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- /* Copyright (c) 2017 The Tor Project, Inc. */
- /* See LICENSE for licensing information */
- /**
- * \file circuitpadding.c
- * \brief Circuit-level padding implementation
- *
- * \details
- *
- * This file implements Tor proposal 254 "Padding Negotiation" which is heavily
- * inspired by the paper "Toward an Efficient Website Fingerprinting Defense"
- * by M. Juarez, M. Imani, M. Perry, C. Diaz, M. Wright.
- *
- * In particular the code in this file describes mechanisms for clients to
- * negotiate various types of circuit-level padding from relays.
- *
- * Each padding type is described by a state machine (circpad_machine_spec_t),
- * which is also referred as a "padding machine" in this file. Currently,
- * these state machines are hardcoded in the source code (e.g. see
- * circpad_machines_init()), but in the future we will be able to
- * serialize them in the torrc or the consensus.
- *
- * As specified by prop#254, clients can negotiate padding with relays by using
- * PADDING_NEGOTIATE cells. After successful padding negotiation, padding
- * machines are assigned to the circuit in their mutable form as a
- * circpad_machine_runtime_t.
- *
- * Each state of a padding state machine can be either:
- * - A histogram that specifies inter-arrival padding delays.
- * - Or a parametrized probability distribution that specifies inter-arrival
- * delays (see circpad_distribution_type_t).
- *
- * Padding machines start from the START state and finish with the END
- * state. They can transition between states using the events in
- * circpad_event_t.
- *
- * When a padding machine reaches the END state, it gets wiped from the circuit
- * so that other padding machines can take over if needed (see
- * circpad_machine_spec_transitioned_to_end()).
- *
- ****************************
- * General notes:
- *
- * All used machines should be heap allocated and placed into
- * origin_padding_machines/relay_padding_machines so that they get correctly
- * cleaned up by the circpad_free_all() function.
- **/
- #define CIRCUITPADDING_PRIVATE
- #include <math.h>
- #include "lib/math/fp.h"
- #include "lib/math/prob_distr.h"
- #include "core/or/or.h"
- #include "core/or/circuitpadding.h"
- #include "core/or/circuitpadding_machines.h"
- #include "core/or/circuitlist.h"
- #include "core/or/circuituse.h"
- #include "core/mainloop/netstatus.h"
- #include "core/or/relay.h"
- #include "feature/stats/rephist.h"
- #include "feature/nodelist/networkstatus.h"
- #include "core/or/channel.h"
- #include "lib/time/compat_time.h"
- #include "lib/defs/time.h"
- #include "lib/crypt_ops/crypto_rand.h"
- #include "core/or/crypt_path_st.h"
- #include "core/or/circuit_st.h"
- #include "core/or/origin_circuit_st.h"
- #include "core/or/or_circuit_st.h"
- #include "feature/nodelist/routerstatus_st.h"
- #include "feature/nodelist/node_st.h"
- #include "core/or/cell_st.h"
- #include "core/or/extend_info_st.h"
- #include "core/crypto/relay_crypto.h"
- #include "feature/nodelist/nodelist.h"
- #include "app/config/config.h"
- static inline circpad_circuit_state_t circpad_circuit_state(
- origin_circuit_t *circ);
- static void circpad_setup_machine_on_circ(circuit_t *on_circ,
- const circpad_machine_spec_t *machine);
- static double circpad_distribution_sample(circpad_distribution_t dist);
- static inline void circpad_machine_update_state_length_for_nonpadding(
- circpad_machine_runtime_t *mi);
- /** Cached consensus params */
- static uint8_t circpad_padding_disabled;
- static uint8_t circpad_padding_reduced;
- static uint8_t circpad_global_max_padding_percent;
- static uint16_t circpad_global_allowed_cells;
- static uint16_t circpad_max_circ_queued_cells;
- /** Global cell counts, for rate limiting */
- static uint64_t circpad_global_padding_sent;
- static uint64_t circpad_global_nonpadding_sent;
- /** This is the list of circpad_machine_spec_t's parsed from consensus and
- * torrc that have origin_side == 1 (ie: are for client side).
- *
- * The machines in this smartlist are considered immutable and they are used
- * as-is by circuits so they should not change or get deallocated in Tor's
- * runtime and as long as circuits are alive. */
- STATIC smartlist_t *origin_padding_machines = NULL;
- /** This is the list of circpad_machine_spec_t's parsed from consensus and
- * torrc that have origin_side == 0 (ie: are for relay side).
- *
- * The machines in this smartlist are considered immutable and they are used
- * as-is by circuits so they should not change or get deallocated in Tor's
- * runtime and as long as circuits are alive. */
- STATIC smartlist_t *relay_padding_machines = NULL;
- /** Loop over the current padding state machines using <b>loop_var</b> as the
- * loop variable. */
- #define FOR_EACH_CIRCUIT_MACHINE_BEGIN(loop_var) \
- STMT_BEGIN \
- for (int loop_var = 0; loop_var < CIRCPAD_MAX_MACHINES; loop_var++) {
- #define FOR_EACH_CIRCUIT_MACHINE_END } STMT_END ;
- /** Loop over the current active padding state machines using <b>loop_var</b>
- * as the loop variable. If a machine is not active, skip it. */
- #define FOR_EACH_ACTIVE_CIRCUIT_MACHINE_BEGIN(loop_var, circ) \
- FOR_EACH_CIRCUIT_MACHINE_BEGIN(loop_var) \
- if (!(circ)->padding_info[loop_var]) \
- continue;
- #define FOR_EACH_ACTIVE_CIRCUIT_MACHINE_END } STMT_END ;
- /**
- * Free the machineinfo at an index
- */
- static void
- circpad_circuit_machineinfo_free_idx(circuit_t *circ, int idx)
- {
- if (circ->padding_info[idx]) {
- log_fn(LOG_INFO,LD_CIRC, "Freeing padding info idx %d on circuit %u (%d)",
- idx, CIRCUIT_IS_ORIGIN(circ) ?
- TO_ORIGIN_CIRCUIT(circ)->global_identifier : 0,
- circ->purpose);
- tor_free(circ->padding_info[idx]->histogram);
- timer_free(circ->padding_info[idx]->padding_timer);
- tor_free(circ->padding_info[idx]);
- }
- }
- /**
- * Return true if circpad has decided to hold the circuit open for additional
- * padding. This function is used to take and retain ownership of certain
- * types of circuits that have padding machines on them, that have been passed
- * to circuit_mark_for_close().
- *
- * circuit_mark_for_close() calls this function to ask circpad if any padding
- * machines want to keep the circuit open longer to pad.
- *
- * Any non-measurement circuit that was closed for a normal, non-error reason
- * code may be held open for up to CIRCPAD_DELAY_INFINITE microseconds between
- * network-driven cell events.
- *
- * After CIRCPAD_DELAY_INFINITE microseconds of silence on a circuit, this
- * function will no longer hold it open (it will return 0 regardless of
- * what the machines ask for, and thus circuit_expire_old_circuits_clientside()
- * will close the circuit after roughly 1.25hr of idle time, maximum,
- * regardless of the padding machine state.
- */
- int
- circpad_marked_circuit_for_padding(circuit_t *circ, int reason)
- {
- /* If the circuit purpose is measurement or path bias, don't
- * hold it open */
- if (circ->purpose == CIRCUIT_PURPOSE_PATH_BIAS_TESTING ||
- circ->purpose == CIRCUIT_PURPOSE_C_MEASURE_TIMEOUT) {
- return 0;
- }
- /* If the circuit is closed for any reason other than these three valid,
- * client-side close reasons, do not try to keep it open. It is probably
- * damaged or unusable. Note this is OK with vanguards because
- * controller-closed circuits have REASON=REQUESTED, so vanguards-closed
- * circuits will not be held open (we want them to close ASAP). */
- if (!(reason == END_CIRC_REASON_NONE ||
- reason == END_CIRC_REASON_FINISHED ||
- reason == END_CIRC_REASON_IP_NOW_REDUNDANT)) {
- return 0;
- }
- FOR_EACH_ACTIVE_CIRCUIT_MACHINE_BEGIN(i, circ) {
- circpad_machine_runtime_t *mi = circ->padding_info[i];
- if (!mi) {
- continue; // No padding runtime info; check next machine
- }
- const circpad_state_t *state = circpad_machine_current_state(mi);
- /* If we're in END state (NULL here), then check next machine */
- if (!state) {
- continue; // check next machine
- }
- /* If the machine does not want to control the circuit close itself, then
- * check the next machine */
- if (!circ->padding_machine[i]->manage_circ_lifetime) {
- continue; // check next machine
- }
- /* If the machine has reached the END state, we can close. Check next
- * machine. */
- if (mi->current_state == CIRCPAD_STATE_END) {
- continue; // check next machine
- }
- log_info(LD_CIRC, "Circuit %d is not marked for close because of a "
- "pending padding machine in index %d.",
- CIRCUIT_IS_ORIGIN(circ) ?
- TO_ORIGIN_CIRCUIT(circ)->global_identifier : 0, i);
- /* If the machine has had no network events at all within the
- * last circpad_delay_t timespan, it's in some deadlock state.
- * Tell circuit_mark_for_close() that we don't own it anymore.
- * This will allow circuit_expire_old_circuits_clientside() to
- * close it.
- */
- if (circ->padding_info[i]->last_cell_time_sec +
- (time_t)CIRCPAD_DELAY_MAX_SECS < approx_time()) {
- log_notice(LD_BUG, "Circuit %d was not marked for close because of a "
- "pending padding machine in index %d for over an hour. "
- "Circuit is a %s",
- CIRCUIT_IS_ORIGIN(circ) ?
- TO_ORIGIN_CIRCUIT(circ)->global_identifier : 0,
- i, circuit_purpose_to_string(circ->purpose));
- return 0; // abort timer reached; mark the circuit for close now
- }
- /* If we weren't marked dirty yet, let's pretend we're dirty now.
- * ("Dirty" means that a circuit has been used for application traffic
- * by Tor.. Dirty circuits have different expiry times, and are not
- * considered in counts of built circuits, etc. By claiming that we're
- * dirty, the rest of Tor will make decisions as if we were actually
- * used by application data.
- *
- * This is most important for circuit_expire_old_circuits_clientside(),
- * where we want that function to expire us after the padding machine
- * has shut down, but using the MaxCircuitDirtiness timer instead of
- * the idle circuit timer (again, we want this because we're not
- * supposed to look idle to Guard nodes that can see our lifespan). */
- if (!circ->timestamp_dirty)
- circ->timestamp_dirty = approx_time();
- /* Take ownership of the circuit */
- circuit_change_purpose(circ, CIRCUIT_PURPOSE_C_CIRCUIT_PADDING);
- return 1;
- } FOR_EACH_ACTIVE_CIRCUIT_MACHINE_END;
- return 0; // No machine wanted to keep the circuit open; mark for close
- }
- /**
- * Free all the machineinfos in <b>circ</b> that match <b>machine_num</b>.
- *
- * Returns true if any machineinfos with that number were freed.
- * False otherwise. */
- static int
- free_circ_machineinfos_with_machine_num(circuit_t *circ, int machine_num)
- {
- int found = 0;
- FOR_EACH_CIRCUIT_MACHINE_BEGIN(i) {
- if (circ->padding_machine[i] &&
- circ->padding_machine[i]->machine_num == machine_num) {
- circpad_circuit_machineinfo_free_idx(circ, i);
- circ->padding_machine[i] = NULL;
- found = 1;
- }
- } FOR_EACH_CIRCUIT_MACHINE_END;
- return found;
- }
- /**
- * Free all padding machines and mutable info associated with circuit
- */
- void
- circpad_circuit_free_all_machineinfos(circuit_t *circ)
- {
- FOR_EACH_CIRCUIT_MACHINE_BEGIN(i) {
- circpad_circuit_machineinfo_free_idx(circ, i);
- } FOR_EACH_CIRCUIT_MACHINE_END;
- }
- /**
- * Allocate a new mutable machineinfo structure.
- */
- STATIC circpad_machine_runtime_t *
- circpad_circuit_machineinfo_new(circuit_t *on_circ, int machine_index)
- {
- circpad_machine_runtime_t *mi =
- tor_malloc_zero(sizeof(circpad_machine_runtime_t));
- mi->machine_index = machine_index;
- mi->on_circ = on_circ;
- mi->last_cell_time_sec = approx_time();
- return mi;
- }
- /**
- * Return the circpad_state_t for the current state based on the
- * mutable info.
- *
- * This function returns NULL when the machine is in the end state or in an
- * invalid state.
- */
- STATIC const circpad_state_t *
- circpad_machine_current_state(const circpad_machine_runtime_t *mi)
- {
- const circpad_machine_spec_t *machine = CIRCPAD_GET_MACHINE(mi);
- if (mi->current_state == CIRCPAD_STATE_END) {
- return NULL;
- } else if (BUG(mi->current_state >= machine->num_states)) {
- log_fn(LOG_WARN,LD_CIRC,
- "Invalid circuit padding state %d",
- mi->current_state);
- return NULL;
- }
- return &machine->states[mi->current_state];
- }
- /**
- * Get the lower bound of a histogram bin.
- *
- * You can obtain the upper bound using histogram_get_bin_upper_bound().
- *
- * This function can also be called with 'bin' set to a value equal or greater
- * than histogram_len in which case the infinity bin is chosen and
- * CIRCPAD_DELAY_INFINITE is returned.
- */
- STATIC circpad_delay_t
- circpad_histogram_bin_to_usec(const circpad_machine_runtime_t *mi,
- circpad_hist_index_t bin)
- {
- const circpad_state_t *state = circpad_machine_current_state(mi);
- circpad_delay_t rtt_add_usec = 0;
- /* Our state should have been checked to be non-null by the caller
- * (circpad_machine_remove_token()) */
- if (BUG(state == NULL)) {
- return CIRCPAD_DELAY_INFINITE;
- }
- /* The infinity bin has an upper bound of infinity, so make sure we return
- * that if they ask for it. */
- if (bin > CIRCPAD_INFINITY_BIN(state)) {
- return CIRCPAD_DELAY_INFINITE;
- }
- /* If we are using an RTT estimate, consider it as well. */
- if (state->use_rtt_estimate) {
- rtt_add_usec = mi->rtt_estimate_usec;
- }
- return state->histogram_edges[bin] + rtt_add_usec;
- }
- /**
- * Like circpad_histogram_bin_to_usec() but return the upper bound of bin.
