diff options
Diffstat (limited to 'src/or/circuitbuild.c')
| -rw-r--r-- | src/or/circuitbuild.c | 297 |
1 files changed, 211 insertions, 86 deletions
diff --git a/src/or/circuitbuild.c b/src/or/circuitbuild.c index 14d40150db..0881f231aa 100644 --- a/src/or/circuitbuild.c +++ b/src/or/circuitbuild.c @@ -9,6 +9,20 @@ * * \brief Implements the details of building circuits (by chosing paths, * constructing/sending create/extend cells, and so on). + * + * On the client side, this module handles launching circuits. Circuit + * launches are srtarted from circuit_establish_circuit(), called from + * circuit_launch_by_extend_info()). To choose the path the circuit will + * take, onion_extend_cpath() calls into a maze of node selection functions. + * + * Once the circuit is ready to be launched, the first hop is treated as a + * special case with circuit_handle_first_hop(), since it might need to open a + * channel. As the channel opens, and later as CREATED and RELAY_EXTENDED + * cells arrive, the client will invoke circuit_send_next_onion_skin() to send + * CREATE or RELAY_EXTEND cells. + * + * On the server side, this module also handles the logic of responding to + * RELAY_EXTEND requests, using circuit_extend(). **/ #define CIRCUITBUILD_PRIVATE @@ -28,6 +42,7 @@ #include "connection_edge.h" #include "connection_or.h" #include "control.h" +#include "crypto.h" #include "directory.h" #include "entrynodes.h" #include "main.h" @@ -38,14 +53,14 @@ #include "onion_tap.h" #include "onion_fast.h" #include "policies.h" -#include "transports.h" #include "relay.h" +#include "rendcommon.h" #include "rephist.h" #include "router.h" #include "routerlist.h" #include "routerparse.h" #include "routerset.h" -#include "crypto.h" +#include "transports.h" static channel_t * channel_connect_for_circuit(const tor_addr_t *addr, uint16_t port, @@ -58,7 +73,6 @@ static crypt_path_t *onion_next_hop_in_cpath(crypt_path_t *cpath); static int onion_extend_cpath(origin_circuit_t *circ); static int count_acceptable_nodes(smartlist_t *routers); static int onion_append_hop(crypt_path_t **head_ptr, extend_info_t *choice); -static int circuits_can_use_ntor(void); /** This function tries to get a channel to the specified endpoint, * and then calls command_setup_channel() to give it the right @@ -70,7 +84,9 @@ channel_connect_for_circuit(const tor_addr_t *addr, uint16_t port, { channel_t *chan; - chan = channel_connect(addr, port, id_digest); + chan = channel_connect(addr, port, id_digest, + NULL // XXXX Ed25519 id. + ); if (chan) command_setup_channel(chan); return chan; @@ -365,7 +381,7 @@ circuit_rep_hist_note_result(origin_circuit_t *circ) } while (hop!=circ->cpath); } -/** Return 1 iff at least one node in circ's cpath supports ntor. */ +/** Return 1 iff every node in circ's cpath definitely supports ntor. */ static int circuit_cpath_supports_ntor(const origin_circuit_t *circ) { @@ -373,16 +389,19 @@ circuit_cpath_supports_ntor(const origin_circuit_t *circ) cpath = head = circ->cpath; do { - if (cpath->extend_info && - !tor_mem_is_zero( - (const char*)cpath->extend_info->curve25519_onion_key.public_key, - CURVE25519_PUBKEY_LEN)) - return 1; + /* if the extend_info is missing, we can't tell if it supports ntor */ + if (!cpath->extend_info) { + return 0; + } + /* if the key is blank, it definitely doesn't support ntor */ + if (!extend_info_supports_ntor(cpath->extend_info)) { + return 0; + } cpath = cpath->next; } while (cpath != head); - return 0; + return 1; } /** Pick all the entries in our cpath. Stop and return 0 when we're @@ -390,41 +409,61 @@ circuit_cpath_supports_ntor(const origin_circuit_t *circ) static int onion_populate_cpath(origin_circuit_t *circ) { - int n_tries = 0; - const int using_ntor = circuits_can_use_ntor(); + int r = 0; -#define MAX_POPULATE_ATTEMPTS 32 + /* onion_extend_cpath assumes these are non-NULL */ + tor_assert(circ); + tor_assert(circ->build_state); - while (1) { - int r = onion_extend_cpath(circ); + while (r == 0) { + r = onion_extend_cpath(circ); if (r < 0) { log_info(LD_CIRC,"Generating cpath hop failed."); return -1; } - if (r == 1) { - /* This circuit doesn't need/shouldn't be forced to have an ntor hop */ - if (circ->build_state->desired_path_len <= 1 || ! using_ntor) - return 0; + } - /* This circuit has an ntor hop. great! */ - if (circuit_cpath_supports_ntor(circ)) - return 0; + /* The path is complete */ + tor_assert(r == 1); - /* No node in the circuit supports ntor. Have we already tried too many - * times? */ - if (++n_tries >= MAX_POPULATE_ATTEMPTS) - break; + /* Does every node in this path support ntor? */ + int path_supports_ntor = circuit_cpath_supports_ntor(circ); - /* Clear the path and retry */ - circuit_clear_cpath(circ); + /* We would like every path to support ntor, but we have to allow for some + * edge cases. */ + tor_assert(circuit_get_cpath_len(circ)); + if (circuit_can_use_tap(circ)) { + /* Circuits from clients to intro points, and hidden services to + * rend points do not support ntor, because the hidden service protocol + * does not include ntor onion keys. This is also true for Tor2web clients + * and Single Onion Services. */ + return 0; + } + + if (circuit_get_cpath_len(circ) == 1) { + /* Allow for bootstrapping: when we're fetching directly from a fallback, + * authority, or bridge, we have no way of knowing its ntor onion key + * before we connect to it. So instead, we try connecting, and end up using + * CREATE_FAST. */ + tor_assert(circ->cpath); + tor_assert(circ->cpath->extend_info); + const node_t *node = node_get_by_id( + circ->cpath->extend_info->identity_digest); + /* If we don't know the node and its descriptor, we must be bootstrapping. + */ + if (!node || !node_has_descriptor(node)) { + return 0; } } - log_warn(LD_CIRC, "I tried for %d times, but I couldn't build a %d-hop " - "circuit with at least one node that supports ntor.", - MAX_POPULATE_ATTEMPTS, - circ->build_state->desired_path_len); - return -1; + if (BUG(!path_supports_ntor)) { + /* If we're building a multi-hop path, and it's not one of the HS or + * bootstrapping exceptions, and it doesn't support ntor, something has + * gone wrong. */ + return -1; + } + + return 0; } /** Create and return a new origin circuit. Initialize its purpose and @@ -757,10 +796,13 @@ should_use_create_fast_for_circuit(origin_circuit_t *circ) tor_assert(circ->cpath); tor_assert(circ->cpath->extend_info); - if (!circ->cpath->extend_info->onion_key) - return 1; /* our hand is forced: only a create_fast will work. */ + if (!circuit_has_usable_onion_key(circ)) { + /* We don't have ntor, and we don't have or can't use TAP, + * so our hand is forced: only a create_fast will work. */ + return 1; + } if (public_server_mode(options)) { - /* We're a server, and we know an onion key. We can choose. + /* We're a server, and we have a usable onion key. We can choose. * Prefer to blend our circuit into the other circuits we are * creating on behalf of others. */ return 0; @@ -785,62 +827,56 @@ circuit_timeout_want_to_count_circ(origin_circuit_t *circ) && circ->build_state->desired_path_len == DEFAULT_ROUTE_LEN; } -/** Return true if the ntor handshake is enabled in the configuration, or if - * it's been set to "auto" in the configuration and it's enabled in the - * consensus. */ -static int -circuits_can_use_ntor(void) -{ - const or_options_t *options = get_options(); - if (options->UseNTorHandshake != -1) - return options->UseNTorHandshake; - return networkstatus_get_param(NULL, "UseNTorHandshake", 0, 0, 1); -} - /** Decide whether to use a TAP or ntor handshake for connecting to <b>ei</b> * directly, and set *<b>cell_type_out</b> and *<b>handshake_type_out</b> - * accordingly. */ + * accordingly. + * Note that TAP handshakes in CREATE cells are only used for direct + * connections: + * - from Tor2web to intro points not in the client's consensus, and + * - from Single Onions to rend points not in the service's consensus. + * This is checked in onion_populate_cpath. */ static void circuit_pick_create_handshake(uint8_t *cell_type_out, uint16_t *handshake_type_out, const extend_info_t *ei) { - /* XXXX029 Remove support for deciding to use TAP. */ - if (!tor_mem_is_zero((const char*)ei->curve25519_onion_key.public_key, - CURVE25519_PUBKEY_LEN) && - circuits_can_use_ntor()) { + /* torspec says: In general, clients SHOULD use CREATE whenever they are + * using the TAP handshake, and CREATE2 