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, write to the
  17  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18  * Boston, MA 02111-1307, USA.
  19  *
  20  * Authors: Vincent Untz <vuntz@gnome.org>
  21  *          Ryan Lortie <desrt@desrt.ca>
  22  */
  23
  24 #include "config.h"
  25
  26 #include <stdio.h>
  27 #include <string.h>
  28
  29 #include "gfile.h"
  30 #include "gfileinfo.h"
  31 #include "gfilemonitor.h"
  32 #include "gsimplepermission.h"
  33 #include "gsettingsbackend.h"
  34
  35
  36 #define G_TYPE_KEYFILE_SETTINGS_BACKEND      (g_keyfile_settings_backend_get_type ())
  37 #define G_KEYFILE_SETTINGS_BACKEND(inst)     (G_TYPE_CHECK_INSTANCE_CAST ((inst),      \
  38                                               G_TYPE_KEYFILE_SETTINGS_BACKEND,         \
  39                                               GKeyfileSettingsBackend))
  40 #define G_IS_KEYFILE_SETTINGS_BACKEND(inst)  (G_TYPE_CHECK_INSTANCE_TYPE ((inst),      \
  41                                               G_TYPE_KEYFILE_SETTINGS_BACKEND))
  42
  43
  44 typedef GSettingsBackendClass GKeyfileSettingsBackendClass;
  45
  46 typedef struct
  47 {
  48   GSettingsBackend   parent_instance;
  49
  50   GKeyFile          *keyfile;
  51   GPermission       *permission;
  52   gboolean           writable;
  53
  54   gchar             *prefix;
  55   gint               prefix_len;
  56   gchar             *root_group;
  57   gint               root_group_len;
  58
  59   GFile             *file;
  60   GFileMonitor      *file_monitor;
  61   guint8             digest[32];
  62   GFile             *dir;
  63   GFileMonitor      *dir_monitor;
  64 } GKeyfileSettingsBackend;
  65
  66 static GType g_keyfile_settings_backend_get_type (void);
  67 G_DEFINE_TYPE (GKeyfileSettingsBackend,
  68                g_keyfile_settings_backend,
  69                G_TYPE_SETTINGS_BACKEND)
  70
  71 static void
  72 compute_checksum (guint8        *digest,
  73                   gconstpointer  contents,
  74                   gsize          length)
  75 {
  76   GChecksum *checksum;
  77   gsize len = 32;
  78
  79   checksum = g_checksum_new (G_CHECKSUM_SHA256);
  80   g_checksum_update (checksum, contents, length);
  81   g_checksum_get_digest (checksum, digest, &len);
  82   g_checksum_free (checksum);
  83   g_assert (len == 32);
  84 }
  85
  86 static void
  87 g_keyfile_settings_backend_keyfile_write (GKeyfileSettingsBackend *kfsb)
  88 {
  89   gchar *contents;
  90   gsize length;
  91
  92   contents = g_key_file_to_data (kfsb->keyfile, &length, NULL);
  93   g_file_replace_contents (kfsb->file, contents, length, NULL, FALSE,
  94                            G_FILE_CREATE_REPLACE_DESTINATION,
  95                            NULL, NULL, NULL);
  96
  97   compute_checksum (kfsb->digest, contents, length);
  98   g_free (contents);
  99 }
 100
 101 static gboolean
 102 group_name_matches (const gchar *group_name,
 103                     const gchar *prefix)
 104 {
 105   /* sort of like g_str_has_prefix() except that it must be an exact
 106    * match or the prefix followed by '/'.
 107    *
 108    * for example 'a' is a prefix of 'a' and 'a/b' but not 'ab'.
