commit f61e3090fb2975ad8c2a5e138b87c62428c5f46b Author: George Kadianakis <desnacked@riseup.net> Date: Mon Nov 6 19:38:47 2017 +0200 Introduce new guard restriction and use it to skip outdated dirs. --- changes/bug23817 | 3 ++ src/or/directory.c | 4 +-- src/or/entrynodes.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++------- src/or/entrynodes.h | 37 +++++++++++++++------ 4 files changed, 116 insertions(+), 23 deletions(-) diff --git a/changes/bug23817 b/changes/bug23817 new file mode 100644 index 000000000..474094279 --- /dev/null +++ b/changes/bug23817 @@ -0,0 +1,3 @@ + o Minor bugfixes (descriptors): + - Don't try fetching microdescriptors from relays that have failed to + deliver them in the past. Fixes bug 23817; bugfix on 0.3.0.1-alpha. diff --git a/src/or/directory.c b/src/or/directory.c index 129309ae4..aec8ef5bf 100644 --- a/src/or/directory.c +++ b/src/or/directory.c @@ -464,7 +464,7 @@ directory_pick_generic_dirserver(dirinfo_type_t type, int pds_flags, log_warn(LD_BUG, "Called when we have UseBridges set."); if (should_use_directory_guards(options)) { - const node_t *node = guards_choose_dirguard(guard_state_out); + const node_t *node = guards_choose_dirguard(dir_purpose, guard_state_out); if (node) rs = node->rs; } else { @@ -598,7 +598,7 @@ directory_get_from_dirserver,( * sort of dir fetch we'll be doing, so it won't return a bridge * that can't answer our question. */ - const node_t *node = guards_choose_dirguard(&guard_state); + const node_t *node = guards_choose_dirguard(dir_purpose, &guard_state); if (node && node->ri) { /* every bridge has a routerinfo. */ routerinfo_t *ri = node->ri; diff --git a/src/or/entrynodes.c b/src/or/entrynodes.c index 26f53cbfe..f2ca7aac2 100644 --- a/src/or/entrynodes.c +++ b/src/or/entrynodes.c @@ -1460,6 +1460,70 @@ guard_in_node_family(const entry_guard_t *guard, const node_t *node) } } +/* Allocate and return a new exit guard restriction (where <b>exit_id</b> is of + * size DIGEST_LEN) */ +STATIC entry_guard_restriction_t * +guard_create_exit_restriction(const uint8_t *exit_id) +{ + entry_guard_restriction_t *rst = NULL; + rst = tor_malloc_zero(sizeof(entry_guard_restriction_t)); + rst->type = RST_EXIT_NODE; + memcpy(rst->exclude_id, exit_id, DIGEST_LEN); + return rst; +} + +/** Allocate and return an outdated md guard restriction. */ +STATIC entry_guard_restriction_t * +guard_create_dirserver_md_restriction(void) +{ + entry_guard_restriction_t *rst = NULL; + + rst = tor_malloc_zero(sizeof(entry_guard_restriction_t)); + rst->type = RST_OUTDATED_MD_DIRSERVER; + + return rst; +} + +/* Return True if <b>guard</b> obeys the exit restriction <b>rst</b>. */ +static int +guard_obeys_exit_restriction(const entry_guard_t *guard, + const entry_guard_restriction_t *rst) +{ + tor_assert(rst->type == RST_EXIT_NODE); + + // Exclude the exit ID and all of its family. + const node_t *node = node_get_by_id((const char*)rst->exclude_id); + if (node && guard_in_node_family(guard, node)) + return 0; + + return tor_memneq(guard->identity, rst->exclude_id, DIGEST_LEN); +} + +/** Return True if <b>guard</b> should be used as a dirserver for fetching + * microdescriptors. */ +static int +guard_obeys_md_dirserver_restriction(const entry_guard_t *guard) +{ + /* Don't enforce dirserver restrictions for bridges since we might not have + * many of those. Be willing to try them over and over again for now. */ + /* XXX: Improvement might be possible here */ + if (guard->bridge_addr) { + return 1; + } + + /* If this guard is an outdated dirserver, don't use it. */ + if (microdesc_relay_is_outdated_dirserver(guard->identity)) { + log_info(LD_GENERAL, "Skipping %s dirserver: outdated", + hex_str(guard->identity, DIGEST_LEN)); + return 0; + } + + log_debug(LD_GENERAL, "%s dirserver obeys md restrictions", + hex_str(guard->identity, DIGEST_LEN)); + + return 1; +} + /** * Return true iff <b>guard</b> obeys the restrictions defined in <b>rst</b>. * (If <b>rst</b> is NULL, there are no restrictions.) @@ -1472,13 +1536,14 @@ entry_guard_obeys_restriction(const entry_guard_t *guard, if (! rst) return 1; // No restriction? No problem. - // Only one kind of restriction exists right now: excluding an exit - // ID and all of its family. - const node_t *node = node_get_by_id((const char*)rst->exclude_id); - if (node && guard_in_node_family(guard, node)) - return 