1 /* -*- mode: C; c-file-style: "gnu" -*- */
2 /* dbus-keyring.c Store secret cookies in your homedir
4 * Copyright (C) 2003 Red Hat Inc.
6 * Licensed under the Academic Free License version 1.2
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
24 #include "dbus-keyring.h"
25 #include <dbus/dbus-string.h>
26 #include <dbus/dbus-list.h>
27 #include <dbus/dbus-sysdeps.h>
30 * @defgroup DBusKeyring keyring class
31 * @ingroup DBusInternals
32 * @brief DBusKeyring data structure
34 * Types and functions related to DBusKeyring. DBusKeyring is intended
35 * to manage cookies used to authenticate clients to servers. This is
36 * essentially the "verify that client can read the user's homedir"
37 * authentication mechanism. Both client and server must have access
40 * The secret keys are not kept in locked memory, and are written to a
41 * file in the user's homedir. However they are transient (only used
42 * by a single server instance for a fixed period of time, then
43 * discarded). Also, the keys are not sent over the wire.
47 * @defgroup DBusKeyringInternals DBusKeyring implementation details
48 * @ingroup DBusInternals
49 * @brief DBusKeyring implementation details
51 * The guts of DBusKeyring.
56 /** The maximum age of a key before we create a new key to use in
57 * challenges. This isn't super-reliably enforced, since system
58 * clocks can change or be wrong, but we make a best effort to only
59 * use keys for a short time.
61 #define NEW_KEY_TIMEOUT_SECONDS (60*5)
63 * The time after which we drop a key from the secrets file.
64 * The EXPIRE_KEYS_TIMEOUT_SECONDS - NEW_KEY_TIMEOUT_SECONDS is the minimum
65 * time window a client has to complete authentication.
67 #define EXPIRE_KEYS_TIMEOUT_SECONDS (NEW_KEY_TIMEOUT_SECONDS + (60*2))
69 * The maximum amount of time a key can be in the future.
71 #define MAX_TIME_TRAVEL_SECONDS (60*5)
75 dbus_int32_t id; /**< identifier used to refer to the key */
77 long creation_time; /**< when the key was generated,
78 * as unix timestamp. signed long
79 * matches struct timeval.
82 DBusString secret; /**< the actual key */
87 * @brief Internals of DBusKeyring.
89 * DBusKeyring internals. DBusKeyring is an opaque object, it must be
90 * used via accessor functions.
94 int refcount; /**< Reference count */
95 DBusString directory; /**< Directory the below two items are inside */
96 DBusString filename; /**< Keyring filename */
97 DBusString filename_lock; /**< Name of lockfile */
98 DBusKey *keys; /**< Keys loaded from the file */
99 int n_keys; /**< Number of keys */
103 _dbus_keyring_new (void)
105 DBusKeyring *keyring;
107 keyring = dbus_new0 (DBusKeyring, 1);
111 if (!_dbus_string_init (&keyring->directory, _DBUS_INT_MAX))
114 if (!_dbus_string_init (&keyring->filename, _DBUS_INT_MAX))
117 if (!_dbus_string_init (&keyring->filename_lock, _DBUS_INT_MAX))
120 keyring->refcount = 1;
121 keyring->keys = NULL;
127 _dbus_string_free (&keyring->filename);
129 _dbus_string_free (&keyring->directory);
137 free_keys (DBusKey *keys,
142 /* should be safe for args NULL, 0 */
147 _dbus_string_free (&keys[i].secret);
154 /* Our locking scheme is highly unreliable. However, there is
155 * unfortunately no reliable locking scheme in user home directories;
156 * between bugs in Linux NFS, people using Tru64 or other total crap
157 * NFS, AFS, random-file-system-of-the-week, and so forth, fcntl() in
158 * homedirs simply generates tons of bug reports. This has been
159 * learned through hard experience with GConf, unfortunately.