 109    */
 110   gint i;
 111
 112   for (i = 0; prefix[i]; i++)
 113     if (prefix[i] != group_name[i])
 114       return FALSE;
 115
 116   return group_name[i] == '\0' || group_name[i] == '/';
 117 }
 118
 119 static gboolean
 120 convert_path (GKeyfileSettingsBackend  *kfsb,
 121               const gchar              *key,
 122               gchar                   **group,
 123               gchar                   **basename)
 124 {
 125   gint key_len = strlen (key);
 126   gint i;
 127
 128   if (key_len < kfsb->prefix_len ||
 129       memcmp (key, kfsb->prefix, kfsb->prefix_len) != 0)
 130     return FALSE;
 131
 132   key_len -= kfsb->prefix_len;
 133   key += kfsb->prefix_len;
 134
 135   for (i = key_len; i >= 0; i--)
 136     if (key[i] == '/')
 137       break;
 138
 139   if (kfsb->root_group)
 140     {
 141       /* if a root_group was specified, make sure the user hasn't given
 142        * a path that ghosts that group name
 143        */
 144       if (i == kfsb->root_group_len && memcmp (key, kfsb->root_group, i) == 0)
 145         return FALSE;
 146     }
 147   else
 148     {
 149       /* if no root_group was given, ensure that the user gave a path */
 150       if (i == -1)
 151         return FALSE;
 152     }
 153
 154   if (group)
 155     {
 156       if (i >= 0)
 157         {
 158           *group = g_memdup (key, i + 1);
 159           (*group)[i] = '\0';
 160         }
 161       else
 162         *group = g_strdup (kfsb->root_group);
 163     }
 164
 165   if (basename)
 166     *basename = g_memdup (key + i + 1, key_len - i);
 167
 168   return TRUE;
 169 }
 170
 171 static gboolean
 172 path_is_valid (GKeyfileSettingsBackend *kfsb,
 173                const gchar             *path)
 174 {
 175   return convert_path (kfsb, path, NULL, NULL);
 176 }
 177
 178 static GVariant *
 179 get_from_keyfile (GKeyfileSettingsBackend *kfsb,
 180                   const GVariantType      *type,
 181                   const gchar             *key)
 182 {
 183   GVariant *return_value = NULL;
 184   gchar *group, *name;
 185
 186   if (convert_path (kfsb, key, &group, &name))
 187     {
 188       gchar *str;
 189
 190       g_assert (*name);
 191
 192       str = g_key_file_get_value (kfsb->keyfile, group, name, NULL);
 193
 194       if (str)
 195         {
 196           return_value = g_variant_parse (type, str, NULL, NULL, NULL);
 197           g_free (str);
 198         }
 199
 200       g_free (group);
 201       g_free (name);
 202     }
 203
 204   return return_value;
 205 }
 206
 207 static gboolean
 208 set_to_keyfile (GKeyfileSettingsBackend *kfsb,
 209                 const gchar             *key,
 210                 GVariant                *value)
 211 {
 212   gchar *group, *name;
 213
 214   if (convert_path (kfsb, key, &group, &name))
 215     {
 216       if (value)
 217         {
 218           gchar *str = g_variant_print (value, FALSE);
 219           g_key_file_set_value (kfsb->keyfile, group, name, str);
 220           g_variant_unref (g_variant_ref_sink (value));
 221           g_free (str);
 222         }
 223       else
 224         {
 225           if (*name == '\0')
 226             {
 227               gchar **groups;
 228               gint i;
 229
 230               groups = g_key_file_get_groups (kfsb->keyfile, NULL);
 231
 232               for (i = 0; groups[i]; i++)
 233                 if (group_name_matches (groups[i], group))
 234                   g_key_file_remove_group (kfsb->keyfile, groups[i], NULL);
 235
 236               g_strfreev (groups);
 237             }
 238           else
