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. */
 389         size = LINE_MAX / 2;
 390
 391         /* Limit the number of attempts to read the number of bytes returned by fstat(). */
 392         n_retries = 3;
 393
 394         for (;;) {
 395                 if (n_retries <= 0)
 396                         return -EIO;
 397
 398                 if (fstat(fd, &st) < 0)
 399                         return -errno;
 400
 401                 if (!S_ISREG(st.st_mode))
 402                         return -EBADF;
 403
 404                 /* Be prepared for files from /proc which generally report a file size of 0. */
 405                 if (st.st_size > 0) {
 406                         size = st.st_size;
 407                         n_retries--;
 408                 } else
 409                         size = size * 2;
 410
 411                 if (size > READ_FULL_BYTES_MAX)
 412                         return -E2BIG;
 413
 414                 p = realloc(buf, size + 1);
 415                 if (!p)
 416                         return -ENOMEM;
 417                 buf = TAKE_PTR(p);
 418
 419                 for (;;) {
 420                         ssize_t k;
 421
 422                         /* Read one more byte so we can detect whether the content of the
 423                          * file has already changed or the guessed size for files from /proc
 424                          * wasn't large enough . */
 425                         k = read(fd, buf, size + 1);
 426                         if (k >= 0) {
 427                                 n = k;
 428                                 break;
 429                         }
 430
 431                         if (errno != EINTR)
 432                                 return -errno;
 433                 }
 434
 435                 /* Consider a short read as EOF */
 436                 if (n <= size)
 437                         break;
 438
 439                 /* Hmm... either we read too few bytes from /proc or less likely the content
 440                  * of the file might have been changed (and is now bigger) while we were
 441                  * processing, let's try again either with a bigger guessed size or the new
 442                  * file size. */
 443
 444                 if (lseek(fd, 0, SEEK_SET) < 0)
 445                         return -errno;
 446         }
 447
 448         if (n < size) {
 449                 p = realloc(buf, n + 1);
 450                 if (!p)
 451                         return -ENOMEM;
 452                 buf = TAKE_PTR(p);
 453         }
 454
 455         if (!ret_size) {
 456                 /* Safety check: if the caller doesn't want to know the size of what we
 457                  * just read it will rely on the trailing NUL byte. But if there's an
 458                  * embedded NUL byte, then we should refuse operation as otherwise
 459                  * there'd be ambiguity about what we just read. */
 460
 461                 if (memchr(buf, 0, n))
 462                         return -EBADMSG;
 463         } else
 464                 *ret_size = n;
 465
 466         buf[n] = 0;
 467         *ret_contents = TAKE_PTR(buf);
 468
 469         return 0;
 470 }
 471
 472 int read_full_stream_full(
 473                 FILE *f,
 474                 const char *filename,
 475                 uint64_t offset,
 476                 size_t size,
 477                 ReadFullFileFlags flags,
 478                 char **ret_contents,
 479                 size_t *ret_size) {
 480
 481         _cleanup_free_ char *buf = NULL;
 482         size_t n, n_next, l;
 483         int fd, r;
 484
 485         assert(f);
 486         assert(ret_contents);
 487         assert(!FLAGS_SET(flags, READ_FULL_FILE_UNBASE64 | READ_FULL_FILE_UNHEX));
 488
 489         if (offset != UINT64_MAX && offset > LONG_MAX)
 490                 return -ERANGE;
 491
 492         n_next = size != SIZE_MAX ? size : LINE_MAX; /* Start size */
 493
 494         fd = fileno(f);
 495         if (fd >= 0) { /* If the FILE* object is backed by an fd (as opposed to memory or such, see
 496                         * fmemopen()), let's optimize our buffering */
 497                 struct stat st;
 498
 499                 if (fstat(fd, &st) < 0)
 500                         return -errno;
 501
 502                 if (S_ISREG(st.st_mode)) {
 503                         if (size == SIZE_MAX) {
 504                                 uint64_t rsize =
 505                                         LESS_BY((uint64_t) st.st_size, offset == UINT64_MAX ? 0 : offset);
