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5f733ccd73
tor/src/or/circuitbuild.c
Mike Perry 5f733ccd73 Fix some hidden service edge cases.
2012-12-08 12:07:58 -08:00

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/* Copyright (c) 2001 Matej Pfajfar.
* Copyright (c) 2001-2004, Roger Dingledine.
* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
* Copyright (c) 2007-2012, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* \file circuitbuild.c
* \brief The actual details of building circuits.
**/
#include "or.h"
#include "channel.h"
#include "circuitbuild.h"
#include "circuitlist.h"
#include "circuitstats.h"
#include "circuituse.h"
#include "command.h"
#include "config.h"
#include "confparse.h"
#include "connection.h"
#include "connection_edge.h"
#include "connection_or.h"
#include "control.h"
#include "directory.h"
#include "entrynodes.h"
#include "main.h"
#include "networkstatus.h"
#include "nodelist.h"
#include "onion.h"
#include "policies.h"
#include "transports.h"
#include "relay.h"
#include "rephist.h"
#include "router.h"
#include "routerlist.h"
#include "routerparse.h"
#include "routerset.h"
#include "crypto.h"
#ifndef MIN
#define MIN(a,b) ((a)<(b)?(a):(b))
#endif
/********* START VARIABLES **********/
/** A global list of all circuits at this hop. */
extern circuit_t *global_circuitlist;
/********* END VARIABLES ************/
static channel_t * channel_connect_for_circuit(const tor_addr_t *addr,
uint16_t port,
const char *id_digest);
static int circuit_deliver_create_cell(circuit_t *circ,
uint8_t cell_type, const char *payload);
static int onion_pick_cpath_exit(origin_circuit_t *circ, extend_info_t *exit);
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 entry_guard_inc_first_hop_count(entry_guard_t *guard);
static void pathbias_count_build_success(origin_circuit_t *circ);
static void pathbias_count_successful_close(origin_circuit_t *circ);
static void pathbias_count_collapse(origin_circuit_t *circ);
static void pathbias_count_unusable(origin_circuit_t *circ);
/** This function tries to get a channel to the specified endpoint,
* and then calls command_setup_channel() to give it the right
* callbacks.
*/
static channel_t *
channel_connect_for_circuit(const tor_addr_t *addr, uint16_t port,
const char *id_digest)
{
channel_t *chan;
chan = channel_connect(addr, port, id_digest);
if (chan) command_setup_channel(chan);
return chan;
}
/** Iterate over values of circ_id, starting from conn-\>next_circ_id,
* and with the high bit specified by conn-\>circ_id_type, until we get
* a circ_id that is not in use by any other circuit on that conn.
*
* Return it, or 0 if can't get a unique circ_id.
*/
static circid_t
get_unique_circ_id_by_chan(channel_t *chan)
{
circid_t test_circ_id;
circid_t attempts=0;
circid_t high_bit;
tor_assert(chan);
if (chan->circ_id_type == CIRC_ID_TYPE_NEITHER) {
log_warn(LD_BUG,
"Trying to pick a circuit ID for a connection from "
"a client with no identity.");
return 0;
}
high_bit =
(chan->circ_id_type == CIRC_ID_TYPE_HIGHER) ? 1<<15 : 0;
do {
/* Sequentially iterate over test_circ_id=1...1<<15-1 until we find a
* circID such that (high_bit|test_circ_id) is not already used. */
test_circ_id = chan->next_circ_id++;
if (test_circ_id == 0 || test_circ_id >= 1<<15) {
test_circ_id = 1;
chan->next_circ_id = 2;
}
if (++attempts > 1<<15) {
/* Make sure we don't loop forever if all circ_id's are used. This
* matters because it's an external DoS opportunity.
*/
log_warn(LD_CIRC,"No unused circ IDs. Failing.");
return 0;
}
test_circ_id |= high_bit;
} while (circuit_id_in_use_on_channel(test_circ_id, chan));
return test_circ_id;
}
/** If <b>verbose</b> is false, allocate and return a comma-separated list of
* the currently built elements of <b>circ</b>. If <b>verbose</b> is true, also
* list information about link status in a more verbose format using spaces.
* If <b>verbose_names</b> is false, give nicknames for Named routers and hex
* digests for others; if <b>verbose_names</b> is true, use $DIGEST=Name style
* names.
*/
static char *
circuit_list_path_impl(origin_circuit_t *circ, int verbose, int verbose_names)
{
crypt_path_t *hop;
smartlist_t *elements;
const char *states[] = {"closed", "waiting for keys", "open"};
char *s;
elements = smartlist_new();
if (verbose) {
const char *nickname = build_state_get_exit_nickname(circ->build_state);
smartlist_add_asprintf(elements, "%s%s circ (length %d%s%s):",
circ->build_state->is_internal ? "internal" : "exit",
circ->build_state->need_uptime ? " (high-uptime)" : "",
circ->build_state->desired_path_len,
circ->base_.state == CIRCUIT_STATE_OPEN ? "" : ", last hop ",
circ->base_.state == CIRCUIT_STATE_OPEN ? "" :
(nickname?nickname:"*unnamed*"));
}
hop = circ->cpath;
do {
char *elt;
const char *id;
const node_t *node;
if (!hop)
break;
if (!verbose && hop->state != CPATH_STATE_OPEN)
break;
if (!hop->extend_info)
break;
id = hop->extend_info->identity_digest;
if (verbose_names) {
elt = tor_malloc(MAX_VERBOSE_NICKNAME_LEN+1);
if ((node = node_get_by_id(id))) {
node_get_verbose_nickname(node, elt);
} else if (is_legal_nickname(hop->extend_info->nickname)) {
elt[0] = '$';
base16_encode(elt+1, HEX_DIGEST_LEN+1, id, DIGEST_LEN);
elt[HEX_DIGEST_LEN+1]= '~';
strlcpy(elt+HEX_DIGEST_LEN+2,
hop->extend_info->nickname, MAX_NICKNAME_LEN+1);
} else {
elt[0] = '$';
base16_encode(elt+1, HEX_DIGEST_LEN+1, id, DIGEST_LEN);
}
} else { /* ! verbose_names */
node = node_get_by_id(id);
if (node && node_is_named(node)) {
elt = tor_strdup(node_get_nickname(node));
} else {
elt = tor_malloc(HEX_DIGEST_LEN+2);
elt[0] = '$';
base16_encode(elt+1, HEX_DIGEST_LEN+1, id, DIGEST_LEN);
}
}
tor_assert(elt);
if (verbose) {
tor_assert(hop->state <= 2);
smartlist_add_asprintf(elements,"%s(%s)",elt,states[hop->state]);
tor_free(elt);
} else {
smartlist_add(elements, elt);
}
hop = hop->next;
} while (hop != circ->cpath);
s = smartlist_join_strings(elements, verbose?" ":",", 0, NULL);
SMARTLIST_FOREACH(elements, char*, cp, tor_free(cp));
smartlist_free(elements);
return s;
}
/** If <b>verbose</b> is false, allocate and return a comma-separated
* list of the currently built elements of <b>circ</b>. If
* <b>verbose</b> is true, also list information about link status in
* a more verbose format using spaces.
*/
char *
circuit_list_path(origin_circuit_t *circ, int verbose)
{
return circuit_list_path_impl(circ, verbose, 0);
}
/** Allocate and return a comma-separated list of the currently built elements
* of <b>circ</b>, giving each as a verbose nickname.
*/
char *
circuit_list_path_for_controller(origin_circuit_t *circ)
{
return circuit_list_path_impl(circ, 0, 1);
}
/** Log, at severity <b>severity</b>, the nicknames of each router in
* <b>circ</b>'s cpath. Also log the length of the cpath, and the intended
* exit point.
*/
void
circuit_log_path(int severity, unsigned int domain, origin_circuit_t *circ)
{
char *s = circuit_list_path(circ,1);
tor_log(severity,domain,"%s",s);
tor_free(s);
}
/** Tell the rep(utation)hist(ory) module about the status of the links
* in <b>circ</b>. Hops that have become OPEN are marked as successfully
* extended; the _first_ hop that isn't open (if any) is marked as
* unable to extend.
*/
/* XXXX Someday we should learn from OR circuits too. */
void
circuit_rep_hist_note_result(origin_circuit_t *circ)
{
crypt_path_t *hop;
const char *prev_digest = NULL;
hop = circ->cpath;
if (!hop) /* circuit hasn't started building yet. */
return;
if (server_mode(get_options())) {
const routerinfo_t *me = router_get_my_routerinfo();
if (!me)
return;
prev_digest = me->cache_info.identity_digest;
}
do {
const node_t *node = node_get_by_id(hop->extend_info->identity_digest);
if (node) { /* Why do we check this? We know the identity. -NM XXXX */
if (prev_digest) {
if (hop->state == CPATH_STATE_OPEN)
rep_hist_note_extend_succeeded(prev_digest, node->identity);
else {
rep_hist_note_extend_failed(prev_digest, node->identity);
break;
}
}
prev_digest = node->identity;
} else {
prev_digest = NULL;
}
hop=hop->next;
} while (hop!=circ->cpath);
}
/** Pick all the entries in our cpath. Stop and return 0 when we're
* happy, or return -1 if an error occurs. */
static int
onion_populate_cpath(origin_circuit_t *circ)
{
int r;
again:
r = onion_extend_cpath(circ);
if (r < 0) {
log_info(LD_CIRC,"Generating cpath hop failed.");
return -1;
}
if (r == 0)
goto again;
return 0; /* if r == 1 */
}
/** Create and return a new origin circuit. Initialize its purpose and
* build-state based on our arguments. The <b>flags</b> argument is a
* bitfield of CIRCLAUNCH_* flags. */
origin_circuit_t *
origin_circuit_init(uint8_t purpose, int flags)
{
/* sets circ->p_circ_id and circ->p_chan */
origin_circuit_t *circ = origin_circuit_new();
circuit_set_state(TO_CIRCUIT(circ), CIRCUIT_STATE_CHAN_WAIT);
circ->build_state = tor_malloc_zero(sizeof(cpath_build_state_t));
circ->build_state->onehop_tunnel =
((flags & CIRCLAUNCH_ONEHOP_TUNNEL) ? 1 : 0);
circ->build_state->need_uptime =
((flags & CIRCLAUNCH_NEED_UPTIME) ? 1 : 0);
circ->build_state->need_capacity =
((flags & CIRCLAUNCH_NEED_CAPACITY) ? 1 : 0);
circ->build_state->is_internal =
((flags & CIRCLAUNCH_IS_INTERNAL) ? 1 : 0);
circ->base_.purpose = purpose;
return circ;
}
/** Build a new circuit for <b>purpose</b>. If <b>exit</b>
* is defined, then use that as your exit router, else choose a suitable
* exit node.
*
* Also launch a connection to the first OR in the chosen path, if
* it's not open already.
*/
origin_circuit_t *
circuit_establish_circuit(uint8_t purpose, extend_info_t *exit, int flags)
{
origin_circuit_t *circ;
int err_reason = 0;
circ = origin_circuit_init(purpose, flags);
if (onion_pick_cpath_exit(circ, exit) < 0 ||
onion_populate_cpath(circ) < 0) {
circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_NOPATH);
return NULL;
}
control_event_circuit_status(circ, CIRC_EVENT_LAUNCHED, 0);
if ((err_reason = circuit_handle_first_hop(circ)) < 0) {
circuit_mark_for_close(TO_CIRCUIT(circ), -err_reason);
return NULL;
}
return circ;
}
/** Start establishing the first hop of our circuit. Figure out what
* OR we should connect to, and if necessary start the connection to
* it. If we're already connected, then send the 'create' cell.
