diff options
| -rw-r--r-- | changes/bug25870 | 6 | ||||
| -rw-r--r-- | doc/tor.1.txt | 16 | ||||
| -rw-r--r-- | src/or/circuitbuild.c | 109 | ||||
| -rw-r--r-- | src/or/circuitbuild.h | 7 | ||||
| -rw-r--r-- | src/or/entrynodes.c | 11 | ||||
| -rw-r--r-- | src/or/entrynodes.h | 1 | ||||
| -rw-r--r-- | src/test/test_entrynodes.c | 201 |
7 files changed, 307 insertions, 44 deletions
diff --git a/changes/bug25870 b/changes/bug25870 new file mode 100644 index 0000000000..aea5a1e303 --- /dev/null +++ b/changes/bug25870 @@ -0,0 +1,6 @@ + o Minor bugfixes (vanguards): + - Allow the last hop in a vanguard circuit to be the same as our first, + to prevent the adversary from influencing guard node choice by choice + of last hop. Also prevent the creation of A - B - A paths, or A - A + paths, which are forbidden by relays. Fixes bug 25870; bugfix on + 0.3.3.1-alpha. diff --git a/doc/tor.1.txt b/doc/tor.1.txt index 3552dc5014..f42ad0dd3c 100644 --- a/doc/tor.1.txt +++ b/doc/tor.1.txt @@ -1592,6 +1592,14 @@ The following options are useful only for clients (that is, if which means that nodes specified in ExcludeNodes will not be picked. + + When either this option or HSLayer3Nodes are set, the /16 subnet + and node family restrictions are removed for hidden service + circuits. Additionally, we allow the guard node to be present + as the Rend, HSDir, and IP node, and as the hop before it. This + is done to prevent the adversary from inferring information + about our guard, layer2, and layer3 node choices at later points + in the path. + + This option is meant to be managed by a Tor controller such as https://github.com/mikeperry-tor/vanguards that selects and updates this set of nodes for you. Hence it does not do load @@ -1637,6 +1645,14 @@ The following options are useful only for clients (that is, if ExcludeNodes have higher priority than HSLayer3Nodes, which means that nodes specified in ExcludeNodes will not be picked. + + + When either this option or HSLayer2Nodes are set, the /16 subnet + and node family restrictions are removed for hidden service + circuits. Additionally, we allow the guard node to be present + as the Rend, HSDir, and IP node, and as the hop before it. This + is done to prevent the adversary from inferring information + about our guard, layer2, and layer3 node choices at later points + in the path. + This option is meant to be managed by a Tor controller such as https://github.com/mikeperry-tor/vanguards that selects and diff --git a/src/or/circuitbuild.c b/src/or/circuitbuild.c index c6a09f8b7f..6881e0ebb8 100644 --- a/src/or/circuitbuild.c +++ b/src/or/circuitbuild.c @@ -72,10 +72,7 @@ static channel_t * channel_connect_for_circuit(const tor_addr_t *addr, static int circuit_deliver_create_cell(circuit_t *circ, const create_cell_t *create_cell, int relayed); -static int onion_pick_cpath_exit(origin_circuit_t *circ, extend_info_t *exit, - int is_hs_v3_rp_circuit); static crypt_path_t *onion_next_hop_in_cpath(crypt_path_t *cpath); -static int onion_extend_cpath(origin_circuit_t *circ); STATIC int onion_append_hop(crypt_path_t **head_ptr, extend_info_t *choice); static int circuit_send_first_onion_skin(origin_circuit_t *circ); static int circuit_build_no_more_hops(origin_circuit_t *circ); @@ -2283,7 +2280,7 @@ warn_if_last_router_excluded(origin_circuit_t *circ, * be used as an HS v3 rendezvous point. * * Return 0 if ok, -1 if circuit should be closed. */ -static int +STATIC int onion_pick_cpath_exit(origin_circuit_t *circ, extend_info_t *exit_ei, int is_hs_v3_rp_circuit) { @@ -2454,12 +2451,71 @@ cpath_get_n_hops(crypt_path_t **head_ptr) #endif /* defined(TOR_UNIT_TESTS) */ /** + * Build the exclude list for vanguard circuits. + * + * For vanguard circuits we exclude all the already chosen nodes (including the + * exit) from being middle hops to prevent the creation of A - B - A subpaths. + * We also allow the 4th hop to be the same as the guard node so as to not leak + * guard information to RP/IP/HSDirs. + * + * For vanguard circuits, we don't apply any subnet or family restrictions. + * This is to avoid impossible-to-build circuit paths, or just situations where + * our earlier guards prevent us from using most of our later ones. + * + * The alternative is building the circuit in reverse. Reverse calls to + * onion_extend_cpath() (ie: select outer hops first) would then have the + * property that you don't gain information about inner hops by observing + * outer ones. See https://trac.torproject.org/projects/tor/ticket/24487 + * for this. + * + * (Note further that we still exclude the exit to prevent A - B - A + * at the end of the path. */ +static smartlist_t * +build_vanguard_middle_exclude_list(uint8_t purpose, + cpath_build_state_t *state, + crypt_path_t *head, + int cur_len) +{ + smartlist_t *excluded; + const node_t *r; + crypt_path_t *cpath; + int i; + + (void) purpose; + + excluded = smartlist_new(); + + /* Add the exit to the exclude list (note that the exit/last hop is always + * chosen first in circuit_establish_circuit()). */ + if ((r = build_state_get_exit_node(state))) { + smartlist_add(excluded, (node_t*)r); + } + + /* If we are picking the 4th hop, allow that node to be the guard too. + * This prevents us from avoiding the Guard for those hops, which + * gives the adversary information about our guard if they control + * the RP, IP, or HSDIR. We don't do this check based on purpose + * because we also want to allow HS_VANGUARDS pre-build circuits + * to use the guard for that last hop. + */ + if (cur_len == DEFAULT_ROUTE_LEN+1) { + /* Skip the first hop for the exclude list below */ + head = head->next; + cur_len--; + } + + for (i = 0, cpath = head; cpath && i < cur_len; ++i, cpath=cpath->next) { + if ((r = node_get_by_id(cpath->extend_info->identity_digest))) { + smartlist_add(excluded, (node_t*)r); + } + } + + return excluded; +} + +/** * Build a list of nodes to exclude from the choice of this middle * hop, based on already chosen nodes. - * - * XXX: At present, this function does not exclude any nodes from - * the vanguard circuits. See - * https://trac.torproject.org/projects/tor/ticket/24487 */ static smartlist_t * build_middle_exclude_list(uint8_t purpose, @@ -2472,32 +2528,21 @@ build_middle_exclude_list(uint8_t purpose, crypt_path_t *cpath; int i; + /** Vanguard circuits have their own path selection rules */ + if (circuit_should_use_vanguards(purpose)) { + return build_vanguard_middle_exclude_list(purpose, state, head, cur_len); + } + excluded = smartlist_new(); - /* Add the exit to the exclude list (note that the exit/last hop is always - * chosen first in circuit_establish_circuit()). */ + /* For non-vanguard circuits, add the exit and its family to the exclude list + * (note that the exit/last hop is always chosen first in + * circuit_establish_circuit()). */ if ((r = build_state_get_exit_node(state))) { nodelist_add_node_and_family(excluded, r); } - /* XXX: We don't apply any other previously selected node restrictions for - * vanguards, and allow nodes to be reused for those hop positions in the - * same circuit. This is because after many rotations, you get to learn - * inner guard nodes through the nodes that are not selected for outer - * hops. - * - * The alternative is building the circuit in reverse. Reverse calls to - * onion_extend_cpath() (ie: select outer hops first) would then have the - * property that you don't gain information about inner hops by observing - * outer ones. See https://trac.torproject.org/projects/tor/ticket/24487 - * for this. - * - * (Note further that we can and do still exclude the exit in the block - * above, because it is chosen first in circuit_establish_circuit()..) */ - if (circuit_should_use_vanguards(purpose)) { - return excluded; - } - + /* also exclude all other already chosen nodes and their family */ for (i = 0, cpath = head; cpath && i < cur_len; ++i, cpath=cpath->next) { if ((r = node_get_by_id(cpath->extend_info->identity_digest))) { nodelist_add_node_and_family(excluded, r); @@ -2597,7 +2642,9 @@ choose_good_middle_server(uint8_t purpose, /** If a hidden service circuit wants a specific middle node, pin it. */ if (middle_node_must_be_vanguard(options, purpose, cur_len)) { log_debug(LD_GENERAL, "Picking a sticky node (cur_len = %d)", cur_len); - return pick_vanguard_middle_node(options, flags, cur_len, excluded); + choice = pick_vanguard_middle_node(options, flags, cur_len, excluded); + smartlist_free(excluded); + return choice; } choice = router_choose_random_node(excluded, options->ExcludeNodes, flags); @@ -2637,7 +2684,7 @@ choose_good_entry_server(uint8_t purpose, cpath_build_state_t *state, /* This request is for an entry server to use for a regular circuit, * and we use entry guard nodes. Just return one of the guard nodes. */ tor_assert(guard_state_out); - return guards_choose_guard(state, guard_state_out); + return guards_choose_guard(state, purpose, guard_state_out); } excluded = smartlist_new(); @@ -2680,7 +2727,7 @@ onion_next_hop_in_cpath(crypt_path_t *cpath) * Return 1 if the path is complete, 0 if we successfully added a hop, * and -1 on error. */ -static int +STATIC int onion_extend_cpath(origin_circuit_t *circ) { uint8_t purpose = circ->base_.purpose; diff --git a/src/or/circuitbuild.h b/src/or/circuitbuild.h index bea31ad0dd..ae4aef768a 100644 --- a/src/or/circuitbuild.h +++ b/src/or/circuitbuild.h @@ -83,6 +83,13 @@ STATIC circid_t get_unique_circ_id_by_chan(channel_t *chan); STATIC int new_route_len(uint8_t purpose, extend_info_t *exit_ei, smartlist_t *nodes); MOCK_DECL(STATIC int, count_acceptable_nodes, (smartlist_t *nodes)); + +STATIC int onion_extend_cpath(origin_circuit_t *circ); + +STATIC int +onion_pick_cpath_exit(origin_circuit_t *circ, extend_info_t *exit_ei, + int is_hs_v3_rp_circuit); + #if defined(ENABLE_TOR2WEB_MODE) || defined(TOR_UNIT_TESTS) STATIC const node_t *pick_tor2web_rendezvous_node(router_crn_flags_t flags, const or_options_t *options); diff --git a/src/or/entrynodes.c b/src/or/entrynodes.c index bc2afb142a..27d760f1a8 100644 --- a/src/or/entrynodes.c +++ b/src/or/entrynodes.c @@ -118,6 +118,7 @@ #include "circpathbias.h" #include "circuitbuild.h" #include "circuitlist.h" +#include "circuituse.h" #include "circuitstats.h" #include "config.h" #include "confparse.h" @@ -3479,12 +3480,18 @@ guards_update_all(void) used. */ const node_t * guards_choose_guard(cpath_build_state_t *state, - circuit_guard_state_t **guard_state_out) + uint8_t purpose, + circuit_guard_state_t **guard_state_out) { const node_t *r = NULL; const uint8_t *exit_id = NULL; entry_guard_restriction_t *rst = NULL; - if (state && (exit_id = build_state_get_exit_rsa_id(state))) { + + /* Only apply restrictions if we have a specific exit node in mind, and only + * if we are not doing vanguard circuits: we don't want to apply guard + * restrictions to vanguard circuits. */ + if (state && !circuit_should_use_vanguards(purpose) && + (exit_id = build_state_get_exit_rsa_id(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. */ diff --git a/src/or/entrynodes.h b/src/or/entrynodes.h index d562498313..e8c91da41b 100644 --- a/src/or/entrynodes.h +++ b/src/or/entrynodes.h @@ -322,6 +322,7 @@ struct circuit_guard_state_t { /* Common entry points for old and new guard code */ int guards_update_all(void); const node_t *guards_choose_guard(cpath_build_state_t *state, + uint8_t purpose, circuit_guard_state_t **guard_state_out); const node_t *guards_choose_dirguard(uint8_t dir_purpose, circuit_guard_state_t **guard_state_out); diff --git a/src/test/test_entrynodes.c b/src/test/test_entrynodes.c index 6af18f8f4f..cfcb88a66e 100644 --- a/src/test/test_entrynodes.c +++ b/src/test/test_entrynodes.c @@ -4,6 +4,7 @@ #include "orconfig.h" #define CIRCUITLIST_PRIVATE +#define CIRCUITBUILD_PRIVATE #define STATEFILE_PRIVATE #define ENTRYNODES_PRIVATE #define ROUTERLIST_PRIVATE @@ -14,6 +15,7 @@ #include "bridges.h" #include "circuitlist.h" +#include "circuitbuild.h" #include "config.h" #include "confparse.h" #include "crypto_rand.h" @@ -75,6 +77,17 @@ bfn_mock_node_get_by_id(const char *id) return NULL; } +/* Helper function to free a test node. */ +static void +test_node_free(node_t *n) +{ + tor_free(n->rs); + tor_free(n->md->onion_curve25519_pkey); + short_policy_free(n->md->exit_policy); + tor_free(n->md); + tor_free(n); +} + /* Unittest cleanup function: Cleanup the fake network. */ static int big_fake_network_cleanup(const struct testcase_t *testcase, void *ptr) @@ -84,9 +97,7 @@ big_fake_network_cleanup(const struct testcase_t *testcase, void *ptr) if (big_fake_net_nodes) { SMARTLIST_FOREACH(big_fake_net_nodes, node_t *, n, { - tor_free(n->rs); - tor_free(n->md); - tor_free(n); + test_node_free(n); }); smartlist_free(big_fake_net_nodes); } @@ -114,9 +125,18 @@ big_fake_network_setup(const struct testcase_t *testcase) big_fake_net_nodes = smartlist_new(); for (i = 0; i < N_NODES; ++i) { + curve25519_secret_key_t curve25519_secret_key; + node_t *n = tor_malloc_zero(sizeof(node_t)); n->md = tor_malloc_zero(sizeof(microdesc_t)); + /* Generate curve25519 key for this node */ + n->md->onion_curve25519_pkey = + tor_malloc_zero(sizeof(curve25519_public_key_t)); + curve25519_secret_key_generate(&curve25519_secret_key, 0); + curve25519_public_key_generate(n->md->onion_curve25519_pkey, + &curve25519_secret_key); + crypto_rand(n->identity, sizeof(n->identity)); n->rs = tor_malloc_zero(sizeof(routerstatus_t)); @@ -136,8 +156,8 @@ big_fake_network_setup(const struct testcase_t *testcase) { char nickname_binary[8]; crypto_rand(nickname_binary, sizeof(nickname_binary)); - base64_encode(n->rs->nickname, sizeof(n->rs->nickname), - nickname_binary, sizeof(nickname_binary), 