entrynodes.c 117 KB

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  1. /* Copyright (c) 2001 Matej Pfajfar.
  2. * Copyright (c) 2001-2004, Roger Dingledine.
  3. * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
  4. * Copyright (c) 2007-2017, The Tor Project, Inc. */
  5. /* See LICENSE for licensing information */
  6. /**
  7. * \file entrynodes.c
  8. * \brief Code to manage our fixed first nodes for various functions.
  9. *
  10. * Entry nodes can be guards (for general use) or bridges (for censorship
  11. * circumvention).
  12. *
  13. * In general, we use entry guards to prevent traffic-sampling attacks:
  14. * if we chose every circuit independently, an adversary controlling
  15. * some fraction of paths on the network would observe a sample of every
  16. * user's traffic. Using guards gives users a chance of not being
  17. * profiled.
  18. *
  19. * The current entry guard selection code is designed to try to avoid
  20. * _ever_ trying every guard on the network, to try to stick to guards
  21. * that we've used before, to handle hostile/broken networks, and
  22. * to behave sanely when the network goes up and down.
  23. *
  24. * Our algorithm works as follows: First, we maintain a SAMPLE of guards
  25. * we've seen in the networkstatus consensus. We maintain this sample
  26. * over time, and store it persistently; it is chosen without reference
  27. * to our configuration or firewall rules. Guards remain in the sample
  28. * as they enter and leave the consensus. We expand this sample as
  29. * needed, up to a maximum size.
  30. *
  31. * As a subset of the sample, we maintain a FILTERED SET of the guards
  32. * that we would be willing to use if we could connect to them. The
  33. * filter removes all the guards that we're excluding because they're
  34. * bridges (or not bridges), because we have restrictive firewall rules,
  35. * because of ExcludeNodes, because we of path bias restrictions,
  36. * because they're absent from the network at present, and so on.
  37. *
  38. * As a subset of the filtered set, we keep a REACHABLE FILTERED SET
  39. * (also called a "usable filtered set") of those guards that we call
  40. * "reachable" or "maybe reachable". A guard is reachable if we've
  41. * connected to it more recently than we've failed. A guard is "maybe
  42. * reachable" if we have never tried to connect to it, or if we
  43. * failed to connect to it so long ago that we no longer think our
  44. * failure means it's down.
  45. *
  46. * As a persistent ordered list whose elements are taken from the
  47. * sampled set, we track a CONFIRMED GUARDS LIST. A guard becomes
  48. * confirmed when we successfully build a circuit through it, and decide
  49. * to use that circuit. We order the guards on this list by the order
  50. * in which they became confirmed.
  51. *
  52. * And as a final group, we have an ordered list of PRIMARY GUARDS,
  53. * whose elements are taken from the filtered set. We prefer
  54. * confirmed guards to non-confirmed guards for this list, and place
  55. * other restrictions on it. The primary guards are the ones that we
  56. * connect to "when nothing is wrong" -- circuits through them can be used
  57. * immediately.
  58. *
  59. * To build circuits, we take a primary guard if possible -- or a
  60. * reachable filtered confirmed guard if no primary guard is possible --
  61. * or a random reachable filtered guard otherwise. If the guard is
  62. * primary, we can use the circuit immediately on success. Otherwise,
  63. * the guard is now "pending" -- we won't use its circuit unless all
  64. * of the circuits we're trying to build through better guards have
  65. * definitely failed.
  66. *
  67. * While we're building circuits, we track a little "guard state" for
  68. * each circuit. We use this to keep track of whether the circuit is
  69. * one that we can use as soon as it's done, or whether it's one that
  70. * we should keep around to see if we can do better. In the latter case,
  71. * a periodic call to entry_guards_upgrade_waiting_circuits() will
  72. * eventually upgrade it.
  73. **/
  74. /* DOCDOC -- expand this.
  75. *
  76. * Information invariants:
  77. *
  78. * [x] whenever a guard becomes unreachable, clear its usable_filtered flag.
  79. *
  80. * [x] Whenever a guard becomes reachable or maybe-reachable, if its filtered
  81. * flag is set, set its usable_filtered flag.
  82. *
  83. * [x] Whenever we get a new consensus, call update_from_consensus(). (LATER.)
  84. *
  85. * [x] Whenever the configuration changes in a relevant way, update the
  86. * filtered/usable flags. (LATER.)
  87. *
  88. * [x] Whenever we add a guard to the sample, make sure its filtered/usable
  89. * flags are set as possible.
  90. *
  91. * [x] Whenever we remove a guard from the sample, remove it from the primary
  92. * and confirmed lists.
  93. *
  94. * [x] When we make a guard confirmed, update the primary list.
  95. *
  96. * [x] When we make a guard filtered or unfiltered, update the primary list.
  97. *
  98. * [x] When we are about to pick a guard, make sure that the primary list is
  99. * full.
  100. *
  101. * [x] Before calling sample_reachable_filtered_entry_guards(), make sure
  102. * that the filtered, primary, and confirmed flags are up-to-date.
  103. *
  104. * [x] Call entry_guard_consider_retry every time we are about to check
  105. * is_usable_filtered or is_reachable, and every time we set
  106. * is_filtered to 1.
  107. *
  108. * [x] Call entry_guards_changed_for_guard_selection() whenever we update
  109. * a persistent field.
  110. */
  111. #define ENTRYNODES_PRIVATE
  112. #include "or.h"
  113. #include "channel.h"
  114. #include "bridges.h"
  115. #include "circpathbias.h"
  116. #include "circuitbuild.h"
  117. #include "circuitlist.h"
  118. #include "circuitstats.h"
  119. #include "config.h"
  120. #include "confparse.h"
  121. #include "connection.h"
  122. #include "control.h"
  123. #include "directory.h"
  124. #include "entrynodes.h"
  125. #include "main.h"
  126. #include "microdesc.h"
  127. #include "networkstatus.h"
  128. #include "nodelist.h"
  129. #include "policies.h"
  130. #include "router.h"
  131. #include "routerlist.h"
  132. #include "routerparse.h"
  133. #include "routerset.h"
  134. #include "transports.h"
  135. #include "statefile.h"
  136. /** A list of existing guard selection contexts. */
  137. static smartlist_t *guard_contexts = NULL;
  138. /** The currently enabled guard selection context. */
  139. static guard_selection_t *curr_guard_context = NULL;
  140. /** A value of 1 means that at least one context has changed,
  141. * and those changes need to be flushed to disk. */
  142. static int entry_guards_dirty = 0;
  143. static void entry_guard_set_filtered_flags(const or_options_t *options,
  144. guard_selection_t *gs,
  145. entry_guard_t *guard);
  146. static void pathbias_check_use_success_count(entry_guard_t *guard);
  147. static void pathbias_check_close_success_count(entry_guard_t *guard);
  148. static int node_is_possible_guard(const node_t *node);
  149. static int node_passes_guard_filter(const or_options_t *options,
  150. const node_t *node);
  151. static entry_guard_t *entry_guard_add_to_sample_impl(guard_selection_t *gs,
  152. const uint8_t *rsa_id_digest,
  153. const char *nickname,
  154. const tor_addr_port_t *bridge_addrport);
  155. static entry_guard_t *get_sampled_guard_by_bridge_addr(guard_selection_t *gs,
  156. const tor_addr_port_t *addrport);
  157. static int entry_guard_obeys_restriction(const entry_guard_t *guard,
  158. const entry_guard_restriction_t *rst);
  159. /** Return 0 if we should apply guardfraction information found in the
  160. * consensus. A specific consensus can be specified with the
  161. * <b>ns</b> argument, if NULL the most recent one will be picked.*/
  162. int
  163. should_apply_guardfraction(const networkstatus_t *ns)
  164. {
  165. /* We need to check the corresponding torrc option and the consensus
  166. * parameter if we need to. */
  167. const or_options_t *options = get_options();
  168. /* If UseGuardFraction is 'auto' then check the same-named consensus
  169. * parameter. If the consensus parameter is not present, default to
  170. * "off". */
  171. if (options->UseGuardFraction == -1) {
  172. return networkstatus_get_param(ns, "UseGuardFraction",
  173. 0, /* default to "off" */
  174. 0, 1);
  175. }
  176. return options->UseGuardFraction;
  177. }
  178. /** Return true iff we know a descriptor for <b>guard</b> */
  179. static int
  180. guard_has_descriptor(const entry_guard_t *guard)
  181. {
  182. const node_t *node = node_get_by_id(guard->identity);
  183. if (!node)
  184. return 0;
  185. return node_has_descriptor(node);
  186. }
  187. /**
  188. * Try to determine the correct type for a selection named "name",
  189. * if <b>type</b> is GS_TYPE_INFER.
  190. */
  191. STATIC guard_selection_type_t
  192. guard_selection_infer_type(guard_selection_type_t type,
  193. const char *name)
  194. {
  195. if (type == GS_TYPE_INFER) {
  196. if (!strcmp(name, "bridges"))
  197. type = GS_TYPE_BRIDGE;
  198. else if (!strcmp(name, "restricted"))
  199. type = GS_TYPE_RESTRICTED;
  200. else
  201. type = GS_TYPE_NORMAL;
  202. }
  203. return type;
  204. }
  205. /**
  206. * Allocate and return a new guard_selection_t, with the name <b>name</b>.
  207. */
  208. STATIC guard_selection_t *
  209. guard_selection_new(const char *name,
  210. guard_selection_type_t type)
  211. {
  212. guard_selection_t *gs;
  213. type = guard_selection_infer_type(type, name);
  214. gs = tor_malloc_zero(sizeof(*gs));
  215. gs->name = tor_strdup(name);
  216. gs->type = type;
  217. gs->sampled_entry_guards = smartlist_new();
  218. gs->confirmed_entry_guards = smartlist_new();
  219. gs->primary_entry_guards = smartlist_new();
  220. return gs;
  221. }
  222. /**
  223. * Return the guard selection called <b>name</b>. If there is none, and
  224. * <b>create_if_absent</b> is true, then create and return it. If there
  225. * is none, and <b>create_if_absent</b> is false, then return NULL.
  226. */
  227. STATIC guard_selection_t *
  228. get_guard_selection_by_name(const char *name,
  229. guard_selection_type_t type,
  230. int create_if_absent)
  231. {
  232. if (!guard_contexts) {
  233. guard_contexts = smartlist_new();
  234. }
  235. SMARTLIST_FOREACH_BEGIN(guard_contexts, guard_selection_t *, gs) {
  236. if (!strcmp(gs->name, name))
  237. return gs;
  238. } SMARTLIST_FOREACH_END(gs);
  239. if (! create_if_absent)
  240. return NULL;
  241. log_debug(LD_GUARD, "Creating a guard selection called %s", name);
  242. guard_selection_t *new_selection = guard_selection_new(name, type);
  243. smartlist_add(guard_contexts, new_selection);
  244. return new_selection;
  245. }
  246. /**
  247. * Allocate the first guard context that we're planning to use,
  248. * and make it the current context.
  249. */
  250. static void
  251. create_initial_guard_context(void)
  252. {
  253. tor_assert(! curr_guard_context);
  254. if (!guard_contexts) {
  255. guard_contexts = smartlist_new();
  256. }
  257. guard_selection_type_t type = GS_TYPE_INFER;
  258. const char *name = choose_guard_selection(
  259. get_options(),
  260. networkstatus_get_live_consensus(approx_time()),
  261. NULL,
  262. &type);
  263. tor_assert(name); // "name" can only be NULL if we had an old name.
  264. tor_assert(type != GS_TYPE_INFER);
  265. log_notice(LD_GUARD, "Starting with guard context \"%s\"", name);
  266. curr_guard_context = get_guard_selection_by_name(name, type, 1);
  267. }
  268. /** Get current default guard_selection_t, creating it if necessary */
  269. guard_selection_t *
  270. get_guard_selection_info(void)
  271. {
  272. if (!curr_guard_context) {
  273. create_initial_guard_context();
  274. }
  275. return curr_guard_context;
  276. }
  277. /** Return a statically allocated human-readable description of <b>guard</b>
  278. */
  279. const char *
  280. entry_guard_describe(const entry_guard_t *guard)
  281. {
  282. static char buf[256];
  283. tor_snprintf(buf, sizeof(buf),
  284. "%s ($%s)",
  285. strlen(guard->nickname) ? guard->nickname : "[bridge]",
  286. hex_str(guard->identity, DIGEST_LEN));
  287. return buf;
  288. }
  289. /** Return <b>guard</b>'s 20-byte RSA identity digest */
  290. const char *
  291. entry_guard_get_rsa_id_digest(const entry_guard_t *guard)
  292. {
  293. return guard->identity;
  294. }
  295. /** Return the pathbias state associated with <b>guard</b>. */
  296. guard_pathbias_t *
  297. entry_guard_get_pathbias_state(entry_guard_t *guard)
  298. {
  299. return &guard->pb;
  300. }
  301. HANDLE_IMPL(entry_guard, entry_guard_t, ATTR_UNUSED STATIC)
  302. /** Return an interval betweeen 'now' and 'max_backdate' seconds in the past,
  303. * chosen uniformly at random. We use this before recording persistent
  304. * dates, so that we aren't leaking exactly when we recorded it.
  305. */
  306. MOCK_IMPL(STATIC time_t,
  307. randomize_time,(time_t now, time_t max_backdate))
  308. {
  309. tor_assert(max_backdate > 0);
  310. time_t earliest = now - max_backdate;
  311. time_t latest = now;
  312. if (earliest <= 0)
  313. earliest = 1;
  314. if (latest <= earliest)
  315. latest = earliest + 1;
  316. return crypto_rand_time_range(earliest, latest);
  317. }
  318. /**
  319. * @name parameters for networkstatus algorithm
  320. *
  321. * These parameters are taken from the consensus; some are overrideable in
  322. * the torrc.
  323. */
  324. /**@{*/
  325. /**
  326. * We never let our sampled guard set grow larger than this fraction
  327. * of the guards on the network.
  328. */
  329. STATIC double
  330. get_max_sample_threshold(void)
  331. {
  332. int32_t pct =
  333. networkstatus_get_param(NULL, "guard-max-sample-threshold-percent",
  334. DFLT_MAX_SAMPLE_THRESHOLD_PERCENT,
  335. 1, 100);
  336. return pct / 100.0;
  337. }
  338. /**
  339. * We never let our sampled guard set grow larger than this number.
  340. */
  341. STATIC int
  342. get_max_sample_size_absolute(void)
  343. {
  344. return (int) networkstatus_get_param(NULL, "guard-max-sample-size",
  345. DFLT_MAX_SAMPLE_SIZE,
  346. 1, INT32_MAX);
  347. }
  348. /**
  349. * We always try to make our sample contain at least this many guards.
  350. */
  351. STATIC int
  352. get_min_filtered_sample_size(void)
  353. {
  354. return networkstatus_get_param(NULL, "guard-min-filtered-sample-size",
  355. DFLT_MIN_FILTERED_SAMPLE_SIZE,
  356. 1, INT32_MAX);
  357. }
  358. /**
  359. * If a guard is unlisted for this many days in a row, we remove it.
  360. */
  361. STATIC int
  362. get_remove_unlisted_guards_after_days(void)
  363. {
  364. return networkstatus_get_param(NULL,
  365. "guard-remove-unlisted-guards-after-days",
  366. DFLT_REMOVE_UNLISTED_GUARDS_AFTER_DAYS,
  367. 1, 365*10);
  368. }
  369. /**
  370. * We remove unconfirmed guards from the sample after this many days,
  371. * regardless of whether they are listed or unlisted.
  372. */
  373. STATIC int
  374. get_guard_lifetime(void)
  375. {
  376. if (get_options()->GuardLifetime >= 86400)
  377. return get_options()->GuardLifetime;
  378. int32_t days;
  379. days = networkstatus_get_param(NULL,
  380. "guard-lifetime-days",
  381. DFLT_GUARD_LIFETIME_DAYS, 1, 365*10);
  382. return days * 86400;
  383. }
  384. /**
  385. * We remove confirmed guards from the sample if they were sampled
  386. * GUARD_LIFETIME_DAYS ago and confirmed this many days ago.
  387. */
  388. STATIC int
  389. get_guard_confirmed_min_lifetime(void)
  390. {
  391. if (get_options()->GuardLifetime >= 86400)
  392. return get_options()->GuardLifetime;
  393. int32_t days;
  394. days = networkstatus_get_param(NULL, "guard-confirmed-min-lifetime-days",
  395. DFLT_GUARD_CONFIRMED_MIN_LIFETIME_DAYS,
  396. 1, 365*10);
  397. return days * 86400;
  398. }
  399. /**
  400. * How many guards do we try to keep on our primary guard list?
  401. */
  402. STATIC int
  403. get_n_primary_guards(void)
  404. {
  405. const int n = get_options()->NumEntryGuards;
  406. const int n_dir = get_options()->NumDirectoryGuards;
  407. if (n > 5) {
  408. return MAX(n_dir, n + n / 2);
  409. } else if (n >= 1) {
  410. return MAX(n_dir, n * 2);
  411. }
  412. return networkstatus_get_param(NULL,
  413. "guard-n-primary-guards",
  414. DFLT_N_PRIMARY_GUARDS, 1, INT32_MAX);
  415. }
  416. /**
  417. * Return the number of the live primary guards we should look at when
  418. * making a circuit.
  419. */
  420. STATIC int
  421. get_n_primary_guards_to_use(guard_usage_t usage)
  422. {
  423. int configured;
  424. const char *param_name;
  425. int param_default;
  426. if (usage == GUARD_USAGE_DIRGUARD) {
  427. configured = get_options()->NumDirectoryGuards;
  428. param_name = "guard-n-primary-dir-guards-to-use";
  429. param_default = DFLT_N_PRIMARY_DIR_GUARDS_TO_USE;
  430. } else {
  431. configured = get_options()->NumEntryGuards;
  432. param_name = "guard-n-primary-guards-to-use";
  433. param_default = DFLT_N_PRIMARY_GUARDS_TO_USE;
  434. }
  435. if (configured >= 1) {
  436. return configured;
  437. }
  438. return networkstatus_get_param(NULL,
  439. param_name, param_default, 1, INT32_MAX);
  440. }
  441. /**
  442. * If we haven't successfully built or used a circuit in this long, then
  443. * consider that the internet is probably down.