- * (The upper bound is included in the bin.)
- */
- STATIC circpad_delay_t
- histogram_get_bin_upper_bound(const circpad_machine_runtime_t *mi,
- circpad_hist_index_t bin)
- {
- return circpad_histogram_bin_to_usec(mi, bin+1) - 1;
- }
- /** Return the midpoint of the histogram bin <b>bin_index</b>. */
- static circpad_delay_t
- circpad_get_histogram_bin_midpoint(const circpad_machine_runtime_t *mi,
- int bin_index)
- {
- circpad_delay_t left_bound = circpad_histogram_bin_to_usec(mi, bin_index);
- circpad_delay_t right_bound = histogram_get_bin_upper_bound(mi, bin_index);
- return left_bound + (right_bound - left_bound)/2;
- }
- /**
- * Return the bin that contains the usec argument.
- * "Contains" is defined as us in [lower, upper).
- *
- * This function will never return the infinity bin (histogram_len-1), in order
- * to simplify the rest of the code, so if a usec is provided that falls above
- * the highest non-infinity bin, that bin index will be returned.
- */
- STATIC circpad_hist_index_t
- circpad_histogram_usec_to_bin(const circpad_machine_runtime_t *mi,
- circpad_delay_t usec)
- {
- const circpad_state_t *state = circpad_machine_current_state(mi);
- circpad_delay_t rtt_add_usec = 0;
- circpad_hist_index_t bin;
- /* Our state should have been checked to be non-null by the caller
- * (circpad_machine_remove_token()) */
- if (BUG(state == NULL)) {
- return 0;
- }
- /* If we are using an RTT estimate, consider it as well. */
- if (state->use_rtt_estimate) {
- rtt_add_usec = mi->rtt_estimate_usec;
- }
- /* Walk through the bins and check the upper bound of each bin, if 'usec' is
- * less-or-equal to that, return that bin. If rtt_estimate is enabled then
- * add that to the upper bound of each bin.
- *
- * We don't want to return the infinity bin here, so don't go there. */
- for (bin = 0 ; bin < CIRCPAD_INFINITY_BIN(state) ; bin++) {
- if (usec <= histogram_get_bin_upper_bound(mi, bin) + rtt_add_usec) {
- return bin;
- }
- }
- /* We don't want to return the infinity bin here, so if we still didn't find
- * the right bin, return the highest non-infinity bin */
- return CIRCPAD_INFINITY_BIN(state)-1;
- }
- /**
- * Return true if the machine supports token removal.
- *
- * Token removal is equivalent to having a mutable histogram in the
- * circpad_machine_runtime_t mutable info. So while we're at it,
- * let's assert that everything is consistent between the mutable
- * runtime and the readonly machine spec.
- */
- static inline int
- circpad_is_token_removal_supported(circpad_machine_runtime_t *mi)
- {
- /* No runtime histogram == no token removal */
- if (mi->histogram == NULL) {
- /* Machines that don't want token removal are trying to avoid
- * potentially expensive mallocs, extra memory accesses, and/or
- * potentially expensive monotime calls. Let's minimize checks
- * and keep this path fast. */
- tor_assert_nonfatal(mi->histogram_len == 0);
- return 0;
- } else {
- /* Machines that do want token removal are less sensitive to performance.
- * Let's spend some time to check that our state is consistent and sane */
- const circpad_state_t *state = circpad_machine_current_state(mi);
- if (BUG(!state)) {
- return 1;
- }
- tor_assert_nonfatal(state->token_removal != CIRCPAD_TOKEN_REMOVAL_NONE);
- tor_assert_nonfatal(state->histogram_len == mi->histogram_len);
- tor_assert_nonfatal(mi->histogram_len != 0);
- return 1;
- }
- tor_assert_nonfatal_unreached();
- return 0;
- }
- /**
- * This function frees any token bins allocated from a previous state
- *
- * Called after a state transition, or if the bins are empty.
- */
- STATIC void
- circpad_machine_setup_tokens(circpad_machine_runtime_t *mi)
- {
- const circpad_state_t *state = circpad_machine_current_state(mi);
- /* If this state doesn't exist, or doesn't have token removal,
- * free any previous state's runtime histogram, and bail.
- *
- * If we don't have a token removal strategy, we also don't need a runtime
- * histogram and we rely on the immutable one in machine_spec_t. */
- if (!state || state->token_removal == CIRCPAD_TOKEN_REMOVAL_NONE) {
- if (mi->histogram) {
- tor_free(mi->histogram);
- mi->histogram = NULL;
- mi->histogram_len = 0;
- }
- return;
- }
- /* Try to avoid re-mallocing if we don't really need to */
- if (!mi->histogram || (mi->histogram
- && mi->histogram_len != state->histogram_len)) {
- tor_free(mi->histogram); // null ok
- mi->histogram = tor_malloc_zero(sizeof(circpad_hist_token_t)
- *state->histogram_len);
- }
- mi->histogram_len = state->histogram_len;
- memcpy(mi->histogram, state->histogram,
- sizeof(circpad_hist_token_t)*state->histogram_len);
- }
- /**
- * Choose a length for this state (in cells), if specified.
- */
- static void
- circpad_choose_state_length(circpad_machine_runtime_t *mi)
- {
- const circpad_state_t *state = circpad_machine_current_state(mi);
- double length;
- if (!state || state->length_dist.type == CIRCPAD_DIST_NONE) {
- mi->state_length = CIRCPAD_STATE_LENGTH_INFINITE;
- return;
- }
- length = circpad_distribution_sample(state->length_dist);
- length = MAX(0, length);
- length += state->start_length;
- if (state->max_length) {
- length = MIN(length, state->max_length);
- }
- mi->state_length = clamp_double_to_int64(length);
- log_info(LD_CIRC, "State length sampled to %"PRIu64" for circuit %u",
- mi->state_length, CIRCUIT_IS_ORIGIN(mi->on_circ) ?
- TO_ORIGIN_CIRCUIT(mi->on_circ)->global_identifier : 0);
- }
- /**
- * Sample a value from our iat_dist, and clamp it safely
- * to circpad_delay_t.
- *
- * Before returning, add <b>delay_shift</b> (can be zero) to the sampled value.
- */
- static circpad_delay_t
- circpad_distribution_sample_iat_delay(const circpad_state_t *state,
- circpad_delay_t delay_shift)
- {
- double val = circpad_distribution_sample(state->iat_dist);
- /* These comparisons are safe, because the output is in the range
- * [0, 2**32), and double has a precision of 53 bits. */
- /* We want a positive sample value */
- val = MAX(0, val);
- /* Respect the maximum sample setting */
- val = MIN(val, state->dist_max_sample_usec);
- /* Now apply the shift:
- * This addition is exact: val is at most 2**32-1, delay_shift is at most
- * 2**32-1, and doubles have a precision of 53 bits. */
- val += delay_shift;
- /* Clamp the distribution at infinite delay val */
- return (circpad_delay_t)MIN(tor_llround(val), CIRCPAD_DELAY_INFINITE);
- }
- /**
- * Sample an expected time-until-next-packet delay from the histogram or
- * probability distribution.
- *
- * A bin of the histogram is chosen with probability proportional to the number
- * of tokens in each bin, and then a time value is chosen uniformly from that
- * bin's [start,end) time range.
- */
- STATIC circpad_delay_t
- circpad_machine_sample_delay(circpad_machine_runtime_t *mi)
- {
- const circpad_state_t *state = circpad_machine_current_state(mi);
- const circpad_hist_token_t *histogram = NULL;
- circpad_hist_index_t curr_bin = 0;
- circpad_delay_t bin_start, bin_end;
- /* These three must all be larger than circpad_hist_token_t, because
- * we sum several circpad_hist_token_t values across the histogram */
- uint64_t curr_weight = 0;
- uint64_t histogram_total_tokens = 0;
- uint64_t bin_choice;
- tor_assert(state);
- if (state->iat_dist.type != CIRCPAD_DIST_NONE) {
- /* Sample from a fixed IAT distribution and return */
- circpad_delay_t iat_delay_shift = state->use_rtt_estimate ?
- mi->rtt_estimate_usec + state->dist_added_shift_usec :
- state->dist_added_shift_usec;
- return circpad_distribution_sample_iat_delay(state, iat_delay_shift);
- } else if (circpad_is_token_removal_supported(mi)) {
- histogram = mi->histogram;
- for (circpad_hist_index_t b = 0; b < state->histogram_len; b++)
- histogram_total_tokens += histogram[b];
- } else {
- /* We have a histogram, but it's immutable */
- histogram = state->histogram;
- histogram_total_tokens = state->histogram_total_tokens;
- }
- /* If we are out of tokens, don't schedule padding. */
- if (!histogram_total_tokens) {
- return CIRCPAD_DELAY_INFINITE;
- }
- bin_choice = crypto_fast_rng_get_uint64(get_thread_fast_rng(),
- histogram_total_tokens);
- /* Skip all the initial zero bins */
- while (!histogram[curr_bin]) {
- curr_bin++;
- }
- curr_weight = histogram[curr_bin];
- // TODO: This is not constant-time. Pretty sure we don't
- // really need it to be, though.
- while (curr_weight < bin_choice) {
- curr_bin++;
- /* It should be impossible to run past the end of the histogram */
- if (BUG(curr_bin >= state->histogram_len)) {
- return CIRCPAD_DELAY_INFINITE;
- }
- curr_weight += histogram[curr_bin];
- }
- /* Do some basic checking of the current bin we are in */
- if (BUG(curr_bin >= state->histogram_len) ||
- BUG(histogram[curr_bin] == 0)) {
- return CIRCPAD_DELAY_INFINITE;
- }
- // Store this index to remove the token upon callback.
- if (state->token_removal != CIRCPAD_TOKEN_REMOVAL_NONE) {
- mi->chosen_bin = curr_bin;
- }
- if (curr_bin >= CIRCPAD_INFINITY_BIN(state)) {
- if (state->token_removal != CIRCPAD_TOKEN_REMOVAL_NONE &&
- mi->histogram[curr_bin] > 0) {
- mi->histogram[curr_bin]--;
- }
- // Infinity: Don't send a padding packet. Wait for a real packet
- // and then see if our bins are empty or what else we should do.
- return CIRCPAD_DELAY_INFINITE;
- }
- tor_assert(curr_bin < CIRCPAD_INFINITY_BIN(state));
- bin_start = circpad_histogram_bin_to_usec(mi, curr_bin);
- /* We don't need to reduct 1 from the upper bound because the random range
- * function below samples from [bin_start, bin_end) */
- bin_end = circpad_histogram_bin_to_usec(mi, curr_bin+1);
- /* Bin edges are monotonically increasing so this is a bug. Handle it. */
- if (BUG(bin_start >= bin_end)) {
- return bin_start;
- }
- return (circpad_delay_t)crypto_fast_rng_uint64_range(get_thread_fast_rng(),
- bin_start, bin_end);
- }
- /**
- * Sample a value from the specified probability distribution.
- *
- * Uses functions from src/lib/math/prob_distr.c .
- */
- static double
- circpad_distribution_sample(circpad_distribution_t dist)
- {
- log_fn(LOG_DEBUG,LD_CIRC, "Sampling delay with distribution %d",
- dist.type);
- switch (dist.type) {
- case CIRCPAD_DIST_NONE:
- {
- /* We should not get in here like this */
- tor_assert_nonfatal_unreached();
- return 0;
- }
- case CIRCPAD_DIST_UNIFORM:
- {
- // param2 is upper bound, param1 is lower
- const struct uniform my_uniform = {
- .base = UNIFORM(my_uniform),
- .a = dist.param1,
- .b = dist.param2,
- };
- return dist_sample(&my_uniform.base);
- }
- case CIRCPAD_DIST_LOGISTIC:
- {
- /* param1 is Mu, param2 is sigma. */
- const struct logistic my_logistic = {
- .base = LOGISTIC(my_logistic),
- .mu = dist.param1,
- .sigma = dist.param2,
- };
- return dist_sample(&my_logistic.base);
- }
- case CIRCPAD_DIST_LOG_LOGISTIC:
- {
- /* param1 is Alpha, param2 is 1.0/Beta */
- const struct log_logistic my_log_logistic = {
- .base = LOG_LOGISTIC(my_log_logistic),
- .alpha = dist.param1,
- .beta = dist.param2,
- };
- return dist_sample(&my_log_logistic.base);
- }
- case CIRCPAD_DIST_GEOMETRIC:
- {
- /* param1 is 'p' (success probability) */
- const struct geometric my_geometric = {
- .base = GEOMETRIC(my_geometric),
- .p = dist.param1,
- };
- return dist_sample(&my_geometric.base);
- }
- case CIRCPAD_DIST_WEIBULL:
- {
- /* param1 is k, param2 is Lambda */
- const struct weibull my_weibull = {
- .base = WEIBULL(my_weibull),
- .k = dist.param1,
- .lambda = dist.param2,
- };
- return dist_sample(&my_weibull.base);
- }
- case CIRCPAD_DIST_PARETO:
- {
- /* param1 is sigma, param2 is xi, no more params for mu so we use 0 */
- const struct genpareto my_genpareto = {
- .base = GENPARETO(my_genpareto),
- .mu = 0,
- .sigma = dist.param1,
- .xi = dist.param2,
- };
- return dist_sample(&my_genpareto.base);
- }
- }
- tor_assert_nonfatal_unreached();
- return 0;
- }
- /**
- * Find the index of the first bin whose upper bound is
- * greater than the target, and that has tokens remaining.
- *
- * Used for histograms with token removal.
- */
- static circpad_hist_index_t
- circpad_machine_first_higher_index(const circpad_machine_runtime_t *mi,
- circpad_delay_t target_bin_usec)
- {
- circpad_hist_index_t bin = circpad_histogram_usec_to_bin(mi,
- target_bin_usec);
- /* Don't remove from the infinity bin */
- for (; bin < CIRCPAD_INFINITY_BIN(mi); bin++) {
- if (mi->histogram[bin] &&
- histogram_get_bin_upper_bound(mi, bin) >= target_bin_usec) {
- return bin;
- }
- }
- return mi->histogram_len;
- }
- /**
- * Find the index of the first bin whose lower bound is lower or equal to
- * <b>target_bin_usec</b>, and that still has tokens remaining.
