gio/gkeyfilesettingsbackend.c

   1 /*
   2  * Copyright © 2010 Codethink Limited
   3  * Copyright © 2010 Novell, Inc.
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2 of the licence, or (at your option) any later version.
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  17  *
  18  * Authors: Vincent Untz <vuntz@gnome.org>
  19  *          Ryan Lortie <desrt@desrt.ca>
  20  */
  21
  22 #include "config.h"
  23
  24 #include <stdio.h>
  25 #include <string.h>
  26
  27 #include "gfile.h"
  28 #include "gfileinfo.h"
  29 #include "gfilemonitor.h"
  30 #include "gsimplepermission.h"
  31 #include "gsettingsbackend.h"
  32
  33
  34 #define G_TYPE_KEYFILE_SETTINGS_BACKEND      (g_keyfile_settings_backend_get_type ())
  35 #define G_KEYFILE_SETTINGS_BACKEND(inst)     (G_TYPE_CHECK_INSTANCE_CAST ((inst),      \
  36                                               G_TYPE_KEYFILE_SETTINGS_BACKEND,         \
  37                                               GKeyfileSettingsBackend))
  38 #define G_IS_KEYFILE_SETTINGS_BACKEND(inst)  (G_TYPE_CHECK_INSTANCE_TYPE ((inst),      \
  39                                               G_TYPE_KEYFILE_SETTINGS_BACKEND))
  40
  41
  42 typedef GSettingsBackendClass GKeyfileSettingsBackendClass;
  43
  44 typedef struct
  45 {
  46   GSettingsBackend   parent_instance;
  47
  48   GKeyFile          *keyfile;
  49   GPermission       *permission;
  50   gboolean           writable;
  51
  52   gchar             *prefix;
  53   gint               prefix_len;
  54   gchar             *root_group;
  55   gint               root_group_len;
  56
  57   GFile             *file;
  58   GFileMonitor      *file_monitor;
  59   guint8             digest[32];
  60   GFile             *dir;
  61   GFileMonitor      *dir_monitor;
  62 } GKeyfileSettingsBackend;
  63
  64 static GType g_keyfile_settings_backend_get_type (void);
  65 G_DEFINE_TYPE (GKeyfileSettingsBackend,
  66                g_keyfile_settings_backend,
  67                G_TYPE_SETTINGS_BACKEND)
  68
  69 static void
  70 compute_checksum (guint8        *digest,
  71                   gconstpointer  contents,
  72                   gsize          length)
  73 {
  74   GChecksum *checksum;
  75   gsize len = 32;
  76
  77   checksum = g_checksum_new (G_CHECKSUM_SHA256);
  78   g_checksum_update (checksum, contents, length);
  79   g_checksum_get_digest (checksum, digest, &len);
  80   g_checksum_free (checksum);
  81   g_assert (len == 32);
  82 }
  83
  84 static void
  85 g_keyfile_settings_backend_keyfile_write (GKeyfileSettingsBackend *kfsb)
  86 {
  87   gchar *contents;
  88   gsize length;
  89
  90   contents = g_key_file_to_data (kfsb->keyfile, &length, NULL);
  91   g_file_replace_contents (kfsb->file, contents, length, NULL, FALSE,
  92                            G_FILE_CREATE_REPLACE_DESTINATION,
  93                            NULL, NULL, NULL);
  94
  95   compute_checksum (kfsb->digest, contents, length);
  96   g_free (contents);
  97 }
  98
  99 static gboolean
 100 group_name_matches (const gchar *group_name,
 101                     const gchar *prefix)
 102 {
 103   /* sort of like g_str_has_prefix() except that it must be an exact
 104    * match or the prefix followed by '/'.
 105    *
 106    * for example 'a' is a prefix of 'a' and 'a/b' but not 'ab'.