 239             g_key_file_remove_key (kfsb->keyfile, group, name, NULL);
 240         }
 241
 242       g_free (group);
 243       g_free (name);
 244
 245       return TRUE;
 246     }
 247
 248   return FALSE;
 249 }
 250
 251 static GVariant *
 252 g_keyfile_settings_backend_read (GSettingsBackend   *backend,
 253                                  const gchar        *key,
 254                                  const GVariantType *expected_type,
 255                                  gboolean            default_value)
 256 {
 257   GKeyfileSettingsBackend *kfsb = G_KEYFILE_SETTINGS_BACKEND (backend);
 258
 259   if (default_value)
 260     return NULL;
 261
 262   return get_from_keyfile (kfsb, expected_type, key);
 263 }
 264
 265 typedef struct
 266 {
 267   GKeyfileSettingsBackend *kfsb;
 268   gboolean failed;
 269 } WriteManyData;
 270
 271 static gboolean
 272 g_keyfile_settings_backend_write_one (gpointer key,
 273                                       gpointer value,
 274                                       gpointer user_data)
 275 {
 276   WriteManyData *data = user_data;
 277   gboolean success;
 278
 279   success = set_to_keyfile (data->kfsb, key, value);
 280   g_assert (success);
 281
 282   return FALSE;
 283 }
 284
 285 static gboolean
 286 g_keyfile_settings_backend_check_one (gpointer key,
 287                                       gpointer value,
 288                                       gpointer user_data)
 289 {
 290   WriteManyData *data = user_data;
 291
 292   return data->failed = !path_is_valid (data->kfsb, key);
 293 }
 294
 295 static gboolean
 296 g_keyfile_settings_backend_write_tree (GSettingsBackend *backend,
 297                                        GTree            *tree,
 298                                        gpointer          origin_tag)
 299 {
 300   WriteManyData data = { G_KEYFILE_SETTINGS_BACKEND (backend) };
 301
 302   if (!data.kfsb->writable)
 303     return FALSE;
 304
 305   g_tree_foreach (tree, g_keyfile_settings_backend_check_one, &data);
 306
 307   if (data.failed)
 308     return FALSE;
 309
 310   g_tree_foreach (tree, g_keyfile_settings_backend_write_one, &data);
 311   g_keyfile_settings_backend_keyfile_write (data.kfsb);
 312
 313   g_settings_backend_changed_tree (backend, tree, origin_tag);
 314
 315   return TRUE;
 316 }
 317
 318 static gboolean
 319 g_keyfile_settings_backend_write (GSettingsBackend *backend,
 320                                   const gchar      *key,
 321                                   GVariant         *value,
 322                                   gpointer          origin_tag)
 323 {
 324   GKeyfileSettingsBackend *kfsb = G_KEYFILE_SETTINGS_BACKEND (backend);
 325   gboolean success;
 326
 327   if (!kfsb->writable)
 328     return FALSE;
 329
 330   success = set_to_keyfile (kfsb, key, value);
 331
 332   if (success)
 333     {
 334       g_settings_backend_changed (backend, key, origin_tag);
 335       g_keyfile_settings_backend_keyfile_write (kfsb);
 336     }
 337
 338   return success;
 339 }
 340
 341 static void
 342 g_keyfile_settings_backend_reset (GSettingsBackend *backend,
 343                                   const gchar      *key,
 344                                   gpointer          origin_tag)
 345 {
 346   GKeyfileSettingsBackend *kfsb = G_KEYFILE_SETTINGS_BACKEND (backend);
 347
 348   if (set_to_keyfile (kfsb, key, NULL))
 349     g_keyfile_settings_backend_keyfile_write (kfsb);
 350
 351   g_settings_backend_changed (backend, key, origin_tag);
 352 }
 353
 354 static gboolean
 355 g_keyfile_settings_backend_get_writable (GSettingsBackend *backend,
 356                                          const gchar      *name)