- *
- * Used for histograms with token removal.
- */
- static circpad_hist_index_t
- circpad_machine_first_lower_index(const circpad_machine_runtime_t *mi,
- circpad_delay_t target_bin_usec)
- {
- circpad_hist_index_t bin = circpad_histogram_usec_to_bin(mi,
- target_bin_usec);
- for (; bin >= 0; bin--) {
- if (mi->histogram[bin] &&
- circpad_histogram_bin_to_usec(mi, bin) <= target_bin_usec) {
- return bin;
- }
- }
- return -1;
- }
- /**
- * Remove a token from the first non-empty bin whose upper bound is
- * greater than the target.
- *
- * Used for histograms with token removal.
- */
- STATIC void
- circpad_machine_remove_higher_token(circpad_machine_runtime_t *mi,
- circpad_delay_t target_bin_usec)
- {
- /* We need to remove the token from the first bin
- * whose upper bound is greater than the target, and that
- * has tokens remaining. */
- circpad_hist_index_t bin = circpad_machine_first_higher_index(mi,
- target_bin_usec);
- if (bin >= 0 && bin < CIRCPAD_INFINITY_BIN(mi)) {
- if (!BUG(mi->histogram[bin] == 0)) {
- mi->histogram[bin]--;
- }
- }
- }
- /**
- * Remove a token from the first non-empty bin whose upper bound is
- * lower than the target.
- *
- * Used for histograms with token removal.
- */
- STATIC void
- circpad_machine_remove_lower_token(circpad_machine_runtime_t *mi,
- circpad_delay_t target_bin_usec)
- {
- circpad_hist_index_t bin = circpad_machine_first_lower_index(mi,
- target_bin_usec);
- if (bin >= 0 && bin < CIRCPAD_INFINITY_BIN(mi)) {
- if (!BUG(mi->histogram[bin] == 0)) {
- mi->histogram[bin]--;
- }
- }
- }
- /* Helper macro: Ensure that the bin has tokens available, and BUG out of the
- * function if it's not the case. */
- #define ENSURE_BIN_CAPACITY(bin_index) \
- if (BUG(mi->histogram[bin_index] == 0)) { \
- return; \
- }
- /**
- * Remove a token from the closest non-empty bin to the target.
- *
- * If use_usec is true, measure "closest" in terms of the next closest bin
- * midpoint.
- *
- * If it is false, use bin index distance only.
- *
- * Used for histograms with token removal.
- */
- STATIC void
- circpad_machine_remove_closest_token(circpad_machine_runtime_t *mi,
- circpad_delay_t target_bin_usec,
- bool use_usec)
- {
- circpad_hist_index_t lower, higher, current;
- circpad_hist_index_t bin_to_remove = -1;
- lower = circpad_machine_first_lower_index(mi, target_bin_usec);
- higher = circpad_machine_first_higher_index(mi, target_bin_usec);
- current = circpad_histogram_usec_to_bin(mi, target_bin_usec);
- /* Sanity check the results */
- if (BUG(lower > current) || BUG(higher < current)) {
- return;
- }
- /* Take care of edge cases first */
- if (higher == mi->histogram_len && lower == -1) {
- /* All bins are empty */
- return;
- } else if (higher == mi->histogram_len) {
- /* All higher bins are empty */
- ENSURE_BIN_CAPACITY(lower);
- mi->histogram[lower]--;
- return;
- } else if (lower == -1) {
- /* All lower bins are empty */
- ENSURE_BIN_CAPACITY(higher);
- mi->histogram[higher]--;
- return;
- }
- /* Now handle the intermediate cases */
- if (use_usec) {
- /* Find the closest bin midpoint to the target */
- circpad_delay_t lower_usec = circpad_get_histogram_bin_midpoint(mi, lower);
- circpad_delay_t higher_usec =
- circpad_get_histogram_bin_midpoint(mi, higher);
- if (target_bin_usec < lower_usec) {
- // Lower bin is closer
- ENSURE_BIN_CAPACITY(lower);
- bin_to_remove = lower;
- } else if (target_bin_usec > higher_usec) {
- // Higher bin is closer
- ENSURE_BIN_CAPACITY(higher);
- bin_to_remove = higher;
- } else if (target_bin_usec-lower_usec > higher_usec-target_bin_usec) {
- // Higher bin is closer
- ENSURE_BIN_CAPACITY(higher);
- bin_to_remove = higher;
- } else {
- // Lower bin is closer
- ENSURE_BIN_CAPACITY(lower);
- bin_to_remove = lower;
- }
- mi->histogram[bin_to_remove]--;
- log_debug(LD_CIRC, "Removing token from bin %d", bin_to_remove);
- return;
- } else {
- if (current - lower > higher - current) {
- // Higher bin is closer
- ENSURE_BIN_CAPACITY(higher);
- mi->histogram[higher]--;
- return;
- } else {
- // Lower bin is closer
- ENSURE_BIN_CAPACITY(lower);
- mi->histogram[lower]--;
- return;
- }
- }
- }
- #undef ENSURE_BIN_CAPACITY
- /**
- * Remove a token from the exact bin corresponding to the target.
- *
- * If it is empty, do nothing.
- *
- * Used for histograms with token removal.
- */
- static void
- circpad_machine_remove_exact(circpad_machine_runtime_t *mi,
- circpad_delay_t target_bin_usec)
- {
- circpad_hist_index_t bin = circpad_histogram_usec_to_bin(mi,
- target_bin_usec);
- if (mi->histogram[bin] > 0)
- mi->histogram[bin]--;
- }
- /**
- * Check our state's cell limit count and tokens.
- *
- * Returns 1 if either limits are hit and we decide to change states,
- * otherwise returns 0.
- */
- static circpad_decision_t
- check_machine_token_supply(circpad_machine_runtime_t *mi)
- {
- uint32_t histogram_total_tokens = 0;
- /* Check if bins empty. This requires summing up the current mutable
- * machineinfo histogram token total and checking if it is zero.
- * Machineinfo does not keep a running token count. We're assuming the
- * extra space is not worth this short loop iteration.
- *
- * We also do not count infinity bin in histogram totals.
- */
- if (circpad_is_token_removal_supported(mi)) {
- for (circpad_hist_index_t b = 0; b < CIRCPAD_INFINITY_BIN(mi); b++)
- histogram_total_tokens += mi->histogram[b];
- /* If we change state, we're done */
- if (histogram_total_tokens == 0) {
- if (circpad_internal_event_bins_empty(mi) == CIRCPAD_STATE_CHANGED)
- return CIRCPAD_STATE_CHANGED;
- }
- }
- if (mi->state_length == 0) {
- return circpad_internal_event_state_length_up(mi);
- }
- return CIRCPAD_STATE_UNCHANGED;
- }
- /**
- * Count that a padding packet was sent.
- *
- * This updates our state length count, our machine rate limit counts,
- * and if token removal is used, decrements the histogram.
- */
- static inline void
- circpad_machine_count_padding_sent(circpad_machine_runtime_t *mi)
- {
- /* If we have a valid state length bound, consider it */
- if (mi->state_length != CIRCPAD_STATE_LENGTH_INFINITE &&
- !BUG(mi->state_length <= 0)) {
- mi->state_length--;
- }
- /*
- * Update non-padding counts for rate limiting: We scale at UINT16_MAX
- * because we only use this for a percentile limit of 2 sig figs, and
- * space is scare in the machineinfo struct.
- */
- mi->padding_sent++;
- if (mi->padding_sent == UINT16_MAX) {
- mi->padding_sent /= 2;
- mi->nonpadding_sent /= 2;
- }
- circpad_global_padding_sent++;
- /* If we have a mutable histogram, reduce the token count from
- * the chosen padding bin (this assumes we always send padding
- * when we intended to). */
- if (circpad_is_token_removal_supported(mi)) {
- /* Check array bounds and token count before removing */
- if (!BUG(mi->chosen_bin >= mi->histogram_len) &&
- !BUG(mi->histogram[mi->chosen_bin] == 0)) {
- mi->histogram[mi->chosen_bin]--;
- }
- }
- }
- /**
- * Count a nonpadding packet as being sent.
- *
- * This function updates our overhead accounting variables, as well
- * as decrements the state limit packet counter, if the latter was
- * flagged as applying to non-padding as well.
- */
- static inline void
- circpad_machine_count_nonpadding_sent(circpad_machine_runtime_t *mi)
- {
- /* Update non-padding counts for rate limiting: We scale at UINT16_MAX
- * because we only use this for a percentile limit of 2 sig figs, and
- * space is scare in the machineinfo struct. */
- mi->nonpadding_sent++;
- if (mi->nonpadding_sent == UINT16_MAX) {
- mi->padding_sent /= 2;
- mi->nonpadding_sent /= 2;
- }
- /* Update any state packet length limits that apply */
- circpad_machine_update_state_length_for_nonpadding(mi);
- /* Remove a token from the histogram, if applicable */
- circpad_machine_remove_token(mi);
- }
- /**
- * Decrement the state length counter for a non-padding packet.
- *
- * Only updates the state length if we're using that feature, we
- * have a state, and the machine wants to count non-padding packets
- * towards the state length.
- */
- static inline void
- circpad_machine_update_state_length_for_nonpadding(
- circpad_machine_runtime_t *mi)
- {
- const circpad_state_t *state = NULL;
- if (mi->state_length == CIRCPAD_STATE_LENGTH_INFINITE)
- return;
- state = circpad_machine_current_state(mi);
- /* If we are not in a padding state (like start or end), we're done */
- if (!state)
- return;
- /* If we're enforcing a state length on non-padding packets,
- * decrement it */
- if (state->length_includes_nonpadding &&
- mi->state_length > 0) {
- mi->state_length--;
- }
- }
- /**
- * When a non-padding packet arrives, remove a token from the bin
- * corresponding to the delta since last sent packet. If that bin
- * is empty, choose a token based on the specified removal strategy
- * in the state machine.
- */
- STATIC void
- circpad_machine_remove_token(circpad_machine_runtime_t *mi)
- {
- const circpad_state_t *state = NULL;
- circpad_time_t current_time;
- circpad_delay_t target_bin_usec;
- /* Dont remove any tokens if there was no padding scheduled */
- if (!mi->padding_scheduled_at_usec) {
- return;
- }
- state = circpad_machine_current_state(mi);
- /* If we are not in a padding state (like start or end), we're done */
- if (!state)
- return;
- /* Don't remove any tokens if we're not doing token removal */
- if (state->token_removal == CIRCPAD_TOKEN_REMOVAL_NONE)
- return;
- current_time = monotime_absolute_usec();
- /* If we have scheduled padding some time in the future, we want to see what
- bin we are in at the current time */
- target_bin_usec = (circpad_delay_t)
- MIN((current_time - mi->padding_scheduled_at_usec),
- CIRCPAD_DELAY_INFINITE-1);
- /* We are treating this non-padding cell as a padding cell, so we cancel
- padding timer, if present. */
- mi->padding_scheduled_at_usec = 0;
- if (mi->is_padding_timer_scheduled) {
- mi->is_padding_timer_scheduled = 0;
- timer_disable(mi->padding_timer);
- }
- /* Perform the specified token removal strategy */
- switch (state->token_removal) {
- case CIRCPAD_TOKEN_REMOVAL_CLOSEST_USEC:
- circpad_machine_remove_closest_token(mi, target_bin_usec, 1);
- break;
- case CIRCPAD_TOKEN_REMOVAL_CLOSEST:
- circpad_machine_remove_closest_token(mi, target_bin_usec, 0);
- break;
- case CIRCPAD_TOKEN_REMOVAL_LOWER:
- circpad_machine_remove_lower_token(mi, target_bin_usec);
- break;
- case CIRCPAD_TOKEN_REMOVAL_HIGHER:
- circpad_machine_remove_higher_token(mi, target_bin_usec);
- break;
- case CIRCPAD_TOKEN_REMOVAL_EXACT:
- circpad_machine_remove_exact(mi, target_bin_usec);
- break;
- case CIRCPAD_TOKEN_REMOVAL_NONE:
- default:
- tor_assert_nonfatal_unreached();
- log_warn(LD_BUG, "Circpad: Unknown token removal strategy %d",
- state->token_removal);
- break;
- }
- }
- /**
- * Send a relay command with a relay cell payload on a circuit to
- * the particular hopnum.
- *
- * Hopnum starts at 1 (1=guard, 2=middle, 3=exit, etc).
- *
- * Payload may be null.
- *
- * Returns negative on error, 0 on success.
- */
- MOCK_IMPL(STATIC signed_error_t,
- circpad_send_command_to_hop,(origin_circuit_t *circ, uint8_t hopnum,
- uint8_t relay_command, const uint8_t *payload,
- ssize_t payload_len))
- {
- crypt_path_t *target_hop = circuit_get_cpath_hop(circ, hopnum);
- signed_error_t ret;
- /* Check that the cpath has the target hop */
- if (!target_hop) {
- log_fn(LOG_WARN, LD_BUG, "Padding circuit %u has %d hops, not %d",
- circ->global_identifier, circuit_get_cpath_len(circ), hopnum);
- return -1;
- }
- /* Check that the target hop is opened */
- if (target_hop->state != CPATH_STATE_OPEN) {
- log_fn(LOG_WARN,LD_CIRC,
- "Padding circuit %u has %d hops, not %d",
- circ->global_identifier,
- circuit_get_cpath_opened_len(circ), hopnum);
- return -1;
- }
- /* Send the drop command to the second hop */
- ret = relay_send_command_from_edge(0, TO_CIRCUIT(circ), relay_command,
- (const char*)payload, payload_len,
- target_hop);
- return ret;
- }
- /**
- * Callback helper to send a padding cell.
- *
- * This helper is called after our histogram-sampled delay period passes
- * without another packet being sent first. If a packet is sent before this
- * callback happens, it is canceled. So when we're called here, send padding
- * right away.
- *
- * If sending this padding cell forced us to transition states return
- * CIRCPAD_STATE_CHANGED. Otherwise return CIRCPAD_STATE_UNCHANGED.