* Return 0 for ok, -reason if circ should be marked-for-close. */
int
circuit_handle_first_hop(origin_circuit_t *circ)
{
crypt_path_t *firsthop;
channel_t *n_chan;
int err_reason = 0;
const char *msg = NULL;
int should_launch = 0;
firsthop = onion_next_hop_in_cpath(circ->cpath);
tor_assert(firsthop);
tor_assert(firsthop->extend_info);
/* now see if we're already connected to the first OR in 'route' */
log_debug(LD_CIRC,"Looking for firsthop '%s'",
fmt_addrport(&firsthop->extend_info->addr,
firsthop->extend_info->port));
n_chan = channel_get_for_extend(firsthop->extend_info->identity_digest,
&firsthop->extend_info->addr,
&msg,
&should_launch);
if (!n_chan) {
/* not currently connected in a useful way. */
log_info(LD_CIRC, "Next router is %s: %s",
safe_str_client(extend_info_describe(firsthop->extend_info)),
msg?msg:"???");
circ->base_.n_hop = extend_info_dup(firsthop->extend_info);
if (should_launch) {
if (circ->build_state->onehop_tunnel)
control_event_bootstrap(BOOTSTRAP_STATUS_CONN_DIR, 0);
n_chan = channel_connect_for_circuit(
&firsthop->extend_info->addr,
firsthop->extend_info->port,
firsthop->extend_info->identity_digest);
if (!n_chan) { /* connect failed, forget the whole thing */
log_info(LD_CIRC,"connect to firsthop failed. Closing.");
return -END_CIRC_REASON_CONNECTFAILED;
}
}
log_debug(LD_CIRC,"connecting in progress (or finished). Good.");
/* 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 { /* it's already open. use it. */
tor_assert(!circ->base_.n_hop);
circ->base_.n_chan = n_chan;
log_debug(LD_CIRC,"Conn open. Delivering first onion skin.");
if ((err_reason = circuit_send_next_onion_skin(circ)) < 0) {
log_info(LD_CIRC,"circuit_send_next_onion_skin failed.");
return err_reason;
}
}
return 0;
}
/** Find any circuits that are waiting on <b>or_conn</b> to become
* open and get them to send their create cells forward.
*
* Status is 1 if connect succeeded, or 0 if connect failed.
*/
void
circuit_n_chan_done(channel_t *chan, int status)
{
smartlist_t *pending_circs;
int err_reason = 0;
tor_assert(chan);
log_debug(LD_CIRC,"chan to %s/%s, status=%d",
chan->nickname ? chan->nickname : "NULL",
channel_get_canonical_remote_descr(chan), status);
pending_circs = smartlist_new();
circuit_get_all_pending_on_channel(pending_circs, chan);
SMARTLIST_FOREACH_BEGIN(pending_circs, circuit_t *, circ)
{
/* These checks are redundant wrt get_all_pending_on_or_conn, but I'm
* leaving them in in case it's possible for the status of a circuit to
* change as we're going down the list. */
if (circ->marked_for_close || circ->n_chan || !circ->n_hop ||
circ->state != CIRCUIT_STATE_CHAN_WAIT)
continue;
if (tor_digest_is_zero(circ->n_hop->identity_digest)) {
/* Look at addr/port. This is an unkeyed connection. */
if (!channel_matches_extend_info(chan, circ->n_hop))
continue;
} else {
/* We expected a key. See if it's the right one. */
if (tor_memneq(chan->identity_digest,
circ->n_hop->identity_digest, DIGEST_LEN))
continue;
}
if (!status) { /* chan failed; close circ */
log_info(LD_CIRC,"Channel failed; closing circ.");
circuit_mark_for_close(circ, END_CIRC_REASON_CHANNEL_CLOSED);
continue;
}
log_debug(LD_CIRC, "Found circ, sending create cell.");
/* circuit_deliver_create_cell will set n_circ_id and add us to
* chan_circuid_circuit_map, so we don't need to call
* set_circid_chan here. */
circ->n_chan = chan;
extend_info_free(circ->n_hop);
circ->n_hop = NULL;
if (CIRCUIT_IS_ORIGIN(circ)) {
if ((err_reason =
circuit_send_next_onion_skin(TO_ORIGIN_CIRCUIT(circ))) < 0) {
log_info(LD_CIRC,
"send_next_onion_skin failed; circuit marked for closing.");
circuit_mark_for_close(circ, -err_reason);
continue;
/* XXX could this be bad, eg if next_onion_skin failed because conn
* died? */
}
} else {
/* pull the create cell out of circ->onionskin, and send it */
tor_assert(circ->n_chan_onionskin);
if (circuit_deliver_create_cell(circ,CELL_CREATE,
circ->n_chan_onionskin)<0) {
circuit_mark_for_close(circ, END_CIRC_REASON_RESOURCELIMIT);
continue;
}
tor_free(circ->n_chan_onionskin);
circuit_set_state(circ, CIRCUIT_STATE_OPEN);
}
}
SMARTLIST_FOREACH_END(circ);
smartlist_free(pending_circs);
}
/** Find a new circid that isn't currently in use on the circ->n_chan
* for the outgoing
* circuit <b>circ</b>, and deliver a cell of type <b>cell_type</b>
* (either CELL_CREATE or CELL_CREATE_FAST) with payload <b>payload</b>
* to this circuit.
* Return -1 if we failed to find a suitable circid, else return 0.
*/
static int
circuit_deliver_create_cell(circuit_t *circ, uint8_t cell_type,
const char *payload)
{
cell_t cell;
circid_t id;
tor_assert(circ);
tor_assert(circ->n_chan);
tor_assert(payload);
tor_assert(cell_type == CELL_CREATE || cell_type == CELL_CREATE_FAST);
id = get_unique_circ_id_by_chan(circ->n_chan);
if (!id) {
log_warn(LD_CIRC,"failed to get unique circID.");
return -1;
}
log_debug(LD_CIRC,"Chosen circID %u.", id);
circuit_set_n_circid_chan(circ, id, circ->n_chan);
memset(&cell, 0, sizeof(cell_t));
cell.command = cell_type;
cell.circ_id = circ->n_circ_id;
memcpy(cell.payload, payload, ONIONSKIN_CHALLENGE_LEN);
append_cell_to_circuit_queue(circ, circ->n_chan, &cell,
CELL_DIRECTION_OUT, 0);
if (CIRCUIT_IS_ORIGIN(circ)) {
/* Update began timestamp for circuits starting their first hop */
if (TO_ORIGIN_CIRCUIT(circ)->cpath->state == CPATH_STATE_CLOSED) {
if (circ->n_chan->state != CHANNEL_STATE_OPEN) {
log_warn(LD_CIRC,
"Got first hop for a circuit without an opened channel. "
"State: %s.", channel_state_to_string(circ->n_chan->state));
tor_fragile_assert();
}
tor_gettimeofday(&circ->timestamp_began);
}
/* mark it so it gets better rate limiting treatment. */
channel_timestamp_client(circ->n_chan);
}
return 0;
}
/** We've decided to start our reachability testing. If all
* is set, log this to the user. Return 1 if we did, or 0 if
* we chose not to log anything. */
int
inform_testing_reachability(void)
{
char dirbuf[128];
const routerinfo_t *me = router_get_my_routerinfo();
if (!me)
return 0;
control_event_server_status(LOG_NOTICE,
"CHECKING_REACHABILITY ORADDRESS=%s:%d",
me->address, me->or_port);
if (me->dir_port) {
tor_snprintf(dirbuf, sizeof(dirbuf), " and DirPort %s:%d",
me->address, me->dir_port);
control_event_server_status(LOG_NOTICE,
"CHECKING_REACHABILITY DIRADDRESS=%s:%d",
me->address, me->dir_port);
}
log_notice(LD_OR, "Now checking whether ORPort %s:%d%s %s reachable... "
"(this may take up to %d minutes -- look for log "
"messages indicating success)",
me->address, me->or_port,
me->dir_port ? dirbuf : "",
me->dir_port ? "are" : "is",
TIMEOUT_UNTIL_UNREACHABILITY_COMPLAINT/60);
return 1;
}
/** Return true iff we should send a create_fast cell to start building a given
* circuit */
static INLINE int
should_use_create_fast_for_circuit(origin_circuit_t *circ)
{
const or_options_t *options = get_options();
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 (!options->FastFirstHopPK)
return 0; /* we prefer to avoid create_fast */
if (public_server_mode(options)) {
/* We're a server, and we know an onion key. We can choose.
* Prefer to blend our circuit into the other circuits we are
* creating on behalf of others. */
return 0;
}
return 1;
}
/** Return true if <b>circ</b> is the type of circuit we want to count
* timeouts from. In particular, we want it to have not completed yet
* (already completing indicates we cannibalized it), and we want it to
* have exactly three hops.
*/
int
circuit_timeout_want_to_count_circ(origin_circuit_t *circ)
{
return !circ->has_opened
&& circ->build_state->desired_path_len == DEFAULT_ROUTE_LEN;
}
/** This is the backbone function for building circuits.
*
* If circ's first hop is closed, then we need to build a create
* cell and send it forward.
*
* Otherwise, we need to build a relay extend cell and send it
* forward.
*
* Return -reason if we want to tear down circ, else return 0.
*/
int
circuit_send_next_onion_skin(origin_circuit_t *circ)
{
crypt_path_t *hop;
const node_t *node;
char payload[2+4+DIGEST_LEN+ONIONSKIN_CHALLENGE_LEN];
char *onionskin;
size_t payload_len;
tor_assert(circ);
if (circ->cpath->state == CPATH_STATE_CLOSED) {
int fast;
uint8_t cell_type;
log_debug(LD_CIRC,"First skin; sending create cell.");
if (circ->build_state->onehop_tunnel)
control_event_bootstrap(BOOTSTRAP_STATUS_ONEHOP_CREATE, 0);
else
control_event_bootstrap(BOOTSTRAP_STATUS_CIRCUIT_CREATE, 0);
node = node_get_by_id(circ->base_.n_chan->identity_digest);
fast = should_use_create_fast_for_circuit(circ);
if (!fast) {
/* We are an OR and we know the right onion key: we should
* send an old slow create cell.
*/
cell_type = CELL_CREATE;
if (onion_skin_create(circ->cpath->extend_info->onion_key,
&(circ->cpath->dh_handshake_state),
payload) < 0) {
log_warn(LD_CIRC,"onion_skin_create (first hop) failed.");
return - END_CIRC_REASON_INTERNAL;
}
note_request("cell: create", 1);
} else {
/* We are not an OR, and we're building the first hop of a circuit to a
* new OR: we can be speedy and use CREATE_FAST to save an RSA operation
* and a DH operation. */
cell_type = CELL_CREATE_FAST;
memset(payload, 0, sizeof(payload));
crypto_rand((char*) circ->cpath->fast_handshake_state,
sizeof(circ->cpath->fast_handshake_state));
memcpy(payload, circ->cpath->fast_handshake_state,
sizeof(circ->cpath->fast_handshake_state));
note_request("cell: create fast", 1);
}
if (circuit_deliver_create_cell(TO_CIRCUIT(circ), cell_type, payload) < 0)
return - END_CIRC_REASON_RESOURCELIMIT;
circ->cpath->state = CPATH_STATE_AWAITING_KEYS;
circuit_set_state(TO_CIRCUIT(circ), CIRCUIT_STATE_BUILDING);
log_info(LD_CIRC,"First hop: finished sending %s cell to '%s'",
fast ? "CREATE_FAST" : "CREATE",
node ? node_describe(node) : "<unnamed>");
} else {
tor_assert(circ->cpath->state == CPATH_STATE_OPEN);
tor_assert(circ->base_.state == CIRCUIT_STATE_BUILDING);
log_debug(LD_CIRC,"starting to send subsequent skin.");
hop = onion_next_hop_in_cpath(circ->cpath);
if (!hop) {
/* done building the circuit. whew. */
circuit_set_state(TO_CIRCUIT(circ), CIRCUIT_STATE_OPEN);
if (circuit_timeout_want_to_count_circ(circ)) {
struct timeval end;
long timediff;
tor_gettimeofday(&end);
timediff = tv_mdiff(&circ->base_.timestamp_began, &end);
/*
* If the circuit build time is much greater than we would have cut
* it off at, we probably had a suspend event along this codepath,
* and we should discard the value.