 357 {
 358   GKeyfileSettingsBackend *kfsb = G_KEYFILE_SETTINGS_BACKEND (backend);
 359
 360   return kfsb->writable && path_is_valid (kfsb, name);
 361 }
 362
 363 static GPermission *
 364 g_keyfile_settings_backend_get_permission (GSettingsBackend *backend,
 365                                            const gchar      *path)
 366 {
 367   GKeyfileSettingsBackend *kfsb = G_KEYFILE_SETTINGS_BACKEND (backend);
 368
 369   return g_object_ref (kfsb->permission);
 370 }
 371
 372 static void
 373 keyfile_to_tree (GKeyfileSettingsBackend *kfsb,
 374                  GTree                   *tree,
 375                  GKeyFile                *keyfile,
 376                  gboolean                 dup_check)
 377 {
 378   gchar **groups;
 379   gint i;
 380
 381   groups = g_key_file_get_groups (keyfile, NULL);
 382   for (i = 0; groups[i]; i++)
 383     {
 384       gboolean is_root_group;
 385       gchar **keys;
 386       gint j;
 387
 388       is_root_group = g_strcmp0 (kfsb->root_group, groups[i]) == 0;
 389
 390       /* reject group names that will form invalid key names */
 391       if (!is_root_group &&
 392           (g_str_has_prefix (groups[i], "/") ||
 393            g_str_has_suffix (groups[i], "/") || strstr (groups[i], "//")))
 394         continue;
 395
 396       keys = g_key_file_get_keys (keyfile, groups[i], NULL, NULL);
 397
 398       for (j = 0; keys[j]; j++)
 399         {
 400           gchar *path, *value;
 401
 402           /* reject key names with slashes in them */
 403           if (strchr (keys[j], '/'))
 404             continue;
 405
 406           if (is_root_group)
 407             path = g_strdup_printf ("%s%s", kfsb->prefix, keys[j]);
 408           else
 409             path = g_strdup_printf ("%s%s/%s", kfsb->prefix, groups[i], keys[j]);
 410
 411           value = g_key_file_get_value (keyfile, groups[i], keys[j], NULL);
 412
 413           if (dup_check && g_strcmp0 (g_tree_lookup (tree, path), value) == 0)
 414             {
 415               g_tree_remove (tree, path);
 416               g_free (value);
 417               g_free (path);
 418             }
 419           else
 420             g_tree_insert (tree, path, value);
 421         }
 422
 423       g_strfreev (keys);
 424     }
 425   g_strfreev (groups);
 426 }
 427
 428 static void
 429 g_keyfile_settings_backend_keyfile_reload (GKeyfileSettingsBackend *kfsb)
 430 {
 431   guint8 digest[32];
 432   gchar *contents;
 433   gsize length;
 434
 435   contents = NULL;
 436   length = 0;
 437
 438   g_file_load_contents (kfsb->file, NULL, &contents, &length, NULL, NULL);
 439   compute_checksum (digest, contents, length);
 440
 441   if (memcmp (kfsb->digest, digest, sizeof digest) != 0)
 442     {
 443       GKeyFile *keyfiles[2];
 444       GTree *tree;
 445
 446       tree = g_tree_new_full ((GCompareDataFunc) strcmp, NULL,
 447                               g_free, g_free);
 448
 449       keyfiles[0] = kfsb->keyfile;
 450       keyfiles[1] = g_key_file_new ();
 451
 452       if (length > 0)
 453         g_key_file_load_from_data (keyfiles[1], contents, length,
 454                                    G_KEY_FILE_KEEP_COMMENTS |
 455                                    G_KEY_FILE_KEEP_TRANSLATIONS, NULL);
 456
 457       keyfile_to_tree (kfsb, tree, keyfiles[0], FALSE);
 458       keyfile_to_tree (kfsb, tree, keyfiles[1], TRUE);
 459       g_key_file_free (keyfiles[0]);
 460       kfsb->keyfile = keyfiles[1];
 461
 462       if (g_tree_nnodes (tree) > 0)
 463         g_settings_backend_changed_tree (&kfsb->parent_instance, tree, NULL);
 464
 465       g_tree_unref (tree);
