* we can't have read zero bytes because that would have been EOF */
 574
 575                 /* Safety check */
 576                 if (n >= READ_FULL_BYTES_MAX) {
 577                         r = -E2BIG;
 578                         goto finalize;
 579                 }
 580
 581                 n_next = MIN(n * 2, READ_FULL_BYTES_MAX);
 582         }
 583
 584         if (flags & (READ_FULL_FILE_UNBASE64 | READ_FULL_FILE_UNHEX)) {
 585                 _cleanup_free_ void *decoded = NULL;
 586                 size_t decoded_size;
 587
 588                 buf[l++] = 0;
 589                 if (flags & READ_FULL_FILE_UNBASE64)
 590                         r = unbase64mem_full(buf, l, flags & READ_FULL_FILE_SECURE, &decoded, &decoded_size);
 591                 else
 592                         r = unhexmem_full(buf, l, flags & READ_FULL_FILE_SECURE, &decoded, &decoded_size);
 593                 if (r < 0)
 594                         goto finalize;
 595
 596                 if (flags & READ_FULL_FILE_SECURE)
 597                         explicit_bzero_safe(buf, n);
 598                 free_and_replace(buf, decoded);
 599                 n = l = decoded_size;
 600         }
 601
 602         if (!ret_size) {
 603                 /* Safety check: if the caller doesn't want to know the size of what we just read it will rely on the
 604                  * trailing NUL byte. But if there's an embedded NUL byte, then we should refuse operation as otherwise
 605                  * there'd be ambiguity about what we just read. */
 606
 607                 if (memchr(buf, 0, l)) {
 608                         r = -EBADMSG;
 609                         goto finalize;
 610                 }
 611         }
 612
 613         buf[l] = 0;
 614         *ret_contents = TAKE_PTR(buf);
 615
 616         if (ret_size)
 617                 *ret_size = l;
 618
 619         return 0;
 620
 621 finalize:
 622         if (flags & READ_FULL_FILE_SECURE)
 623                 explicit_bzero_safe(buf, n);
 624
 625         return r;
 626 }
 627
 628 int read_full_file_full(
 629                 int dir_fd,
 630                 const char *filename,
 631                 uint64_t offset,
 632                 size_t size,
 633                 ReadFullFileFlags flags,
 634                 const char *bind_name,
 635                 char **ret_contents,
 636                 size_t *ret_size) {
 637
 638         _cleanup_fclose_ FILE *f = NULL;
 639         int r;
 640
 641         assert(filename);
 642         assert(ret_contents);
 643
 644         r = xfopenat(dir_fd, filename, "re", 0, &f);
 645         if (r < 0) {
 646                 _cleanup_close_ int dfd = -1, sk = -1;
 647                 union sockaddr_union sa;
 648
 649                 /* ENXIO is what Linux returns if we open a node that is an AF_UNIX socket */
 650                 if (r != -ENXIO)
 651                         return r;
 652
 653                 /* If this is enabled, let's try to connect to it */
 654                 if (!FLAGS_SET(flags, READ_FULL_FILE_CONNECT_SOCKET))
 655                         return -ENXIO;
 656
 657                 /* Seeking is not supported on AF_UNIX sockets */
 658                 if (offset != UINT64_MAX)
 659                         return -ESPIPE;
 660
 661                 if (dir_fd == AT_FDCWD)
 662                         r = sockaddr_un_set_path(&sa.un, filename);
 663                 else {
 664                         char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
 665
 666                         /* If we shall operate relative to some directory, then let's use O_PATH first to
 667                          * open the socket inode, and then connect to it via /proc/self/fd/. We have to do
 668                          * this since there's not connectat() that takes a directory fd as first arg. */
 669
 670                         dfd = openat(dir_fd, filename, O_PATH|O_CLOEXEC);
 671                         if (dfd < 0)
 672                                 return -errno;
 673
 674                         xsprintf(procfs_path, "/proc/self/fd/%i", dfd);
 675                         r = sockaddr_un_set_path(&sa.un, procfs_path);
 676                 }
 677                 if (r < 0)
 678                         return r;
 679
 680                 sk = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0);
 681                 if (sk < 0)
 682                         return -errno;
 683
 684                 if (bind_name) {
 685                         /* If the caller specified a socket name to bind to, do so before connecting. This is
