src/home/homework-directory.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include <sys/mount.h>
   4
   5 #include "btrfs-util.h"
   6 #include "fd-util.h"
   7 #include "homework-directory.h"
   8 #include "homework-mount.h"
   9 #include "homework-quota.h"
  10 #include "mkdir.h"
  11 #include "mount-util.h"
  12 #include "path-util.h"
  13 #include "rm-rf.h"
  14 #include "tmpfile-util.h"
  15 #include "umask-util.h"
  16 #include "user-util.h"
  17
  18 int home_setup_directory(UserRecord *h, HomeSetup *setup) {
  19         const char *ip;
  20         int r;
  21
  22         assert(h);
  23         assert(IN_SET(user_record_storage(h), USER_DIRECTORY, USER_SUBVOLUME));
  24         assert(setup);
  25         assert(!setup->undo_mount);
  26         assert(setup->root_fd < 0);
  27
  28         /* We'll bind mount the image directory to a new mount point where we'll start adjusting it. Only
  29          * once that's complete we'll move the thing to its final place eventually. */
  30         r = home_unshare_and_mkdir();
  31         if (r < 0)
  32                 return r;
  33
  34         assert_se(ip = user_record_image_path(h));
  35
  36         r = mount_follow_verbose(LOG_ERR, ip, HOME_RUNTIME_WORK_DIR, NULL, MS_BIND, NULL);
  37         if (r < 0)
  38                 return r;
  39
  40         setup->undo_mount = true;
  41
  42         /* Turn off any form of propagation for this */
  43         r = mount_nofollow_verbose(LOG_ERR, NULL, HOME_RUNTIME_WORK_DIR, NULL, MS_PRIVATE, NULL);
  44         if (r < 0)
  45                 return r;
  46
  47         /* Adjust MS_SUID and similar flags */
  48         r = mount_nofollow_verbose(LOG_ERR, NULL, HOME_RUNTIME_WORK_DIR, NULL, MS_BIND|MS_REMOUNT|user_record_mount_flags(h), NULL);
  49         if (r < 0)
  50                 return r;
  51
  52         setup->root_fd = open(HOME_RUNTIME_WORK_DIR, O_RDONLY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW);
  53         if (setup->root_fd < 0)
  54                 return log_error_errno(errno, "Failed to open home directory: %m");
  55
  56         return 0;
  57 }
  58
  59 int home_activate_directory(
  60                 UserRecord *h,
  61                 HomeSetup *setup,
  62                 PasswordCache *cache,
  63                 UserRecord **ret_home) {
  64
  65         _cleanup_(user_record_unrefp) UserRecord *new_home = NULL, *header_home = NULL;
  66         const char *hd, *hdo;
  67         int r;
  68
  69         assert(h);
  70         assert(IN_SET(user_record_storage(h), USER_DIRECTORY, USER_SUBVOLUME, USER_FSCRYPT));
  71         assert(setup);
  72         assert(ret_home);
  73
  74         assert_se(hdo = user_record_home_directory(h));
  75         hd = strdupa_safe(hdo);
  76
  77         r = home_setup(h, 0, cache, setup, &header_home);
  78         if (r < 0)
  79                 return r;
  80
  81         r = home_refresh(h, setup, header_home, cache, NULL, &new_home);
  82         if (r < 0)
  83                 return r;
  84
  85         r = home_extend_embedded_identity(new_home, h, setup);
  86         if (r < 0)
  87                 return r;
  88
  89         /* Close fd to private mount before moving mount */
  90         setup->root_fd = safe_close(setup->root_fd);
  91
  92         /* We are now done with everything, move the mount into place */
  93         r = home_move_mount(NULL, hd);
  94         if (r < 0)
  95                 return r;
  96
  97         setup->undo_mount = false;
  98
  99         setup->do_drop_caches = false;
 100
 101         log_info("Everything completed.");
 102
 103         *ret_home = TAKE_PTR(new_home);
 104         return 0;
 105 }
 106
 107 int home_create_directory_or_subvolume(UserRecord *h, HomeSetup *setup, UserRecord **ret_home) {
 108         _cleanup_(rm_rf_subvolume_and_freep) char *temporary = NULL;
 109         _cleanup_(user_record_unrefp) UserRecord *new_home = NULL;
 110         _cleanup_close_ int mount_fd = -1;
 111         _cleanup_free_ char *d = NULL;
 112         bool is_subvolume = false;
 113         const char *ip;
 114         int r;
 115
 116         assert(h);
 117         assert(IN_SET(user_record_storage(h), USER_DIRECTORY, USER_SUBVOLUME));
 118         assert(setup);