 466
 467       memcpy (kfsb->digest, digest, sizeof digest);
 468     }
 469
 470   g_free (contents);
 471 }
 472
 473 static void
 474 g_keyfile_settings_backend_keyfile_writable (GKeyfileSettingsBackend *kfsb)
 475 {
 476   GFileInfo *fileinfo;
 477   gboolean writable;
 478
 479   fileinfo = g_file_query_info (kfsb->dir, "access::*", 0, NULL, NULL);
 480
 481   if (fileinfo)
 482     {
 483       writable =
 484         g_file_info_get_attribute_boolean (fileinfo, G_FILE_ATTRIBUTE_ACCESS_CAN_WRITE) &&
 485         g_file_info_get_attribute_boolean (fileinfo, G_FILE_ATTRIBUTE_ACCESS_CAN_EXECUTE);
 486       g_object_unref (fileinfo);
 487     }
 488   else
 489     writable = FALSE;
 490
 491   if (writable != kfsb->writable)
 492     {
 493       kfsb->writable = writable;
 494       g_settings_backend_path_writable_changed (&kfsb->parent_instance, "/");
 495     }
 496 }
 497
 498 static void
 499 g_keyfile_settings_backend_finalize (GObject *object)
 500 {
 501   GKeyfileSettingsBackend *kfsb = G_KEYFILE_SETTINGS_BACKEND (object);
 502
 503   g_key_file_free (kfsb->keyfile);
 504   g_object_unref (kfsb->permission);
 505
 506   g_file_monitor_cancel (kfsb->file_monitor);
 507   g_object_unref (kfsb->file_monitor);
 508   g_object_unref (kfsb->file);
 509
 510   g_file_monitor_cancel (kfsb->dir_monitor);
 511   g_object_unref (kfsb->dir_monitor);
 512   g_object_unref (kfsb->dir);
 513
 514   g_free (kfsb->root_group);
 515   g_free (kfsb->prefix);
 516
 517   G_OBJECT_CLASS (g_keyfile_settings_backend_parent_class)
 518     ->finalize (object);
 519 }
 520
 521 static void
 522 g_keyfile_settings_backend_init (GKeyfileSettingsBackend *kfsb)
 523 {
 524 }
 525
 526 static void
 527 g_keyfile_settings_backend_class_init (GKeyfileSettingsBackendClass *class)
 528 {
 529   GObjectClass *object_class = G_OBJECT_CLASS (class);
 530
 531   object_class->finalize = g_keyfile_settings_backend_finalize;
 532
 533   class->read = g_keyfile_settings_backend_read;
 534   class->write = g_keyfile_settings_backend_write;
 535   class->write_tree = g_keyfile_settings_backend_write_tree;
 536   class->reset = g_keyfile_settings_backend_reset;
 537   class->get_writable = g_keyfile_settings_backend_get_writable;
 538   class->get_permission = g_keyfile_settings_backend_get_permission;
 539   /* No need to implement subscribed/unsubscribe: the only point would be to
 540    * stop monitoring the file when there's no GSettings anymore, which is no
 541    * big win. */
 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   g_keyfile_settings_backend_keyfile_reload (kfsb);
 554 }
 555
 556 static void
 557 dir_changed (GFileMonitor       *monitor,
 558               GFile             *file,
 559               GFile             *other_file,
 560               GFileMonitorEvent  event_type,
 561               gpointer           user_data)
 562 {
 563   GKeyfileSettingsBackend *kfsb = user_data;
 564
 565   g_keyfile_settings_backend_keyfile_writable (kfsb);
 566 }
 567
 568 /**
 569  * g_keyfile_settings_backend_new:
 570  * @filename: the filename of the keyfile
 571  * @root_path: the path under which all settings keys appear
 572  * @root_group: (allow-none): the group name corresponding to
 573  *              @root_path, or %NULL
 574  *
 575  * Creates a keyfile-backed #GSettingsBackend.
 576  *
 577  * The filename of the keyfile to use is given by @filename.
 578  *
 579  * All settings read to or written from the backend must fall under the
 580  * path given in @root_path (which must start and end with a slash and
 581  * not contain two consecutive slashes).  @root_path may be "/".