- */
- circpad_decision_t
- circpad_send_padding_cell_for_callback(circpad_machine_runtime_t *mi)
- {
- circuit_t *circ = mi->on_circ;
- int machine_idx = mi->machine_index;
- mi->padding_scheduled_at_usec = 0;
- circpad_statenum_t state = mi->current_state;
- /* Make sure circuit didn't close on us */
- if (mi->on_circ->marked_for_close) {
- log_fn(LOG_INFO,LD_CIRC,
- "Padding callback on circuit marked for close (%u). Ignoring.",
- CIRCUIT_IS_ORIGIN(mi->on_circ) ?
- TO_ORIGIN_CIRCUIT(mi->on_circ)->global_identifier : 0);
- return CIRCPAD_STATE_CHANGED;
- }
- circpad_machine_count_padding_sent(mi);
- if (CIRCUIT_IS_ORIGIN(mi->on_circ)) {
- circpad_send_command_to_hop(TO_ORIGIN_CIRCUIT(mi->on_circ),
- CIRCPAD_GET_MACHINE(mi)->target_hopnum,
- RELAY_COMMAND_DROP, NULL, 0);
- log_info(LD_CIRC, "Callback: Sending padding to origin circuit %u"
- " (%d) [length: %"PRIu64"]",
- TO_ORIGIN_CIRCUIT(mi->on_circ)->global_identifier,
- mi->on_circ->purpose, mi->state_length);
- } else {
- // If we're a non-origin circ, we can just send from here as if we're the
- // edge.
- if (TO_OR_CIRCUIT(circ)->p_chan_cells.n <= circpad_max_circ_queued_cells) {
- log_info(LD_CIRC, "Callback: Sending padding to circuit (%d)"
- " [length: %"PRIu64"]", mi->on_circ->purpose, mi->state_length);
- relay_send_command_from_edge(0, mi->on_circ, RELAY_COMMAND_DROP, NULL,
- 0, NULL);
- rep_hist_padding_count_write(PADDING_TYPE_DROP);
- } else {
- static ratelim_t cell_lim = RATELIM_INIT(600);
- log_fn_ratelim(&cell_lim,LOG_NOTICE,LD_CIRC,
- "Too many cells (%d) in circ queue to send padding.",
- TO_OR_CIRCUIT(circ)->p_chan_cells.n);
- }
- }
- /* This is a padding cell sent from the client or from the middle node,
- * (because it's invoked from circuitpadding.c) */
- circpad_cell_event_padding_sent(circ);
- /* The circpad_cell_event_padding_sent() could cause us to transition.
- * Check that we still have a padding machineinfo, and then check our token
- * supply. */
- if (circ->padding_info[machine_idx] != NULL) {
- if (state != circ->padding_info[machine_idx]->current_state)
- return CIRCPAD_STATE_CHANGED;
- else
- return check_machine_token_supply(circ->padding_info[machine_idx]);
- } else {
- return CIRCPAD_STATE_CHANGED;
- }
- }
- /**
- * Tor-timer compatible callback that tells us to send a padding cell.
- *
- * Timers are associated with circpad_machine_runtime_t's. When the machineinfo
- * is freed on a circuit, the timers are cancelled. Since the lifetime
- * of machineinfo is always longer than the timers, handles are not
- * needed.
- */
- static void
- circpad_send_padding_callback(tor_timer_t *timer, void *args,
- const struct monotime_t *time)
- {
- circpad_machine_runtime_t *mi = ((circpad_machine_runtime_t*)args);
- (void)timer; (void)time;
- if (mi && mi->on_circ) {
- assert_circuit_ok(mi->on_circ);
- circpad_send_padding_cell_for_callback(mi);
- } else {
- // This shouldn't happen (represents a timer leak)
- log_fn(LOG_WARN,LD_CIRC,
- "Circuit closed while waiting for padding timer.");
- tor_fragile_assert();
- }
- // TODO-MP-AP: Unify this counter with channelpadding for rephist stats
- //total_timers_pending--;
- }
- /**
- * Cache our consensus parameters upon consensus update.
- */
- void
- circpad_new_consensus_params(const networkstatus_t *ns)
- {
- circpad_padding_disabled =
- networkstatus_get_param(ns, "circpad_padding_disabled",
- 0, 0, 1);
- circpad_padding_reduced =
- networkstatus_get_param(ns, "circpad_padding_reduced",
- 0, 0, 1);
- circpad_global_allowed_cells =
- networkstatus_get_param(ns, "circpad_global_allowed_cells",
- 0, 0, UINT16_MAX-1);
- circpad_global_max_padding_percent =
- networkstatus_get_param(ns, "circpad_global_max_padding_pct",
- 0, 0, 100);
- circpad_max_circ_queued_cells =
- networkstatus_get_param(ns, "circpad_max_circ_queued_cells",
- CIRCWINDOW_START_MAX, 0, 50*CIRCWINDOW_START_MAX);
- }
- /**
- * Return true if padding is allowed by torrc and consensus.
- */
- static bool
- circpad_is_padding_allowed(void)
- {
- /* If padding has been disabled in the consensus, don't send any more
- * padding. Technically the machine should be shut down when the next
- * machine condition check happens, but machine checks only happen on
- * certain circuit events, and if padding is disabled due to some
- * network overload or DoS condition, we really want to stop ASAP. */
- if (circpad_padding_disabled || !get_options()->CircuitPadding) {
- return 0;
- }
- return 1;
- }
- /**
- * Check this machine against its padding limits, as well as global
- * consensus limits.
- *
- * We have two limits: a percent and a cell count. The cell count
- * limit must be reached before the percent is enforced (this is to
- * optionally allow very light padding of things like circuit setup
- * while there is no other traffic on the circuit).
- *
- * TODO: Don't apply limits to machines form torrc.
- *
- * Returns 1 if limits are set and we've hit them. Otherwise returns 0.
- */
- STATIC bool
- circpad_machine_reached_padding_limit(circpad_machine_runtime_t *mi)
- {
- const circpad_machine_spec_t *machine = CIRCPAD_GET_MACHINE(mi);
- /* If machine_padding_pct is non-zero, and we've sent more
- * than the allowed count of padding cells, then check our
- * percent limits for this machine. */
- if (machine->max_padding_percent &&
- mi->padding_sent >= machine->allowed_padding_count) {
- uint32_t total_cells = mi->padding_sent + mi->nonpadding_sent;
- /* Check the percent */
- if ((100*(uint32_t)mi->padding_sent) / total_cells >
- machine->max_padding_percent) {
- return 1; // limit is reached. Stop.
- }
- }
- /* If circpad_max_global_padding_pct is non-zero, and we've
- * sent more than the global padding cell limit, then check our
- * global tor process percentage limit on padding. */
- if (circpad_global_max_padding_percent &&
- circpad_global_padding_sent >= circpad_global_allowed_cells) {
- uint64_t total_cells = circpad_global_padding_sent +
- circpad_global_nonpadding_sent;
- /* Check the percent */
- if ((100*circpad_global_padding_sent) / total_cells >
- circpad_global_max_padding_percent) {
- return 1; // global limit reached. Stop.
- }
- }
- return 0; // All good!
- }
- /**
- * Schedule the next padding time according to the machineinfo on a
- * circuit.
- *
- * The histograms represent inter-packet-delay. Whenever you get an packet
- * event you should be scheduling your next timer (after cancelling any old
- * ones and updating tokens accordingly).
- *
- * Returns 1 if we decide to transition states (due to infinity bin),
- * 0 otherwise.
- */
- MOCK_IMPL(circpad_decision_t,
- circpad_machine_schedule_padding,(circpad_machine_runtime_t *mi))
- {
- circpad_delay_t in_usec = 0;
- struct timeval timeout;
- tor_assert(mi);
- /* Don't schedule padding if it is disabled */
- if (!circpad_is_padding_allowed()) {
- static ratelim_t padding_lim = RATELIM_INIT(600);
- log_fn_ratelim(&padding_lim,LOG_INFO,LD_CIRC,
- "Padding has been disabled, but machine still on circuit %"PRIu64
- ", %d",
- mi->on_circ->n_chan ? mi->on_circ->n_chan->global_identifier : 0,
- mi->on_circ->n_circ_id);
- return CIRCPAD_STATE_UNCHANGED;
- }
- /* Don't schedule padding if we are currently in dormant mode. */
- if (!is_participating_on_network()) {
- log_info(LD_CIRC, "Not scheduling padding because we are dormant.");
- return CIRCPAD_STATE_UNCHANGED;
- }
- // Don't pad in end (but also don't cancel any previously
- // scheduled padding either).
- if (mi->current_state == CIRCPAD_STATE_END) {
- log_fn(LOG_INFO, LD_CIRC, "Padding end state on circuit %u",
- CIRCUIT_IS_ORIGIN(mi->on_circ) ?
- TO_ORIGIN_CIRCUIT(mi->on_circ)->global_identifier : 0);
- return CIRCPAD_STATE_UNCHANGED;
- }
- /* Check our padding limits */
- if (circpad_machine_reached_padding_limit(mi)) {
- if (CIRCUIT_IS_ORIGIN(mi->on_circ)) {
- log_fn(LOG_INFO, LD_CIRC,
- "Padding machine has reached padding limit on circuit %u",
- TO_ORIGIN_CIRCUIT(mi->on_circ)->global_identifier);
- } else {
- static ratelim_t padding_lim = RATELIM_INIT(600);
- log_fn_ratelim(&padding_lim,LOG_INFO,LD_CIRC,
- "Padding machine has reached padding limit on circuit %"PRIu64
- ", %d",
- mi->on_circ->n_chan ? mi->on_circ->n_chan->global_identifier : 0,
- mi->on_circ->n_circ_id);
- }
- return CIRCPAD_STATE_UNCHANGED;
- }
- if (mi->is_padding_timer_scheduled) {
- /* Cancel current timer (if any) */
- timer_disable(mi->padding_timer);
- mi->is_padding_timer_scheduled = 0;
- }
- /* in_usec = in microseconds */
- in_usec = circpad_machine_sample_delay(mi);
- /* If we're using token removal, we need to know when the padding
- * was scheduled at, so we can remove the appropriate token if
- * a non-padding cell is sent before the padding timer expires.
- *
- * However, since monotime is unpredictably expensive, let's avoid
- * using it for machines that don't need token removal. */
- if (circpad_is_token_removal_supported(mi)) {
- mi->padding_scheduled_at_usec = monotime_absolute_usec();
- } else {
- mi->padding_scheduled_at_usec = 1;
- }
- log_fn(LOG_INFO,LD_CIRC,"\tPadding in %u usec on circuit %u", in_usec,
- CIRCUIT_IS_ORIGIN(mi->on_circ) ?
- TO_ORIGIN_CIRCUIT(mi->on_circ)->global_identifier : 0);
- // Don't schedule if we have infinite delay.
- if (in_usec == CIRCPAD_DELAY_INFINITE) {
- return circpad_internal_event_infinity(mi);
- }
- if (mi->state_length == 0) {
- /* If we're at length 0, that means we hit 0 after sending
- * a cell earlier, and emitted an event for it, but
- * for whatever reason we did not decide to change states then.
- * So maybe the machine is waiting for bins empty, or for an
- * infinity event later? That would be a strange machine,
- * but there's no reason to make it impossible. */
- return CIRCPAD_STATE_UNCHANGED;
- }
- if (in_usec <= 0) {
- return circpad_send_padding_cell_for_callback(mi);
- }
- timeout.tv_sec = in_usec/TOR_USEC_PER_SEC;
- timeout.tv_usec = (in_usec%TOR_USEC_PER_SEC);
- log_fn(LOG_INFO, LD_CIRC, "\tPadding circuit %u in %u sec, %u usec",
- CIRCUIT_IS_ORIGIN(mi->on_circ) ?
- TO_ORIGIN_CIRCUIT(mi->on_circ)->global_identifier : 0,
- (unsigned)timeout.tv_sec, (unsigned)timeout.tv_usec);
- if (mi->padding_timer) {
- timer_set_cb(mi->padding_timer, circpad_send_padding_callback, mi);
- } else {
- mi->padding_timer =
- timer_new(circpad_send_padding_callback, mi);
- }
- timer_schedule(mi->padding_timer, &timeout);
- mi->is_padding_timer_scheduled = 1;
- // TODO-MP-AP: Unify with channelpadding counter
- //rep_hist_padding_count_timers(++total_timers_pending);
- return CIRCPAD_STATE_UNCHANGED;
- }
- /**
- * If the machine transitioned to the END state, we need
- * to check to see if it wants us to shut it down immediately.
- * If it does, then we need to send the appropiate negotiation commands
- * depending on which side it is.
- *
- * After this function is called, mi may point to freed memory. Do
- * not access it.
- */
- static void
- circpad_machine_spec_transitioned_to_end(circpad_machine_runtime_t *mi)
- {
- const circpad_machine_spec_t *machine = CIRCPAD_GET_MACHINE(mi);
- circuit_t *on_circ = mi->on_circ;
- log_fn(LOG_INFO,LD_CIRC, "Padding machine in end state on circuit %u (%d)",
- CIRCUIT_IS_ORIGIN(on_circ) ?
- TO_ORIGIN_CIRCUIT(on_circ)->global_identifier : 0,
- on_circ->purpose);
- /*
- * We allow machines to shut down and delete themselves as opposed
- * to just going back to START or waiting forever in END so that
- * we can handle the case where this machine started while it was
- * the only machine that matched conditions, but *since* then more
- * "higher ranking" machines now match the conditions, and would
- * be given a chance to take precedence over this one in
- * circpad_add_matching_machines().
- *
- * Returning to START or waiting forever in END would not give those
- * other machines a chance to be launched, where as shutting down
- * here does.
- */
- if (machine->should_negotiate_end) {
- if (machine->is_origin_side) {
- /* We free the machine info here so that we can be replaced
- * by a different machine. But we must leave the padding_machine
- * in place to wait for the negotiated response */
- circpad_circuit_machineinfo_free_idx(on_circ,
- machine->machine_index);
- circpad_negotiate_padding(TO_ORIGIN_CIRCUIT(on_circ),
- machine->machine_num,
- machine->target_hopnum,
- CIRCPAD_COMMAND_STOP);
- } else {
- circpad_circuit_machineinfo_free_idx(on_circ,
- machine->machine_index);
- circpad_padding_negotiated(on_circ,
- machine->machine_num,
- CIRCPAD_COMMAND_STOP,
- CIRCPAD_RESPONSE_OK);
- on_circ->padding_machine[machine->machine_index] = NULL;
- }
- }
- }
- /**
- * Generic state transition function for padding state machines.
