src/shared/base-filesystem.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   Copyright © 2014 Kay Sievers
   4 ***/
   5
   6 #include <errno.h>
   7 #include <fcntl.h>
   8 #include <stdbool.h>
   9 #include <stdlib.h>
  10 #include <sys/stat.h>
  11 #include <syslog.h>
  12 #include <unistd.h>
  13
  14 #include "alloc-util.h"
  15 #include "base-filesystem.h"
  16 #include "fd-util.h"
  17 #include "log.h"
  18 #include "macro.h"
  19 #include "string-util.h"
  20 #include "umask-util.h"
  21 #include "user-util.h"
  22 #include "util.h"
  23
  24 typedef struct BaseFilesystem {
  25         const char *dir;
  26         mode_t mode;
  27         const char *target;
  28         const char *exists;
  29         bool ignore_failure;
  30 } BaseFilesystem;
  31
  32 static const BaseFilesystem table[] = {
  33         { "bin",      0, "usr/bin\0",                  NULL },
  34         { "lib",      0, "usr/lib\0",                  NULL },
  35         { "root",  0755, NULL,                         NULL, true },
  36         { "sbin",     0, "usr/sbin\0",                 NULL },
  37         { "usr",   0755, NULL,                         NULL },
  38         { "var",   0755, NULL,                         NULL },
  39         { "etc",   0755, NULL,                         NULL },
  40         { "proc",  0755, NULL,                         NULL, true },
  41         { "sys",   0755, NULL,                         NULL, true },
  42         { "dev",   0755, NULL,                         NULL, true },
  43 #if defined(__i386__) || defined(__x86_64__)
  44         { "lib64",    0, "usr/lib/x86_64-linux-gnu\0"
  45                          "usr/lib64\0",                "ld-linux-x86-64.so.2" },
  46 #endif
  47 };
  48
  49 int base_filesystem_create(const char *root, uid_t uid, gid_t gid) {
  50         _cleanup_close_ int fd = -1;
  51         int r = 0;
  52         size_t i;
  53
  54         fd = open(root, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW);
  55         if (fd < 0)
  56                 return log_error_errno(errno, "Failed to open root file system: %m");
  57
  58         for (i = 0; i < ELEMENTSOF(table); i ++) {
  59                 if (faccessat(fd, table[i].dir, F_OK, AT_SYMLINK_NOFOLLOW) >= 0)
  60                         continue;
  61
  62                 if (table[i].target) {
  63                         const char *target = NULL, *s;
  64
  65                         /* check if one of the targets exists */
  66                         NULSTR_FOREACH(s, table[i].target) {
  67                                 if (faccessat(fd, s, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
  68                                         continue;
  69
  70                                 /* check if a specific file exists at the target path */
  71                                 if (table[i].exists) {
  72                                         _cleanup_free_ char *p = NULL;
  73
  74                                         p = strjoin(s, "/", table[i].exists);
  75                                         if (!p)
  76                                                 return log_oom();
  77
  78                                         if (faccessat(fd, p, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
  79                                                 continue;
  80                                 }
  81
  82                                 target = s;
  83                                 break;
  84                         }
  85
  86                         if (!target)
  87                                 continue;
  88
  89                         r = symlinkat(target, fd, table[i].dir);
  90                         if (r < 0 && errno != EEXIST)
  91                                 return log_error_errno(errno, "Failed to create symlink at %s/%s: %m", root, table[i].dir);
  92
  93                         if (uid_is_valid(uid) || gid_is_valid(gid)) {
  94                                 if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)
  95                                         return log_error_errno(errno, "Failed to chown symlink at %s/%s: %m", root, table[i].dir);
  96                         }
  97
  98                         continue;
  99                 }
 100
 101                 RUN_WITH_UMASK(0000)
 102                         r = mkdirat(fd, table[i].dir, table[i].mode);
 103                 if (r < 0 && errno != EEXIST) {
 104                         log_full_errno(table[i].ignore_failure ? LOG_DEBUG : LOG_ERR, errno,
 105                                        "Failed to create directory at %s/%s: %m", root, table[i].dir);
 106
 107                         if (!table[i].ignore_failure)
 108                                 return -errno;
 109
 110                         continue;
 111                 }
 112
 113                 if (uid != UID_INVALID || gid != UID_INVALID) {
 114                         if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)
 115                                 return log_error_errno(errno, "Failed to chown directory at %s/%s: %m", root, table[i].dir);
 116                 }
 117         }
 118
 119         return 0;
 120 }