 686                          * useful to communicate some minor, short meta-information token from the client to
 687                          * the server. */
 688                         union sockaddr_union bsa;
 689
 690                         r = sockaddr_un_set_path(&bsa.un, bind_name);
 691                         if (r < 0)
 692                                 return r;
 693
 694                         if (bind(sk, &bsa.sa, r) < 0)
 695                                 return r;
 696                 }
 697
 698                 if (connect(sk, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0)
 699                         return errno == ENOTSOCK ? -ENXIO : -errno; /* propagate original error if this is
 700                                                                      * not a socket after all */
 701
 702                 if (shutdown(sk, SHUT_WR) < 0)
 703                         return -errno;
 704
 705                 f = fdopen(sk, "r");
 706                 if (!f)
 707                         return -errno;
 708
 709                 TAKE_FD(sk);
 710         }
 711
 712         (void) __fsetlocking(f, FSETLOCKING_BYCALLER);
 713
 714         return read_full_stream_full(f, filename, offset, size, flags, ret_contents, ret_size);
 715 }
 716
 717 int executable_is_script(const char *path, char **interpreter) {
 718         _cleanup_free_ char *line = NULL;
 719         size_t len;
 720         char *ans;
 721         int r;
 722
 723         assert(path);
 724
 725         r = read_one_line_file(path, &line);
 726         if (r == -ENOBUFS) /* First line overly long? if so, then it's not a script */
 727                 return 0;
 728         if (r < 0)
 729                 return r;
 730
 731         if (!startswith(line, "#!"))
 732                 return 0;
 733
 734         ans = strstrip(line + 2);
 735         len = strcspn(ans, " \t");
 736
 737         if (len == 0)
 738                 return 0;
 739
 740         ans = strndup(ans, len);
 741         if (!ans)
 742                 return -ENOMEM;
 743
 744         *interpreter = ans;
 745         return 1;
 746 }
 747
 748 /**
 749  * Retrieve one field from a file like /proc/self/status.  pattern
 750  * should not include whitespace or the delimiter (':'). pattern matches only
 751  * the beginning of a line. Whitespace before ':' is skipped. Whitespace and
 752  * zeros after the ':' will be skipped. field must be freed afterwards.
 753  * terminator specifies the terminating characters of the field value (not
 754  * included in the value).
 755  */
 756 int get_proc_field(const char *filename, const char *pattern, const char *terminator, char **field) {
 757         _cleanup_free_ char *status = NULL;
 758         char *t, *f;
 759         size_t len;
 760         int r;
 761
 762         assert(terminator);
 763         assert(filename);
 764         assert(pattern);
 765         assert(field);
 766
 767         r = read_full_virtual_file(filename, &status, NULL);
 768         if (r < 0)
 769                 return r;
 770
 771         t = status;
 772
 773         do {
 774                 bool pattern_ok;
 775
 776                 do {
 777                         t = strstr(t, pattern);
 778                         if (!t)
 779                                 return -ENOENT;
 780
 781                         /* Check that pattern occurs in beginning of line. */
 782                         pattern_ok = (t == status || t[-1] == '\n');
 783
 784                         t += strlen(pattern);
 785
 786                 } while (!pattern_ok);
 787
 788                 t += strspn(t, " \t");
 789                 if (!*t)
 790                         return -ENOENT;
 791
 792         } while (*t != ':');
 793
 794         t++;
 795
 796         if (*t) {
 797                 t += strspn(t, " \t");
 798
 799                 /* Also skip zeros, because when this is used for
 800                  * capabilities, we don't want the zeros. This way the
 801                  * same capability set always maps to the same string,
 802                  * irrespective of the total capability set size. For
 803                  * other numbers it shouldn't matter. */
 804                 t += strspn(t, "0");
 805                 /* Back off one char if there's nothing but whitespace
 806                    and zeros */
 807                 if (!*t || isspace(*t))
 808                         t--;
 809         }
 810
 811         len = strcspn(t, terminator);
 812
 813         f = strndup(t, len);
 814         if (!f)
 815                 return -ENOMEM;
 816
 817         *field = f;
 818         return 0;
 819 }
 820
