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 "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         size_t i;
  50         int r;
  51
  52         fd = open(root, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW);
  53         if (fd < 0)
  54                 return log_error_errno(errno, "Failed to open root file system: %m");
  55
  56         for (i = 0; i < ELEMENTSOF(table); i ++) {
  57                 if (faccessat(fd, table[i].dir, F_OK, AT_SYMLINK_NOFOLLOW) >= 0)
  58                         continue;
  59
  60                 if (table[i].target) {
  61                         const char *target = NULL, *s;
  62
  63                         /* check if one of the targets exists */
  64                         NULSTR_FOREACH(s, table[i].target) {
  65                                 if (faccessat(fd, s, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
  66                                         continue;
  67
  68                                 /* check if a specific file exists at the target path */
  69                                 if (table[i].exists) {
  70                                         _cleanup_free_ char *p = NULL;
  71
  72                                         p = path_join(s, table[i].exists);
  73                                         if (!p)
  74                                                 return log_oom();
  75
  76                                         if (faccessat(fd, p, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
  77                                                 continue;
  78                                 }
  79
  80                                 target = s;
  81                                 break;
  82                         }
  83
  84                         if (!target)
  85                                 continue;
  86
  87                         if (symlinkat(target, fd, table[i].dir) < 0) {
  88                                 log_full_errno(IN_SET(errno, EEXIST, EROFS) || table[i].ignore_failure ? LOG_DEBUG : LOG_ERR, errno,
  89                                                "Failed to create symlink at %s/%s: %m", root, table[i].dir);
  90
  91                                 if (IN_SET(errno, EEXIST, EROFS) || table[i].ignore_failure)
  92                                         continue;
  93
  94                                 return -errno;
  95                         }
  96
  97                         if (uid_is_valid(uid) || gid_is_valid(gid)) {
  98                                 if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)
  99                                         return log_error_errno(errno, "Failed to chown symlink at %s/%s: %m", root, table[i].dir);
 100                         }
 101
 102                         continue;
 103                 }
 104
 105                 RUN_WITH_UMASK(0000)
 106                         r = mkdirat(fd, table[i].dir, table[i].mode);
 107                 if (r < 0) {
 108                         log_full_errno(IN_SET(errno, EEXIST, EROFS) || table[i].ignore_failure ? LOG_DEBUG : LOG_ERR, errno,
 109                                        "Failed to create directory at %s/%s: %m", root, table[i].dir);
 110
 111                         if (IN_SET(errno, EEXIST, EROFS) || table[i].ignore_failure)
 112                                 continue;
 113
 114                         return -errno;
 115                 }
 116
 117                 if (uid != UID_INVALID || gid != UID_INVALID) {
 118                         if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)
 119                                 return log_error_errno(errno, "Failed to chown directory at %s/%s: %m", root, table[i].dir);
 120                 }
 121         }
 122
 123         return 0;
 124 }