otherwise. */ + if (extend_info_supports_ntor(ei)) { *cell_type_out = CELL_CREATE2; *handshake_type_out = ONION_HANDSHAKE_TYPE_NTOR; - return; + } else { + /* XXXX030 Remove support for deciding to use TAP and EXTEND. */ + *cell_type_out = CELL_CREATE; + *handshake_type_out = ONION_HANDSHAKE_TYPE_TAP; } - - *cell_type_out = CELL_CREATE; - *handshake_type_out = ONION_HANDSHAKE_TYPE_TAP; } -/** Decide whether to use a TAP or ntor handshake for connecting to <b>ei</b> - * directly, and set *<b>handshake_type_out</b> accordingly. Decide whether, - * in extending through <b>node</b> to do so, we should use an EXTEND2 or an - * EXTEND cell to do so, and set *<b>cell_type_out</b> and - * *<b>create_cell_type_out</b> accordingly. */ +/** Decide whether to use a TAP or ntor handshake for extending to <b>ei</b> + * and set *<b>handshake_type_out</b> accordingly. Decide whether we should + * use an EXTEND2 or an EXTEND cell to do so, and set *<b>cell_type_out</b> + * and *<b>create_cell_type_out</b> accordingly. + * Note that TAP handshakes in EXTEND cells are only used: + * - from clients to intro points, and + * - from hidden services to rend points. + * This is checked in onion_populate_cpath. + */ static void circuit_pick_extend_handshake(uint8_t *cell_type_out, uint8_t *create_cell_type_out, uint16_t *handshake_type_out, - const node_t *node_prev, const extend_info_t *ei) { uint8_t t; circuit_pick_create_handshake(&t, handshake_type_out, ei); - /* XXXX029 Remove support for deciding to use TAP. */ - if (node_prev && - *handshake_type_out != ONION_HANDSHAKE_TYPE_TAP && - (node_has_curve25519_onion_key(node_prev) || - (node_prev->rs && node_prev->rs->version_supports_extend2_cells))) { + /* torspec says: Clients SHOULD use the EXTEND format whenever sending a TAP + * handshake... In other cases, clients SHOULD use EXTEND2. */ + if (*handshake_type_out != ONION_HANDSHAKE_TYPE_TAP) { *cell_type_out = RELAY_COMMAND_EXTEND2; *create_cell_type_out = CELL_CREATE2; } else { + /* XXXX030 Remove support for deciding to use TAP and EXTEND. */ *cell_type_out = RELAY_COMMAND_EXTEND; *create_cell_type_out = CELL_CREATE; } @@ -996,15 +1032,10 @@ circuit_send_next_onion_skin(origin_circuit_t *circ) return - END_CIRC_REASON_INTERNAL; } - { - const node_t *prev_node; - prev_node = node_get_by_id(hop->prev->extend_info->identity_digest); - circuit_pick_extend_handshake(&ec.cell_type, - &ec.create_cell.cell_type, - &ec.create_cell.handshake_type, - prev_node, - hop->extend_info); - } + circuit_pick_extend_handshake(&ec.cell_type, + &ec.create_cell.cell_type, + &ec.create_cell.handshake_type, + hop->extend_info); tor_addr_copy(&ec.orport_ipv4.addr, &hop->extend_info->addr); ec.orport_ipv4.port = hop->extend_info->port; @@ -1826,13 +1857,32 @@ pick_rendezvous_node(router_crn_flags_t flags) flags |= CRN_ALLOW_INVALID; #ifdef ENABLE_TOR2WEB_MODE + /* We want to connect directly to the node if we can */ + router_crn_flags_t direct_flags = flags; + direct_flags |= CRN_PREF_ADDR; + direct_flags |= CRN_DIRECT_CONN; + /* The user wants us to pick specific RPs. */ if (options->Tor2webRendezvousPoints) { - const node_t *tor2web_rp = pick_tor2web_rendezvous_node(flags, options); + const node_t *tor2web_rp = pick_tor2web_rendezvous_node(direct_flags, + options); if (tor2web_rp) { return tor2web_rp; } - /* Else, if no tor2web RP was found, fall back to choosing a random node */ + } + + /* Else, if no direct, preferred tor2web RP was found, fall back to choosing + * a random direct node */ + const node_t *node = router_choose_random_node(NULL, options->ExcludeNodes, + direct_flags); + /* Return the direct node (if found), or log a message and fall back to an + * indirect connection. */ + if (node) { + return node; + } else { + log_info(LD_REND, + "Unable to find a random rendezvous point that is reachable via " + "a direct connection, falling back to a 3-hop path."); } #endif @@ -1967,7 +2017,9 @@ onion_pick_cpath_exit(origin_circuit_t *circ, extend_info_t *exit_ei) cpath_build_state_t *state = circ->build_state; if (state->onehop_tunnel) { - log_debug(LD_CIRC, "Launching a one-hop circuit for dir tunnel."); + log_debug(LD_CIRC, "Launching a one-hop circuit for dir