*/
if (timediff < 0 || timediff > 2*circ_times.close_ms+1000) {
log_notice(LD_CIRC, "Strange value for circuit build time: %ldmsec. "
"Assuming clock jump. Purpose %d (%s)", timediff,
circ->base_.purpose,
circuit_purpose_to_string(circ->base_.purpose));
} else if (!circuit_build_times_disabled()) {
/* Only count circuit times if the network is live */
if (circuit_build_times_network_check_live(&circ_times)) {
circuit_build_times_add_time(&circ_times, (build_time_t)timediff);
circuit_build_times_set_timeout(&circ_times);
}
if (circ->base_.purpose != CIRCUIT_PURPOSE_C_MEASURE_TIMEOUT) {
circuit_build_times_network_circ_success(&circ_times);
}
}
}
log_info(LD_CIRC,"circuit built!");
circuit_reset_failure_count(0);
if (circ->build_state->onehop_tunnel || circ->has_opened) {
control_event_bootstrap(BOOTSTRAP_STATUS_REQUESTING_STATUS, 0);
}
if (!can_complete_circuit && !circ->build_state->onehop_tunnel) {
const or_options_t *options = get_options();
can_complete_circuit=1;
/* FFFF Log a count of known routers here */
log_notice(LD_GENERAL,
"Tor has successfully opened a circuit. "
"Looks like client functionality is working.");
control_event_bootstrap(BOOTSTRAP_STATUS_DONE, 0);
control_event_client_status(LOG_NOTICE, "CIRCUIT_ESTABLISHED");
clear_broken_connection_map(1);
if (server_mode(options) && !check_whether_orport_reachable()) {
inform_testing_reachability();
consider_testing_reachability(1, 1);
}
}
pathbias_count_build_success(circ);
circuit_rep_hist_note_result(circ);
circuit_has_opened(circ); /* do other actions as necessary */
/* We're done with measurement circuits here. Just close them */
if (circ->base_.purpose == CIRCUIT_PURPOSE_C_MEASURE_TIMEOUT)
circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_FINISHED);
return 0;
}
if (tor_addr_family(&hop->extend_info->addr) != AF_INET) {
log_warn(LD_BUG, "Trying to extend to a non-IPv4 address.");
return - END_CIRC_REASON_INTERNAL;
}
set_uint32(payload, tor_addr_to_ipv4n(&hop->extend_info->addr));
set_uint16(payload+4, htons(hop->extend_info->port));
onionskin = payload+2+4;
memcpy(payload+2+4+ONIONSKIN_CHALLENGE_LEN,
hop->extend_info->identity_digest, DIGEST_LEN);
payload_len = 2+4+ONIONSKIN_CHALLENGE_LEN+DIGEST_LEN;
if (onion_skin_create(hop->extend_info->onion_key,
&(hop->dh_handshake_state), onionskin) < 0) {
log_warn(LD_CIRC,"onion_skin_create failed.");
return - END_CIRC_REASON_INTERNAL;
}
log_info(LD_CIRC,"Sending extend relay cell.");
note_request("cell: extend", 1);
/* send it to hop->prev, because it will transfer
* it to a create cell and then send to hop */
if (relay_send_command_from_edge(0, TO_CIRCUIT(circ),
RELAY_COMMAND_EXTEND,
payload, payload_len, hop->prev) < 0)
return 0; /* circuit is closed */
hop->state = CPATH_STATE_AWAITING_KEYS;
}
return 0;
}
/** Our clock just jumped by <b>seconds_elapsed</b>. Assume
* something has also gone wrong with our network: notify the user,
* and abandon all not-yet-used circuits. */
void
circuit_note_clock_jumped(int seconds_elapsed)
{
int severity = server_mode(get_options()) ? LOG_WARN : LOG_NOTICE;
tor_log(severity, LD_GENERAL, "Your system clock just jumped %d seconds %s; "
"assuming established circuits no longer work.",
seconds_elapsed >=0 ? seconds_elapsed : -seconds_elapsed,
seconds_elapsed >=0 ? "forward" : "backward");
control_event_general_status(LOG_WARN, "CLOCK_JUMPED TIME=%d",
seconds_elapsed);
can_complete_circuit=0; /* so it'll log when it works again */
control_event_client_status(severity, "CIRCUIT_NOT_ESTABLISHED REASON=%s",
"CLOCK_JUMPED");
circuit_mark_all_unused_circs();
circuit_expire_all_dirty_circs();
}
/** 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(cell_t *cell, circuit_t *circ)
{
channel_t *n_chan;
relay_header_t rh;
char *onionskin;
char *id_digest=NULL;
uint32_t n_addr32;
uint16_t n_port;
tor_addr_t n_addr;
const char *msg = NULL;
int should_launch = 0;
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;
}
if (!server_mode(get_options())) {
log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
"Got an extend cell, but running as a client. Closing.");
return -1;
}
relay_header_unpack(&rh, cell->payload);
if (rh.length < 4+2+ONIONSKIN_CHALLENGE_LEN+DIGEST_LEN) {
log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
"Wrong length %d on extend cell. Closing circuit.",
rh.length);
return -1;
}
n_addr32 = ntohl(get_uint32(cell->payload+RELAY_HEADER_SIZE));
n_port = ntohs(get_uint16(cell->payload+RELAY_HEADER_SIZE+4));
onionskin = (char*) cell->payload+RELAY_HEADER_SIZE+4+2;
id_digest = (char*) cell->payload+RELAY_HEADER_SIZE+4+2+
ONIONSKIN_CHALLENGE_LEN;
tor_addr_from_ipv4h(&n_addr, n_addr32);
if (!n_port || !n_addr32) {
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(&n_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 people 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(id_digest)) {
log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
"Client asked me to extend without specifying an id_digest.");
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(id_digest,
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.");
return -1;
}
n_chan = channel_get_for_extend(id_digest,
&n_addr,
&msg,
&should_launch);
if (!n_chan) {
log_debug(LD_CIRC|LD_OR,"Next router (%s): %s",
fmt_addrport(&n_addr, n_port), msg?msg:"????");
circ->n_hop = extend_info_new(NULL /*nickname*/,
id_digest,
NULL /*onion_key*/,
&n_addr, n_port);
circ->n_chan_onionskin = tor_malloc(ONIONSKIN_CHALLENGE_LEN);
memcpy(circ->n_chan_onionskin, onionskin, ONIONSKIN_CHALLENGE_LEN);
circuit_set_state(circ, CIRCUIT_STATE_CHAN_WAIT);
if (should_launch) {
/* we should try to open a connection */
n_chan = channel_connect_for_circuit(&n_addr, n_port, id_digest);
if (!n_chan) {
log_info(LD_CIRC,"Launching n_chan failed. Closing circuit.");
circuit_mark_for_close(circ, END_CIRC_REASON_CONNECTFAILED);
return 0;
}
log_debug(LD_CIRC,"connecting in progress (or finished). Good.");
}
/* 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;
}
tor_assert(!circ->n_hop); /* Connection is already established. */
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, CELL_CREATE, onionskin) < 0)
return -1;
return 0;
}
/** Initialize cpath-\>{f|b}_{crypto|digest} from the key material in
* key_data. key_data must contain CPATH_KEY_MATERIAL bytes, which are
* used as follows:
* - 20 to initialize f_digest
* - 20 to initialize b_digest
* - 16 to key f_crypto
* - 16 to key b_crypto
*
* (If 'reverse' is true, then f_XX and b_XX are swapped.)
*/
int
circuit_init_cpath_crypto(crypt_path_t *cpath, const char *key_data,
int reverse)
{
crypto_digest_t *tmp_digest;
crypto_cipher_t *tmp_crypto;
tor_assert(cpath);
tor_assert(key_data);
tor_assert(!(cpath->f_crypto || cpath->b_crypto ||
cpath->f_digest || cpath->b_digest));
cpath->f_digest = crypto_digest_new();
crypto_digest_add_bytes(cpath->f_digest, key_data, DIGEST_LEN);
cpath->b_digest = crypto_digest_new();
crypto_digest_add_bytes(cpath->b_digest, key_data+DIGEST_LEN, DIGEST_LEN);
if (!(cpath->f_crypto =
crypto_cipher_new(key_data+(2*DIGEST_LEN)))) {
log_warn(LD_BUG,"Forward cipher initialization failed.");
return -1;
}
if (!(cpath->b_crypto =
crypto_cipher_new(key_data+(2*DIGEST_LEN)+CIPHER_KEY_LEN))) {
log_warn(LD_BUG,"Backward cipher initialization failed.");
return -1;
}
if (reverse) {
tmp_digest = cpath->f_digest;
cpath->f_digest = cpath->b_digest;
cpath->b_digest = tmp_digest;
tmp_crypto = cpath->f_crypto;
cpath->f_crypto = cpath->b_crypto;
cpath->b_crypto = tmp_crypto;
}
return 0;
}
/** The minimum number of first hop completions before we start
* thinking about warning about path bias and dropping guards */
static int
pathbias_get_min_circs(const or_options_t *options)
{
#define DFLT_PATH_BIAS_MIN_CIRC 150
if (options->PathBiasCircThreshold >= 5)
return options->PathBiasCircThreshold;
else
return networkstatus_get_param(NULL, "pb_mincircs",
DFLT_PATH_BIAS_MIN_CIRC,
5, INT32_MAX);
}
/** The circuit success rate below which we issue a notice */
static double
pathbias_get_notice_rate(const or_options_t *options)
{
#define DFLT_PATH_BIAS_NOTICE_PCT 70
if (options->PathBiasNoticeRate >= 0.0)
return options->PathBiasNoticeRate;
else
return networkstatus_get_param(NULL, "pb_noticepct",
DFLT_PATH_BIAS_NOTICE_PCT, 0, 100)/100.0;
}
/* XXXX024 I'd like to have this be static again, but entrynodes.c needs it. */
/** The circuit success rate below which we issue a warn */
double
pathbias_get_warn_rate(const or_options_t *options)
{
#define DFLT_PATH_BIAS_WARN_PCT 50
if (options->PathBiasWarnRate >= 0.0)
return options->PathBiasWarnRate;
else
return networkstatus_get_param(NULL, "pb_warnpct",
DFLT_PATH_BIAS_WARN_PCT, 0, 100)/100.0;
}
/* XXXX024 I'd like to have this be static again, but entrynodes.c needs it. */
/**
* The extreme rate is the rate at which we would drop the guard,
* if pb_dropguard is also set. Otherwise we just warn.
*/
double
pathbias_get_extreme_rate(const or_options_t *options)
{
#define DFLT_PATH_BIAS_EXTREME_PCT 30
if (options->PathBiasExtremeRate >= 0.0)
return options->PathBiasExtremeRate;
else
return networkstatus_get_param(NULL, "pb_extremepct",
DFLT_PATH_BIAS_EXTREME_PCT, 0, 100)/100.0;
}
/* XXXX024 I'd like to have this be static again, but entrynodes.c needs it. */
/**
* If 1, we actually disable use of guards that fall below
* the extreme_pct.
*/
int
pathbias_get_dropguards(const or_options_t *options)
{
#define DFLT_PATH_BIAS_DROP_GUARDS 0
if (options->PathBiasDropGuards >= 0)
return options->PathBiasDropGuards;
else
return networkstatus_get_param(NULL, "pb_dropguards",
DFLT_PATH_BIAS_DROP_GUARDS, 0, 100)/100.0;
}
/**
* This is the number of circuits at which we scale our
* counts by mult_factor/scale_factor. Note, this count is
* not exact, as we only perform the scaling in the event
* of no integer truncation.
*/
static int
pathbias_get_scale_threshold(const or_options_t *options)
{
#define DFLT_PATH_BIAS_SCALE_THRESHOLD 300
if (options->PathBiasScaleThreshold >= 10)
return options->PathBiasScaleThreshold;
else
return networkstatus_get_param(NULL, "pb_scalecircs",
DFLT_PATH_BIAS_SCALE_THRESHOLD, 10,
INT32_MAX);
}
/**
* The scale factor is the denominator for our scaling
* of circuit counts for our path bias window. Note that
* we must be careful of the values we use here, as the
* code only scales in the event of no integer truncation.
