src/shared/base-filesystem.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <errno.h>
   4 #include <fcntl.h>
   5 #include <stdbool.h>
   6 #include <stdlib.h>
   7 #include <sys/stat.h>
   8 #include <syslog.h>
   9 #include <unistd.h>
  10
  11 #include "alloc-util.h"
  12 #include "base-filesystem.h"
  13 #include "fd-util.h"
  14 #include "log.h"
  15 #include "macro.h"
  16 #include "nulstr-util.h"
  17 #include "string-util.h"
  18 #include "umask-util.h"
  19 #include "user-util.h"
  20
  21 typedef struct BaseFilesystem {
  22         const char *dir;
  23         mode_t mode;
  24         const char *target;
  25         const char *exists;
  26         bool ignore_failure;
  27 } BaseFilesystem;
  28
  29 static const BaseFilesystem table[] = {
  30         { "bin",      0, "usr/bin\0",                  NULL },
  31         { "lib",      0, "usr/lib\0",                  NULL },
  32         { "root",  0755, NULL,                         NULL, true },
  33         { "sbin",     0, "usr/sbin\0",                 NULL },
  34         { "usr",   0755, NULL,                         NULL },
  35         { "var",   0755, NULL,                         NULL },
  36         { "etc",   0755, NULL,                         NULL },
  37         { "proc",  0755, NULL,                         NULL, true },
  38         { "sys",   0755, NULL,                         NULL, true },
  39         { "dev",   0755, NULL,                         NULL, true },
  40 #if defined(__i386__) || defined(__x86_64__)
  41         { "lib64",    0, "usr/lib/x86_64-linux-gnu\0"
  42                          "usr/lib64\0",                "ld-linux-x86-64.so.2" },
  43 #endif
  44 };
  45
  46 int base_filesystem_create(const char *root, uid_t uid, gid_t gid) {
  47         _cleanup_close_ int fd = -1;
  48         size_t i;
  49         int r;
  50
  51         fd = open(root, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW);
  52         if (fd < 0)
  53                 return log_error_errno(errno, "Failed to open root file system: %m");
  54
  55         for (i = 0; i < ELEMENTSOF(table); i ++) {
  56                 if (faccessat(fd, table[i].dir, F_OK, AT_SYMLINK_NOFOLLOW) >= 0)
  57                         continue;
  58
  59                 if (table[i].target) {
  60                         const char *target = NULL, *s;
  61
  62                         /* check if one of the targets exists */
  63                         NULSTR_FOREACH(s, table[i].target) {
  64                                 if (faccessat(fd, s, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
  65                                         continue;
  66
  67                                 /* check if a specific file exists at the target path */
  68                                 if (table[i].exists) {
  69                                         _cleanup_free_ char *p = NULL;
  70
  71                                         p = strjoin(s, "/", table[i].exists);
  72                                         if (!p)
  73                                                 return log_oom();
  74
  75                                         if (faccessat(fd, p, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
  76                                                 continue;
  77                                 }
  78
  79                                 target = s;
  80                                 break;
  81                         }
  82
  83                         if (!target)
  84                                 continue;
  85
  86                         r = symlinkat(target, fd, table[i].dir);
  87                         if (r < 0 && errno != EEXIST)
  88                                 return log_error_errno(errno, "Failed to create symlink at %s/%s: %m", root, table[i].dir);
  89
  90                         if (uid_is_valid(uid) || gid_is_valid(gid)) {
  91                                 if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)
  92                                         return log_error_errno(errno, "Failed to chown symlink at %s/%s: %m", root, table[i].dir);
  93                         }
  94
  95                         continue;
  96                 }
  97
  98                 RUN_WITH_UMASK(0000)
  99                         r = mkdirat(fd, table[i].dir, table[i].mode);
 100                 if (r < 0 && errno != EEXIST) {
 101                         log_full_errno(table[i].ignore_failure ? LOG_DEBUG : LOG_ERR, errno,
 102                                        "Failed to create directory at %s/%s: %m", root, table[i].dir);
 103
 104                         if (!table[i].ignore_failure)
 105                                 return -errno;
 106
 107                         continue;
 108                 }
 109
 110                 if (uid != UID_INVALID || gid != UID_INVALID) {
 111                         if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)
 112                                 return log_error_errno(errno, "Failed to chown directory at %s/%s: %m", root, table[i].dir);
 113                 }
 114         }
 115
 116         return 0;
 117 }