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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) 2007-2017, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* \file entrynodes.c
* \brief Code to manage our fixed first nodes for various functions.
*
* Entry nodes can be guards (for general use) or bridges (for censorship
* circumvention).
*
* In general, we use entry guards to prevent traffic-sampling attacks:
* if we chose every circuit independently, an adversary controlling
* some fraction of paths on the network would observe a sample of every
* user's traffic. Using guards gives users a chance of not being
* profiled.
*
* The current entry guard selection code is designed to try to avoid
* _ever_ trying every guard on the network, to try to stick to guards
* that we've used before, to handle hostile/broken networks, and
* to behave sanely when the network goes up and down.
*
* Our algorithm works as follows: First, we maintain a SAMPLE of guards
* we've seen in the networkstatus consensus. We maintain this sample
* over time, and store it persistently; it is chosen without reference
* to our configuration or firewall rules. Guards remain in the sample
* as they enter and leave the consensus. We expand this sample as
* needed, up to a maximum size.
*
* As a subset of the sample, we maintain a FILTERED SET of the guards
* that we would be willing to use if we could connect to them. The
* filter removes all the guards that we're excluding because they're
* bridges (or not bridges), because we have restrictive firewall rules,
* because of ExcludeNodes, because we of path bias restrictions,
* because they're absent from the network at present, and so on.
*
* As a subset of the filtered set, we keep a REACHABLE FILTERED SET
* (also called a "usable filtered set") of those guards that we call
* "reachable" or "maybe reachable". A guard is reachable if we've
* connected to it more recently than we've failed. A guard is "maybe
* reachable" if we have never tried to connect to it, or if we
* failed to connect to it so long ago that we no longer think our
* failure means it's down.
*
* As a persistent ordered list whose elements are taken from the
* sampled set, we track a CONFIRMED GUARDS LIST. A guard becomes
* confirmed when we successfully build a circuit through it, and decide
* to use that circuit. We order the guards on this list by the order
* in which they became confirmed.
*
* And as a final group, we have an ordered list of PRIMARY GUARDS,
* whose elements are taken from the filtered set. We prefer
* confirmed guards to non-confirmed guards for this list, and place
* other restrictions on it. The primary guards are the ones that we
* connect to "when nothing is wrong" -- circuits through them can be used
* immediately.
*
* To build circuits, we take a primary guard if possible -- or a
* reachable filtered confirmed guard if no primary guard is possible --
* or a random reachable filtered guard otherwise. If the guard is
* primary, we can use the circuit immediately on success. Otherwise,
* the guard is now "pending" -- we won't use its circuit unless all
* of the circuits we're trying to build through better guards have
* definitely failed.
*
* While we're building circuits, we track a little "guard state" for
* each circuit. We use this to keep track of whether the circuit is
* one that we can use as soon as it's done, or whether it's one that
* we should keep around to see if we can do better. In the latter case,
* a periodic call to entry_guards_upgrade_waiting_circuits() will
* eventually upgrade it.
**/
/* DOCDOC -- expand this.
*
* Information invariants:
*
* [x] whenever a guard becomes unreachable, clear its usable_filtered flag.
*
* [x] Whenever a guard becomes reachable or maybe-reachable, if its filtered
* flag is set, set its usable_filtered flag.
*
* [x] Whenever we get a new consensus, call update_from_consensus(). (LATER.)
*
* [x] Whenever the configuration changes in a relevant way, update the
* filtered/usable flags. (LATER.)
*
* [x] Whenever we add a guard to the sample, make sure its filtered/usable
* flags are set as possible.
*
* [x] Whenever we remove a guard from the sample, remove it from the primary
* and confirmed lists.
*
* [x] When we make a guard confirmed, update the primary list.
*
* [x] When we make a guard filtered or unfiltered, update the primary list.
*
* [x] When we are about to pick a guard, make sure that the primary list is
* full.
*
* [x] Before calling sample_reachable_filtered_entry_guards(), make sure
* that the filtered, primary, and confirmed flags are up-to-date.
*
* [x] Call entry_guard_consider_retry every time we are about to check
* is_usable_filtered or is_reachable, and every time we set
* is_filtered to 1.
*
* [x] Call entry_guards_changed_for_guard_selection() whenever we update
* a persistent field.
*/
#define ENTRYNODES_PRIVATE
#include "or.h"
#include "channel.h"
#include "bridges.h"
#include "circpathbias.h"
#include "circuitbuild.h"
#include "circuitlist.h"
#include "circuituse.h"
#include "circuitstats.h"
#include "config.h"
#include "confparse.h"
#include "connection.h"
#include "control.h"
#include "crypto_rand.h"
#include "directory.h"
#include "entrynodes.h"
#include "main.h"
#include "microdesc.h"
#include "networkstatus.h"
#include "nodelist.h"
#include "policies.h"
#include "router.h"
#include "routerlist.h"
#include "routerparse.h"
#include "routerset.h"
#include "transports.h"
#include "statefile.h"
/** A list of existing guard selection contexts. */
static smartlist_t *guard_contexts = NULL;
/** The currently enabled guard selection context. */
static guard_selection_t *curr_guard_context = NULL;
/** A value of 1 means that at least one context has changed,
* and those changes need to be flushed to disk. */
static int entry_guards_dirty = 0;
static void entry_guard_set_filtered_flags(const or_options_t *options,
guard_selection_t *gs,
entry_guard_t *guard);
static void pathbias_check_use_success_count(entry_guard_t *guard);
static void pathbias_check_close_success_count(entry_guard_t *guard);
static int node_is_possible_guard(const node_t *node);
static int node_passes_guard_filter(const or_options_t *options,
const node_t *node);
static entry_guard_t *entry_guard_add_to_sample_impl(guard_selection_t *gs,
const uint8_t *rsa_id_digest,
const char *nickname,
const tor_addr_port_t *bridge_addrport);
static entry_guard_t *get_sampled_guard_by_bridge_addr(guard_selection_t *gs,
const tor_addr_port_t *addrport);
static int entry_guard_obeys_restriction(const entry_guard_t *guard,
const entry_guard_restriction_t *rst);
/** Return 0 if we should apply guardfraction information found in the
* consensus. A specific consensus can be specified with the
* <b>ns</b> argument, if NULL the most recent one will be picked.*/
int
should_apply_guardfraction(const networkstatus_t *ns)
{
/* We need to check the corresponding torrc option and the consensus
* parameter if we need to. */
const or_options_t *options = get_options();
/* If UseGuardFraction is 'auto' then check the same-named consensus
* parameter. If the consensus parameter is not present, default to
* "off". */
if (options->UseGuardFraction == -1) {
return networkstatus_get_param(ns, "UseGuardFraction",
0, /* default to "off" */
0, 1);
}
return options->UseGuardFraction;
}
/** Return true iff we know a preferred descriptor for <b>guard</b> */
static int
guard_has_descriptor(const entry_guard_t *guard)
{
const node_t *node = node_get_by_id(guard->identity);
if (!node)
return 0;
return node_has_preferred_descriptor(node, 1);
}
/**
* Try to determine the correct type for a selection named "name",
* if <b>type</b> is GS_TYPE_INFER.
*/
STATIC guard_selection_type_t
guard_selection_infer_type(guard_selection_type_t type,
const char *name)
{
if (type == GS_TYPE_INFER) {
if (!strcmp(name, "bridges"))
type = GS_TYPE_BRIDGE;
else if (!strcmp(name, "restricted"))
type = GS_TYPE_RESTRICTED;
else
type = GS_TYPE_NORMAL;
}
return type;
}
/**
* Allocate and return a new guard_selection_t, with the name <b>name</b>.
*/
STATIC guard_selection_t *
guard_selection_new(const char *name,
guard_selection_type_t type)
{
guard_selection_t *gs;
type = guard_selection_infer_type(type, name);
gs = tor_malloc_zero(sizeof(*gs));
gs->name = tor_strdup(name);
gs->type = type;
gs->sampled_entry_guards = smartlist_new();
gs->confirmed_entry_guards = smartlist_new();
gs->primary_entry_guards = smartlist_new();
return gs;
}
/**
* Return the guard selection called <b>name</b>. If there is none, and
* <b>create_if_absent</b> is true, then create and return it. If there
* is none, and <b>create_if_absent</b> is false, then return NULL.
*/
STATIC guard_selection_t *
get_guard_selection_by_name(const char *name,
guard_selection_type_t type,
int create_if_absent)
{
if (!guard_contexts) {
guard_contexts = smartlist_new();
}
SMARTLIST_FOREACH_BEGIN(guard_contexts, guard_selection_t *, gs) {
if (!strcmp(gs->name, name))
return gs;
} SMARTLIST_FOREACH_END(gs);
if (! create_if_absent)
return NULL;
log_debug(LD_GUARD, "Creating a guard selection called %s", name);
guard_selection_t *new_selection = guard_selection_new(name, type);
smartlist_add(guard_contexts, new_selection);
return new_selection;
}
/**
* Allocate the first guard context that we're planning to use,
* and make it the current context.
*/
static void
create_initial_guard_context(void)
{
tor_assert(! curr_guard_context);
if (!guard_contexts) {
guard_contexts = smartlist_new();
}
guard_selection_type_t type = GS_TYPE_INFER;
const char *name = choose_guard_selection(
get_options(),
networkstatus_get_live_consensus(approx_time()),
NULL,
&type);
tor_assert(name); // "name" can only be NULL if we had an old name.
tor_assert(type != GS_TYPE_INFER);
log_notice(LD_GUARD, "Starting with guard context \"%s\"", name);
curr_guard_context = get_guard_selection_by_name(name, type, 1);
}
/** Get current default guard_selection_t, creating it if necessary */
guard_selection_t *
get_guard_selection_info(void)
{
if (!curr_guard_context) {
create_initial_guard_context();
}
return curr_guard_context;
}
/** Return a statically allocated human-readable description of <b>guard</b>
*/
const char *
entry_guard_describe(const entry_guard_t *guard)
{
static char buf[256];
tor_snprintf(buf, sizeof(buf),
"%s ($%s)",
strlen(guard->nickname) ? guard->nickname : "[bridge]",
hex_str(guard->identity, DIGEST_LEN));
return buf;
}
/** Return <b>guard</b>'s 20-byte RSA identity digest */
const char *
entry_guard_get_rsa_id_digest(const entry_guard_t *guard)
{
return guard->identity;
}
/** Return the pathbias state associated with <b>guard</b>. */
guard_pathbias_t *
entry_guard_get_pathbias_state(entry_guard_t *guard)
{
return &guard->pb;
}
HANDLE_IMPL(entry_guard, entry_guard_t, ATTR_UNUSED STATIC)
/** Return an interval betweeen 'now' and 'max_backdate' seconds in the past,
* chosen uniformly at random. We use this before recording persistent
* dates, so that we aren't leaking exactly when we recorded it.
*/
MOCK_IMPL(STATIC time_t,
randomize_time,(time_t now, time_t max_backdate))
{
tor_assert(max_backdate > 0);
time_t earliest = now - max_backdate;
time_t latest = now;
if (earliest <= 0)
earliest = 1;
if (latest <= earliest)
latest = earliest + 1;
return crypto_rand_time_range(earliest, latest);
}
/**
* @name parameters for networkstatus algorithm
*
* These parameters are taken from the consensus; some are overrideable in
* the torrc.
*/
/**@{*/
/**
* We never let our sampled guard set grow larger than this fraction
* of the guards on the network.
*/
STATIC double
get_max_sample_threshold(void)
{
int32_t pct =
networkstatus_get_param(NULL, "guard-max-sample-threshold-percent",
DFLT_MAX_SAMPLE_THRESHOLD_PERCENT,
1, 100);
return pct / 100.0;
}
/**
* We never let our sampled guard set grow larger than this number.
*/
STATIC int
get_max_sample_size_absolute(void)
{
return (int) networkstatus_get_param(NULL, "guard-max-sample-size",
DFLT_MAX_SAMPLE_SIZE,
1, INT32_MAX);
}
/**
* We always try to make our sample contain at least this many guards.
*/
STATIC int
get_min_filtered_sample_size(void)
{
return networkstatus_get_param(NULL, "guard-min-filtered-sample-size",
DFLT_MIN_FILTERED_SAMPLE_SIZE,
1, INT32_MAX);
}
/**
* If a guard is unlisted for this many days in a row, we remove it.
*/
STATIC int
get_remove_unlisted_guards_after_days(void)
{
return networkstatus_get_param(NULL,
"guard-remove-unlisted-guards-after-days",
DFLT_REMOVE_UNLISTED_GUARDS_AFTER_DAYS,
1, 365*10);
}
/**
* We remove unconfirmed guards from the sample after this many days,
* regardless of whether they are listed or unlisted.
*/
STATIC int
get_guard_lifetime(void)
{
if (get_options()->GuardLifetime >= 86400)
return get_options()->GuardLifetime;
int32_t days;
days = networkstatus_get_param(NULL,
"guard-lifetime-days",
DFLT_GUARD_LIFETIME_DAYS, 1, 365*10);
return days * 86400;
}
/**
* We remove confirmed guards from the sample if they were sampled
* GUARD_LIFETIME_DAYS ago and confirmed this many days ago.
*/
STATIC int
get_guard_confirmed_min_lifetime(void)
{
if (get_options()->GuardLifetime >= 86400)
return get_options()->GuardLifetime;
int32_t days;
days = networkstatus_get_param(NULL, "guard-confirmed-min-lifetime-days",
DFLT_GUARD_CONFIRMED_MIN_LIFETIME_DAYS,
1, 365*10);
return days * 86400;
}
/**
* How many guards do we try to keep on our primary guard list?
*/
STATIC int
get_n_primary_guards(void)
{
/* If the user has explicitly configured the number of primary guards, do
* what the user wishes to do */
const int configured_primaries = get_options()->NumPrimaryGuards;
if (configured_primaries) {
return configured_primaries;
}
/* otherwise check for consensus parameter and if that's not set either, just
* use the default value. */
return networkstatus_get_param(NULL,
"guard-n-primary-guards",
DFLT_N_PRIMARY_GUARDS, 1, INT32_MAX);
}
/**
* Return the number of the live primary guards we should look at when
* making a circuit.
*/
STATIC int
get_n_primary_guards_to_use(guard_usage_t usage)
{
int configured;
const char *param_name;
int param_default;
/* If the user has explicitly configured the amount of guards, use
that. Otherwise, fall back to the default value. */
if (usage == GUARD_USAGE_DIRGUARD) {
configured = get_options()->NumDirectoryGuards;
param_name = "guard-n-primary-dir-guards-to-use";
param_default = DFLT_N_PRIMARY_DIR_GUARDS_TO_USE;
} else {
configured = get_options()->NumEntryGuards;
param_name = "guard-n-primary-guards-to-use";
param_default = DFLT_N_PRIMARY_GUARDS_TO_USE;
}
if (configured >= 1) {
return configured;
}
return networkstatus_get_param(NULL,
param_name, param_default, 1, INT32_MAX);
}
/**
* If we haven't successfully built or used a circuit in this long, then
* consider that the internet is probably down.