*/
static int
pathbias_get_scale_factor(const or_options_t *options)
{
#define DFLT_PATH_BIAS_SCALE_FACTOR 2
if (options->PathBiasScaleFactor >= 1)
return options->PathBiasScaleFactor;
else
return networkstatus_get_param(NULL, "pb_scalefactor",
DFLT_PATH_BIAS_SCALE_FACTOR, 1, INT32_MAX);
}
/**
* The mult factor is the numerator for our scaling
* of circuit counts for our path bias window. It
* allows us to scale by fractions.
*/
static int
pathbias_get_mult_factor(const or_options_t *options)
{
#define DFLT_PATH_BIAS_MULT_FACTOR 1
if (options->PathBiasMultFactor >= 1)
return options->PathBiasMultFactor;
else
return networkstatus_get_param(NULL, "pb_multfactor",
DFLT_PATH_BIAS_MULT_FACTOR, 1,
pathbias_get_scale_factor(options));
}
/**
* If this parameter is set to a true value (default), we use the
* successful_circuits_closed. Otherwise, we use the success_count.
*/
static int
pathbias_use_close_counts(const or_options_t *options)
{
#define DFLT_PATH_BIAS_USE_CLOSE_COUNTS 1
if (options->PathBiasUseCloseCounts >= 0)
return options->PathBiasUseCloseCounts;
else
return networkstatus_get_param(NULL, "pb_useclosecounts",
DFLT_PATH_BIAS_USE_CLOSE_COUNTS, 0, 1);
}
/**
* Convert a Guard's path state to string.
*/
static const char *
pathbias_state_to_string(path_state_t state)
{
switch (state) {
case PATH_STATE_NEW_CIRC:
return "new";
case PATH_STATE_DID_FIRST_HOP:
return "first hop";
case PATH_STATE_BUILD_SUCCEEDED:
return "build succeeded";
case PATH_STATE_USE_SUCCEEDED:
return "use succeeded";
}
return "unknown";
}
/**
* Decide if the path bias code should count a circuit.
*
* @returns 1 if we should count it, 0 otherwise.
*/
static int
pathbias_should_count(origin_circuit_t *circ)
{
#define PATHBIAS_COUNT_INTERVAL (600)
static ratelim_t count_limit =
RATELIM_INIT(PATHBIAS_COUNT_INTERVAL);
char *rate_msg = NULL;
/* We can't do path bias accounting without entry guards.
* Testing and controller circuits also have no guards.
* We also don't count server-side rends, because their
* endpoint could be chosen maliciously. */
if (get_options()->UseEntryGuards == 0 ||
circ->base_.purpose == CIRCUIT_PURPOSE_TESTING ||
circ->base_.purpose == CIRCUIT_PURPOSE_CONTROLLER ||
circ->base_.purpose == CIRCUIT_PURPOSE_S_CONNECT_REND ||
circ->base_.purpose == CIRCUIT_PURPOSE_S_REND_JOINED) {
return 0;
}
/* Completely ignore one hop circuits */
if (circ->build_state->onehop_tunnel ||
circ->build_state->desired_path_len == 1) {
/* Check for inconsistency */
if (circ->build_state->desired_path_len != 1 ||
!circ->build_state->onehop_tunnel) {
if ((rate_msg = rate_limit_log(&count_limit, approx_time()))) {
log_notice(LD_BUG,
"One-hop circuit has length %d. Path state is %s. "
"Circuit is a %s currently %s.%s",
circ->build_state->desired_path_len,
pathbias_state_to_string(circ->path_state),
circuit_purpose_to_string(circ->base_.purpose),
circuit_state_to_string(circ->base_.state),
rate_msg);
tor_free(rate_msg);
}
tor_fragile_assert();
}
return 0;
}
return 1;
}
/**
* Check our circuit state to see if this is a successful first hop.
* If so, record it in the current guard's path bias first_hop count.
*
* Also check for several potential error cases for bug #6475.
*/
static int
pathbias_count_first_hop(origin_circuit_t *circ)
{
#define FIRST_HOP_NOTICE_INTERVAL (600)
static ratelim_t first_hop_notice_limit =
RATELIM_INIT(FIRST_HOP_NOTICE_INTERVAL);
char *rate_msg = NULL;
if (!pathbias_should_count(circ)) {
return 0;
}
if (circ->cpath->state == CPATH_STATE_AWAITING_KEYS) {
/* Help track down the real cause of bug #6475: */
if (circ->has_opened && circ->path_state != PATH_STATE_DID_FIRST_HOP) {
if ((rate_msg = rate_limit_log(&first_hop_notice_limit,
approx_time()))) {
log_info(LD_BUG,
"Opened circuit is in strange path state %s. "
"Circuit is a %s currently %s.%s",
pathbias_state_to_string(circ->path_state),
circuit_purpose_to_string(circ->base_.purpose),
circuit_state_to_string(circ->base_.state),
rate_msg);
tor_free(rate_msg);
}
}
/* Don't re-count cannibalized circs.. */
if (!circ->has_opened) {
entry_guard_t *guard = NULL;
if (circ->cpath && circ->cpath->extend_info) {
guard = entry_guard_get_by_id_digest(
circ->cpath->extend_info->identity_digest);
} else if (circ->base_.n_chan) {
guard =
entry_guard_get_by_id_digest(circ->base_.n_chan->identity_digest);
}
if (guard) {
if (circ->path_state == PATH_STATE_NEW_CIRC) {
circ->path_state = PATH_STATE_DID_FIRST_HOP;
if (entry_guard_inc_first_hop_count(guard) < 0) {
/* Bogus guard; we already warned. */
return -END_CIRC_REASON_TORPROTOCOL;
}
} else {
if ((rate_msg = rate_limit_log(&first_hop_notice_limit,
approx_time()))) {
log_info(LD_BUG,
"Unopened circuit has strange path state %s. "
"Circuit is a %s currently %s.%s",
pathbias_state_to_string(circ->path_state),
circuit_purpose_to_string(circ->base_.purpose),
circuit_state_to_string(circ->base_.state),
rate_msg);
tor_free(rate_msg);
}
}
} else {
if ((rate_msg = rate_limit_log(&first_hop_notice_limit,
approx_time()))) {
log_info(LD_BUG,
"Unopened circuit has no known guard. "
"Circuit is a %s currently %s.%s",
circuit_purpose_to_string(circ->base_.purpose),
circuit_state_to_string(circ->base_.state),
rate_msg);
tor_free(rate_msg);
}
}
}
} else {
/* Help track down the real cause of bug #6475: */
if (circ->path_state == PATH_STATE_NEW_CIRC) {
if ((rate_msg = rate_limit_log(&first_hop_notice_limit,
approx_time()))) {
log_info(LD_BUG,
"A %s circuit is in cpath state %d (opened: %d). "
"Circuit is a %s currently %s.%s",
pathbias_state_to_string(circ->path_state),
circ->cpath->state, circ->has_opened,
circuit_purpose_to_string(circ->base_.purpose),
circuit_state_to_string(circ->base_.state),
rate_msg);
tor_free(rate_msg);
}
}
}
return 0;
}
/**
* Check our circuit state to see if this is a successful circuit
* completion. If so, record it in the current guard's path bias
* success count.
*
* Also check for several potential error cases for bug #6475.
*/
static void
pathbias_count_build_success(origin_circuit_t *circ)
{
#define SUCCESS_NOTICE_INTERVAL (600)
static ratelim_t success_notice_limit =
RATELIM_INIT(SUCCESS_NOTICE_INTERVAL);
char *rate_msg = NULL;
entry_guard_t *guard = NULL;
if (!pathbias_should_count(circ)) {
return;
}
/* Don't count cannibalized/reused circs for path bias
* build success.. They get counted under use success */
if (!circ->has_opened) {
if (circ->cpath && circ->cpath->extend_info) {
guard = entry_guard_get_by_id_digest(
circ->cpath->extend_info->identity_digest);
}
if (guard) {
if (circ->path_state == PATH_STATE_DID_FIRST_HOP) {
circ->path_state = PATH_STATE_BUILD_SUCCEEDED;
guard->circuit_successes++;
log_info(LD_CIRC, "Got success count %u/%u for guard %s=%s",
guard->circuit_successes, guard->first_hops,
guard->nickname, hex_str(guard->identity, DIGEST_LEN));
} else {
if ((rate_msg = rate_limit_log(&success_notice_limit,
approx_time()))) {
log_info(LD_BUG,
"Succeeded circuit is in strange path state %s. "
"Circuit is a %s currently %s.%s",
pathbias_state_to_string(circ->path_state),
circuit_purpose_to_string(circ->base_.purpose),
circuit_state_to_string(circ->base_.state),
rate_msg);
tor_free(rate_msg);
}
}
if (guard->first_hops < guard->circuit_successes) {
log_notice(LD_BUG, "Unexpectedly high circuit_successes (%u/%u) "
"for guard %s=%s",
guard->circuit_successes, guard->first_hops,
guard->nickname, hex_str(guard->identity, DIGEST_LEN));
}
/* In rare cases, CIRCUIT_PURPOSE_TESTING can get converted to
* CIRCUIT_PURPOSE_C_MEASURE_TIMEOUT and have no guards here.
* No need to log that case. */
} else if (circ->base_.purpose != CIRCUIT_PURPOSE_C_MEASURE_TIMEOUT) {
if ((rate_msg = rate_limit_log(&success_notice_limit,
approx_time()))) {
log_info(LD_BUG,
"Completed circuit has no known guard. "
"Circuit is a %s currently %s.%s",
circuit_purpose_to_string(circ->base_.purpose),
circuit_state_to_string(circ->base_.state),
rate_msg);
tor_free(rate_msg);
}
}
} else {
if (circ->path_state < PATH_STATE_BUILD_SUCCEEDED) {
if ((rate_msg = rate_limit_log(&success_notice_limit,
approx_time()))) {
log_info(LD_BUG,
"Opened circuit is in strange path state %s. "
"Circuit is a %s currently %s.%s",
pathbias_state_to_string(circ->path_state),
circuit_purpose_to_string(circ->base_.purpose),
circuit_state_to_string(circ->base_.state),
rate_msg);
tor_free(rate_msg);
}
}
}
}
/**
* Check if a circuit was used and/or closed successfully.
*/
void
pathbias_check_close(origin_circuit_t *ocirc, int reason)
{
circuit_t *circ = &ocirc->base_;
if (!pathbias_should_count(circ)) {
return;
}
if (ocirc->path_state == PATH_STATE_BUILD_SUCCEEDED) {
if (circ->timestamp_dirty) {
/* Any circuit where there were attempted streams but no successful
* streams could be bias */
// XXX: May open up attacks if the adversary can force connections
// on unresponsive hosts to use new circs. Vidalia displayes a "Retrying"
// state.. Can we use that? Does optimistic data change this?
// XXX: Sub-attack: in collusion with an intro point, you can induce bias
// through the web. Need a Torbutton patch to prevent this.
/* FIXME: This is not ideal, but it prevents the case where a
* CPU overloaded intro point is chosen.
* XXX: Is this reason code authenticated? */
if (circ->purpose == CIRCUIT_PURPOSE_C_INTRODUCING &&
reason ==
END_CIRC_REASON_FLAG_REMOTE|END_CIRC_REASON_RESOURCELIMIT) {
log_info(LD_CIRC,
"Ignoring CPU overload intro circuit without successful use. "
"Circuit purpose %d currently %s.",
reason, circ->purpose, circuit_state_to_string(circ->state));
} else {
log_info(LD_CIRC,
"Circuit closed without successful use for reason %d. "
"Circuit purpose %d currently %s.",
reason, circ->purpose, circuit_state_to_string(circ->state));
pathbias_count_unusable(ocirc);
}
} else {
if (reason & END_CIRC_REASON_FLAG_REMOTE) {
/* Unused remote circ close reasons all could be bias */
// XXX: We hit this a lot for hidserv circs with purposes:
// CIRCUIT_PURPOSE_S_CONNECT_REND (reasons: 514,517,520)
// CIRCUIT_PURPOSE_S_REND_JOINED (reasons: 514,517,520)
// == reasons: 2,3,8. Client-side timeouts?
log_info(LD_CIRC,
"Circuit remote-closed without successful use for reason %d. "
"Circuit purpose %d currently %s.",
reason, circ->purpose, circuit_state_to_string(circ->state));
pathbias_count_collapse(ocirc);
} else if ((reason & ~END_CIRC_REASON_FLAG_REMOTE)
== END_CIRC_REASON_CHANNEL_CLOSED &&
circ->n_chan &&
circ->n_chan->reason_for_closing
!= CHANNEL_CLOSE_REQUESTED) {
/* If we didn't close the channel ourselves, it could be bias */
/* FIXME: Only count bias if the network is live?