  444. */
  445. STATIC int
  446. get_internet_likely_down_interval(void)
  447. {
  448. return networkstatus_get_param(NULL, "guard-internet-likely-down-interval",
  449. DFLT_INTERNET_LIKELY_DOWN_INTERVAL,
  450. 1, INT32_MAX);
  451. }
  452. /**
  453. * If we're trying to connect to a nonprimary guard for at least this
  454. * many seconds, and we haven't gotten the connection to work, we will treat
  455. * lower-priority guards as usable.
  456. */
  457. STATIC int
  458. get_nonprimary_guard_connect_timeout(void)
  459. {
  460. return networkstatus_get_param(NULL,
  461. "guard-nonprimary-guard-connect-timeout",
  462. DFLT_NONPRIMARY_GUARD_CONNECT_TIMEOUT,
  463. 1, INT32_MAX);
  464. }
  465. /**
  466. * If a circuit has been sitting around in 'waiting for better guard' state
  467. * for at least this long, we'll expire it.
  468. */
  469. STATIC int
  470. get_nonprimary_guard_idle_timeout(void)
  471. {
  472. return networkstatus_get_param(NULL,
  473. "guard-nonprimary-guard-idle-timeout",
  474. DFLT_NONPRIMARY_GUARD_IDLE_TIMEOUT,
  475. 1, INT32_MAX);
  476. }
  477. /**
  478. * If our configuration retains fewer than this fraction of guards from the
  479. * torrc, we are in a restricted setting.
  480. */
  481. STATIC double
  482. get_meaningful_restriction_threshold(void)
  483. {
  484. int32_t pct = networkstatus_get_param(NULL,
  485. "guard-meaningful-restriction-percent",
  486. DFLT_MEANINGFUL_RESTRICTION_PERCENT,
  487. 1, INT32_MAX);
  488. return pct / 100.0;
  489. }
  490. /**
  491. * If our configuration retains fewer than this fraction of guards from the
  492. * torrc, we are in an extremely restricted setting, and should warn.
  493. */
  494. STATIC double
  495. get_extreme_restriction_threshold(void)
  496. {
  497. int32_t pct = networkstatus_get_param(NULL,
  498. "guard-extreme-restriction-percent",
  499. DFLT_EXTREME_RESTRICTION_PERCENT,
  500. 1, INT32_MAX);
  501. return pct / 100.0;
  502. }
  503. /* Mark <b>guard</b> as maybe reachable again. */
  504. static void
  505. mark_guard_maybe_reachable(entry_guard_t *guard)
  506. {
  507. if (guard->is_reachable != GUARD_REACHABLE_NO) {
  508. return;
  509. }
  510. /* Note that we do not clear failing_since: this guard is now only
  511. * _maybe-reachable_. */
  512. guard->is_reachable = GUARD_REACHABLE_MAYBE;
  513. if (guard->is_filtered_guard)
  514. guard->is_usable_filtered_guard = 1;
  515. }
  516. /**
  517. * Called when the network comes up after having seemed to be down for
  518. * a while: Mark the primary guards as maybe-reachable so that we'll
  519. * try them again.
  520. */
  521. STATIC void
  522. mark_primary_guards_maybe_reachable(guard_selection_t *gs)
  523. {
  524. tor_assert(gs);
  525. if (!gs->primary_guards_up_to_date)
  526. entry_guards_update_primary(gs);
  527. SMARTLIST_FOREACH_BEGIN(gs->primary_entry_guards, entry_guard_t *, guard) {
  528. mark_guard_maybe_reachable(guard);
  529. } SMARTLIST_FOREACH_END(guard);
  530. }
  531. /* Called when we exhaust all guards in our sampled set: Marks all guards as
  532. maybe-reachable so that we 'll try them again. */
  533. static void
  534. mark_all_guards_maybe_reachable(guard_selection_t *gs)
  535. {
  536. tor_assert(gs);
  537. SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
  538. mark_guard_maybe_reachable(guard);
  539. } SMARTLIST_FOREACH_END(guard);
  540. }
  541. /**@}*/
  542. /**
  543. * Given our options and our list of nodes, return the name of the
  544. * guard selection that we should use. Return NULL for "use the
  545. * same selection you were using before.
  546. */
  547. STATIC const char *
  548. choose_guard_selection(const or_options_t *options,
  549. const networkstatus_t *live_ns,
  550. const guard_selection_t *old_selection,
  551. guard_selection_type_t *type_out)
  552. {
  553. tor_assert(options);
  554. tor_assert(type_out);
  555. if (options->UseBridges) {
  556. *type_out = GS_TYPE_BRIDGE;
  557. return "bridges";
  558. }
  559. if (! live_ns) {
  560. /* without a networkstatus, we can't tell any more than that. */
  561. *type_out = GS_TYPE_NORMAL;
  562. return "default";
  563. }
  564. const smartlist_t *nodes = nodelist_get_list();
  565. int n_guards = 0, n_passing_filter = 0;
  566. SMARTLIST_FOREACH_BEGIN(nodes, const node_t *, node) {
  567. if (node_is_possible_guard(node)) {
  568. ++n_guards;
  569. if (node_passes_guard_filter(options, node)) {
  570. ++n_passing_filter;
  571. }
  572. }
  573. } SMARTLIST_FOREACH_END(node);
  574. /* We use separate 'high' and 'low' thresholds here to prevent flapping
  575. * back and forth */
  576. const int meaningful_threshold_high =
  577. (int)(n_guards * get_meaningful_restriction_threshold() * 1.05);
  578. const int meaningful_threshold_mid =
  579. (int)(n_guards * get_meaningful_restriction_threshold());
  580. const int meaningful_threshold_low =
  581. (int)(n_guards * get_meaningful_restriction_threshold() * .95);
  582. const int extreme_threshold =
  583. (int)(n_guards * get_extreme_restriction_threshold());
  584. /*
  585. If we have no previous selection, then we're "restricted" iff we are
  586. below the meaningful restriction threshold. That's easy enough.
  587. But if we _do_ have a previous selection, we make it a little
  588. "sticky": we only move from "restricted" to "default" when we find
  589. that we're above the threshold plus 5%, and we only move from
  590. "default" to "restricted" when we're below the threshold minus 5%.
  591. That should prevent us from flapping back and forth if we happen to
  592. be hovering very close to the default.
  593. The extreme threshold is for warning only.
  594. */
  595. static int have_warned_extreme_threshold = 0;
  596. if (n_guards &&
  597. n_passing_filter < extreme_threshold &&
  598. ! have_warned_extreme_threshold) {
  599. have_warned_extreme_threshold = 1;
  600. const double exclude_frac =
  601. (n_guards - n_passing_filter) / (double)n_guards;
  602. log_warn(LD_GUARD, "Your configuration excludes %d%% of all possible "
  603. "guards. That's likely to make you stand out from the "
  604. "rest of the world.", (int)(exclude_frac * 100));
  605. }
  606. /* Easy case: no previous selection. Just check if we are in restricted or
  607. normal guard selection. */
  608. if (old_selection == NULL) {
  609. if (n_passing_filter >= meaningful_threshold_mid) {
  610. *type_out = GS_TYPE_NORMAL;
  611. return "default";
  612. } else {
  613. *type_out = GS_TYPE_RESTRICTED;
  614. return "restricted";
  615. }
  616. }
  617. /* Trickier case: we do have a previous guard selection context. */
  618. tor_assert(old_selection);
  619. /* Use high and low thresholds to decide guard selection, and if we fall in
  620. the middle then keep the current guard selection context. */
  621. if (n_passing_filter >= meaningful_threshold_high) {
  622. *type_out = GS_TYPE_NORMAL;
  623. return "default";
  624. } else if (n_passing_filter < meaningful_threshold_low) {
  625. *type_out = GS_TYPE_RESTRICTED;
  626. return "restricted";
  627. } else {
  628. /* we are in the middle: maintain previous guard selection */
  629. *type_out = old_selection->type;
  630. return old_selection->name;
  631. }
  632. }
  633. /**
  634. * Check whether we should switch from our current guard selection to a
  635. * different one. If so, switch and return 1. Return 0 otherwise.
  636. *
  637. * On a 1 return, the caller should mark all currently live circuits unusable
  638. * for new streams, by calling circuit_mark_all_unused_circs() and
  639. * circuit_mark_all_dirty_circs_as_unusable().
  640. */
  641. int
  642. update_guard_selection_choice(const or_options_t *options)
  643. {
  644. if (!curr_guard_context) {
  645. create_initial_guard_context();
  646. return 1;
  647. }
  648. guard_selection_type_t type = GS_TYPE_INFER;
  649. const char *new_name = choose_guard_selection(
  650. options,
  651. networkstatus_get_live_consensus(approx_time()),
  652. curr_guard_context,
  653. &type);
  654. tor_assert(new_name);
  655. tor_assert(type != GS_TYPE_INFER);
  656. const char *cur_name = curr_guard_context->name;
  657. if (! strcmp(cur_name, new_name)) {
  658. log_debug(LD_GUARD,
  659. "Staying with guard context \"%s\" (no change)", new_name);
  660. return 0; // No change
  661. }
  662. log_notice(LD_GUARD, "Switching to guard context \"%s\" (was using \"%s\")",
  663. new_name, cur_name);
  664. guard_selection_t *new_guard_context;
  665. new_guard_context = get_guard_selection_by_name(new_name, type, 1);
  666. tor_assert(new_guard_context);
  667. tor_assert(new_guard_context != curr_guard_context);
  668. curr_guard_context = new_guard_context;
  669. return 1;
  670. }
  671. /**
  672. * Return true iff <b>node</b> has all the flags needed for us to consider it
  673. * a possible guard when sampling guards.
  674. */
  675. static int
  676. node_is_possible_guard(const node_t *node)
  677. {
  678. /* The "GUARDS" set is all nodes in the nodelist for which this predicate
  679. * holds. */
  680. tor_assert(node);
  681. return (node->is_possible_guard &&
  682. node->is_stable &&
  683. node->is_fast &&
  684. node->is_valid &&
  685. node_is_dir(node) &&
  686. !router_digest_is_me(node->identity));
  687. }
  688. /**
  689. * Return the sampled guard with the RSA identity digest <b>rsa_id</b>, or
  690. * NULL if we don't have one. */
  691. STATIC entry_guard_t *
  692. get_sampled_guard_with_id(guard_selection_t *gs,
  693. const uint8_t *rsa_id)
  694. {
  695. tor_assert(gs);
  696. tor_assert(rsa_id);
  697. SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
  698. if (tor_memeq(guard->identity, rsa_id, DIGEST_LEN))
  699. return guard;
  700. } SMARTLIST_FOREACH_END(guard);
  701. return NULL;
  702. }
  703. /** If <b>gs</b> contains a sampled entry guard matching <b>bridge</b>,
  704. * return that guard. Otherwise return NULL. */
  705. static entry_guard_t *
  706. get_sampled_guard_for_bridge(guard_selection_t *gs,
  707. const bridge_info_t *bridge)
  708. {
  709. const uint8_t *id = bridge_get_rsa_id_digest(bridge);
  710. const tor_addr_port_t *addrport = bridge_get_addr_port(bridge);
  711. entry_guard_t *guard;
  712. if (BUG(!addrport))
  713. return NULL; // LCOV_EXCL_LINE
  714. guard = get_sampled_guard_by_bridge_addr(gs, addrport);
  715. if (! guard || (id && tor_memneq(id, guard->identity, DIGEST_LEN)))
  716. return NULL;
  717. else
  718. return guard;
  719. }
  720. /** If we know a bridge_info_t matching <b>guard</b>, return that
  721. * bridge. Otherwise return NULL. */
  722. static bridge_info_t *
  723. get_bridge_info_for_guard(const entry_guard_t *guard)
  724. {
  725. const uint8_t *identity = NULL;
  726. if (! tor_digest_is_zero(guard->identity)) {
  727. identity = (const uint8_t *)guard->identity;
  728. }
  729. if (BUG(guard->bridge_addr == NULL))
  730. return NULL;
  731. return get_configured_bridge_by_exact_addr_port_digest(
  732. &guard->bridge_addr->addr,
  733. guard->bridge_addr->port,
  734. (const char*)identity);
  735. }
  736. /**
  737. * Return true iff we have a sampled guard with the RSA identity digest
  738. * <b>rsa_id</b>. */
  739. static inline int
  740. have_sampled_guard_with_id(guard_selection_t *gs, const uint8_t *rsa_id)
  741. {
  742. return get_sampled_guard_with_id(gs, rsa_id) != NULL;
  743. }
  744. /**
  745. * Allocate a new entry_guard_t object for <b>node</b>, add it to the
  746. * sampled entry guards in <b>gs</b>, and return it. <b>node</b> must
  747. * not currently be a sampled guard in <b>gs</b>.
  748. */
  749. STATIC entry_guard_t *
  750. entry_guard_add_to_sample(guard_selection_t *gs,
  751. const node_t *node)
  752. {
  753. log_info(LD_GUARD, "Adding %s as to the entry guard sample set.",
  754. node_describe(node));
  755. /* make sure that the guard is not already sampled. */
  756. if (BUG(have_sampled_guard_with_id(gs, (const uint8_t*)node->identity)))
  757. return NULL; // LCOV_EXCL_LINE
  758. return entry_guard_add_to_sample_impl(gs,
  759. (const uint8_t*)node->identity,
  760. node_get_nickname(node),
  761. NULL);
  762. }
  763. /**
  764. * Backend: adds a new sampled guard to <b>gs</b>, with given identity,
  765. * nickname, and ORPort. rsa_id_digest and bridge_addrport are optional, but
  766. * we need one of them. nickname is optional. The caller is responsible for
  767. * maintaining the size limit of the SAMPLED_GUARDS set.
  768. */
  769. static entry_guard_t *
  770. entry_guard_add_to_sample_impl(guard_selection_t *gs,
  771. const uint8_t *rsa_id_digest,
  772. const char *nickname,
  773. const tor_addr_port_t *bridge_addrport)
  774. {
  775. const int GUARD_LIFETIME = get_guard_lifetime();
  776. tor_assert(gs);
  777. // XXXX #20827 take ed25519 identity here too.
  778. /* Make sure we can actually identify the guard. */
  779. if (BUG(!rsa_id_digest && !bridge_addrport))
  780. return NULL; // LCOV_EXCL_LINE
  781. entry_guard_t *guard = tor_malloc_zero(sizeof(entry_guard_t));
  782. /* persistent fields */
  783. guard->is_persistent = (rsa_id_digest != NULL);
  784. guard->selection_name = tor_strdup(gs->name);
  785. if (rsa_id_digest)
  786. memcpy(guard->identity, rsa_id_digest, DIGEST_LEN);
  787. if (nickname)
  788. strlcpy(guard->nickname, nickname, sizeof(guard->nickname));
  789. guard->sampled_on_date = randomize_time(approx_time(), GUARD_LIFETIME/10);
  790. tor_free(guard->sampled_by_version);
  791. guard->sampled_by_version = tor_strdup(VERSION);
  792. guard->currently_listed = 1;
  793. guard->confirmed_idx = -1;
  794. /* non-persistent fields */
  795. guard->is_reachable = GUARD_REACHABLE_MAYBE;
  796. if (bridge_addrport)
  797. guard->bridge_addr = tor_memdup(bridge_addrport, sizeof(*bridge_addrport));
  798. smartlist_add(gs->sampled_entry_guards, guard);
  799. guard->in_selection = gs;
  800. entry_guard_set_filtered_flags(get_options(), gs, guard);
  801. entry_guards_changed_for_guard_selection(gs);
  802. return guard;
  803. }
  804. /**
  805. * Add an entry guard to the "bridges" guard selection sample, with
  806. * information taken from <b>bridge</b>. Return that entry guard.
  807. */
  808. static entry_guard_t *
  809. entry_guard_add_bridge_to_sample(guard_selection_t *gs,
  810. const bridge_info_t *bridge)
  811. {
  812. const uint8_t *id_digest = bridge_get_rsa_id_digest(bridge);
  813. const tor_addr_port_t *addrport = bridge_get_addr_port(bridge);
  814. tor_assert(addrport);
  815. /* make sure that the guard is not already sampled. */
  816. if (BUG(get_sampled_guard_for_bridge(gs, bridge)))
  817. return NULL; // LCOV_EXCL_LINE
  818. return entry_guard_add_to_sample_impl(gs, id_digest, NULL, addrport);
  819. }
  820. /**
  821. * Return the entry_guard_t in <b>gs</b> whose address is <b>addrport</b>,
  822. * or NULL if none exists.
  823. */
  824. static entry_guard_t *
  825. get_sampled_guard_by_bridge_addr(guard_selection_t *gs,
  826. const tor_addr_port_t *addrport)
  827. {
  828. if (! gs)
  829. return NULL;
  830. if (BUG(!addrport))
  831. return NULL;
  832. SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, g) {
  833. if (g->bridge_addr && tor_addr_port_eq(addrport, g->bridge_addr))
  834. return g;
  835. } SMARTLIST_FOREACH_END(g);
  836. return NULL;
  837. }
  838. /** Update the guard subsystem's knowledge of the identity of the bridge
  839. * at <b>addrport</b>. Idempotent.
  840. */
  841. void
  842. entry_guard_learned_bridge_identity(const tor_addr_port_t *addrport,
  843. const uint8_t *rsa_id_digest)
  844. {
  845. guard_selection_t *gs = get_guard_selection_by_name("bridges",
  846. GS_TYPE_BRIDGE,
  847. 0);
  848. if (!gs)
  849. return;
  850. entry_guard_t *g = get_sampled_guard_by_bridge_addr(gs, addrport);
  851. if (!g)
  852. return;
  853. int make_persistent = 0;
  854. if (tor_digest_is_zero(g->identity)) {
  855. memcpy(g->identity, rsa_id_digest, DIGEST_LEN);
  856. make_persistent = 1;
  857. } else if (tor_memeq(g->identity, rsa_id_digest, DIGEST_LEN)) {
  858. /* Nothing to see here; we learned something we already knew. */
  859. if (BUG(! g->is_persistent))
  860. make_persistent = 1;
  861. } else {
  862. char old_id[HEX_DIGEST_LEN+1];
  863. base16_encode(old_id, sizeof(old_id), g->identity, sizeof(g->identity));
  864. log_warn(LD_BUG, "We 'learned' an identity %s for a bridge at %s:%d, but "
  865. "we already knew a different one (%s). Ignoring the new info as "
  866. "possibly bogus.",
  867. hex_str((const char *)rsa_id_digest, DIGEST_LEN),
  868. fmt_and_decorate_addr(&addrport->addr), addrport->port,
  869. old_id);
  870. return; // redundant, but let's be clear: we're not making this persistent.
