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Diffstat (limited to 'src/feature/relay/circuitbuild_relay.c')
| -rw-r--r-- | src/feature/relay/circuitbuild_relay.c | 549 |
1 files changed, 549 insertions, 0 deletions
diff --git a/src/feature/relay/circuitbuild_relay.c b/src/feature/relay/circuitbuild_relay.c new file mode 100644 index 0000000000..b89866b477 --- /dev/null +++ b/src/feature/relay/circuitbuild_relay.c @@ -0,0 +1,549 @@ +/* Copyright (c) 2001 Matej Pfajfar. + * Copyright (c) 2001-2004, Roger Dingledine. + * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. + * Copyright (c) 2007-2020, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * @file circuitbuild_relay.c + * @brief Implements the details of exteding circuits (by relaying extend + * cells as create cells, and answering create cells). + * + * On the server side, this module handles the logic of responding to + * RELAY_EXTEND requests, using circuit_extend() and onionskin_answer(). + * + * The shared client and server code is in core/or/circuitbuild.c. + **/ + +#include "orconfig.h" +#include "feature/relay/circuitbuild_relay.h" + +#include "lib/crypt_ops/crypto_rand.h" + +#include "core/or/or.h" +#include "app/config/config.h" + +#include "core/crypto/relay_crypto.h" + +#include "core/or/cell_st.h" +#include "core/or/circuit_st.h" +#include "core/or/extend_info_st.h" +#include "core/or/or_circuit_st.h" + +#include "core/or/channel.h" +#include "core/or/circuitbuild.h" +#include "core/or/circuitlist.h" +#include "core/or/onion.h" +#include "core/or/relay.h" + +#include "feature/nodelist/nodelist.h" + +#include "feature/relay/router.h" +#include "feature/relay/routermode.h" +#include "feature/relay/selftest.h" + +/* Before replying to an extend cell, check the state of the circuit + * <b>circ</b>, and the configured tor mode. + * + * <b>circ</b> must not be NULL. + * + * If the state and mode are valid, return 0. + * Otherwise, if they are invalid, log a protocol warning, and return -1. + */ +STATIC int +circuit_extend_state_valid_helper(const struct circuit_t *circ) +{ + if (!server_mode(get_options())) { + circuitbuild_warn_client_extend(); + return -1; + } + + IF_BUG_ONCE(!circ) { + return -1; + } + + if (circ->n_chan) { + log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, + "n_chan already set. Bug/attack. Closing."); + return -1; + } + + if (circ->n_hop) { + log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, + "conn to next hop already launched. Bug/attack. Closing."); + return -1; + } + + return 0; +} + +/* Make sure the extend cell <b>ec</b> has an ed25519 link specifier. + * + * First, check that the RSA node id is valid. + * If the node id is valid, add the ed25519 link specifier (if required), + * and return 0. + * + * Otherwise, if the node id is invalid, log a protocol warning, + * and return -1.(And do not modify the extend cell.) + * + * Must be called before circuit_extend_lspec_valid_helper(). + */ +STATIC int +circuit_extend_add_ed25519_helper(struct extend_cell_t *ec) +{ + IF_BUG_ONCE(!ec) { + return -1; + } + + /* Check if they asked us for 0000..0000. We support using + * an empty fingerprint for the first hop (e.g. for a bridge relay), + * but we don't want to let clients send us extend cells for empty + * fingerprints -- a) because it opens the user up to a mitm attack, + * and b) because it lets an attacker force the relay to hold open a + * new TLS connection