* What about clock jumps/suspends? */
log_info(LD_CIRC,
"Circuit's channel closed without successful use for reason %d, "
"channel reason %d. Circuit purpose %d currently %s.",
reason, circ->n_chan->reason_for_closing,
circ->purpose, circuit_state_to_string(circ->state));
pathbias_count_collapse(ocirc);
} else {
pathbias_count_successful_close(ocirc);
}
}
} else if (ocirc->path_state == PATH_STATE_USE_SUCCEEDED) {
pathbias_count_successful_close(ocirc);
}
}
/**
* Count a successfully closed circuit.
*/
static void
pathbias_count_successful_close(origin_circuit_t *circ)
{
entry_guard_t *guard = NULL;
if (!pathbias_should_count(circ)) {
return;
}
if (circ->cpath && circ->cpath->extend_info) {
guard = entry_guard_get_by_id_digest(
circ->cpath->extend_info->identity_digest);
}
if (guard) {
/* In the long run: circuit_success ~= successful_circuit_close +
* circ_failure + stream_failure */
guard->successful_circuits_closed++;
entry_guards_changed();
} else if (circ->base_.purpose != CIRCUIT_PURPOSE_C_MEASURE_TIMEOUT) {
/* In rare cases, CIRCUIT_PURPOSE_TESTING can get converted to
* CIRCUIT_PURPOSE_C_MEASURE_TIMEOUT and have no guards here.
* No need to log that case. */
log_info(LD_BUG,
"Successfully closed circuit has no known guard. "
"Circuit is a %s currently %s",
circuit_purpose_to_string(circ->base_.purpose),
circuit_state_to_string(circ->base_.state));
}
}
/**
* Count a circuit that fails after it is built, but before it can
* carry any traffic.
*
* This is needed because there are ways to destroy a
* circuit after it has successfully completed. Right now, this is
* used for purely informational/debugging purposes.
*/
static void
pathbias_count_collapse(origin_circuit_t *circ)
{
entry_guard_t *guard = NULL;
if (!pathbias_should_count(circ)) {
return;
}
if (circ->cpath && circ->cpath->extend_info) {
guard = entry_guard_get_by_id_digest(
circ->cpath->extend_info->identity_digest);
}
if (guard) {
guard->collapsed_circuits++;
entry_guards_changed();
} else if (circ->base_.purpose != CIRCUIT_PURPOSE_C_MEASURE_TIMEOUT) {
/* In rare cases, CIRCUIT_PURPOSE_TESTING can get converted to
* CIRCUIT_PURPOSE_C_MEASURE_TIMEOUT and have no guards here.
* No need to log that case. */
log_info(LD_BUG,
"Destroyed circuit has no known guard. "
"Circuit is a %s currently %s",
circuit_purpose_to_string(circ->base_.purpose),
circuit_state_to_string(circ->base_.state));
}
}
static void
pathbias_count_unusable(origin_circuit_t *circ)
{
entry_guard_t *guard = NULL;
if (!pathbias_should_count(circ)) {
return;
}
if (circ->cpath && circ->cpath->extend_info) {
guard = entry_guard_get_by_id_digest(
circ->cpath->extend_info->identity_digest);
}
if (guard) {
guard->unusable_circuits++;
entry_guards_changed();
} else if (circ->base_.purpose != CIRCUIT_PURPOSE_C_MEASURE_TIMEOUT) {
/* In rare cases, CIRCUIT_PURPOSE_TESTING can get converted to
* CIRCUIT_PURPOSE_C_MEASURE_TIMEOUT and have no guards here.
* No need to log that case. */
log_info(LD_BUG,
"Stream-failing circuit has no known guard. "
"Circuit is a %s currently %s",
circuit_purpose_to_string(circ->base_.purpose),
circuit_state_to_string(circ->base_.state));
}
}
/**
* Count timeouts for path bias log messages.
*
* These counts are purely informational.
*/
void
pathbias_count_timeout(origin_circuit_t *circ)
{
entry_guard_t *guard = NULL;
if (!pathbias_should_count(circ)) {
return;
}
/* For hidden service circs, they can actually be used
* successfully and then time out later (because
* the other side declines to use them). */
if (circ->path_state == PATH_STATE_USE_SUCCEEDED) {
return;
}
if (circ->cpath && circ->cpath->extend_info) {
guard = entry_guard_get_by_id_digest(
circ->cpath->extend_info->identity_digest);
}
if (guard) {
guard->timeouts++;
entry_guards_changed();
}
}
// XXX: DOCDOC
int
pathbias_get_closed_count(entry_guard_t *guard)
{
circuit_t *circ = global_circuitlist;
int open_circuits = 0;
/* Count currently open circuits. Give them the benefit of the doubt */
for ( ; circ; circ = circ->next) {
origin_circuit_t *ocirc = NULL;
if (!CIRCUIT_IS_ORIGIN(circ) || /* didn't originate here */
circ->marked_for_close) /* already counted */
continue;
ocirc = TO_ORIGIN_CIRCUIT(circ);
if(!ocirc->cpath || !ocirc->cpath->extend_info)
continue;
if (ocirc->path_state >= PATH_STATE_BUILD_SUCCEEDED &&
(memcmp(guard->identity,
ocirc->cpath->extend_info->identity_digest,
DIGEST_LEN)
== 0)) {
open_circuits++;
}
}
return guard->successful_circuits_closed + open_circuits;
}
/**
* This function checks the consensus parameters to decide
* if it should return guard->circuit_successes or
* guard->successful_circuits_closed.
*/
static int
pathbias_get_success_count(entry_guard_t *guard)
{
if (pathbias_use_close_counts(get_options())) {
return pathbias_get_closed_count(guard);
} else {
return guard->circuit_successes;
}
}
/** Increment the number of times we successfully extended a circuit to
* 'guard', first checking if the failure rate is high enough that we should
* eliminate the guard. Return -1 if the guard looks no good; return 0 if the
* guard looks fine. */
static int
entry_guard_inc_first_hop_count(entry_guard_t *guard)
{
const or_options_t *options = get_options();
entry_guards_changed();
if (guard->first_hops > (unsigned)pathbias_get_min_circs(options)) {
/* Note: We rely on the < comparison here to allow us to set a 0
* rate and disable the feature entirely. If refactoring, don't
* change to <= */
if (pathbias_get_success_count(guard)/((double)guard->first_hops)
< pathbias_get_extreme_rate(options)) {
/* Dropping is currently disabled by default. */
if (pathbias_get_dropguards(options)) {
if (!guard->path_bias_disabled) {
log_warn(LD_CIRC,
"Your Guard %s=%s is failing an extremely large amount of "
"circuits. To avoid potential route manipluation attacks, "
"Tor has disabled use of this guard. "
"Success counts are %d/%d. %d circuits completed, %d "
"were unusable, %d collapsed, and %d timed out. For "
"reference, your timeout cutoff is %ld seconds.",
guard->nickname, hex_str(guard->identity, DIGEST_LEN),
pathbias_get_closed_count(guard), guard->first_hops,
guard->circuit_successes, guard->unusable_circuits,
guard->collapsed_circuits, guard->timeouts,
(long)circ_times.close_ms/1000);
guard->path_bias_disabled = 1;
guard->bad_since = approx_time();
return -1;
}
} else if (!guard->path_bias_extreme) {
guard->path_bias_extreme = 1;
log_warn(LD_CIRC,
"Your Guard %s=%s is failing an extremely large amount of "
"circuits. This could indicate a route manipulation attack, "
"extreme network overload, or a bug. "
"Success counts are %d/%d. %d circuits completed, %d "
"were unusable, %d collapsed, and %d timed out. For "
"reference, your timeout cutoff is %ld seconds.",
guard->nickname, hex_str(guard->identity, DIGEST_LEN),
pathbias_get_closed_count(guard), guard->first_hops,
guard->circuit_successes, guard->unusable_circuits,
guard->collapsed_circuits, guard->timeouts,
(long)circ_times.close_ms/1000);
}
} else if (pathbias_get_success_count(guard)/((double)guard->first_hops)
< pathbias_get_warn_rate(options)) {
if (!guard->path_bias_warned) {
guard->path_bias_warned = 1;
log_warn(LD_CIRC,
"Your Guard %s=%s is failing a very large amount of "
"circuits. Most likely this means the Tor network is "
"overloaded, but it could also mean an attack against "
"you or the potentially the guard itself. "
"Success counts are %d/%d. %d circuits completed, %d "
"were unusable, %d collapsed, and %d timed out. For "
"reference, your timeout cutoff is %ld seconds.",
guard->nickname, hex_str(guard->identity, DIGEST_LEN),
pathbias_get_closed_count(guard), guard->first_hops,
guard->circuit_successes, guard->unusable_circuits,
guard->collapsed_circuits, guard->timeouts,
(long)circ_times.close_ms/1000);
}
} else if (pathbias_get_success_count(guard)/((double)guard->first_hops)
< pathbias_get_notice_rate(options)) {
if (!guard->path_bias_noticed) {
guard->path_bias_noticed = 1;
log_notice(LD_CIRC,
"Your Guard %s=%s is failing more circuits than usual. "
"Most likely this means the Tor network is overloaded. "
"Success counts are %d/%d. %d circuits completed, %d "
"were unusable, %d collapsed, and %d timed out. For "
"reference, your timeout cutoff is %ld seconds.",
guard->nickname, hex_str(guard->identity, DIGEST_LEN),
pathbias_get_closed_count(guard), guard->first_hops,
guard->circuit_successes, guard->unusable_circuits,
guard->collapsed_circuits, guard->timeouts,
(long)circ_times.close_ms/1000);
}
}
}
/* If we get a ton of circuits, just scale everything down */
if (guard->first_hops > (unsigned)pathbias_get_scale_threshold(options)) {
const int scale_factor = pathbias_get_scale_factor(options);
const int mult_factor = pathbias_get_mult_factor(options);
/* Only scale if there will be no rounding error for our scaling
* factors */
if (((mult_factor*guard->first_hops) % scale_factor) == 0 &&
((mult_factor*guard->circuit_successes) % scale_factor) == 0) {
log_info(LD_CIRC,
"Scaling pathbias counts to (%u/%u)*(%d/%d) for guard %s=%s",
guard->circuit_successes, guard->first_hops, mult_factor,
scale_factor, guard->nickname, hex_str(guard->identity,
DIGEST_LEN));
guard->first_hops *= mult_factor;
guard->circuit_successes *= mult_factor;
guard->timeouts *= mult_factor;
guard->successful_circuits_closed *= mult_factor;
guard->collapsed_circuits *= mult_factor;
guard->unusable_circuits *= mult_factor;
guard->first_hops /= scale_factor;
guard->circuit_successes /= scale_factor;
guard->timeouts /= scale_factor;
guard->successful_circuits_closed /= scale_factor;
guard->collapsed_circuits /= scale_factor;
guard->unusable_circuits /= scale_factor;
}
}
guard->first_hops++;
log_info(LD_CIRC, "Got success count %u/%u for guard %s=%s",
guard->circuit_successes, guard->first_hops, guard->nickname,
hex_str(guard->identity, DIGEST_LEN));
return 0;
}
/** A created or extended cell came back to us on the circuit, and it included
* <b>reply</b> as its body. (If <b>reply_type</b> is CELL_CREATED, the body
* contains (the second DH key, plus KH). If <b>reply_type</b> is
* CELL_CREATED_FAST, the body contains a secret y and a hash H(x|y).)
*
* Calculate the appropriate keys and digests, make sure KH is
* correct, and initialize this hop of the cpath.