 821 DIR *xopendirat(int fd, const char *name, int flags) {
 822         int nfd;
 823         DIR *d;
 824
 825         assert(!(flags & O_CREAT));
 826
 827         nfd = openat(fd, name, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|flags, 0);
 828         if (nfd < 0)
 829                 return NULL;
 830
 831         d = fdopendir(nfd);
 832         if (!d) {
 833                 safe_close(nfd);
 834                 return NULL;
 835         }
 836
 837         return d;
 838 }
 839
 840 static int mode_to_flags(const char *mode) {
 841         const char *p;
 842         int flags;
 843
 844         if ((p = startswith(mode, "r+")))
 845                 flags = O_RDWR;
 846         else if ((p = startswith(mode, "r")))
 847                 flags = O_RDONLY;
 848         else if ((p = startswith(mode, "w+")))
 849                 flags = O_RDWR|O_CREAT|O_TRUNC;
 850         else if ((p = startswith(mode, "w")))
 851                 flags = O_WRONLY|O_CREAT|O_TRUNC;
 852         else if ((p = startswith(mode, "a+")))
 853                 flags = O_RDWR|O_CREAT|O_APPEND;
 854         else if ((p = startswith(mode, "a")))
 855                 flags = O_WRONLY|O_CREAT|O_APPEND;
 856         else
 857                 return -EINVAL;
 858
 859         for (; *p != 0; p++) {
 860
 861                 switch (*p) {
 862
 863                 case 'e':
 864                         flags |= O_CLOEXEC;
 865                         break;
 866
 867                 case 'x':
 868                         flags |= O_EXCL;
 869                         break;
 870
 871                 case 'm':
 872                         /* ignore this here, fdopen() might care later though */
 873                         break;
 874
 875                 case 'c': /* not sure what to do about this one */
 876                 default:
 877                         return -EINVAL;
 878                 }
 879         }
 880
 881         return flags;
 882 }
 883
 884 int xfopenat(int dir_fd, const char *path, const char *mode, int flags, FILE **ret) {
 885         FILE *f;
 886
 887         /* A combination of fopen() with openat() */
 888
 889         if (dir_fd == AT_FDCWD && flags == 0) {
 890                 f = fopen(path, mode);
 891                 if (!f)
 892                         return -errno;
 893         } else {
 894                 int fd, mode_flags;
 895
 896                 mode_flags = mode_to_flags(mode);
 897                 if (mode_flags < 0)
 898                         return mode_flags;
 899
 900                 fd = openat(dir_fd, path, mode_flags | flags);
 901                 if (fd < 0)
 902                         return -errno;
 903
 904                 f = fdopen(fd, mode);
 905                 if (!f) {
 906                         safe_close(fd);
 907                         return -errno;
 908                 }
 909         }
 910
 911         *ret = f;
 912         return 0;
 913 }
 914
 915 static int search_and_fopen_internal(const char *path, const char *mode, const char *root, char **search, FILE **_f) {
 916         char **i;
 917
 918         assert(path);
 919         assert(mode);
 920         assert(_f);
 921
 922         if (!path_strv_resolve_uniq(search, root))
 923                 return -ENOMEM;
 924
 925         STRV_FOREACH(i, search) {
 926                 _cleanup_free_ char *p = NULL;
 927                 FILE *f;
 928
 929                 p = path_join(root, *i, path);
 930                 if (!p)
 931                         return -ENOMEM;
 932
 933                 f = fopen(p, mode);
 934                 if (f) {
 935                         *_f = f;
 936                         return 0;
 937                 }
 938
 939                 if (errno != ENOENT)
 940                         return -errno;
 941         }
 942
 943         return -ENOENT;
 944 }
 945
 946 int search_and_fopen(const char *path, const char *mode, const char *root, const char **search, FILE **_f) {
 947         _cleanup_strv_free_ char **copy = NULL;
 948
 949         assert(path);
 950         assert(mode);
 951         assert(_f);
 952
 953         if (path_is_absolute(path)) {
 954                 FILE *f;
 955
 956                 f = fopen(path, mode);
 957                 if (f) {
 958                         *_f = f;
 959                         return 0;
 960                 }
 961
 962                 return -errno;
 963         }
 964
 965         copy = strv_copy((char**) search);
 966         if (!copy)
 967                 return -ENOMEM;
 968
 969         return search_and_fopen_internal(path, mode, root, copy, _f);
 970 }
 971