0); + base32_encode(n->rs->nickname, sizeof(n->rs->nickname), + nickname_binary, sizeof(nickname_binary)); } /* Call half of the nodes a possible guard. */ @@ -145,6 +165,12 @@ big_fake_network_setup(const struct testcase_t *testcase) n->is_possible_guard = 1; n->rs->guardfraction_percentage = 100; n->rs->has_guardfraction = 1; + n->rs->is_possible_guard = 1; + } + + /* Make some of these nodes a possible exit */ + if (i % 7 == 0) { + n->md->exit_policy = parse_short_policy("accept 443"); } smartlist_add(big_fake_net_nodes, n); @@ -1076,9 +1102,7 @@ test_entry_guard_expand_sample_small_net(void *arg) /* Fun corner case: not enough guards to make up our whole sample size. */ SMARTLIST_FOREACH(big_fake_net_nodes, node_t *, n, { if (n_sl_idx >= 15) { - tor_free(n->rs); - tor_free(n->md); - tor_free(n); + test_node_free(n); SMARTLIST_DEL_CURRENT(big_fake_net_nodes, n); } else { n->rs->addr = 0; // make the filter reject this. @@ -1172,9 +1196,7 @@ test_entry_guard_update_from_consensus_status(void *arg) entry_guard_t *g = smartlist_get(gs->sampled_entry_guards, 5); node_t *n = (node_t*) bfn_mock_node_get_by_id(g->identity); smartlist_remove(big_fake_net_nodes, n); - tor_free(n->rs); - tor_free(n->md); - tor_free(n); + test_node_free(n); } update_approx_time(start + 300); sampled_guards_update_from_consensus(gs); @@ -2805,6 +2827,161 @@ test_entry_guard_outdated_dirserver_exclusion(void *arg) } } +/** Test helper to extend the <b>oc</b> circuit path <b>n</b> times and then + * ensure that the circuit is now complete. */ +static void +helper_extend_circuit_path_n_times(origin_circuit_t *oc, int n) +{ + int retval; + int i; + + /* Extend path n times */ + for (i = 0 ; i < n ; i++) { + retval = onion_extend_cpath(oc); + tt_int_op(retval, OP_EQ, 0); + tt_int_op(circuit_get_cpath_len(oc), OP_EQ, i+1); + } + + /* Now do it one last time and see that circ is complete */ + retval = onion_extend_cpath(oc); + tt_int_op(retval, OP_EQ, 1); + + done: + ; +} + +/** Test for basic Tor path selection. Makes sure we build 3-hop circuits. */ +static void +test_entry_guard_basic_path_selection(void *arg) +{ + (void) arg; + + int retval; + + /* Enable entry guards */ + or_options_t *options = get_options_mutable(); + options->UseEntryGuards = 1; + + /* disables /16 check since all nodes have the same addr... */ + options->EnforceDistinctSubnets = 0; + + /* Create our circuit */ + circuit_t *circ = dummy_origin_circuit_new(30); + origin_circuit_t *oc = TO_ORIGIN_CIRCUIT(circ); + oc->build_state = tor_malloc_zero(sizeof(cpath_build_state_t)); + + /* First pick the exit and pin it on the build_state */ + retval = onion_pick_cpath_exit(oc, NULL, 0); + tt_int_op(retval, OP_EQ, 0); + + /* Extend path 3 times. First we pick guard, then middle, then exit. */ + helper_extend_circuit_path_n_times(oc, 3); + + done: + circuit_free_(circ); +} + +/** Test helper to build an L2 and L3 vanguard list. The vanguard lists + * produced should be completely disjoint. */ +static void +helper_setup_vanguard_list(or_options_t *options) +{ + int i = 0; + + /* Add some nodes to the vanguard L2 list */ + options->HSLayer2Nodes = routerset_new(); + for (i = 0; i < 10 ; i += 2) { + node_t *vanguard_node = smartlist_get(big_fake_net_nodes, i); + tt_assert(vanguard_node->is_possible_guard); + routerset_parse(options->HSLayer2Nodes, vanguard_node->rs->nickname, "l2"); + } + /* also add some nodes to vanguard L3 list + * (L2 