 506
 507                                 /* Safety check */
 508                                 if (rsize > READ_FULL_BYTES_MAX)
 509                                         return -E2BIG;
 510
 511                                 /* Start with the right file size. Note that we increase the size to read
 512                                  * here by one, so that the first read attempt already makes us notice the
 513                                  * EOF. If the reported size of the file is zero, we avoid this logic
 514                                  * however, since quite likely it might be a virtual file in procfs that all
 515                                  * report a zero file size. */
 516                                 if (st.st_size > 0)
 517                                         n_next = rsize + 1;
 518                         }
 519
 520                         if (flags & READ_FULL_FILE_WARN_WORLD_READABLE)
 521                                 (void) warn_file_is_world_accessible(filename, &st, NULL, 0);
 522                 }
 523         }
 524
 525         if (offset != UINT64_MAX && fseek(f, offset, SEEK_SET) < 0)
 526                 return -errno;
 527
 528         n = l = 0;
 529         for (;;) {
 530                 char *t;
 531                 size_t k;
 532
 533                 if (flags & READ_FULL_FILE_SECURE) {
 534                         t = malloc(n_next + 1);
 535                         if (!t) {
 536                                 r = -ENOMEM;
 537                                 goto finalize;
 538                         }
 539                         memcpy_safe(t, buf, n);
 540                         explicit_bzero_safe(buf, n);
 541                         buf = mfree(buf);
 542                 } else {
 543                         t = realloc(buf, n_next + 1);
 544                         if (!t)
 545                                 return -ENOMEM;
 546                 }
 547
 548                 buf = t;
 549                 n = n_next;
 550
 551                 errno = 0;
 552                 k = fread(buf + l, 1, n - l, f);
 553
 554                 assert(k <= n - l);
 555                 l += k;
 556
 557                 if (ferror(f)) {
 558                         r = errno_or_else(EIO);
 559                         goto finalize;
 560                 }
 561                 if (feof(f))
 562                         break;
 563
 564                 if (size != SIZE_MAX) { /* If we got asked to read some specific size, we already sized the buffer right, hence leave */
 565                         assert(l == size);
 566                         break;
 567                 }
 568
 569                 assert(k > 0); /* we can't have read zero bytes because that would have been EOF */
 570
 571                 /* Safety check */
 572                 if (n >= READ_FULL_BYTES_MAX) {
 573                         r = -E2BIG;
 574                         goto finalize;
 575                 }
 576
 577                 n_next = MIN(n * 2, READ_FULL_BYTES_MAX);
 578         }
 579
 580         if (flags & (READ_FULL_FILE_UNBASE64 | READ_FULL_FILE_UNHEX)) {
 581                 _cleanup_free_ void *decoded = NULL;
 582                 size_t decoded_size;
 583
 584                 buf[l++] = 0;
 585                 if (flags & READ_FULL_FILE_UNBASE64)
 586                         r = unbase64mem_full(buf, l, flags & READ_FULL_FILE_SECURE, &decoded, &decoded_size);
 587                 else
 588                         r = unhexmem_full(buf, l, flags & READ_FULL_FILE_SECURE, &decoded, &decoded_size);
 589                 if (r < 0)
 590                         goto finalize;
 591
 592                 if (flags & READ_FULL_FILE_SECURE)
 593                         explicit_bzero_safe(buf, n);
 594                 free_and_replace(buf, decoded);
 595                 n = l = decoded_size;
 596         }
 597
 598         if (!ret_size) {
 599                 /* Safety check: if the caller doesn't want to know the size of what we just read it will rely on the
 600                  * trailing NUL byte. But if there's an embedded NUL byte, then we should refuse operation as otherwise
 601                  * there'd be ambiguity about what we just read. */
 602
 603                 if (memchr(buf, 0, l)) {
 604                         r = -EBADMSG;
 605                         goto finalize;
 606                 }
 607         }
 608
 609         buf[l] = 0;
 610         *ret_contents = TAKE_PTR(buf);
 611
 612         if (ret_size)