*
* Return - reason if we want to mark circ for close, else return 0.
*/
int
circuit_finish_handshake(origin_circuit_t *circ, uint8_t reply_type,
const uint8_t *reply)
{
char keys[CPATH_KEY_MATERIAL_LEN];
crypt_path_t *hop;
int rv;
if ((rv = pathbias_count_first_hop(circ)) < 0)
return rv;
if (circ->cpath->state == CPATH_STATE_AWAITING_KEYS) {
hop = circ->cpath;
} else {
hop = onion_next_hop_in_cpath(circ->cpath);
if (!hop) { /* got an extended when we're all done? */
log_warn(LD_PROTOCOL,"got extended when circ already built? Closing.");
return - END_CIRC_REASON_TORPROTOCOL;
}
}
tor_assert(hop->state == CPATH_STATE_AWAITING_KEYS);
if (reply_type == CELL_CREATED && hop->dh_handshake_state) {
if (onion_skin_client_handshake(hop->dh_handshake_state, (char*)reply,keys,
DIGEST_LEN*2+CIPHER_KEY_LEN*2) < 0) {
log_warn(LD_CIRC,"onion_skin_client_handshake failed.");
return -END_CIRC_REASON_TORPROTOCOL;
}
/* Remember hash of g^xy */
memcpy(hop->handshake_digest, reply+DH_KEY_LEN, DIGEST_LEN);
} else if (reply_type == CELL_CREATED_FAST && !hop->dh_handshake_state) {
if (fast_client_handshake(hop->fast_handshake_state, reply,
(uint8_t*)keys,
DIGEST_LEN*2+CIPHER_KEY_LEN*2) < 0) {
log_warn(LD_CIRC,"fast_client_handshake failed.");
return -END_CIRC_REASON_TORPROTOCOL;
}
memcpy(hop->handshake_digest, reply+DIGEST_LEN, DIGEST_LEN);
} else {
log_warn(LD_PROTOCOL,"CREATED cell type did not match CREATE cell type.");
return -END_CIRC_REASON_TORPROTOCOL;
}
crypto_dh_free(hop->dh_handshake_state); /* don't need it anymore */
hop->dh_handshake_state = NULL;
memset(hop->fast_handshake_state, 0, sizeof(hop->fast_handshake_state));
if (circuit_init_cpath_crypto(hop, keys, 0)<0) {
return -END_CIRC_REASON_TORPROTOCOL;
}
hop->state = CPATH_STATE_OPEN;
log_info(LD_CIRC,"Finished building %scircuit hop:",
(reply_type == CELL_CREATED_FAST) ? "fast " : "");
circuit_log_path(LOG_INFO,LD_CIRC,circ);
control_event_circuit_status(circ, CIRC_EVENT_EXTENDED, 0);
return 0;
}
/** We received a relay truncated cell on circ.
*
* Since we don't ask for truncates currently, getting a truncated
* means that a connection broke or an extend failed. For now,
* just give up: for circ to close, and return 0.
*/
int
circuit_truncated(origin_circuit_t *circ, crypt_path_t *layer, int reason)
{
// crypt_path_t *victim;
// connection_t *stream;
tor_assert(circ);
tor_assert(layer);
/* XXX Since we don't ask for truncates currently, getting a truncated
* means that a connection broke or an extend failed. For now,
* just give up.
*/
circuit_mark_for_close(TO_CIRCUIT(circ),
END_CIRC_REASON_FLAG_REMOTE|reason);
return 0;
#if 0
while (layer->next != circ->cpath) {
/* we need to clear out layer->next */
victim = layer->next;
log_debug(LD_CIRC, "Killing a layer of the cpath.");
for (stream = circ->p_streams; stream; stream=stream->next_stream) {
if (stream->cpath_layer == victim) {
log_info(LD_APP, "Marking stream %d for close because of truncate.",
stream->stream_id);
/* no need to send 'end' relay cells,
* because the other side's already dead
*/
connection_mark_unattached_ap(stream, END_STREAM_REASON_DESTROY);
}
}
layer->next = victim->next;
circuit_free_cpath_node(victim);
}
log_info(LD_CIRC, "finished");
return 0;
#endif
}
/** Given a response payload and keys, initialize, then send a created
* cell back.
*/
int
onionskin_answer(or_circuit_t *circ, uint8_t cell_type, const char *payload,
const char *keys)
{
cell_t cell;
crypt_path_t *tmp_cpath;
tmp_cpath = tor_malloc_zero(sizeof(crypt_path_t));
tmp_cpath->magic = CRYPT_PATH_MAGIC;
memset(&cell, 0, sizeof(cell_t));
cell.command = cell_type;
cell.circ_id = circ->p_circ_id;
circuit_set_state(TO_CIRCUIT(circ), CIRCUIT_STATE_OPEN);
memcpy(cell.payload, payload,
cell_type == CELL_CREATED ? ONIONSKIN_REPLY_LEN : DIGEST_LEN*2);
log_debug(LD_CIRC,"init digest forward 0x%.8x, backward 0x%.8x.",
(unsigned int)get_uint32(keys),
(unsigned int)get_uint32(keys+20));
if (circuit_init_cpath_crypto(tmp_cpath, keys, 0)<0) {
log_warn(LD_BUG,"Circuit initialization failed");
tor_free(tmp_cpath);
return -1;
}
circ->n_digest = tmp_cpath->f_digest;
circ->n_crypto = tmp_cpath->f_crypto;
circ->p_digest = tmp_cpath->b_digest;
circ->p_crypto = tmp_cpath->b_crypto;
tmp_cpath->magic = 0;
tor_free(tmp_cpath);
if (cell_type == CELL_CREATED)
memcpy(circ->handshake_digest, cell.payload+DH_KEY_LEN, DIGEST_LEN);
else
memcpy(circ->handshake_digest, cell.payload+DIGEST_LEN, DIGEST_LEN);
circ->is_first_hop = (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.",
circ->is_first_hop ? "created_fast" : "created");
if (!channel_is_local(circ->p_chan) &&
!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;
}
/** Choose a length for a circuit of purpose <b>purpose</b>.
* Default length is 3 + the number of endpoints that would give something
* away. If the routerlist <b>routers</b> doesn't have enough routers
* to handle the desired path length, return as large a path length as
* is feasible, except if it's less than 2, in which case return -1.
*/
static int
new_route_len(uint8_t purpose, extend_info_t *exit,
smartlist_t *nodes)
{
int num_acceptable_routers;
int routelen;
tor_assert(nodes);
routelen = DEFAULT_ROUTE_LEN;
if (exit &&
purpose != CIRCUIT_PURPOSE_TESTING &&
purpose != CIRCUIT_PURPOSE_S_ESTABLISH_INTRO)
routelen++;
num_acceptable_routers = count_acceptable_nodes(nodes);
log_debug(LD_CIRC,"Chosen route length %d (%d/%d routers suitable).",
routelen, num_acceptable_routers, smartlist_len(nodes));
if (num_acceptable_routers < 2) {
log_info(LD_CIRC,
"Not enough acceptable routers (%d). Discarding this circuit.",
num_acceptable_routers);
return -1;
}
if (num_acceptable_routers < routelen) {
log_info(LD_CIRC,"Not enough routers: cutting routelen from %d to %d.",
routelen, num_acceptable_routers);
routelen = num_acceptable_routers;
}
return routelen;
}
/** Return a newly allocated list of uint16_t * for each predicted port not
* handled by a current circuit. */
static smartlist_t *
circuit_get_unhandled_ports(time_t now)
{
smartlist_t *dest = rep_hist_get_predicted_ports(now);
circuit_remove_handled_ports(dest);
return dest;
}
/** Return 1 if we already have circuits present or on the way for
* all anticipated ports. Return 0 if we should make more.
*
* If we're returning 0, set need_uptime and need_capacity to
* indicate any requirements that the unhandled ports have.
*/
int
circuit_all_predicted_ports_handled(time_t now, int *need_uptime,
int *need_capacity)
{
int i, enough;
uint16_t *port;
smartlist_t *sl = circuit_get_unhandled_ports(now);
smartlist_t *LongLivedServices = get_options()->LongLivedPorts;
tor_assert(need_uptime);
tor_assert(need_capacity);
// Always predict need_capacity
*need_capacity = 1;
enough = (smartlist_len(sl) == 0);
for (i = 0; i < smartlist_len(sl); ++i) {
port = smartlist_get(sl, i);
if (smartlist_string_num_isin(LongLivedServices, *port))
*need_uptime = 1;
tor_free(port);
}
smartlist_free(sl);
return enough;
}
/** Return 1 if <b>node</b> can handle one or more of the ports in
* <b>needed_ports</b>, else return 0.
*/
static int
node_handles_some_port(const node_t *node, smartlist_t *needed_ports)
{ /* XXXX MOVE */
int i;
uint16_t port;
for (i = 0; i < smartlist_len(needed_ports); ++i) {
addr_policy_result_t r;
/* alignment issues aren't a worry for this dereference, since
needed_ports is explicitly a smartlist of uint16_t's */
port = *(uint16_t *)smartlist_get(needed_ports, i);
tor_assert(port);
if (node)
r = compare_tor_addr_to_node_policy(NULL, port, node);
else
continue;
if (r != ADDR_POLICY_REJECTED && r != ADDR_POLICY_PROBABLY_REJECTED)
return 1;
}
return 0;
}
/** Return true iff <b>conn</b> needs another general circuit to be
* built. */
static int
ap_stream_wants_exit_attention(connection_t *conn)
{
entry_connection_t *entry;
if (conn->type != CONN_TYPE_AP)
return 0;
entry = TO_ENTRY_CONN(conn);
if (conn->state == AP_CONN_STATE_CIRCUIT_WAIT &&
!conn->marked_for_close &&
!(entry->want_onehop) && /* ignore one-hop streams */
!(entry->use_begindir) && /* ignore targeted dir fetches */
!(entry->chosen_exit_name) && /* ignore defined streams */
!connection_edge_is_rendezvous_stream(TO_EDGE_CONN(conn)) &&
!circuit_stream_is_being_handled(TO_ENTRY_CONN(conn), 0,
MIN_CIRCUITS_HANDLING_STREAM))
return 1;
return 0;
}
/** Return a pointer to a suitable router to be the exit node for the
* general-purpose circuit we're about to build.
*
* Look through the connection array, and choose a router that maximizes
* the number of pending streams that can exit from this router.
*
* Return NULL if we can't find any suitable routers.
*/
static const node_t *
choose_good_exit_server_general(int need_uptime, int need_capacity)
{
int *n_supported;
int n_pending_connections = 0;
smartlist_t *connections;
int best_support = -1;
int n_best_support=0;
const or_options_t *options = get_options();
const smartlist_t *the_nodes;
const node_t *node=NULL;
connections = get_connection_array();
/* Count how many connections are waiting for a circuit to be built.
* We use this for log messages now, but in the future we may depend on it.
*/
SMARTLIST_FOREACH(connections, connection_t *, conn,
{
if (ap_stream_wants_exit_attention(conn))
++n_pending_connections;
});
// log_fn(LOG_DEBUG, "Choosing exit node; %d connections are pending",
// n_pending_connections);
/* Now we count, for each of the routers in the directory, how many
* of the pending connections could possibly exit from that
* router (n_supported[i]). (We can't be sure about cases where we
* don't know the IP address of the pending connection.)
*
* -1 means "Don't use this router at all."
