diff options
Diffstat (limited to 'src/or/circuitbuild.c')
| -rw-r--r-- | src/or/circuitbuild.c | 111 |
1 files changed, 79 insertions, 32 deletions
diff --git a/src/or/circuitbuild.c b/src/or/circuitbuild.c index 24c32b710c..6881e0ebb8 100644 --- a/src/or/circuitbuild.c +++ b/src/or/circuitbuild.c @@ -43,7 +43,7 @@ #include "connection_edge.h" #include "connection_or.h" #include "control.h" -#include "crypto.h" +#include "crypto_rand.h" #include "directory.h" #include "entrynodes.h" #include "hs_ntor.h" @@ -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; |