  871. }
  872. if (make_persistent) {
  873. g->is_persistent = 1;
  874. entry_guards_changed_for_guard_selection(gs);
  875. }
  876. }
  877. /**
  878. * Return the number of sampled guards in <b>gs</b> that are "filtered"
  879. * (that is, we're willing to connect to them) and that are "usable"
  880. * (that is, either "reachable" or "maybe reachable").
  881. *
  882. * If a restriction is provided in <b>rst</b>, do not count any guards that
  883. * violate it.
  884. */
  885. STATIC int
  886. num_reachable_filtered_guards(const guard_selection_t *gs,
  887. const entry_guard_restriction_t *rst)
  888. {
  889. int n_reachable_filtered_guards = 0;
  890. SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
  891. entry_guard_consider_retry(guard);
  892. if (! entry_guard_obeys_restriction(guard, rst))
  893. continue;
  894. if (guard->is_usable_filtered_guard)
  895. ++n_reachable_filtered_guards;
  896. } SMARTLIST_FOREACH_END(guard);
  897. return n_reachable_filtered_guards;
  898. }
  899. /** Return the actual maximum size for the sample in <b>gs</b>,
  900. * given that we know about <b>n_guards</b> total. */
  901. static int
  902. get_max_sample_size(guard_selection_t *gs,
  903. int n_guards)
  904. {
  905. const int using_bridges = (gs->type == GS_TYPE_BRIDGE);
  906. const int min_sample = get_min_filtered_sample_size();
  907. /* If we are in bridge mode, expand our sample set as needed without worrying
  908. * about max size. We should respect the user's wishes to use many bridges if
  909. * that's what they have specified in their configuration file. */
  910. if (using_bridges)
  911. return INT_MAX;
  912. const int max_sample_by_pct = (int)(n_guards * get_max_sample_threshold());
  913. const int max_sample_absolute = get_max_sample_size_absolute();
  914. const int max_sample = MIN(max_sample_by_pct, max_sample_absolute);
  915. if (max_sample < min_sample)
  916. return min_sample;
  917. else
  918. return max_sample;
  919. }
  920. /**
  921. * Return a smartlist of the all the guards that are not currently
  922. * members of the sample (GUARDS - SAMPLED_GUARDS). The elements of
  923. * this list are node_t pointers in the non-bridge case, and
  924. * bridge_info_t pointers in the bridge case. Set *<b>n_guards_out/b>
  925. * to the number of guards that we found in GUARDS, including those
  926. * that were already sampled.
  927. */
  928. static smartlist_t *
  929. get_eligible_guards(const or_options_t *options,
  930. guard_selection_t *gs,
  931. int *n_guards_out)
  932. {
  933. /* Construct eligible_guards as GUARDS - SAMPLED_GUARDS */
  934. smartlist_t *eligible_guards = smartlist_new();
  935. int n_guards = 0; // total size of "GUARDS"
  936. if (gs->type == GS_TYPE_BRIDGE) {
  937. const smartlist_t *bridges = bridge_list_get();
  938. SMARTLIST_FOREACH_BEGIN(bridges, bridge_info_t *, bridge) {
  939. ++n_guards;
  940. if (NULL != get_sampled_guard_for_bridge(gs, bridge)) {
  941. continue;
  942. }
  943. smartlist_add(eligible_guards, bridge);
  944. } SMARTLIST_FOREACH_END(bridge);
  945. } else {
  946. const smartlist_t *nodes = nodelist_get_list();
  947. const int n_sampled = smartlist_len(gs->sampled_entry_guards);
  948. /* Build a bloom filter of our current guards: let's keep this O(N). */
  949. digestset_t *sampled_guard_ids = digestset_new(n_sampled);
  950. SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, const entry_guard_t *,
  951. guard) {
  952. digestset_add(sampled_guard_ids, guard->identity);
  953. } SMARTLIST_FOREACH_END(guard);
  954. SMARTLIST_FOREACH_BEGIN(nodes, const node_t *, node) {
  955. if (! node_is_possible_guard(node))
  956. continue;
  957. if (gs->type == GS_TYPE_RESTRICTED) {
  958. /* In restricted mode, we apply the filter BEFORE sampling, so
  959. * that we are sampling from the nodes that we might actually
  960. * select. If we sampled first, we might wind up with a sample
  961. * that didn't include any EntryNodes at all. */
  962. if (! node_passes_guard_filter(options, node))
  963. continue;
  964. }
  965. ++n_guards;
  966. if (digestset_contains(sampled_guard_ids, node->identity))
  967. continue;
  968. smartlist_add(eligible_guards, (node_t*)node);
  969. } SMARTLIST_FOREACH_END(node);
  970. /* Now we can free that bloom filter. */
  971. digestset_free(sampled_guard_ids);
  972. }
  973. *n_guards_out = n_guards;
  974. return eligible_guards;
  975. }
  976. /** Helper: given a smartlist of either bridge_info_t (if gs->type is
  977. * GS_TYPE_BRIDGE) or node_t (otherwise), pick one that can be a guard,
  978. * add it as a guard, remove it from the list, and return a new
  979. * entry_guard_t. Return NULL on failure. */
  980. static entry_guard_t *
  981. select_and_add_guard_item_for_sample(guard_selection_t *gs,
  982. smartlist_t *eligible_guards)
  983. {
  984. entry_guard_t *added_guard;
  985. if (gs->type == GS_TYPE_BRIDGE) {
  986. const bridge_info_t *bridge = smartlist_choose(eligible_guards);
  987. if (BUG(!bridge))
  988. return NULL; // LCOV_EXCL_LINE
  989. smartlist_remove(eligible_guards, bridge);
  990. added_guard = entry_guard_add_bridge_to_sample(gs, bridge);
  991. } else {
  992. const node_t *node =
  993. node_sl_choose_by_bandwidth(eligible_guards, WEIGHT_FOR_GUARD);
  994. if (BUG(!node))
  995. return NULL; // LCOV_EXCL_LINE
  996. smartlist_remove(eligible_guards, node);
  997. added_guard = entry_guard_add_to_sample(gs, node);
  998. }
  999. return added_guard;
  1000. }
  1001. /** Return true iff we need a consensus to maintain our */
  1002. static int
  1003. live_consensus_is_missing(const guard_selection_t *gs)
  1004. {
  1005. tor_assert(gs);
  1006. if (gs->type == GS_TYPE_BRIDGE) {
  1007. /* We don't update bridges from the consensus; they aren't there. */
  1008. return 0;
  1009. }
  1010. return networkstatus_get_live_consensus(approx_time()) == NULL;
  1011. }
  1012. /**
  1013. * Add new guards to the sampled guards in <b>gs</b> until there are
  1014. * enough usable filtered guards, but never grow the sample beyond its
  1015. * maximum size. Return the last guard added, or NULL if none were
  1016. * added.
  1017. */
  1018. STATIC entry_guard_t *
  1019. entry_guards_expand_sample(guard_selection_t *gs)
  1020. {
  1021. tor_assert(gs);
  1022. const or_options_t *options = get_options();
  1023. if (live_consensus_is_missing(gs)) {
  1024. log_info(LD_GUARD, "Not expanding the sample guard set; we have "
  1025. "no live consensus.");
  1026. return NULL;
  1027. }
  1028. int n_sampled = smartlist_len(gs->sampled_entry_guards);
  1029. entry_guard_t *added_guard = NULL;
  1030. int n_usable_filtered_guards = num_reachable_filtered_guards(gs, NULL);
  1031. int n_guards = 0;
  1032. smartlist_t *eligible_guards = get_eligible_guards(options, gs, &n_guards);
  1033. const int max_sample = get_max_sample_size(gs, n_guards);
  1034. const int min_filtered_sample = get_min_filtered_sample_size();
  1035. log_info(LD_GUARD, "Expanding the sample guard set. We have %d guards "
  1036. "in the sample, and %d eligible guards to extend it with.",
  1037. n_sampled, smartlist_len(eligible_guards));
  1038. while (n_usable_filtered_guards < min_filtered_sample) {
  1039. /* Has our sample grown too large to expand? */
  1040. if (n_sampled >= max_sample) {
  1041. log_info(LD_GUARD, "Not expanding the guard sample any further; "
  1042. "just hit the maximum sample threshold of %d",
  1043. max_sample);
  1044. goto done;
  1045. }
  1046. /* Did we run out of guards? */
  1047. if (smartlist_len(eligible_guards) == 0) {
  1048. /* LCOV_EXCL_START
  1049. As long as MAX_SAMPLE_THRESHOLD makes can't be adjusted to
  1050. allow all guards to be sampled, this can't be reached.
  1051. */
  1052. log_info(LD_GUARD, "Not expanding the guard sample any further; "
  1053. "just ran out of eligible guards");
  1054. goto done;
  1055. /* LCOV_EXCL_STOP */
  1056. }
  1057. /* Otherwise we can add at least one new guard. */
  1058. added_guard = select_and_add_guard_item_for_sample(gs, eligible_guards);
  1059. if (!added_guard)
  1060. goto done; // LCOV_EXCL_LINE -- only fails on BUG.
  1061. ++n_sampled;
  1062. if (added_guard->is_usable_filtered_guard)
  1063. ++n_usable_filtered_guards;
  1064. }
  1065. done:
  1066. smartlist_free(eligible_guards);
  1067. return added_guard;
  1068. }
  1069. /**
  1070. * Helper: <b>guard</b> has just been removed from the sampled guards:
  1071. * also remove it from primary and confirmed. */
  1072. static void
  1073. remove_guard_from_confirmed_and_primary_lists(guard_selection_t *gs,
  1074. entry_guard_t *guard)
  1075. {
  1076. if (guard->is_primary) {
  1077. guard->is_primary = 0;
  1078. smartlist_remove_keeporder(gs->primary_entry_guards, guard);
  1079. } else {
  1080. if (BUG(smartlist_contains(gs->primary_entry_guards, guard))) {
  1081. smartlist_remove_keeporder(gs->primary_entry_guards, guard);
  1082. }
  1083. }
  1084. if (guard->confirmed_idx >= 0) {
  1085. smartlist_remove_keeporder(gs->confirmed_entry_guards, guard);
  1086. guard->confirmed_idx = -1;
  1087. guard->confirmed_on_date = 0;
  1088. } else {
  1089. if (BUG(smartlist_contains(gs->confirmed_entry_guards, guard))) {
  1090. // LCOV_EXCL_START
  1091. smartlist_remove_keeporder(gs->confirmed_entry_guards, guard);
  1092. // LCOV_EXCL_STOP
  1093. }
  1094. }
  1095. }
  1096. /** Return true iff <b>guard</b> is currently "listed" -- that is, it
  1097. * appears in the consensus, or as a configured bridge (as
  1098. * appropriate) */
  1099. MOCK_IMPL(STATIC int,
  1100. entry_guard_is_listed,(guard_selection_t *gs, const entry_guard_t *guard))
  1101. {
  1102. if (gs->type == GS_TYPE_BRIDGE) {
  1103. return NULL != get_bridge_info_for_guard(guard);
  1104. } else {
  1105. const node_t *node = node_get_by_id(guard->identity);
  1106. return node && node_is_possible_guard(node);
  1107. }
  1108. }
  1109. /**
  1110. * Update the status of all sampled guards based on the arrival of a
  1111. * new consensus networkstatus document. This will include marking
  1112. * some guards as listed or unlisted, and removing expired guards. */
  1113. STATIC void
  1114. sampled_guards_update_from_consensus(guard_selection_t *gs)
  1115. {
  1116. tor_assert(gs);
  1117. const int REMOVE_UNLISTED_GUARDS_AFTER =
  1118. (get_remove_unlisted_guards_after_days() * 86400);
  1119. const int unlisted_since_slop = REMOVE_UNLISTED_GUARDS_AFTER / 5;
  1120. // It's important to use only a live consensus here; we don't want to
  1121. // make changes based on anything expired or old.
  1122. if (live_consensus_is_missing(gs)) {
  1123. log_info(LD_GUARD, "Not updating the sample guard set; we have "
  1124. "no live consensus.");
  1125. return;
  1126. }
  1127. log_info(LD_GUARD, "Updating sampled guard status based on received "
  1128. "consensus.");
  1129. int n_changes = 0;
  1130. /* First: Update listed/unlisted. */
  1131. SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
  1132. /* XXXX #20827 check ed ID too */
  1133. const int is_listed = entry_guard_is_listed(gs, guard);
  1134. if (is_listed && ! guard->currently_listed) {
  1135. ++n_changes;
  1136. guard->currently_listed = 1;
  1137. guard->unlisted_since_date = 0;
  1138. log_info(LD_GUARD, "Sampled guard %s is now listed again.",
  1139. entry_guard_describe(guard));
  1140. } else if (!is_listed && guard->currently_listed) {
  1141. ++n_changes;
  1142. guard->currently_listed = 0;
  1143. guard->unlisted_since_date = randomize_time(approx_time(),
  1144. unlisted_since_slop);
  1145. log_info(LD_GUARD, "Sampled guard %s is now unlisted.",
  1146. entry_guard_describe(guard));
  1147. } else if (is_listed && guard->currently_listed) {
  1148. log_debug(LD_GUARD, "Sampled guard %s is still listed.",
  1149. entry_guard_describe(guard));
  1150. } else {
  1151. tor_assert(! is_listed && ! guard->currently_listed);
  1152. log_debug(LD_GUARD, "Sampled guard %s is still unlisted.",
  1153. entry_guard_describe(guard));
  1154. }
  1155. /* Clean up unlisted_since_date, just in case. */
  1156. if (guard->currently_listed && guard->unlisted_since_date) {
  1157. ++n_changes;
  1158. guard->unlisted_since_date = 0;
  1159. log_warn(LD_BUG, "Sampled guard %s was listed, but with "
  1160. "unlisted_since_date set. Fixing.",
  1161. entry_guard_describe(guard));
  1162. } else if (!guard->currently_listed && ! guard->unlisted_since_date) {
  1163. ++n_changes;
  1164. guard->unlisted_since_date = randomize_time(approx_time(),
  1165. unlisted_since_slop);
  1166. log_warn(LD_BUG, "Sampled guard %s was unlisted, but with "
  1167. "unlisted_since_date unset. Fixing.",
  1168. entry_guard_describe(guard));
  1169. }
  1170. } SMARTLIST_FOREACH_END(guard);
  1171. const time_t remove_if_unlisted_since =
  1172. approx_time() - REMOVE_UNLISTED_GUARDS_AFTER;
  1173. const time_t maybe_remove_if_sampled_before =
  1174. approx_time() - get_guard_lifetime();
  1175. const time_t remove_if_confirmed_before =
  1176. approx_time() - get_guard_confirmed_min_lifetime();
  1177. /* Then: remove the ones that have been junk for too long */
  1178. SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
  1179. int rmv = 0;
  1180. if (guard->currently_listed == 0 &&
  1181. guard->unlisted_since_date < remove_if_unlisted_since) {
  1182. /*
  1183. "We have a live consensus, and {IS_LISTED} is false, and
  1184. {FIRST_UNLISTED_AT} is over {REMOVE_UNLISTED_GUARDS_AFTER}
  1185. days in the past."
  1186. */
  1187. log_info(LD_GUARD, "Removing sampled guard %s: it has been unlisted "
  1188. "for over %d days", entry_guard_describe(guard),
  1189. get_remove_unlisted_guards_after_days());
  1190. rmv = 1;
  1191. } else if (guard->sampled_on_date < maybe_remove_if_sampled_before) {
  1192. /* We have a live consensus, and {ADDED_ON_DATE} is over
  1193. {GUARD_LIFETIME} ago, *and* {CONFIRMED_ON_DATE} is either
  1194. "never", or over {GUARD_CONFIRMED_MIN_LIFETIME} ago.
  1195. */
  1196. if (guard->confirmed_on_date == 0) {
  1197. rmv = 1;
  1198. log_info(LD_GUARD, "Removing sampled guard %s: it was sampled "
  1199. "over %d days ago, but never confirmed.",
  1200. entry_guard_describe(guard),
  1201. get_guard_lifetime() / 86400);
  1202. } else if (guard->confirmed_on_date < remove_if_confirmed_before) {
  1203. rmv = 1;
  1204. log_info(LD_GUARD, "Removing sampled guard %s: it was sampled "
  1205. "over %d days ago, and confirmed over %d days ago.",
  1206. entry_guard_describe(guard),
  1207. get_guard_lifetime() / 86400,
  1208. get_guard_confirmed_min_lifetime() / 86400);
  1209. }
  1210. }
  1211. if (rmv) {
  1212. ++n_changes;
  1213. SMARTLIST_DEL_CURRENT(gs->sampled_entry_guards, guard);
  1214. remove_guard_from_confirmed_and_primary_lists(gs, guard);
  1215. entry_guard_free(guard);
  1216. }
  1217. } SMARTLIST_FOREACH_END(guard);
  1218. if (n_changes) {
  1219. gs->primary_guards_up_to_date = 0;
  1220. entry_guards_update_filtered_sets(gs);
  1221. /* We don't need to rebuild the confirmed list right here -- we may have
  1222. * removed confirmed guards above, but we can't have added any new
  1223. * confirmed guards.