- *
- * Given an event and our mutable machine info, decide if/how to
- * transition to a different state, and perform actions accordingly.
- *
- * Returns 1 if we transition states, 0 otherwise.
- */
- MOCK_IMPL(circpad_decision_t,
- circpad_machine_spec_transition,(circpad_machine_runtime_t *mi,
- circpad_event_t event))
- {
- const circpad_state_t *state =
- circpad_machine_current_state(mi);
- /* If state is null we are in the end state. */
- if (!state) {
- /* If we in end state we don't pad no matter what. */
- return CIRCPAD_STATE_UNCHANGED;
- }
- /* Check if this event is ignored or causes a cancel */
- if (state->next_state[event] == CIRCPAD_STATE_IGNORE) {
- return CIRCPAD_STATE_UNCHANGED;
- } else if (state->next_state[event] == CIRCPAD_STATE_CANCEL) {
- /* Check cancel events and cancel any pending padding */
- mi->padding_scheduled_at_usec = 0;
- if (mi->is_padding_timer_scheduled) {
- mi->is_padding_timer_scheduled = 0;
- /* Cancel current timer (if any) */
- timer_disable(mi->padding_timer);
- }
- return CIRCPAD_STATE_UNCHANGED;
- } else {
- circpad_statenum_t s = state->next_state[event];
- /* See if we need to transition to any other states based on this event.
- * Whenever a transition happens, even to our own state, we schedule
- * padding.
- *
- * So if a state only wants to schedule padding for an event, it specifies
- * a transition to itself. All non-specified events are ignored.
- */
- log_fn(LOG_INFO, LD_CIRC,
- "Circuit %u circpad machine %d transitioning from %u to %u",
- CIRCUIT_IS_ORIGIN(mi->on_circ) ?
- TO_ORIGIN_CIRCUIT(mi->on_circ)->global_identifier : 0,
- mi->machine_index, mi->current_state, s);
- /* If this is not the same state, switch and init tokens,
- * otherwise just reschedule padding. */
- if (mi->current_state != s) {
- mi->current_state = s;
- circpad_machine_setup_tokens(mi);
- circpad_choose_state_length(mi);
- /* If we transition to the end state, check to see
- * if this machine wants to be shut down at end */
- if (s == CIRCPAD_STATE_END) {
- circpad_machine_spec_transitioned_to_end(mi);
- /* We transitioned but we don't pad in end. Also, mi
- * may be freed. Returning STATE_CHANGED prevents us
- * from accessing it in any callers of this function. */
- return CIRCPAD_STATE_CHANGED;
- }
- /* We transitioned to a new state, schedule padding */
- circpad_machine_schedule_padding(mi);
- return CIRCPAD_STATE_CHANGED;
- }
- /* We transitioned back to the same state. Schedule padding,
- * and inform if that causes a state transition. */
- return circpad_machine_schedule_padding(mi);
- }
- return CIRCPAD_STATE_UNCHANGED;
- }
- /**
- * Estimate the circuit RTT from the current middle hop out to the
- * end of the circuit.
- *
- * We estimate RTT by calculating the time between "receive" and
- * "send" at a middle hop. This is because we "receive" a cell
- * from the origin, and then relay it towards the exit before a
- * response comes back. It is that response time from the exit side
- * that we want to measure, so that we can make use of it for synthetic
- * response delays.
- */
- static void
- circpad_estimate_circ_rtt_on_received(circuit_t *circ,
- circpad_machine_runtime_t *mi)
- {
- /* Origin circuits don't estimate RTT. They could do it easily enough,
- * but they have no reason to use it in any delay calculations. */
- if (CIRCUIT_IS_ORIGIN(circ) || mi->stop_rtt_update)
- return;
- /* If we already have a last received packet time, that means we
- * did not get a response before this packet. The RTT estimate
- * only makes sense if we do not have multiple packets on the
- * wire, so stop estimating if this is the second packet
- * back to back. However, for the first set of back-to-back
- * packets, we can wait until the very first response comes back
- * to us, to measure that RTT (for the response to optimistic
- * data, for example). Hence stop_rtt_update is only checked
- * in this received side function, and not in send side below.
- */
- if (mi->last_received_time_usec) {
- /* We also allow multiple back-to-back packets if the circuit is not
- * opened, to handle var cells.
- * XXX: Will this work with out var cell plans? Maybe not,
- * since we're opened at the middle hop as soon as we process
- * one var extend2 :/ */
- if (circ->state == CIRCUIT_STATE_OPEN) {
- log_fn(LOG_INFO, LD_CIRC,
- "Stopping padding RTT estimation on circuit (%"PRIu64
- ", %d) after two back to back packets. Current RTT: %d",
- circ->n_chan ? circ->n_chan->global_identifier : 0,
- circ->n_circ_id, mi->rtt_estimate_usec);
- mi->stop_rtt_update = 1;
- if (!mi->rtt_estimate_usec) {
- static ratelim_t rtt_lim = RATELIM_INIT(600);
- log_fn_ratelim(&rtt_lim,LOG_NOTICE,LD_BUG,
- "Circuit got two cells back to back before estimating RTT.");
- }
- }
- } else {
- const circpad_state_t *state = circpad_machine_current_state(mi);
- if (BUG(!state)) {
- return;
- }
- /* Since monotime is unpredictably expensive, only update this field
- * if rtt estimates are needed. Otherwise, stop the rtt update. */
- if (state->use_rtt_estimate) {
- mi->last_received_time_usec = monotime_absolute_usec();
- } else {
- /* Let's fast-path future decisions not to update rtt if the
- * feature is not in use. */
- mi->stop_rtt_update = 1;
- }
- }
- }
- /**
- * Handles the "send" side of RTT calculation at middle nodes.
- *
- * This function calculates the RTT from the middle to the end
- * of the circuit by subtracting the last received cell timestamp
- * from the current time. It allows back-to-back cells until
- * the circuit is opened, to allow for var cell handshakes.
- * XXX: Check our var cell plans to make sure this will work.
- */
- static void
- circpad_estimate_circ_rtt_on_send(circuit_t *circ,
- circpad_machine_runtime_t *mi)
- {
- /* Origin circuits don't estimate RTT. They could do it easily enough,
- * but they have no reason to use it in any delay calculations. */
- if (CIRCUIT_IS_ORIGIN(circ))
- return;
- /* If last_received_time_usec is non-zero, we are waiting for a response
- * from the exit side. Calculate the time delta and use it as RTT. */
- if (mi->last_received_time_usec) {
- circpad_time_t rtt_time = monotime_absolute_usec() -
- mi->last_received_time_usec;
- /* Reset the last RTT packet time, so we can tell if two cells
- * arrive back to back */
- mi->last_received_time_usec = 0;
- /* Use INT32_MAX to ensure the addition doesn't overflow */
- if (rtt_time >= INT32_MAX) {
- log_fn(LOG_WARN,LD_CIRC,
- "Circuit padding RTT estimate overflowed: %"PRIu64
- " vs %"PRIu64, monotime_absolute_usec(),
- mi->last_received_time_usec);
- return;
- }
- /* If the old RTT estimate is lower than this one, use this one, because
- * the circuit is getting longer. If this estimate is somehow
- * faster than the previous, then maybe that was network jitter, or a
- * bad monotonic clock source (so our ratchet returned a zero delta).
- * In that case, average them. */
- if (mi->rtt_estimate_usec < (circpad_delay_t)rtt_time) {
- mi->rtt_estimate_usec = (circpad_delay_t)rtt_time;
- } else {
- mi->rtt_estimate_usec += (circpad_delay_t)rtt_time;
- mi->rtt_estimate_usec /= 2;
- }
- } else if (circ->state == CIRCUIT_STATE_OPEN) {
- /* If last_received_time_usec is zero, then we have gotten two cells back
- * to back. Stop estimating RTT in this case. Note that we only
- * stop RTT update if the circuit is opened, to allow for RTT estimates
- * of var cells during circ setup. */
- if (!mi->rtt_estimate_usec && !mi->stop_rtt_update) {
- static ratelim_t rtt_lim = RATELIM_INIT(600);
- log_fn_ratelim(&rtt_lim,LOG_NOTICE,LD_BUG,
- "Circuit sent two cells back to back before estimating RTT.");
- }
- mi->stop_rtt_update = 1;
- }
- }
- /**
- * A "non-padding" cell has been sent from this endpoint. React
- * according to any padding state machines on the circuit.
- *
- * For origin circuits, this means we sent a cell into the network.
- * For middle relay circuits, this means we sent a cell towards the
- * origin.
- */
- void
- circpad_cell_event_nonpadding_sent(circuit_t *on_circ)
- {
- /* Update global cell count */
- circpad_global_nonpadding_sent++;
- /* If there are no machines then this loop should not iterate */
- FOR_EACH_ACTIVE_CIRCUIT_MACHINE_BEGIN(i, on_circ) {
- /* First, update any timestamps */
- on_circ->padding_info[i]->last_cell_time_sec = approx_time();
- circpad_estimate_circ_rtt_on_send(on_circ, on_circ->padding_info[i]);
- /* Then, do accounting */
- circpad_machine_count_nonpadding_sent(on_circ->padding_info[i]);
- /* Check to see if we've run out of tokens for this state already,
- * and if not, check for other state transitions */
- if (check_machine_token_supply(on_circ->padding_info[i])
- == CIRCPAD_STATE_UNCHANGED) {
- /* If removing a token did not cause a transition, check if
- * non-padding sent event should */
- circpad_machine_spec_transition(on_circ->padding_info[i],
- CIRCPAD_EVENT_NONPADDING_SENT);
- }
- } FOR_EACH_ACTIVE_CIRCUIT_MACHINE_END;
- }
- /** Check if this cell or circuit are related to circuit padding and handle
- * them if so. Return 0 if the cell was handled in this subsystem and does
- * not need any other consideration, otherwise return 1.
- */
- int
- circpad_check_received_cell(cell_t *cell, circuit_t *circ,
- crypt_path_t *layer_hint,
- const relay_header_t *rh)
- {
- /* First handle the padding commands, since we want to ignore any other
- * commands if this circuit is padding-specific. */
- switch (rh->command) {
- case RELAY_COMMAND_DROP:
- /* Already examined in circpad_deliver_recognized_relay_cell_events */
- return 0;
- case RELAY_COMMAND_PADDING_NEGOTIATE:
- circpad_handle_padding_negotiate(circ, cell);
- return 0;
- case RELAY_COMMAND_PADDING_NEGOTIATED:
- if (circpad_handle_padding_negotiated(circ, cell, layer_hint) == 0)
- circuit_read_valid_data(TO_ORIGIN_CIRCUIT(circ), rh->length);
- return 0;
- }
- /* If this is a padding circuit we don't need to parse any other commands
- * than the padding ones. Just drop them to the floor.
- *
- * Note: we deliberately do not call circuit_read_valid_data() here. The
- * vanguards addon (specifically the 'bandguards' component's dropped cell
- * detection) will thus close this circuit, as it would for any other
- * unexpected cell. However, default tor will *not* close the circuit.
- *
- * This is intentional. We are not yet certain that is it optimal to keep
- * padding circuits open in cases like these, rather than closing them.
- * We suspect that continuing to pad is optimal against a passive classifier,
- * but as soon as the adversary is active (even as a client adversary) this
- * might change.
- *
- * So as a way forward, we log the cell command and circuit number, to
- * help us enumerate the most common instances of this in testing with
- * vanguards, to see which are common enough to verify and handle
- * properly.
- * - Mike
- */
- if (circ->purpose == CIRCUIT_PURPOSE_C_CIRCUIT_PADDING) {
- log_fn(LOG_PROTOCOL_WARN, LD_CIRC,
- "Ignored cell (%d) that arrived in padding circuit "
- " %u.", rh->command, CIRCUIT_IS_ORIGIN(circ) ?
- TO_ORIGIN_CIRCUIT(circ)->global_identifier : 0);
- return 0;
- }
- return 1;
- }
- /**
- * A "non-padding" cell has been received by this endpoint. React
- * according to any padding state machines on the circuit.
- *
- * For origin circuits, this means we read a cell from the network.
- * For middle relay circuits, this means we received a cell from the
- * origin.
- */
- void
- circpad_cell_event_nonpadding_received(circuit_t *on_circ)
- {
- FOR_EACH_ACTIVE_CIRCUIT_MACHINE_BEGIN(i, on_circ) {
- /* First, update any timestamps */
- on_circ->padding_info[i]->last_cell_time_sec = approx_time();
- circpad_estimate_circ_rtt_on_received(on_circ, on_circ->padding_info[i]);
- circpad_machine_spec_transition(on_circ->padding_info[i],
- CIRCPAD_EVENT_NONPADDING_RECV);
- } FOR_EACH_ACTIVE_CIRCUIT_MACHINE_END;
- }
- /**
- * A padding cell has been sent from this endpoint. React
- * according to any padding state machines on the circuit.
- *
- * For origin circuits, this means we sent a cell into the network.
- * For middle relay circuits, this means we sent a cell towards the
- * origin.
- */
- void
- circpad_cell_event_padding_sent(circuit_t *on_circ)
- {
- FOR_EACH_ACTIVE_CIRCUIT_MACHINE_BEGIN(i, on_circ) {
- /* Check to see if we've run out of tokens for this state already,
- * and if not, check for other state transitions */
- if (check_machine_token_supply(on_circ->padding_info[i])
- == CIRCPAD_STATE_UNCHANGED) {
- /* If removing a token did not cause a transition, check if
- * non-padding sent event should */
- on_circ->padding_info[i]->last_cell_time_sec = approx_time();
- circpad_machine_spec_transition(on_circ->padding_info[i],
- CIRCPAD_EVENT_PADDING_SENT);
- }
- } FOR_EACH_ACTIVE_CIRCUIT_MACHINE_END;
- }
- /**
- * A padding cell has been received by this endpoint. React
- * according to any padding state machines on the circuit.
- *
- * For origin circuits, this means we read a cell from the network.
- * For middle relay circuits, this means we received a cell from the
- * origin.