 613                 *ret_size = l;
 614
 615         return 0;
 616
 617 finalize:
 618         if (flags & READ_FULL_FILE_SECURE)
 619                 explicit_bzero_safe(buf, n);
 620
 621         return r;
 622 }
 623
 624 int read_full_file_full(
 625                 int dir_fd,
 626                 const char *filename,
 627                 uint64_t offset,
 628                 size_t size,
 629                 ReadFullFileFlags flags,
 630                 const char *bind_name,
 631                 char **ret_contents,
 632                 size_t *ret_size) {
 633
 634         _cleanup_fclose_ FILE *f = NULL;
 635         int r;
 636
 637         assert(filename);
 638         assert(ret_contents);
 639
 640         r = xfopenat(dir_fd, filename, "re", 0, &f);
 641         if (r < 0) {
 642                 _cleanup_close_ int dfd = -1, sk = -1;
 643                 union sockaddr_union sa;
 644
 645                 /* ENXIO is what Linux returns if we open a node that is an AF_UNIX socket */
 646                 if (r != -ENXIO)
 647                         return r;
 648
 649                 /* If this is enabled, let's try to connect to it */
 650                 if (!FLAGS_SET(flags, READ_FULL_FILE_CONNECT_SOCKET))
 651                         return -ENXIO;
 652
 653                 /* Seeking is not supported on AF_UNIX sockets */
 654                 if (offset != UINT64_MAX)
 655                         return -ESPIPE;
 656
 657                 if (dir_fd == AT_FDCWD)
 658                         r = sockaddr_un_set_path(&sa.un, filename);
 659                 else {
 660                         char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
 661
 662                         /* If we shall operate relative to some directory, then let's use O_PATH first to
 663                          * open the socket inode, and then connect to it via /proc/self/fd/. We have to do
 664                          * this since there's not connectat() that takes a directory fd as first arg. */
 665
 666                         dfd = openat(dir_fd, filename, O_PATH|O_CLOEXEC);
 667                         if (dfd < 0)
 668                                 return -errno;
 669
 670                         xsprintf(procfs_path, "/proc/self/fd/%i", dfd);
 671                         r = sockaddr_un_set_path(&sa.un, procfs_path);
 672                 }
 673                 if (r < 0)
 674                         return r;
 675
 676                 sk = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0);
 677                 if (sk < 0)
 678                         return -errno;
 679
 680                 if (bind_name) {
 681                         /* If the caller specified a socket name to bind to, do so before connecting. This is
 682                          * useful to communicate some minor, short meta-information token from the client to
 683                          * the server. */
 684                         union sockaddr_union bsa;
 685
 686                         r = sockaddr_un_set_path(&bsa.un, bind_name);
 687                         if (r < 0)
 688                                 return r;
 689
 690                         if (bind(sk, &bsa.sa, r) < 0)
 691                                 return r;
 692                 }
 693
 694                 if (connect(sk, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0)
 695                         return errno == ENOTSOCK ? -ENXIO : -errno; /* propagate original error if this is
 696                                                                      * not a socket after all */
 697
 698                 if (shutdown(sk, SHUT_WR) < 0)
 699                         return -errno;
 700
 701                 f = fdopen(sk, "r");
 702                 if (!f)
 703                         return -errno;
 704
 705                 TAKE_FD(sk);
 706         }
 707
 708         (void) __fsetlocking(f, FSETLOCKING_BYCALLER);
 709
 710         return read_full_stream_full(f, filename, offset, size, flags, ret_contents, ret_size);
 711 }
 712
 713 int executable_is_script(const char *path, char **interpreter) {
 714         _cleanup_free_ char *line = NULL;
 715         size_t len;
 716         char *ans;
 717         int r;
 718
 719         assert(path);
 720
 721         r = read_one_line_file(path, &line);
 722         if (r == -ENOBUFS) /* First line overly long? if so, then it's not a script */
 723                 return 0;
 724         if (r < 0)
 725                 return r;
 726
 727         if (!startswith(line, "#!"))