 107    */
 108   gint i;
 109
 110   for (i = 0; prefix[i]; i++)
 111     if (prefix[i] != group_name[i])
 112       return FALSE;
 113
 114   return group_name[i] == '\0' || group_name[i] == '/';
 115 }
 116
 117 static gboolean
 118 convert_path (GKeyfileSettingsBackend  *kfsb,
 119               const gchar              *key,
 120               gchar                   **group,
 121               gchar                   **basename)
 122 {
 123   gint key_len = strlen (key);
 124   gint i;
 125
 126   if (key_len < kfsb->prefix_len ||
 127       memcmp (key, kfsb->prefix, kfsb->prefix_len) != 0)
 128     return FALSE;
 129
 130   key_len -= kfsb->prefix_len;
 131   key += kfsb->prefix_len;
 132
 133   for (i = key_len; i >= 0; i--)
 134     if (key[i] == '/')
 135       break;
 136
 137   if (kfsb->root_group)
 138     {
 139       /* if a root_group was specified, make sure the user hasn't given
 140        * a path that ghosts that group name
 141        */
 142       if (i == kfsb->root_group_len && memcmp (key, kfsb->root_group, i) == 0)
 143         return FALSE;
 144     }
 145   else
 146     {
 147       /* if no root_group was given, ensure that the user gave a path */
 148       if (i == -1)
 149         return FALSE;
 150     }
 151
 152   if (group)
 153     {
 154       if (i >= 0)
 155         {
 156           *group = g_memdup (key, i + 1);
 157           (*group)[i] = '\0';
 158         }
 159       else
 160         *group = g_strdup (kfsb->root_group);
 161     }
 162
 163   if (basename)
 164     *basename = g_memdup (key + i + 1, key_len - i);
 165
 166   return TRUE;
 167 }
 168
 169 static gboolean
 170 path_is_valid (GKeyfileSettingsBackend *kfsb,
 171                const gchar             *path)
 172 {
 173   return convert_path (kfsb, path, NULL, NULL);
 174 }
 175
 176 static GVariant *
 177 get_from_keyfile (GKeyfileSettingsBackend *kfsb,
 178                   const GVariantType      *type,
 179                   const gchar             *key)
 180 {
 181   GVariant *return_value = NULL;
 182   gchar *group, *name;
 183
 184   if (convert_path (kfsb, key, &group, &name))
 185     {
 186       gchar *str;
 187
 188       g_assert (*name);
 189
 190       str = g_key_file_get_value (kfsb->keyfile, group, name, NULL);
 191
 192       if (str)
 193         {
 194           return_value = g_variant_parse (type, str, NULL, NULL, NULL);
 195           g_free (str);
 196         }
 197
 198       g_free (group);
 199       g_free (name);
 200     }
 201
 202   return return_value;
 203 }
 204
 205 static gboolean
 206 set_to_keyfile (GKeyfileSettingsBackend *kfsb,
 207                 const gchar             *key,
 208                 GVariant                *value)
 209 {
 210   gchar *group, *name;
 211
 212   if (convert_path (kfsb, key, &group, &name))
 213     {
 214       if (value)
 215         {
 216           gchar *str = g_variant_print (value, FALSE);
 217           g_key_file_set_value (kfsb->keyfile, group, name, str);
 218           g_variant_unref (g_variant_ref_sink (value));
 219           g_free (str);
 220         }
 221       else
 222         {
 223           if (*name == '\0')
 224             {
 225               gchar **groups;
 226               gint i;
 227
 228               groups = g_key_file_get_groups (kfsb->keyfile, NULL);
 229
 230               for (i = 0; groups[i]; i++)
 231                 if (group_name_matches (groups[i], group))
 232                   g_key_file_remove_group (kfsb->keyfile, groups[i], NULL);
 233
 234               g_strfreev (groups);
 235             }
 236           else
 237             g_key_file_remove_key (kfsb->keyfile, group, name, NULL);
 238         }