for each extend request. */ + if (tor_digest_is_zero((const char*)ec->node_id)) { + log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, + "Client asked me to extend without specifying an id_digest."); + return -1; + } + + /* Fill in ed_pubkey if it was not provided and we can infer it from + * our networkstatus */ + if (ed25519_public_key_is_zero(&ec->ed_pubkey)) { + const node_t *node = node_get_by_id((const char*)ec->node_id); + const ed25519_public_key_t *node_ed_id = NULL; + if (node && + node_supports_ed25519_link_authentication(node, 1) && + (node_ed_id = node_get_ed25519_id(node))) { + ed25519_pubkey_copy(&ec->ed_pubkey, node_ed_id); + } + } + + return 0; +} + +/* Check if the address and port in the tor_addr_port_t <b>ap</b> are valid, + * and are allowed by the current ExtendAllowPrivateAddresses config. + * + * If they are valid, return true. + * Otherwise, if they are invalid, return false. + * + * If <b>log_zero_addrs</b> is true, log warnings about zero addresses at + * <b>log_level</b>. If <b>log_internal_addrs</b> is true, log warnings about + * internal addresses at <b>log_level</b>. + */ +static bool +circuit_extend_addr_port_is_valid(const struct tor_addr_port_t *ap, + bool log_zero_addrs, bool log_internal_addrs, + int log_level) +{ + /* It's safe to print the family. But we don't want to print the address, + * unless specifically configured to do so. (Zero addresses aren't sensitive, + * But some internal addresses might be.)*/ + + if (!tor_addr_port_is_valid_ap(ap, 0)) { + if (log_zero_addrs) { + log_fn(log_level, LD_PROTOCOL, + "Client asked me to extend to a zero destination port or " + "%s address '%s'.", + fmt_addr_family(&ap->addr), safe_str(fmt_addrport_ap(ap))); + } + return false; + } + + if (tor_addr_is_internal(&ap->addr, 0) && + !get_options()->ExtendAllowPrivateAddresses) { + if (log_internal_addrs) { + log_fn(log_level, LD_PROTOCOL, + "Client asked me to extend to a private %s address '%s'.", + fmt_addr_family(&ap->addr), + safe_str(fmt_and_decorate_addr(&ap->addr))); + } + return false; + } + + return true; +} + +/* Before replying to an extend cell, check the link specifiers in the extend + * cell <b>ec</b>, which was received on the circuit <b>circ</b>. + * + * If they are valid, return 0. + * Otherwise, if they are invalid, log a protocol warning, and return -1. + * + * Must be called after circuit_extend_add_ed25519_helper(). + */ +STATIC int +circuit_extend_lspec_valid_helper(const struct extend_cell_t *ec, + const struct circuit_t *circ) +{ + IF_BUG_ONCE(!ec) { + return -1; + } + + IF_BUG_ONCE(!circ) { + return -1; + } + + /* Check the addresses, without logging */ + const int ipv4_valid = circuit_extend_addr_port_is_valid(&ec->orport_ipv4, + false, false, 0); + const int ipv6_valid = circuit_extend_addr_port_is_valid(&ec->orport_ipv6, + false, false, 0); + /* We need at least one valid address */ + if (!ipv4_valid && !ipv6_valid) { + /* Now, log the invalid addresses at protocol warning level */ + circuit_extend_addr_port_is_valid(&ec->orport_ipv4, + true, true, LOG_PROTOCOL_WARN); + circuit_extend_addr_port_is_valid(&ec->orport_ipv6, + true, true, LOG_PROTOCOL_WARN); + /* And fail */ + return -1; + } else if (!ipv4_valid) { + /* Always log unexpected internal addresses, but go on to use the other + * valid address */ + circuit_extend_addr_port_is_valid(&ec->orport_ipv4, + false, true, LOG_PROTOCOL_WARN); + } else if (!ipv6_valid) { + circuit_extend_addr_port_is_valid(&ec->orport_ipv6, + false, true, LOG_PROTOCOL_WARN); + } + + IF_BUG_ONCE(circ->magic != OR_CIRCUIT_MAGIC) { + return -1; + } + + const channel_t *p_chan = CONST_TO_OR_CIRCUIT(circ)->p_chan; + + IF_BUG_ONCE(!p_chan) { + return -1; + } + + /* Next, check if we're being asked to connect to the hop that the + * extend cell came from. There isn't any reason for that, and it can + * assist circular-path attacks. */ + if (tor_memeq(ec->node_id, p_chan->identity_digest, DIGEST_LEN)) { + log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, + "Client asked me to extend back to the previous hop."); + return -1; + } + + /* Check the previous hop Ed25519 ID too */ + if (! ed25519_public_key_is_zero(&ec->ed_pubkey) && + ed25519_pubkey_eq(&ec->ed_pubkey, &p_chan->ed25519_identity)) { + log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, + "Client asked me to extend back to the previous hop " + "(by Ed25519 ID)."); + return -1; + } + + return 0; +} + +/* If possible, return a supported, non-NULL IP address. + * + * If both addresses are supported and non-NULL, choose one uniformly at + * random. + * + * If we have an IPv6-only extend, but IPv6 is not supported, returns NULL. + * If both addresses are NULL, also returns NULL. */ +STATIC const tor_addr_port_t * +circuit_choose_ip_ap_for_extend(const tor_addr_port_t *ipv4_ap, + const tor_addr_port_t *ipv6_ap) +{ + const bool ipv6_supported = router_can_extend_over_ipv6(get_options()); + + /* If IPv6 is not supported, we can't use the IPv6 address. */ + if (!ipv6_supported) { + ipv6_ap = NULL; + } + + /* If there is no IPv6 address, IPv4 is always supported. + * Until clients include IPv6 ORPorts, and most relays support IPv6, + * this is the most common case. */ + if (!ipv6_ap) { + return ipv4_ap; + } + + /* If there is no IPv4 address, return the (possibly NULL) IPv6 address. */ + if (!ipv4_ap) { + return ipv6_ap; + } + + /* Now we have an IPv4 and an IPv6 address, and IPv6 is supported. + * So make an IPv6 connection at random, with probability 1 in N. + * 1 means "always IPv6 (and no IPv4)" + * 2 means "equal probability of IPv4 or IPv6" + * ... (and so on) ... + * (UINT_MAX - 1) means "almost always IPv4 (and almost never IPv6)" + * To disable IPv6, set ipv6_supported to 0. + */ +#define IPV6_CONNECTION_ONE_IN_N 2 + + bool choose_ipv6 = crypto_fast_rng_one_in_n(get_thread_fast_rng(), + IPV6_CONNECTION_ONE_IN_N); + if (choose_ipv6) { + return ipv6_ap; + } else { + return ipv4_ap; + } +} + +/* When there is no open channel for an extend cell <b>ec</b>, set up the + * circuit <b>circ</b> to wait for a new connection. + * + * If <b>should_launch</b> is true, open a new connection. (Otherwise, we are + * already waiting for a new connection to the same relay.) + * + * Check if IPv6 extends are supported by our current configuration. If they + * are, new connections may be made over IPv4 or IPv6. (IPv4 connections are + * always supported.) + */ +STATIC void +circuit_open_connection_for_extend(const struct extend_cell_t *ec, + struct circuit_t *circ, + int should_launch) +{ + /* We have to check circ first, so we can close it on all other failures */ + IF_BUG_ONCE(!circ) { + /* We can't mark a NULL circuit for close. */ + return; + } + + /* Now we know that circ is not NULL */ + IF_BUG_ONCE(!ec) { + circuit_mark_for_close(circ, END_CIRC_REASON_CONNECTFAILED); + return; + } + + /* Check the addresses, without