161 * This bad hack might work better for the kind of lock we have here,
162 * which we don't expect to hold for any length of time. Crashing
163 * while we hold it should be unlikely, and timing out such that we
164 * delete a stale lock should also be unlikely except when the
165 * filesystem is running really slowly. Stuff might break in corner
166 * cases but as long as it's not a security-level breakage it should
170 /** Maximum number of timeouts waiting for lock before we decide it's stale */
171 #define MAX_LOCK_TIMEOUTS 32
172 /** Length of each timeout while waiting for a lock */
173 #define LOCK_TIMEOUT_MILLISECONDS 250
176 _dbus_keyring_lock (DBusKeyring *keyring)
181 while (n_timeouts < MAX_LOCK_TIMEOUTS)
185 dbus_error_init (&error);
186 if (_dbus_create_file_exclusively (&keyring->filename_lock,
190 _dbus_verbose ("Did not get lock file, sleeping %d milliseconds (%s)\n",
191 LOCK_TIMEOUT_MILLISECONDS, error.message);
192 dbus_error_free (&error);
194 _dbus_sleep_milliseconds (LOCK_TIMEOUT_MILLISECONDS);
199 if (n_timeouts == MAX_LOCK_TIMEOUTS)
203 _dbus_verbose ("Lock file timed out %d times, assuming stale\n",
206 dbus_error_init (&error);
208 if (!_dbus_delete_file (&keyring->filename_lock, &error))
210 _dbus_verbose ("Couldn't delete old lock file: %s\n",
212 dbus_error_free (&error);
216 if (!_dbus_create_file_exclusively (&keyring->filename_lock,
219 _dbus_verbose ("Couldn't create lock file after deleting stale one: %s\n",
221 dbus_error_free (&error);
230 _dbus_keyring_unlock (DBusKeyring *keyring)
233 dbus_error_init (&error);
234 if (!_dbus_delete_file (&keyring->filename_lock, &error))
236 _dbus_warn ("Failed to delete lock file: %s\n",
238 dbus_error_free (&error);
243 find_key_by_id (DBusKey *keys,
252 if (keys[i].id == id)
262 add_new_key (DBusKey **keys_p,
269 unsigned long timestamp;
270 const unsigned char *s;
275 if (!_dbus_string_init (&bytes, _DBUS_INT_MAX))
277 dbus_set_error (error, DBUS_ERROR_NO_MEMORY,
278 "No memory to generate new secret key");
286 /* Generate an integer ID and then the actual key. */
289 if (!_dbus_generate_random_bytes (&bytes, 4))
291 dbus_set_error (error, DBUS_ERROR_NO_MEMORY,
292 "No memory to generate new secret key");
296 _dbus_string_get_const_data (&bytes, (const char**) &s);
298 id = s[0] | (s[1] << 8) | (s[2] << 16) | (s[3] << 24);
301 _dbus_assert (id >= 0);
303 if (find_key_by_id (keys, n_keys, id) != NULL)
305 _dbus_string_set_length (&bytes, 0);
306 _dbus_verbose ("Key ID %d already existed, trying another one\n",
311 _dbus_verbose ("Creating key with ID %d\n", id);
313 #define KEY_LENGTH_BYTES 24
314 _dbus_string_set_length (&bytes, 0);
315 if (!_dbus_generate_random_bytes (&bytes, KEY_LENGTH_BYTES))
317 dbus_set_error (error, DBUS_ERROR_NO_MEMORY,
318 "No memory to generate new secret key");
322 new = dbus_realloc (keys, sizeof (DBusKey) * (n_keys + 1));
325 dbus_set_error (error, DBUS_ERROR_NO_MEMORY,
326 "No memory to reallocate secret key list");
333 if (!_dbus_string_init (&keys[n_keys-1].secret,
336 n_keys -= 1; /* we don't want to free the one we didn't init */
337 dbus_set_error (error, DBUS_ERROR_NO_MEMORY,
338 "No memory to store secret key");
342 _dbus_get_current_time (×tamp, NULL);
344 keys[n_keys-1].id = id;
345 keys[n_keys-1].creation_time = timestamp;
346 if (!_dbus_string_move (&bytes, 0,
347 &keys[n_keys-1].secret,
350 dbus_set_error (error, DBUS_ERROR_NO_MEMORY,
351 "No memory to store secret key");
364 _dbus_string_free (&bytes);
369 * Reloads the keyring file, optionally adds one new key to the file,
370 * removes all expired keys from the file iff a key was added, then
371 * resaves the file. Stores the keys from the file in keyring->keys.