- */
- void
- circpad_cell_event_padding_received(circuit_t *on_circ)
- {
- /* identical to padding sent */
- FOR_EACH_ACTIVE_CIRCUIT_MACHINE_BEGIN(i, on_circ) {
- on_circ->padding_info[i]->last_cell_time_sec = approx_time();
- circpad_machine_spec_transition(on_circ->padding_info[i],
- CIRCPAD_EVENT_PADDING_RECV);
- } FOR_EACH_ACTIVE_CIRCUIT_MACHINE_END;
- }
- /**
- * An "infinite" delay has ben chosen from one of our histograms.
- *
- * "Infinite" delays mean don't send padding -- but they can also
- * mean transition to another state depending on the state machine
- * definitions. Check the rules and react accordingly.
- *
- * Return 1 if we decide to transition, 0 otherwise.
- */
- circpad_decision_t
- circpad_internal_event_infinity(circpad_machine_runtime_t *mi)
- {
- return circpad_machine_spec_transition(mi, CIRCPAD_EVENT_INFINITY);
- }
- /**
- * All of the bins of our current state's histogram's are empty.
- *
- * Check to see if this means transition to another state, and if
- * not, refill the tokens.
- *
- * Return 1 if we decide to transition, 0 otherwise.
- */
- circpad_decision_t
- circpad_internal_event_bins_empty(circpad_machine_runtime_t *mi)
- {
- if (circpad_machine_spec_transition(mi, CIRCPAD_EVENT_BINS_EMPTY)
- == CIRCPAD_STATE_CHANGED) {
- return CIRCPAD_STATE_CHANGED;
- } else {
- /* If we dont transition, then we refill the tokens */
- circpad_machine_setup_tokens(mi);
- return CIRCPAD_STATE_UNCHANGED;
- }
- }
- /**
- * This state has used up its cell count. Emit the event and
- * see if we transition.
- *
- * Return 1 if we decide to transition, 0 otherwise.
- */
- circpad_decision_t
- circpad_internal_event_state_length_up(circpad_machine_runtime_t *mi)
- {
- return circpad_machine_spec_transition(mi, CIRCPAD_EVENT_LENGTH_COUNT);
- }
- /**
- * Returns true if the circuit matches the conditions.
- */
- static inline bool
- circpad_machine_conditions_met(origin_circuit_t *circ,
- const circpad_machine_spec_t *machine)
- {
- /* If padding is disabled, no machines should match/apply. This has
- * the effect of shutting down all machines, and not adding any more. */
- if (circpad_padding_disabled || !get_options()->CircuitPadding)
- return 0;
- /* If the consensus or our torrc has selected reduced connection padding,
- * then only allow this machine if it is flagged as acceptable under
- * reduced padding conditions */
- if (circpad_padding_reduced || get_options()->ReducedCircuitPadding) {
- if (!machine->conditions.reduced_padding_ok)
- return 0;
- }
- if (!(circpad_circ_purpose_to_mask(TO_CIRCUIT(circ)->purpose)
- & machine->conditions.purpose_mask))
- return 0;
- if (machine->conditions.requires_vanguards) {
- const or_options_t *options = get_options();
- /* Pinned middles are effectively vanguards */
- if (!(options->HSLayer2Nodes || options->HSLayer3Nodes))
- return 0;
- }
- /* We check for any bits set in the circuit state mask so that machines
- * can say any of the following through their state bitmask:
- * "I want to apply to circuits with either streams or no streams"; OR
- * "I only want to apply to circuits with streams"; OR
- * "I only want to apply to circuits without streams". */
- if (!(circpad_circuit_state(circ) & machine->conditions.state_mask))
- return 0;
- if (circuit_get_cpath_opened_len(circ) < machine->conditions.min_hops)
- return 0;
- return 1;
- }
- /**
- * Returns a minimized representation of the circuit state.
- *
- * The padding code only cares if the circuit is building,
- * opened, used for streams, and/or still has relay early cells.
- * This returns a bitmask of all state properities that apply to
- * this circuit.
- */
- static inline
- circpad_circuit_state_t
- circpad_circuit_state(origin_circuit_t *circ)
- {
- circpad_circuit_state_t retmask = 0;
- if (circ->p_streams)
- retmask |= CIRCPAD_CIRC_STREAMS;
- else
- retmask |= CIRCPAD_CIRC_NO_STREAMS;
- /* We use has_opened to prevent cannibialized circs from flapping. */
- if (circ->has_opened)
- retmask |= CIRCPAD_CIRC_OPENED;
- else
- retmask |= CIRCPAD_CIRC_BUILDING;
- if (circ->remaining_relay_early_cells > 0)
- retmask |= CIRCPAD_CIRC_HAS_RELAY_EARLY;
- else
- retmask |= CIRCPAD_CIRC_HAS_NO_RELAY_EARLY;
- return retmask;
- }
- /**
- * Convert a normal circuit purpose into a bitmask that we can
- * use for determining matching circuits.
- */
- circpad_purpose_mask_t
- circpad_circ_purpose_to_mask(uint8_t circ_purpose)
- {
- /* Treat OR circ purposes as ignored. They should not be passed here*/
- if (BUG(circ_purpose <= CIRCUIT_PURPOSE_OR_MAX_)) {
- return 0;
- }
- /* Treat new client circuit purposes as "OMG ITS EVERYTHING".
- * This also should not happen */
- if (BUG(circ_purpose - CIRCUIT_PURPOSE_OR_MAX_ - 1 > 32)) {
- return CIRCPAD_PURPOSE_ALL;
- }
- /* Convert the purpose to a bit position */
- return 1 << (circ_purpose - CIRCUIT_PURPOSE_OR_MAX_ - 1);
- }
- /**
- * Shut down any machines whose conditions no longer match
- * the current circuit.
- */
- static void
- circpad_shutdown_old_machines(origin_circuit_t *on_circ)
- {
- circuit_t *circ = TO_CIRCUIT(on_circ);
- FOR_EACH_ACTIVE_CIRCUIT_MACHINE_BEGIN(i, circ) {
- if (!circpad_machine_conditions_met(on_circ,
- circ->padding_machine[i])) {
- // Clear machineinfo (frees timers)
- circpad_circuit_machineinfo_free_idx(circ, i);
- // Send padding negotiate stop
- circpad_negotiate_padding(on_circ,
- circ->padding_machine[i]->machine_num,
- circ->padding_machine[i]->target_hopnum,
- CIRCPAD_COMMAND_STOP);
- }
- } FOR_EACH_ACTIVE_CIRCUIT_MACHINE_END;
- }
- /**
- * Negotiate new machines that would apply to this circuit, given the machines
- * inside <b>machines_sl</b>.
- *
- * This function checks to see if we have any free machine indexes,
- * and for each free machine index, it initializes the most recently
- * added origin-side padding machine that matches the target machine
- * index and circuit conditions, and negotiates it with the appropriate
- * middle relay.
- */
- STATIC void
- circpad_add_matching_machines(origin_circuit_t *on_circ,
- smartlist_t *machines_sl)
- {
- circuit_t *circ = TO_CIRCUIT(on_circ);
- #ifdef TOR_UNIT_TESTS
- /* Tests don't have to init our padding machines */
- if (!machines_sl)
- return;
- #endif
- /* If padding negotiation failed before, do not try again */
- if (on_circ->padding_negotiation_failed)
- return;
- FOR_EACH_CIRCUIT_MACHINE_BEGIN(i) {
- /* If there is a padding machine info, this index is occupied.
- * No need to check conditions for this index. */
- if (circ->padding_info[i])
- continue;
- /* We have a free machine index. Check the origin padding
- * machines in reverse order, so that more recently added
- * machines take priority over older ones. */
- SMARTLIST_FOREACH_REVERSE_BEGIN(machines_sl,
- circpad_machine_spec_t *,
- machine) {
- /* Machine definitions have a specific target machine index.
- * This is so event ordering is deterministic with respect
- * to which machine gets events first when there are two
- * machines installed on a circuit. Make sure we only
- * add this machine if its target machine index is free. */
- if (machine->machine_index == i &&
- circpad_machine_conditions_met(on_circ, machine)) {
- // We can only replace this machine if the target hopnum
- // is the same, otherwise we'll get invalid data
- if (circ->padding_machine[i]) {
- if (circ->padding_machine[i]->target_hopnum !=
- machine->target_hopnum)
- continue;
- /* Replace it. (Don't free - is global). */
- circ->padding_machine[i] = NULL;
- }
- /* Set up the machine immediately so that the slot is occupied.
- * We will tear it down on error return, or if there is an error
- * response from the relay. */
- circpad_setup_machine_on_circ(circ, machine);
- if (circpad_negotiate_padding(on_circ, machine->machine_num,
- machine->target_hopnum,
- CIRCPAD_COMMAND_START) < 0) {
- log_info(LD_CIRC,
- "Padding not negotiated. Cleaning machine from circuit %u",
- CIRCUIT_IS_ORIGIN(circ) ?
- TO_ORIGIN_CIRCUIT(circ)->global_identifier : 0);
- circpad_circuit_machineinfo_free_idx(circ, i);
- circ->padding_machine[i] = NULL;
- on_circ->padding_negotiation_failed = 1;
- } else {
- /* Success. Don't try any more machines */
- return;
- }
- }
- } SMARTLIST_FOREACH_END(machine);
- } FOR_EACH_CIRCUIT_MACHINE_END;
- }
- /**
- * Event that tells us we added a hop to an origin circuit.
- *
- * This event is used to decide if we should create a padding machine
- * on a circuit.
- */
- void
- circpad_machine_event_circ_added_hop(origin_circuit_t *on_circ)
- {
- /* Since our padding conditions do not specify a max_hops,
- * all we can do is add machines here */
- circpad_add_matching_machines(on_circ, origin_padding_machines);
- }
- /**
- * Event that tells us that an origin circuit is now built.
- *
- * Shut down any machines that only applied to un-built circuits.
- * Activate any new ones.
- */
- void
- circpad_machine_event_circ_built(origin_circuit_t *circ)
- {
- circpad_shutdown_old_machines(circ);
- circpad_add_matching_machines(circ, origin_padding_machines);
- }
- /**
- * Circpad purpose changed event.
- *
- * Shut down any machines that don't apply to our circ purpose.
- * Activate any new ones that do.
- */
- void
- circpad_machine_event_circ_purpose_changed(origin_circuit_t *circ)
- {
- circpad_shutdown_old_machines(circ);
- circpad_add_matching_machines(circ, origin_padding_machines);
- }
- /**
- * Event that tells us that an origin circuit is out of RELAY_EARLY
- * cells.
- *
- * Shut down any machines that only applied to RELAY_EARLY circuits.
- * Activate any new ones.
- */
- void
- circpad_machine_event_circ_has_no_relay_early(origin_circuit_t *circ)
- {
- circpad_shutdown_old_machines(circ);
- circpad_add_matching_machines(circ, origin_padding_machines);
- }
- /**
- * Streams attached event.
- *
- * Called from link_apconn_to_circ() and handle_hs_exit_conn()
- *
- * Shut down any machines that only applied to machines without
- * streams. Activate any new ones.
- */
- void
- circpad_machine_event_circ_has_streams(origin_circuit_t *circ)
- {
- circpad_shutdown_old_machines(circ);
- circpad_add_matching_machines(circ, origin_padding_machines);
- }
- /**
- * Streams detached event.
- *
- * Called from circuit_detach_stream()
- *
- * Shut down any machines that only applied to machines without
- * streams. Activate any new ones.
- */
- void
- circpad_machine_event_circ_has_no_streams(origin_circuit_t *circ)
- {
- circpad_shutdown_old_machines(circ);
- circpad_add_matching_machines(circ, origin_padding_machines);
- }
- /**
- * Verify that padding is coming from the expected hop.
- *
- * Returns true if from_hop matches the target hop from
- * one of our padding machines.
- *
- * Returns false if we're not an origin circuit, or if from_hop
- * does not match one of the padding machines.
- */
- bool
- circpad_padding_is_from_expected_hop(circuit_t *circ,
- crypt_path_t *from_hop)
- {
- crypt_path_t *target_hop = NULL;
- if (!CIRCUIT_IS_ORIGIN(circ))
- return 0;
- FOR_EACH_CIRCUIT_MACHINE_BEGIN(i) {
- /* We have to check padding_machine and not padding_info/active
- * machines here because padding may arrive after we shut down a
- * machine. The info is gone, but the padding_machine waits
- * for the padding_negotiated response to come back. */
- if (!circ->padding_machine[i])
- continue;
- target_hop = circuit_get_cpath_hop(TO_ORIGIN_CIRCUIT(circ),
- circ->padding_machine[i]->target_hopnum);
- if (target_hop == from_hop)
- return 1;
- } FOR_EACH_CIRCUIT_MACHINE_END;
- return 0;
- }
- /**
- * Deliver circpad events for an "unrecognized cell".
- *
- * Unrecognized cells are sent to relays and are forwarded
- * onto the next hop of their circuits. Unrecognized cells
- * are by definition not padding. We need to tell relay-side
- * state machines that a non-padding cell was sent or received,
- * depending on the direction, so they can update their histograms
- * and decide to pad or not.
- */
- void
- circpad_deliver_unrecognized_cell_events(circuit_t *circ,
- cell_direction_t dir)
- {
- // We should never see unrecognized cells at origin.
- // Our caller emits a warn when this happens.
- if (CIRCUIT_IS_ORIGIN(circ)) {
- return;
- }
- if (dir == CELL_DIRECTION_OUT) {
- /* When direction is out (away from origin), then we received non-padding
- cell coming from the origin to us. */
- circpad_cell_event_nonpadding_received(circ);
- } else if (dir == CELL_DIRECTION_IN) {
- /* It's in and not origin, so the cell is going away from us.
- * So we are relaying a non-padding cell towards the origin. */
- circpad_cell_event_nonpadding_sent(circ);
- }
- }
- /**
- * Deliver circpad events for "recognized" relay cells.
- *
- * Recognized cells are destined for this hop, either client or middle.
- * Check if this is a padding cell or not, and send the appropiate
- * received event.