 972 int search_and_fopen_nulstr(const char *path, const char *mode, const char *root, const char *search, FILE **_f) {
 973         _cleanup_strv_free_ char **s = NULL;
 974
 975         if (path_is_absolute(path)) {
 976                 FILE *f;
 977
 978                 f = fopen(path, mode);
 979                 if (f) {
 980                         *_f = f;
 981                         return 0;
 982                 }
 983
 984                 return -errno;
 985         }
 986
 987         s = strv_split_nulstr(search);
 988         if (!s)
 989                 return -ENOMEM;
 990
 991         return search_and_fopen_internal(path, mode, root, s, _f);
 992 }
 993
 994 int chase_symlinks_and_fopen_unlocked(
 995                 const char *path,
 996                 const char *root,
 997                 unsigned chase_flags,
 998                 const char *open_flags,
 999                 FILE **ret_file,
1000                 char **ret_path) {
1001
1002         _cleanup_close_ int fd = -1;
1003         _cleanup_free_ char *final_path = NULL;
1004         int mode_flags, r;
1005         FILE *f;
1006
1007         assert(path);
1008         assert(open_flags);
1009         assert(ret_file);
1010
1011         mode_flags = mode_to_flags(open_flags);
1012         if (mode_flags < 0)
1013                 return mode_flags;
1014
1015         fd = chase_symlinks_and_open(path, root, chase_flags, mode_flags, ret_path ? &final_path : NULL);
1016         if (fd < 0)
1017                 return fd;
1018
1019         r = fdopen_unlocked(fd, open_flags, &f);
1020         if (r < 0)
1021                 return r;
1022         TAKE_FD(fd);
1023
1024         *ret_file = f;
1025         if (ret_path)
1026                 *ret_path = TAKE_PTR(final_path);
1027         return 0;
1028 }
1029
1030 int fflush_and_check(FILE *f) {
1031         assert(f);
1032
1033         errno = 0;
1034         fflush(f);
1035
1036         if (ferror(f))
1037                 return errno_or_else(EIO);
1038
1039         return 0;
1040 }
1041
1042 int fflush_sync_and_check(FILE *f) {
1043         int r, fd;
1044
1045         assert(f);
1046
1047         r = fflush_and_check(f);
1048         if (r < 0)
1049                 return r;
1050
1051         /* Not all file streams have an fd associated (think: fmemopen()), let's handle this gracefully and
1052          * assume that in that case we need no explicit syncing */
1053         fd = fileno(f);
1054         if (fd < 0)
1055                 return 0;
1056
1057         if (fsync(fd) < 0)
1058                 return -errno;
1059
1060         r = fsync_directory_of_file(fd);
1061         if (r < 0)
1062                 return r;
1063
1064         return 0;
1065 }
1066
1067 int write_timestamp_file_atomic(const char *fn, usec_t n) {
1068         char ln[DECIMAL_STR_MAX(n)+2];
1069
1070         /* Creates a "timestamp" file, that contains nothing but a
1071          * usec_t timestamp, formatted in ASCII. */
1072
1073         if (n <= 0 || n >= USEC_INFINITY)
1074                 return -ERANGE;
1075
1076         xsprintf(ln, USEC_FMT "\n", n);
1077
1078         return write_string_file(fn, ln, WRITE_STRING_FILE_CREATE|WRITE_STRING_FILE_ATOMIC);
1079 }
1080
1081 int read_timestamp_file(const char *fn, usec_t *ret) {
1082         _cleanup_free_ char *ln = NULL;
1083         uint64_t t;
1084         int r;
1085
1086         r = read_one_line_file(fn, &ln);
1087         if (r < 0)
1088                 return r;
1089
1090         r = safe_atou64(ln, &t);
1091         if (r < 0)
1092                 return r;
1093
1094         if (t <= 0 || t >= (uint64_t) USEC_INFINITY)
1095                 return -ERANGE;
1096
1097         *ret = (usec_t) t;
1098         return 0;
1099 }
1100
1101 int fputs_with_space(FILE *f, const char *s, const char *separator, bool *space) {
1102         int r;
1103
1104         assert(s);
1105
1106         /* Outputs the specified string with fputs(), but optionally prefixes it with a separator. The *space parameter
1107          * when specified shall initially point to a boolean variable initialized to false. It is set to true after the
1108          * first invocation. This call is supposed to be use in loops, where a separator shall be inserted between each
1109          * element, but not before the first one. */
1110
1111         if (!f)
1112                 f = stdout;
1113
1114         if (space) {
1115                 if (!separator)
1116                         separator = " ";
1117
1118                 if (*space) {
1119                         r = fputs(separator, f);
1120                         if (r < 0)
1121                                 return r;