*/
STATIC int
get_internet_likely_down_interval(void)
{
return networkstatus_get_param(NULL, "guard-internet-likely-down-interval",
DFLT_INTERNET_LIKELY_DOWN_INTERVAL,
1, INT32_MAX);
}
/**
* If we're trying to connect to a nonprimary guard for at least this
* many seconds, and we haven't gotten the connection to work, we will treat
* lower-priority guards as usable.
*/
STATIC int
get_nonprimary_guard_connect_timeout(void)
{
return networkstatus_get_param(NULL,
"guard-nonprimary-guard-connect-timeout",
DFLT_NONPRIMARY_GUARD_CONNECT_TIMEOUT,
1, INT32_MAX);
}
/**
* If a circuit has been sitting around in 'waiting for better guard' state
* for at least this long, we'll expire it.
*/
STATIC int
get_nonprimary_guard_idle_timeout(void)
{
return networkstatus_get_param(NULL,
"guard-nonprimary-guard-idle-timeout",
DFLT_NONPRIMARY_GUARD_IDLE_TIMEOUT,
1, INT32_MAX);
}
/**
* If our configuration retains fewer than this fraction of guards from the
* torrc, we are in a restricted setting.
*/
STATIC double
get_meaningful_restriction_threshold(void)
{
int32_t pct = networkstatus_get_param(NULL,
"guard-meaningful-restriction-percent",
DFLT_MEANINGFUL_RESTRICTION_PERCENT,
1, INT32_MAX);
return pct / 100.0;
}
/**
* If our configuration retains fewer than this fraction of guards from the
* torrc, we are in an extremely restricted setting, and should warn.
*/
STATIC double
get_extreme_restriction_threshold(void)
{
int32_t pct = networkstatus_get_param(NULL,
"guard-extreme-restriction-percent",
DFLT_EXTREME_RESTRICTION_PERCENT,
1, INT32_MAX);
return pct / 100.0;
}
/* Mark <b>guard</b> as maybe reachable again. */
static void
mark_guard_maybe_reachable(entry_guard_t *guard)
{
if (guard->is_reachable != GUARD_REACHABLE_NO) {
return;
}
/* Note that we do not clear failing_since: this guard is now only
* _maybe-reachable_. */
guard->is_reachable = GUARD_REACHABLE_MAYBE;
if (guard->is_filtered_guard)
guard->is_usable_filtered_guard = 1;
}
/**
* Called when the network comes up after having seemed to be down for
* a while: Mark the primary guards as maybe-reachable so that we'll
* try them again.
*/
STATIC void
mark_primary_guards_maybe_reachable(guard_selection_t *gs)
{
tor_assert(gs);
if (!gs->primary_guards_up_to_date)
entry_guards_update_primary(gs);
SMARTLIST_FOREACH_BEGIN(gs->primary_entry_guards, entry_guard_t *, guard) {
mark_guard_maybe_reachable(guard);
} SMARTLIST_FOREACH_END(guard);
}
/* Called when we exhaust all guards in our sampled set: Marks all guards as
maybe-reachable so that we 'll try them again. */
static void
mark_all_guards_maybe_reachable(guard_selection_t *gs)
{
tor_assert(gs);
SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
mark_guard_maybe_reachable(guard);
} SMARTLIST_FOREACH_END(guard);
}
/**@}*/
/**
* Given our options and our list of nodes, return the name of the
* guard selection that we should use. Return NULL for "use the
* same selection you were using before.
*/
STATIC const char *
choose_guard_selection(const or_options_t *options,
const networkstatus_t *live_ns,
const guard_selection_t *old_selection,
guard_selection_type_t *type_out)
{
tor_assert(options);
tor_assert(type_out);
if (options->UseBridges) {
*type_out = GS_TYPE_BRIDGE;
return "bridges";
}
if (! live_ns) {
/* without a networkstatus, we can't tell any more than that. */
*type_out = GS_TYPE_NORMAL;
return "default";
}
const smartlist_t *nodes = nodelist_get_list();
int n_guards = 0, n_passing_filter = 0;
SMARTLIST_FOREACH_BEGIN(nodes, const node_t *, node) {
if (node_is_possible_guard(node)) {
++n_guards;
if (node_passes_guard_filter(options, node)) {
++n_passing_filter;
}
}
} SMARTLIST_FOREACH_END(node);
/* We use separate 'high' and 'low' thresholds here to prevent flapping
* back and forth */
const int meaningful_threshold_high =
(int)(n_guards * get_meaningful_restriction_threshold() * 1.05);
const int meaningful_threshold_mid =
(int)(n_guards * get_meaningful_restriction_threshold());
const int meaningful_threshold_low =
(int)(n_guards * get_meaningful_restriction_threshold() * .95);
const int extreme_threshold =
(int)(n_guards * get_extreme_restriction_threshold());
/*
If we have no previous selection, then we're "restricted" iff we are
below the meaningful restriction threshold. That's easy enough.
But if we _do_ have a previous selection, we make it a little
"sticky": we only move from "restricted" to "default" when we find
that we're above the threshold plus 5%, and we only move from
"default" to "restricted" when we're below the threshold minus 5%.
That should prevent us from flapping back and forth if we happen to
be hovering very close to the default.
The extreme threshold is for warning only.
*/
static int have_warned_extreme_threshold = 0;
if (n_guards &&
n_passing_filter < extreme_threshold &&
! have_warned_extreme_threshold) {
have_warned_extreme_threshold = 1;
const double exclude_frac =
(n_guards - n_passing_filter) / (double)n_guards;
log_warn(LD_GUARD, "Your configuration excludes %d%% of all possible "
"guards. That's likely to make you stand out from the "
"rest of the world.", (int)(exclude_frac * 100));
}
/* Easy case: no previous selection. Just check if we are in restricted or
normal guard selection. */
if (old_selection == NULL) {
if (n_passing_filter >= meaningful_threshold_mid) {
*type_out = GS_TYPE_NORMAL;
return "default";
} else {
*type_out = GS_TYPE_RESTRICTED;
return "restricted";
}
}
/* Trickier case: we do have a previous guard selection context. */
tor_assert(old_selection);
/* Use high and low thresholds to decide guard selection, and if we fall in
the middle then keep the current guard selection context. */
if (n_passing_filter >= meaningful_threshold_high) {
*type_out = GS_TYPE_NORMAL;
return "default";
} else if (n_passing_filter < meaningful_threshold_low) {
*type_out = GS_TYPE_RESTRICTED;
return "restricted";
} else {
/* we are in the middle: maintain previous guard selection */
*type_out = old_selection->type;
return old_selection->name;
}
}
/**
* Check whether we should switch from our current guard selection to a
* different one. If so, switch and return 1. Return 0 otherwise.
*
* On a 1 return, the caller should mark all currently live circuits unusable
* for new streams, by calling circuit_mark_all_unused_circs() and
* circuit_mark_all_dirty_circs_as_unusable().
*/
int
update_guard_selection_choice(const or_options_t *options)
{
if (!curr_guard_context) {
create_initial_guard_context();
return 1;
}
guard_selection_type_t type = GS_TYPE_INFER;
const char *new_name = choose_guard_selection(
options,
networkstatus_get_live_consensus(approx_time()),
curr_guard_context,
&type);
tor_assert(new_name);
tor_assert(type != GS_TYPE_INFER);
const char *cur_name = curr_guard_context->name;
if (! strcmp(cur_name, new_name)) {
log_debug(LD_GUARD,
"Staying with guard context \"%s\" (no change)", new_name);
return 0; // No change
}
log_notice(LD_GUARD, "Switching to guard context \"%s\" (was using \"%s\")",
new_name, cur_name);
guard_selection_t *new_guard_context;
new_guard_context = get_guard_selection_by_name(new_name, type, 1);
tor_assert(new_guard_context);
tor_assert(new_guard_context != curr_guard_context);
curr_guard_context = new_guard_context;
return 1;
}
/**
* Return true iff <b>node</b> has all the flags needed for us to consider it
* a possible guard when sampling guards.
*/
static int
node_is_possible_guard(const node_t *node)
{
/* The "GUARDS" set is all nodes in the nodelist for which this predicate
* holds. */
tor_assert(node);
return (node->is_possible_guard &&
node->is_stable &&
node->is_fast &&
node->is_valid &&
node_is_dir(node) &&
!router_digest_is_me(node->identity));
}
/**
* Return the sampled guard with the RSA identity digest <b>rsa_id</b>, or
* NULL if we don't have one. */
STATIC entry_guard_t *
get_sampled_guard_with_id(guard_selection_t *gs,
const uint8_t *rsa_id)
{
tor_assert(gs);
tor_assert(rsa_id);
SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
if (tor_memeq(guard->identity, rsa_id, DIGEST_LEN))
return guard;
} SMARTLIST_FOREACH_END(guard);
return NULL;
}
/** If <b>gs</b> contains a sampled entry guard matching <b>bridge</b>,
* return that guard. Otherwise return NULL. */
static entry_guard_t *
get_sampled_guard_for_bridge(guard_selection_t *gs,
const bridge_info_t *bridge)
{
const uint8_t *id = bridge_get_rsa_id_digest(bridge);
const tor_addr_port_t *addrport = bridge_get_addr_port(bridge);
entry_guard_t *guard;
if (BUG(!addrport))
return NULL; // LCOV_EXCL_LINE
guard = get_sampled_guard_by_bridge_addr(gs, addrport);
if (! guard || (id && tor_memneq(id, guard->identity, DIGEST_LEN)))
return NULL;
else
return guard;
}
/** If we know a bridge_info_t matching <b>guard</b>, return that
* bridge. Otherwise return NULL. */
static bridge_info_t *
get_bridge_info_for_guard(const entry_guard_t *guard)
{
const uint8_t *identity = NULL;
if (! tor_digest_is_zero(guard->identity)) {
identity = (const uint8_t *)guard->identity;
}
if (BUG(guard->bridge_addr == NULL))
return NULL;
return get_configured_bridge_by_exact_addr_port_digest(
&guard->bridge_addr->addr,
guard->bridge_addr->port,
(const char*)identity);
}
/**
* Return true iff we have a sampled guard with the RSA identity digest
* <b>rsa_id</b>. */
static inline int
have_sampled_guard_with_id(guard_selection_t *gs, const uint8_t *rsa_id)
{
return get_sampled_guard_with_id(gs, rsa_id) != NULL;
}
/**
* Allocate a new entry_guard_t object for <b>node</b>, add it to the
* sampled entry guards in <b>gs</b>, and return it. <b>node</b> must
* not currently be a sampled guard in <b>gs</b>.
*/
STATIC entry_guard_t *
entry_guard_add_to_sample(guard_selection_t *gs,
const node_t *node)
{
log_info(LD_GUARD, "Adding %s to the entry guard sample set.",
node_describe(node));
/* make sure that the guard is not already sampled. */
if (BUG(have_sampled_guard_with_id(gs, (const uint8_t*)node->identity)))
return NULL; // LCOV_EXCL_LINE
return entry_guard_add_to_sample_impl(gs,
(const uint8_t*)node->identity,
node_get_nickname(node),
NULL);
}
/**
* Backend: adds a new sampled guard to <b>gs</b>, with given identity,
* nickname, and ORPort. rsa_id_digest and bridge_addrport are optional, but
* we need one of them. nickname is optional. The caller is responsible for
* maintaining the size limit of the SAMPLED_GUARDS set.
*/
static entry_guard_t *
entry_guard_add_to_sample_impl(guard_selection_t *gs,
const uint8_t *rsa_id_digest,
const char *nickname,
const tor_addr_port_t *bridge_addrport)
{
const int GUARD_LIFETIME = get_guard_lifetime();
tor_assert(gs);
// XXXX #20827 take ed25519 identity here too.
/* Make sure we can actually identify the guard. */
if (BUG(!rsa_id_digest && !bridge_addrport))
return NULL; // LCOV_EXCL_LINE
entry_guard_t *guard = tor_malloc_zero(sizeof(entry_guard_t));
/* persistent fields */
guard->is_persistent = (rsa_id_digest != NULL);
guard->selection_name = tor_strdup(gs->name);
if (rsa_id_digest)
memcpy(guard->identity, rsa_id_digest, DIGEST_LEN);
if (nickname)
strlcpy(guard->nickname, nickname, sizeof(guard->nickname));
guard->sampled_on_date = randomize_time(approx_time(), GUARD_LIFETIME/10);
tor_free(guard->sampled_by_version);
guard->sampled_by_version = tor_strdup(VERSION);
guard->currently_listed = 1;
guard->confirmed_idx = -1;
/* non-persistent fields */
guard->is_reachable = GUARD_REACHABLE_MAYBE;
if (bridge_addrport)
guard->bridge_addr = tor_memdup(bridge_addrport, sizeof(*bridge_addrport));
smartlist_add(gs->sampled_entry_guards, guard);
guard->in_selection = gs;
entry_guard_set_filtered_flags(get_options(), gs, guard);
entry_guards_changed_for_guard_selection(gs);
return guard;
}
/**
* Add an entry guard to the "bridges" guard selection sample, with
* information taken from <b>bridge</b>. Return that entry guard.
*/
static entry_guard_t *
entry_guard_add_bridge_to_sample(guard_selection_t *gs,
const bridge_info_t *bridge)
{
const uint8_t *id_digest = bridge_get_rsa_id_digest(bridge);
const tor_addr_port_t *addrport = bridge_get_addr_port(bridge);
tor_assert(addrport);
/* make sure that the guard is not already sampled. */
if (BUG(get_sampled_guard_for_bridge(gs, bridge)))
return NULL; // LCOV_EXCL_LINE
return entry_guard_add_to_sample_impl(gs, id_digest, NULL, addrport);
}
/**
* Return the entry_guard_t in <b>gs</b> whose address is <b>addrport</b>,
* or NULL if none exists.
*/
static entry_guard_t *
get_sampled_guard_by_bridge_addr(guard_selection_t *gs,
const tor_addr_port_t *addrport)
{
if (! gs)
return NULL;
if (BUG(!addrport))
return NULL;
SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, g) {
if (g->bridge_addr && tor_addr_port_eq(addrport, g->bridge_addr))
return g;
} SMARTLIST_FOREACH_END(g);
return NULL;
}
/** Update the guard subsystem's knowledge of the identity of the bridge
* at <b>addrport</b>. Idempotent.
*/
void
entry_guard_learned_bridge_identity(const tor_addr_port_t *addrport,
const uint8_t *rsa_id_digest)
{
guard_selection_t *gs = get_guard_selection_by_name("bridges",
GS_TYPE_BRIDGE,
0);
if (!gs)
return;
entry_guard_t *g = get_sampled_guard_by_bridge_addr(gs, addrport);
if (!g)
return;
int make_persistent = 0;
if (tor_digest_is_zero(g->identity)) {
memcpy(g->identity, rsa_id_digest, DIGEST_LEN);
make_persistent = 1;
} else if (tor_memeq(g->identity, rsa_id_digest, DIGEST_LEN)) {
/* Nothing to see here; we learned something we already knew. */
if (BUG(! g->is_persistent))
make_persistent = 1;
} else {
char old_id[HEX_DIGEST_LEN+1];
base16_encode(old_id, sizeof(old_id), g->identity, sizeof(g->identity));
log_warn(LD_BUG, "We 'learned' an identity %s for a bridge at %s:%d, but "
"we already knew a different one (%s). Ignoring the new info as "
"possibly bogus.",
hex_str((const char *)rsa_id_digest, DIGEST_LEN),
fmt_and_decorate_addr(&addrport->addr), addrport->port,
old_id);
return; // redundant, but let's be clear: we're not making this persistent.
