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   systemd is free software; you can redistribute it and/or modify it
   8   under the terms of the GNU Lesser General Public License as published by
   9   the Free Software Foundation; either version 2.1 of the License, or
  10   (at your option) any later version.
  11
  12   systemd is distributed in the hope that it will be useful, but
  13   WITHOUT ANY WARRANTY; without even the implied warranty of
  14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  15   Lesser General Public License for more details.
  16
  17   You should have received a copy of the GNU Lesser General Public License
  18   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  19 ***/
  20
  21 #include <errno.h>
  22 #include <fcntl.h>
  23 #include <stdbool.h>
  24 #include <stdlib.h>
  25 #include <sys/stat.h>
  26 #include <syslog.h>
  27 #include <unistd.h>
  28
  29 #include "alloc-util.h"
  30 #include "base-filesystem.h"
  31 #include "fd-util.h"
  32 #include "log.h"
  33 #include "macro.h"
  34 #include "string-util.h"
  35 #include "umask-util.h"
  36 #include "user-util.h"
  37 #include "util.h"
  38
  39 typedef struct BaseFilesystem {
  40         const char *dir;
  41         mode_t mode;
  42         const char *target;
  43         const char *exists;
  44         bool ignore_failure;
  45 } BaseFilesystem;
  46
  47 static const BaseFilesystem table[] = {
  48         { "bin",      0, "usr/bin\0",                  NULL },
  49         { "lib",      0, "usr/lib\0",                  NULL },
  50         { "root",  0755, NULL,                         NULL, true },
  51         { "sbin",     0, "usr/sbin\0",                 NULL },
  52         { "usr",   0755, NULL,                         NULL },
  53         { "var",   0755, NULL,                         NULL },
  54         { "etc",   0755, NULL,                         NULL },
  55         { "proc",  0755, NULL,                         NULL, true },
  56         { "sys",   0755, NULL,                         NULL, true },
  57         { "dev",   0755, NULL,                         NULL, true },
  58 #if defined(__i386__) || defined(__x86_64__)
  59         { "lib64",    0, "usr/lib/x86_64-linux-gnu\0"
  60                          "usr/lib64\0",                "ld-linux-x86-64.so.2" },
  61 #endif
  62 };
  63
  64 int base_filesystem_create(const char *root, uid_t uid, gid_t gid) {
  65         _cleanup_close_ int fd = -1;
  66         unsigned i;
  67         int r = 0;
  68
  69         fd = open(root, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW);
  70         if (fd < 0)
  71                 return log_error_errno(errno, "Failed to open root file system: %m");
  72
  73         for (i = 0; i < ELEMENTSOF(table); i ++) {
  74                 if (faccessat(fd, table[i].dir, F_OK, AT_SYMLINK_NOFOLLOW) >= 0)
  75                         continue;
  76
  77                 if (table[i].target) {
  78                         const char *target = NULL, *s;
  79
  80                         /* check if one of the targets exists */
  81                         NULSTR_FOREACH(s, table[i].target) {
  82                                 if (faccessat(fd, s, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
  83                                         continue;
  84
  85                                 /* check if a specific file exists at the target path */
  86                                 if (table[i].exists) {
  87                                         _cleanup_free_ char *p = NULL;
  88
  89                                         p = strjoin(s, "/", table[i].exists);
  90                                         if (!p)
  91                                                 return log_oom();
  92
  93                                         if (faccessat(fd, p, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
  94                                                 continue;
  95                                 }
  96
  97                                 target = s;
  98                                 break;
  99                         }
 100
 101                         if (!target)
 102                                 continue;
 103
 104                         r = symlinkat(target, fd, table[i].dir);
 105                         if (r < 0 && errno != EEXIST)
 106                                 return log_error_errno(errno, "Failed to create symlink at %s/%s: %m", root, table[i].dir);
 107
 108                         if (uid_is_valid(uid) || gid_is_valid(gid)) {
 109                                 if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)
 110                                         return log_error_errno(errno, "Failed to chown symlink at %s/%s: %m", root, table[i].dir);
 111                         }
 112
 113                         continue;
 114                 }
 115
 116                 RUN_WITH_UMASK(0000)
 117                         r = mkdirat(fd, table[i].dir, table[i].mode);
 118                 if (r < 0 && errno != EEXIST) {
 119                         log_full_errno(table[i].ignore_failure ? LOG_DEBUG : LOG_ERR, errno,
 120                                        "Failed to create directory at %s/%s: %m", root, table[i].dir);
 121
 122                         if (!table[i].ignore_failure)
 123                                 return -errno;
 124
 125                         continue;
 126                 }
 127
 128                 if (uid != UID_INVALID || gid != UID_INVALID) {
 129                         if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)
 130                                 return log_error_errno(errno, "Failed to chown directory at %s/%s: %m", root, table[i].dir);
 131                 }
 132         }
 133
 134         return 0;
 135 }