 728                 return 0;
 729
 730         ans = strstrip(line + 2);
 731         len = strcspn(ans, " \t");
 732
 733         if (len == 0)
 734                 return 0;
 735
 736         ans = strndup(ans, len);
 737         if (!ans)
 738                 return -ENOMEM;
 739
 740         *interpreter = ans;
 741         return 1;
 742 }
 743
 744 /**
 745  * Retrieve one field from a file like /proc/self/status.  pattern
 746  * should not include whitespace or the delimiter (':'). pattern matches only
 747  * the beginning of a line. Whitespace before ':' is skipped. Whitespace and
 748  * zeros after the ':' will be skipped. field must be freed afterwards.
 749  * terminator specifies the terminating characters of the field value (not
 750  * included in the value).
 751  */
 752 int get_proc_field(const char *filename, const char *pattern, const char *terminator, char **field) {
 753         _cleanup_free_ char *status = NULL;
 754         char *t, *f;
 755         size_t len;
 756         int r;
 757
 758         assert(terminator);
 759         assert(filename);
 760         assert(pattern);
 761         assert(field);
 762
 763         r = read_full_virtual_file(filename, &status, NULL);
 764         if (r < 0)
 765                 return r;
 766
 767         t = status;
 768
 769         do {
 770                 bool pattern_ok;
 771
 772                 do {
 773                         t = strstr(t, pattern);
 774                         if (!t)
 775                                 return -ENOENT;
 776
 777                         /* Check that pattern occurs in beginning of line. */
 778                         pattern_ok = (t == status || t[-1] == '\n');
 779
 780                         t += strlen(pattern);
 781
 782                 } while (!pattern_ok);
 783
 784                 t += strspn(t, " \t");
 785                 if (!*t)
 786                         return -ENOENT;
 787
 788         } while (*t != ':');
 789
 790         t++;
 791
 792         if (*t) {
 793                 t += strspn(t, " \t");
 794
 795                 /* Also skip zeros, because when this is used for
 796                  * capabilities, we don't want the zeros. This way the
 797                  * same capability set always maps to the same string,
 798                  * irrespective of the total capability set size. For
 799                  * other numbers it shouldn't matter. */
 800                 t += strspn(t, "0");
 801                 /* Back off one char if there's nothing but whitespace
 802                    and zeros */
 803                 if (!*t || isspace(*t))
 804                         t--;
 805         }
 806
 807         len = strcspn(t, terminator);
 808
 809         f = strndup(t, len);
 810         if (!f)
 811                 return -ENOMEM;
 812
 813         *field = f;
 814         return 0;
 815 }
 816
 817 DIR *xopendirat(int fd, const char *name, int flags) {
 818         int nfd;
 819         DIR *d;
 820
 821         assert(!(flags & O_CREAT));
 822
 823         nfd = openat(fd, name, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|flags, 0);
 824         if (nfd < 0)
 825                 return NULL;
 826
 827         d = fdopendir(nfd);
 828         if (!d) {
 829                 safe_close(nfd);
 830                 return NULL;
 831         }
 832
 833         return d;
 834 }
 835
 836 static int mode_to_flags(const char *mode) {
 837         const char *p;
 838         int flags;
 839
 840         if ((p = startswith(mode, "r+")))
 841                 flags = O_RDWR;
 842         else if ((p = startswith(mode, "r")))
 843                 flags = O_RDONLY;
 844         else if ((p = startswith(mode, "w+")))
 845                 flags = O_RDWR|O_CREAT|O_TRUNC;
 846         else if ((p = startswith(mode, "w")))
 847                 flags = O_WRONLY|O_CREAT|O_TRUNC;
 848         else if ((p = startswith(mode, "a+")))
 849                 flags = O_RDWR|O_CREAT|O_APPEND;
 850         else if ((p = startswith(mode, "a")))
 851                 flags = O_WRONLY|O_CREAT|O_APPEND;
 852         else
 853                 return -EINVAL;
 854
 855         for (; *p != 0; p++) {
 856
 857                 switch (*p) {
 858
 859                 case 'e':
 860                         flags |= O_CLOEXEC;
 861                         break;
 862
 863                 case 'x':
 864                         flags |= O_EXCL;
 865                         break;
 866