*/
the_nodes = nodelist_get_list();
n_supported = tor_malloc(sizeof(int)*smartlist_len(the_nodes));
SMARTLIST_FOREACH_BEGIN(the_nodes, const node_t *, node) {
const int i = node_sl_idx;
if (router_digest_is_me(node->identity)) {
n_supported[i] = -1;
// log_fn(LOG_DEBUG,"Skipping node %s -- it's me.", router->nickname);
/* XXX there's probably a reverse predecessor attack here, but
* it's slow. should we take this out? -RD
*/
continue;
}
if (!node_has_descriptor(node)) {
n_supported[i] = -1;
continue;
}
if (!node->is_running || node->is_bad_exit) {
n_supported[i] = -1;
continue; /* skip routers that are known to be down or bad exits */
}
if (node_get_purpose(node) != ROUTER_PURPOSE_GENERAL) {
/* never pick a non-general node as a random exit. */
n_supported[i] = -1;
continue;
}
if (routerset_contains_node(options->ExcludeExitNodesUnion_, node)) {
n_supported[i] = -1;
continue; /* user asked us not to use it, no matter what */
}
if (options->ExitNodes &&
!routerset_contains_node(options->ExitNodes, node)) {
n_supported[i] = -1;
continue; /* not one of our chosen exit nodes */
}
if (node_is_unreliable(node, need_uptime, need_capacity, 0)) {
n_supported[i] = -1;
continue; /* skip routers that are not suitable. Don't worry if
* this makes us reject all the possible routers: if so,
* we'll retry later in this function with need_update and
* need_capacity set to 0. */
}
if (!(node->is_valid || options->AllowInvalid_ & ALLOW_INVALID_EXIT)) {
/* if it's invalid and we don't want it */
n_supported[i] = -1;
// log_fn(LOG_DEBUG,"Skipping node %s (index %d) -- invalid router.",
// router->nickname, i);
continue; /* skip invalid routers */
}
if (options->ExcludeSingleHopRelays &&
node_allows_single_hop_exits(node)) {
n_supported[i] = -1;
continue;
}
if (node_exit_policy_rejects_all(node)) {
n_supported[i] = -1;
// log_fn(LOG_DEBUG,"Skipping node %s (index %d) -- it rejects all.",
// router->nickname, i);
continue; /* skip routers that reject all */
}
n_supported[i] = 0;
/* iterate over connections */
SMARTLIST_FOREACH_BEGIN(connections, connection_t *, conn) {
if (!ap_stream_wants_exit_attention(conn))
continue; /* Skip everything but APs in CIRCUIT_WAIT */
if (connection_ap_can_use_exit(TO_ENTRY_CONN(conn), node)) {
++n_supported[i];
// log_fn(LOG_DEBUG,"%s is supported. n_supported[%d] now %d.",
// router->nickname, i, n_supported[i]);
} else {
// log_fn(LOG_DEBUG,"%s (index %d) would reject this stream.",
// router->nickname, i);
}
} SMARTLIST_FOREACH_END(conn);
if (n_pending_connections > 0 && n_supported[i] == 0) {
/* Leave best_support at -1 if that's where it is, so we can
* distinguish it later. */
continue;
}
if (n_supported[i] > best_support) {
/* If this router is better than previous ones, remember its index
* and goodness, and start counting how many routers are this good. */
best_support = n_supported[i]; n_best_support=1;
// log_fn(LOG_DEBUG,"%s is new best supported option so far.",
// router->nickname);
} else if (n_supported[i] == best_support) {
/* If this router is _as good_ as the best one, just increment the
* count of equally good routers.*/
++n_best_support;
}
} SMARTLIST_FOREACH_END(node);
log_info(LD_CIRC,
"Found %d servers that might support %d/%d pending connections.",
n_best_support, best_support >= 0 ? best_support : 0,
n_pending_connections);
/* If any routers definitely support any pending connections, choose one
* at random. */
if (best_support > 0) {
smartlist_t *supporting = smartlist_new();
SMARTLIST_FOREACH(the_nodes, const node_t *, node, {
if (n_supported[node_sl_idx] == best_support)
smartlist_add(supporting, (void*)node);
});
node = node_sl_choose_by_bandwidth(supporting, WEIGHT_FOR_EXIT);
smartlist_free(supporting);
} else {
/* Either there are no pending connections, or no routers even seem to
* possibly support any of them. Choose a router at random that satisfies
* at least one predicted exit port. */
int attempt;
smartlist_t *needed_ports, *supporting;
if (best_support == -1) {
if (need_uptime || need_capacity) {
log_info(LD_CIRC,
"We couldn't find any live%s%s routers; falling back "
"to list of all routers.",
need_capacity?", fast":"",
need_uptime?", stable":"");
tor_free(n_supported);
return choose_good_exit_server_general(0, 0);
}
log_notice(LD_CIRC, "All routers are down or won't exit%s -- "
"choosing a doomed exit at random.",
options->ExcludeExitNodesUnion_ ? " or are Excluded" : "");
}
supporting = smartlist_new();
needed_ports = circuit_get_unhandled_ports(time(NULL));
for (attempt = 0; attempt < 2; attempt++) {
/* try once to pick only from routers that satisfy a needed port,
* then if there are none, pick from any that support exiting. */
SMARTLIST_FOREACH_BEGIN(the_nodes, const node_t *, node) {
if (n_supported[node_sl_idx] != -1 &&
(attempt || node_handles_some_port(node, needed_ports))) {
// log_fn(LOG_DEBUG,"Try %d: '%s' is a possibility.",
// try, router->nickname);
smartlist_add(supporting, (void*)node);
}
} SMARTLIST_FOREACH_END(node);
node = node_sl_choose_by_bandwidth(supporting, WEIGHT_FOR_EXIT);
if (node)
break;
smartlist_clear(supporting);
/* If we reach this point, we can't actually support any unhandled
* predicted ports, so clear all the remaining ones. */
if (smartlist_len(needed_ports))
rep_hist_remove_predicted_ports(needed_ports);
}
SMARTLIST_FOREACH(needed_ports, uint16_t *, cp, tor_free(cp));
smartlist_free(needed_ports);
smartlist_free(supporting);
}
tor_free(n_supported);
if (node) {
log_info(LD_CIRC, "Chose exit server '%s'", node_describe(node));
return node;
}
if (options->ExitNodes) {
log_warn(LD_CIRC,
"No specified %sexit routers seem to be running: "
"can't choose an exit.",
options->ExcludeExitNodesUnion_ ? "non-excluded " : "");
}
return NULL;
}
/** Return a pointer to a suitable router to be the exit node for the
* circuit of purpose <b>purpose</b> that we're about to build (or NULL
* if no router is suitable).
*
* For general-purpose circuits, pass it off to
* choose_good_exit_server_general()
*
* For client-side rendezvous circuits, choose a random node, weighted
* toward the preferences in 'options'.
*/
static const node_t *
choose_good_exit_server(uint8_t purpose,
int need_uptime, int need_capacity, int is_internal)
{
const or_options_t *options = get_options();
router_crn_flags_t flags = CRN_NEED_DESC;
if (need_uptime)
flags |= CRN_NEED_UPTIME;
if (need_capacity)
flags |= CRN_NEED_CAPACITY;
switch (purpose) {
case CIRCUIT_PURPOSE_C_GENERAL:
if (options->AllowInvalid_ & ALLOW_INVALID_MIDDLE)
flags |= CRN_ALLOW_INVALID;
if (is_internal) /* pick it like a middle hop */
return router_choose_random_node(NULL, options->ExcludeNodes, flags);
else
return choose_good_exit_server_general(need_uptime,need_capacity);
case CIRCUIT_PURPOSE_C_ESTABLISH_REND:
if (options->AllowInvalid_ & ALLOW_INVALID_RENDEZVOUS)
flags |= CRN_ALLOW_INVALID;
return router_choose_random_node(NULL, options->ExcludeNodes, flags);
}
log_warn(LD_BUG,"Unhandled purpose %d", purpose);
tor_fragile_assert();
return NULL;
}
/** Log a warning if the user specified an exit for the circuit that
* has been excluded from use by ExcludeNodes or ExcludeExitNodes. */
static void
warn_if_last_router_excluded(origin_circuit_t *circ, const extend_info_t *exit)
{
const or_options_t *options = get_options();
routerset_t *rs = options->ExcludeNodes;
const char *description;
uint8_t purpose = circ->base_.purpose;
if (circ->build_state->onehop_tunnel)
return;
switch (purpose)
{
default:
case CIRCUIT_PURPOSE_OR:
case CIRCUIT_PURPOSE_INTRO_POINT:
case CIRCUIT_PURPOSE_REND_POINT_WAITING:
case CIRCUIT_PURPOSE_REND_ESTABLISHED:
log_warn(LD_BUG, "Called on non-origin circuit (purpose %d, %s)",
(int)purpose,
circuit_purpose_to_string(purpose));
return;
case CIRCUIT_PURPOSE_C_GENERAL:
if (circ->build_state->is_internal)
return;
description = "requested exit node";
rs = options->ExcludeExitNodesUnion_;
break;
case CIRCUIT_PURPOSE_C_INTRODUCING:
case CIRCUIT_PURPOSE_C_INTRODUCE_ACK_WAIT:
case CIRCUIT_PURPOSE_C_INTRODUCE_ACKED:
case CIRCUIT_PURPOSE_S_ESTABLISH_INTRO:
case CIRCUIT_PURPOSE_S_CONNECT_REND:
case CIRCUIT_PURPOSE_S_REND_JOINED:
case CIRCUIT_PURPOSE_TESTING:
return;
case CIRCUIT_PURPOSE_C_ESTABLISH_REND:
case CIRCUIT_PURPOSE_C_REND_READY:
case CIRCUIT_PURPOSE_C_REND_READY_INTRO_ACKED:
case CIRCUIT_PURPOSE_C_REND_JOINED:
description = "chosen rendezvous point";
break;
case CIRCUIT_PURPOSE_CONTROLLER:
rs = options->ExcludeExitNodesUnion_;
description = "controller-selected circuit target";
break;
}
if (routerset_contains_extendinfo(rs, exit)) {
/* We should never get here if StrictNodes is set to 1. */
if (options->StrictNodes) {
log_warn(LD_BUG, "Using %s '%s' which is listed in ExcludeNodes%s, "
"even though StrictNodes is set. Please report. "
"(Circuit purpose: %s)",
description, extend_info_describe(exit),
rs==options->ExcludeNodes?"":" or ExcludeExitNodes",
circuit_purpose_to_string(purpose));
} else {
log_warn(LD_CIRC, "Using %s '%s' which is listed in "
"ExcludeNodes%s, because no better options were available. To "
"prevent this (and possibly break your Tor functionality), "
"set the StrictNodes configuration option. "
"(Circuit purpose: %s)",
description, extend_info_describe(exit),
rs==options->ExcludeNodes?"":" or ExcludeExitNodes",
circuit_purpose_to_string(purpose));
}
circuit_log_path(LOG_WARN, LD_CIRC, circ);
}
return;
}
/** Decide a suitable length for circ's cpath, and pick an exit
* router (or use <b>exit</b> if provided). Store these in the
* cpath. Return 0 if ok, -1 if circuit should be closed. */
static int
onion_pick_cpath_exit(origin_circuit_t *circ, extend_info_t *exit)
{
cpath_build_state_t *state = circ->build_state;
if (state->onehop_tunnel) {
log_debug(LD_CIRC, "Launching a one-hop circuit for dir tunnel.");
state->desired_path_len = 1;
} else {
int r = new_route_len(circ->base_.purpose, exit, nodelist_get_list());
if (r < 1) /* must be at least 1 */
return -1;
state->desired_path_len = r;
}
if (exit) { /* the circuit-builder pre-requested one */
warn_if_last_router_excluded(circ, exit);
log_info(LD_CIRC,"Using requested exit node '%s'",
extend_info_describe(exit));
exit = extend_info_dup(exit);
} else { /* we have to decide one */
const node_t *node =
choose_good_exit_server(circ->base_.purpose, state->need_uptime,
state->need_capacity, state->is_internal);
if (!node) {
log_warn(LD_CIRC,"failed to choose an exit server");
return -1;
}
exit = extend_info_from_node(node, 0);
tor_assert(exit);
}
state->chosen_exit = exit;
return 0;
}
/** Give <b>circ</b> a new exit destination to <b>exit</b>, and add a
* hop to the cpath reflecting this. Don't send the next extend cell --
* the caller will do this if it wants to.