}
if (make_persistent) {
g->is_persistent = 1;
entry_guards_changed_for_guard_selection(gs);
}
}
/**
* Return the number of sampled guards in <b>gs</b> that are "filtered"
* (that is, we're willing to connect to them) and that are "usable"
* (that is, either "reachable" or "maybe reachable").
*
* If a restriction is provided in <b>rst</b>, do not count any guards that
* violate it.
*/
STATIC int
num_reachable_filtered_guards(const guard_selection_t *gs,
const entry_guard_restriction_t *rst)
{
int n_reachable_filtered_guards = 0;
SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
entry_guard_consider_retry(guard);
if (! entry_guard_obeys_restriction(guard, rst))
continue;
if (guard->is_usable_filtered_guard)
++n_reachable_filtered_guards;
} SMARTLIST_FOREACH_END(guard);
return n_reachable_filtered_guards;
}
/** Return the actual maximum size for the sample in <b>gs</b>,
* given that we know about <b>n_guards</b> total. */
static int
get_max_sample_size(guard_selection_t *gs,
int n_guards)
{
const int using_bridges = (gs->type == GS_TYPE_BRIDGE);
const int min_sample = get_min_filtered_sample_size();
/* If we are in bridge mode, expand our sample set as needed without worrying
* about max size. We should respect the user's wishes to use many bridges if
* that's what they have specified in their configuration file. */
if (using_bridges)
return INT_MAX;
const int max_sample_by_pct = (int)(n_guards * get_max_sample_threshold());
const int max_sample_absolute = get_max_sample_size_absolute();
const int max_sample = MIN(max_sample_by_pct, max_sample_absolute);
if (max_sample < min_sample)
return min_sample;
else
return max_sample;
}
/**
* Return a smartlist of the all the guards that are not currently
* members of the sample (GUARDS - SAMPLED_GUARDS). The elements of
* this list are node_t pointers in the non-bridge case, and
* bridge_info_t pointers in the bridge case. Set *<b>n_guards_out/b>
* to the number of guards that we found in GUARDS, including those
* that were already sampled.
*/
static smartlist_t *
get_eligible_guards(const or_options_t *options,
guard_selection_t *gs,
int *n_guards_out)
{
/* Construct eligible_guards as GUARDS - SAMPLED_GUARDS */
smartlist_t *eligible_guards = smartlist_new();
int n_guards = 0; // total size of "GUARDS"
if (gs->type == GS_TYPE_BRIDGE) {
const smartlist_t *bridges = bridge_list_get();
SMARTLIST_FOREACH_BEGIN(bridges, bridge_info_t *, bridge) {
++n_guards;
if (NULL != get_sampled_guard_for_bridge(gs, bridge)) {
continue;
}
smartlist_add(eligible_guards, bridge);
} SMARTLIST_FOREACH_END(bridge);
} else {
const smartlist_t *nodes = nodelist_get_list();
const int n_sampled = smartlist_len(gs->sampled_entry_guards);
/* Build a bloom filter of our current guards: let's keep this O(N). */
digestset_t *sampled_guard_ids = digestset_new(n_sampled);
SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, const entry_guard_t *,
guard) {
digestset_add(sampled_guard_ids, guard->identity);
} SMARTLIST_FOREACH_END(guard);
SMARTLIST_FOREACH_BEGIN(nodes, const node_t *, node) {
if (! node_is_possible_guard(node))
continue;
if (gs->type == GS_TYPE_RESTRICTED) {
/* In restricted mode, we apply the filter BEFORE sampling, so
* that we are sampling from the nodes that we might actually
* select. If we sampled first, we might wind up with a sample
* that didn't include any EntryNodes at all. */
if (! node_passes_guard_filter(options, node))
continue;
}
++n_guards;
if (digestset_contains(sampled_guard_ids, node->identity))
continue;
smartlist_add(eligible_guards, (node_t*)node);
} SMARTLIST_FOREACH_END(node);
/* Now we can free that bloom filter. */
digestset_free(sampled_guard_ids);
}
*n_guards_out = n_guards;
return eligible_guards;
}
/** Helper: given a smartlist of either bridge_info_t (if gs->type is
* GS_TYPE_BRIDGE) or node_t (otherwise), pick one that can be a guard,
* add it as a guard, remove it from the list, and return a new
* entry_guard_t. Return NULL on failure. */
static entry_guard_t *
select_and_add_guard_item_for_sample(guard_selection_t *gs,
smartlist_t *eligible_guards)
{
entry_guard_t *added_guard;
if (gs->type == GS_TYPE_BRIDGE) {
const bridge_info_t *bridge = smartlist_choose(eligible_guards);
if (BUG(!bridge))
return NULL; // LCOV_EXCL_LINE
smartlist_remove(eligible_guards, bridge);
added_guard = entry_guard_add_bridge_to_sample(gs, bridge);
} else {
const node_t *node =
node_sl_choose_by_bandwidth(eligible_guards, WEIGHT_FOR_GUARD);
if (BUG(!node))
return NULL; // LCOV_EXCL_LINE
smartlist_remove(eligible_guards, node);
added_guard = entry_guard_add_to_sample(gs, node);
}
return added_guard;
}
/**
* Return true iff we need a consensus to update our guards, but we don't
* have one. (We can return 0 here either if the consensus is _not_ missing,
* or if we don't need a consensus because we're using bridges.)
*/
static int
live_consensus_is_missing(const guard_selection_t *gs)
{
tor_assert(gs);
if (gs->type == GS_TYPE_BRIDGE) {
/* We don't update bridges from the consensus; they aren't there. */
return 0;
}
return networkstatus_get_live_consensus(approx_time()) == NULL;
}
/**
* Add new guards to the sampled guards in <b>gs</b> until there are
* enough usable filtered guards, but never grow the sample beyond its
* maximum size. Return the last guard added, or NULL if none were
* added.
*/
STATIC entry_guard_t *
entry_guards_expand_sample(guard_selection_t *gs)
{
tor_assert(gs);
const or_options_t *options = get_options();
if (live_consensus_is_missing(gs)) {
log_info(LD_GUARD, "Not expanding the sample guard set; we have "
"no live consensus.");
return NULL;
}
int n_sampled = smartlist_len(gs->sampled_entry_guards);
entry_guard_t *added_guard = NULL;
int n_usable_filtered_guards = num_reachable_filtered_guards(gs, NULL);
int n_guards = 0;
smartlist_t *eligible_guards = get_eligible_guards(options, gs, &n_guards);
const int max_sample = get_max_sample_size(gs, n_guards);
const int min_filtered_sample = get_min_filtered_sample_size();
log_info(LD_GUARD, "Expanding the sample guard set. We have %d guards "
"in the sample, and %d eligible guards to extend it with.",
n_sampled, smartlist_len(eligible_guards));
while (n_usable_filtered_guards < min_filtered_sample) {
/* Has our sample grown too large to expand? */
if (n_sampled >= max_sample) {
log_info(LD_GUARD, "Not expanding the guard sample any further; "
"just hit the maximum sample threshold of %d",
max_sample);
goto done;
}
/* Did we run out of guards? */
if (smartlist_len(eligible_guards) == 0) {
/* LCOV_EXCL_START
As long as MAX_SAMPLE_THRESHOLD makes can't be adjusted to
allow all guards to be sampled, this can't be reached.
*/
log_info(LD_GUARD, "Not expanding the guard sample any further; "
"just ran out of eligible guards");
goto done;
/* LCOV_EXCL_STOP */
}
/* Otherwise we can add at least one new guard. */
added_guard = select_and_add_guard_item_for_sample(gs, eligible_guards);
if (!added_guard)
goto done; // LCOV_EXCL_LINE -- only fails on BUG.
++n_sampled;
if (added_guard->is_usable_filtered_guard)
++n_usable_filtered_guards;
}
done:
smartlist_free(eligible_guards);
return added_guard;
}
/**
* Helper: <b>guard</b> has just been removed from the sampled guards:
* also remove it from primary and confirmed. */
static void
remove_guard_from_confirmed_and_primary_lists(guard_selection_t *gs,
entry_guard_t *guard)
{
if (guard->is_primary) {
guard->is_primary = 0;
smartlist_remove_keeporder(gs->primary_entry_guards, guard);
} else {
if (BUG(smartlist_contains(gs->primary_entry_guards, guard))) {
smartlist_remove_keeporder(gs->primary_entry_guards, guard);
}
}
if (guard->confirmed_idx >= 0) {
smartlist_remove_keeporder(gs->confirmed_entry_guards, guard);
guard->confirmed_idx = -1;
guard->confirmed_on_date = 0;
} else {
if (BUG(smartlist_contains(gs->confirmed_entry_guards, guard))) {
// LCOV_EXCL_START
smartlist_remove_keeporder(gs->confirmed_entry_guards, guard);
// LCOV_EXCL_STOP
}
}
}
/** Return true iff <b>guard</b> is currently "listed" -- that is, it
* appears in the consensus, or as a configured bridge (as
* appropriate) */
MOCK_IMPL(STATIC int,
entry_guard_is_listed,(guard_selection_t *gs, const entry_guard_t *guard))
{
if (gs->type == GS_TYPE_BRIDGE) {
return NULL != get_bridge_info_for_guard(guard);
} else {
const node_t *node = node_get_by_id(guard->identity);
return node && node_is_possible_guard(node);
}
}
/**
* Update the status of all sampled guards based on the arrival of a
* new consensus networkstatus document. This will include marking
* some guards as listed or unlisted, and removing expired guards. */
STATIC void
sampled_guards_update_from_consensus(guard_selection_t *gs)
{
tor_assert(gs);
const int REMOVE_UNLISTED_GUARDS_AFTER =
(get_remove_unlisted_guards_after_days() * 86400);
const int unlisted_since_slop = REMOVE_UNLISTED_GUARDS_AFTER / 5;
// It's important to use only a live consensus here; we don't want to
// make changes based on anything expired or old.
if (live_consensus_is_missing(gs)) {
log_info(LD_GUARD, "Not updating the sample guard set; we have "
"no live consensus.");
return;
}
log_info(LD_GUARD, "Updating sampled guard status based on received "
"consensus.");
int n_changes = 0;
/* First: Update listed/unlisted. */
SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
/* XXXX #20827 check ed ID too */
const int is_listed = entry_guard_is_listed(gs, guard);
if (is_listed && ! guard->currently_listed) {
++n_changes;
guard->currently_listed = 1;
guard->unlisted_since_date = 0;
log_info(LD_GUARD, "Sampled guard %s is now listed again.",
entry_guard_describe(guard));
} else if (!is_listed && guard->currently_listed) {
++n_changes;
guard->currently_listed = 0;
guard->unlisted_since_date = randomize_time(approx_time(),
unlisted_since_slop);
log_info(LD_GUARD, "Sampled guard %s is now unlisted.",
entry_guard_describe(guard));
} else if (is_listed && guard->currently_listed) {
log_debug(LD_GUARD, "Sampled guard %s is still listed.",
entry_guard_describe(guard));
} else {
tor_assert(! is_listed && ! guard->currently_listed);
log_debug(LD_GUARD, "Sampled guard %s is still unlisted.",
entry_guard_describe(guard));
}
/* Clean up unlisted_since_date, just in case. */
if (guard->currently_listed && guard->unlisted_since_date) {
++n_changes;
guard->unlisted_since_date = 0;
log_warn(LD_BUG, "Sampled guard %s was listed, but with "
"unlisted_since_date set. Fixing.",
entry_guard_describe(guard));
} else if (!guard->currently_listed && ! guard->unlisted_since_date) {
++n_changes;
guard->unlisted_since_date = randomize_time(approx_time(),
unlisted_since_slop);
log_warn(LD_BUG, "Sampled guard %s was unlisted, but with "
"unlisted_since_date unset. Fixing.",
entry_guard_describe(guard));
}
} SMARTLIST_FOREACH_END(guard);
const time_t remove_if_unlisted_since =
approx_time() - REMOVE_UNLISTED_GUARDS_AFTER;
const time_t maybe_remove_if_sampled_before =
approx_time() - get_guard_lifetime();
const time_t remove_if_confirmed_before =
approx_time() - get_guard_confirmed_min_lifetime();
/* Then: remove the ones that have been junk for too long */
SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
int rmv = 0;
if (guard->currently_listed == 0 &&
guard->unlisted_since_date < remove_if_unlisted_since) {
/*
"We have a live consensus, and {IS_LISTED} is false, and
{FIRST_UNLISTED_AT} is over {REMOVE_UNLISTED_GUARDS_AFTER}
days in the past."
*/
log_info(LD_GUARD, "Removing sampled guard %s: it has been unlisted "
"for over %d days", entry_guard_describe(guard),
get_remove_unlisted_guards_after_days());
rmv = 1;
} else if (guard->sampled_on_date < maybe_remove_if_sampled_before) {
/* We have a live consensus, and {ADDED_ON_DATE} is over
{GUARD_LIFETIME} ago, *and* {CONFIRMED_ON_DATE} is either
"never", or over {GUARD_CONFIRMED_MIN_LIFETIME} ago.
*/
if (guard->confirmed_on_date == 0) {
rmv = 1;
log_info(LD_GUARD, "Removing sampled guard %s: it was sampled "
"over %d days ago, but never confirmed.",
entry_guard_describe(guard),
get_guard_lifetime() / 86400);
} else if (guard->confirmed_on_date < remove_if_confirmed_before) {
rmv = 1;
log_info(LD_GUARD, "Removing sampled guard %s: it was sampled "
"over %d days ago, and confirmed over %d days ago.",
entry_guard_describe(guard),
get_guard_lifetime() / 86400,
get_guard_confirmed_min_lifetime() / 86400);
}
}
if (rmv) {
++n_changes;
SMARTLIST_DEL_CURRENT(gs->sampled_entry_guards, guard);
remove_guard_from_confirmed_and_primary_lists(gs, guard);
entry_guard_free(guard);
}
} SMARTLIST_FOREACH_END(guard);
if (n_changes) {
gs->primary_guards_up_to_date = 0;
entry_guards_update_filtered_sets(gs);
/* We don't need to rebuild the confirmed list right here -- we may have
* removed confirmed guards above, but we can't have added any new
* confirmed guards.