372 * Note that the file is only resaved (written to) if a key is added,
373 * this means that only servers ever write to the file and need to
374 * lock it, which avoids a lot of lock contention at login time and
377 * @param keyring the keyring
378 * @param add_new #TRUE to add a new key to the file, expire keys, and resave
379 * @param error return location for errors
380 * @returns #FALSE on failure
383 _dbus_keyring_reload (DBusKeyring *keyring,
389 DBusResultCode result;
391 dbus_bool_t have_lock;
397 if (!_dbus_string_init (&contents, _DBUS_INT_MAX))
399 dbus_set_error (error, DBUS_ERROR_NO_MEMORY,
400 "No memory to reload keyring");
404 if (!_dbus_string_init (&line, _DBUS_INT_MAX))
406 dbus_set_error (error, DBUS_ERROR_NO_MEMORY,
407 "No memory to reload keyring");
408 _dbus_string_free (&contents);
417 _dbus_get_current_time (&now, NULL);
421 if (!_dbus_keyring_lock (keyring))
423 dbus_set_error (error, DBUS_ERROR_FAILED,
424 "Could not lock keyring file to add to it");
431 result = _dbus_file_get_contents (&contents,
434 if (result != DBUS_RESULT_SUCCESS)
436 _dbus_verbose ("Failed to load keyring file: %s\n",
437 dbus_result_to_string (result));
438 /* continue with empty keyring file, so we recreate it */
441 if (!_dbus_string_validate_ascii (&contents, 0,
442 _dbus_string_get_length (&contents)))
444 _dbus_warn ("Secret keyring file contains non-ASCII! Ignoring existing contents\n");
445 _dbus_string_set_length (&contents, 0);
448 while (_dbus_string_pop_line (&contents, &line))
458 if (!_dbus_string_parse_int (&line, 0, &val, &next))
460 _dbus_verbose ("could not parse secret key ID at start of line\n");
464 if (val > _DBUS_INT_MAX || val < 0)
466 _dbus_verbose ("invalid secret key ID at start of line\n");
472 _dbus_string_skip_blank (&line, next, &next);
474 if (!_dbus_string_parse_int (&line, next, ×tamp, &next))
476 _dbus_verbose ("could not parse secret key timestamp\n");
481 (now + MAX_TIME_TRAVEL_SECONDS) < timestamp ||
482 (now - EXPIRE_KEYS_TIMEOUT_SECONDS) > timestamp)
484 _dbus_verbose ("dropping/ignoring %ld-seconds old key with timestamp %ld as current time is %ld\n",
485 now - timestamp, timestamp, now);
489 _dbus_string_skip_blank (&line, next, &next);
491 len = _dbus_string_get_length (&line);
493 if ((len - next) == 0)
495 _dbus_verbose ("no secret key after ID and timestamp\n");
499 /* We have all three parts */
500 new = dbus_realloc (keys, sizeof (DBusKey) * (n_keys + 1));
503 dbus_set_error (error, DBUS_ERROR_NO_MEMORY,
504 "No memory to reallocate secret key list");
511 if (!_dbus_string_init (&keys[n_keys-1].secret,
514 n_keys -= 1; /* we don't want to free the one we didn't init */
515 dbus_set_error (error, DBUS_ERROR_NO_MEMORY,