1122                 }
1123
1124                 *space = true;
1125         }
1126
1127         return fputs(s, f);
1128 }
1129
1130 /* A bitmask of the EOL markers we know */
1131 typedef enum EndOfLineMarker {
1132         EOL_NONE     = 0,
1133         EOL_ZERO     = 1 << 0,  /* \0 (aka NUL) */
1134         EOL_TEN      = 1 << 1,  /* \n (aka NL, aka LF)  */
1135         EOL_THIRTEEN = 1 << 2,  /* \r (aka CR)  */
1136 } EndOfLineMarker;
1137
1138 static EndOfLineMarker categorize_eol(char c, ReadLineFlags flags) {
1139
1140         if (!IN_SET(flags, READ_LINE_ONLY_NUL)) {
1141                 if (c == '\n')
1142                         return EOL_TEN;
1143                 if (c == '\r')
1144                         return EOL_THIRTEEN;
1145         }
1146
1147         if (c == '\0')
1148                 return EOL_ZERO;
1149
1150         return EOL_NONE;
1151 }
1152
1153 DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(FILE*, funlockfile, NULL);
1154
1155 int read_line_full(FILE *f, size_t limit, ReadLineFlags flags, char **ret) {
1156         size_t n = 0, allocated = 0, count = 0;
1157         _cleanup_free_ char *buffer = NULL;
1158         int r;
1159
1160         assert(f);
1161
1162         /* Something like a bounded version of getline().
1163          *
1164          * Considers EOF, \n, \r and \0 end of line delimiters (or combinations of these), and does not include these
1165          * delimiters in the string returned. Specifically, recognizes the following combinations of markers as line
1166          * endings:
1167          *
1168          *     • \n        (UNIX)
1169          *     • \r        (old MacOS)
1170          *     • \0        (C strings)
1171          *     • \n\0
1172          *     • \r\0
1173          *     • \r\n      (Windows)
1174          *     • \n\r
1175          *     • \r\n\0
1176          *     • \n\r\0
1177          *
1178          * Returns the number of bytes read from the files (i.e. including delimiters — this hence usually differs from
1179          * the number of characters in the returned string). When EOF is hit, 0 is returned.
1180          *
1181          * The input parameter limit is the maximum numbers of characters in the returned string, i.e. excluding
1182          * delimiters. If the limit is hit we fail and return -ENOBUFS.
1183          *
1184          * If a line shall be skipped ret may be initialized as NULL. */
1185
1186         if (ret) {
1187                 if (!GREEDY_REALLOC(buffer, allocated, 1))
1188                         return -ENOMEM;
1189         }
1190
1191         {
1192                 _unused_ _cleanup_(funlockfilep) FILE *flocked = f;
1193                 EndOfLineMarker previous_eol = EOL_NONE;
1194                 flockfile(f);
1195
1196                 for (;;) {
1197                         EndOfLineMarker eol;
1198                         char c;
1199
1200                         if (n >= limit)
1201                                 return -ENOBUFS;
1202
1203                         if (count >= INT_MAX) /* We couldn't return the counter anymore as "int", hence refuse this */
1204                                 return -ENOBUFS;
1205
1206                         r = safe_fgetc(f, &c);
1207                         if (r < 0)
1208                                 return r;
1209                         if (r == 0) /* EOF is definitely EOL */
1210                                 break;
1211
1212                         eol = categorize_eol(c, flags);
1213
1214                         if (FLAGS_SET(previous_eol, EOL_ZERO) ||
1215                             (eol == EOL_NONE && previous_eol != EOL_NONE) ||
1216                             (eol != EOL_NONE && (previous_eol & eol) != 0)) {
1217                                 /* Previous char was a NUL? This is not an EOL, but the previous char was? This type of
1218                                  * EOL marker has been seen right before?  In either of these three cases we are
1219                                  * done. But first, let's put this character back in the queue. (Note that we have to
1220                                  * cast this to (unsigned char) here as ungetc() expects a positive 'int', and if we
1221                                  * are on an architecture where 'char' equals 'signed char' we need to ensure we don't
1222                                  * pass a negative value here. That said, to complicate things further ungetc() is
1223                                  * actually happy with most negative characters and implicitly casts them back to