 239
 240       g_free (group);
 241       g_free (name);
 242
 243       return TRUE;
 244     }
 245
 246   return FALSE;
 247 }
 248
 249 static GVariant *
 250 g_keyfile_settings_backend_read (GSettingsBackend   *backend,
 251                                  const gchar        *key,
 252                                  const GVariantType *expected_type,
 253                                  gboolean            default_value)
 254 {
 255   GKeyfileSettingsBackend *kfsb = G_KEYFILE_SETTINGS_BACKEND (backend);
 256
 257   if (default_value)
 258     return NULL;
 259
 260   return get_from_keyfile (kfsb, expected_type, key);
 261 }
 262
 263 typedef struct
 264 {
 265   GKeyfileSettingsBackend *kfsb;
 266   gboolean failed;
 267 } WriteManyData;
 268
 269 static gboolean
 270 g_keyfile_settings_backend_write_one (gpointer key,
 271                                       gpointer value,
 272                                       gpointer user_data)
 273 {
 274   WriteManyData *data = user_data;
 275   gboolean success;
 276
 277   success = set_to_keyfile (data->kfsb, key, value);
 278   g_assert (success);
 279
 280   return FALSE;
 281 }
 282
 283 static gboolean
 284 g_keyfile_settings_backend_check_one (gpointer key,
 285                                       gpointer value,
 286                                       gpointer user_data)
 287 {
 288   WriteManyData *data = user_data;
 289
 290   return data->failed = !path_is_valid (data->kfsb, key);
 291 }
 292
 293 static gboolean
 294 g_keyfile_settings_backend_write_tree (GSettingsBackend *backend,
 295                                        GTree            *tree,
 296                                        gpointer          origin_tag)
 297 {
 298   WriteManyData data = { G_KEYFILE_SETTINGS_BACKEND (backend) };
 299
 300   if (!data.kfsb->writable)
 301     return FALSE;
 302
 303   g_tree_foreach (tree, g_keyfile_settings_backend_check_one, &data);
 304
 305   if (data.failed)
 306     return FALSE;
 307
 308   g_tree_foreach (tree, g_keyfile_settings_backend_write_one, &data);
 309   g_keyfile_settings_backend_keyfile_write (data.kfsb);
 310
 311   g_settings_backend_changed_tree (backend, tree, origin_tag);
 312
 313   return TRUE;
 314 }
 315
 316 static gboolean
 317 g_keyfile_settings_backend_write (GSettingsBackend *backend,
 318                                   const gchar      *key,
 319                                   GVariant         *value,
 320                                   gpointer          origin_tag)
 321 {
 322   GKeyfileSettingsBackend *kfsb = G_KEYFILE_SETTINGS_BACKEND (backend);
 323   gboolean success;
 324
 325   if (!kfsb->writable)
 326     return FALSE;
 327
 328   success = set_to_keyfile (kfsb, key, value);
 329
 330   if (success)
 331     {
 332       g_settings_backend_changed (backend, key, origin_tag);
 333       g_keyfile_settings_backend_keyfile_write (kfsb);
 334     }
 335
 336   return success;
 337 }
 338
 339 static void
 340 g_keyfile_settings_backend_reset (GSettingsBackend *backend,
 341                                   const gchar      *key,
 342                                   gpointer          origin_tag)
 343 {
 344   GKeyfileSettingsBackend *kfsb = G_KEYFILE_SETTINGS_BACKEND (backend);
 345
 346   if (set_to_keyfile (kfsb, key, NULL))
 347     g_keyfile_settings_backend_keyfile_write (kfsb);
 348
 349   g_settings_backend_changed (backend, key, origin_tag);
 350 }
 351
 352 static gboolean
 353 g_keyfile_settings_backend_get_writable (GSettingsBackend *backend,
 354                                          const gchar      *name)
 355 {
 356   GKeyfileSettingsBackend *kfsb = G_KEYFILE_SETTINGS_BACKEND (backend);
 357