  1224. */
  1225. entry_guards_changed_for_guard_selection(gs);
  1226. }
  1227. }
  1228. /**
  1229. * Return true iff <b>node</b> is a Tor relay that we are configured to
  1230. * be able to connect to. */
  1231. static int
  1232. node_passes_guard_filter(const or_options_t *options,
  1233. const node_t *node)
  1234. {
  1235. /* NOTE: Make sure that this function stays in sync with
  1236. * options_transition_affects_entry_guards */
  1237. if (routerset_contains_node(options->ExcludeNodes, node))
  1238. return 0;
  1239. if (options->EntryNodes &&
  1240. !routerset_contains_node(options->EntryNodes, node))
  1241. return 0;
  1242. if (!fascist_firewall_allows_node(node, FIREWALL_OR_CONNECTION, 0))
  1243. return 0;
  1244. if (node_is_a_configured_bridge(node))
  1245. return 0;
  1246. return 1;
  1247. }
  1248. /** Helper: Return true iff <b>bridge</b> passes our configuration
  1249. * filter-- if it is a relay that we are configured to be able to
  1250. * connect to. */
  1251. static int
  1252. bridge_passes_guard_filter(const or_options_t *options,
  1253. const bridge_info_t *bridge)
  1254. {
  1255. tor_assert(bridge);
  1256. if (!bridge)
  1257. return 0;
  1258. if (routerset_contains_bridge(options->ExcludeNodes, bridge))
  1259. return 0;
  1260. /* Ignore entrynodes */
  1261. const tor_addr_port_t *addrport = bridge_get_addr_port(bridge);
  1262. if (!fascist_firewall_allows_address_addr(&addrport->addr,
  1263. addrport->port,
  1264. FIREWALL_OR_CONNECTION,
  1265. 0, 0))
  1266. return 0;
  1267. return 1;
  1268. }
  1269. /**
  1270. * Return true iff <b>guard</b> is a Tor relay that we are configured to
  1271. * be able to connect to, and we haven't disabled it for omission from
  1272. * the consensus or path bias issues. */
  1273. static int
  1274. entry_guard_passes_filter(const or_options_t *options, guard_selection_t *gs,
  1275. entry_guard_t *guard)
  1276. {
  1277. if (guard->currently_listed == 0)
  1278. return 0;
  1279. if (guard->pb.path_bias_disabled)
  1280. return 0;
  1281. if (gs->type == GS_TYPE_BRIDGE) {
  1282. const bridge_info_t *bridge = get_bridge_info_for_guard(guard);
  1283. if (bridge == NULL)
  1284. return 0;
  1285. return bridge_passes_guard_filter(options, bridge);
  1286. } else {
  1287. const node_t *node = node_get_by_id(guard->identity);
  1288. if (node == NULL) {
  1289. // This can happen when currently_listed is true, and we're not updating
  1290. // it because we don't have a live consensus.
  1291. return 0;
  1292. }
  1293. return node_passes_guard_filter(options, node);
  1294. }
  1295. }
  1296. /** Return true iff <b>guard</b> is in the same family as <b>node</b>.
  1297. */
  1298. static int
  1299. guard_in_node_family(const entry_guard_t *guard, const node_t *node)
  1300. {
  1301. const node_t *guard_node = node_get_by_id(guard->identity);
  1302. if (guard_node) {
  1303. return nodes_in_same_family(guard_node, node);
  1304. } else {
  1305. /* If we don't have a node_t for the guard node, we might have
  1306. * a bridge_info_t for it. So let's check to see whether the bridge
  1307. * address matches has any family issues.
  1308. *
  1309. * (Strictly speaking, I believe this check is unnecessary, since we only
  1310. * use it to avoid the exit's family when building circuits, and we don't
  1311. * build multihop circuits until we have a routerinfo_t for the
  1312. * bridge... at which point, we'll also have a node_t for the
  1313. * bridge. Nonetheless, it seems wise to include it, in case our
  1314. * assumptions change down the road. -nickm.)
  1315. */
  1316. if (get_options()->EnforceDistinctSubnets && guard->bridge_addr) {
  1317. tor_addr_t node_addr;
  1318. node_get_addr(node, &node_addr);
  1319. if (addrs_in_same_network_family(&node_addr,
  1320. &guard->bridge_addr->addr)) {
  1321. return 1;
  1322. }
  1323. }
  1324. return 0;
  1325. }
  1326. }
  1327. /* Allocate and return a new exit guard restriction (where <b>exit_id</b> is of
  1328. * size DIGEST_LEN) */
  1329. STATIC entry_guard_restriction_t *
  1330. guard_create_exit_restriction(const uint8_t *exit_id)
  1331. {
  1332. entry_guard_restriction_t *rst = NULL;
  1333. rst = tor_malloc_zero(sizeof(entry_guard_restriction_t));
  1334. rst->type = RST_EXIT_NODE;
  1335. memcpy(rst->exclude_id, exit_id, DIGEST_LEN);
  1336. return rst;
  1337. }
  1338. /** If we have fewer than this many possible usable guards, don't set
  1339. * MD-availability-based restrictions: we might blacklist all of them. */
  1340. #define MIN_GUARDS_FOR_MD_RESTRICTION 10
  1341. /** Return true if we should set md dirserver restrictions. We might not want
  1342. * to set those if our guard options are too restricted, since we don't want
  1343. * to blacklist all of them. */
  1344. static int
  1345. should_set_md_dirserver_restriction(void)
  1346. {
  1347. const guard_selection_t *gs = get_guard_selection_info();
  1348. int num_usable_guards = num_reachable_filtered_guards(gs, NULL);
  1349. /* Don't set restriction if too few reachable filtered guards. */
  1350. if (num_usable_guards < MIN_GUARDS_FOR_MD_RESTRICTION) {
  1351. log_info(LD_GUARD, "Not setting md restriction: only %d"
  1352. " usable guards.", num_usable_guards);
  1353. return 0;
  1354. }
  1355. /* We have enough usable guards: set MD restriction */
  1356. return 1;
  1357. }
  1358. /** Allocate and return an outdated md guard restriction. Return NULL if no
  1359. * such restriction is needed. */
  1360. STATIC entry_guard_restriction_t *
  1361. guard_create_dirserver_md_restriction(void)
  1362. {
  1363. entry_guard_restriction_t *rst = NULL;
  1364. if (!should_set_md_dirserver_restriction()) {
  1365. log_debug(LD_GUARD, "Not setting md restriction: too few "
  1366. "filtered guards.");
  1367. return NULL;
  1368. }
  1369. rst = tor_malloc_zero(sizeof(entry_guard_restriction_t));
  1370. rst->type = RST_OUTDATED_MD_DIRSERVER;
  1371. return rst;
  1372. }
  1373. /* Return True if <b>guard</b> obeys the exit restriction <b>rst</b>. */
  1374. static int
  1375. guard_obeys_exit_restriction(const entry_guard_t *guard,
  1376. const entry_guard_restriction_t *rst)
  1377. {
  1378. tor_assert(rst->type == RST_EXIT_NODE);
  1379. // Exclude the exit ID and all of its family.
  1380. const node_t *node = node_get_by_id((const char*)rst->exclude_id);
  1381. if (node && guard_in_node_family(guard, node))
  1382. return 0;
  1383. return tor_memneq(guard->identity, rst->exclude_id, DIGEST_LEN);
  1384. }
  1385. /** Return True if <b>guard</b> should be used as a dirserver for fetching
  1386. * microdescriptors. */
  1387. static int
  1388. guard_obeys_md_dirserver_restriction(const entry_guard_t *guard)
  1389. {
  1390. /* If this guard is an outdated dirserver, don't use it. */
  1391. if (microdesc_relay_is_outdated_dirserver(guard->identity)) {
  1392. log_info(LD_GENERAL, "Skipping %s dirserver: outdated",
  1393. hex_str(guard->identity, DIGEST_LEN));
  1394. return 0;
  1395. }
  1396. log_debug(LD_GENERAL, "%s dirserver obeys md restrictions",
  1397. hex_str(guard->identity, DIGEST_LEN));
  1398. return 1;
  1399. }
  1400. /**
  1401. * Return true iff <b>guard</b> obeys the restrictions defined in <b>rst</b>.
  1402. * (If <b>rst</b> is NULL, there are no restrictions.)
  1403. */
  1404. static int
  1405. entry_guard_obeys_restriction(const entry_guard_t *guard,
  1406. const entry_guard_restriction_t *rst)
  1407. {
  1408. tor_assert(guard);
  1409. if (! rst)
  1410. return 1; // No restriction? No problem.
  1411. if (rst->type == RST_EXIT_NODE) {
  1412. return guard_obeys_exit_restriction(guard, rst);
  1413. } else if (rst->type == RST_OUTDATED_MD_DIRSERVER) {
  1414. return guard_obeys_md_dirserver_restriction(guard);
  1415. }
  1416. tor_assert_nonfatal_unreached();
  1417. return 0;
  1418. }
  1419. /**
  1420. * Update the <b>is_filtered_guard</b> and <b>is_usable_filtered_guard</b>
  1421. * flags on <b>guard</b>. */
  1422. void
  1423. entry_guard_set_filtered_flags(const or_options_t *options,
  1424. guard_selection_t *gs,
  1425. entry_guard_t *guard)
  1426. {
  1427. unsigned was_filtered = guard->is_filtered_guard;
  1428. guard->is_filtered_guard = 0;
  1429. guard->is_usable_filtered_guard = 0;
  1430. if (entry_guard_passes_filter(options, gs, guard)) {
  1431. guard->is_filtered_guard = 1;
  1432. if (guard->is_reachable != GUARD_REACHABLE_NO)
  1433. guard->is_usable_filtered_guard = 1;
  1434. entry_guard_consider_retry(guard);
  1435. }
  1436. log_debug(LD_GUARD, "Updated sampled guard %s: filtered=%d; "
  1437. "reachable_filtered=%d.", entry_guard_describe(guard),
  1438. guard->is_filtered_guard, guard->is_usable_filtered_guard);
  1439. if (!bool_eq(was_filtered, guard->is_filtered_guard)) {
  1440. /* This guard might now be primary or nonprimary. */
  1441. gs->primary_guards_up_to_date = 0;
  1442. }
  1443. }
  1444. /**
  1445. * Update the <b>is_filtered_guard</b> and <b>is_usable_filtered_guard</b>
  1446. * flag on every guard in <b>gs</b>. */
  1447. STATIC void
  1448. entry_guards_update_filtered_sets(guard_selection_t *gs)
  1449. {
  1450. const or_options_t *options = get_options();
  1451. SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
  1452. entry_guard_set_filtered_flags(options, gs, guard);
  1453. } SMARTLIST_FOREACH_END(guard);
  1454. }
  1455. /**
  1456. * Return a random guard from the reachable filtered sample guards
  1457. * in <b>gs</b>, subject to the exclusion rules listed in <b>flags</b>.
  1458. * Return NULL if no such guard can be found.
  1459. *
  1460. * Make sure that the sample is big enough, and that all the filter flags
  1461. * are set correctly, before calling this function.
  1462. *
  1463. * If a restriction is provided in <b>rst</b>, do not return any guards that
  1464. * violate it.
  1465. **/
  1466. STATIC entry_guard_t *
  1467. sample_reachable_filtered_entry_guards(guard_selection_t *gs,
  1468. const entry_guard_restriction_t *rst,
  1469. unsigned flags)
  1470. {
  1471. tor_assert(gs);
  1472. entry_guard_t *result = NULL;
  1473. const unsigned exclude_confirmed = flags & SAMPLE_EXCLUDE_CONFIRMED;
  1474. const unsigned exclude_primary = flags & SAMPLE_EXCLUDE_PRIMARY;
  1475. const unsigned exclude_pending = flags & SAMPLE_EXCLUDE_PENDING;
  1476. const unsigned no_update_primary = flags & SAMPLE_NO_UPDATE_PRIMARY;
  1477. const unsigned need_descriptor = flags & SAMPLE_EXCLUDE_NO_DESCRIPTOR;
  1478. SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
  1479. entry_guard_consider_retry(guard);
  1480. } SMARTLIST_FOREACH_END(guard);
  1481. const int n_reachable_filtered = num_reachable_filtered_guards(gs, rst);
  1482. log_info(LD_GUARD, "Trying to sample a reachable guard: We know of %d "
  1483. "in the USABLE_FILTERED set.", n_reachable_filtered);
  1484. const int min_filtered_sample = get_min_filtered_sample_size();
  1485. if (n_reachable_filtered < min_filtered_sample) {
  1486. log_info(LD_GUARD, " (That isn't enough. Trying to expand the sample.)");
  1487. entry_guards_expand_sample(gs);
  1488. }
  1489. if (exclude_primary && !gs->primary_guards_up_to_date && !no_update_primary)
  1490. entry_guards_update_primary(gs);
  1491. /* Build the set of reachable filtered guards. */
  1492. smartlist_t *reachable_filtered_sample = smartlist_new();
  1493. SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
  1494. entry_guard_consider_retry(guard);// redundant, but cheap.
  1495. if (! entry_guard_obeys_restriction(guard, rst))
  1496. continue;
  1497. if (! guard->is_usable_filtered_guard)
  1498. continue;
  1499. if (exclude_confirmed && guard->confirmed_idx >= 0)
  1500. continue;
  1501. if (exclude_primary && guard->is_primary)
  1502. continue;
  1503. if (exclude_pending && guard->is_pending)
  1504. continue;
  1505. if (need_descriptor && !guard_has_descriptor(guard))
  1506. continue;
  1507. smartlist_add(reachable_filtered_sample, guard);
  1508. } SMARTLIST_FOREACH_END(guard);
  1509. log_info(LD_GUARD, " (After filters [%x], we have %d guards to consider.)",
  1510. flags, smartlist_len(reachable_filtered_sample));
  1511. if (smartlist_len(reachable_filtered_sample)) {
  1512. result = smartlist_choose(reachable_filtered_sample);
  1513. log_info(LD_GUARD, " (Selected %s.)",
  1514. result ? entry_guard_describe(result) : "<null>");
  1515. }
  1516. smartlist_free(reachable_filtered_sample);
  1517. return result;
  1518. }
  1519. /**
  1520. * Helper: compare two entry_guard_t by their confirmed_idx values.
  1521. * Used to sort the confirmed list.
  1522. */
  1523. static int
  1524. compare_guards_by_confirmed_idx(const void **a_, const void **b_)
  1525. {
  1526. const entry_guard_t *a = *a_, *b = *b_;
  1527. if (a->confirmed_idx < b->confirmed_idx)
  1528. return -1;
  1529. else if (a->confirmed_idx > b->confirmed_idx)
  1530. return 1;
  1531. else
  1532. return 0;
  1533. }
  1534. /**
  1535. * Find the confirmed guards from among the sampled guards in <b>gs</b>,
  1536. * and put them in confirmed_entry_guards in the correct
  1537. * order. Recalculate their indices.
  1538. */
  1539. STATIC void
  1540. entry_guards_update_confirmed(guard_selection_t *gs)
  1541. {
  1542. smartlist_clear(gs->confirmed_entry_guards);
  1543. SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
  1544. if (guard->confirmed_idx >= 0)
  1545. smartlist_add(gs->confirmed_entry_guards, guard);
  1546. } SMARTLIST_FOREACH_END(guard);
  1547. smartlist_sort(gs->confirmed_entry_guards, compare_guards_by_confirmed_idx);
  1548. int any_changed = 0;
  1549. SMARTLIST_FOREACH_BEGIN(gs->confirmed_entry_guards, entry_guard_t *, guard) {
  1550. if (guard->confirmed_idx != guard_sl_idx) {
  1551. any_changed = 1;
  1552. guard->confirmed_idx = guard_sl_idx;
  1553. }
  1554. } SMARTLIST_FOREACH_END(guard);
  1555. gs->next_confirmed_idx = smartlist_len(gs->confirmed_entry_guards);
  1556. if (any_changed) {
  1557. entry_guards_changed_for_guard_selection(gs);
  1558. }
  1559. }
  1560. /**
  1561. * Mark <b>guard</b> as a confirmed guard -- that is, one that we have
  1562. * connected to, and intend to use again.
  1563. */
  1564. STATIC void
  1565. make_guard_confirmed(guard_selection_t *gs, entry_guard_t *guard)
  1566. {
  1567. if (BUG(guard->confirmed_on_date && guard->confirmed_idx >= 0))
  1568. return; // LCOV_EXCL_LINE
  1569. if (BUG(smartlist_contains(gs->confirmed_entry_guards, guard)))
  1570. return; // LCOV_EXCL_LINE
  1571. const int GUARD_LIFETIME = get_guard_lifetime();
  1572. guard->confirmed_on_date = randomize_time(approx_time(), GUARD_LIFETIME/10);
  1573. log_info(LD_GUARD, "Marking %s as a confirmed guard (index %d)",
  1574. entry_guard_describe(guard),
  1575. gs->next_confirmed_idx);
  1576. guard->confirmed_idx = gs->next_confirmed_idx++;
  1577. smartlist_add(gs->confirmed_entry_guards, guard);
  1578. // This confirmed guard might kick something else out of the primary
  1579. // guards.
  1580. gs->primary_guards_up_to_date = 0;
  1581. entry_guards_changed_for_guard_selection(gs);
  1582. }
  1583. /**
  1584. * Recalculate the list of primary guards (the ones we'd prefer to use) from
  1585. * the filtered sample and the confirmed list.
  1586. */
  1587. STATIC void
  1588. entry_guards_update_primary(guard_selection_t *gs)
  1589. {
  1590. tor_assert(gs);
  1591. // prevent recursion. Recursion is potentially very bad here.