*/
entry_guards_changed_for_guard_selection(gs);
}
}
/**
* Return true iff <b>node</b> is a Tor relay that we are configured to
* be able to connect to. */
static int
node_passes_guard_filter(const or_options_t *options,
const node_t *node)
{
/* NOTE: Make sure that this function stays in sync with
* options_transition_affects_entry_guards */
if (routerset_contains_node(options->ExcludeNodes, node))
return 0;
if (options->EntryNodes &&
!routerset_contains_node(options->EntryNodes, node))
return 0;
if (!fascist_firewall_allows_node(node, FIREWALL_OR_CONNECTION, 0))
return 0;
if (node_is_a_configured_bridge(node))
return 0;
return 1;
}
/** Helper: Return true iff <b>bridge</b> passes our configuration
* filter-- if it is a relay that we are configured to be able to
* connect to. */
static int
bridge_passes_guard_filter(const or_options_t *options,
const bridge_info_t *bridge)
{
tor_assert(bridge);
if (!bridge)
return 0;
if (routerset_contains_bridge(options->ExcludeNodes, bridge))
return 0;
/* Ignore entrynodes */
const tor_addr_port_t *addrport = bridge_get_addr_port(bridge);
if (!fascist_firewall_allows_address_addr(&addrport->addr,
addrport->port,
FIREWALL_OR_CONNECTION,
0, 0))
return 0;
return 1;
}
/**
* Return true iff <b>guard</b> is a Tor relay that we are configured to
* be able to connect to, and we haven't disabled it for omission from
* the consensus or path bias issues. */
static int
entry_guard_passes_filter(const or_options_t *options, guard_selection_t *gs,
entry_guard_t *guard)
{
if (guard->currently_listed == 0)
return 0;
if (guard->pb.path_bias_disabled)
return 0;
if (gs->type == GS_TYPE_BRIDGE) {
const bridge_info_t *bridge = get_bridge_info_for_guard(guard);
if (bridge == NULL)
return 0;
return bridge_passes_guard_filter(options, bridge);
} else {
const node_t *node = node_get_by_id(guard->identity);
if (node == NULL) {
// This can happen when currently_listed is true, and we're not updating
// it because we don't have a live consensus.
return 0;
}
return node_passes_guard_filter(options, node);
}
}
/** Return true iff <b>guard</b> is in the same family as <b>node</b>.
*/
static int
guard_in_node_family(const entry_guard_t *guard, const node_t *node)
{
const node_t *guard_node = node_get_by_id(guard->identity);
if (guard_node) {
return nodes_in_same_family(guard_node, node);
} else {
/* If we don't have a node_t for the guard node, we might have
* a bridge_info_t for it. So let's check to see whether the bridge
* address matches has any family issues.
*
* (Strictly speaking, I believe this check is unnecessary, since we only
* use it to avoid the exit's family when building circuits, and we don't
* build multihop circuits until we have a routerinfo_t for the
* bridge... at which point, we'll also have a node_t for the
* bridge. Nonetheless, it seems wise to include it, in case our
* assumptions change down the road. -nickm.)
*/
if (get_options()->EnforceDistinctSubnets && guard->bridge_addr) {
tor_addr_t node_addr;
node_get_addr(node, &node_addr);
if (addrs_in_same_network_family(&node_addr,
&guard->bridge_addr->addr)) {
return 1;
}
}
return 0;
}
}
/* Allocate and return a new exit guard restriction (where <b>exit_id</b> is of
* size DIGEST_LEN) */
STATIC entry_guard_restriction_t *
guard_create_exit_restriction(const uint8_t *exit_id)
{
entry_guard_restriction_t *rst = NULL;
rst = tor_malloc_zero(sizeof(entry_guard_restriction_t));
rst->type = RST_EXIT_NODE;
memcpy(rst->exclude_id, exit_id, DIGEST_LEN);
return rst;
}
/** If we have fewer than this many possible usable guards, don't set
* MD-availability-based restrictions: we might blacklist all of them. */
#define MIN_GUARDS_FOR_MD_RESTRICTION 10
/** Return true if we should set md dirserver restrictions. We might not want
* to set those if our guard options are too restricted, since we don't want
* to blacklist all of them. */
static int
should_set_md_dirserver_restriction(void)
{
const guard_selection_t *gs = get_guard_selection_info();
int num_usable_guards = num_reachable_filtered_guards(gs, NULL);
/* Don't set restriction if too few reachable filtered guards. */
if (num_usable_guards < MIN_GUARDS_FOR_MD_RESTRICTION) {
log_info(LD_GUARD, "Not setting md restriction: only %d"
" usable guards.", num_usable_guards);
return 0;
}
/* We have enough usable guards: set MD restriction */
return 1;
}
/** Allocate and return an outdated md guard restriction. Return NULL if no
* such restriction is needed. */
STATIC entry_guard_restriction_t *
guard_create_dirserver_md_restriction(void)
{
entry_guard_restriction_t *rst = NULL;
if (!should_set_md_dirserver_restriction()) {
log_debug(LD_GUARD, "Not setting md restriction: too few "
"filtered guards.");
return NULL;
}
rst = tor_malloc_zero(sizeof(entry_guard_restriction_t));
rst->type = RST_OUTDATED_MD_DIRSERVER;
return rst;
}
/* Return True if <b>guard</b> obeys the exit restriction <b>rst</b>. */
static int
guard_obeys_exit_restriction(const entry_guard_t *guard,
const entry_guard_restriction_t *rst)
{
tor_assert(rst->type == RST_EXIT_NODE);
// Exclude the exit ID and all of its family.
const node_t *node = node_get_by_id((const char*)rst->exclude_id);
if (node && guard_in_node_family(guard, node))
return 0;
return tor_memneq(guard->identity, rst->exclude_id, DIGEST_LEN);
}
/** Return True if <b>guard</b> should be used as a dirserver for fetching
* microdescriptors. */
static int
guard_obeys_md_dirserver_restriction(const entry_guard_t *guard)
{
/* If this guard is an outdated dirserver, don't use it. */
if (microdesc_relay_is_outdated_dirserver(guard->identity)) {
log_info(LD_GENERAL, "Skipping %s dirserver: outdated",
hex_str(guard->identity, DIGEST_LEN));
return 0;
}
log_debug(LD_GENERAL, "%s dirserver obeys md restrictions",
hex_str(guard->identity, DIGEST_LEN));
return 1;
}
/**
* Return true iff <b>guard</b> obeys the restrictions defined in <b>rst</b>.
* (If <b>rst</b> is NULL, there are no restrictions.)
*/
static int
entry_guard_obeys_restriction(const entry_guard_t *guard,
const entry_guard_restriction_t *rst)
{
tor_assert(guard);
if (! rst)
return 1; // No restriction? No problem.
if (rst->type == RST_EXIT_NODE) {
return guard_obeys_exit_restriction(guard, rst);
} else if (rst->type == RST_OUTDATED_MD_DIRSERVER) {
return guard_obeys_md_dirserver_restriction(guard);
}
tor_assert_nonfatal_unreached();
return 0;
}
/**
* Update the <b>is_filtered_guard</b> and <b>is_usable_filtered_guard</b>
* flags on <b>guard</b>. */
void
entry_guard_set_filtered_flags(const or_options_t *options,
guard_selection_t *gs,
entry_guard_t *guard)
{
unsigned was_filtered = guard->is_filtered_guard;
guard->is_filtered_guard = 0;
guard->is_usable_filtered_guard = 0;
if (entry_guard_passes_filter(options, gs, guard)) {
guard->is_filtered_guard = 1;
if (guard->is_reachable != GUARD_REACHABLE_NO)
guard->is_usable_filtered_guard = 1;
entry_guard_consider_retry(guard);
}
log_debug(LD_GUARD, "Updated sampled guard %s: filtered=%d; "
"reachable_filtered=%d.", entry_guard_describe(guard),
guard->is_filtered_guard, guard->is_usable_filtered_guard);
if (!bool_eq(was_filtered, guard->is_filtered_guard)) {
/* This guard might now be primary or nonprimary. */
gs->primary_guards_up_to_date = 0;
}
}
/**
* Update the <b>is_filtered_guard</b> and <b>is_usable_filtered_guard</b>
* flag on every guard in <b>gs</b>. */
STATIC void
entry_guards_update_filtered_sets(guard_selection_t *gs)
{
const or_options_t *options = get_options();
SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
entry_guard_set_filtered_flags(options, gs, guard);
} SMARTLIST_FOREACH_END(guard);
}
/**
* Return a random guard from the reachable filtered sample guards
* in <b>gs</b>, subject to the exclusion rules listed in <b>flags</b>.
* Return NULL if no such guard can be found.
*
* Make sure that the sample is big enough, and that all the filter flags
* are set correctly, before calling this function.
*
* If a restriction is provided in <b>rst</b>, do not return any guards that
* violate it.
**/
STATIC entry_guard_t *
sample_reachable_filtered_entry_guards(guard_selection_t *gs,
const entry_guard_restriction_t *rst,
unsigned flags)
{
tor_assert(gs);
entry_guard_t *result = NULL;
const unsigned exclude_confirmed = flags & SAMPLE_EXCLUDE_CONFIRMED;
const unsigned exclude_primary = flags & SAMPLE_EXCLUDE_PRIMARY;
const unsigned exclude_pending = flags & SAMPLE_EXCLUDE_PENDING;
const unsigned no_update_primary = flags & SAMPLE_NO_UPDATE_PRIMARY;
const unsigned need_descriptor = flags & SAMPLE_EXCLUDE_NO_DESCRIPTOR;
SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
entry_guard_consider_retry(guard);
} SMARTLIST_FOREACH_END(guard);
const int n_reachable_filtered = num_reachable_filtered_guards(gs, rst);
log_info(LD_GUARD, "Trying to sample a reachable guard: We know of %d "
"in the USABLE_FILTERED set.", n_reachable_filtered);
const int min_filtered_sample = get_min_filtered_sample_size();
if (n_reachable_filtered < min_filtered_sample) {
log_info(LD_GUARD, " (That isn't enough. Trying to expand the sample.)");
entry_guards_expand_sample(gs);
}
if (exclude_primary && !gs->primary_guards_up_to_date && !no_update_primary)
entry_guards_update_primary(gs);
/* Build the set of reachable filtered guards. */
smartlist_t *reachable_filtered_sample = smartlist_new();
SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
entry_guard_consider_retry(guard);// redundant, but cheap.
if (! entry_guard_obeys_restriction(guard, rst))
continue;
if (! guard->is_usable_filtered_guard)
continue;
if (exclude_confirmed && guard->confirmed_idx >= 0)
continue;
if (exclude_primary && guard->is_primary)
continue;
if (exclude_pending && guard->is_pending)
continue;
if (need_descriptor && !guard_has_descriptor(guard))
continue;
smartlist_add(reachable_filtered_sample, guard);
} SMARTLIST_FOREACH_END(guard);
log_info(LD_GUARD, " (After filters [%x], we have %d guards to consider.)",
flags, smartlist_len(reachable_filtered_sample));
if (smartlist_len(reachable_filtered_sample)) {
result = smartlist_choose(reachable_filtered_sample);
log_info(LD_GUARD, " (Selected %s.)",
result ? entry_guard_describe(result) : "<null>");
}
smartlist_free(reachable_filtered_sample);
return result;
}
/**
* Helper: compare two entry_guard_t by their confirmed_idx values.
* Used to sort the confirmed list.
*/
static int
compare_guards_by_confirmed_idx(const void **a_, const void **b_)
{
const entry_guard_t *a = *a_, *b = *b_;
if (a->confirmed_idx < b->confirmed_idx)
return -1;
else if (a->confirmed_idx > b->confirmed_idx)
return 1;
else
return 0;
}
/**
* Find the confirmed guards from among the sampled guards in <b>gs</b>,
* and put them in confirmed_entry_guards in the correct
* order. Recalculate their indices.
*/
STATIC void
entry_guards_update_confirmed(guard_selection_t *gs)
{
smartlist_clear(gs->confirmed_entry_guards);
SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
if (guard->confirmed_idx >= 0)
smartlist_add(gs->confirmed_entry_guards, guard);
} SMARTLIST_FOREACH_END(guard);
smartlist_sort(gs->confirmed_entry_guards, compare_guards_by_confirmed_idx);
int any_changed = 0;
SMARTLIST_FOREACH_BEGIN(gs->confirmed_entry_guards, entry_guard_t *, guard) {
if (guard->confirmed_idx != guard_sl_idx) {
any_changed = 1;
guard->confirmed_idx = guard_sl_idx;
}
} SMARTLIST_FOREACH_END(guard);
gs->next_confirmed_idx = smartlist_len(gs->confirmed_entry_guards);
if (any_changed) {
entry_guards_changed_for_guard_selection(gs);
}
}
/**
* Mark <b>guard</b> as a confirmed guard -- that is, one that we have
* connected to, and intend to use again.
*/
STATIC void
make_guard_confirmed(guard_selection_t *gs, entry_guard_t *guard)
{
if (BUG(guard->confirmed_on_date && guard->confirmed_idx >= 0))
return; // LCOV_EXCL_LINE
if (BUG(smartlist_contains(gs->confirmed_entry_guards, guard)))
return; // LCOV_EXCL_LINE
const int GUARD_LIFETIME = get_guard_lifetime();
guard->confirmed_on_date = randomize_time(approx_time(), GUARD_LIFETIME/10);
log_info(LD_GUARD, "Marking %s as a confirmed guard (index %d)",
entry_guard_describe(guard),
gs->next_confirmed_idx);
guard->confirmed_idx = gs->next_confirmed_idx++;
smartlist_add(gs->confirmed_entry_guards, guard);
// This confirmed guard might kick something else out of the primary
// guards.
gs->primary_guards_up_to_date = 0;
entry_guards_changed_for_guard_selection(gs);
}
/**
* Recalculate the list of primary guards (the ones we'd prefer to use) from
* the filtered sample and the confirmed list.
