commit 5cb2bbea7d7e6bebe797a9d59cd8b98d41b201ba Author: teor teor@torproject.org Date: Wed Mar 18 18:44:42 2020 +1000
relay: Split link specifier checks from circuit_extend()
Part of 33633. --- src/feature/relay/circuitbuild_relay.c | 136 +++++++++++++++++++++------------ 1 file changed, 87 insertions(+), 49 deletions(-)
diff --git a/src/feature/relay/circuitbuild_relay.c b/src/feature/relay/circuitbuild_relay.c index 469fd44b8..2781d1400 100644 --- a/src/feature/relay/circuitbuild_relay.c +++ b/src/feature/relay/circuitbuild_relay.c @@ -67,56 +67,27 @@ circuit_extend_state_valid_helper(const struct circuit_t *circ) return 0; }
-/** 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. +/* Make sure the extend cell <b>ec</b> has an ed25519 link specifier. * - * Return -1 if we want to warn and tear down the circuit, else return 0. + * 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(). */ -int -circuit_extend(struct cell_t *cell, struct circuit_t *circ) +static int +circuit_extend_add_ed25519_helper(extend_cell_t *ec) { - channel_t *n_chan; - relay_header_t rh; - extend_cell_t ec; - const char *msg = NULL; - int should_launch = 0; - - 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 (!ec.orport_ipv4.port || tor_addr_is_null(&ec.orport_ipv4.addr)) { - log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, - "Client asked me to extend to zero destination port or addr."); - return -1; - } - - if (tor_addr_is_internal(&ec.orport_ipv4.addr, 0) && - !get_options()->ExtendAllowPrivateAddresses) { - log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, - "Client asked me to extend to a private address"); - 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)) { + 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; @@ -124,21 +95,49 @@ circuit_extend(struct cell_t *cell, struct circuit_t *circ)
/* 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); + 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); + ed25519_pubkey_copy(&ec->ed_pubkey, node_ed_id); } }
+ return 0; +} + +/* 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 extend_cell_t *ec, + const struct circuit_t *circ) +{ + if (!ec->orport_ipv4.port || tor_addr_is_null(&ec->orport_ipv4.addr)) { + log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, + "Client asked me to extend to zero destination port or addr."); + return -1; + } + + if (tor_addr_is_internal(&ec->orport_ipv4.addr, 0) && + !get_options()->ExtendAllowPrivateAddresses) { + log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, + "Client asked me to extend to a private address"); + 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, - TO_OR_CIRCUIT(circ)->p_chan->identity_digest, + if (tor_memeq(ec->node_id, + CONST_TO_OR_CIRCUIT(circ)->p_chan->identity_digest, DIGEST_LEN)) { log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, "Client asked me to extend back to the previous hop."); @@ -146,15 +145,54 @@ circuit_extend(struct cell_t *cell, struct circuit_t *circ) }
/* Check the previous hop Ed25519 ID too */ - if (! ed25519_public_key_is_zero(&ec.ed_pubkey) && - ed25519_pubkey_eq(&ec.ed_pubkey, - &TO_OR_CIRCUIT(circ)->p_chan->ed25519_identity)) { + if (! ed25519_public_key_is_zero(&ec->ed_pubkey) && + ed25519_pubkey_eq(&ec->ed_pubkey, + &CONST_TO_OR_CIRCUIT(circ)->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; +} + +/** 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 (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; + n_chan = channel_get_for_extend((const char*)ec.node_id, &ec.ed_pubkey, &ec.orport_ipv4.addr,