  1592. static int running = 0;
  1593. tor_assert(!running);
  1594. running = 1;
  1595. const int N_PRIMARY_GUARDS = get_n_primary_guards();
  1596. smartlist_t *new_primary_guards = smartlist_new();
  1597. smartlist_t *old_primary_guards = smartlist_new();
  1598. smartlist_add_all(old_primary_guards, gs->primary_entry_guards);
  1599. /* Set this flag now, to prevent the calls below from recursing. */
  1600. gs->primary_guards_up_to_date = 1;
  1601. /* First, can we fill it up with confirmed guards? */
  1602. SMARTLIST_FOREACH_BEGIN(gs->confirmed_entry_guards, entry_guard_t *, guard) {
  1603. if (smartlist_len(new_primary_guards) >= N_PRIMARY_GUARDS)
  1604. break;
  1605. if (! guard->is_filtered_guard)
  1606. continue;
  1607. guard->is_primary = 1;
  1608. smartlist_add(new_primary_guards, guard);
  1609. } SMARTLIST_FOREACH_END(guard);
  1610. /* Can we keep any older primary guards? First remove all the ones
  1611. * that we already kept. */
  1612. SMARTLIST_FOREACH_BEGIN(old_primary_guards, entry_guard_t *, guard) {
  1613. if (smartlist_contains(new_primary_guards, guard)) {
  1614. SMARTLIST_DEL_CURRENT_KEEPORDER(old_primary_guards, guard);
  1615. }
  1616. } SMARTLIST_FOREACH_END(guard);
  1617. /* Now add any that are still good. */
  1618. SMARTLIST_FOREACH_BEGIN(old_primary_guards, entry_guard_t *, guard) {
  1619. if (smartlist_len(new_primary_guards) >= N_PRIMARY_GUARDS)
  1620. break;
  1621. if (! guard->is_filtered_guard)
  1622. continue;
  1623. guard->is_primary = 1;
  1624. smartlist_add(new_primary_guards, guard);
  1625. SMARTLIST_DEL_CURRENT_KEEPORDER(old_primary_guards, guard);
  1626. } SMARTLIST_FOREACH_END(guard);
  1627. /* Mark the remaining previous primary guards as non-primary */
  1628. SMARTLIST_FOREACH_BEGIN(old_primary_guards, entry_guard_t *, guard) {
  1629. guard->is_primary = 0;
  1630. } SMARTLIST_FOREACH_END(guard);
  1631. /* Finally, fill out the list with sampled guards. */
  1632. while (smartlist_len(new_primary_guards) < N_PRIMARY_GUARDS) {
  1633. entry_guard_t *guard = sample_reachable_filtered_entry_guards(gs, NULL,
  1634. SAMPLE_EXCLUDE_CONFIRMED|
  1635. SAMPLE_EXCLUDE_PRIMARY|
  1636. SAMPLE_NO_UPDATE_PRIMARY);
  1637. if (!guard)
  1638. break;
  1639. guard->is_primary = 1;
  1640. smartlist_add(new_primary_guards, guard);
  1641. }
  1642. #if 1
  1643. /* Debugging. */
  1644. SMARTLIST_FOREACH(gs->sampled_entry_guards, entry_guard_t *, guard, {
  1645. tor_assert_nonfatal(
  1646. bool_eq(guard->is_primary,
  1647. smartlist_contains(new_primary_guards, guard)));
  1648. });
  1649. #endif
  1650. int any_change = 0;
  1651. if (smartlist_len(gs->primary_entry_guards) !=
  1652. smartlist_len(new_primary_guards)) {
  1653. any_change = 1;
  1654. } else {
  1655. SMARTLIST_FOREACH_BEGIN(gs->primary_entry_guards, entry_guard_t *, g) {
  1656. if (g != smartlist_get(new_primary_guards, g_sl_idx)) {
  1657. any_change = 1;
  1658. }
  1659. } SMARTLIST_FOREACH_END(g);
  1660. }
  1661. if (any_change) {
  1662. log_info(LD_GUARD, "Primary entry guards have changed. "
  1663. "New primary guard list is: ");
  1664. int n = smartlist_len(new_primary_guards);
  1665. SMARTLIST_FOREACH_BEGIN(new_primary_guards, entry_guard_t *, g) {
  1666. log_info(LD_GUARD, " %d/%d: %s%s%s",
  1667. g_sl_idx+1, n, entry_guard_describe(g),
  1668. g->confirmed_idx >= 0 ? " (confirmed)" : "",
  1669. g->is_filtered_guard ? "" : " (excluded by filter)");
  1670. } SMARTLIST_FOREACH_END(g);
  1671. }
  1672. smartlist_free(old_primary_guards);
  1673. smartlist_free(gs->primary_entry_guards);
  1674. gs->primary_entry_guards = new_primary_guards;
  1675. gs->primary_guards_up_to_date = 1;
  1676. running = 0;
  1677. }
  1678. /**
  1679. * Return the number of seconds after the last attempt at which we should
  1680. * retry a guard that has been failing since <b>failing_since</b>.
  1681. */
  1682. static int
  1683. get_retry_schedule(time_t failing_since, time_t now,
  1684. int is_primary)
  1685. {
  1686. const unsigned SIX_HOURS = 6 * 3600;
  1687. const unsigned FOUR_DAYS = 4 * 86400;
  1688. const unsigned SEVEN_DAYS = 7 * 86400;
  1689. time_t tdiff;
  1690. if (now > failing_since) {
  1691. tdiff = now - failing_since;
  1692. } else {
  1693. tdiff = 0;
  1694. }
  1695. const struct {
  1696. time_t maximum; int primary_delay; int nonprimary_delay;
  1697. } delays[] = {
  1698. { SIX_HOURS, 10*60, 1*60*60 },
  1699. { FOUR_DAYS, 90*60, 4*60*60 },
  1700. { SEVEN_DAYS, 4*60*60, 18*60*60 },
  1701. { TIME_MAX, 9*60*60, 36*60*60 }
  1702. };
  1703. unsigned i;
  1704. for (i = 0; i < ARRAY_LENGTH(delays); ++i) {
  1705. if (tdiff <= delays[i].maximum) {
  1706. return is_primary ? delays[i].primary_delay : delays[i].nonprimary_delay;
  1707. }
  1708. }
  1709. /* LCOV_EXCL_START -- can't reach, since delays ends with TIME_MAX. */
  1710. tor_assert_nonfatal_unreached();
  1711. return 36*60*60;
  1712. /* LCOV_EXCL_STOP */
  1713. }
  1714. /**
  1715. * If <b>guard</b> is unreachable, consider whether enough time has passed
  1716. * to consider it maybe-reachable again.
  1717. */
  1718. STATIC void
  1719. entry_guard_consider_retry(entry_guard_t *guard)
  1720. {
  1721. if (guard->is_reachable != GUARD_REACHABLE_NO)
  1722. return; /* No retry needed. */
  1723. const time_t now = approx_time();
  1724. const int delay =
  1725. get_retry_schedule(guard->failing_since, now, guard->is_primary);
  1726. const time_t last_attempt = guard->last_tried_to_connect;
  1727. if (BUG(last_attempt == 0) ||
  1728. now >= last_attempt + delay) {
  1729. /* We should mark this retriable. */
  1730. char tbuf[ISO_TIME_LEN+1];
  1731. format_local_iso_time(tbuf, last_attempt);
  1732. log_info(LD_GUARD, "Marked %s%sguard %s for possible retry, since we "
  1733. "haven't tried to use it since %s.",
  1734. guard->is_primary?"primary ":"",
  1735. guard->confirmed_idx>=0?"confirmed ":"",
  1736. entry_guard_describe(guard),
  1737. tbuf);
  1738. guard->is_reachable = GUARD_REACHABLE_MAYBE;
  1739. if (guard->is_filtered_guard)
  1740. guard->is_usable_filtered_guard = 1;
  1741. }
  1742. }
  1743. /** Tell the entry guards subsystem that we have confirmed that as of
  1744. * just now, we're on the internet. */
  1745. void
  1746. entry_guards_note_internet_connectivity(guard_selection_t *gs)
  1747. {
  1748. gs->last_time_on_internet = approx_time();
  1749. }
  1750. /**
  1751. * Get a guard for use with a circuit. Prefer to pick a running primary
  1752. * guard; then a non-pending running filtered confirmed guard; then a
  1753. * non-pending runnable filtered guard. Update the
  1754. * <b>last_tried_to_connect</b> time and the <b>is_pending</b> fields of the
  1755. * guard as appropriate. Set <b>state_out</b> to the new guard-state
  1756. * of the circuit.
  1757. */
  1758. STATIC entry_guard_t *
  1759. select_entry_guard_for_circuit(guard_selection_t *gs,
  1760. guard_usage_t usage,
  1761. const entry_guard_restriction_t *rst,
  1762. unsigned *state_out)
  1763. {
  1764. const int need_descriptor = (usage == GUARD_USAGE_TRAFFIC);
  1765. tor_assert(gs);
  1766. tor_assert(state_out);
  1767. if (!gs->primary_guards_up_to_date)
  1768. entry_guards_update_primary(gs);
  1769. int num_entry_guards = get_n_primary_guards_to_use(usage);
  1770. smartlist_t *usable_primary_guards = smartlist_new();
  1771. /* "If any entry in PRIMARY_GUARDS has {is_reachable} status of
  1772. <maybe> or <yes>, return the first such guard." */
  1773. SMARTLIST_FOREACH_BEGIN(gs->primary_entry_guards, entry_guard_t *, guard) {
  1774. entry_guard_consider_retry(guard);
  1775. if (! entry_guard_obeys_restriction(guard, rst))
  1776. continue;
  1777. if (guard->is_reachable != GUARD_REACHABLE_NO) {
  1778. if (need_descriptor && !guard_has_descriptor(guard)) {
  1779. continue;
  1780. }
  1781. *state_out = GUARD_CIRC_STATE_USABLE_ON_COMPLETION;
  1782. guard->last_tried_to_connect = approx_time();
  1783. smartlist_add(usable_primary_guards, guard);
  1784. if (smartlist_len(usable_primary_guards) >= num_entry_guards)
  1785. break;
  1786. }
  1787. } SMARTLIST_FOREACH_END(guard);
  1788. if (smartlist_len(usable_primary_guards)) {
  1789. entry_guard_t *guard = smartlist_choose(usable_primary_guards);
  1790. smartlist_free(usable_primary_guards);
  1791. log_info(LD_GUARD, "Selected primary guard %s for circuit.",
  1792. entry_guard_describe(guard));
  1793. return guard;
  1794. }
  1795. smartlist_free(usable_primary_guards);
  1796. /* "Otherwise, if the ordered intersection of {CONFIRMED_GUARDS}
  1797. and {USABLE_FILTERED_GUARDS} is nonempty, return the first
  1798. entry in that intersection that has {is_pending} set to
  1799. false." */
  1800. SMARTLIST_FOREACH_BEGIN(gs->confirmed_entry_guards, entry_guard_t *, guard) {
  1801. if (guard->is_primary)
  1802. continue; /* we already considered this one. */
  1803. if (! entry_guard_obeys_restriction(guard, rst))
  1804. continue;
  1805. entry_guard_consider_retry(guard);
  1806. if (guard->is_usable_filtered_guard && ! guard->is_pending) {
  1807. if (need_descriptor && !guard_has_descriptor(guard))
  1808. continue; /* not a bug */
  1809. guard->is_pending = 1;
  1810. guard->last_tried_to_connect = approx_time();
  1811. *state_out = GUARD_CIRC_STATE_USABLE_IF_NO_BETTER_GUARD;
  1812. log_info(LD_GUARD, "No primary guards available. Selected confirmed "
  1813. "guard %s for circuit. Will try other guards before using "
  1814. "this circuit.",
  1815. entry_guard_describe(guard));
  1816. return guard;
  1817. }
  1818. } SMARTLIST_FOREACH_END(guard);
  1819. /* "Otherwise, if there is no such entry, select a member at
  1820. random from {USABLE_FILTERED_GUARDS}." */
  1821. {
  1822. entry_guard_t *guard;
  1823. unsigned flags = 0;
  1824. if (need_descriptor)
  1825. flags |= SAMPLE_EXCLUDE_NO_DESCRIPTOR;
  1826. guard = sample_reachable_filtered_entry_guards(gs,
  1827. rst,
  1828. SAMPLE_EXCLUDE_CONFIRMED |
  1829. SAMPLE_EXCLUDE_PRIMARY |
  1830. SAMPLE_EXCLUDE_PENDING |
  1831. flags);
  1832. if (guard == NULL) {
  1833. log_info(LD_GUARD, "Absolutely no sampled guards were available. "
  1834. "Marking all guards for retry and starting from top again.");
  1835. mark_all_guards_maybe_reachable(gs);
  1836. return NULL;
  1837. }
  1838. guard->is_pending = 1;
  1839. guard->last_tried_to_connect = approx_time();
  1840. *state_out = GUARD_CIRC_STATE_USABLE_IF_NO_BETTER_GUARD;
  1841. log_info(LD_GUARD, "No primary or confirmed guards available. Selected "
  1842. "random guard %s for circuit. Will try other guards before "
  1843. "using this circuit.",
  1844. entry_guard_describe(guard));
  1845. return guard;
  1846. }
  1847. }
  1848. /**
  1849. * Note that we failed to connect to or build circuits through <b>guard</b>.
  1850. * Use with a guard returned by select_entry_guard_for_circuit().
  1851. */
  1852. STATIC void
  1853. entry_guards_note_guard_failure(guard_selection_t *gs,
  1854. entry_guard_t *guard)
  1855. {
  1856. tor_assert(gs);
  1857. guard->is_reachable = GUARD_REACHABLE_NO;
  1858. guard->is_usable_filtered_guard = 0;
  1859. guard->is_pending = 0;
  1860. if (guard->failing_since == 0)
  1861. guard->failing_since = approx_time();
  1862. log_info(LD_GUARD, "Recorded failure for %s%sguard %s",
  1863. guard->is_primary?"primary ":"",
  1864. guard->confirmed_idx>=0?"confirmed ":"",
  1865. entry_guard_describe(guard));
  1866. }
  1867. /**
  1868. * Note that we successfully connected to, and built a circuit through
  1869. * <b>guard</b>. Given the old guard-state of the circuit in <b>old_state</b>,
  1870. * return the new guard-state of the circuit.
  1871. *
  1872. * Be aware: the circuit is only usable when its guard-state becomes
  1873. * GUARD_CIRC_STATE_COMPLETE.
  1874. **/
  1875. STATIC unsigned
  1876. entry_guards_note_guard_success(guard_selection_t *gs,
  1877. entry_guard_t *guard,
  1878. unsigned old_state)
  1879. {
  1880. tor_assert(gs);
  1881. /* Save this, since we're about to overwrite it. */
  1882. const time_t last_time_on_internet = gs->last_time_on_internet;
  1883. gs->last_time_on_internet = approx_time();
  1884. guard->is_reachable = GUARD_REACHABLE_YES;
  1885. guard->failing_since = 0;
  1886. guard->is_pending = 0;
  1887. if (guard->is_filtered_guard)
  1888. guard->is_usable_filtered_guard = 1;
  1889. if (guard->confirmed_idx < 0) {
  1890. make_guard_confirmed(gs, guard);
  1891. if (!gs->primary_guards_up_to_date)
  1892. entry_guards_update_primary(gs);
  1893. }
  1894. unsigned new_state;
  1895. switch (old_state) {
  1896. case GUARD_CIRC_STATE_COMPLETE:
  1897. case GUARD_CIRC_STATE_USABLE_ON_COMPLETION:
  1898. new_state = GUARD_CIRC_STATE_COMPLETE;
  1899. break;
  1900. default:
  1901. tor_assert_nonfatal_unreached();
  1902. /* Fall through. */
  1903. case GUARD_CIRC_STATE_USABLE_IF_NO_BETTER_GUARD:
  1904. if (guard->is_primary) {
  1905. /* XXXX #20832 -- I don't actually like this logic. It seems to make
  1906. * us a little more susceptible to evil-ISP attacks. The mitigations
  1907. * I'm thinking of, however, aren't local to this point, so I'll leave
  1908. * it alone. */
  1909. /* This guard may have become primary by virtue of being confirmed.
  1910. * If so, the circuit for it is now complete.
  1911. */
  1912. new_state = GUARD_CIRC_STATE_COMPLETE;
  1913. } else {
  1914. new_state = GUARD_CIRC_STATE_WAITING_FOR_BETTER_GUARD;
  1915. }
  1916. break;
  1917. }
  1918. if (! guard->is_primary) {
  1919. if (last_time_on_internet + get_internet_likely_down_interval()
  1920. < approx_time()) {
  1921. mark_primary_guards_maybe_reachable(gs);
  1922. }
  1923. }
  1924. log_info(LD_GUARD, "Recorded success for %s%sguard %s",
  1925. guard->is_primary?"primary ":"",
  1926. guard->confirmed_idx>=0?"confirmed ":"",
  1927. entry_guard_describe(guard));
  1928. return new_state;
  1929. }
  1930. /**
  1931. * Helper: Return true iff <b>a</b> has higher priority than <b>b</b>.
  1932. */
  1933. STATIC int
  1934. entry_guard_has_higher_priority(entry_guard_t *a, entry_guard_t *b)
  1935. {
  1936. tor_assert(a && b);
  1937. if (a == b)
  1938. return 0;
  1939. /* Confirmed is always better than unconfirmed; lower index better
  1940. than higher */
  1941. if (a->confirmed_idx < 0) {
  1942. if (b->confirmed_idx >= 0)
  1943. return 0;
  1944. } else {
  1945. if (b->confirmed_idx < 0)
  1946. return 1;
  1947. /* Lower confirmed_idx is better than higher. */
  1948. return (a->confirmed_idx < b->confirmed_idx);
  1949. }
  1950. /* If we reach this point, both are unconfirmed. If one is pending, it
  1951. * has higher priority. */
  1952. if (a->is_pending) {
  1953. if (! b->is_pending)
  1954. return 1;
  1955. /* Both are pending: earlier last_tried_connect wins. */
  1956. return a->last_tried_to_connect < b->last_tried_to_connect;
  1957. } else {
  1958. if (b->is_pending)
  1959. return 0;
  1960. /* Neither is pending: priorities are equal. */
  1961. return 0;
  1962. }
  1963. }
  1964. /** Release all storage held in <b>restriction</b> */
  1965. STATIC void
  1966. entry_guard_restriction_free(entry_guard_restriction_t *rst)
  1967. {
  1968. tor_free(rst);
  1969. }
  1970. /**
  1971. * Release all storage held in <b>state</b>.
  1972. */
  1973. void
  1974. circuit_guard_state_free(circuit_guard_state_t *state)
  1975. {
  1976. if (!state)
  1977. return;
  1978. entry_guard_restriction_free(state->restrictions);
  1979. entry_guard_handle_free(state->guard);
  1980. tor_free(state);
  1981. }
  1982. /** Allocate and return a new circuit_guard_state_t to track the result
  1983. * of using <b>guard</b> for a given operation. */
  1984. static circuit_guard_state_t *
  1985. circuit_guard_state_new(entry_guard_t *guard, unsigned state,
  1986. entry_guard_restriction_t *rst)
  1987. {
  1988. circuit_guard_state_t *result;
  1989. result = tor_malloc_zero(sizeof(circuit_guard_state_t));
  1990. result->guard = entry_guard_handle_new(guard);
  1991. result->state = state;
  1992. result->state_set_at = approx_time();
  1993. result->restrictions = rst;
  1994. return result;
  1995. }
  1996. /**
  1997. * Pick a suitable entry guard for a circuit in, and place that guard
  1998. * in *<b>chosen_node_out</b>. Set *<b>guard_state_out</b> to an opaque
  1999. * state object that will record whether the circuit is ready to be used
  2000. * or not. Return 0 on success; on failure, return -1.
  2001. *
  2002. * If a restriction is provided in <b>rst</b>, do not return any guards that
  2003. * violate it, and remember that restriction in <b>guard_state_out</b> for
  2004. * later use. (Takes ownership of the <b>rst</b> object.)