logging */ + const int ipv4_valid = circuit_extend_addr_port_is_valid(&ec->orport_ipv4, + false, false, 0); + const int ipv6_valid = circuit_extend_addr_port_is_valid(&ec->orport_ipv6, + false, false, 0); + + IF_BUG_ONCE(!ipv4_valid && !ipv6_valid) { + /* circuit_extend_lspec_valid_helper() should have caught this */ + circuit_mark_for_close(circ, END_CIRC_REASON_CONNECTFAILED); + return; + } + + const tor_addr_port_t *chosen_ap = circuit_choose_ip_ap_for_extend( + ipv4_valid ? &ec->orport_ipv4 : NULL, + ipv6_valid ? &ec->orport_ipv6 : NULL); + if (!chosen_ap) { + /* An IPv6-only extend, but IPv6 is not supported */ + log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, + "Received IPv6-only extend, but we don't have an IPv6 ORPort."); + circuit_mark_for_close(circ, END_CIRC_REASON_CONNECTFAILED); + return; + } + + circ->n_hop = extend_info_new(NULL /*nickname*/, + (const char*)ec->node_id, + &ec->ed_pubkey, + NULL, /*onion_key*/ + NULL, /*curve25519_key*/ + &chosen_ap->addr, + chosen_ap->port); + + circ->n_chan_create_cell = tor_memdup(&ec->create_cell, + sizeof(ec->create_cell)); + + circuit_set_state(circ, CIRCUIT_STATE_CHAN_WAIT); + + if (should_launch) { + /* we should try to open a connection */ + channel_t *n_chan = channel_connect_for_circuit( + &circ->n_hop->addr, + circ->n_hop->port, + circ->n_hop->identity_digest, + &circ->n_hop->ed_identity); + if (!n_chan) { + log_info(LD_CIRC,"Launching n_chan failed. Closing circuit."); + circuit_mark_for_close(circ, END_CIRC_REASON_CONNECTFAILED); + return; + } + log_debug(LD_CIRC,"connecting in progress (or finished). Good."); + } +} + +/** Take the 'extend' <b>cell</b>, pull out addr/port plus the onion + * skin and identity digest for the next hop. If we're already connected, + * pass the onion skin to the next hop using a create cell; otherwise + * launch a new OR connection, and <b>circ</b> will notice when the + * connection succeeds or fails. + * + * Return -1 if we want to warn and tear down the circuit, else return 0. + */ +int +circuit_extend(struct cell_t *cell, struct circuit_t *circ) +{ + channel_t *n_chan; + relay_header_t rh; + extend_cell_t ec; + const char *msg = NULL; + int should_launch = 0; + + IF_BUG_ONCE(!cell) { + return -1; + } + + IF_BUG_ONCE(!circ) { + return -1; + } + + if (circuit_extend_state_valid_helper(circ) < 0) + return -1; + + relay_header_unpack(&rh, cell->payload); + + if (extend_cell_parse(&ec, rh.command, + cell->payload+RELAY_HEADER_SIZE, + rh.length) < 0) { + log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, + "Can't parse extend cell. Closing circuit."); + return -1; + } + + if (circuit_extend_add_ed25519_helper(&ec) < 0) + return -1; + + if (circuit_extend_lspec_valid_helper(&ec, circ) < 0) + return -1; + + /* Check the addresses, without logging */ + const int ipv4_valid = circuit_extend_addr_port_is_valid(&ec.orport_ipv4, + false, false, 0); + const int ipv6_valid = circuit_extend_addr_port_is_valid(&ec.orport_ipv6, + false, false, 0); + IF_BUG_ONCE(!ipv4_valid && !ipv6_valid) { + /* circuit_extend_lspec_valid_helper() should have caught this */ + return -1; + } + + n_chan = channel_get_for_extend((const char*)ec.node_id, + &ec.ed_pubkey, + ipv4_valid ? &ec.orport_ipv4.addr : NULL, + ipv6_valid ? &ec.orport_ipv6.addr : NULL, + &msg, + &should_launch); + + if (!n_chan) { + /* We can't use fmt_addr*() twice in the same function call, + * because it uses a static