 358   return kfsb->writable && path_is_valid (kfsb, name);
 359 }
 360
 361 static GPermission *
 362 g_keyfile_settings_backend_get_permission (GSettingsBackend *backend,
 363                                            const gchar      *path)
 364 {
 365   GKeyfileSettingsBackend *kfsb = G_KEYFILE_SETTINGS_BACKEND (backend);
 366
 367   return g_object_ref (kfsb->permission);
 368 }
 369
 370 static void
 371 keyfile_to_tree (GKeyfileSettingsBackend *kfsb,
 372                  GTree                   *tree,
 373                  GKeyFile                *keyfile,
 374                  gboolean                 dup_check)
 375 {
 376   gchar **groups;
 377   gint i;
 378
 379   groups = g_key_file_get_groups (keyfile, NULL);
 380   for (i = 0; groups[i]; i++)
 381     {
 382       gboolean is_root_group;
 383       gchar **keys;
 384       gint j;
 385
 386       is_root_group = g_strcmp0 (kfsb->root_group, groups[i]) == 0;
 387
 388       /* reject group names that will form invalid key names */
 389       if (!is_root_group &&
 390           (g_str_has_prefix (groups[i], "/") ||
 391            g_str_has_suffix (groups[i], "/") || strstr (groups[i], "//")))
 392         continue;
 393
 394       keys = g_key_file_get_keys (keyfile, groups[i], NULL, NULL);
 395       g_assert (keys != NULL);
 396
 397       for (j = 0; keys[j]; j++)
 398         {
 399           gchar *path, *value;
 400
 401           /* reject key names with slashes in them */
 402           if (strchr (keys[j], '/'))
 403             continue;
 404
 405           if (is_root_group)
 406             path = g_strdup_printf ("%s%s", kfsb->prefix, keys[j]);
 407           else
 408             path = g_strdup_printf ("%s%s/%s", kfsb->prefix, groups[i], keys[j]);
 409
 410           value = g_key_file_get_value (keyfile, groups[i], keys[j], NULL);
 411
 412           if (dup_check && g_strcmp0 (g_tree_lookup (tree, path), value) == 0)
 413             {
 414               g_tree_remove (tree, path);
 415               g_free (value);
 416               g_free (path);
 417             }
 418           else
 419             g_tree_insert (tree, path, value);
 420         }
 421
 422       g_strfreev (keys);
 423     }
 424   g_strfreev (groups);
 425 }
 426
 427 static void
 428 g_keyfile_settings_backend_keyfile_reload (GKeyfileSettingsBackend *kfsb)
 429 {
 430   guint8 digest[32];
 431   gchar *contents;
 432   gsize length;
 433
 434   contents = NULL;
 435   length = 0;
 436
 437   g_file_load_contents (kfsb->file, NULL, &contents, &length, NULL, NULL);
 438   compute_checksum (digest, contents, length);
 439
 440   if (memcmp (kfsb->digest, digest, sizeof digest) != 0)
 441     {
 442       GKeyFile *keyfiles[2];
 443       GTree *tree;
 444
 445       tree = g_tree_new_full ((GCompareDataFunc) strcmp, NULL,
 446                               g_free, g_free);
 447
 448       keyfiles[0] = kfsb->keyfile;
 449       keyfiles[1] = g_key_file_new ();
 450
 451       if (length > 0)
 452         g_key_file_load_from_data (keyfiles[1], contents, length,
 453                                    G_KEY_FILE_KEEP_COMMENTS |
 454                                    G_KEY_FILE_KEEP_TRANSLATIONS, NULL);
 455
 456       keyfile_to_tree (kfsb, tree, keyfiles[0], FALSE);
 457       keyfile_to_tree (kfsb, tree, keyfiles[1], TRUE);
 458       g_key_file_free (keyfiles[0]);
 459       kfsb->keyfile = keyfiles[1];
 460
 461       if (g_tree_nnodes (tree) > 0)
 462         g_settings_backend_changed_tree (&kfsb->parent_instance, tree, NULL);
 463
 464       g_tree_unref (tree);
 465
 466       memcpy (kfsb->digest, digest, sizeof digest);
 467     }
 468
 469   g_free (contents);
 470 }
 471
 472 static void