  2005. */
  2006. int
  2007. entry_guard_pick_for_circuit(guard_selection_t *gs,
  2008. guard_usage_t usage,
  2009. entry_guard_restriction_t *rst,
  2010. const node_t **chosen_node_out,
  2011. circuit_guard_state_t **guard_state_out)
  2012. {
  2013. tor_assert(gs);
  2014. tor_assert(chosen_node_out);
  2015. tor_assert(guard_state_out);
  2016. *chosen_node_out = NULL;
  2017. *guard_state_out = NULL;
  2018. unsigned state = 0;
  2019. entry_guard_t *guard =
  2020. select_entry_guard_for_circuit(gs, usage, rst, &state);
  2021. if (! guard)
  2022. goto fail;
  2023. if (BUG(state == 0))
  2024. goto fail;
  2025. const node_t *node = node_get_by_id(guard->identity);
  2026. // XXXX #20827 check Ed ID.
  2027. if (! node)
  2028. goto fail;
  2029. if (BUG(usage != GUARD_USAGE_DIRGUARD && !node_has_descriptor(node)))
  2030. goto fail;
  2031. *chosen_node_out = node;
  2032. *guard_state_out = circuit_guard_state_new(guard, state, rst);
  2033. return 0;
  2034. fail:
  2035. entry_guard_restriction_free(rst);
  2036. return -1;
  2037. }
  2038. /**
  2039. * Called by the circuit building module when a circuit has succeeded: informs
  2040. * the guards code that the guard in *<b>guard_state_p</b> is working, and
  2041. * advances the state of the guard module. On a GUARD_USABLE_NEVER return
  2042. * value, the circuit is broken and should not be used. On a GUARD_USABLE_NOW
  2043. * return value, the circuit is ready to use. On a GUARD_MAYBE_USABLE_LATER
  2044. * return value, the circuit should not be used until we find out whether
  2045. * preferred guards will work for us.
  2046. */
  2047. guard_usable_t
  2048. entry_guard_succeeded(circuit_guard_state_t **guard_state_p)
  2049. {
  2050. if (BUG(*guard_state_p == NULL))
  2051. return GUARD_USABLE_NEVER;
  2052. entry_guard_t *guard = entry_guard_handle_get((*guard_state_p)->guard);
  2053. if (! guard || BUG(guard->in_selection == NULL))
  2054. return GUARD_USABLE_NEVER;
  2055. unsigned newstate =
  2056. entry_guards_note_guard_success(guard->in_selection, guard,
  2057. (*guard_state_p)->state);
  2058. (*guard_state_p)->state = newstate;
  2059. (*guard_state_p)->state_set_at = approx_time();
  2060. if (newstate == GUARD_CIRC_STATE_COMPLETE) {
  2061. return GUARD_USABLE_NOW;
  2062. } else {
  2063. return GUARD_MAYBE_USABLE_LATER;
  2064. }
  2065. }
  2066. /** Cancel the selection of *<b>guard_state_p</b> without declaring
  2067. * success or failure. It is safe to call this function if success or
  2068. * failure _has_ already been declared. */
  2069. void
  2070. entry_guard_cancel(circuit_guard_state_t **guard_state_p)
  2071. {
  2072. if (BUG(*guard_state_p == NULL))
  2073. return;
  2074. entry_guard_t *guard = entry_guard_handle_get((*guard_state_p)->guard);
  2075. if (! guard)
  2076. return;
  2077. /* XXXX prop271 -- last_tried_to_connect_at will be erroneous here, but this
  2078. * function will only get called in "bug" cases anyway. */
  2079. guard->is_pending = 0;
  2080. circuit_guard_state_free(*guard_state_p);
  2081. *guard_state_p = NULL;
  2082. }
  2083. /**
  2084. * Called by the circuit building module when a circuit has succeeded:
  2085. * informs the guards code that the guard in *<b>guard_state_p</b> is
  2086. * not working, and advances the state of the guard module.
  2087. */
  2088. void
  2089. entry_guard_failed(circuit_guard_state_t **guard_state_p)
  2090. {
  2091. if (BUG(*guard_state_p == NULL))
  2092. return;
  2093. entry_guard_t *guard = entry_guard_handle_get((*guard_state_p)->guard);
  2094. if (! guard || BUG(guard->in_selection == NULL))
  2095. return;
  2096. entry_guards_note_guard_failure(guard->in_selection, guard);
  2097. (*guard_state_p)->state = GUARD_CIRC_STATE_DEAD;
  2098. (*guard_state_p)->state_set_at = approx_time();
  2099. }
  2100. /**
  2101. * Run the entry_guard_failed() function on every circuit that is
  2102. * pending on <b>chan</b>.
  2103. */
  2104. void
  2105. entry_guard_chan_failed(channel_t *chan)
  2106. {
  2107. if (!chan)
  2108. return;
  2109. smartlist_t *pending = smartlist_new();
  2110. circuit_get_all_pending_on_channel(pending, chan);
  2111. SMARTLIST_FOREACH_BEGIN(pending, circuit_t *, circ) {
  2112. if (!CIRCUIT_IS_ORIGIN(circ))
  2113. continue;
  2114. origin_circuit_t *origin_circ = TO_ORIGIN_CIRCUIT(circ);
  2115. if (origin_circ->guard_state) {
  2116. /* We might have no guard state if we didn't use a guard on this
  2117. * circuit (eg it's for a fallback directory). */
  2118. entry_guard_failed(&origin_circ->guard_state);
  2119. }
  2120. } SMARTLIST_FOREACH_END(circ);
  2121. smartlist_free(pending);
  2122. }
  2123. /**
  2124. * Return true iff every primary guard in <b>gs</b> is believed to
  2125. * be unreachable.
  2126. */
  2127. STATIC int
  2128. entry_guards_all_primary_guards_are_down(guard_selection_t *gs)
  2129. {
  2130. tor_assert(gs);
  2131. if (!gs->primary_guards_up_to_date)
  2132. entry_guards_update_primary(gs);
  2133. SMARTLIST_FOREACH_BEGIN(gs->primary_entry_guards, entry_guard_t *, guard) {
  2134. entry_guard_consider_retry(guard);
  2135. if (guard->is_reachable != GUARD_REACHABLE_NO)
  2136. return 0;
  2137. } SMARTLIST_FOREACH_END(guard);
  2138. return 1;
  2139. }
  2140. /** Wrapper for entry_guard_has_higher_priority that compares the
  2141. * guard-priorities of a pair of circuits. Return 1 if <b>a</b> has higher
  2142. * priority than <b>b</b>.
  2143. *
  2144. * If a restriction is provided in <b>rst</b>, then do not consider
  2145. * <b>a</b> to have higher priority if it violates the restriction.
  2146. */
  2147. static int
  2148. circ_state_has_higher_priority(origin_circuit_t *a,
  2149. const entry_guard_restriction_t *rst,
  2150. origin_circuit_t *b)
  2151. {
  2152. circuit_guard_state_t *state_a = origin_circuit_get_guard_state(a);
  2153. circuit_guard_state_t *state_b = origin_circuit_get_guard_state(b);
  2154. tor_assert(state_a);
  2155. tor_assert(state_b);
  2156. entry_guard_t *guard_a = entry_guard_handle_get(state_a->guard);
  2157. entry_guard_t *guard_b = entry_guard_handle_get(state_b->guard);
  2158. if (! guard_a) {
  2159. /* Unknown guard -- never higher priority. */
  2160. return 0;
  2161. } else if (! guard_b) {
  2162. /* Known guard -- higher priority than any unknown guard. */
  2163. return 1;
  2164. } else if (! entry_guard_obeys_restriction(guard_a, rst)) {
  2165. /* Restriction violated; guard_a cannot have higher priority. */
  2166. return 0;
  2167. } else {
  2168. /* Both known -- compare.*/
  2169. return entry_guard_has_higher_priority(guard_a, guard_b);
  2170. }
  2171. }
  2172. /**
  2173. * Look at all of the origin_circuit_t * objects in <b>all_circuits_in</b>,
  2174. * and see if any of them that were previously not ready to use for
  2175. * guard-related reasons are now ready to use. Place those circuits
  2176. * in <b>newly_complete_out</b>, and mark them COMPLETE.
  2177. *
  2178. * Return 1 if we upgraded any circuits, and 0 otherwise.
  2179. */
  2180. int
  2181. entry_guards_upgrade_waiting_circuits(guard_selection_t *gs,
  2182. const smartlist_t *all_circuits_in,
  2183. smartlist_t *newly_complete_out)
  2184. {
  2185. tor_assert(gs);
  2186. tor_assert(all_circuits_in);
  2187. tor_assert(newly_complete_out);
  2188. if (! entry_guards_all_primary_guards_are_down(gs)) {
  2189. /* We only upgrade a waiting circuit if the primary guards are all
  2190. * down. */
  2191. log_debug(LD_GUARD, "Considered upgrading guard-stalled circuits, "
  2192. "but not all primary guards were definitely down.");
  2193. return 0;
  2194. }
  2195. int n_waiting = 0;
  2196. int n_complete = 0;
  2197. int n_complete_blocking = 0;
  2198. origin_circuit_t *best_waiting_circuit = NULL;
  2199. smartlist_t *all_circuits = smartlist_new();
  2200. SMARTLIST_FOREACH_BEGIN(all_circuits_in, origin_circuit_t *, circ) {
  2201. // We filter out circuits that aren't ours, or which we can't
  2202. // reason about.
  2203. circuit_guard_state_t *state = origin_circuit_get_guard_state(circ);
  2204. if (state == NULL)
  2205. continue;
  2206. entry_guard_t *guard = entry_guard_handle_get(state->guard);
  2207. if (!guard || guard->in_selection != gs)
  2208. continue;
  2209. smartlist_add(all_circuits, circ);
  2210. } SMARTLIST_FOREACH_END(circ);
  2211. SMARTLIST_FOREACH_BEGIN(all_circuits, origin_circuit_t *, circ) {
  2212. circuit_guard_state_t *state = origin_circuit_get_guard_state(circ);
  2213. if (BUG(state == NULL))
  2214. continue;
  2215. if (state->state == GUARD_CIRC_STATE_WAITING_FOR_BETTER_GUARD) {
  2216. ++n_waiting;
  2217. if (! best_waiting_circuit ||
  2218. circ_state_has_higher_priority(circ, NULL, best_waiting_circuit)) {
  2219. best_waiting_circuit = circ;
  2220. }
  2221. }
  2222. } SMARTLIST_FOREACH_END(circ);
  2223. if (! best_waiting_circuit) {
  2224. log_debug(LD_GUARD, "Considered upgrading guard-stalled circuits, "
  2225. "but didn't find any.");
  2226. goto no_change;
  2227. }
  2228. /* We'll need to keep track of what restrictions were used when picking this
  2229. * circuit, so that we don't allow any circuit without those restrictions to
  2230. * block it. */
  2231. const entry_guard_restriction_t *rst_on_best_waiting =
  2232. origin_circuit_get_guard_state(best_waiting_circuit)->restrictions;
  2233. /* First look at the complete circuits: Do any block this circuit? */
  2234. SMARTLIST_FOREACH_BEGIN(all_circuits, origin_circuit_t *, circ) {
  2235. /* "C2 "blocks" C1 if:
  2236. * C2 obeys all the restrictions that C1 had to obey, AND
  2237. * C2 has higher priority than C1, AND
  2238. * Either C2 is <complete>, or C2 is <waiting_for_better_guard>,
  2239. or C2 has been <usable_if_no_better_guard> for no more than
  2240. {NONPRIMARY_GUARD_CONNECT_TIMEOUT} seconds."
  2241. */
  2242. circuit_guard_state_t *state = origin_circuit_get_guard_state(circ);
  2243. if BUG((state == NULL))
  2244. continue;
  2245. if (state->state != GUARD_CIRC_STATE_COMPLETE)
  2246. continue;
  2247. ++n_complete;
  2248. if (circ_state_has_higher_priority(circ, rst_on_best_waiting,
  2249. best_waiting_circuit))
  2250. ++n_complete_blocking;
  2251. } SMARTLIST_FOREACH_END(circ);
  2252. if (n_complete_blocking) {
  2253. log_debug(LD_GUARD, "Considered upgrading guard-stalled circuits: found "
  2254. "%d complete and %d guard-stalled. At least one complete "
  2255. "circuit had higher priority, so not upgrading.",
  2256. n_complete, n_waiting);
  2257. goto no_change;
  2258. }
  2259. /* " * If any circuit C1 is <waiting_for_better_guard>, AND:
  2260. * All primary guards have reachable status of <no>.
  2261. * There is no circuit C2 that "blocks" C1.
  2262. Then, upgrade C1 to <complete>.""
  2263. */
  2264. int n_blockers_found = 0;
  2265. const time_t state_set_at_cutoff =
  2266. approx_time() - get_nonprimary_guard_connect_timeout();
  2267. SMARTLIST_FOREACH_BEGIN(all_circuits, origin_circuit_t *, circ) {
  2268. circuit_guard_state_t *state = origin_circuit_get_guard_state(circ);
  2269. if (BUG(state == NULL))
  2270. continue;
  2271. if (state->state != GUARD_CIRC_STATE_USABLE_IF_NO_BETTER_GUARD)
  2272. continue;
  2273. if (state->state_set_at <= state_set_at_cutoff)
  2274. continue;
  2275. if (circ_state_has_higher_priority(circ, rst_on_best_waiting,
  2276. best_waiting_circuit))
  2277. ++n_blockers_found;
  2278. } SMARTLIST_FOREACH_END(circ);
  2279. if (n_blockers_found) {
  2280. log_debug(LD_GUARD, "Considered upgrading guard-stalled circuits: found "
  2281. "%d guard-stalled, but %d pending circuit(s) had higher "
  2282. "guard priority, so not upgrading.",
  2283. n_waiting, n_blockers_found);
  2284. goto no_change;
  2285. }
  2286. /* Okay. We have a best waiting circuit, and we aren't waiting for
  2287. anything better. Add all circuits with that priority to the
  2288. list, and call them COMPLETE. */
  2289. int n_succeeded = 0;
  2290. SMARTLIST_FOREACH_BEGIN(all_circuits, origin_circuit_t *, circ) {
  2291. circuit_guard_state_t *state = origin_circuit_get_guard_state(circ);
  2292. if (BUG(state == NULL))
  2293. continue;
  2294. if (circ != best_waiting_circuit && rst_on_best_waiting) {
  2295. /* Can't upgrade other circ with same priority as best; might
  2296. be blocked. */
  2297. continue;
  2298. }
  2299. if (state->state != GUARD_CIRC_STATE_WAITING_FOR_BETTER_GUARD)
  2300. continue;
  2301. if (circ_state_has_higher_priority(best_waiting_circuit, NULL, circ))
  2302. continue;
  2303. state->state = GUARD_CIRC_STATE_COMPLETE;
  2304. state->state_set_at = approx_time();
  2305. smartlist_add(newly_complete_out, circ);
  2306. ++n_succeeded;
  2307. } SMARTLIST_FOREACH_END(circ);
  2308. log_info(LD_GUARD, "Considered upgrading guard-stalled circuits: found "
  2309. "%d guard-stalled, %d complete. %d of the guard-stalled "
  2310. "circuit(s) had high enough priority to upgrade.",
  2311. n_waiting, n_complete, n_succeeded);
  2312. tor_assert_nonfatal(n_succeeded >= 1);
  2313. smartlist_free(all_circuits);
  2314. return 1;
  2315. no_change:
  2316. smartlist_free(all_circuits);
  2317. return 0;
  2318. }
  2319. /**
  2320. * Return true iff the circuit whose state is <b>guard_state</b> should
  2321. * expire.
  2322. */
  2323. int
  2324. entry_guard_state_should_expire(circuit_guard_state_t *guard_state)
  2325. {
  2326. if (guard_state == NULL)
  2327. return 0;
  2328. const time_t expire_if_waiting_since =
  2329. approx_time() - get_nonprimary_guard_idle_timeout();
  2330. return (guard_state->state == GUARD_CIRC_STATE_WAITING_FOR_BETTER_GUARD
  2331. && guard_state->state_set_at < expire_if_waiting_since);
  2332. }
  2333. /**
  2334. * Update all derived pieces of the guard selection state in <b>gs</b>.
  2335. * Return true iff we should stop using all previously generated circuits.
  2336. */
  2337. int
  2338. entry_guards_update_all(guard_selection_t *gs)
  2339. {
  2340. sampled_guards_update_from_consensus(gs);
  2341. entry_guards_update_filtered_sets(gs);
  2342. entry_guards_update_confirmed(gs);
  2343. entry_guards_update_primary(gs);
  2344. return 0;
  2345. }
  2346. /**
  2347. * Return a newly allocated string for encoding the persistent parts of
  2348. * <b>guard</b> to the state file.
  2349. */
  2350. STATIC char *
  2351. entry_guard_encode_for_state(entry_guard_t *guard)
  2352. {
  2353. /*
  2354. * The meta-format we use is K=V K=V K=V... where K can be any
  2355. * characters excepts space and =, and V can be any characters except
  2356. * space. The order of entries is not allowed to matter.
  2357. * Unrecognized K=V entries are persisted; recognized but erroneous
  2358. * entries are corrected.