516 "No memory to store secret key");
520 keys[n_keys-1].id = id;
521 keys[n_keys-1].creation_time = timestamp;
522 if (!_dbus_string_hex_decode (&line, next,
523 &keys[n_keys-1].secret,
526 dbus_set_error (error, DBUS_ERROR_NO_MEMORY,
527 "No memory to store secret key or invalid hex encoding");
532 _dbus_verbose ("Successfully loaded %d existing keys\n",
537 if (!add_new_key (&keys, &n_keys, error))
539 _dbus_verbose ("Failed to generate new key: %s\n",
540 error ? "(unknown)" : error->message);
544 _dbus_string_set_length (&contents, 0);
549 if (!_dbus_string_append_int (&contents,
553 if (!_dbus_string_append_byte (&contents, ' '))
556 if (!_dbus_string_append_int (&contents,
557 keys[i].creation_time))
560 if (!_dbus_string_append_byte (&contents, ' '))
563 if (!_dbus_string_hex_encode (&keys[i].secret, 0,
565 _dbus_string_get_length (&contents)))
568 if (!_dbus_string_append_byte (&contents, '\n'))
575 dbus_set_error (error, DBUS_ERROR_NO_MEMORY,
576 "No memory to save secret keyring");
580 result = _dbus_string_save_to_file (&contents, &keyring->filename);
581 if (result != DBUS_RESULT_SUCCESS)
583 dbus_set_error (error, DBUS_ERROR_FAILED,
584 "Failed to save keyring file: %s",
585 dbus_result_to_string (result));
590 dbus_free (keyring->keys);
591 keyring->keys = keys;
592 keyring->n_keys = n_keys;
600 _dbus_keyring_unlock (keyring);
602 if (! ((retval == TRUE && (error == NULL || error->name == NULL)) ||
603 (retval == FALSE && (error == NULL || error->name != NULL))))
605 if (error && error->name)
606 _dbus_verbose ("error is %s: %s\n", error->name, error->message);
607 _dbus_warn ("returning %d but error pointer %p name %s\n",
608 retval, error, error->name ? error->name : "(none)");
609 _dbus_assert_not_reached ("didn't handle errors properly");
617 _dbus_string_free (&keys[i].secret);
624 _dbus_string_free (&contents);
625 _dbus_string_free (&line);
630 /** @} */ /* end of internals */
633 * @addtogroup DBusKeyring
639 * Increments reference count of the keyring
641 * @param keyring the keyring
644 _dbus_keyring_ref (DBusKeyring *keyring)
646 keyring->refcount += 1;
650 * Decrements refcount and finalizes if it reaches
653 * @param keyring the keyring
656 _dbus_keyring_unref (DBusKeyring *keyring)
658 keyring->refcount -= 1;
660 if (keyring->refcount == 0)
662 _dbus_string_free (&keyring->filename);
663 _dbus_string_free (&keyring->filename_lock);
664 _dbus_string_free (&keyring->directory);
665 free_keys (keyring->keys, keyring->n_keys);
671 * Creates a new keyring that lives in the ~/.dbus-keyrings
672 * directory of the given user. If the username is #NULL,
673 * uses the user owning the current process.