 867                 case 'm':
 868                         /* ignore this here, fdopen() might care later though */
 869                         break;
 870
 871                 case 'c': /* not sure what to do about this one */
 872                 default:
 873                         return -EINVAL;
 874                 }
 875         }
 876
 877         return flags;
 878 }
 879
 880 int xfopenat(int dir_fd, const char *path, const char *mode, int flags, FILE **ret) {
 881         FILE *f;
 882
 883         /* A combination of fopen() with openat() */
 884
 885         if (dir_fd == AT_FDCWD && flags == 0) {
 886                 f = fopen(path, mode);
 887                 if (!f)
 888                         return -errno;
 889         } else {
 890                 int fd, mode_flags;
 891
 892                 mode_flags = mode_to_flags(mode);
 893                 if (mode_flags < 0)
 894                         return mode_flags;
 895
 896                 fd = openat(dir_fd, path, mode_flags | flags);
 897                 if (fd < 0)
 898                         return -errno;
 899
 900                 f = fdopen(fd, mode);
 901                 if (!f) {
 902                         safe_close(fd);
 903                         return -errno;
 904                 }
 905         }
 906
 907         *ret = f;
 908         return 0;
 909 }
 910
 911 static int search_and_fopen_internal(const char *path, const char *mode, const char *root, char **search, FILE **_f) {
 912         char **i;
 913
 914         assert(path);
 915         assert(mode);
 916         assert(_f);
 917
 918         if (!path_strv_resolve_uniq(search, root))
 919                 return -ENOMEM;
 920
 921         STRV_FOREACH(i, search) {
 922                 _cleanup_free_ char *p = NULL;
 923                 FILE *f;
 924
 925                 p = path_join(root, *i, path);
 926                 if (!p)
 927                         return -ENOMEM;
 928
 929                 f = fopen(p, mode);
 930                 if (f) {
 931                         *_f = f;
 932                         return 0;
 933                 }
 934
 935                 if (errno != ENOENT)
 936                         return -errno;
 937         }
 938
 939         return -ENOENT;
 940 }
 941
 942 int search_and_fopen(const char *path, const char *mode, const char *root, const char **search, FILE **_f) {
 943         _cleanup_strv_free_ char **copy = NULL;
 944
 945         assert(path);
 946         assert(mode);
 947         assert(_f);
 948
 949         if (path_is_absolute(path)) {
 950                 FILE *f;
 951
 952                 f = fopen(path, mode);
 953                 if (f) {
 954                         *_f = f;
 955                         return 0;
 956                 }
 957
 958                 return -errno;
 959         }
 960
 961         copy = strv_copy((char**) search);
 962         if (!copy)
 963                 return -ENOMEM;
 964
 965         return search_and_fopen_internal(path, mode, root, copy, _f);
 966 }
 967
 968 int search_and_fopen_nulstr(const char *path, const char *mode, const char *root, const char *search, FILE **_f) {
 969         _cleanup_strv_free_ char **s = NULL;
 970
 971         if (path_is_absolute(path)) {
 972                 FILE *f;
 973
 974                 f = fopen(path, mode);
 975                 if (f) {
 976                         *_f = f;
 977                         return 0;
 978                 }
 979
 980                 return -errno;
 981         }
 982
 983         s = strv_split_nulstr(search);
 984         if (!s)
 985                 return -ENOMEM;
 986
 987         return search_and_fopen_internal(path, mode, root, s, _f);
 988 }
 989
 990 int chase_symlinks_and_fopen_unlocked(
 991                 const char *path,
 992                 const char *root,
 993                 unsigned chase_flags,
 994                 const char *open_flags,
 995                 FILE **ret_file,
 996                 char **ret_path) {
 997
 998         _cleanup_close_ int fd = -1;
 999         _cleanup_free_ char *final_path = NULL;
1000         int mode_flags, r;
1001         FILE *f;
1002
1003         assert(path);
1004         assert(open_flags);
1005         assert(ret_file);
1006
1007         mode_flags = mode_to_flags(open_flags);
1008         if (mode_flags < 0)
1009                 return mode_flags;
1010
1011         fd = chase_symlinks_and_open(path, root, chase_flags, mode_flags, ret_path ? &final_path : NULL);