list and L3 list should be disjoint for this test to work) */ + options->HSLayer3Nodes = routerset_new(); + for (i = 10; i < 20 ; i += 2) { + node_t *vanguard_node = smartlist_get(big_fake_net_nodes, i); + tt_assert(vanguard_node->is_possible_guard); + routerset_parse(options->HSLayer3Nodes, vanguard_node->rs->nickname, "l3"); + } + + done: + ; +} + +/** Test to ensure that vanguard path selection works properly. Ensures that + * default vanguard circuits are 4 hops, and that path selection works + * correctly given the vanguard settings. */ +static void +test_entry_guard_vanguard_path_selection(void *arg) +{ + (void) arg; + + int retval; + + /* Enable entry guards */ + or_options_t *options = get_options_mutable(); + options->UseEntryGuards = 1; + + /* XXX disables /16 check */ + options->EnforceDistinctSubnets = 0; + + /* Setup our vanguard list */ + helper_setup_vanguard_list(options); + + /* Create our circuit */ + circuit_t *circ = dummy_origin_circuit_new(30); + origin_circuit_t *oc = TO_ORIGIN_CIRCUIT(circ); + oc->build_state = tor_malloc_zero(sizeof(cpath_build_state_t)); + oc->build_state->is_internal = 1; + + /* Switch circuit purpose to vanguards */ + circ->purpose = CIRCUIT_PURPOSE_HS_VANGUARDS; + + /* First pick the exit and pin it on the build_state */ + tt_int_op(oc->build_state->desired_path_len, OP_EQ, 0); + retval = onion_pick_cpath_exit(oc, NULL, 0); + tt_int_op(retval, OP_EQ, 0); + + /* Ensure that vanguards make 4-hop circuits by default */ + tt_int_op(oc->build_state->desired_path_len, OP_EQ, 4); + + /* Extend path as many times as needed to have complete circ. */ + helper_extend_circuit_path_n_times(oc, oc->build_state->desired_path_len); + + /* Test that the cpath linked list is set correctly. */ + crypt_path_t *l1_node = oc->cpath; + crypt_path_t *l2_node = l1_node->next; + crypt_path_t *l3_node = l2_node->next; + crypt_path_t *l4_node = l3_node->next; + crypt_path_t *l1_node_again = l4_node->next; + tt_ptr_op(l1_node, OP_EQ, l1_node_again); + + /* Test that L2 is indeed HSLayer2Node */ + retval = routerset_contains_extendinfo(options->HSLayer2Nodes, + l2_node->extend_info); + tt_int_op(retval, OP_EQ, 4); + /* test that L3 node is _not_ contained in HSLayer2Node */ + retval = routerset_contains_extendinfo(options->HSLayer2Nodes, + l3_node->extend_info); + tt_int_op(retval, OP_LT, 4); + + /* Test that L3 is indeed HSLayer3Node */ + retval = routerset_contains_extendinfo(options->HSLayer3Nodes, + l3_node->extend_info); + tt_int_op(retval, OP_EQ, 4); + /* test that L2 node is _not_ contained in HSLayer3Node */ + retval = routerset_contains_extendinfo(options->HSLayer3Nodes, + l2_node->extend_info); + tt_int_op(retval, OP_LT, 4); + + /* TODO: Test that L1 can be the same as exit. To test this we need start + enforcing EnforceDistinctSubnets again, which means that we need to give + each test node a different address which currently breaks some tests. */ + + done: + circuit_free_(circ); +} + static const struct testcase_setup_t big_fake_network = { big_fake_network_setup, big_fake_network_cleanup }; @@ -2868,6 +3045,8 @@ struct testcase_t entrynodes_tests[] = { BFN_TEST(select_and_cancel), BFN_TEST(drop_guards), BFN_TEST(outdated_dirserver_exclusion), + BFN_TEST(basic_path_selection), + BFN_TEST(vanguard_path_selection), UPGRADE_TEST(upgrade_a_circuit, "c1-done c2-done"), UPGRADE_TEST(upgrade_blocked_by_live_primary_guards, "c1-done c2-done"), |