1224                                  * positive ones as needed, except for \xff (aka -1, aka EOF), which it refuses. What a
1225                                  * godawful API!) */
1226                                 assert_se(ungetc((unsigned char) c, f) != EOF);
1227                                 break;
1228                         }
1229
1230                         count++;
1231
1232                         if (eol != EOL_NONE) {
1233                                 /* If we are on a tty, we can't shouldn't wait for more input, because that
1234                                  * generally means waiting for the user, interactively. In the case of a TTY
1235                                  * we expect only \n as the single EOL marker, so we are in the lucky
1236                                  * position that there is no need to wait. We check this condition last, to
1237                                  * avoid isatty() check if not necessary. */
1238
1239                                 if ((flags & (READ_LINE_IS_A_TTY|READ_LINE_NOT_A_TTY)) == 0) {
1240                                         int fd;
1241
1242                                         fd = fileno(f);
1243                                         if (fd < 0) /* Maybe an fmemopen() stream? Handle this gracefully,
1244                                                      * and don't call isatty() on an invalid fd */
1245                                                 flags |= READ_LINE_NOT_A_TTY;
1246                                         else
1247                                                 flags |= isatty(fd) ? READ_LINE_IS_A_TTY : READ_LINE_NOT_A_TTY;
1248                                 }
1249                                 if (FLAGS_SET(flags, READ_LINE_IS_A_TTY))
1250                                         break;
1251                         }
1252
1253                         if (eol != EOL_NONE) {
1254                                 previous_eol |= eol;
1255                                 continue;
1256                         }
1257
1258                         if (ret) {
1259                                 if (!GREEDY_REALLOC(buffer, allocated, n + 2))
1260                                         return -ENOMEM;
1261
1262                                 buffer[n] = c;
1263                         }
1264
1265                         n++;
1266                 }
1267         }
1268
1269         if (ret) {
1270                 buffer[n] = 0;
1271
1272                 *ret = TAKE_PTR(buffer);
1273         }
1274
1275         return (int) count;
1276 }
1277
1278 int safe_fgetc(FILE *f, char *ret) {
1279         int k;
1280
1281         assert(f);
1282
1283         /* A safer version of plain fgetc(): let's propagate the error that happened while reading as such, and
1284          * separate the EOF condition from the byte read, to avoid those confusion signed/unsigned issues fgetc()
1285          * has. */
1286
1287         errno = 0;
1288         k = fgetc(f);
1289         if (k == EOF) {
1290                 if (ferror(f))
1291                         return errno_or_else(EIO);
1292
1293                 if (ret)
1294                         *ret = 0;
1295
1296                 return 0;
1297         }
1298
1299         if (ret)
1300                 *ret = k;
1301
1302         return 1;
1303 }
1304
1305 int warn_file_is_world_accessible(const char *filename, struct stat *st, const char *unit, unsigned line) {
1306         struct stat _st;
1307
1308         if (!filename)
1309                 return 0;
1310
1311         if (!st) {
1312                 if (stat(filename, &_st) < 0)
1313                         return -errno;
1314                 st = &_st;
1315         }
1316
1317         if ((st->st_mode & S_IRWXO) == 0)
1318                 return 0;
1319
1320         if (unit)
1321                 log_syntax(unit, LOG_WARNING, filename, line, 0,
1322                            "%s has %04o mode that is too permissive, please adjust the ownership and access mode.",
1323                            filename, st->st_mode & 07777);
1324         else
1325                 log_warning("%s has %04o mode that is too permissive, please adjust the ownership and access mode.",
1326                             filename, st->st_mode & 07777);
1327         return 0;
1328 }
1329
1330 int rename_and_apply_smack_floor_label(const char *from, const char *to) {
1331         int r = 0;
1332         if (rename(from, to) < 0)
1333                 return -errno;
1334
1335 #ifdef SMACK_RUN_LABEL
1336         r = mac_smack_apply(to, SMACK_ATTR_ACCESS, SMACK_FLOOR_LABEL);
1337         if (r < 0)
1338                 return r;
1339 #endif
1340         return r;
1341 }