  2359. */
  2360. smartlist_t *result = smartlist_new();
  2361. char tbuf[ISO_TIME_LEN+1];
  2362. tor_assert(guard);
  2363. smartlist_add_asprintf(result, "in=%s", guard->selection_name);
  2364. smartlist_add_asprintf(result, "rsa_id=%s",
  2365. hex_str(guard->identity, DIGEST_LEN));
  2366. if (guard->bridge_addr) {
  2367. smartlist_add_asprintf(result, "bridge_addr=%s:%d",
  2368. fmt_and_decorate_addr(&guard->bridge_addr->addr),
  2369. guard->bridge_addr->port);
  2370. }
  2371. if (strlen(guard->nickname) && is_legal_nickname(guard->nickname)) {
  2372. smartlist_add_asprintf(result, "nickname=%s", guard->nickname);
  2373. }
  2374. format_iso_time_nospace(tbuf, guard->sampled_on_date);
  2375. smartlist_add_asprintf(result, "sampled_on=%s", tbuf);
  2376. if (guard->sampled_by_version) {
  2377. smartlist_add_asprintf(result, "sampled_by=%s",
  2378. guard->sampled_by_version);
  2379. }
  2380. if (guard->unlisted_since_date > 0) {
  2381. format_iso_time_nospace(tbuf, guard->unlisted_since_date);
  2382. smartlist_add_asprintf(result, "unlisted_since=%s", tbuf);
  2383. }
  2384. smartlist_add_asprintf(result, "listed=%d",
  2385. (int)guard->currently_listed);
  2386. if (guard->confirmed_idx >= 0) {
  2387. format_iso_time_nospace(tbuf, guard->confirmed_on_date);
  2388. smartlist_add_asprintf(result, "confirmed_on=%s", tbuf);
  2389. smartlist_add_asprintf(result, "confirmed_idx=%d", guard->confirmed_idx);
  2390. }
  2391. const double EPSILON = 1.0e-6;
  2392. /* Make a copy of the pathbias object, since we will want to update
  2393. some of them */
  2394. guard_pathbias_t *pb = tor_memdup(&guard->pb, sizeof(*pb));
  2395. pb->use_successes = pathbias_get_use_success_count(guard);
  2396. pb->successful_circuits_closed = pathbias_get_close_success_count(guard);
  2397. #define PB_FIELD(field) do { \
  2398. if (pb->field >= EPSILON) { \
  2399. smartlist_add_asprintf(result, "pb_" #field "=%f", pb->field); \
  2400. } \
  2401. } while (0)
  2402. PB_FIELD(use_attempts);
  2403. PB_FIELD(use_successes);
  2404. PB_FIELD(circ_attempts);
  2405. PB_FIELD(circ_successes);
  2406. PB_FIELD(successful_circuits_closed);
  2407. PB_FIELD(collapsed_circuits);
  2408. PB_FIELD(unusable_circuits);
  2409. PB_FIELD(timeouts);
  2410. tor_free(pb);
  2411. #undef PB_FIELD
  2412. if (guard->extra_state_fields)
  2413. smartlist_add_strdup(result, guard->extra_state_fields);
  2414. char *joined = smartlist_join_strings(result, " ", 0, NULL);
  2415. SMARTLIST_FOREACH(result, char *, cp, tor_free(cp));
  2416. smartlist_free(result);
  2417. return joined;
  2418. }
  2419. /**
  2420. * Given a string generated by entry_guard_encode_for_state(), parse it
  2421. * (if possible) and return an entry_guard_t object for it. Return NULL
  2422. * on complete failure.
  2423. */
  2424. STATIC entry_guard_t *
  2425. entry_guard_parse_from_state(const char *s)
  2426. {
  2427. /* Unrecognized entries get put in here. */
  2428. smartlist_t *extra = smartlist_new();
  2429. /* These fields get parsed from the string. */
  2430. char *in = NULL;
  2431. char *rsa_id = NULL;
  2432. char *nickname = NULL;
  2433. char *sampled_on = NULL;
  2434. char *sampled_by = NULL;
  2435. char *unlisted_since = NULL;
  2436. char *listed = NULL;
  2437. char *confirmed_on = NULL;
  2438. char *confirmed_idx = NULL;
  2439. char *bridge_addr = NULL;
  2440. // pathbias
  2441. char *pb_use_attempts = NULL;
  2442. char *pb_use_successes = NULL;
  2443. char *pb_circ_attempts = NULL;
  2444. char *pb_circ_successes = NULL;
  2445. char *pb_successful_circuits_closed = NULL;
  2446. char *pb_collapsed_circuits = NULL;
  2447. char *pb_unusable_circuits = NULL;
  2448. char *pb_timeouts = NULL;
  2449. /* Split up the entries. Put the ones we know about in strings and the
  2450. * rest in "extra". */
  2451. {
  2452. smartlist_t *entries = smartlist_new();
  2453. strmap_t *vals = strmap_new(); // Maps keyword to location
  2454. #define FIELD(f) \
  2455. strmap_set(vals, #f, &f);
  2456. FIELD(in);
  2457. FIELD(rsa_id);
  2458. FIELD(nickname);
  2459. FIELD(sampled_on);
  2460. FIELD(sampled_by);
  2461. FIELD(unlisted_since);
  2462. FIELD(listed);
  2463. FIELD(confirmed_on);
  2464. FIELD(confirmed_idx);
  2465. FIELD(bridge_addr);
  2466. FIELD(pb_use_attempts);
  2467. FIELD(pb_use_successes);
  2468. FIELD(pb_circ_attempts);
  2469. FIELD(pb_circ_successes);
  2470. FIELD(pb_successful_circuits_closed);
  2471. FIELD(pb_collapsed_circuits);
  2472. FIELD(pb_unusable_circuits);
  2473. FIELD(pb_timeouts);
  2474. #undef FIELD
  2475. smartlist_split_string(entries, s, " ",
  2476. SPLIT_SKIP_SPACE|SPLIT_IGNORE_BLANK, 0);
  2477. SMARTLIST_FOREACH_BEGIN(entries, char *, entry) {
  2478. const char *eq = strchr(entry, '=');
  2479. if (!eq) {
  2480. smartlist_add(extra, entry);
  2481. continue;
  2482. }
  2483. char *key = tor_strndup(entry, eq-entry);
  2484. char **target = strmap_get(vals, key);
  2485. if (target == NULL || *target != NULL) {
  2486. /* unrecognized or already set */
  2487. smartlist_add(extra, entry);
  2488. tor_free(key);
  2489. continue;
  2490. }
  2491. *target = tor_strdup(eq+1);
  2492. tor_free(key);
  2493. tor_free(entry);
  2494. } SMARTLIST_FOREACH_END(entry);
  2495. smartlist_free(entries);
  2496. strmap_free(vals, NULL);
  2497. }
  2498. entry_guard_t *guard = tor_malloc_zero(sizeof(entry_guard_t));
  2499. guard->is_persistent = 1;
  2500. if (in == NULL) {
  2501. log_warn(LD_CIRC, "Guard missing 'in' field");
  2502. goto err;
  2503. }
  2504. guard->selection_name = in;
  2505. in = NULL;
  2506. if (rsa_id == NULL) {
  2507. log_warn(LD_CIRC, "Guard missing RSA ID field");
  2508. goto err;
  2509. }
  2510. /* Process the identity and nickname. */
  2511. if (base16_decode(guard->identity, sizeof(guard->identity),
  2512. rsa_id, strlen(rsa_id)) != DIGEST_LEN) {
  2513. log_warn(LD_CIRC, "Unable to decode guard identity %s", escaped(rsa_id));
  2514. goto err;
  2515. }
  2516. if (nickname) {
  2517. strlcpy(guard->nickname, nickname, sizeof(guard->nickname));
  2518. } else {
  2519. guard->nickname[0]='$';
  2520. base16_encode(guard->nickname+1, sizeof(guard->nickname)-1,
  2521. guard->identity, DIGEST_LEN);
  2522. }
  2523. if (bridge_addr) {
  2524. tor_addr_port_t res;
  2525. memset(&res, 0, sizeof(res));
  2526. int r = tor_addr_port_parse(LOG_WARN, bridge_addr,
  2527. &res.addr, &res.port, -1);
  2528. if (r == 0)
  2529. guard->bridge_addr = tor_memdup(&res, sizeof(res));
  2530. /* On error, we already warned. */
  2531. }
  2532. /* Process the various time fields. */
  2533. #define HANDLE_TIME(field) do { \
  2534. if (field) { \
  2535. int r = parse_iso_time_nospace(field, &field ## _time); \
  2536. if (r < 0) { \
  2537. log_warn(LD_CIRC, "Unable to parse %s %s from guard", \
  2538. #field, escaped(field)); \
  2539. field##_time = -1; \
  2540. } \
  2541. } \
  2542. } while (0)
  2543. time_t sampled_on_time = 0;
  2544. time_t unlisted_since_time = 0;
  2545. time_t confirmed_on_time = 0;
  2546. HANDLE_TIME(sampled_on);
  2547. HANDLE_TIME(unlisted_since);
  2548. HANDLE_TIME(confirmed_on);
  2549. if (sampled_on_time <= 0)
  2550. sampled_on_time = approx_time();
  2551. if (unlisted_since_time < 0)
  2552. unlisted_since_time = 0;
  2553. if (confirmed_on_time < 0)
  2554. confirmed_on_time = 0;
  2555. #undef HANDLE_TIME
  2556. guard->sampled_on_date = sampled_on_time;
  2557. guard->unlisted_since_date = unlisted_since_time;
  2558. guard->confirmed_on_date = confirmed_on_time;
  2559. /* Take sampled_by_version verbatim. */
  2560. guard->sampled_by_version = sampled_by;
  2561. sampled_by = NULL; /* prevent free */
  2562. /* Listed is a boolean */
  2563. if (listed && strcmp(listed, "0"))
  2564. guard->currently_listed = 1;
  2565. /* The index is a nonnegative integer. */
  2566. guard->confirmed_idx = -1;
  2567. if (confirmed_idx) {
  2568. int ok=1;
  2569. long idx = tor_parse_long(confirmed_idx, 10, 0, INT_MAX, &ok, NULL);
  2570. if (! ok) {
  2571. log_warn(LD_GUARD, "Guard has invalid confirmed_idx %s",
  2572. escaped(confirmed_idx));
  2573. } else {
  2574. guard->confirmed_idx = (int)idx;
  2575. }
  2576. }
  2577. /* Anything we didn't recognize gets crammed together */
  2578. if (smartlist_len(extra) > 0) {
  2579. guard->extra_state_fields = smartlist_join_strings(extra, " ", 0, NULL);
  2580. }
  2581. /* initialize non-persistent fields */
  2582. guard->is_reachable = GUARD_REACHABLE_MAYBE;
  2583. #define PB_FIELD(field) \
  2584. do { \
  2585. if (pb_ ## field) { \
  2586. int ok = 1; \
  2587. double r = tor_parse_double(pb_ ## field, 0.0, 1e9, &ok, NULL); \
  2588. if (! ok) { \
  2589. log_warn(LD_CIRC, "Guard has invalid pb_%s %s", \
  2590. #field, pb_ ## field); \
  2591. } else { \
  2592. guard->pb.field = r; \
  2593. } \
  2594. } \
  2595. } while (0)
  2596. PB_FIELD(use_attempts);
  2597. PB_FIELD(use_successes);
  2598. PB_FIELD(circ_attempts);
  2599. PB_FIELD(circ_successes);
  2600. PB_FIELD(successful_circuits_closed);
  2601. PB_FIELD(collapsed_circuits);
  2602. PB_FIELD(unusable_circuits);
  2603. PB_FIELD(timeouts);
  2604. #undef PB_FIELD
  2605. pathbias_check_use_success_count(guard);
  2606. pathbias_check_close_success_count(guard);
  2607. /* We update everything on this guard later, after we've parsed
  2608. * everything. */
  2609. goto done;
  2610. err:
  2611. // only consider it an error if the guard state was totally unparseable.
  2612. entry_guard_free(guard);
  2613. guard = NULL;
  2614. done:
  2615. tor_free(in);
  2616. tor_free(rsa_id);
  2617. tor_free(nickname);
  2618. tor_free(sampled_on);
  2619. tor_free(sampled_by);
  2620. tor_free(unlisted_since);
  2621. tor_free(listed);
  2622. tor_free(confirmed_on);
  2623. tor_free(confirmed_idx);
  2624. tor_free(bridge_addr);
  2625. tor_free(pb_use_attempts);
  2626. tor_free(pb_use_successes);
  2627. tor_free(pb_circ_attempts);
  2628. tor_free(pb_circ_successes);
  2629. tor_free(pb_successful_circuits_closed);
  2630. tor_free(pb_collapsed_circuits);
  2631. tor_free(pb_unusable_circuits);
  2632. tor_free(pb_timeouts);
  2633. SMARTLIST_FOREACH(extra, char *, cp, tor_free(cp));
  2634. smartlist_free(extra);
  2635. return guard;
  2636. }
  2637. /**
  2638. * Replace the Guards entries in <b>state</b> with a list of all our sampled
  2639. * guards.
  2640. */
  2641. static void
  2642. entry_guards_update_guards_in_state(or_state_t *state)
  2643. {
  2644. if (!guard_contexts)
  2645. return;
  2646. config_line_t *lines = NULL;
  2647. config_line_t **nextline = &lines;
  2648. SMARTLIST_FOREACH_BEGIN(guard_contexts, guard_selection_t *, gs) {
  2649. SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
  2650. if (guard->is_persistent == 0)
  2651. continue;
  2652. *nextline = tor_malloc_zero(sizeof(config_line_t));
  2653. (*nextline)->key = tor_strdup("Guard");
  2654. (*nextline)->value = entry_guard_encode_for_state(guard);
  2655. nextline = &(*nextline)->next;
  2656. } SMARTLIST_FOREACH_END(guard);
  2657. } SMARTLIST_FOREACH_END(gs);
  2658. config_free_lines(state->Guard);
  2659. state->Guard = lines;
  2660. }
  2661. /**
  2662. * Replace our sampled guards from the Guards entries in <b>state</b>. Return 0
  2663. * on success, -1 on failure. (If <b>set</b> is true, replace nothing -- only
  2664. * check whether replacing would work.)
  2665. */
  2666. static int
  2667. entry_guards_load_guards_from_state(or_state_t *state, int set)
  2668. {
  2669. const config_line_t *line = state->Guard;
  2670. int n_errors = 0;
  2671. if (!guard_contexts)
  2672. guard_contexts = smartlist_new();
  2673. /* Wipe all our existing guard info. (we shouldn't have any, but
  2674. * let's be safe.) */
  2675. if (set) {
  2676. SMARTLIST_FOREACH_BEGIN(guard_contexts, guard_selection_t *, gs) {
  2677. guard_selection_free(gs);
  2678. if (curr_guard_context == gs)
  2679. curr_guard_context = NULL;
  2680. SMARTLIST_DEL_CURRENT(guard_contexts, gs);
  2681. } SMARTLIST_FOREACH_END(gs);
  2682. }
  2683. for ( ; line != NULL; line = line->next) {
  2684. entry_guard_t *guard = entry_guard_parse_from_state(line->value);
  2685. if (guard == NULL) {
  2686. ++n_errors;
  2687. continue;
  2688. }
  2689. tor_assert(guard->selection_name);
  2690. if (!strcmp(guard->selection_name, "legacy")) {
  2691. ++n_errors;
  2692. entry_guard_free(guard);
  2693. continue;
  2694. }
  2695. if (set) {
  2696. guard_selection_t *gs;
  2697. gs = get_guard_selection_by_name(guard->selection_name,
  2698. GS_TYPE_INFER, 1);
  2699. tor_assert(gs);
  2700. smartlist_add(gs->sampled_entry_guards, guard);
  2701. guard->in_selection = gs;
  2702. } else {
  2703. entry_guard_free(guard);
  2704. }
  2705. }
  2706. if (set) {
  2707. SMARTLIST_FOREACH_BEGIN(guard_contexts, guard_selection_t *, gs) {
  2708. entry_guards_update_all(gs);
  2709. } SMARTLIST_FOREACH_END(gs);
  2710. }
  2711. return n_errors ? -1 : 0;
  2712. }
  2713. /** If <b>digest</b> matches the identity of any node in the
  2714. * entry_guards list for the provided guard selection state,
  2715. return that node. Else return NULL. */
  2716. entry_guard_t *
  2717. entry_guard_get_by_id_digest_for_guard_selection(guard_selection_t *gs,
  2718. const char *digest)
  2719. {
  2720. return get_sampled_guard_with_id(gs, (const uint8_t*)digest);
  2721. }
  2722. /** Return the node_t associated with a single entry_guard_t. May
  2723. * return NULL if the guard is not currently in the consensus. */
  2724. const node_t *
  2725. entry_guard_find_node(const entry_guard_t *guard)
  2726. {
  2727. tor_assert(guard);
  2728. return node_get_by_id(guard->identity);
  2729. }
  2730. /** If <b>digest</b> matches the identity of any node in the
  2731. * entry_guards list for the default guard selection state,
  2732. return that node. Else return NULL. */
  2733. entry_guard_t *
  2734. entry_guard_get_by_id_digest(const char *digest)
  2735. {
  2736. return entry_guard_get_by_id_digest_for_guard_selection(
  2737. get_guard_selection_info(), digest);
  2738. }
  2739. /** We are about to connect to bridge with identity <b>digest</b> to fetch its
  2740. * descriptor. Create a new guard state for this connection and return it. */
  2741. circuit_guard_state_t *
  2742. get_guard_state_for_bridge_desc_fetch(const char *digest)
  2743. {
  2744. circuit_guard_state_t *guard_state = NULL;
  2745. entry_guard_t *guard = NULL;
  2746. guard = entry_guard_get_by_id_digest_for_guard_selection(
  2747. get_guard_selection_info(), digest);
  2748. if (!guard) {
  2749. return NULL;
  2750. }
  2751. /* Update the guard last_tried_to_connect time since it's checked by the
  2752. * guard susbsystem. */
  2753. guard->last_tried_to_connect = approx_time();
  2754. /* Create the guard state */
  2755. guard_state = circuit_guard_state_new(guard,
  2756. GUARD_CIRC_STATE_USABLE_ON_COMPLETION,
  2757. NULL);
  2758. return guard_state;
  2759. }
  2760. /** Release all storage held by <b>e</b>. */
  2761. STATIC void
  2762. entry_guard_free(entry_guard_t *e)
  2763. {
  2764. if (!e)
  2765. return;
  2766. entry_guard_handles_clear(e);
  2767. tor_free(e->sampled_by_version);
  2768. tor_free(e->extra_state_fields);
  2769. tor_free(e->selection_name);
  2770. tor_free(e->bridge_addr);
  2771. tor_free(e);
  2772. }
  2773. /** Return 0 if we're fine adding arbitrary routers out of the
  2774. * directory to our entry guard list, or return 1 if we have a
  2775. * list already and we must stick to it.
  2776. */
  2777. int
  2778. entry_list_is_constrained(const or_options_t *options)
  2779. {
  2780. // XXXX #21425 look at the current selection.
  2781. if (options->EntryNodes)
  2782. return 1;
  2783. if (options->UseBridges)
  2784. return 1;
  2785. return 0;
  2786. }
  2787. /** Return the number of bridges that have descriptors that are marked with
  2788. * purpose 'bridge' and are running.