675 * @param username username to get keyring for, or #NULL
676 * @param context which keyring to get
677 * @param error return location for errors
678 * @returns the keyring or #NULL on error
681 _dbus_keyring_new_homedir (const DBusString *username,
682 const DBusString *context,
686 DBusKeyring *keyring;
687 dbus_bool_t error_set;
694 if (!_dbus_string_init (&homedir, _DBUS_INT_MAX))
697 _dbus_string_init_const (&dotdir, ".dbus-keyrings");
699 if (username == NULL)
701 const DBusString *const_homedir;
703 if (!_dbus_user_info_from_current_process (&username,
708 if (!_dbus_string_copy (const_homedir, 0,
714 if (!_dbus_homedir_from_username (username, &homedir))
718 keyring = _dbus_keyring_new ();
722 /* should have been validated already, but paranoia check here */
723 if (!_dbus_keyring_validate_context (context))
726 dbus_set_error_const (error,
728 "Invalid context in keyring creation");
732 if (!_dbus_string_copy (&homedir, 0,
733 &keyring->directory, 0))
736 if (!_dbus_concat_dir_and_file (&keyring->directory,
740 if (!_dbus_string_copy (&keyring->directory, 0,
741 &keyring->filename, 0))
744 if (!_dbus_concat_dir_and_file (&keyring->filename,
748 if (!_dbus_string_copy (&keyring->filename, 0,
749 &keyring->filename_lock, 0))
752 if (!_dbus_string_append (&keyring->filename_lock, ".lock"))
755 dbus_error_init (&tmp_error);
756 if (!_dbus_keyring_reload (keyring, FALSE, &tmp_error))
758 _dbus_verbose ("didn't load an existing keyring: %s\n",
760 dbus_error_free (&tmp_error);
763 /* We don't fail fatally if we can't create the directory,
764 * but the keyring will probably always be empty
765 * unless someone else manages to create it
767 dbus_error_init (&tmp_error);
768 if (!_dbus_create_directory (&keyring->directory,
771 _dbus_verbose ("Creating keyring directory: %s\n",
773 dbus_error_free (&tmp_error);
780 dbus_set_error_const (error,
781 DBUS_ERROR_NO_MEMORY,
782 "No memory to create keyring");
784 _dbus_keyring_unref (keyring);
785 _dbus_string_free (&homedir);
791 * Checks whether the context is a valid context.
792 * Contexts that might cause confusion when used
793 * in filenames are not allowed (contexts can't
794 * start with a dot or contain dir separators).
796 * @param context the context
797 * @returns #TRUE if valid
800 _dbus_keyring_validate_context (const DBusString *context)
802 if (_dbus_string_get_length (context) == 0)
804 _dbus_verbose ("context is zero-length\n");
808 if (!_dbus_string_validate_ascii (context, 0,
809 _dbus_string_get_length (context)))
811 _dbus_verbose ("context not valid ascii\n");
815 /* no directory separators */
816 if (_dbus_string_find (context, 0, "/", NULL))
818 _dbus_verbose ("context contains a slash\n");
822 if (_dbus_string_find (context, 0, "\\", NULL))
824 _dbus_verbose ("context contains a backslash\n");
828 /* prevent attempts to use dotfiles or ".." or ".lock"
829 * all of which might allow some kind of attack
831 if (_dbus_string_find (context, 0, ".", NULL))
833 _dbus_verbose ("context contains a dot\n");
841 find_recent_key (DBusKeyring *keyring)
844 long tv_sec, tv_usec;
846 _dbus_get_current_time (&tv_sec, &tv_usec);
849 while (i < keyring->n_keys)
851 DBusKey *key = &keyring->keys[i];
853 _dbus_verbose ("Key %d is %ld seconds old\n",
854 i, tv_sec - key->creation_time);
856 if ((tv_sec - NEW_KEY_TIMEOUT_SECONDS) < key->creation_time)
866 * Gets a recent key to use for authentication.
867 * If no recent key exists, creates one. Returns
868 * the key ID. If a key can't be written to the keyring
869 * file so no recent key can be created, returns -1.
870 * All valid keys are > 0.
872 * @param keyring the keyring
873 * @param error error on failure
874 * @returns key ID to use for auth, or -1 on failure
877 _dbus_keyring_get_best_key (DBusKeyring *keyring,
882 key = find_recent_key (keyring);
886 /* All our keys are too old, or we've never loaded the
887 * keyring. Create a new one.
