src/shared/base-filesystem.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright 2014 Kay Sievers
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include <errno.h>
  21 #include <fcntl.h>
  22 #include <stdbool.h>
  23 #include <stdlib.h>
  24 #include <sys/stat.h>
  25 #include <syslog.h>
  26 #include <unistd.h>
  27
  28 #include "alloc-util.h"
  29 #include "base-filesystem.h"
  30 #include "fd-util.h"
  31 #include "log.h"
  32 #include "macro.h"
  33 #include "string-util.h"
  34 #include "umask-util.h"
  35 #include "user-util.h"
  36 #include "util.h"
  37
  38 typedef struct BaseFilesystem {
  39         const char *dir;
  40         mode_t mode;
  41         const char *target;
  42         const char *exists;
  43         bool ignore_failure;
  44 } BaseFilesystem;
  45
  46 static const BaseFilesystem table[] = {
  47         { "bin",      0, "usr/bin\0",                  NULL },
  48         { "lib",      0, "usr/lib\0",                  NULL },
  49         { "root",  0755, NULL,                         NULL, true },
  50         { "sbin",     0, "usr/sbin\0",                 NULL },
  51         { "usr",   0755, NULL,                         NULL },
  52         { "var",   0755, NULL,                         NULL },
  53         { "etc",   0755, NULL,                         NULL },
  54         { "proc",  0755, NULL,                         NULL, true },
  55         { "sys",   0755, NULL,                         NULL, true },
  56         { "dev",   0755, NULL,                         NULL, true },
  57 #if defined(__i386__) || defined(__x86_64__)
  58         { "lib64",    0, "usr/lib/x86_64-linux-gnu\0"
  59                          "usr/lib64\0",                "ld-linux-x86-64.so.2" },
  60 #endif
  61 };
  62
  63 int base_filesystem_create(const char *root, uid_t uid, gid_t gid) {
  64         _cleanup_close_ int fd = -1;
  65         unsigned i;
  66         int r = 0;
  67
  68         fd = open(root, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW);
  69         if (fd < 0)
  70                 return log_error_errno(errno, "Failed to open root file system: %m");
  71
  72         for (i = 0; i < ELEMENTSOF(table); i ++) {
  73                 if (faccessat(fd, table[i].dir, F_OK, AT_SYMLINK_NOFOLLOW) >= 0)
  74                         continue;
  75
  76                 if (table[i].target) {
  77                         const char *target = NULL, *s;
  78
  79                         /* check if one of the targets exists */
  80                         NULSTR_FOREACH(s, table[i].target) {
  81                                 if (faccessat(fd, s, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
  82                                         continue;
  83
  84                                 /* check if a specific file exists at the target path */
  85                                 if (table[i].exists) {
  86                                         _cleanup_free_ char *p = NULL;
  87
  88                                         p = strjoin(s, "/", table[i].exists);
  89                                         if (!p)
  90                                                 return log_oom();
  91
  92                                         if (faccessat(fd, p, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
  93                                                 continue;
  94                                 }
  95
  96                                 target = s;
  97                                 break;
  98                         }
  99
 100                         if (!target)
 101                                 continue;
 102
 103                         r = symlinkat(target, fd, table[i].dir);
 104                         if (r < 0 && errno != EEXIST)
 105                                 return log_error_errno(errno, "Failed to create symlink at %s/%s: %m", root, table[i].dir);
 106
 107                         if (uid_is_valid(uid) || gid_is_valid(gid)) {
 108                                 if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)
 109                                         return log_error_errno(errno, "Failed to chown symlink at %s/%s: %m", root, table[i].dir);
 110                         }
 111
 112                         continue;
 113                 }
 114
 115                 RUN_WITH_UMASK(0000)
 116                         r = mkdirat(fd, table[i].dir, table[i].mode);
 117                 if (r < 0 && errno != EEXIST) {
 118                         log_full_errno(table[i].ignore_failure ? LOG_DEBUG : LOG_ERR, errno,
 119                                        "Failed to create directory at %s/%s: %m", root, table[i].dir);
 120
 121                         if (!table[i].ignore_failure)
 122                                 return -errno;
 123
 124                         continue;
 125                 }
 126
 127                 if (uid != UID_INVALID || gid != UID_INVALID) {
 128                         if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)
 129                                 return log_error_errno(errno, "Failed to chown directory at %s/%s: %m", root, table[i].dir);
 130                 }
 131         }
 132
 133         return 0;
 134 }