*/
STATIC void
entry_guards_update_primary(guard_selection_t *gs)
{
tor_assert(gs);
// prevent recursion. Recursion is potentially very bad here.
static int running = 0;
tor_assert(!running);
running = 1;
const int N_PRIMARY_GUARDS = get_n_primary_guards();
smartlist_t *new_primary_guards = smartlist_new();
smartlist_t *old_primary_guards = smartlist_new();
smartlist_add_all(old_primary_guards, gs->primary_entry_guards);
/* Set this flag now, to prevent the calls below from recursing. */
gs->primary_guards_up_to_date = 1;
/* First, can we fill it up with confirmed guards? */
SMARTLIST_FOREACH_BEGIN(gs->confirmed_entry_guards, entry_guard_t *, guard) {
if (smartlist_len(new_primary_guards) >= N_PRIMARY_GUARDS)
break;
if (! guard->is_filtered_guard)
continue;
guard->is_primary = 1;
smartlist_add(new_primary_guards, guard);
} SMARTLIST_FOREACH_END(guard);
/* Can we keep any older primary guards? First remove all the ones
* that we already kept. */
SMARTLIST_FOREACH_BEGIN(old_primary_guards, entry_guard_t *, guard) {
if (smartlist_contains(new_primary_guards, guard)) {
SMARTLIST_DEL_CURRENT_KEEPORDER(old_primary_guards, guard);
}
} SMARTLIST_FOREACH_END(guard);
/* Now add any that are still good. */
SMARTLIST_FOREACH_BEGIN(old_primary_guards, entry_guard_t *, guard) {
if (smartlist_len(new_primary_guards) >= N_PRIMARY_GUARDS)
break;
if (! guard->is_filtered_guard)
continue;
guard->is_primary = 1;
smartlist_add(new_primary_guards, guard);
SMARTLIST_DEL_CURRENT_KEEPORDER(old_primary_guards, guard);
} SMARTLIST_FOREACH_END(guard);
/* Mark the remaining previous primary guards as non-primary */
SMARTLIST_FOREACH_BEGIN(old_primary_guards, entry_guard_t *, guard) {
guard->is_primary = 0;
} SMARTLIST_FOREACH_END(guard);
/* Finally, fill out the list with sampled guards. */
while (smartlist_len(new_primary_guards) < N_PRIMARY_GUARDS) {
entry_guard_t *guard = sample_reachable_filtered_entry_guards(gs, NULL,
SAMPLE_EXCLUDE_CONFIRMED|
SAMPLE_EXCLUDE_PRIMARY|
SAMPLE_NO_UPDATE_PRIMARY);
if (!guard)
break;
guard->is_primary = 1;
smartlist_add(new_primary_guards, guard);
}
#if 1
/* Debugging. */
SMARTLIST_FOREACH(gs->sampled_entry_guards, entry_guard_t *, guard, {
tor_assert_nonfatal(
bool_eq(guard->is_primary,
smartlist_contains(new_primary_guards, guard)));
});
#endif /* 1 */
int any_change = 0;
if (smartlist_len(gs->primary_entry_guards) !=
smartlist_len(new_primary_guards)) {
any_change = 1;
} else {
SMARTLIST_FOREACH_BEGIN(gs->primary_entry_guards, entry_guard_t *, g) {
if (g != smartlist_get(new_primary_guards, g_sl_idx)) {
any_change = 1;
}
} SMARTLIST_FOREACH_END(g);
}
if (any_change) {
log_info(LD_GUARD, "Primary entry guards have changed. "
"New primary guard list is: ");
int n = smartlist_len(new_primary_guards);
SMARTLIST_FOREACH_BEGIN(new_primary_guards, entry_guard_t *, g) {
log_info(LD_GUARD, " %d/%d: %s%s%s",
g_sl_idx+1, n, entry_guard_describe(g),
g->confirmed_idx >= 0 ? " (confirmed)" : "",
g->is_filtered_guard ? "" : " (excluded by filter)");
} SMARTLIST_FOREACH_END(g);
}
smartlist_free(old_primary_guards);
smartlist_free(gs->primary_entry_guards);
gs->primary_entry_guards = new_primary_guards;
gs->primary_guards_up_to_date = 1;
running = 0;
}
/**
* Return the number of seconds after the last attempt at which we should
* retry a guard that has been failing since <b>failing_since</b>.
*/
static int
get_retry_schedule(time_t failing_since, time_t now,
int is_primary)
{
const unsigned SIX_HOURS = 6 * 3600;
const unsigned FOUR_DAYS = 4 * 86400;
const unsigned SEVEN_DAYS = 7 * 86400;
time_t tdiff;
if (now > failing_since) {
tdiff = now - failing_since;
} else {
tdiff = 0;
}
const struct {
time_t maximum; int primary_delay; int nonprimary_delay;
} delays[] = {
{ SIX_HOURS, 10*60, 1*60*60 },
{ FOUR_DAYS, 90*60, 4*60*60 },
{ SEVEN_DAYS, 4*60*60, 18*60*60 },
{ TIME_MAX, 9*60*60, 36*60*60 }
};
unsigned i;
for (i = 0; i < ARRAY_LENGTH(delays); ++i) {
if (tdiff <= delays[i].maximum) {
return is_primary ? delays[i].primary_delay : delays[i].nonprimary_delay;
}
}
/* LCOV_EXCL_START -- can't reach, since delays ends with TIME_MAX. */
tor_assert_nonfatal_unreached();
return 36*60*60;
/* LCOV_EXCL_STOP */
}
/**
* If <b>guard</b> is unreachable, consider whether enough time has passed
* to consider it maybe-reachable again.
*/
STATIC void
entry_guard_consider_retry(entry_guard_t *guard)
{
if (guard->is_reachable != GUARD_REACHABLE_NO)
return; /* No retry needed. */
const time_t now = approx_time();
const int delay =
get_retry_schedule(guard->failing_since, now, guard->is_primary);
const time_t last_attempt = guard->last_tried_to_connect;
if (BUG(last_attempt == 0) ||
now >= last_attempt + delay) {
/* We should mark this retriable. */
char tbuf[ISO_TIME_LEN+1];
format_local_iso_time(tbuf, last_attempt);
log_info(LD_GUARD, "Marked %s%sguard %s for possible retry, since we "
"haven't tried to use it since %s.",
guard->is_primary?"primary ":"",
guard->confirmed_idx>=0?"confirmed ":"",
entry_guard_describe(guard),
tbuf);
guard->is_reachable = GUARD_REACHABLE_MAYBE;
if (guard->is_filtered_guard)
guard->is_usable_filtered_guard = 1;
}
}
/** Tell the entry guards subsystem that we have confirmed that as of
* just now, we're on the internet. */
void
entry_guards_note_internet_connectivity(guard_selection_t *gs)
{
gs->last_time_on_internet = approx_time();
}
/**
* Get a guard for use with a circuit. Prefer to pick a running primary
* guard; then a non-pending running filtered confirmed guard; then a
* non-pending runnable filtered guard. Update the
* <b>last_tried_to_connect</b> time and the <b>is_pending</b> fields of the
* guard as appropriate. Set <b>state_out</b> to the new guard-state
* of the circuit.
*/
STATIC entry_guard_t *
select_entry_guard_for_circuit(guard_selection_t *gs,
guard_usage_t usage,
const entry_guard_restriction_t *rst,
unsigned *state_out)
{
const int need_descriptor = (usage == GUARD_USAGE_TRAFFIC);
tor_assert(gs);
tor_assert(state_out);
if (!gs->primary_guards_up_to_date)
entry_guards_update_primary(gs);
int num_entry_guards = get_n_primary_guards_to_use(usage);
smartlist_t *usable_primary_guards = smartlist_new();
/* "If any entry in PRIMARY_GUARDS has {is_reachable} status of
<maybe> or <yes>, return the first such guard." */
SMARTLIST_FOREACH_BEGIN(gs->primary_entry_guards, entry_guard_t *, guard) {
entry_guard_consider_retry(guard);
if (! entry_guard_obeys_restriction(guard, rst))
continue;
if (guard->is_reachable != GUARD_REACHABLE_NO) {
if (need_descriptor && !guard_has_descriptor(guard)) {
continue;
}
*state_out = GUARD_CIRC_STATE_USABLE_ON_COMPLETION;
guard->last_tried_to_connect = approx_time();
smartlist_add(usable_primary_guards, guard);
if (smartlist_len(usable_primary_guards) >= num_entry_guards)
break;
}
} SMARTLIST_FOREACH_END(guard);
if (smartlist_len(usable_primary_guards)) {
entry_guard_t *guard = smartlist_choose(usable_primary_guards);
smartlist_free(usable_primary_guards);
log_info(LD_GUARD, "Selected primary guard %s for circuit.",
entry_guard_describe(guard));
return guard;
}
smartlist_free(usable_primary_guards);
/* "Otherwise, if the ordered intersection of {CONFIRMED_GUARDS}
and {USABLE_FILTERED_GUARDS} is nonempty, return the first
entry in that intersection that has {is_pending} set to
false." */
SMARTLIST_FOREACH_BEGIN(gs->confirmed_entry_guards, entry_guard_t *, guard) {
if (guard->is_primary)
continue; /* we already considered this one. */
if (! entry_guard_obeys_restriction(guard, rst))
continue;
entry_guard_consider_retry(guard);
if (guard->is_usable_filtered_guard && ! guard->is_pending) {
if (need_descriptor && !guard_has_descriptor(guard))
continue; /* not a bug */
guard->is_pending = 1;
guard->last_tried_to_connect = approx_time();
*state_out = GUARD_CIRC_STATE_USABLE_IF_NO_BETTER_GUARD;
log_info(LD_GUARD, "No primary guards available. Selected confirmed "
"guard %s for circuit. Will try other guards before using "
"this circuit.",
entry_guard_describe(guard));
return guard;
}
} SMARTLIST_FOREACH_END(guard);
/* "Otherwise, if there is no such entry, select a member at
random from {USABLE_FILTERED_GUARDS}." */
{
entry_guard_t *guard;
unsigned flags = 0;
if (need_descriptor)
flags |= SAMPLE_EXCLUDE_NO_DESCRIPTOR;
guard = sample_reachable_filtered_entry_guards(gs,
rst,
SAMPLE_EXCLUDE_CONFIRMED |
SAMPLE_EXCLUDE_PRIMARY |
SAMPLE_EXCLUDE_PENDING |
flags);
if (guard == NULL) {
log_info(LD_GUARD, "Absolutely no sampled guards were available. "
"Marking all guards for retry and starting from top again.");
mark_all_guards_maybe_reachable(gs);
return NULL;
}
guard->is_pending = 1;
guard->last_tried_to_connect = approx_time();
*state_out = GUARD_CIRC_STATE_USABLE_IF_NO_BETTER_GUARD;
log_info(LD_GUARD, "No primary or confirmed guards available. Selected "
"random guard %s for circuit. Will try other guards before "
"using this circuit.",
entry_guard_describe(guard));
return guard;
}
}
/**
* Note that we failed to connect to or build circuits through <b>guard</b>.
* Use with a guard returned by select_entry_guard_for_circuit().
*/
STATIC void
entry_guards_note_guard_failure(guard_selection_t *gs,
entry_guard_t *guard)
{
tor_assert(gs);
guard->is_reachable = GUARD_REACHABLE_NO;
guard->is_usable_filtered_guard = 0;
guard->is_pending = 0;
if (guard->failing_since == 0)
guard->failing_since = approx_time();
log_info(LD_GUARD, "Recorded failure for %s%sguard %s",
guard->is_primary?"primary ":"",
guard->confirmed_idx>=0?"confirmed ":"",
entry_guard_describe(guard));
}
/**
* Note that we successfully connected to, and built a circuit through
* <b>guard</b>. Given the old guard-state of the circuit in <b>old_state</b>,
* return the new guard-state of the circuit.
*
* Be aware: the circuit is only usable when its guard-state becomes
* GUARD_CIRC_STATE_COMPLETE.
**/
STATIC unsigned
entry_guards_note_guard_success(guard_selection_t *gs,
entry_guard_t *guard,
unsigned old_state)
{
tor_assert(gs);
/* Save this, since we're about to overwrite it. */
const time_t last_time_on_internet = gs->last_time_on_internet;
gs->last_time_on_internet = approx_time();
guard->is_reachable = GUARD_REACHABLE_YES;
guard->failing_since = 0;
guard->is_pending = 0;
if (guard->is_filtered_guard)
guard->is_usable_filtered_guard = 1;
if (guard->confirmed_idx < 0) {
make_guard_confirmed(gs, guard);
if (!gs->primary_guards_up_to_date)
entry_guards_update_primary(gs);
}
unsigned new_state;
switch (old_state) {
case GUARD_CIRC_STATE_COMPLETE:
case GUARD_CIRC_STATE_USABLE_ON_COMPLETION:
new_state = GUARD_CIRC_STATE_COMPLETE;
break;
default:
tor_assert_nonfatal_unreached();
/* Fall through. */
case GUARD_CIRC_STATE_USABLE_IF_NO_BETTER_GUARD:
if (guard->is_primary) {
/* XXXX #20832 -- I don't actually like this logic. It seems to make
* us a little more susceptible to evil-ISP attacks. The mitigations
* I'm thinking of, however, aren't local to this point, so I'll leave
* it alone. */
/* This guard may have become primary by virtue of being confirmed.
* If so, the circuit for it is now complete.
*/
new_state = GUARD_CIRC_STATE_COMPLETE;
} else {
new_state = GUARD_CIRC_STATE_WAITING_FOR_BETTER_GUARD;
}
break;
}
if (! guard->is_primary) {
if (last_time_on_internet + get_internet_likely_down_interval()
< approx_time()) {
mark_primary_guards_maybe_reachable(gs);
}
}
log_info(LD_GUARD, "Recorded success for %s%sguard %s",
guard->is_primary?"primary ":"",
guard->confirmed_idx>=0?"confirmed ":"",
entry_guard_describe(guard));
return new_state;
}
/**
* Helper: Return true iff <b>a</b> has higher priority than <b>b</b>.
*/
STATIC int
entry_guard_has_higher_priority(entry_guard_t *a, entry_guard_t *b)
{
tor_assert(a && b);
if (a == b)
return 0;
/* Confirmed is always better than unconfirmed; lower index better
than higher */
if (a->confirmed_idx < 0) {
if (b->confirmed_idx >= 0)
return 0;
} else {
if (b->confirmed_idx < 0)
return 1;
/* Lower confirmed_idx is better than higher. */
return (a->confirmed_idx < b->confirmed_idx);
}
/* If we reach this point, both are unconfirmed. If one is pending, it
* has higher priority. */
if (a->is_pending) {
if (! b->is_pending)
return 1;
/* Both are pending: earlier last_tried_connect wins. */
return a->last_tried_to_connect < b->last_tried_to_connect;
} else {
if (b->is_pending)
return 0;
/* Neither is pending: priorities are equal. */
return 0;
}
}
/** Release all storage held in <b>restriction</b> */
STATIC void
entry_guard_restriction_free_(entry_guard_restriction_t *rst)
{
tor_free(rst);
}
/**
* Release all storage held in <b>state</b>.
*/
void
circuit_guard_state_free_(circuit_guard_state_t *state)
{
if (!state)
return;
entry_guard_restriction_free(state->restrictions);
entry_guard_handle_free(state->guard);
tor_free(state);
}
/** Allocate and return a new circuit_guard_state_t to track the result
* of using <b>guard</b> for a given operation. */
MOCK_IMPL(STATIC circuit_guard_state_t *,
circuit_guard_state_new,(entry_guard_t *guard, unsigned state,
entry_guard_restriction_t *rst))
{
circuit_guard_state_t *result;
result = tor_malloc_zero(sizeof(circuit_guard_state_t));
result->guard = entry_guard_handle_new(guard);
result->state = state;
result->state_set_at = approx_time();
result->restrictions = rst;
return result;
}
/**
* Pick a suitable entry guard for a circuit in, and place that guard
* in *<b>chosen_node_out</b>. Set *<b>guard_state_out</b> to an opaque
* state object that will record whether the circuit is ready to be used
* or not. Return 0 on success; on failure, return -1.
*
* If a restriction is provided in <b>rst</b>, do not return any guards that
* violate it, and remember that restriction in <b>guard_state_out</b> for
* later use. (Takes ownership of the <b>rst</b> object.)