buffer. */ + log_debug(LD_CIRC|LD_OR, "Next router IPv4 (%s): %s.", + fmt_addrport_ap(&ec.orport_ipv4), + msg ? msg : "????"); + log_debug(LD_CIRC|LD_OR, "Next router IPv6 (%s).", + fmt_addrport_ap(&ec.orport_ipv6)); + + circuit_open_connection_for_extend(&ec, circ, should_launch); + + /* return success. The onion/circuit/etc will be taken care of + * automatically (may already have been) whenever n_chan reaches + * OR_CONN_STATE_OPEN. + */ + return 0; + } else { + /* Connection is already established. + * So we need to extend the circuit to the next hop. */ + tor_assert(!circ->n_hop); + circ->n_chan = n_chan; + log_debug(LD_CIRC, + "n_chan is %s.", + channel_get_canonical_remote_descr(n_chan)); + + if (circuit_deliver_create_cell(circ, &ec.create_cell, 1) < 0) + return -1; + + return 0; + } +} + +/** On a relay, accept a create cell, initialise a circuit, and send a + * created cell back. + * + * Given: + * - a response payload consisting of: + * - the <b>created_cell</b> and + * - an optional <b>rend_circ_nonce</b>, and + * - <b>keys</b> of length <b>keys_len</b>, which must be + * CPATH_KEY_MATERIAL_LEN; + * then: + * - initialize the circuit <b>circ</b>'s cryptographic material, + * - set the circuit's state to open, and + * - send a created cell back on that circuit. + * + * If we haven't found our ORPorts reachable yet, and the channel meets the + * necessary conditions, mark the relevant ORPorts as reachable. + * + * Returns -1 if cell or circuit initialisation fails. + */ +int +onionskin_answer(struct or_circuit_t *circ, + const created_cell_t *created_cell, + const char *keys, size_t keys_len, + const uint8_t *rend_circ_nonce) +{ + cell_t cell; + + IF_BUG_ONCE(!circ) { + return -1; + } + + IF_BUG_ONCE(!created_cell) { + return -1; + } + + IF_BUG_ONCE(!keys) { + return -1; + } + + IF_BUG_ONCE(!rend_circ_nonce) { + return -1; + } + + tor_assert(keys_len == CPATH_KEY_MATERIAL_LEN); + + if (created_cell_format(&cell, created_cell) < 0) { + log_warn(LD_BUG,"couldn't format created cell (type=%d, len=%d).", + (int)created_cell->cell_type, (int)created_cell->handshake_len); + return -1; + } + cell.circ_id = circ->p_circ_id; + + circuit_set_state(TO_CIRCUIT(circ), CIRCUIT_STATE_OPEN); + + log_debug(LD_CIRC,"init digest forward 0x%.8x, backward 0x%.8x.", + (unsigned int)get_uint32(keys), + (unsigned int)get_uint32(keys+20)); + if (relay_crypto_init(&circ->crypto, keys, keys_len, 0, 0)<0) { + log_warn(LD_BUG,"Circuit initialization failed."); + return -1; + } + + memcpy(circ->rend_circ_nonce, rend_circ_nonce, DIGEST_LEN); + + int used_create_fast = (created_cell->cell_type == CELL_CREATED_FAST); + + append_cell_to_circuit_queue(TO_CIRCUIT(circ), + circ->p_chan, &cell, CELL_DIRECTION_IN, 0); + log_debug(LD_CIRC,"Finished sending '%s' cell.", + used_create_fast ? "created_fast" : "created"); + + /* Ignore the local bit when ExtendAllowPrivateAddresses is set: + * it violates the assumption that private addresses are local. + * Also, many test networks run on local addresses, and + * TestingTorNetwork sets ExtendAllowPrivateAddresses. */ + if ((!channel_is_local(circ->p_chan) + || get_options()->ExtendAllowPrivateAddresses) + && !channel_is_outgoing(circ->p_chan)) { + /* record that we could process create cells from a non-local conn + * that we didn't initiate; presumably this means that create cells + * can reach us too. */ + router_orport_found_reachable(); + } + + return 0; +} |