1012         if (fd < 0)
1013                 return fd;
1014
1015         r = fdopen_unlocked(fd, open_flags, &f);
1016         if (r < 0)
1017                 return r;
1018         TAKE_FD(fd);
1019
1020         *ret_file = f;
1021         if (ret_path)
1022                 *ret_path = TAKE_PTR(final_path);
1023         return 0;
1024 }
1025
1026 int fflush_and_check(FILE *f) {
1027         assert(f);
1028
1029         errno = 0;
1030         fflush(f);
1031
1032         if (ferror(f))
1033                 return errno_or_else(EIO);
1034
1035         return 0;
1036 }
1037
1038 int fflush_sync_and_check(FILE *f) {
1039         int r, fd;
1040
1041         assert(f);
1042
1043         r = fflush_and_check(f);
1044         if (r < 0)
1045                 return r;
1046
1047         /* Not all file streams have an fd associated (think: fmemopen()), let's handle this gracefully and
1048          * assume that in that case we need no explicit syncing */
1049         fd = fileno(f);
1050         if (fd < 0)
1051                 return 0;
1052
1053         if (fsync(fd) < 0)
1054                 return -errno;
1055
1056         r = fsync_directory_of_file(fd);
1057         if (r < 0)
1058                 return r;
1059
1060         return 0;
1061 }
1062
1063 int write_timestamp_file_atomic(const char *fn, usec_t n) {
1064         char ln[DECIMAL_STR_MAX(n)+2];
1065
1066         /* Creates a "timestamp" file, that contains nothing but a
1067          * usec_t timestamp, formatted in ASCII. */
1068
1069         if (n <= 0 || n >= USEC_INFINITY)
1070                 return -ERANGE;
1071
1072         xsprintf(ln, USEC_FMT "\n", n);
1073
1074         return write_string_file(fn, ln, WRITE_STRING_FILE_CREATE|WRITE_STRING_FILE_ATOMIC);
1075 }
1076
1077 int read_timestamp_file(const char *fn, usec_t *ret) {
1078         _cleanup_free_ char *ln = NULL;
1079         uint64_t t;
1080         int r;
1081
1082         r = read_one_line_file(fn, &ln);
1083         if (r < 0)
1084                 return r;
1085
1086         r = safe_atou64(ln, &t);
1087         if (r < 0)
1088                 return r;
1089
1090         if (t <= 0 || t >= (uint64_t) USEC_INFINITY)
1091                 return -ERANGE;
1092
1093         *ret = (usec_t) t;
1094         return 0;
1095 }
1096
1097 int fputs_with_space(FILE *f, const char *s, const char *separator, bool *space) {
1098         int r;
1099
1100         assert(s);
1101
1102         /* Outputs the specified string with fputs(), but optionally prefixes it with a separator. The *space parameter
1103          * when specified shall initially point to a boolean variable initialized to false. It is set to true after the
1104          * first invocation. This call is supposed to be use in loops, where a separator shall be inserted between each
1105          * element, but not before the first one. */
1106
1107         if (!f)
1108                 f = stdout;
1109
1110         if (space) {
1111                 if (!separator)
1112                         separator = " ";
1113
1114                 if (*space) {
1115                         r = fputs(separator, f);
1116                         if (r < 0)
1117                                 return r;
1118                 }
1119
1120                 *space = true;
1121         }
1122
1123         return fputs(s, f);
1124 }
1125
1126 /* A bitmask of the EOL markers we know */
1127 typedef enum EndOfLineMarker {
1128         EOL_NONE     = 0,
1129         EOL_ZERO     = 1 << 0,  /* \0 (aka NUL) */
1130         EOL_TEN      = 1 << 1,  /* \n (aka NL, aka LF)  */
1131         EOL_THIRTEEN = 1 << 2,  /* \r (aka CR)  */
1132 } EndOfLineMarker;
1133
1134 static EndOfLineMarker categorize_eol(char c, ReadLineFlags flags) {
1135
1136         if (!IN_SET(flags, READ_LINE_ONLY_NUL)) {
1137                 if (c == '\n')
1138                         return EOL_TEN;
1139                 if (c == '\r')
1140                         return EOL_THIRTEEN;
1141         }
1142
1143         if (c == '\0')
1144                 return EOL_ZERO;
1145
1146         return EOL_NONE;
1147 }
1148
1149 DEFINE_TRIVIAL_CLEANUP_FUNC(FILE*, funlockfile);
1150
1151 int read_line_full(FILE *f, size_t limit, ReadLineFlags flags, char **ret) {
1152         size_t n = 0, allocated = 0, count = 0;
1153         _cleanup_free_ char *buffer = NULL;
1154         int r;
1155
1156         assert(f);
1157
1158         /* Something like a bounded version of getline().