  2789. */
  2790. int
  2791. num_bridges_usable(void)
  2792. {
  2793. int n_options = 0;
  2794. tor_assert(get_options()->UseBridges);
  2795. guard_selection_t *gs = get_guard_selection_info();
  2796. tor_assert(gs->type == GS_TYPE_BRIDGE);
  2797. SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
  2798. if (guard->is_reachable == GUARD_REACHABLE_NO)
  2799. continue;
  2800. if (tor_digest_is_zero(guard->identity))
  2801. continue;
  2802. const node_t *node = node_get_by_id(guard->identity);
  2803. if (node && node->ri)
  2804. ++n_options;
  2805. } SMARTLIST_FOREACH_END(guard);
  2806. return n_options;
  2807. }
  2808. /** Check the pathbias use success count of <b>node</b> and disable it if it
  2809. * goes over our thresholds. */
  2810. static void
  2811. pathbias_check_use_success_count(entry_guard_t *node)
  2812. {
  2813. const or_options_t *options = get_options();
  2814. const double EPSILON = 1.0e-9;
  2815. /* Note: We rely on the < comparison here to allow us to set a 0
  2816. * rate and disable the feature entirely. If refactoring, don't
  2817. * change to <= */
  2818. if (node->pb.use_attempts > EPSILON &&
  2819. pathbias_get_use_success_count(node)/node->pb.use_attempts
  2820. < pathbias_get_extreme_use_rate(options) &&
  2821. pathbias_get_dropguards(options)) {
  2822. node->pb.path_bias_disabled = 1;
  2823. log_info(LD_GENERAL,
  2824. "Path use bias is too high (%f/%f); disabling node %s",
  2825. node->pb.circ_successes, node->pb.circ_attempts,
  2826. node->nickname);
  2827. }
  2828. }
  2829. /** Check the pathbias close count of <b>node</b> and disable it if it goes
  2830. * over our thresholds. */
  2831. static void
  2832. pathbias_check_close_success_count(entry_guard_t *node)
  2833. {
  2834. const or_options_t *options = get_options();
  2835. const double EPSILON = 1.0e-9;
  2836. /* Note: We rely on the < comparison here to allow us to set a 0
  2837. * rate and disable the feature entirely. If refactoring, don't
  2838. * change to <= */
  2839. if (node->pb.circ_attempts > EPSILON &&
  2840. pathbias_get_close_success_count(node)/node->pb.circ_attempts
  2841. < pathbias_get_extreme_rate(options) &&
  2842. pathbias_get_dropguards(options)) {
  2843. node->pb.path_bias_disabled = 1;
  2844. log_info(LD_GENERAL,
  2845. "Path bias is too high (%f/%f); disabling node %s",
  2846. node->pb.circ_successes, node->pb.circ_attempts,
  2847. node->nickname);
  2848. }
  2849. }
  2850. /** Parse <b>state</b> and learn about the entry guards it describes.
  2851. * If <b>set</b> is true, and there are no errors, replace the guard
  2852. * list in the default guard selection context with what we find.
  2853. * On success, return 0. On failure, alloc into *<b>msg</b> a string
  2854. * describing the error, and return -1.
  2855. */
  2856. int
  2857. entry_guards_parse_state(or_state_t *state, int set, char **msg)
  2858. {
  2859. entry_guards_dirty = 0;
  2860. int r1 = entry_guards_load_guards_from_state(state, set);
  2861. entry_guards_dirty = 0;
  2862. if (r1 < 0) {
  2863. if (msg && *msg == NULL) {
  2864. *msg = tor_strdup("parsing error");
  2865. }
  2866. return -1;
  2867. }
  2868. return 0;
  2869. }
  2870. /** How long will we let a change in our guard nodes stay un-saved
  2871. * when we are trying to avoid disk writes? */
  2872. #define SLOW_GUARD_STATE_FLUSH_TIME 600
  2873. /** How long will we let a change in our guard nodes stay un-saved
  2874. * when we are not trying to avoid disk writes? */
  2875. #define FAST_GUARD_STATE_FLUSH_TIME 30
  2876. /** Our list of entry guards has changed for a particular guard selection
  2877. * context, or some element of one of our entry guards has changed for one.
  2878. * Write the changes to disk within the next few minutes.
  2879. */
  2880. void
  2881. entry_guards_changed_for_guard_selection(guard_selection_t *gs)
  2882. {
  2883. time_t when;
  2884. tor_assert(gs != NULL);
  2885. entry_guards_dirty = 1;
  2886. if (get_options()->AvoidDiskWrites)
  2887. when = time(NULL) + SLOW_GUARD_STATE_FLUSH_TIME;
  2888. else
  2889. when = time(NULL) + FAST_GUARD_STATE_FLUSH_TIME;
  2890. /* or_state_save() will call entry_guards_update_state() and
  2891. entry_guards_update_guards_in_state()
  2892. */
  2893. or_state_mark_dirty(get_or_state(), when);
  2894. }
  2895. /** Our list of entry guards has changed for the default guard selection
  2896. * context, or some element of one of our entry guards has changed. Write
  2897. * the changes to disk within the next few minutes.
  2898. */
  2899. void
  2900. entry_guards_changed(void)
  2901. {
  2902. entry_guards_changed_for_guard_selection(get_guard_selection_info());
  2903. }
  2904. /** If the entry guard info has not changed, do nothing and return.
  2905. * Otherwise, free the EntryGuards piece of <b>state</b> and create
  2906. * a new one out of the global entry_guards list, and then mark
  2907. * <b>state</b> dirty so it will get saved to disk.
  2908. */
  2909. void
  2910. entry_guards_update_state(or_state_t *state)
  2911. {
  2912. entry_guards_dirty = 0;
  2913. // Handles all guard info.
  2914. entry_guards_update_guards_in_state(state);
  2915. entry_guards_dirty = 0;
  2916. if (!get_options()->AvoidDiskWrites)
  2917. or_state_mark_dirty(get_or_state(), 0);
  2918. entry_guards_dirty = 0;
  2919. }
  2920. /**
  2921. * Format a single entry guard in the format expected by the controller.
  2922. * Return a newly allocated string.
  2923. */
  2924. STATIC char *
  2925. getinfo_helper_format_single_entry_guard(const entry_guard_t *e)
  2926. {
  2927. const char *status = NULL;
  2928. time_t when = 0;
  2929. const node_t *node;
  2930. char tbuf[ISO_TIME_LEN+1];
  2931. char nbuf[MAX_VERBOSE_NICKNAME_LEN+1];
  2932. /* This is going to be a bit tricky, since the status
  2933. * codes weren't really intended for prop271 guards.
  2934. *
  2935. * XXXX use a more appropriate format for exporting this information
  2936. */
  2937. if (e->confirmed_idx < 0) {
  2938. status = "never-connected";
  2939. } else if (! e->currently_listed) {
  2940. when = e->unlisted_since_date;
  2941. status = "unusable";
  2942. } else if (! e->is_filtered_guard) {
  2943. status = "unusable";
  2944. } else if (e->is_reachable == GUARD_REACHABLE_NO) {
  2945. when = e->failing_since;
  2946. status = "down";
  2947. } else {
  2948. status = "up";
  2949. }
  2950. node = entry_guard_find_node(e);
  2951. if (node) {
  2952. node_get_verbose_nickname(node, nbuf);
  2953. } else {
  2954. nbuf[0] = '$';
  2955. base16_encode(nbuf+1, sizeof(nbuf)-1, e->identity, DIGEST_LEN);
  2956. /* e->nickname field is not very reliable if we don't know about
  2957. * this router any longer; don't include it. */
  2958. }
  2959. char *result = NULL;
  2960. if (when) {
  2961. format_iso_time(tbuf, when);
  2962. tor_asprintf(&result, "%s %s %s\n", nbuf, status, tbuf);
  2963. } else {
  2964. tor_asprintf(&result, "%s %s\n", nbuf, status);
  2965. }
  2966. return result;
  2967. }
  2968. /** If <b>question</b> is the string "entry-guards", then dump
  2969. * to *<b>answer</b> a newly allocated string describing all of
  2970. * the nodes in the global entry_guards list. See control-spec.txt
  2971. * for details.
  2972. * For backward compatibility, we also handle the string "helper-nodes".
  2973. *
  2974. * XXX this should be totally redesigned after prop 271 too, and that's
  2975. * going to take some control spec work.
  2976. * */
  2977. int
  2978. getinfo_helper_entry_guards(control_connection_t *conn,
  2979. const char *question, char **answer,
  2980. const char **errmsg)
  2981. {
  2982. guard_selection_t *gs = get_guard_selection_info();
  2983. tor_assert(gs != NULL);
  2984. (void) conn;
  2985. (void) errmsg;
  2986. if (!strcmp(question,"entry-guards") ||
  2987. !strcmp(question,"helper-nodes")) {
  2988. const smartlist_t *guards;
  2989. guards = gs->sampled_entry_guards;
  2990. smartlist_t *sl = smartlist_new();
  2991. SMARTLIST_FOREACH_BEGIN(guards, const entry_guard_t *, e) {
  2992. char *cp = getinfo_helper_format_single_entry_guard(e);
  2993. smartlist_add(sl, cp);
  2994. } SMARTLIST_FOREACH_END(e);
  2995. *answer = smartlist_join_strings(sl, "", 0, NULL);
  2996. SMARTLIST_FOREACH(sl, char *, c, tor_free(c));
  2997. smartlist_free(sl);
  2998. }
  2999. return 0;
  3000. }
  3001. /* Given the original bandwidth of a guard and its guardfraction,
  3002. * calculate how much bandwidth the guard should have as a guard and
  3003. * as a non-guard.
  3004. *
  3005. * Quoting from proposal236:
  3006. *
  3007. * Let Wpf denote the weight from the 'bandwidth-weights' line a
  3008. * client would apply to N for position p if it had the guard
  3009. * flag, Wpn the weight if it did not have the guard flag, and B the
  3010. * measured bandwidth of N in the consensus. Then instead of choosing
  3011. * N for position p proportionally to Wpf*B or Wpn*B, clients should
  3012. * choose N proportionally to F*Wpf*B + (1-F)*Wpn*B.
  3013. *
  3014. * This function fills the <b>guardfraction_bw</b> structure. It sets
  3015. * <b>guard_bw</b> to F*B and <b>non_guard_bw</b> to (1-F)*B.
  3016. */
  3017. void
  3018. guard_get_guardfraction_bandwidth(guardfraction_bandwidth_t *guardfraction_bw,
  3019. int orig_bandwidth,
  3020. uint32_t guardfraction_percentage)
  3021. {
  3022. double guardfraction_fraction;
  3023. /* Turn the percentage into a fraction. */
  3024. tor_assert(guardfraction_percentage <= 100);
  3025. guardfraction_fraction = guardfraction_percentage / 100.0;
  3026. long guard_bw = tor_lround(guardfraction_fraction * orig_bandwidth);
  3027. tor_assert(guard_bw <= INT_MAX);
  3028. guardfraction_bw->guard_bw = (int) guard_bw;
  3029. guardfraction_bw->non_guard_bw = orig_bandwidth - (int) guard_bw;
  3030. }
  3031. /** Helper: Update the status of all entry guards, in whatever algorithm
  3032. * is used. Return true if we should stop using all previously generated
  3033. * circuits, by calling circuit_mark_all_unused_circs() and
  3034. * circuit_mark_all_dirty_circs_as_unusable().
  3035. */
  3036. int
  3037. guards_update_all(void)
  3038. {
  3039. int mark_circuits = 0;
  3040. if (update_guard_selection_choice(get_options()))
  3041. mark_circuits = 1;
  3042. tor_assert(curr_guard_context);
  3043. if (entry_guards_update_all(curr_guard_context))
  3044. mark_circuits = 1;
  3045. return mark_circuits;
  3046. }
  3047. /** Helper: pick a guard for a circuit, with whatever algorithm is
  3048. used. */
  3049. const node_t *
  3050. guards_choose_guard(cpath_build_state_t *state,
  3051. circuit_guard_state_t **guard_state_out)
  3052. {
  3053. const node_t *r = NULL;
  3054. const uint8_t *exit_id = NULL;
  3055. entry_guard_restriction_t *rst = NULL;
  3056. if (state && (exit_id = build_state_get_exit_rsa_id(state))) {
  3057. /* We're building to a targeted exit node, so that node can't be
  3058. * chosen as our guard for this circuit. Remember that fact in a
  3059. * restriction. */
  3060. rst = guard_create_exit_restriction(exit_id);
  3061. tor_assert(rst);
  3062. }
  3063. if (entry_guard_pick_for_circuit(get_guard_selection_info(),
  3064. GUARD_USAGE_TRAFFIC,
  3065. rst,
  3066. &r,
  3067. guard_state_out) < 0) {
  3068. tor_assert(r == NULL);
  3069. }
  3070. return r;
  3071. }
  3072. /** Remove all currently listed entry guards for a given guard selection
  3073. * context. This frees and replaces <b>gs</b>, so don't use <b>gs</b>
  3074. * after calling this function. */
  3075. void
  3076. remove_all_entry_guards_for_guard_selection(guard_selection_t *gs)
  3077. {
  3078. // This function shouldn't exist. XXXX
  3079. tor_assert(gs != NULL);
  3080. char *old_name = tor_strdup(gs->name);
  3081. guard_selection_type_t old_type = gs->type;
  3082. SMARTLIST_FOREACH(gs->sampled_entry_guards, entry_guard_t *, entry, {
  3083. control_event_guard(entry->nickname, entry->identity, "DROPPED");
  3084. });
  3085. if (gs == curr_guard_context) {
  3086. curr_guard_context = NULL;
  3087. }
  3088. smartlist_remove(guard_contexts, gs);
  3089. guard_selection_free(gs);
  3090. gs = get_guard_selection_by_name(old_name, old_type, 1);
  3091. entry_guards_changed_for_guard_selection(gs);
  3092. tor_free(old_name);
  3093. }
  3094. /** Remove all currently listed entry guards, so new ones will be chosen.
  3095. *
  3096. * XXXX This function shouldn't exist -- it's meant to support the DROPGUARDS
  3097. * command, which is deprecated.
  3098. */
  3099. void
  3100. remove_all_entry_guards(void)
  3101. {
  3102. remove_all_entry_guards_for_guard_selection(get_guard_selection_info());
  3103. }
  3104. /** Helper: pick a directory guard, with whatever algorithm is used. */
  3105. const node_t *
  3106. guards_choose_dirguard(uint8_t dir_purpose,
  3107. circuit_guard_state_t **guard_state_out)
  3108. {
  3109. const node_t *r = NULL;
  3110. entry_guard_restriction_t *rst = NULL;
  3111. /* If we are fetching microdescs, don't query outdated dirservers. */
  3112. if (dir_purpose == DIR_PURPOSE_FETCH_MICRODESC) {
  3113. rst = guard_create_dirserver_md_restriction();
  3114. }
  3115. if (entry_guard_pick_for_circuit(get_guard_selection_info(),
  3116. GUARD_USAGE_DIRGUARD,
  3117. rst,
  3118. &r,
  3119. guard_state_out) < 0) {
  3120. tor_assert(r == NULL);
  3121. }
  3122. return r;
  3123. }
  3124. /**
  3125. * If we're running with a constrained guard set, then maybe mark our guards
  3126. * usable. Return 1 if we do; 0 if we don't.
  3127. */
  3128. int
  3129. guards_retry_optimistic(const or_options_t *options)
  3130. {
  3131. if (! entry_list_is_constrained(options))
  3132. return 0;
  3133. mark_primary_guards_maybe_reachable(get_guard_selection_info());
  3134. return 1;
  3135. }
  3136. /**
  3137. * Return true iff we know enough directory information to construct
  3138. * circuits through all of the primary guards we'd currently use.
  3139. */
  3140. int
  3141. guard_selection_have_enough_dir_info_to_build_circuits(guard_selection_t *gs)
  3142. {
  3143. if (!gs->primary_guards_up_to_date)
  3144. entry_guards_update_primary(gs);
  3145. int n_missing_descriptors = 0;
  3146. int n_considered = 0;
  3147. int num_primary_to_check;
  3148. /* We want to check for the descriptor of at least the first two primary
  3149. * guards in our list, since these are the guards that we typically use for
  3150. * circuits. */
  3151. num_primary_to_check = get_n_primary_guards_to_use(GUARD_USAGE_TRAFFIC);
  3152. num_primary_to_check++;
  3153. SMARTLIST_FOREACH_BEGIN(gs->primary_entry_guards, entry_guard_t *, guard) {
  3154. entry_guard_consider_retry(guard);
  3155. if (guard->is_reachable == GUARD_REACHABLE_NO)
  3156. continue;
  3157. n_considered++;
  3158. if (!guard_has_descriptor(guard))
  3159. n_missing_descriptors++;
  3160. if (n_considered >= num_primary_to_check)
  3161. break;
  3162. } SMARTLIST_FOREACH_END(guard);
  3163. return n_missing_descriptors == 0;
  3164. }
  3165. /** As guard_selection_have_enough_dir_info_to_build_circuits, but uses
  3166. * the default guard selection. */
  3167. int
  3168. entry_guards_have_enough_dir_info_to_build_circuits(void)
  3169. {
  3170. return guard_selection_have_enough_dir_info_to_build_circuits(
  3171. get_guard_selection_info());
  3172. }
  3173. /** Free one guard selection context */
  3174. STATIC void
  3175. guard_selection_free(guard_selection_t *gs)
  3176. {
  3177. if (!gs) return;
  3178. tor_free(gs->name);
  3179. if (gs->sampled_entry_guards) {
  3180. SMARTLIST_FOREACH(gs->sampled_entry_guards, entry_guard_t *, e,
  3181. entry_guard_free(e));
  3182. smartlist_free(gs->sampled_entry_guards);
  3183. gs->sampled_entry_guards = NULL;
  3184. }
  3185. smartlist_free(gs->confirmed_entry_guards);
  3186. smartlist_free(gs->primary_entry_guards);
  3187. tor_free(gs);
  3188. }
  3189. /** Release all storage held by the list of entry guards and related
  3190. * memory structs. */
  3191. void
  3192. entry_guards_free_all(void)
  3193. {
  3194. /* Null out the default */
  3195. curr_guard_context = NULL;
  3196. /* Free all the guard contexts */
  3197. if (guard_contexts != NULL) {
  3198. SMARTLIST_FOREACH_BEGIN(guard_contexts, guard_selection_t *, gs) {
  3199. guard_selection_free(gs);
  3200. } SMARTLIST_FOREACH_END(gs);
  3201. smartlist_free(guard_contexts);
  3202. guard_contexts = NULL;
  3203. }
  3204. circuit_build_times_free_timeouts(get_circuit_build_times_mutable());
  3205. }