 119         assert(ret_home);
 120
 121         assert_se(ip = user_record_image_path(h));
 122
 123         r = tempfn_random(ip, "homework", &d);
 124         if (r < 0)
 125                 return log_error_errno(r, "Failed to allocate temporary directory: %m");
 126
 127         (void) mkdir_parents(d, 0755);
 128
 129         switch (user_record_storage(h)) {
 130
 131         case USER_SUBVOLUME:
 132                 RUN_WITH_UMASK(0077)
 133                         r = btrfs_subvol_make(d);
 134
 135                 if (r >= 0) {
 136                         log_info("Subvolume created.");
 137                         is_subvolume = true;
 138
 139                         if (h->disk_size != UINT64_MAX) {
 140
 141                                 /* Enable quota for the subvolume we just created. Note we don't check for
 142                                  * errors here and only log about debug level about this. */
 143                                 r = btrfs_quota_enable(d, true);
 144                                 if (r < 0)
 145                                         log_debug_errno(r, "Failed to enable quota on %s, ignoring: %m", d);
 146
 147                                 r = btrfs_subvol_auto_qgroup(d, 0, false);
 148                                 if (r < 0)
 149                                         log_debug_errno(r, "Failed to set up automatic quota group on %s, ignoring: %m", d);
 150
 151                                 /* Actually configure the quota. We also ignore errors here, but we do log
 152                                  * about them loudly, to keep things discoverable even though we don't
 153                                  * consider lacking quota support in kernel fatal. */
 154                                 (void) home_update_quota_btrfs(h, d);
 155                         }
 156
 157                         break;
 158                 }
 159                 if (r != -ENOTTY)
 160                         return log_error_errno(r, "Failed to create temporary home directory subvolume %s: %m", d);
 161
 162                 log_info("Creating subvolume %s is not supported, as file system does not support subvolumes. Falling back to regular directory.", d);
 163                 _fallthrough_;
 164
 165         case USER_DIRECTORY:
 166
 167                 if (mkdir(d, 0700) < 0)
 168                         return log_error_errno(errno, "Failed to create temporary home directory %s: %m", d);
 169
 170                 (void) home_update_quota_classic(h, d);
 171                 break;
 172
 173         default:
 174                 assert_not_reached();
 175         }
 176
 177         temporary = TAKE_PTR(d); /* Needs to be destroyed now */
 178
 179         /* Let's decouple namespaces now, so that we can possibly mount a UID map mount into
 180          * /run/systemd/user-home-mount/ that noone will see but us. */
 181         r = home_unshare_and_mkdir();
 182         if (r < 0)
 183                 return r;
 184
 185         setup->root_fd = open(temporary, O_RDONLY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW);
 186         if (setup->root_fd < 0)
 187                 return log_error_errno(errno, "Failed to open temporary home directory: %m");
 188
 189         /* Try to apply a UID shift, so that the directory is actually owned by "nobody", and is only mapped
 190          * to the proper UID while active. — Well, that's at least the theory. Unfortunately, only btrfs does
 191          * per-subvolume quota. The others do per-uid quota. Which means mapping all home directories to the
 192          * same UID of "nobody" makes quota impossible. Hence unless we actually managed to create a btrfs
 193          * subvolume for this user we'll map the user's UID to itself. Now you might ask: why bother mapping
 194          * at all? It's because we want to restrict the UIDs used on the home directory: we leave all other
 195          * UIDs of the homed UID range unmapped, thus making them unavailable to programs accessing the
 196          * mount. */
 197         r = home_shift_uid(setup->root_fd, HOME_RUNTIME_WORK_DIR, is_subvolume ? UID_NOBODY : h->uid, h->uid, &mount_fd);
 198         if (r > 0)
 199                 setup->undo_mount = true; /* If uidmaps worked we have a mount to undo again */