*/
int
circuit_append_new_exit(origin_circuit_t *circ, extend_info_t *exit)
{
cpath_build_state_t *state;
tor_assert(exit);
tor_assert(circ);
state = circ->build_state;
tor_assert(state);
extend_info_free(state->chosen_exit);
state->chosen_exit = extend_info_dup(exit);
++circ->build_state->desired_path_len;
onion_append_hop(&circ->cpath, exit);
return 0;
}
/** Take an open <b>circ</b>, and add a new hop at the end, based on
* <b>info</b>. Set its state back to CIRCUIT_STATE_BUILDING, and then
* send the next extend cell to begin connecting to that hop.
*/
int
circuit_extend_to_new_exit(origin_circuit_t *circ, extend_info_t *exit)
{
int err_reason = 0;
warn_if_last_router_excluded(circ, exit);
circuit_append_new_exit(circ, exit);
circuit_set_state(TO_CIRCUIT(circ), CIRCUIT_STATE_BUILDING);
if ((err_reason = circuit_send_next_onion_skin(circ))<0) {
log_warn(LD_CIRC, "Couldn't extend circuit to new point %s.",
extend_info_describe(exit));
circuit_mark_for_close(TO_CIRCUIT(circ), -err_reason);
return -1;
}
/* Set timestamp_dirty, so we can check it for path use bias */
if (!circ->base_.timestamp_dirty)
circ->base_.timestamp_dirty = time(NULL);
return 0;
}
/** Return the number of routers in <b>routers</b> that are currently up
* and available for building circuits through.
*/
static int
count_acceptable_nodes(smartlist_t *nodes)
{
int num=0;
SMARTLIST_FOREACH_BEGIN(nodes, const node_t *, node) {
// log_debug(LD_CIRC,
// "Contemplating whether router %d (%s) is a new option.",
// i, r->nickname);
if (! node->is_running)
// log_debug(LD_CIRC,"Nope, the directory says %d is not running.",i);
continue;
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. */
++num;
} SMARTLIST_FOREACH_END(node);
// log_debug(LD_CIRC,"I like %d. num_acceptable_routers now %d.",i, num);
return num;
}
/** Add <b>new_hop</b> to the end of the doubly-linked-list <b>head_ptr</b>.
* This function is used to extend cpath by another hop.
*/
void
onion_append_to_cpath(crypt_path_t **head_ptr, crypt_path_t *new_hop)
{
if (*head_ptr) {
new_hop->next = (*head_ptr);
new_hop->prev = (*head_ptr)->prev;
(*head_ptr)->prev->next = new_hop;
(*head_ptr)->prev = new_hop;
} else {
*head_ptr = new_hop;
new_hop->prev = new_hop->next = new_hop;
}
}
/** A helper function used by onion_extend_cpath(). Use <b>purpose</b>
* and <b>state</b> and the cpath <b>head</b> (currently populated only
* to length <b>cur_len</b> to decide a suitable middle hop for a
* circuit. In particular, make sure we don't pick the exit node or its
* family, and make sure we don't duplicate any previous nodes or their
* families. */
static const node_t *
choose_good_middle_server(uint8_t purpose,
cpath_build_state_t *state,
crypt_path_t *head,
int cur_len)
{
int i;
const node_t *r, *choice;
crypt_path_t *cpath;
smartlist_t *excluded;
const or_options_t *options = get_options();
router_crn_flags_t flags = CRN_NEED_DESC;
tor_assert(CIRCUIT_PURPOSE_MIN_ <= purpose &&
purpose <= CIRCUIT_PURPOSE_MAX_);
log_debug(LD_CIRC, "Contemplating intermediate hop: random choice.");
excluded = smartlist_new();
if ((r = build_state_get_exit_node(state))) {
nodelist_add_node_and_family(excluded, r);
}
for (i = 0, cpath = head; 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);
}
}
if (state->need_uptime)
flags |= CRN_NEED_UPTIME;
if (state->need_capacity)
flags |= CRN_NEED_CAPACITY;
if (options->AllowInvalid_ & ALLOW_INVALID_MIDDLE)
flags |= CRN_ALLOW_INVALID;
choice = router_choose_random_node(excluded, options->ExcludeNodes, flags);
smartlist_free(excluded);
return choice;
}
/** Pick a good entry server for the circuit to be built according to
* <b>state</b>. Don't reuse a chosen exit (if any), don't use this
* router (if we're an OR), and respect firewall settings; if we're
* configured to use entry guards, return one.
*
* If <b>state</b> is NULL, we're choosing a router to serve as an entry
* guard, not for any particular circuit.
*/
/* XXXX024 I'd like to have this be static again, but entrynodes.c needs it. */
const node_t *
choose_good_entry_server(uint8_t purpose, cpath_build_state_t *state)
{
const node_t *choice;
smartlist_t *excluded;
const or_options_t *options = get_options();
router_crn_flags_t flags = CRN_NEED_GUARD|CRN_NEED_DESC;
const node_t *node;
if (state && options->UseEntryGuards &&
(purpose != CIRCUIT_PURPOSE_TESTING || options->BridgeRelay)) {
/* 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. */
return choose_random_entry(state);
}
excluded = smartlist_new();
if (state && (node = build_state_get_exit_node(state))) {
/* Exclude the exit node from the state, if we have one. Also exclude its
* family. */
nodelist_add_node_and_family(excluded, node);
}
if (firewall_is_fascist_or()) {
/* Exclude all ORs that we can't reach through our firewall */
smartlist_t *nodes = nodelist_get_list();
SMARTLIST_FOREACH(nodes, const node_t *, node, {
if (!fascist_firewall_allows_node(node))
smartlist_add(excluded, (void*)node);
});
}
/* and exclude current entry guards and their families, if applicable */
if (options->UseEntryGuards) {
SMARTLIST_FOREACH(get_entry_guards(), const entry_guard_t *, entry,
{
if ((node = node_get_by_id(entry->identity))) {
nodelist_add_node_and_family(excluded, node);
}
});
}
if (state) {
if (state->need_uptime)
flags |= CRN_NEED_UPTIME;
if (state->need_capacity)
flags |= CRN_NEED_CAPACITY;
}
if (options->AllowInvalid_ & ALLOW_INVALID_ENTRY)
flags |= CRN_ALLOW_INVALID;
choice = router_choose_random_node(excluded, options->ExcludeNodes, flags);
smartlist_free(excluded);
return choice;
}
/** Return the first non-open hop in cpath, or return NULL if all
* hops are open. */
static crypt_path_t *
onion_next_hop_in_cpath(crypt_path_t *cpath)
{
crypt_path_t *hop = cpath;
do {
if (hop->state != CPATH_STATE_OPEN)
return hop;
hop = hop->next;
} while (hop != cpath);
return NULL;
}
/** Choose a suitable next hop in the cpath <b>head_ptr</b>,
* based on <b>state</b>. Append the hop info to head_ptr.
*/
static int
onion_extend_cpath(origin_circuit_t *circ)
{
uint8_t purpose = circ->base_.purpose;
cpath_build_state_t *state = circ->build_state;
int cur_len = circuit_get_cpath_len(circ);
extend_info_t *info = NULL;
if (cur_len >= state->desired_path_len) {
log_debug(LD_CIRC, "Path is complete: %d steps long",
state->desired_path_len);
return 1;
}
log_debug(LD_CIRC, "Path is %d long; we want %d", cur_len,
state->desired_path_len);
if (cur_len == state->desired_path_len - 1) { /* Picking last node */
info = extend_info_dup(state->chosen_exit);
} else if (cur_len == 0) { /* picking first node */
const node_t *r = choose_good_entry_server(purpose, state);
if (r) {
/* If we're a client, use the preferred address rather than the
primary address, for potentially connecting to an IPv6 OR
port. */
info = extend_info_from_node(r, server_mode(get_options()) == 0);
tor_assert(info);
}
} else {
const node_t *r =
choose_good_middle_server(purpose, state, circ->cpath, cur_len);
if (r) {
info = extend_info_from_node(r, 0);
tor_assert(info);
}
}
if (!info) {
log_warn(LD_CIRC,"Failed to find node for hop %d of our path. Discarding "
"this circuit.", cur_len);
return -1;
}
log_debug(LD_CIRC,"Chose router %s for hop %d (exit is %s)",
extend_info_describe(info),
cur_len+1, build_state_get_exit_nickname(state));
onion_append_hop(&circ->cpath, info);
extend_info_free(info);
return 0;
}
/** Create a new hop, annotate it with information about its
* corresponding router <b>choice</b>, and append it to the
* end of the cpath <b>head_ptr</b>. */
static int
onion_append_hop(crypt_path_t **head_ptr, extend_info_t *choice)
{
crypt_path_t *hop = tor_malloc_zero(sizeof(crypt_path_t));
/* link hop into the cpath, at the end. */
onion_append_to_cpath(head_ptr, hop);
hop->magic = CRYPT_PATH_MAGIC;
hop->state = CPATH_STATE_CLOSED;
hop->extend_info = extend_info_dup(choice);
hop->package_window = circuit_initial_package_window();
hop->deliver_window = CIRCWINDOW_START;
return 0;
}
/** Allocate a new extend_info object based on the various arguments. */
extend_info_t *
extend_info_new(const char *nickname, const char *digest,
crypto_pk_t *onion_key,
const tor_addr_t *addr, uint16_t port)
{
extend_info_t *info = tor_malloc_zero(sizeof(extend_info_t));
memcpy(info->identity_digest, digest, DIGEST_LEN);
if (nickname)
strlcpy(info->nickname, nickname, sizeof(info->nickname));
if (onion_key)
info->onion_key = crypto_pk_dup_key(onion_key);
tor_addr_copy(&info->addr, addr);
info->port = port;
return info;
}
/** Allocate and return a new extend_info that can be used to build a
* circuit to or through the node <b>node</b>. Use the primary address
* of the node (i.e. its IPv4 address) unless
* <b>for_direct_connect</b> is true, in which case the preferred
* address is used instead. May return NULL if there is not enough
* info about <b>node</b> to extend to it--for example, if there is no
* routerinfo_t or microdesc_t.
**/
extend_info_t *
extend_info_from_node(const node_t *node, int for_direct_connect)
{
tor_addr_port_t ap;
if (node->ri == NULL && (node->rs == NULL || node->md == NULL))
return NULL;
if (for_direct_connect)
node_get_pref_orport(node, &ap);
else
node_get_prim_orport(node, &ap);
log_debug(LD_CIRC, "using %s for %s",
fmt_addrport(&ap.addr, ap.port),
node->ri ? node->ri->nickname : node->rs->nickname);
if (node->ri)
return extend_info_new(node->ri->nickname,
node->identity,
node->ri->onion_pkey,
&ap.addr,
ap.port);
else if (node->rs && node->md)
return extend_info_new(node->rs->nickname,
node->identity,
node->md->onion_pkey,
&ap.addr,
ap.port);
else
return NULL;
}
/** Release storage held by an extend_info_t struct. */
void
extend_info_free(extend_info_t *info)
{
if (!info)
return;
crypto_pk_free(info->onion_key);
tor_free(info);
}
/** Allocate and return a new extend_info_t with the same contents as
* <b>info</b>. */
extend_info_t *
extend_info_dup(extend_info_t *info)
{
extend_info_t *newinfo;
tor_assert(info);
newinfo = tor_malloc(sizeof(extend_info_t));
memcpy(newinfo, info, sizeof(extend_info_t));
if (info->onion_key)
newinfo->onion_key = crypto_pk_dup_key(info->onion_key);
else
newinfo->onion_key = NULL;
return newinfo;
}
/** Return the routerinfo_t for the chosen exit router in <b>state</b>.
* If there is no chosen exit, or if we don't know the routerinfo_t for
* the chosen exit, return NULL.
*/
const node_t *
build_state_get_exit_node(cpath_build_state_t *state)
{
if (!state || !state->chosen_exit)
return NULL;
return node_get_by_id(state->chosen_exit->identity_digest);
}
/** Return the nickname for the chosen exit router in <b>state</b>. If
* there is no chosen exit, or if we don't know the routerinfo_t for the
* chosen exit, return NULL.
*/
const char *
build_state_get_exit_nickname(cpath_build_state_t *state)
{
if (!state || !state->chosen_exit)
return NULL;
return state->chosen_exit->nickname;
}
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