src/shared/base-filesystem.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   This file is part of systemd.
   4
   5   Copyright 2014 Kay Sievers
   6 ***/
   7
   8 #include <errno.h>
   9 #include <fcntl.h>
  10 #include <stdbool.h>
  11 #include <stdlib.h>
  12 #include <sys/stat.h>
  13 #include <syslog.h>
  14 #include <unistd.h>
  15
  16 #include "alloc-util.h"
  17 #include "base-filesystem.h"
  18 #include "fd-util.h"
  19 #include "log.h"
  20 #include "macro.h"
  21 #include "string-util.h"
  22 #include "umask-util.h"
  23 #include "user-util.h"
  24 #include "util.h"
  25
  26 typedef struct BaseFilesystem {
  27         const char *dir;
  28         mode_t mode;
  29         const char *target;
  30         const char *exists;
  31         bool ignore_failure;
  32 } BaseFilesystem;
  33
  34 static const BaseFilesystem table[] = {
  35         { "bin",      0, "usr/bin\0",                  NULL },
  36         { "lib",      0, "usr/lib\0",                  NULL },
  37         { "root",  0755, NULL,                         NULL, true },
  38         { "sbin",     0, "usr/sbin\0",                 NULL },
  39         { "usr",   0755, NULL,                         NULL },
  40         { "var",   0755, NULL,                         NULL },
  41         { "etc",   0755, NULL,                         NULL },
  42         { "proc",  0755, NULL,                         NULL, true },
  43         { "sys",   0755, NULL,                         NULL, true },
  44         { "dev",   0755, NULL,                         NULL, true },
  45 #if defined(__i386__) || defined(__x86_64__)
  46         { "lib64",    0, "usr/lib/x86_64-linux-gnu\0"
  47                          "usr/lib64\0",                "ld-linux-x86-64.so.2" },
  48 #endif
  49 };
  50
  51 int base_filesystem_create(const char *root, uid_t uid, gid_t gid) {
  52         _cleanup_close_ int fd = -1;
  53         unsigned i;
  54         int r = 0;
  55
  56         fd = open(root, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW);
  57         if (fd < 0)
  58                 return log_error_errno(errno, "Failed to open root file system: %m");
  59
  60         for (i = 0; i < ELEMENTSOF(table); i ++) {
  61                 if (faccessat(fd, table[i].dir, F_OK, AT_SYMLINK_NOFOLLOW) >= 0)
  62                         continue;
  63
  64                 if (table[i].target) {
  65                         const char *target = NULL, *s;
  66
  67                         /* check if one of the targets exists */
  68                         NULSTR_FOREACH(s, table[i].target) {
  69                                 if (faccessat(fd, s, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
  70                                         continue;
  71
  72                                 /* check if a specific file exists at the target path */
  73                                 if (table[i].exists) {
  74                                         _cleanup_free_ char *p = NULL;
  75
  76                                         p = strjoin(s, "/", table[i].exists);
  77                                         if (!p)
  78                                                 return log_oom();
  79
  80                                         if (faccessat(fd, p, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
  81                                                 continue;
  82                                 }
  83
  84                                 target = s;
  85                                 break;
  86                         }
  87
  88                         if (!target)
  89                                 continue;
  90
  91                         r = symlinkat(target, fd, table[i].dir);
  92                         if (r < 0 && errno != EEXIST)
  93                                 return log_error_errno(errno, "Failed to create symlink at %s/%s: %m", root, table[i].dir);
  94
  95                         if (uid_is_valid(uid) || gid_is_valid(gid)) {
  96                                 if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)
  97                                         return log_error_errno(errno, "Failed to chown symlink at %s/%s: %m", root, table[i].dir);
  98                         }
  99
 100                         continue;
 101                 }
 102
 103                 RUN_WITH_UMASK(0000)
 104                         r = mkdirat(fd, table[i].dir, table[i].mode);
 105                 if (r < 0 && errno != EEXIST) {
 106                         log_full_errno(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 (!table[i].ignore_failure)
 110                                 return -errno;
 111
 112                         continue;
 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
 121         return 0;
 122 }