1159          *
1160          * Considers EOF, \n, \r and \0 end of line delimiters (or combinations of these), and does not include these
1161          * delimiters in the string returned. Specifically, recognizes the following combinations of markers as line
1162          * endings:
1163          *
1164          *     • \n        (UNIX)
1165          *     • \r        (old MacOS)
1166          *     • \0        (C strings)
1167          *     • \n\0
1168          *     • \r\0
1169          *     • \r\n      (Windows)
1170          *     • \n\r
1171          *     • \r\n\0
1172          *     • \n\r\0
1173          *
1174          * Returns the number of bytes read from the files (i.e. including delimiters — this hence usually differs from
1175          * the number of characters in the returned string). When EOF is hit, 0 is returned.
1176          *
1177          * The input parameter limit is the maximum numbers of characters in the returned string, i.e. excluding
1178          * delimiters. If the limit is hit we fail and return -ENOBUFS.
1179          *
1180          * If a line shall be skipped ret may be initialized as NULL. */
1181
1182         if (ret) {
1183                 if (!GREEDY_REALLOC(buffer, allocated, 1))
1184                         return -ENOMEM;
1185         }
1186
1187         {
1188                 _unused_ _cleanup_(funlockfilep) FILE *flocked = f;
1189                 EndOfLineMarker previous_eol = EOL_NONE;
1190                 flockfile(f);
1191
1192                 for (;;) {
1193                         EndOfLineMarker eol;
1194                         char c;
1195
1196                         if (n >= limit)
1197                                 return -ENOBUFS;
1198
1199                         if (count >= INT_MAX) /* We couldn't return the counter anymore as "int", hence refuse this */
1200                                 return -ENOBUFS;
1201
1202                         r = safe_fgetc(f, &c);
1203                         if (r < 0)
1204                                 return r;
1205                         if (r == 0) /* EOF is definitely EOL */
1206                                 break;
1207
1208                         eol = categorize_eol(c, flags);
1209
1210                         if (FLAGS_SET(previous_eol, EOL_ZERO) ||
1211                             (eol == EOL_NONE && previous_eol != EOL_NONE) ||
1212                             (eol != EOL_NONE && (previous_eol & eol) != 0)) {
1213                                 /* Previous char was a NUL? This is not an EOL, but the previous char was? This type of
1214                                  * EOL marker has been seen right before?  In either of these three cases we are
1215                                  * done. But first, let's put this character back in the queue. (Note that we have to
1216                                  * cast this to (unsigned char) here as ungetc() expects a positive 'int', and if we
1217                                  * are on an architecture where 'char' equals 'signed char' we need to ensure we don't
1218                                  * pass a negative value here. That said, to complicate things further ungetc() is
1219                                  * actually happy with most negative characters and implicitly casts them back to
1220                                  * positive ones as needed, except for \xff (aka -1, aka EOF), which it refuses. What a
1221                                  * godawful API!) */
1222                                 assert_se(ungetc((unsigned char) c, f) != EOF);
1223                                 break;
1224                         }
1225
1226                         count++;
1227
1228                         if (eol != EOL_NONE) {
1229                                 /* If we are on a tty, we can't shouldn't wait for more input, because that
1230                                  * generally means waiting for the user, interactively. In the case of a TTY
1231                                  * we expect only \n as the single EOL marker, so we are in the lucky