0; + if (rst->type == RST_EXIT_NODE) { + return guard_obeys_exit_restriction(guard, rst); + } else if (rst->type == RST_OUTDATED_MD_DIRSERVER) { + return guard_obeys_md_dirserver_restriction(guard); + } - return tor_memneq(guard->identity, rst->exclude_id, DIGEST_LEN); + tor_assert_nonfatal_unreached(); + return 0; } /** @@ -2105,7 +2170,7 @@ entry_guard_has_higher_priority(entry_guard_t *a, entry_guard_t *b) } /** Release all storage held in <b>restriction</b> */ -static void +STATIC void entry_guard_restriction_free(entry_guard_restriction_t *rst) { tor_free(rst); @@ -3358,8 +3423,8 @@ guards_choose_guard(cpath_build_state_t *state, /* We're building to a targeted exit node, so that node can't be * chosen as our guard for this circuit. Remember that fact in a * restriction. */ - rst = tor_malloc_zero(sizeof(entry_guard_restriction_t)); - memcpy(rst->exclude_id, exit_id, DIGEST_LEN); + rst = guard_create_exit_restriction(exit_id); + tor_assert(rst); } if (entry_guard_pick_for_circuit(get_guard_selection_info(), GUARD_USAGE_TRAFFIC, @@ -3411,12 +3476,20 @@ remove_all_entry_guards(void) /** Helper: pick a directory guard, with whatever algorithm is used. */ const node_t * -guards_choose_dirguard(circuit_guard_state_t **guard_state_out) +guards_choose_dirguard(uint8_t dir_purpose, + circuit_guard_state_t **guard_state_out) { const node_t *r = NULL; + entry_guard_restriction_t *rst = NULL; + + /* If we are fetching microdescs, don't query outdated dirservers. */ + if (dir_purpose == DIR_PURPOSE_FETCH_MICRODESC) { + rst = guard_create_dirserver_md_restriction(); + } + if (entry_guard_pick_for_circuit(get_guard_selection_info(), GUARD_USAGE_DIRGUARD, - NULL, + rst, &r, guard_state_out) < 0) { tor_assert(r == NULL); diff --git a/src/or/entrynodes.h b/src/or/entrynodes.h index 735c7738b..29de627de 100644 --- a/src/or/entrynodes.h +++ b/src/or/entrynodes.h @@ -272,22 +272,28 @@ struct guard_selection_s { struct entry_guard_handle_t; +/** Types of restrictions we impose when picking guard nodes */ +typedef enum guard_restriction_type_t { + /* Don't pick the same guard node as our exit node (or its family) */ + RST_EXIT_NODE = 0, + /* Don't pick dirguards that have previously shown to be outdated */ + RST_OUTDATED_MD_DIRSERVER = 1 +} guard_restriction_type_t; + /** * A restriction to remember which entry guards are off-limits for a given * circuit. * - * Right now, we only use restrictions to block a single guard and its family - * from being selected; this mechanism is designed to be more extensible in - * the future, however. - * * Note: This mechanism is NOT for recording which guards are never to be * used: only which guards cannot be used on <em>one particular circuit</em>. */ struct entry_guard_restriction_t { - /** - * The guard's RSA identity digest must not equal this; and it must not - * be in the same family as any node with this digest. - */ + /* What type of restriction are we imposing? */ + guard_restriction_type_t type; + + /* In case of restriction type RST_EXIT_NODE, the guard's RSA identity + * digest must not equal this; and it must not be in the same family as any + * node with this digest. */ uint8_t exclude_id[DIGEST_LEN]; }; @@ -316,7 +322,8 @@ struct circuit_guard_state_t { int guards_update_all(void); const node_t *guards_choose_guard(cpath_build_state_t *state, circuit_guard_state_t **guard_state_out); -const node_t *guards_choose_dirguard(circuit_guard_state_t **guard_state_out); +const node_t *guards_choose_dirguard(uint8_t dir_purpose, + circuit_guard_state_t **guard_state_out); #if 1 /* XXXX NM I would prefer that all of this stuff be private to @@ -550,7 +557,17 @@ STATIC unsigned entry_guards_note_guard_success(guard_selection_t *gs, unsigned old_state); STATIC int entry_guard_has_higher_priority(entry_guard_t *a, entry_guard_t *b); STATIC char *getinfo_helper_format_single_entry_guard(const entry_guard_t *e); -#endif + +STATIC entry_guard_restriction_t * +guard_create_exit_restriction(const uint8_t *exit_id); + +STATIC entry_guard_restriction_t * +guard_create_dirserver_md_restriction(void); + +STATIC void +entry_guard_restriction_free(entry_guard_restriction_t *rst); + +#endif /* defined(ENTRYNODES_PRIVATE) */ void remove_all_entry_guards_for_guard_selection(guard_selection_t *gs); void remove_all_entry_guards(void);