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