tunnel%s.", + (rend_allow_non_anonymous_connection(get_options()) ? + ", or intro or rendezvous connection" : "")); state->desired_path_len = 1; } else { int r = new_route_len(circ->base_.purpose, exit_ei, nodelist_get_list()); @@ -2058,15 +2110,18 @@ count_acceptable_nodes(smartlist_t *nodes) if (! node->is_running) // log_debug(LD_CIRC,"Nope, the directory says %d is not running.",i); continue; + /* XXX This clause makes us count incorrectly: if AllowInvalidRouters + * allows this node in some places, then we're getting an inaccurate + * count. For now, be conservative and don't count it. But later we + * should try to be smarter. */ if (! node->is_valid) // log_debug(LD_CIRC,"Nope, the directory says %d is not valid.",i); continue; if (! node_has_descriptor(node)) continue; - /* XXX This clause makes us count incorrectly: if AllowInvalidRouters - * allows this node in some places, then we're getting an inaccurate - * count. For now, be conservative and don't count it. But later we - * should try to be smarter. */ + /* The node has a descriptor, so we can just check the ntor key directly */ + if (!node_has_curve25519_onion_key(node)) + continue; ++num; } SMARTLIST_FOREACH_END(node); @@ -2177,7 +2232,6 @@ choose_good_entry_server(uint8_t purpose, cpath_build_state_t *state) * This is an incomplete fix, but is no worse than the previous behaviour, * and only applies to minimal, testing tor networks * (so it's no less secure) */ - /*XXXX++ use the using_as_guard flag to accomplish this.*/ if (options->UseEntryGuards && (!options->TestingTorNetwork || smartlist_len(nodelist_get_list()) > smartlist_len(get_entry_guards()) @@ -2356,6 +2410,14 @@ extend_info_from_node(const node_t *node, int for_direct_connect) log_warn(LD_CIRC, "Could not choose valid address for %s", node->ri ? node->ri->nickname : node->rs->nickname); + /* Every node we connect or extend to must support ntor */ + if (!node_has_curve25519_onion_key(node)) { + log_fn(LOG_PROTOCOL_WARN, LD_CIRC, + "Attempted to create extend_info for a node that does not support " + "ntor: %s", node_describe(node)); + return NULL; + } + if (valid_addr && node->ri) return extend_info_new(node->ri->nickname, node->identity, @@ -2441,3 +2503,66 @@ extend_info_addr_is_allowed(const tor_addr_t *addr) return 0; } +/* Does ei have a valid TAP key? */ +int +extend_info_supports_tap(const extend_info_t* ei) +{ + tor_assert(ei); + /* Valid TAP keys are not NULL */ + return ei->onion_key != NULL; +} + +/* Does ei have a valid ntor key? */ +int +extend_info_supports_ntor(const extend_info_t* ei) +{ + tor_assert(ei); + /* Valid ntor keys have at least one non-zero byte */ + return !tor_mem_is_zero( + (const char*)ei->curve25519_onion_key.public_key, + CURVE25519_PUBKEY_LEN); +} + +/* Is circuit purpose allowed to use the deprecated TAP encryption protocol? + * The hidden service protocol still uses TAP for some connections, because + * ntor onion keys aren't included in HS descriptors or INTRODUCE cells. */ +static int +circuit_purpose_can_use_tap_impl(uint8_t purpose) +{ + return (purpose == CIRCUIT_PURPOSE_S_CONNECT_REND || + purpose == CIRCUIT_PURPOSE_C_INTRODUCING); +} + +/* Is circ allowed to use the deprecated TAP encryption protocol? + * The hidden service protocol still uses TAP for some connections, because + * ntor onion keys aren't included in HS descriptors or INTRODUCE cells. */ +int +circuit_can_use_tap(const origin_circuit_t *circ) +{ + tor_assert(circ); + tor_assert(circ->cpath); + tor_assert(circ->cpath->extend_info); + return (circuit_purpose_can_use_tap_impl(circ->base_.purpose) && + extend_info_supports_tap(circ->cpath->extend_info)); +} + +/* Does circ have an onion key which it's allowed to use? */ +int +circuit_has_usable_onion_key(const origin_circuit_t *circ) +{ + tor_assert(circ); + tor_assert(circ->cpath); + tor_assert(circ->cpath->extend_info); + return (extend_info_supports_ntor(circ->cpath->extend_info) || + circuit_can_use_tap(circ)); +} + +/* Does ei have an onion key which it would prefer to use? + * Currently, we prefer ntor keys*/ +int +extend_info_has_preferred_onion_key(const extend_info_t* ei) +{ + tor_assert(ei); + return extend_info_supports_ntor(ei); +} + |