diff options
Diffstat (limited to 'src/feature/relay/relay_find_addr.c')
| -rw-r--r-- | src/feature/relay/relay_find_addr.c | 239 |
1 files changed, 239 insertions, 0 deletions
diff --git a/src/feature/relay/relay_find_addr.c b/src/feature/relay/relay_find_addr.c new file mode 100644 index 0000000000..c43885af51 --- /dev/null +++ b/src/feature/relay/relay_find_addr.c @@ -0,0 +1,239 @@ +/* Copyright (c) 2001-2020, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * \file relay_find_addr.c + * \brief Implement mechanism for a relay to find its address. + **/ + +#include "core/or/or.h" + +#include "app/config/config.h" +#include "app/config/resolve_addr.h" + +#include "core/mainloop/mainloop.h" +#include "core/or/circuitlist.h" +#include "core/or/circuituse.h" +#include "core/or/extendinfo.h" + +#include "feature/control/control_events.h" +#include "feature/dircommon/dir_connection_st.h" +#include "feature/nodelist/dirlist.h" +#include "feature/nodelist/node_select.h" +#include "feature/nodelist/nodelist.h" +#include "feature/nodelist/routerstatus_st.h" +#include "feature/relay/relay_find_addr.h" +#include "feature/relay/router.h" +#include "feature/relay/routermode.h" + +/** Consider the address suggestion suggested_addr as a possible one to use as + * our address. + * + * This is called when a valid NETINFO cell is received containing a candidate + * for our address or when a directory sends us back the X-Your-Address-Is + * header. + * + * The suggested address is ignored if it does NOT come from a trusted source. + * At the moment, we only look a trusted directory authorities. + * + * The suggested address is ignored if it is internal or it is the same as the + * given peer_addr which is the address from the endpoint that sent the + * NETINFO cell. + * + * The identity_digest is NULL if this is an address suggested by a directory + * since this is a plaintext connection. + * + * The suggested address is set in our suggested address cache if everything + * passes. */ +void +relay_address_new_suggestion(const tor_addr_t *suggested_addr, + const tor_addr_t *peer_addr, + const char *identity_digest) +{ + const or_options_t *options = get_options(); + + tor_assert(suggested_addr); + tor_assert(peer_addr); + + /* Non server should just ignore this suggestion. Clients don't need to + * learn their address let alone cache it. */ + if (!server_mode(options)) { + return; + } + + /* Is the peer a trusted source? Ignore anything coming from non trusted + * source. In this case, we only look at trusted directory authorities. */ + if (!router_addr_is_trusted_dir(peer_addr) || + (identity_digest && !router_digest_is_trusted_dir(identity_digest))) { + return; + } + + /* Ignore a suggestion that is an internal address or the same as the one + * the peer address. */ + if (tor_addr_is_internal(suggested_addr, 0)) { + /* Do not believe anyone who says our address is internal. */ + return; + } + if (tor_addr_eq(suggested_addr, peer_addr)) { + /* Do not believe anyone who says our address is their address. */ + log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, + "A relay endpoint %s is telling us that their address is ours.", + fmt_addr(peer_addr)); + return; + } + + /* Save the suggestion in our cache. */ + resolved_addr_set_suggested(suggested_addr); +} + +/** Find our address to be published in our descriptor. Three places are + * looked at: + * + * 1. Resolved cache. Populated by find_my_address() during the relay + * periodic event that attempts to learn if our address has changed. + * + * 2. If flags is set with RELAY_FIND_ADDR_CACHE_ONLY, only the resolved + * and suggested cache are looked at. No address discovery will be done. + * + * 3. Finally, if all fails, use the suggested address cache which is + * populated by the NETINFO cell content or HTTP header from a + * directory. + * + * The AddressDisableIPv6 is checked here for IPv6 address discovery and if + * set, false is returned and addr_out is UNSPEC. + * + * Before doing any discovery, the configuration is checked for an ORPort of + * the given family. If none can be found, false is returned and addr_out is + * UNSPEC. + * + * Return true on success and addr_out contains the address to use for the + * given family. On failure to find the address, false is returned and + * addr_out is set to an AF_UNSPEC address. */ +MOCK_IMPL(bool, +relay_find_addr_to_publish, (const