 473 g_keyfile_settings_backend_keyfile_writable (GKeyfileSettingsBackend *kfsb)
 474 {
 475   GFileInfo *fileinfo;
 476   gboolean writable;
 477
 478   fileinfo = g_file_query_info (kfsb->dir, "access::*", 0, NULL, NULL);
 479
 480   if (fileinfo)
 481     {
 482       writable =
 483         g_file_info_get_attribute_boolean (fileinfo, G_FILE_ATTRIBUTE_ACCESS_CAN_WRITE) &&
 484         g_file_info_get_attribute_boolean (fileinfo, G_FILE_ATTRIBUTE_ACCESS_CAN_EXECUTE);
 485       g_object_unref (fileinfo);
 486     }
 487   else
 488     writable = FALSE;
 489
 490   if (writable != kfsb->writable)
 491     {
 492       kfsb->writable = writable;
 493       g_settings_backend_path_writable_changed (&kfsb->parent_instance, "/");
 494     }
 495 }
 496
 497 static void
 498 g_keyfile_settings_backend_finalize (GObject *object)
 499 {
 500   GKeyfileSettingsBackend *kfsb = G_KEYFILE_SETTINGS_BACKEND (object);
 501
 502   g_key_file_free (kfsb->keyfile);
 503   g_object_unref (kfsb->permission);
 504
 505   g_file_monitor_cancel (kfsb->file_monitor);
 506   g_object_unref (kfsb->file_monitor);
 507   g_object_unref (kfsb->file);
 508
 509   g_file_monitor_cancel (kfsb->dir_monitor);
 510   g_object_unref (kfsb->dir_monitor);
 511   g_object_unref (kfsb->dir);
 512
 513   g_free (kfsb->root_group);
 514   g_free (kfsb->prefix);
 515
 516   G_OBJECT_CLASS (g_keyfile_settings_backend_parent_class)
 517     ->finalize (object);
 518 }
 519
 520 static void
 521 g_keyfile_settings_backend_init (GKeyfileSettingsBackend *kfsb)
 522 {
 523 }
 524
 525 static void
 526 g_keyfile_settings_backend_class_init (GKeyfileSettingsBackendClass *class)
 527 {
 528   GObjectClass *object_class = G_OBJECT_CLASS (class);
 529
 530   object_class->finalize = g_keyfile_settings_backend_finalize;
 531
 532   class->read = g_keyfile_settings_backend_read;
 533   class->write = g_keyfile_settings_backend_write;
 534   class->write_tree = g_keyfile_settings_backend_write_tree;
 535   class->reset = g_keyfile_settings_backend_reset;
 536   class->get_writable = g_keyfile_settings_backend_get_writable;
 537   class->get_permission = g_keyfile_settings_backend_get_permission;
 538   /* No need to implement subscribed/unsubscribe: the only point would be to
 539    * stop monitoring the file when there's no GSettings anymore, which is no
 540    * big win.
 541    */
 542 }
 543
 544 static void
 545 file_changed (GFileMonitor      *monitor,
 546               GFile             *file,
 547               GFile             *other_file,
 548               GFileMonitorEvent  event_type,
 549               gpointer           user_data)
 550 {
 551   GKeyfileSettingsBackend *kfsb = user_data;
 552
 553   /* Ignore file deletions, let the GKeyFile content remain in tact. */
 554   if (event_type != G_FILE_MONITOR_EVENT_DELETED)
 555     g_keyfile_settings_backend_keyfile_reload (kfsb);
 556 }
 557
 558 static void
 559 dir_changed (GFileMonitor       *monitor,
 560               GFile             *file,
 561               GFile             *other_file,
 562               GFileMonitorEvent  event_type,
 563               gpointer           user_data)
 564 {
 565   GKeyfileSettingsBackend *kfsb = user_data;
 566
 567   g_keyfile_settings_backend_keyfile_writable (kfsb);
 568 }
 569
 570 /**
 571  * g_keyfile_settings_backend_new:
 572  * @filename: the filename of the keyfile
 573  * @root_path: the path under which all settings keys appear
 574  * @root_group: (nullable): the group name corresponding to
 575  *              @root_path, or %NULL
 576  *
 577  * Creates a keyfile-backed #GSettingsBackend.
 578  *
 579  * The filename of the keyfile to use is given by @filename.