889 if (!_dbus_keyring_reload (keyring, TRUE,
893 key = find_recent_key (keyring);
898 dbus_set_error_const (error,
900 "No recent-enough key found in keyring, and unable to create a new key");
905 /** @} */ /* end of exposed API */
907 #ifdef DBUS_BUILD_TESTS
908 #include "dbus-test.h"
912 _dbus_keyring_test (void)
924 /* Context validation */
926 _dbus_string_init_const (&context, "foo");
927 _dbus_assert (_dbus_keyring_validate_context (&context));
928 _dbus_string_init_const (&context, "org_freedesktop_blah");
929 _dbus_assert (_dbus_keyring_validate_context (&context));
931 _dbus_string_init_const (&context, "");
932 _dbus_assert (!_dbus_keyring_validate_context (&context));
933 _dbus_string_init_const (&context, ".foo");
934 _dbus_assert (!_dbus_keyring_validate_context (&context));
935 _dbus_string_init_const (&context, "bar.foo");
936 _dbus_assert (!_dbus_keyring_validate_context (&context));
937 _dbus_string_init_const (&context, "bar/foo");
938 _dbus_assert (!_dbus_keyring_validate_context (&context));
939 _dbus_string_init_const (&context, "bar\\foo");
940 _dbus_assert (!_dbus_keyring_validate_context (&context));
941 _dbus_string_init_const (&context, "foo\xfa\xf0");
942 _dbus_assert (!_dbus_keyring_validate_context (&context));
943 _dbus_string_init_const (&context, "foo\x80");
944 _dbus_assert (!_dbus_keyring_validate_context (&context));
945 _dbus_string_init_const (&context, "foo\x7f");
946 _dbus_assert (_dbus_keyring_validate_context (&context));
948 if (!_dbus_string_init (&context, _DBUS_INT_MAX))
949 _dbus_assert_not_reached ("no memory");
950 if (!_dbus_string_append_byte (&context, '\0'))
951 _dbus_assert_not_reached ("no memory");
952 _dbus_assert (!_dbus_keyring_validate_context (&context));
953 _dbus_string_free (&context);
955 /* Now verify that if we create a key in keyring 1,
956 * it is properly loaded in keyring 2
959 _dbus_string_init_const (&context, "org_freedesktop_dbus_testsuite");
960 dbus_error_init (&error);
961 ring1 = _dbus_keyring_new_homedir (NULL, &context,
963 _dbus_assert (ring1);
964 _dbus_assert (error.name == NULL);
966 id = _dbus_keyring_get_best_key (ring1, &error);
969 fprintf (stderr, "Could not load keyring: %s\n", error.message);
970 dbus_error_free (&error);
974 ring2 = _dbus_keyring_new_homedir (NULL, &context, &error);
975 _dbus_assert (ring2);
976 _dbus_assert (error.name == NULL);
978 if (ring1->n_keys != ring2->n_keys)
980 fprintf (stderr, "Different number of keys in keyrings\n");
984 /* We guarantee we load and save keeping keys in a fixed
988 while (i < ring1->n_keys)
990 if (ring1->keys[i].id != ring2->keys[i].id)
992 fprintf (stderr, "Keyring 1 has first key ID %d and keyring 2 has %d\n",
993 ring1->keys[i].id, ring2->keys[i].id);
997 if (ring1->keys[i].creation_time != ring2->keys[i].creation_time)
999 fprintf (stderr, "Keyring 1 has first key time %ld and keyring 2 has %ld\n",
1000 ring1->keys[i].creation_time, ring2->keys[i].creation_time);
1004 if (!_dbus_string_equal (&ring1->keys[i].secret,
1005 &ring2->keys[i].secret))
1007 fprintf (stderr, "Keyrings 1 and 2 have different secrets for same ID/timestamp\n");
1014 printf (" %d keys in test\n", ring1->n_keys);
1020 _dbus_keyring_unref (ring1);
1022 _dbus_keyring_unref (ring2);
1027 #endif /* DBUS_BUILD_TESTS */