*/
int
entry_guard_pick_for_circuit(guard_selection_t *gs,
guard_usage_t usage,
entry_guard_restriction_t *rst,
const node_t **chosen_node_out,
circuit_guard_state_t **guard_state_out)
{
tor_assert(gs);
tor_assert(chosen_node_out);
tor_assert(guard_state_out);
*chosen_node_out = NULL;
*guard_state_out = NULL;
unsigned state = 0;
entry_guard_t *guard =
select_entry_guard_for_circuit(gs, usage, rst, &state);
if (! guard)
goto fail;
if (BUG(state == 0))
goto fail;
const node_t *node = node_get_by_id(guard->identity);
// XXXX #20827 check Ed ID.
if (! node)
goto fail;
if (BUG(usage != GUARD_USAGE_DIRGUARD &&
!node_has_preferred_descriptor(node, 1)))
goto fail;
*chosen_node_out = node;
*guard_state_out = circuit_guard_state_new(guard, state, rst);
return 0;
fail:
entry_guard_restriction_free(rst);
return -1;
}
/**
* Called by the circuit building module when a circuit has succeeded: informs
* the guards code that the guard in *<b>guard_state_p</b> is working, and
* advances the state of the guard module. On a GUARD_USABLE_NEVER return
* value, the circuit is broken and should not be used. On a GUARD_USABLE_NOW
* return value, the circuit is ready to use. On a GUARD_MAYBE_USABLE_LATER
* return value, the circuit should not be used until we find out whether
* preferred guards will work for us.
*/
guard_usable_t
entry_guard_succeeded(circuit_guard_state_t **guard_state_p)
{
if (BUG(*guard_state_p == NULL))
return GUARD_USABLE_NEVER;
entry_guard_t *guard = entry_guard_handle_get((*guard_state_p)->guard);
if (! guard || BUG(guard->in_selection == NULL))
return GUARD_USABLE_NEVER;
unsigned newstate =
entry_guards_note_guard_success(guard->in_selection, guard,
(*guard_state_p)->state);
(*guard_state_p)->state = newstate;
(*guard_state_p)->state_set_at = approx_time();
if (newstate == GUARD_CIRC_STATE_COMPLETE) {
return GUARD_USABLE_NOW;
} else {
return GUARD_MAYBE_USABLE_LATER;
}
}
/** Cancel the selection of *<b>guard_state_p</b> without declaring
* success or failure. It is safe to call this function if success or
* failure _has_ already been declared. */
void
entry_guard_cancel(circuit_guard_state_t **guard_state_p)
{
if (BUG(*guard_state_p == NULL))
return;
entry_guard_t *guard = entry_guard_handle_get((*guard_state_p)->guard);
if (! guard)
return;
/* XXXX prop271 -- last_tried_to_connect_at will be erroneous here, but this
* function will only get called in "bug" cases anyway. */
guard->is_pending = 0;
circuit_guard_state_free(*guard_state_p);
*guard_state_p = NULL;
}
/**
* Called by the circuit building module when a circuit has failed:
* informs the guards code that the guard in *<b>guard_state_p</b> is
* not working, and advances the state of the guard module.
*/
void
entry_guard_failed(circuit_guard_state_t **guard_state_p)
{
if (BUG(*guard_state_p == NULL))
return;
entry_guard_t *guard = entry_guard_handle_get((*guard_state_p)->guard);
if (! guard || BUG(guard->in_selection == NULL))
return;
entry_guards_note_guard_failure(guard->in_selection, guard);
(*guard_state_p)->state = GUARD_CIRC_STATE_DEAD;
(*guard_state_p)->state_set_at = approx_time();
}
/**
* Run the entry_guard_failed() function on every circuit that is
* pending on <b>chan</b>.
*/
void
entry_guard_chan_failed(channel_t *chan)
{
if (!chan)
return;
smartlist_t *pending = smartlist_new();
circuit_get_all_pending_on_channel(pending, chan);
SMARTLIST_FOREACH_BEGIN(pending, circuit_t *, circ) {
if (!CIRCUIT_IS_ORIGIN(circ))
continue;
origin_circuit_t *origin_circ = TO_ORIGIN_CIRCUIT(circ);
if (origin_circ->guard_state) {
/* We might have no guard state if we didn't use a guard on this
* circuit (eg it's for a fallback directory). */
entry_guard_failed(&origin_circ->guard_state);
}
} SMARTLIST_FOREACH_END(circ);
smartlist_free(pending);
}
/**
* Return true iff every primary guard in <b>gs</b> is believed to
* be unreachable.
*/
STATIC int
entry_guards_all_primary_guards_are_down(guard_selection_t *gs)
{
tor_assert(gs);
if (!gs->primary_guards_up_to_date)
entry_guards_update_primary(gs);
SMARTLIST_FOREACH_BEGIN(gs->primary_entry_guards, entry_guard_t *, guard) {
entry_guard_consider_retry(guard);
if (guard->is_reachable != GUARD_REACHABLE_NO)
return 0;
} SMARTLIST_FOREACH_END(guard);
return 1;
}
/** Wrapper for entry_guard_has_higher_priority that compares the
* guard-priorities of a pair of circuits. Return 1 if <b>a</b> has higher
* priority than <b>b</b>.
*
* If a restriction is provided in <b>rst</b>, then do not consider
* <b>a</b> to have higher priority if it violates the restriction.
*/
static int
circ_state_has_higher_priority(origin_circuit_t *a,
const entry_guard_restriction_t *rst,
origin_circuit_t *b)
{
circuit_guard_state_t *state_a = origin_circuit_get_guard_state(a);
circuit_guard_state_t *state_b = origin_circuit_get_guard_state(b);
tor_assert(state_a);
tor_assert(state_b);
entry_guard_t *guard_a = entry_guard_handle_get(state_a->guard);
entry_guard_t *guard_b = entry_guard_handle_get(state_b->guard);
if (! guard_a) {
/* Unknown guard -- never higher priority. */
return 0;
} else if (! guard_b) {
/* Known guard -- higher priority than any unknown guard. */
return 1;
} else if (! entry_guard_obeys_restriction(guard_a, rst)) {
/* Restriction violated; guard_a cannot have higher priority. */
return 0;
} else {
/* Both known -- compare.*/
return entry_guard_has_higher_priority(guard_a, guard_b);
}
}
/**
* Look at all of the origin_circuit_t * objects in <b>all_circuits_in</b>,
* and see if any of them that were previously not ready to use for
* guard-related reasons are now ready to use. Place those circuits
* in <b>newly_complete_out</b>, and mark them COMPLETE.
*
* Return 1 if we upgraded any circuits, and 0 otherwise.
*/
int
entry_guards_upgrade_waiting_circuits(guard_selection_t *gs,
const smartlist_t *all_circuits_in,
smartlist_t *newly_complete_out)
{
tor_assert(gs);
tor_assert(all_circuits_in);
tor_assert(newly_complete_out);
if (! entry_guards_all_primary_guards_are_down(gs)) {
/* We only upgrade a waiting circuit if the primary guards are all
* down. */
log_debug(LD_GUARD, "Considered upgrading guard-stalled circuits, "
"but not all primary guards were definitely down.");
return 0;
}
int n_waiting = 0;
int n_complete = 0;
int n_complete_blocking = 0;
origin_circuit_t *best_waiting_circuit = NULL;
smartlist_t *all_circuits = smartlist_new();
SMARTLIST_FOREACH_BEGIN(all_circuits_in, origin_circuit_t *, circ) {
// We filter out circuits that aren't ours, or which we can't
// reason about.
circuit_guard_state_t *state = origin_circuit_get_guard_state(circ);
if (state == NULL)
continue;
entry_guard_t *guard = entry_guard_handle_get(state->guard);
if (!guard || guard->in_selection != gs)
continue;
smartlist_add(all_circuits, circ);
} SMARTLIST_FOREACH_END(circ);
SMARTLIST_FOREACH_BEGIN(all_circuits, origin_circuit_t *, circ) {
circuit_guard_state_t *state = origin_circuit_get_guard_state(circ);
if (BUG(state == NULL))
continue;
if (state->state == GUARD_CIRC_STATE_WAITING_FOR_BETTER_GUARD) {
++n_waiting;
if (! best_waiting_circuit ||
circ_state_has_higher_priority(circ, NULL, best_waiting_circuit)) {
best_waiting_circuit = circ;
}
}
} SMARTLIST_FOREACH_END(circ);
if (! best_waiting_circuit) {
log_debug(LD_GUARD, "Considered upgrading guard-stalled circuits, "
"but didn't find any.");
goto no_change;
}
/* We'll need to keep track of what restrictions were used when picking this
* circuit, so that we don't allow any circuit without those restrictions to
* block it. */
const entry_guard_restriction_t *rst_on_best_waiting =
origin_circuit_get_guard_state(best_waiting_circuit)->restrictions;
/* First look at the complete circuits: Do any block this circuit? */
SMARTLIST_FOREACH_BEGIN(all_circuits, origin_circuit_t *, circ) {
/* "C2 "blocks" C1 if:
* C2 obeys all the restrictions that C1 had to obey, AND
* C2 has higher priority than C1, AND
* Either C2 is <complete>, or C2 is <waiting_for_better_guard>,
or C2 has been <usable_if_no_better_guard> for no more than
{NONPRIMARY_GUARD_CONNECT_TIMEOUT} seconds."
*/
circuit_guard_state_t *state = origin_circuit_get_guard_state(circ);
if BUG((state == NULL))
continue;
if (state->state != GUARD_CIRC_STATE_COMPLETE)
continue;
++n_complete;
if (circ_state_has_higher_priority(circ, rst_on_best_waiting,
best_waiting_circuit))
++n_complete_blocking;
} SMARTLIST_FOREACH_END(circ);
if (n_complete_blocking) {
log_debug(LD_GUARD, "Considered upgrading guard-stalled circuits: found "
"%d complete and %d guard-stalled. At least one complete "
"circuit had higher priority, so not upgrading.",
n_complete, n_waiting);
goto no_change;
}
/* " * If any circuit C1 is <waiting_for_better_guard>, AND:
* All primary guards have reachable status of <no>.
* There is no circuit C2 that "blocks" C1.
Then, upgrade C1 to <complete>.""
*/
int n_blockers_found = 0;
const time_t state_set_at_cutoff =
approx_time() - get_nonprimary_guard_connect_timeout();
SMARTLIST_FOREACH_BEGIN(all_circuits, origin_circuit_t *, circ) {
circuit_guard_state_t *state = origin_circuit_get_guard_state(circ);
if (BUG(state == NULL))
continue;
if (state->state != GUARD_CIRC_STATE_USABLE_IF_NO_BETTER_GUARD)
continue;
if (state->state_set_at <= state_set_at_cutoff)
continue;
if (circ_state_has_higher_priority(circ, rst_on_best_waiting,
best_waiting_circuit))
++n_blockers_found;
} SMARTLIST_FOREACH_END(circ);
if (n_blockers_found) {
log_debug(LD_GUARD, "Considered upgrading guard-stalled circuits: found "
"%d guard-stalled, but %d pending circuit(s) had higher "
"guard priority, so not upgrading.",
n_waiting, n_blockers_found);
goto no_change;
}
/* Okay. We have a best waiting circuit, and we aren't waiting for
anything better. Add all circuits with that priority to the
list, and call them COMPLETE. */
int n_succeeded = 0;
SMARTLIST_FOREACH_BEGIN(all_circuits, origin_circuit_t *, circ) {
circuit_guard_state_t *state = origin_circuit_get_guard_state(circ);
if (BUG(state == NULL))
continue;
if (circ != best_waiting_circuit && rst_on_best_waiting) {
/* Can't upgrade other circ with same priority as best; might
be blocked. */
continue;
}
if (state->state != GUARD_CIRC_STATE_WAITING_FOR_BETTER_GUARD)
continue;
if (circ_state_has_higher_priority(best_waiting_circuit, NULL, circ))
continue;
state->state = GUARD_CIRC_STATE_COMPLETE;
state->state_set_at = approx_time();
smartlist_add(newly_complete_out, circ);
++n_succeeded;
} SMARTLIST_FOREACH_END(circ);
log_info(LD_GUARD, "Considered upgrading guard-stalled circuits: found "
"%d guard-stalled, %d complete. %d of the guard-stalled "
"circuit(s) had high enough priority to upgrade.",
n_waiting, n_complete, n_succeeded);
tor_assert_nonfatal(n_succeeded >= 1);
smartlist_free(all_circuits);
return 1;
no_change:
smartlist_free(all_circuits);
return 0;
}
/**
* Return true iff the circuit whose state is <b>guard_state</b> should
* expire.
*/
int
entry_guard_state_should_expire(circuit_guard_state_t *guard_state)
{
if (guard_state == NULL)
return 0;
const time_t expire_if_waiting_since =
approx_time() - get_nonprimary_guard_idle_timeout();
return (guard_state->state == GUARD_CIRC_STATE_WAITING_FOR_BETTER_GUARD
&& guard_state->state_set_at < expire_if_waiting_since);
}
/**
* Update all derived pieces of the guard selection state in <b>gs</b>.
* Return true iff we should stop using all previously generated circuits.
*/
int
entry_guards_update_all(guard_selection_t *gs)
{
sampled_guards_update_from_consensus(gs);
entry_guards_update_filtered_sets(gs);
entry_guards_update_confirmed(gs);
entry_guards_update_primary(gs);
return 0;
}
/**
* Return a newly allocated string for encoding the persistent parts of
* <b>guard</b> to the state file.
*/
STATIC char *
entry_guard_encode_for_state(entry_guard_t *guard)
{
/*
* The meta-format we use is K=V K=V K=V... where K can be any
* characters excepts space and =, and V can be any characters except
* space. The order of entries is not allowed to matter.
* Unrecognized K=V entries are persisted; recognized but erroneous
* entries are corrected.
*/
smartlist_t *result = smartlist_new();
char tbuf[ISO_TIME_LEN+1];
tor_assert(guard);
smartlist_add_asprintf(result, "in=%s", guard->selection_name);
smartlist_add_asprintf(result, "rsa_id=%s",
hex_str(guard->identity, DIGEST_LEN));
if (guard->bridge_addr) {
smartlist_add_asprintf(result, "bridge_addr=%s:%d",
fmt_and_decorate_addr(&guard->bridge_addr->addr),
guard->bridge_addr->port);
}
if (strlen(guard->nickname) && is_legal_nickname(guard->nickname)) {
smartlist_add_asprintf(result, "nickname=%s", guard->nickname);
}
format_iso_time_nospace(tbuf, guard->sampled_on_date);
smartlist_add_asprintf(result, "sampled_on=%s", tbuf);
if (guard->sampled_by_version) {
smartlist_add_asprintf(result, "sampled_by=%s",
guard->sampled_by_version);
}
if (guard->unlisted_since_date > 0) {
format_iso_time_nospace(tbuf, guard->unlisted_since_date);
smartlist_add_asprintf(result, "unlisted_since=%s", tbuf);
}
smartlist_add_asprintf(result, "listed=%d",
(int)guard->currently_listed);
if (guard->confirmed_idx >= 0) {
format_iso_time_nospace(tbuf, guard->confirmed_on_date);
smartlist_add_asprintf(result, "confirmed_on=%s", tbuf);
smartlist_add_asprintf(result, "confirmed_idx=%d", guard->confirmed_idx);
}
const double EPSILON = 1.0e-6;
/* Make a copy of the pathbias object, since we will want to update
some of them */
guard_pathbias_t *pb = tor_memdup(&guard->pb, sizeof(*pb));
pb->use_successes = pathbias_get_use_success_count(guard);
pb->successful_circuits_closed = pathbias_get_close_success_count(guard);
#define PB_FIELD(field) do { \
if (pb->field >= EPSILON) { \
smartlist_add_asprintf(result, "pb_" #field "=%f", pb->field); \
} \
} while (0)
PB_FIELD(use_attempts);
PB_FIELD(use_successes);
PB_FIELD(circ_attempts);
PB_FIELD(circ_successes);
PB_FIELD(successful_circuits_closed);
PB_FIELD(collapsed_circuits);
PB_FIELD(unusable_circuits);
PB_FIELD(timeouts);
tor_free(pb);
#undef PB_FIELD
if (guard->extra_state_fields)
smartlist_add_strdup(result, guard->extra_state_fields);
char *joined = smartlist_join_strings(result, " ", 0, NULL);
SMARTLIST_FOREACH(result, char *, cp, tor_free(cp));
smartlist_free(result);
return joined;
}
/**
* Given a string generated by entry_guard_encode_for_state(), parse it
* (if possible) and return an entry_guard_t object for it. Return NULL
* on complete failure.