1232                                  * position that there is no need to wait. We check this condition last, to
1233                                  * avoid isatty() check if not necessary. */
1234
1235                                 if ((flags & (READ_LINE_IS_A_TTY|READ_LINE_NOT_A_TTY)) == 0) {
1236                                         int fd;
1237
1238                                         fd = fileno(f);
1239                                         if (fd < 0) /* Maybe an fmemopen() stream? Handle this gracefully,
1240                                                      * and don't call isatty() on an invalid fd */
1241                                                 flags |= READ_LINE_NOT_A_TTY;
1242                                         else
1243                                                 flags |= isatty(fd) ? READ_LINE_IS_A_TTY : READ_LINE_NOT_A_TTY;
1244                                 }
1245                                 if (FLAGS_SET(flags, READ_LINE_IS_A_TTY))
1246                                         break;
1247                         }
1248
1249                         if (eol != EOL_NONE) {
1250                                 previous_eol |= eol;
1251                                 continue;
1252                         }
1253
1254                         if (ret) {
1255                                 if (!GREEDY_REALLOC(buffer, allocated, n + 2))
1256                                         return -ENOMEM;
1257
1258                                 buffer[n] = c;
1259                         }
1260
1261                         n++;
1262                 }
1263         }
1264
1265         if (ret) {
1266                 buffer[n] = 0;
1267
1268                 *ret = TAKE_PTR(buffer);
1269         }
1270
1271         return (int) count;
1272 }
1273
1274 int safe_fgetc(FILE *f, char *ret) {
1275         int k;
1276
1277         assert(f);
1278
1279         /* A safer version of plain fgetc(): let's propagate the error that happened while reading as such, and
1280          * separate the EOF condition from the byte read, to avoid those confusion signed/unsigned issues fgetc()
1281          * has. */
1282
1283         errno = 0;
1284         k = fgetc(f);
1285         if (k == EOF) {
1286                 if (ferror(f))
1287                         return errno_or_else(EIO);
1288
1289                 if (ret)
1290                         *ret = 0;
1291
1292                 return 0;
1293         }
1294
1295         if (ret)
1296                 *ret = k;
1297
1298         return 1;
1299 }
1300
1301 int warn_file_is_world_accessible(const char *filename, struct stat *st, const char *unit, unsigned line) {
1302         struct stat _st;
1303
1304         if (!filename)
1305                 return 0;
1306
1307         if (!st) {
1308                 if (stat(filename, &_st) < 0)
1309                         return -errno;
1310                 st = &_st;
1311         }
1312
1313         if ((st->st_mode & S_IRWXO) == 0)
1314                 return 0;
1315
1316         if (unit)
1317                 log_syntax(unit, LOG_WARNING, filename, line, 0,
1318                            "%s has %04o mode that is too permissive, please adjust the ownership and access mode.",
1319                            filename, st->st_mode & 07777);
1320         else
1321                 log_warning("%s has %04o mode that is too permissive, please adjust the ownership and access mode.",
1322                             filename, st->st_mode & 07777);
1323         return 0;
1324 }
1325
1326 int sync_rights(int from, int to) {
1327         struct stat st;
1328
1329         if (fstat(from, &st) < 0)
1330                 return -errno;
1331
1332         return fchmod_and_chown(to, st.st_mode & 07777, st.st_uid, st.st_gid);
1333 }
1334
1335 int rename_and_apply_smack_floor_label(const char *from, const char *to) {
1336         int r = 0;
1337         if (rename(from, to) < 0)
1338                 return -errno;
1339
1340 #ifdef SMACK_RUN_LABEL
1341         r = mac_smack_apply(to, SMACK_ATTR_ACCESS, SMACK_FLOOR_LABEL);
1342         if (r < 0)
1343                 return r;
1344 #endif
1345         return r;
1346 }