 580  *
 581  * All settings read to or written from the backend must fall under the
 582  * path given in @root_path (which must start and end with a slash and
 583  * not contain two consecutive slashes).  @root_path may be "/".
 584  *
 585  * If @root_group is non-%NULL then it specifies the name of the keyfile
 586  * group used for keys that are written directly below @root_path.  For
 587  * example, if @root_path is "/apps/example/" and @root_group is
 588  * "toplevel", then settings the key "/apps/example/enabled" to a value
 589  * of %TRUE will cause the following to appear in the keyfile:
 590  *
 591  * |[
 592  *   [toplevel]
 593  *   enabled=true
 594  * ]|
 595  *
 596  * If @root_group is %NULL then it is not permitted to store keys
 597  * directly below the @root_path.
 598  *
 599  * For keys not stored directly below @root_path (ie: in a sub-path),
 600  * the name of the subpath (with the final slash stripped) is used as
 601  * the name of the keyfile group.  To continue the example, if
 602  * "/apps/example/profiles/default/font-size" were set to
 603  * 12 then the following would appear in the keyfile:
 604  *
 605  * |[
 606  *   [profiles/default]
 607  *   font-size=12
 608  * ]|
 609  *
 610  * The backend will refuse writes (and return writability as being
 611  * %FALSE) for keys outside of @root_path and, in the event that
 612  * @root_group is %NULL, also for keys directly under @root_path.
 613  * Writes will also be refused if the backend detects that it has the
 614  * inability to rewrite the keyfile (ie: the containing directory is not
 615  * writable).
 616  *
 617  * There is no checking done for your key namespace clashing with the
 618  * syntax of the key file format.  For example, if you have '[' or ']'
 619  * characters in your path names or '=' in your key names you may be in
 620  * trouble.
 621  *
 622  * Returns: (transfer full): a keyfile-backed #GSettingsBackend
 623  **/
 624 GSettingsBackend *
 625 g_keyfile_settings_backend_new (const gchar *filename,
 626                                 const gchar *root_path,
 627                                 const gchar *root_group)
 628 {
 629   GKeyfileSettingsBackend *kfsb;
 630
 631   g_return_val_if_fail (filename != NULL, NULL);
 632   g_return_val_if_fail (root_path != NULL, NULL);
 633   g_return_val_if_fail (g_str_has_prefix (root_path, "/"), NULL);
 634   g_return_val_if_fail (g_str_has_suffix (root_path, "/"), NULL);
 635   g_return_val_if_fail (strstr (root_path, "//") == NULL, NULL);
 636
 637   kfsb = g_object_new (G_TYPE_KEYFILE_SETTINGS_BACKEND, NULL);
 638   kfsb->keyfile = g_key_file_new ();
 639   kfsb->permission = g_simple_permission_new (TRUE);
 640
 641   kfsb->file = g_file_new_for_path (filename);
 642   kfsb->dir = g_file_get_parent (kfsb->file);
 643   g_file_make_directory_with_parents (kfsb->dir, NULL, NULL);
 644
 645   kfsb->file_monitor = g_file_monitor (kfsb->file, 0, NULL, NULL);
 646   kfsb->dir_monitor = g_file_monitor (kfsb->dir, 0, NULL, NULL);
 647
 648   kfsb->prefix_len = strlen (root_path);
 649   kfsb->prefix = g_strdup (root_path);
 650
 651   if (root_group)
 652     {
 653       kfsb->root_group_len = strlen (root_group);
 654       kfsb->root_group = g_strdup (root_group);
 655     }
 656
 657   compute_checksum (kfsb->digest, NULL, 0);
 658
 659   g_signal_connect (kfsb->file_monitor, "changed",
 660                     G_CALLBACK (file_changed), kfsb);
 661   g_signal_connect (kfsb->dir_monitor, "changed",
 662                     G_CALLBACK (dir_changed), kfsb);
 663
 664   g_keyfile_settings_backend_keyfile_writable (kfsb);
 665   g_keyfile_settings_backend_keyfile_reload (kfsb);
 666
 667   return G_SETTINGS_BACKEND (kfsb);
 668 }