src/shared/base-filesystem.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   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 "path-util.h"
  18 #include "string-util.h"
  19 #include "umask-util.h"
  20 #include "user-util.h"
  21
  22 typedef struct BaseFilesystem {
  23         const char *dir;
  24         mode_t mode;
  25         const char *target;
  26         const char *exists;
  27         bool ignore_failure;
  28 } BaseFilesystem;
  29
  30 static const BaseFilesystem table[] = {
  31         { "bin",      0, "usr/bin\0",                  NULL },
  32         { "lib",      0, "usr/lib\0",                  NULL },
  33         { "root",  0755, NULL,                         NULL, true },
  34         { "sbin",     0, "usr/sbin\0",                 NULL },
  35         { "usr",   0755, NULL,                         NULL },
  36         { "var",   0755, NULL,                         NULL },
  37         { "etc",   0755, NULL,                         NULL },
  38         { "proc",  0755, NULL,                         NULL, true },
  39         { "sys",   0755, NULL,                         NULL, true },
  40         { "dev",   0755, NULL,                         NULL, true },
  41 #if defined(__i386__) || defined(__x86_64__)
  42         { "lib64",    0, "usr/lib/x86_64-linux-gnu\0"
  43                          "usr/lib64\0",                "ld-linux-x86-64.so.2" },
  44 #endif
  45 };
  46
  47 int base_filesystem_create(const char *root, uid_t uid, gid_t gid) {
  48         _cleanup_close_ int fd = -1;
  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 (size_t 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 = path_join(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                         if (symlinkat(target, fd, table[i].dir) < 0) {
  87                                 log_full_errno(IN_SET(errno, EEXIST, EROFS) || table[i].ignore_failure ? LOG_DEBUG : LOG_ERR, errno,
  88                                                "Failed to create symlink at %s/%s: %m", root, table[i].dir);
  89
  90                                 if (IN_SET(errno, EEXIST, EROFS) || table[i].ignore_failure)
  91                                         continue;
  92
  93                                 return -errno;
  94                         }
  95
  96                         if (uid_is_valid(uid) || gid_is_valid(gid))
  97                                 if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)
  98                                         return log_error_errno(errno, "Failed to chown symlink at %s/%s: %m", root, table[i].dir);
  99
 100                         continue;
 101                 }
 102
 103                 RUN_WITH_UMASK(0000)
 104                         r = mkdirat(fd, table[i].dir, table[i].mode);
 105                 if (r < 0) {
 106                         log_full_errno(IN_SET(errno, EEXIST, EROFS) || table[i].ignore_failure ? LOG_DEBUG : LOG_ERR, errno,
 107                                        "Failed to create directory at %s/%s: %m", root, table[i].dir);
 108
 109                         if (IN_SET(errno, EEXIST, EROFS) || table[i].ignore_failure)
 110                                 continue;
 111
 112                         return -errno;
 113                 }
 114
 115                 if (uid != UID_INVALID || gid != UID_INVALID)
 116                         if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)
 117                                 return log_error_errno(errno, "Failed to chown directory at %s/%s: %m", root, table[i].dir);
 118         }
 119
 120         return 0;
 121 }