diff options
Diffstat (limited to 'src/core/or/circuitpadding.c')
| -rw-r--r-- | src/core/or/circuitpadding.c | 3101 |
1 files changed, 3101 insertions, 0 deletions
diff --git a/src/core/or/circuitpadding.c b/src/core/or/circuitpadding.c new file mode 100644 index 0000000000..43f4a31624 --- /dev/null +++ b/src/core/or/circuitpadding.c @@ -0,0 +1,3101 @@ +/* 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; + +#ifndef COCCI +/** 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 ; +#endif /* !defined(COCCI) */ + +/** + * 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_t 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_t 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_t 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_t 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_t 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_t 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 on this index */ + break; + } + } + } 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; + } + + IF_BUG_ONCE(on_circ->padding_machine[machine->machine_index] != NULL) { + return; + } + IF_BUG_ONCE(on_circ->padding_info[machine->machine_index] != NULL) { + return; + } + + /* 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 */ |