 582  *
 583  * If @root_group is non-%NULL then it specifies the name of the keyfile
 584  * group used for keys that are written directly below @root_path.  For
 585  * example, if @root_path is "/apps/example/" and @root_group is
 586  * "toplevel", then settings the key "/apps/example/enabled" to a value
 587  * of %TRUE will cause the following to appear in the keyfile:
 588  *
 589  * |[
 590  *   [toplevel]
 591  *   enabled=true
 592  * ]|
 593  *
 594  * If @root_group is %NULL then it is not permitted to store keys
 595  * directly below the @root_path.
 596  *
 597  * For keys not stored directly below @root_path (ie: in a sub-path),
 598  * the name of the subpath (with the final slash stripped) is used as
 599  * the name of the keyfile group.  To continue the example, if
 600  * "/apps/example/profiles/default/font-size" were set to
 601  * 12 then the following would appear in the keyfile:
 602  *
 603  * |[
 604  *   [profiles/default]
 605  *   font-size=12
 606  * ]|
 607  *
 608  * The backend will refuse writes (and return writability as being
 609  * %FALSE) for keys outside of @root_path and, in the event that
 610  * @root_group is %NULL, also for keys directly under @root_path.
 611  * Writes will also be refused if the backend detects that it has the
 612  * inability to rewrite the keyfile (ie: the containing directory is not
 613  * writable).
 614  *
 615  * There is no checking done for your key namespace clashing with the
 616  * syntax of the key file format.  For example, if you have '[' or ']'
 617  * characters in your path names or '=' in your key names you may be in
 618  * trouble.
 619  *
 620  * Returns: (transfer full): a keyfile-backed #GSettingsBackend
 621  **/
 622 GSettingsBackend *
 623 g_keyfile_settings_backend_new (const gchar *filename,
 624                                 const gchar *root_path,
 625                                 const gchar *root_group)
 626 {
 627   GKeyfileSettingsBackend *kfsb;
 628
 629   g_return_val_if_fail (filename != NULL, NULL);
 630   g_return_val_if_fail (root_path != NULL, NULL);
 631   g_return_val_if_fail (g_str_has_prefix (root_path, "/"), NULL);
 632   g_return_val_if_fail (g_str_has_suffix (root_path, "/"), NULL);
 633   g_return_val_if_fail (strstr (root_path, "//") == NULL, NULL);
 634
 635   kfsb = g_object_new (G_TYPE_KEYFILE_SETTINGS_BACKEND, NULL);
 636   kfsb->keyfile = g_key_file_new ();
 637   kfsb->permission = g_simple_permission_new (TRUE);
 638
 639   kfsb->file = g_file_new_for_path (filename);
 640   kfsb->dir = g_file_get_parent (kfsb->file);
 641   g_file_make_directory_with_parents (kfsb->dir, NULL, NULL);
 642
 643   kfsb->file_monitor = g_file_monitor_file (kfsb->file, 0, NULL, NULL);
 644   kfsb->dir_monitor = g_file_monitor_file (kfsb->dir, 0, NULL, NULL);
 645
 646   kfsb->prefix_len = strlen (root_path);
 647   kfsb->prefix = g_strdup (root_path);
 648
 649   if (root_group)
 650     {
 651       kfsb->root_group_len = strlen (root_group);
 652       kfsb->root_group = g_strdup (root_group);
 653     }
 654
 655   compute_checksum (kfsb->digest, NULL, 0);
 656
 657   g_signal_connect (kfsb->file_monitor, "changed",
 658                     G_CALLBACK (file_changed), kfsb);
 659   g_signal_connect (kfsb->dir_monitor, "changed",
 660                     G_CALLBACK (dir_changed), kfsb);
 661
 662   g_keyfile_settings_backend_keyfile_writable (kfsb);
 663   g_keyfile_settings_backend_keyfile_reload (kfsb);
 664
 665   return G_SETTINGS_BACKEND (kfsb);
 666 }