 200
 201         if (mount_fd >= 0) {
 202                 /* If we have established a new mount, then we can use that as new root fd to our home directory. */
 203                 safe_close(setup->root_fd);
 204
 205                 setup->root_fd = fd_reopen(mount_fd, O_RDONLY|O_CLOEXEC|O_DIRECTORY);
 206                 if (setup->root_fd < 0)
 207                         return log_error_errno(setup->root_fd, "Unable to convert mount fd into proper directory fd: %m");
 208
 209                 mount_fd = safe_close(mount_fd);
 210         }
 211
 212         r = home_populate(h, setup->root_fd);
 213         if (r < 0)
 214                 return r;
 215
 216         r = home_sync_and_statfs(setup->root_fd, NULL);
 217         if (r < 0)
 218                 return r;
 219
 220         r = user_record_clone(h, USER_RECORD_LOAD_MASK_SECRET|USER_RECORD_PERMISSIVE, &new_home);
 221         if (r < 0)
 222                 return log_error_errno(r, "Failed to clone record: %m");
 223
 224         r = user_record_add_binding(
 225                         new_home,
 226                         user_record_storage(h),
 227                         ip,
 228                         SD_ID128_NULL,
 229                         SD_ID128_NULL,
 230                         SD_ID128_NULL,
 231                         NULL,
 232                         NULL,
 233                         UINT64_MAX,
 234                         NULL,
 235                         NULL,
 236                         h->uid,
 237                         (gid_t) h->uid);
 238         if (r < 0)
 239                 return log_error_errno(r, "Failed to add binding to record: %m");
 240
 241         setup->root_fd = safe_close(setup->root_fd);
 242
 243         /* Unmount mapped mount before we move the dir into place */
 244         if (setup->undo_mount) {
 245                 r = umount_verbose(LOG_ERR, HOME_RUNTIME_WORK_DIR, UMOUNT_NOFOLLOW);
 246                 if (r < 0)
 247                         return r;
 248
 249                 setup->undo_mount = false;
 250         }
 251
 252         if (rename(temporary, ip) < 0)
 253                 return log_error_errno(errno, "Failed to rename %s to %s: %m", temporary, ip);
 254
 255         temporary = mfree(temporary);
 256
 257         log_info("Everything completed.");
 258
 259         *ret_home = TAKE_PTR(new_home);
 260         return 0;
 261 }
 262
 263 int home_resize_directory(
 264                 UserRecord *h,
 265                 HomeSetupFlags flags,
 266                 PasswordCache *cache,
 267                 HomeSetup *setup,
 268                 UserRecord **ret_home) {
 269
 270         _cleanup_(user_record_unrefp) UserRecord *embedded_home = NULL, *new_home = NULL;
 271         int r;
 272
 273         assert(h);
 274         assert(setup);
 275         assert(ret_home);
 276         assert(IN_SET(user_record_storage(h), USER_DIRECTORY, USER_SUBVOLUME, USER_FSCRYPT));
 277
 278         r = home_setup(h, flags, cache, setup, NULL);
 279         if (r < 0)
 280                 return r;
 281
 282         r = home_load_embedded_identity(h, setup->root_fd, NULL, USER_RECONCILE_REQUIRE_NEWER_OR_EQUAL, cache, &embedded_home, &new_home);
 283         if (r < 0)
 284                 return r;
 285
 286         r = home_maybe_shift_uid(h, setup);
 287         if (r < 0)
 288                 return r;
 289
 290         r = home_update_quota_auto(h, NULL);
 291         if (ERRNO_IS_NOT_SUPPORTED(r))
 292                 return -ESOCKTNOSUPPORT; /* make recognizable */
 293         if (r < 0)
 294                 return r;
 295
 296         r = home_store_embedded_identity(new_home, setup->root_fd, h->uid, embedded_home);
 297         if (r < 0)
 298                 return r;
 299
 300         r = home_extend_embedded_identity(new_home, h, setup);
 301         if (r < 0)
 302                 return r;
 303
 304         r = home_sync_and_statfs(setup->root_fd, NULL);
 305         if (r < 0)
 306                 return r;
 307
 308         r = home_setup_done(setup);
 309         if (r < 0)
 310                 return r;
 311
 312         log_info("Everything completed.");
 313
 314         *ret_home = TAKE_PTR(new_home);
 315         return 0;
 316 }