or_options_t *options, int family, + int flags, tor_addr_t *addr_out)) +{ + tor_assert(options); + tor_assert(addr_out); + + tor_addr_make_unspec(addr_out); + + /* If an IPv6 is requested, check if IPv6 address discovery is disabled on + * this instance. If so, we return a failure. It is done here so we don't + * query the suggested cache that might be populated with an IPv6. */ + if (family == AF_INET6 && options->AddressDisableIPv6) { + return false; + } + + /* There is no point on attempting an address discovery to publish if we + * don't have an ORPort for this family. */ + if (!routerconf_find_or_port(options, family)) { + return false; + } + + /* First, check our resolved address cache. It should contain the address + * we've discovered from the periodic relay event. */ + resolved_addr_get_last(family, addr_out); + if (!tor_addr_is_null(addr_out)) { + goto found; + } + + /* Second, attempt to find our address. The following can do a DNS resolve + * thus only do it when the no cache only flag is flipped. */ + if (!(flags & RELAY_FIND_ADDR_CACHE_ONLY)) { + if (find_my_address(options, family, LOG_INFO, addr_out, NULL, NULL)) { + goto found; + } + } + + /* Third, consider address from our suggestion cache. */ + resolved_addr_get_suggested(family, addr_out); + if (!tor_addr_is_null(addr_out)) { + goto found; + } + + /* No publishable address was found even though we have an ORPort thus + * print a notice log so operator can notice. We'll do that every hour so + * it is not too spammy but enough so operators address the issue. */ + static ratelim_t rlim = RATELIM_INIT(3600); + log_fn_ratelim(&rlim, LOG_NOTICE, LD_CONFIG, + "Unable to find %s address for ORPort %u. " + "You might want to specify %sOnly to it or set an " + "explicit address or set Address.", + fmt_af_family(family), + routerconf_find_or_port(options, family), + (family == AF_INET) ? fmt_af_family(AF_INET6) : + fmt_af_family(AF_INET)); + + /* Not found. */ + return false; + + found: + return true; +} + +/** How often should we launch a circuit to an authority to be sure of getting + * a guess for our IP? */ +#define DUMMY_DOWNLOAD_INTERVAL (20*60) + +void +relay_addr_learn_from_dirauth(void) +{ + static time_t last_dummy_circuit = 0; + const or_options_t *options = get_options(); + time_t now = time(NULL); + bool have_addr; + tor_addr_t addr_out; + + /* This dummy circuit only matter for relays. */ + if (BUG(!server_mode(options))) { + return; + } + + /* Lookup the address cache to learn if we have a good usable address. We + * still force relays to have an IPv4 so that alone is enough to learn if we + * need a lookup. In case we don't have one, we might want to attempt a + * dummy circuit to learn our address as a suggestion from an authority. */ + have_addr = relay_find_addr_to_publish(options, AF_INET, + RELAY_FIND_ADDR_CACHE_ONLY, + &addr_out); + + /* If we're a relay or bridge for which we were unable to discover our + * public address, we rely on learning our address from a directory + * authority from the NETINFO cell. */ + if (!have_addr && last_dummy_circuit + DUMMY_DOWNLOAD_INTERVAL < now) { + last_dummy_circuit = now; + + const routerstatus_t *rs = router_pick_trusteddirserver(V3_DIRINFO, 0); + if (BUG(!rs)) { + /* We should really always have trusted directories configured at this + * stage. They are loaded early either from default list or the one + * given in the configuration file. */ + return; + } + const node_t *node = node_get_by_id(rs->identity_digest); + if (!node) { + /* This can happen if we are still in the early starting stage where no + * descriptors we actually fetched and thus we have the routerstatus_t + * for the authority but not its descriptor which is needed to build a + * circuit and thus learn our address. */ + log_info(LD_GENERAL, "Can't build a circuit to an authority. Unable to " + "learn for now our address from them."); + return; + } + extend_info_t *ei = extend_info_from_node(node, 1); + if (BUG(!ei)) { + return; + } + + log_debug(LD_GENERAL, "Attempting dummy testing circuit to an authority " + "in order to learn our address."); + + /* Launch a one-hop testing circuit to a trusted authority so we can learn + * our address through the NETINFO cell. */ + circuit_launch_by_extend_info(CIRCUIT_PURPOSE_TESTING, ei, + CIRCLAUNCH_IS_INTERNAL | + CIRCLAUNCH_ONEHOP_TUNNEL); + extend_info_free(ei); + } +} |