- */
- void
- circpad_deliver_recognized_relay_cell_events(circuit_t *circ,
- uint8_t relay_command,
- crypt_path_t *layer_hint)
- {
- if (relay_command == RELAY_COMMAND_DROP) {
- rep_hist_padding_count_read(PADDING_TYPE_DROP);
- if (CIRCUIT_IS_ORIGIN(circ)) {
- if (circpad_padding_is_from_expected_hop(circ, layer_hint)) {
- circuit_read_valid_data(TO_ORIGIN_CIRCUIT(circ), 0);
- } else {
- /* This is unexpected padding. Ignore it for now. */
- return;
- }
- }
- /* The cell should be recognized by now, which means that we are on the
- destination, which means that we received a padding cell. We might be
- the client or the Middle node, still, because leaky-pipe. */
- circpad_cell_event_padding_received(circ);
- log_fn(LOG_INFO, LD_CIRC, "Got padding cell on %s circuit %u.",
- CIRCUIT_IS_ORIGIN(circ) ? "origin" : "non-origin",
- CIRCUIT_IS_ORIGIN(circ) ?
- TO_ORIGIN_CIRCUIT(circ)->global_identifier : 0);
- } else {
- /* We received a non-padding cell on the edge */
- circpad_cell_event_nonpadding_received(circ);
- }
- }
- /**
- * Deliver circpad events for relay cells sent from us.
- *
- * If this is a padding cell, update our padding stats
- * and deliver the event. Otherwise just deliver the event.
- */
- void
- circpad_deliver_sent_relay_cell_events(circuit_t *circ,
- uint8_t relay_command)
- {
- /* RELAY_COMMAND_DROP is the multi-hop (aka circuit-level) padding cell in
- * tor. (CELL_PADDING is a channel-level padding cell, which is not relayed
- * or processed here).
- *
- * We do generate events for PADDING_NEGOTIATE and PADDING_NEGOTIATED cells.
- */
- if (relay_command == RELAY_COMMAND_DROP) {
- /* Optimization: The event for RELAY_COMMAND_DROP is sent directly
- * from circpad_send_padding_cell_for_callback(). This is to avoid
- * putting a cell_t and a relay_header_t on the stack repeatedly
- * if we decide to send a long train of padding cells back-to-back
- * with 0 delay. So we do nothing here. */
- return;
- } else {
- /* This is a non-padding cell sent from the client or from
- * this node. */
- circpad_cell_event_nonpadding_sent(circ);
- }
- }
- /**
- * Initialize the states array for a circpad machine.
- */
- void
- circpad_machine_states_init(circpad_machine_spec_t *machine,
- circpad_statenum_t num_states)
- {
- if (BUG(num_states > CIRCPAD_MAX_MACHINE_STATES)) {
- num_states = CIRCPAD_MAX_MACHINE_STATES;
- }
- machine->num_states = num_states;
- machine->states = tor_malloc_zero(sizeof(circpad_state_t)*num_states);
- /* Initialize the default next state for all events to
- * "ignore" -- if events aren't specified, they are ignored. */
- for (circpad_statenum_t s = 0; s < num_states; s++) {
- for (int e = 0; e < CIRCPAD_NUM_EVENTS; e++) {
- machine->states[s].next_state[e] = CIRCPAD_STATE_IGNORE;
- }
- }
- }
- static void
- circpad_setup_machine_on_circ(circuit_t *on_circ,
- const circpad_machine_spec_t *machine)
- {
- if (CIRCUIT_IS_ORIGIN(on_circ) && !machine->is_origin_side) {
- log_fn(LOG_WARN, LD_BUG,
- "Can't set up non-origin machine on origin circuit!");
- return;
- }
- if (!CIRCUIT_IS_ORIGIN(on_circ) && machine->is_origin_side) {
- log_fn(LOG_WARN, LD_BUG,
- "Can't set up origin machine on non-origin circuit!");
- return;
- }
- tor_assert_nonfatal(on_circ->padding_machine[machine->machine_index]
- == NULL);
- tor_assert_nonfatal(on_circ->padding_info[machine->machine_index] == NULL);
- /* Log message */
- if (CIRCUIT_IS_ORIGIN(on_circ)) {
- log_info(LD_CIRC, "Registering machine %s to origin circ %u (%d)",
- machine->name,
- TO_ORIGIN_CIRCUIT(on_circ)->global_identifier, on_circ->purpose);
- } else {
- log_info(LD_CIRC, "Registering machine %s to non-origin circ (%d)",
- machine->name, on_circ->purpose);
- }
- on_circ->padding_info[machine->machine_index] =
- circpad_circuit_machineinfo_new(on_circ, machine->machine_index);
- on_circ->padding_machine[machine->machine_index] = machine;
- }
- /** Validate a single state of a padding machine */
- static bool
- padding_machine_state_is_valid(const circpad_state_t *state)
- {
- int b;
- uint32_t tokens_count = 0;
- circpad_delay_t prev_bin_edge = 0;
- /* We only validate histograms */
- if (!state->histogram_len) {
- return true;
- }
- /* We need at least two bins in a histogram */
- if (state->histogram_len < 2) {
- log_warn(LD_CIRC, "You can't have a histogram with less than 2 bins");
- return false;
- }
- /* For each machine state, if it's a histogram, make sure all the
- * histogram edges are well defined (i.e. are strictly monotonic). */
- for (b = 0 ; b < state->histogram_len ; b++) {
- /* Check that histogram edges are strictly increasing. Ignore the first
- * edge since it can be zero. */
- if (prev_bin_edge >= state->histogram_edges[b] && b > 0) {
- log_warn(LD_CIRC, "Histogram edges are not increasing [%u/%u]",
- prev_bin_edge, state->histogram_edges[b]);
- return false;
- }
- prev_bin_edge = state->histogram_edges[b];
- /* Also count the number of tokens as we go through the histogram states */
- tokens_count += state->histogram[b];
- }
- /* Verify that the total number of tokens is correct */
- if (tokens_count != state->histogram_total_tokens) {
- log_warn(LD_CIRC, "Histogram token count is wrong [%u/%u]",
- tokens_count, state->histogram_total_tokens);
- return false;
- }
- return true;
- }
- /** Basic validation of padding machine */
- static bool
- padding_machine_is_valid(const circpad_machine_spec_t *machine)
- {
- int i;
- /* Validate the histograms of the padding machine */
- for (i = 0 ; i < machine->num_states ; i++) {
- if (!padding_machine_state_is_valid(&machine->states[i])) {
- return false;
- }
- }
- return true;
- }
- /* Validate and register <b>machine</b> into <b>machine_list</b>. If
- * <b>machine_list</b> is NULL, then just validate. */
- void
- circpad_register_padding_machine(circpad_machine_spec_t *machine,
- smartlist_t *machine_list)
- {
- if (!padding_machine_is_valid(machine)) {
- log_warn(LD_CIRC, "Machine #%u is invalid. Ignoring.",
- machine->machine_num);
- return;
- }
- if (machine_list) {
- smartlist_add(machine_list, machine);
- }
- }
- #ifdef TOR_UNIT_TESTS
- /* These padding machines are only used for tests pending #28634. */
- static void
- circpad_circ_client_machine_init(void)
- {
- circpad_machine_spec_t *circ_client_machine
- = tor_malloc_zero(sizeof(circpad_machine_spec_t));
- circ_client_machine->conditions.min_hops = 2;
- circ_client_machine->conditions.state_mask =
- CIRCPAD_CIRC_BUILDING|CIRCPAD_CIRC_OPENED|CIRCPAD_CIRC_HAS_RELAY_EARLY;
- circ_client_machine->conditions.purpose_mask = CIRCPAD_PURPOSE_ALL;
- circ_client_machine->conditions.reduced_padding_ok = 1;
- circ_client_machine->target_hopnum = 2;
- circ_client_machine->is_origin_side = 1;
- /* Start, gap, burst */
- circpad_machine_states_init(circ_client_machine, 3);
- circ_client_machine->states[CIRCPAD_STATE_START].
- next_state[CIRCPAD_EVENT_NONPADDING_RECV] = CIRCPAD_STATE_BURST;
- circ_client_machine->states[CIRCPAD_STATE_BURST].
- next_state[CIRCPAD_EVENT_NONPADDING_RECV] = CIRCPAD_STATE_BURST;
- circ_client_machine->states[CIRCPAD_STATE_BURST].
- next_state[CIRCPAD_EVENT_PADDING_RECV] = CIRCPAD_STATE_BURST;
- /* If we are in burst state, and we send a non-padding cell, then we cancel
- the timer for the next padding cell:
- We dont want to send fake extends when actual extends are going on */
- circ_client_machine->states[CIRCPAD_STATE_BURST].
- next_state[CIRCPAD_EVENT_NONPADDING_SENT] = CIRCPAD_STATE_CANCEL;
- circ_client_machine->states[CIRCPAD_STATE_BURST].
- next_state[CIRCPAD_EVENT_BINS_EMPTY] = CIRCPAD_STATE_END;
- circ_client_machine->states[CIRCPAD_STATE_BURST].token_removal =
- CIRCPAD_TOKEN_REMOVAL_CLOSEST;
- circ_client_machine->states[CIRCPAD_STATE_BURST].histogram_len = 2;
- circ_client_machine->states[CIRCPAD_STATE_BURST].histogram_edges[0]= 500;
- circ_client_machine->states[CIRCPAD_STATE_BURST].histogram_edges[1]= 1000000;
- /* We have 5 tokens in the histogram, which means that all circuits will look
- * like they have 7 hops (since we start this machine after the second hop,
- * and tokens are decremented for any valid hops, and fake extends are
- * used after that -- 2+5==7). */
- circ_client_machine->states[CIRCPAD_STATE_BURST].histogram[0] = 5;
- circ_client_machine->states[CIRCPAD_STATE_BURST].histogram_total_tokens = 5;
- circ_client_machine->machine_num = smartlist_len(origin_padding_machines);
- circpad_register_padding_machine(circ_client_machine,
- origin_padding_machines);
- }
- static void
- circpad_circ_responder_machine_init(void)
- {
- circpad_machine_spec_t *circ_responder_machine
- = tor_malloc_zero(sizeof(circpad_machine_spec_t));
- /* Shut down the machine after we've sent enough packets */
- circ_responder_machine->should_negotiate_end = 1;
- /* The relay-side doesn't care what hopnum it is, but for consistency,
- * let's match the client */
- circ_responder_machine->target_hopnum = 2;
- circ_responder_machine->is_origin_side = 0;
- /* Start, gap, burst */
- circpad_machine_states_init(circ_responder_machine, 3);
- /* This is the settings of the state machine. In the future we are gonna
- serialize this into the consensus or the torrc */
- /* We transition to the burst state on padding receive and on non-padding
- * recieve */
- circ_responder_machine->states[CIRCPAD_STATE_START].
- next_state[CIRCPAD_EVENT_PADDING_RECV] = CIRCPAD_STATE_BURST;
- circ_responder_machine->states[CIRCPAD_STATE_START].
- next_state[CIRCPAD_EVENT_NONPADDING_RECV] = CIRCPAD_STATE_BURST;
- /* Inside the burst state we _stay_ in the burst state when a non-padding
- * is sent */
- circ_responder_machine->states[CIRCPAD_STATE_BURST].
- next_state[CIRCPAD_EVENT_NONPADDING_SENT] = CIRCPAD_STATE_BURST;
- /* Inside the burst state we transition to the gap state when we receive a
- * padding cell */
- circ_responder_machine->states[CIRCPAD_STATE_BURST].
- next_state[CIRCPAD_EVENT_PADDING_RECV] = CIRCPAD_STATE_GAP;
- /* These describe the padding charasteristics when in burst state */
- /* use_rtt_estimate tries to estimate how long padding cells take to go from
- C->M, and uses that as what as the base of the histogram */
- circ_responder_machine->states[CIRCPAD_STATE_BURST].use_rtt_estimate = 1;
- /* The histogram is 2 bins: an empty one, and infinity */
- circ_responder_machine->states[CIRCPAD_STATE_BURST].histogram_len = 2;
- circ_responder_machine->states[CIRCPAD_STATE_BURST].histogram_edges[0]= 500;
- circ_responder_machine->states[CIRCPAD_STATE_BURST].histogram_edges[1] =
- 1000000;
- /* During burst state we wait forever for padding to arrive.
- We are waiting for a padding cell from the client to come in, so that we
- respond, and we immitate how extend looks like */
- circ_responder_machine->states[CIRCPAD_STATE_BURST].histogram[0] = 0;
- // Only infinity bin:
- circ_responder_machine->states[CIRCPAD_STATE_BURST].histogram[1] = 1;
- circ_responder_machine->states[CIRCPAD_STATE_BURST].
- histogram_total_tokens = 1;
- /* From the gap state, we _stay_ in the gap state, when we receive padding
- * or non padding */
- circ_responder_machine->states[CIRCPAD_STATE_GAP].
- next_state[CIRCPAD_EVENT_PADDING_RECV] = CIRCPAD_STATE_GAP;
- circ_responder_machine->states[CIRCPAD_STATE_GAP].
- next_state[CIRCPAD_EVENT_NONPADDING_RECV] = CIRCPAD_STATE_GAP;
- /* And from the gap state, we go to the end, when the bins are empty or a
- * non-padding cell is sent */
- circ_responder_machine->states[CIRCPAD_STATE_GAP].
- next_state[CIRCPAD_EVENT_BINS_EMPTY] = CIRCPAD_STATE_END;
- circ_responder_machine->states[CIRCPAD_STATE_GAP].
- next_state[CIRCPAD_EVENT_NONPADDING_SENT] = CIRCPAD_STATE_END;
- // FIXME: Tune this histogram
- /* The gap state is the delay you wait after you receive a padding cell
- before you send a padding response */
- circ_responder_machine->states[CIRCPAD_STATE_GAP].use_rtt_estimate = 1;
- circ_responder_machine->states[CIRCPAD_STATE_GAP].histogram_len = 6;
- /* Specify histogram bins */
- circ_responder_machine->states[CIRCPAD_STATE_GAP].histogram_edges[0]= 500;
- circ_responder_machine->states[CIRCPAD_STATE_GAP].histogram_edges[1]= 1000;
- circ_responder_machine->states[CIRCPAD_STATE_GAP].histogram_edges[2]= 2000;
- circ_responder_machine->states[CIRCPAD_STATE_GAP].histogram_edges[3]= 4000;
- circ_responder_machine->states[CIRCPAD_STATE_GAP].histogram_edges[4]= 8000;
- circ_responder_machine->states[CIRCPAD_STATE_GAP].histogram_edges[5]= 16000;
- /* Specify histogram tokens */
- circ_responder_machine->states[CIRCPAD_STATE_GAP].histogram[0] = 0;
- circ_responder_machine->states[CIRCPAD_STATE_GAP].histogram[1] = 1;
- circ_responder_machine->states[CIRCPAD_STATE_GAP].histogram[2] = 2;
- circ_responder_machine->states[CIRCPAD_STATE_GAP].histogram[3] = 2;
- circ_responder_machine->states[CIRCPAD_STATE_GAP].histogram[4] = 1;
- /* Total number of tokens */
- circ_responder_machine->states[CIRCPAD_STATE_GAP].histogram_total_tokens = 6;
- circ_responder_machine->states[CIRCPAD_STATE_GAP].token_removal =
- CIRCPAD_TOKEN_REMOVAL_CLOSEST_USEC;
- circ_responder_machine->machine_num = smartlist_len(relay_padding_machines);
- circpad_register_padding_machine(circ_responder_machine,
- relay_padding_machines);
- }
- #endif /* defined(TOR_UNIT_TESTS) */
- /**
- * Initialize all of our padding machines.
