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circpad: Machines MUST have strictly increasing histogram edges.

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Add a basic validation function for the histograms. It can be a building block
for the future
This commit is contained in:
George Kadianakis 2019-03-13 13:21:52 +02:00
parent 32c821c47b
commit cdaff26f91
3 changed files with 99 additions and 20 deletions
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96
src/core/or/circuitpadding.c
View File

@ -494,11 +494,12 @@ circpad_machine_sample_delay(circpad_machine_state_t *mi)
* function below samples from [bin_start, bin_end) */
bin_end = circpad_histogram_bin_to_usec(mi, curr_bin+1);
// Sample uniformly between histogram[i] to histogram[i+1]-1,
// but no need to sample if they are the same timeval (aka bin 0 or bin 1).
if (bin_end <= bin_start+1)
/* Bin edges are monotonically increasing so this is a bug. Handle it. */
if (BUG(bin_start > bin_end)) {
return bin_start;
else
}
/* Sample randomly from within the bin width */
return (circpad_delay_t)crypto_rand_uint64_range(bin_start, bin_end);
}
@ -2050,16 +2051,92 @@ circpad_setup_machine_on_circ(circuit_t *on_circ,
on_circ->padding_machine[machine->machine_index] = machine;
}
/* These padding machines are only used for tests pending #28634. */
#ifdef TOR_UNIT_TESTS
/** 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_GENERAL, "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_GENERAL, "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_GENERAL, "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. */
STATIC void
register_padding_machine(circpad_machine_spec_t *machine,
smartlist_t *machine_list)
{
if (!padding_machine_is_valid(machine)) {
log_warn(LD_GENERAL, "Machine #%u is invalid. Ignoring.",
machine->machine_num);
return;
}
if (machine_list) {
smartlist_add(machine_list, machine);
}
}
/* 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));
// XXX: Better conditions for merge.. Or disable this machine in
// merge?
circ_client_machine->conditions.min_hops = 2;
circ_client_machine->conditions.state_mask =
CIRCPAD_CIRC_BUILDING|CIRCPAD_CIRC_OPENED|CIRCPAD_CIRC_HAS_RELAY_EARLY;
@ -2091,7 +2168,6 @@ circpad_circ_client_machine_init(void)
circ_client_machine->states[CIRCPAD_STATE_BURST].token_removal =
CIRCPAD_TOKEN_REMOVAL_CLOSEST;
// FIXME: Tune this histogram
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;
@ -2105,7 +2181,7 @@ circpad_circ_client_machine_init(void)
circ_client_machine->states[CIRCPAD_STATE_BURST].histogram_total_tokens = 5;
circ_client_machine->machine_num = smartlist_len(origin_padding_machines);
smartlist_add(origin_padding_machines, circ_client_machine);
register_padding_machine(circ_client_machine, origin_padding_machines);
}
static void
@ -2205,7 +2281,7 @@ circpad_circ_responder_machine_init(void)
CIRCPAD_TOKEN_REMOVAL_CLOSEST_USEC;
circ_responder_machine->machine_num = smartlist_len(relay_padding_machines);
smartlist_add(relay_padding_machines, circ_responder_machine);
register_padding_machine(circ_responder_machine, relay_padding_machines);
}
#endif

6
src/core/or/circuitpadding.h
View File

@ -291,7 +291,7 @@ typedef struct circpad_state_t {
/** The histogram itself: an array of uint16s of tokens, whose
* widths are exponentially spaced, in microseconds.
*
* This array must have histogram_len elements that are (non-strictly)
* This array must have histogram_len elements that are strictly
* monotonically increasing. */
circpad_hist_token_t histogram[CIRCPAD_MAX_HISTOGRAM_LEN];
/* The histogram bin edges in usec.
@ -730,6 +730,10 @@ histogram_get_bin_upper_bound(const circpad_machine_state_t *mi,
#ifdef TOR_UNIT_TESTS
extern smartlist_t *origin_padding_machines;
extern smartlist_t *relay_padding_machines;
STATIC void
register_padding_machine(circpad_machine_spec_t *machine,
smartlist_t *machine_list);
#endif
#endif

15
src/test/test_circuitpadding.c
View File

@ -794,7 +794,7 @@ test_circuitpadding_closest_token_removal(void *arg)
tt_int_op(client_side->padding_info[0]->current_state, OP_EQ,
CIRCPAD_STATE_BURST);
circ_client_machine.states[CIRCPAD_STATE_BURST].histogram_edges[0] = 100;
circ_client_machine.states[CIRCPAD_STATE_BURST].histogram_edges[1] = 100;
circ_client_machine.states[CIRCPAD_STATE_BURST].histogram_edges[1] = 101;
circ_client_machine.states[CIRCPAD_STATE_BURST].histogram_edges[2] = 120;
mi->padding_scheduled_at_usec = current_time - 102;
mi->histogram[0] = 0;
@ -903,7 +903,7 @@ test_circuitpadding_closest_token_removal_usec(void *arg)
tt_int_op(client_side->padding_info[0]->current_state, OP_EQ,
CIRCPAD_STATE_BURST);
circ_client_machine.states[CIRCPAD_STATE_BURST].histogram_edges[0] = 100;
circ_client_machine.states[CIRCPAD_STATE_BURST].histogram_edges[1] = 100;
circ_client_machine.states[CIRCPAD_STATE_BURST].histogram_edges[1] = 101;
circ_client_machine.states[CIRCPAD_STATE_BURST].histogram_edges[2] = 120;
mi->padding_scheduled_at_usec = current_time - 102;
mi->histogram[0] = 0;
@ -1649,7 +1649,7 @@ helper_create_conditional_machine(void)
ret->states[CIRCPAD_STATE_BURST].histogram_len = 3;
ret->states[CIRCPAD_STATE_BURST].histogram_edges[0] = 0;
ret->states[CIRCPAD_STATE_BURST].histogram_edges[1] = 0;
ret->states[CIRCPAD_STATE_BURST].histogram_edges[1] = 1;
ret->states[CIRCPAD_STATE_BURST].histogram_edges[2] = 1000000;
ret->states[CIRCPAD_STATE_BURST].histogram[0] = 6;
@ -1686,8 +1686,7 @@ helper_create_conditional_machines(void)
add->conditions.state_mask = CIRCPAD_CIRC_BUILDING|
CIRCPAD_CIRC_NO_STREAMS|CIRCPAD_CIRC_HAS_RELAY_EARLY;
add->conditions.purpose_mask = CIRCPAD_PURPOSE_ALL;
smartlist_add(origin_padding_machines, add);
register_padding_machine(add, origin_padding_machines);
add = helper_create_conditional_machine();
add->machine_num = 3;
@ -1706,15 +1705,15 @@ helper_create_conditional_machines(void)
add->conditions.state_mask = CIRCPAD_CIRC_OPENED|
CIRCPAD_CIRC_STREAMS|CIRCPAD_CIRC_HAS_NO_RELAY_EARLY;
add->conditions.purpose_mask = CIRCPAD_PURPOSE_ALL;
smartlist_add(origin_padding_machines, add);
register_padding_machine(add, origin_padding_machines);
add = helper_create_conditional_machine();
add->machine_num = 2;
smartlist_add(relay_padding_machines, add);
register_padding_machine(add, relay_padding_machines);
add = helper_create_conditional_machine();
add->machine_num = 3;
smartlist_add(relay_padding_machines, add);
register_padding_machine(add, relay_padding_machines);
}
void