*/
STATIC entry_guard_t *
entry_guard_parse_from_state(const char *s)
{
/* Unrecognized entries get put in here. */
smartlist_t *extra = smartlist_new();
/* These fields get parsed from the string. */
char *in = NULL;
char *rsa_id = NULL;
char *nickname = NULL;
char *sampled_on = NULL;
char *sampled_by = NULL;
char *unlisted_since = NULL;
char *listed = NULL;
char *confirmed_on = NULL;
char *confirmed_idx = NULL;
char *bridge_addr = NULL;
// pathbias
char *pb_use_attempts = NULL;
char *pb_use_successes = NULL;
char *pb_circ_attempts = NULL;
char *pb_circ_successes = NULL;
char *pb_successful_circuits_closed = NULL;
char *pb_collapsed_circuits = NULL;
char *pb_unusable_circuits = NULL;
char *pb_timeouts = NULL;
/* Split up the entries. Put the ones we know about in strings and the
* rest in "extra". */
{
smartlist_t *entries = smartlist_new();
strmap_t *vals = strmap_new(); // Maps keyword to location
#define FIELD(f) \
strmap_set(vals, #f, &f);
FIELD(in);
FIELD(rsa_id);
FIELD(nickname);
FIELD(sampled_on);
FIELD(sampled_by);
FIELD(unlisted_since);
FIELD(listed);
FIELD(confirmed_on);
FIELD(confirmed_idx);
FIELD(bridge_addr);
FIELD(pb_use_attempts);
FIELD(pb_use_successes);
FIELD(pb_circ_attempts);
FIELD(pb_circ_successes);
FIELD(pb_successful_circuits_closed);
FIELD(pb_collapsed_circuits);
FIELD(pb_unusable_circuits);
FIELD(pb_timeouts);
#undef FIELD
smartlist_split_string(entries, s, " ",
SPLIT_SKIP_SPACE|SPLIT_IGNORE_BLANK, 0);
SMARTLIST_FOREACH_BEGIN(entries, char *, entry) {
const char *eq = strchr(entry, '=');
if (!eq) {
smartlist_add(extra, entry);
continue;
}
char *key = tor_strndup(entry, eq-entry);
char **target = strmap_get(vals, key);
if (target == NULL || *target != NULL) {
/* unrecognized or already set */
smartlist_add(extra, entry);
tor_free(key);
continue;
}
*target = tor_strdup(eq+1);
tor_free(key);
tor_free(entry);
} SMARTLIST_FOREACH_END(entry);
smartlist_free(entries);
strmap_free(vals, NULL);
}
entry_guard_t *guard = tor_malloc_zero(sizeof(entry_guard_t));
guard->is_persistent = 1;
if (in == NULL) {
log_warn(LD_CIRC, "Guard missing 'in' field");
goto err;
}
guard->selection_name = in;
in = NULL;
if (rsa_id == NULL) {
log_warn(LD_CIRC, "Guard missing RSA ID field");
goto err;
}
/* Process the identity and nickname. */
if (base16_decode(guard->identity, sizeof(guard->identity),
rsa_id, strlen(rsa_id)) != DIGEST_LEN) {
log_warn(LD_CIRC, "Unable to decode guard identity %s", escaped(rsa_id));
goto err;
}
if (nickname) {
strlcpy(guard->nickname, nickname, sizeof(guard->nickname));
} else {
guard->nickname[0]='$';
base16_encode(guard->nickname+1, sizeof(guard->nickname)-1,
guard->identity, DIGEST_LEN);
}
if (bridge_addr) {
tor_addr_port_t res;
memset(&res, 0, sizeof(res));
int r = tor_addr_port_parse(LOG_WARN, bridge_addr,
&res.addr, &res.port, -1);
if (r == 0)
guard->bridge_addr = tor_memdup(&res, sizeof(res));
/* On error, we already warned. */
}
/* Process the various time fields. */
#define HANDLE_TIME(field) do { \
if (field) { \
int r = parse_iso_time_nospace(field, &field ## _time); \
if (r < 0) { \
log_warn(LD_CIRC, "Unable to parse %s %s from guard", \
#field, escaped(field)); \
field##_time = -1; \
} \
} \
} while (0)
time_t sampled_on_time = 0;
time_t unlisted_since_time = 0;
time_t confirmed_on_time = 0;
HANDLE_TIME(sampled_on);
HANDLE_TIME(unlisted_since);
HANDLE_TIME(confirmed_on);
if (sampled_on_time <= 0)
sampled_on_time = approx_time();
if (unlisted_since_time < 0)
unlisted_since_time = 0;
if (confirmed_on_time < 0)
confirmed_on_time = 0;
#undef HANDLE_TIME
guard->sampled_on_date = sampled_on_time;
guard->unlisted_since_date = unlisted_since_time;
guard->confirmed_on_date = confirmed_on_time;
/* Take sampled_by_version verbatim. */
guard->sampled_by_version = sampled_by;
sampled_by = NULL; /* prevent free */
/* Listed is a boolean */
if (listed && strcmp(listed, "0"))
guard->currently_listed = 1;
/* The index is a nonnegative integer. */
guard->confirmed_idx = -1;
if (confirmed_idx) {
int ok=1;
long idx = tor_parse_long(confirmed_idx, 10, 0, INT_MAX, &ok, NULL);
if (! ok) {
log_warn(LD_GUARD, "Guard has invalid confirmed_idx %s",
escaped(confirmed_idx));
} else {
guard->confirmed_idx = (int)idx;
}
}
/* Anything we didn't recognize gets crammed together */
if (smartlist_len(extra) > 0) {
guard->extra_state_fields = smartlist_join_strings(extra, " ", 0, NULL);
}
/* initialize non-persistent fields */
guard->is_reachable = GUARD_REACHABLE_MAYBE;
#define PB_FIELD(field) \
do { \
if (pb_ ## field) { \
int ok = 1; \
double r = tor_parse_double(pb_ ## field, 0.0, 1e9, &ok, NULL); \
if (! ok) { \
log_warn(LD_CIRC, "Guard has invalid pb_%s %s", \
#field, pb_ ## field); \
} else { \
guard->pb.field = r; \
} \
} \
} while (0)
PB_FIELD(use_attempts);
PB_FIELD(use_successes);
PB_FIELD(circ_attempts);
PB_FIELD(circ_successes);
PB_FIELD(successful_circuits_closed);
PB_FIELD(collapsed_circuits);
PB_FIELD(unusable_circuits);
PB_FIELD(timeouts);
#undef PB_FIELD
pathbias_check_use_success_count(guard);
pathbias_check_close_success_count(guard);
/* We update everything on this guard later, after we've parsed
* everything. */
goto done;
err:
// only consider it an error if the guard state was totally unparseable.
entry_guard_free(guard);
guard = NULL;
done:
tor_free(in);
tor_free(rsa_id);
tor_free(nickname);
tor_free(sampled_on);
tor_free(sampled_by);
tor_free(unlisted_since);
tor_free(listed);
tor_free(confirmed_on);
tor_free(confirmed_idx);
tor_free(bridge_addr);
tor_free(pb_use_attempts);
tor_free(pb_use_successes);
tor_free(pb_circ_attempts);
tor_free(pb_circ_successes);
tor_free(pb_successful_circuits_closed);
tor_free(pb_collapsed_circuits);
tor_free(pb_unusable_circuits);
tor_free(pb_timeouts);
SMARTLIST_FOREACH(extra, char *, cp, tor_free(cp));
smartlist_free(extra);
return guard;
}
/**
* Replace the Guards entries in <b>state</b> with a list of all our sampled
* guards.
*/
static void
entry_guards_update_guards_in_state(or_state_t *state)
{
if (!guard_contexts)
return;
config_line_t *lines = NULL;
config_line_t **nextline = &lines;
SMARTLIST_FOREACH_BEGIN(guard_contexts, guard_selection_t *, gs) {
SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
if (guard->is_persistent == 0)
continue;
*nextline = tor_malloc_zero(sizeof(config_line_t));
(*nextline)->key = tor_strdup("Guard");
(*nextline)->value = entry_guard_encode_for_state(guard);
nextline = &(*nextline)->next;
} SMARTLIST_FOREACH_END(guard);
} SMARTLIST_FOREACH_END(gs);
config_free_lines(state->Guard);
state->Guard = lines;
}
/**
* Replace our sampled guards from the Guards entries in <b>state</b>. Return 0
* on success, -1 on failure. (If <b>set</b> is true, replace nothing -- only
* check whether replacing would work.)
*/
static int
entry_guards_load_guards_from_state(or_state_t *state, int set)
{
const config_line_t *line = state->Guard;
int n_errors = 0;
if (!guard_contexts)
guard_contexts = smartlist_new();
/* Wipe all our existing guard info. (we shouldn't have any, but
* let's be safe.) */
if (set) {
SMARTLIST_FOREACH_BEGIN(guard_contexts, guard_selection_t *, gs) {
guard_selection_free(gs);
if (curr_guard_context == gs)
curr_guard_context = NULL;
SMARTLIST_DEL_CURRENT(guard_contexts, gs);
} SMARTLIST_FOREACH_END(gs);
}
for ( ; line != NULL; line = line->next) {
entry_guard_t *guard = entry_guard_parse_from_state(line->value);
if (guard == NULL) {
++n_errors;
continue;
}
tor_assert(guard->selection_name);
if (!strcmp(guard->selection_name, "legacy")) {
++n_errors;
entry_guard_free(guard);
continue;
}
if (set) {
guard_selection_t *gs;
gs = get_guard_selection_by_name(guard->selection_name,
GS_TYPE_INFER, 1);
tor_assert(gs);
smartlist_add(gs->sampled_entry_guards, guard);
guard->in_selection = gs;
} else {
entry_guard_free(guard);
}
}
if (set) {
SMARTLIST_FOREACH_BEGIN(guard_contexts, guard_selection_t *, gs) {
entry_guards_update_all(gs);
} SMARTLIST_FOREACH_END(gs);
}
return n_errors ? -1 : 0;
}
/** If <b>digest</b> matches the identity of any node in the
* entry_guards list for the provided guard selection state,
return that node. Else return NULL. */
entry_guard_t *
entry_guard_get_by_id_digest_for_guard_selection(guard_selection_t *gs,
const char *digest)
{
return get_sampled_guard_with_id(gs, (const uint8_t*)digest);
}
/** Return the node_t associated with a single entry_guard_t. May
* return NULL if the guard is not currently in the consensus. */
const node_t *
entry_guard_find_node(const entry_guard_t *guard)
{
tor_assert(guard);
return node_get_by_id(guard->identity);
}
/** If <b>digest</b> matches the identity of any node in the
* entry_guards list for the default guard selection state,
return that node. Else return NULL. */
entry_guard_t *
entry_guard_get_by_id_digest(const char *digest)
{
return entry_guard_get_by_id_digest_for_guard_selection(
get_guard_selection_info(), digest);
}
/** We are about to connect to bridge with identity <b>digest</b> to fetch its
* descriptor. Create a new guard state for this connection and return it. */
circuit_guard_state_t *
get_guard_state_for_bridge_desc_fetch(const char *digest)
{
circuit_guard_state_t *guard_state = NULL;
entry_guard_t *guard = NULL;
guard = entry_guard_get_by_id_digest_for_guard_selection(
get_guard_selection_info(), digest);
if (!guard) {
return NULL;
}
/* Update the guard last_tried_to_connect time since it's checked by the
* guard susbsystem. */
guard->last_tried_to_connect = approx_time();
/* Create the guard state */
guard_state = circuit_guard_state_new(guard,
GUARD_CIRC_STATE_USABLE_ON_COMPLETION,
NULL);
return guard_state;
}
/** Release all storage held by <b>e</b>. */
STATIC void
entry_guard_free_(entry_guard_t *e)
{
if (!e)
return;
entry_guard_handles_clear(e);
tor_free(e->sampled_by_version);
tor_free(e->extra_state_fields);
tor_free(e->selection_name);
tor_free(e->bridge_addr);
tor_free(e);
}
/** Return 0 if we're fine adding arbitrary routers out of the
* directory to our entry guard list, or return 1 if we have a
* list already and we must stick to it.
*/
int
entry_list_is_constrained(const or_options_t *options)
{
// XXXX #21425 look at the current selection.
if (options->EntryNodes)
return 1;
if (options->UseBridges)
return 1;
return 0;
}
/** Return the number of bridges that have descriptors that are marked with
* purpose 'bridge' and are running. If use_maybe_reachable is
* true, include bridges that might be reachable in the count.
* Otherwise, if it is false, only include bridges that have recently been
* found running in the count.