- *
- * This is called at startup. It sets up some global machines, and then
- * loads some from torrc, and from the tor consensus.
- */
- void
- circpad_machines_init(void)
- {
- tor_assert_nonfatal(origin_padding_machines == NULL);
- tor_assert_nonfatal(relay_padding_machines == NULL);
- origin_padding_machines = smartlist_new();
- relay_padding_machines = smartlist_new();
- /* Register machines for hiding client-side intro circuits */
- circpad_machine_client_hide_intro_circuits(origin_padding_machines);
- circpad_machine_relay_hide_intro_circuits(relay_padding_machines);
- /* Register machines for hiding client-side rendezvous circuits */
- circpad_machine_client_hide_rend_circuits(origin_padding_machines);
- circpad_machine_relay_hide_rend_circuits(relay_padding_machines);
- // TODO: Parse machines from consensus and torrc
- #ifdef TOR_UNIT_TESTS
- circpad_circ_client_machine_init();
- circpad_circ_responder_machine_init();
- #endif
- }
- /**
- * Free our padding machines
- */
- void
- circpad_machines_free(void)
- {
- if (origin_padding_machines) {
- SMARTLIST_FOREACH(origin_padding_machines,
- circpad_machine_spec_t *,
- m, tor_free(m->states); tor_free(m));
- smartlist_free(origin_padding_machines);
- }
- if (relay_padding_machines) {
- SMARTLIST_FOREACH(relay_padding_machines,
- circpad_machine_spec_t *,
- m, tor_free(m->states); tor_free(m));
- smartlist_free(relay_padding_machines);
- }
- }
- /**
- * Check the Protover info to see if a node supports padding.
- */
- static bool
- circpad_node_supports_padding(const node_t *node)
- {
- if (node->rs) {
- log_fn(LOG_INFO, LD_CIRC, "Checking padding: %s",
- node->rs->pv.supports_hs_setup_padding ?
- "supported" : "unsupported");
- return node->rs->pv.supports_hs_setup_padding;
- }
- log_fn(LOG_INFO, LD_CIRC, "Empty routerstatus in padding check");
- return 0;
- }
- /**
- * Get a node_t for the nth hop in our circuit, starting from 1.
- *
- * Returns node_t from the consensus for that hop, if it is opened.
- * Otherwise returns NULL.
- */
- MOCK_IMPL(STATIC const node_t *,
- circuit_get_nth_node,(origin_circuit_t *circ, int hop))
- {
- crypt_path_t *iter = circuit_get_cpath_hop(circ, hop);
- if (!iter || iter->state != CPATH_STATE_OPEN)
- return NULL;
- return node_get_by_id(iter->extend_info->identity_digest);
- }
- /**
- * Return true if a particular circuit supports padding
- * at the desired hop.
- */
- static bool
- circpad_circuit_supports_padding(origin_circuit_t *circ,
- int target_hopnum)
- {
- const node_t *hop;
- if (!(hop = circuit_get_nth_node(circ, target_hopnum))) {
- return 0;
- }
- return circpad_node_supports_padding(hop);
- }
- /**
- * Try to negotiate padding.
- *
- * Returns -1 on error, 0 on success.
- */
- signed_error_t
- circpad_negotiate_padding(origin_circuit_t *circ,
- circpad_machine_num_t machine,
- uint8_t target_hopnum,
- uint8_t command)
- {
- circpad_negotiate_t type;
- cell_t cell;
- ssize_t len;
- /* Check that the target hop lists support for padding in
- * its ProtoVer fields */
- if (!circpad_circuit_supports_padding(circ, target_hopnum)) {
- return -1;
- }
- memset(&cell, 0, sizeof(cell_t));
- memset(&type, 0, sizeof(circpad_negotiate_t));
- // This gets reset to RELAY_EARLY appropriately by
- // relay_send_command_from_edge_. At least, it looks that way.
- // QQQ-MP-AP: Verify that.
- cell.command = CELL_RELAY;
- circpad_negotiate_set_command(&type, command);
- circpad_negotiate_set_version(&type, 0);
- circpad_negotiate_set_machine_type(&type, machine);
- if ((len = circpad_negotiate_encode(cell.payload, CELL_PAYLOAD_SIZE,
- &type)) < 0)
- return -1;
- log_fn(LOG_INFO,LD_CIRC,
- "Negotiating padding on circuit %u (%d), command %d",
- circ->global_identifier, TO_CIRCUIT(circ)->purpose, command);
- return circpad_send_command_to_hop(circ, target_hopnum,
- RELAY_COMMAND_PADDING_NEGOTIATE,
- cell.payload, len);
- }
- /**
- * Try to negotiate padding.
- *
- * Returns 1 if successful (or already set up), 0 otherwise.
- */
- bool
- circpad_padding_negotiated(circuit_t *circ,
- circpad_machine_num_t machine,
- uint8_t command,
- uint8_t response)
- {
- circpad_negotiated_t type;
- cell_t cell;
- ssize_t len;
- memset(&cell, 0, sizeof(cell_t));
- memset(&type, 0, sizeof(circpad_negotiated_t));
- // This gets reset to RELAY_EARLY appropriately by
- // relay_send_command_from_edge_. At least, it looks that way.
- // QQQ-MP-AP: Verify that.
- cell.command = CELL_RELAY;
- circpad_negotiated_set_command(&type, command);
- circpad_negotiated_set_response(&type, response);
- circpad_negotiated_set_version(&type, 0);
- circpad_negotiated_set_machine_type(&type, machine);
- if ((len = circpad_negotiated_encode(cell.payload, CELL_PAYLOAD_SIZE,
- &type)) < 0)
- return 0;
- /* Use relay_send because we're from the middle to the origin. We don't
- * need to specify a target hop or layer_hint. */
- return relay_send_command_from_edge(0, circ,
- RELAY_COMMAND_PADDING_NEGOTIATED,
- (void*)cell.payload,
- (size_t)len, NULL) == 0;
- }
- /**
- * Parse and react to a padding_negotiate cell.
- *
- * This is called at the middle node upon receipt of the client's choice of
- * state machine, so that it can use the requested state machine index, if
- * it is available.
- *
- * Returns -1 on error, 0 on success.
- */
- signed_error_t
- circpad_handle_padding_negotiate(circuit_t *circ, cell_t *cell)
- {
- int retval = 0;
- circpad_negotiate_t *negotiate;
- if (CIRCUIT_IS_ORIGIN(circ)) {
- log_fn(LOG_PROTOCOL_WARN, LD_CIRC,
- "Padding negotiate cell unsupported at origin (circuit %u)",
- TO_ORIGIN_CIRCUIT(circ)->global_identifier);
- return -1;
- }
- if (circpad_negotiate_parse(&negotiate, cell->payload+RELAY_HEADER_SIZE,
- CELL_PAYLOAD_SIZE-RELAY_HEADER_SIZE) < 0) {
- log_fn(LOG_PROTOCOL_WARN, LD_CIRC,
- "Received malformed PADDING_NEGOTIATE cell; dropping.");
- return -1;
- }
- if (negotiate->command == CIRCPAD_COMMAND_STOP) {
- /* Free the machine corresponding to this machine type */
- if (free_circ_machineinfos_with_machine_num(circ,
- negotiate->machine_type)) {
- log_info(LD_CIRC, "Received STOP command for machine %u",
- negotiate->machine_type);
- goto done;
- }
- log_fn(LOG_PROTOCOL_WARN, LD_CIRC,
- "Received circuit padding stop command for unknown machine.");
- goto err;
- } else if (negotiate->command == CIRCPAD_COMMAND_START) {
- SMARTLIST_FOREACH_BEGIN(relay_padding_machines,
- const circpad_machine_spec_t *, m) {
- if (m->machine_num == negotiate->machine_type) {
- circpad_setup_machine_on_circ(circ, m);
- circpad_cell_event_nonpadding_received(circ);
- goto done;
- }
- } SMARTLIST_FOREACH_END(m);
- }
- err:
- retval = -1;
- done:
- circpad_padding_negotiated(circ, negotiate->machine_type,
- negotiate->command,
- (retval == 0) ? CIRCPAD_RESPONSE_OK : CIRCPAD_RESPONSE_ERR);
- circpad_negotiate_free(negotiate);
- return retval;
- }
- /**
- * Parse and react to a padding_negotiated cell.
- *
- * This is called at the origin upon receipt of the middle's response
- * to our choice of state machine.
- *
- * Returns -1 on error, 0 on success.
- */
- signed_error_t
- circpad_handle_padding_negotiated(circuit_t *circ, cell_t *cell,
- crypt_path_t *layer_hint)
- {
- circpad_negotiated_t *negotiated;
- if (!CIRCUIT_IS_ORIGIN(circ)) {
- log_fn(LOG_PROTOCOL_WARN, LD_CIRC,
- "Padding negotiated cell unsupported at non-origin.");
- return -1;
- }
- /* Verify this came from the expected hop */
- if (!circpad_padding_is_from_expected_hop(circ, layer_hint)) {
- log_fn(LOG_PROTOCOL_WARN, LD_CIRC,
- "Padding negotiated cell from wrong hop on circuit %u",
- TO_ORIGIN_CIRCUIT(circ)->global_identifier);
- return -1;
- }
- if (circpad_negotiated_parse(&negotiated, cell->payload+RELAY_HEADER_SIZE,
- CELL_PAYLOAD_SIZE-RELAY_HEADER_SIZE) < 0) {
- log_fn(LOG_PROTOCOL_WARN, LD_CIRC,
- "Received malformed PADDING_NEGOTIATED cell on circuit %u; "
- "dropping.", TO_ORIGIN_CIRCUIT(circ)->global_identifier);
- return -1;
- }
- if (negotiated->command == CIRCPAD_COMMAND_STOP) {
- log_info(LD_CIRC,
- "Received STOP command on PADDING_NEGOTIATED for circuit %u",
- TO_ORIGIN_CIRCUIT(circ)->global_identifier);
- /* There may not be a padding_info here if we shut down the
- * machine in circpad_shutdown_old_machines(). Or, if
- * circpad_add_matching_matchines() added a new machine,
- * there may be a padding_machine for a different machine num
- * than this response. */
- free_circ_machineinfos_with_machine_num(circ, negotiated->machine_type);
- } else if (negotiated->command == CIRCPAD_COMMAND_START &&
- negotiated->response == CIRCPAD_RESPONSE_ERR) {
- // This can happen due to consensus drift.. free the machines
- // and be sad
- free_circ_machineinfos_with_machine_num(circ, negotiated->machine_type);
- TO_ORIGIN_CIRCUIT(circ)->padding_negotiation_failed = 1;
- log_fn(LOG_PROTOCOL_WARN, LD_CIRC,
- "Middle node did not accept our padding request on circuit %u (%d)",
- TO_ORIGIN_CIRCUIT(circ)->global_identifier,
- circ->purpose);
- }
- circpad_negotiated_free(negotiated);
- return 0;
- }
- /** Free memory allocated by this machine spec. */
- STATIC void
- machine_spec_free_(circpad_machine_spec_t *m)
- {
- if (!m) return;
- tor_free(m->states);
- tor_free(m);
- }
- /** Free all memory allocated by the circuitpadding subsystem. */
- void
- circpad_free_all(void)
- {
- if (origin_padding_machines) {
- SMARTLIST_FOREACH_BEGIN(origin_padding_machines,
- circpad_machine_spec_t *, m) {
- machine_spec_free(m);
- } SMARTLIST_FOREACH_END(m);
- smartlist_free(origin_padding_machines);
- }
- if (relay_padding_machines) {
- SMARTLIST_FOREACH_BEGIN(relay_padding_machines,
- circpad_machine_spec_t *, m) {
- machine_spec_free(m);
- } SMARTLIST_FOREACH_END(m);
- smartlist_free(relay_padding_machines);
- }
- }
- /* Serialization */
- // TODO: Should we use keyword=value here? Are there helpers for that?
- #if 0
- static void
- circpad_state_serialize(const circpad_state_t *state,
- smartlist_t *chunks)
- {
- smartlist_add_asprintf(chunks, " %u", state->histogram[0]);
- for (int i = 1; i < state->histogram_len; i++) {
- smartlist_add_asprintf(chunks, ",%u",
- state->histogram[i]);
- }
- smartlist_add_asprintf(chunks, " 0x%x",
- state->transition_cancel_events);
- for (int i = 0; i < CIRCPAD_NUM_STATES; i++) {
- smartlist_add_asprintf(chunks, ",0x%x",
- state->transition_events[i]);
- }
- smartlist_add_asprintf(chunks, " %u %u",
- state->use_rtt_estimate,
- state->token_removal);
- }
- char *
- circpad_machine_spec_to_string(const circpad_machine_spec_t *machine)
- {
- smartlist_t *chunks = smartlist_new();
- char *out;
- (void)machine;
- circpad_state_serialize(&machine->start, chunks);
- circpad_state_serialize(&machine->gap, chunks);
- circpad_state_serialize(&machine->burst, chunks);
- out = smartlist_join_strings(chunks, "", 0, NULL);
- SMARTLIST_FOREACH(chunks, char *, cp, tor_free(cp));
- smartlist_free(chunks);
- return out;
- }
- // XXX: Writeme
- const circpad_machine_spec_t *
- circpad_string_to_machine(const char *str)
- {
- (void)str;
- return NULL;
- }
- #endif /* 0 */
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