*
* We use this function to decide if we're ready to start building
* circuits through our bridges, or if we need to wait until the
* directory "server/authority" requests finish. */
MOCK_IMPL(int,
num_bridges_usable,(int use_maybe_reachable))
{
int n_options = 0;
if (BUG(!get_options()->UseBridges)) {
return 0;
}
guard_selection_t *gs = get_guard_selection_info();
if (BUG(gs->type != GS_TYPE_BRIDGE)) {
return 0;
}
SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {
/* Definitely not usable */
if (guard->is_reachable == GUARD_REACHABLE_NO)
continue;
/* If we want to be really sure the bridges will work, skip maybes */
if (!use_maybe_reachable && guard->is_reachable == GUARD_REACHABLE_MAYBE)
continue;
if (tor_digest_is_zero(guard->identity))
continue;
const node_t *node = node_get_by_id(guard->identity);
if (node && node->ri)
++n_options;
} SMARTLIST_FOREACH_END(guard);
return n_options;
}
/** Check the pathbias use success count of <b>node</b> and disable it if it
* goes over our thresholds. */
static void
pathbias_check_use_success_count(entry_guard_t *node)
{
const or_options_t *options = get_options();
const double EPSILON = 1.0e-9;
/* 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 (node->pb.use_attempts > EPSILON &&
pathbias_get_use_success_count(node)/node->pb.use_attempts
< pathbias_get_extreme_use_rate(options) &&
pathbias_get_dropguards(options)) {
node->pb.path_bias_disabled = 1;
log_info(LD_GENERAL,
"Path use bias is too high (%f/%f); disabling node %s",
node->pb.circ_successes, node->pb.circ_attempts,
node->nickname);
}
}
/** Check the pathbias close count of <b>node</b> and disable it if it goes
* over our thresholds. */
static void
pathbias_check_close_success_count(entry_guard_t *node)
{
const or_options_t *options = get_options();
const double EPSILON = 1.0e-9;
/* 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 (node->pb.circ_attempts > EPSILON &&
pathbias_get_close_success_count(node)/node->pb.circ_attempts
< pathbias_get_extreme_rate(options) &&
pathbias_get_dropguards(options)) {
node->pb.path_bias_disabled = 1;
log_info(LD_GENERAL,
"Path bias is too high (%f/%f); disabling node %s",
node->pb.circ_successes, node->pb.circ_attempts,
node->nickname);
}
}
/** Parse <b>state</b> and learn about the entry guards it describes.
* If <b>set</b> is true, and there are no errors, replace the guard
* list in the default guard selection context with what we find.
* On success, return 0. On failure, alloc into *<b>msg</b> a string
* describing the error, and return -1.
*/
int
entry_guards_parse_state(or_state_t *state, int set, char **msg)
{
entry_guards_dirty = 0;
int r1 = entry_guards_load_guards_from_state(state, set);
entry_guards_dirty = 0;
if (r1 < 0) {
if (msg && *msg == NULL) {
*msg = tor_strdup("parsing error");
}
return -1;
}
return 0;
}
/** How long will we let a change in our guard nodes stay un-saved
* when we are trying to avoid disk writes? */
#define SLOW_GUARD_STATE_FLUSH_TIME 600
/** How long will we let a change in our guard nodes stay un-saved
* when we are not trying to avoid disk writes? */
#define FAST_GUARD_STATE_FLUSH_TIME 30
/** Our list of entry guards has changed for a particular guard selection
* context, or some element of one of our entry guards has changed for one.
* Write the changes to disk within the next few minutes.
*/
void
entry_guards_changed_for_guard_selection(guard_selection_t *gs)
{
time_t when;
tor_assert(gs != NULL);
entry_guards_dirty = 1;
if (get_options()->AvoidDiskWrites)
when = time(NULL) + SLOW_GUARD_STATE_FLUSH_TIME;
else
when = time(NULL) + FAST_GUARD_STATE_FLUSH_TIME;
/* or_state_save() will call entry_guards_update_state() and
entry_guards_update_guards_in_state()
*/
or_state_mark_dirty(get_or_state(), when);
}
/** Our list of entry guards has changed for the default guard selection
* context, or some element of one of our entry guards has changed. Write
* the changes to disk within the next few minutes.
*/
void
entry_guards_changed(void)
{
entry_guards_changed_for_guard_selection(get_guard_selection_info());
}
/** If the entry guard info has not changed, do nothing and return.
* Otherwise, free the EntryGuards piece of <b>state</b> and create
* a new one out of the global entry_guards list, and then mark
* <b>state</b> dirty so it will get saved to disk.
*/
void
entry_guards_update_state(or_state_t *state)
{
entry_guards_dirty = 0;
// Handles all guard info.
entry_guards_update_guards_in_state(state);
entry_guards_dirty = 0;
if (!get_options()->AvoidDiskWrites)
or_state_mark_dirty(get_or_state(), 0);
entry_guards_dirty = 0;
}
/** Return true iff the circuit's guard can succeed that is can be used. */
int
entry_guard_could_succeed(const circuit_guard_state_t *guard_state)
{
if (!guard_state) {
return 0;
}
entry_guard_t *guard = entry_guard_handle_get(guard_state->guard);
if (!guard || BUG(guard->in_selection == NULL)) {
return 0;
}
return 1;
}
/**
* Format a single entry guard in the format expected by the controller.
* Return a newly allocated string.
*/
STATIC char *
getinfo_helper_format_single_entry_guard(const entry_guard_t *e)
{
const char *status = NULL;
time_t when = 0;
const node_t *node;
char tbuf[ISO_TIME_LEN+1];
char nbuf[MAX_VERBOSE_NICKNAME_LEN+1];
/* This is going to be a bit tricky, since the status
* codes weren't really intended for prop271 guards.
*
* XXXX use a more appropriate format for exporting this information
*/
if (e->confirmed_idx < 0) {
status = "never-connected";
} else if (! e->currently_listed) {
when = e->unlisted_since_date;
status = "unusable";
} else if (! e->is_filtered_guard) {
status = "unusable";
} else if (e->is_reachable == GUARD_REACHABLE_NO) {
when = e->failing_since;
status = "down";
} else {
status = "up";
}
node = entry_guard_find_node(e);
if (node) {
node_get_verbose_nickname(node, nbuf);
} else {
nbuf[0] = '$';
base16_encode(nbuf+1, sizeof(nbuf)-1, e->identity, DIGEST_LEN);
/* e->nickname field is not very reliable if we don't know about
* this router any longer; don't include it. */
}
char *result = NULL;
if (when) {
format_iso_time(tbuf, when);
tor_asprintf(&result, "%s %s %s\n", nbuf, status, tbuf);
} else {
tor_asprintf(&result, "%s %s\n", nbuf, status);
}
return result;
}
/** If <b>question</b> is the string "entry-guards", then dump
* to *<b>answer</b> a newly allocated string describing all of
* the nodes in the global entry_guards list. See control-spec.txt
* for details.
* For backward compatibility, we also handle the string "helper-nodes".
*
* XXX this should be totally redesigned after prop 271 too, and that's
* going to take some control spec work.
* */
int
getinfo_helper_entry_guards(control_connection_t *conn,
const char *question, char **answer,
const char **errmsg)
{
guard_selection_t *gs = get_guard_selection_info();
tor_assert(gs != NULL);
(void) conn;
(void) errmsg;
if (!strcmp(question,"entry-guards") ||
!strcmp(question,"helper-nodes")) {
const smartlist_t *guards;
guards = gs->sampled_entry_guards;
smartlist_t *sl = smartlist_new();
SMARTLIST_FOREACH_BEGIN(guards, const entry_guard_t *, e) {
char *cp = getinfo_helper_format_single_entry_guard(e);
smartlist_add(sl, cp);
} SMARTLIST_FOREACH_END(e);
*answer = smartlist_join_strings(sl, "", 0, NULL);
SMARTLIST_FOREACH(sl, char *, c, tor_free(c));
smartlist_free(sl);
}
return 0;
}
/* Given the original bandwidth of a guard and its guardfraction,
* calculate how much bandwidth the guard should have as a guard and
* as a non-guard.
*
* Quoting from proposal236:
*
* Let Wpf denote the weight from the 'bandwidth-weights' line a
* client would apply to N for position p if it had the guard
* flag, Wpn the weight if it did not have the guard flag, and B the
* measured bandwidth of N in the consensus. Then instead of choosing
* N for position p proportionally to Wpf*B or Wpn*B, clients should
* choose N proportionally to F*Wpf*B + (1-F)*Wpn*B.
*
* This function fills the <b>guardfraction_bw</b> structure. It sets
* <b>guard_bw</b> to F*B and <b>non_guard_bw</b> to (1-F)*B.
*/
void
guard_get_guardfraction_bandwidth(guardfraction_bandwidth_t *guardfraction_bw,
int orig_bandwidth,
uint32_t guardfraction_percentage)
{
double guardfraction_fraction;
/* Turn the percentage into a fraction. */
tor_assert(guardfraction_percentage <= 100);
guardfraction_fraction = guardfraction_percentage / 100.0;
long guard_bw = tor_lround(guardfraction_fraction * orig_bandwidth);
tor_assert(guard_bw <= INT_MAX);
guardfraction_bw->guard_bw = (int) guard_bw;
guardfraction_bw->non_guard_bw = orig_bandwidth - (int) guard_bw;
}
/** Helper: Update the status of all entry guards, in whatever algorithm
* is used. Return true if we should stop using all previously generated
* circuits, by calling circuit_mark_all_unused_circs() and
* circuit_mark_all_dirty_circs_as_unusable().
*/
int
guards_update_all(void)
{
int mark_circuits = 0;
if (update_guard_selection_choice(get_options()))
mark_circuits = 1;
tor_assert(curr_guard_context);
if (entry_guards_update_all(curr_guard_context))
mark_circuits = 1;
return mark_circuits;
}
/** Helper: pick a guard for a circuit, with whatever algorithm is
used. */
const node_t *
guards_choose_guard(cpath_build_state_t *state,
uint8_t purpose,
circuit_guard_state_t **guard_state_out)
{
const node_t *r = NULL;
const uint8_t *exit_id = NULL;
entry_guard_restriction_t *rst = NULL;
/* Only apply restrictions if we have a specific exit node in mind, and only
* if we are not doing vanguard circuits: we don't want to apply guard
* restrictions to vanguard circuits. */
if (state && !circuit_should_use_vanguards(purpose) &&
(exit_id = build_state_get_exit_rsa_id(state))) {
/* We're building to a targeted exit node, so that node can't be
* chosen as our guard for this circuit. Remember that fact in a
* restriction. */
rst = guard_create_exit_restriction(exit_id);
tor_assert(rst);
}
if (entry_guard_pick_for_circuit(get_guard_selection_info(),
GUARD_USAGE_TRAFFIC,
rst,
&r,
guard_state_out) < 0) {
tor_assert(r == NULL);
}
return r;
}
/** Remove all currently listed entry guards for a given guard selection
* context. This frees and replaces <b>gs</b>, so don't use <b>gs</b>
* after calling this function. */
void
remove_all_entry_guards_for_guard_selection(guard_selection_t *gs)
{
// This function shouldn't exist. XXXX
tor_assert(gs != NULL);
char *old_name = tor_strdup(gs->name);
guard_selection_type_t old_type = gs->type;
SMARTLIST_FOREACH(gs->sampled_entry_guards, entry_guard_t *, entry, {
control_event_guard(entry->nickname, entry->identity, "DROPPED");
});
if (gs == curr_guard_context) {
curr_guard_context = NULL;
}
smartlist_remove(guard_contexts, gs);
guard_selection_free(gs);
gs = get_guard_selection_by_name(old_name, old_type, 1);
entry_guards_changed_for_guard_selection(gs);
tor_free(old_name);
}
/** Remove all currently listed entry guards, so new ones will be chosen.
*
* XXXX This function shouldn't exist -- it's meant to support the DROPGUARDS
* command, which is deprecated.
*/
void
remove_all_entry_guards(void)
{
remove_all_entry_guards_for_guard_selection(get_guard_selection_info());
}
/** Helper: pick a directory guard, with whatever algorithm is used. */
const node_t *
guards_choose_dirguard(uint8_t dir_purpose,
circuit_guard_state_t **guard_state_out)
{
const node_t *r = NULL;
entry_guard_restriction_t *rst = NULL;
/* If we are fetching microdescs, don't query outdated dirservers. */
if (dir_purpose == DIR_PURPOSE_FETCH_MICRODESC) {
rst = guard_create_dirserver_md_restriction();
}
if (entry_guard_pick_for_circuit(get_guard_selection_info(),
GUARD_USAGE_DIRGUARD,
rst,
&r,
guard_state_out) < 0) {
tor_assert(r == NULL);
}
return r;
}
/**
* If we're running with a constrained guard set, then maybe mark our guards
* usable. Return 1 if we do; 0 if we don't.
*/
int
guards_retry_optimistic(const or_options_t *options)
{
if (! entry_list_is_constrained(options))
return 0;
mark_primary_guards_maybe_reachable(get_guard_selection_info());
return 1;
}
/**
* Check if we are missing any crucial dirinfo for the guard subsystem to
* work. Return NULL if everything went well, otherwise return a newly
* allocated string with an informative error message. In the latter case, use
* the genreal descriptor information <b>using_mds</b>, <b>num_present</b> and
* <b>num_usable</b> to improve the error message. */
char *
guard_selection_get_err_str_if_dir_info_missing(guard_selection_t *gs,
int using_mds,
int num_present, int num_usable)
{
if (!gs->primary_guards_up_to_date)
entry_guards_update_primary(gs);
char *ret_str = NULL;
int n_missing_descriptors = 0;
int n_considered = 0;
int num_primary_to_check;
/* We want to check for the descriptor of at least the first two primary
* guards in our list, since these are the guards that we typically use for
* circuits. */
num_primary_to_check = get_n_primary_guards_to_use(GUARD_USAGE_TRAFFIC);
num_primary_to_check++;
SMARTLIST_FOREACH_BEGIN(gs->primary_entry_guards, entry_guard_t *, guard) {
entry_guard_consider_retry(guard);
if (guard->is_reachable == GUARD_REACHABLE_NO)
continue;
n_considered++;
if (!guard_has_descriptor(guard))
n_missing_descriptors++;
if (n_considered >= num_primary_to_check)
break;
} SMARTLIST_FOREACH_END(guard);
/* If we are not missing any descriptors, return NULL. */
if (!n_missing_descriptors) {
return NULL;
}
/* otherwise return a helpful error string */
tor_asprintf(&ret_str, "We're missing descriptors for %d/%d of our "
"primary entry guards (total %sdescriptors: %d/%d).",
n_missing_descriptors, num_primary_to_check,
using_mds?"micro":"", num_present, num_usable);
return ret_str;
}
/** As guard_selection_have_enough_dir_info_to_build_circuits, but uses
* the default guard selection. */
char *
entry_guards_get_err_str_if_dir_info_missing(int using_mds,
int num_present, int num_usable)
{
return guard_selection_get_err_str_if_dir_info_missing(
get_guard_selection_info(),
using_mds,
num_present, num_usable);
}
/** Free one guard selection context */
STATIC void
guard_selection_free_(guard_selection_t *gs)
{
if (!gs) return;
tor_free(gs->name);
if (gs->sampled_entry_guards) {
SMARTLIST_FOREACH(gs->sampled_entry_guards, entry_guard_t *, e,
entry_guard_free(e));
smartlist_free(gs->sampled_entry_guards);
gs->sampled_entry_guards = NULL;
}
smartlist_free(gs->confirmed_entry_guards);
smartlist_free(gs->primary_entry_guards);
tor_free(gs);
}
/** Release all storage held by the list of entry guards and related
* memory structs. */
void
entry_guards_free_all(void)
{
/* Null out the default */
curr_guard_context = NULL;
/* Free all the guard contexts */
if (guard_contexts != NULL) {
SMARTLIST_FOREACH_BEGIN(guard_contexts, guard_selection_t *, gs) {
guard_selection_free(gs);
} SMARTLIST_FOREACH_END(gs);
smartlist_free(guard_contexts);
guard_contexts = NULL;
}
circuit_build_times_free_timeouts(get_circuit_build_times_mutable());
}
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