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Merge branch 'bug28683_30173_29203_squashed'

Nick Mathewson 5 years ago
parent
commit
9ad2eb8f73

+ 12 - 0
changes/bugs28693+30173+29203

@@ -0,0 +1,12 @@
+  o Minor bugfixes (circuit padding):
+    - Add a torrc option to disable circuit padding. Fixes bug 28693; bugfix
+      on 0.4.0.1-alpha.
+  o Minor bugfixes (circuit padding):
+    - Provide consensus parameter to fully disable circuit padding, to be used
+      in emergency network overload situations. Fixes bug 30173; bugfix on
+      0.4.0.1-alpha.
+  o Minor bugfixes (circuit padding):
+    - Allow circuit padding machines to specify that they do not contribute
+      much overhead, and provide consensus flags and torrc options to force
+      clients to only use low overhead machines. Fixes bug 29203; bugfix on
+      0.4.0.1-alpha.

+ 14 - 0
doc/tor.1.txt

@@ -955,6 +955,20 @@ The following options are useful only for clients (that is, if
     this option. This option should be offered via the UI to mobile users
     for use where bandwidth may be expensive. (Default: 0)
 
+[[CircuitPadding]] **CircuitPadding** **0**|**1**::
+    If set to 0, Tor will not pad client circuits with additional cover
+    traffic. Only clients may set this option. This option should be offered
+    via the UI to mobile users for use where bandwidth may be expensive. If
+    set to 1, padding will be negotiated as per the consensus and relay
+    support (unlike ConnectionPadding, CircuitPadding cannot be force-enabled).
+    (Default: 1)
+
+[[ReducedCircuitPadding]] **ReducedCircuitPadding** **0**|**1**::
+    If set to 1, Tor will only use circuit padding algorithms that have low
+    overhead. Only clients may set this option. This option should be offered
+    via the UI to mobile users for use where bandwidth may be expensive.
+    (Default: 0)
+
 [[ExcludeNodes]] **ExcludeNodes** __node__,__node__,__...__::
     A list of identity fingerprints, country codes, and address
     patterns of nodes to avoid when building a circuit. Country codes are

+ 3 - 3
scripts/maint/practracker/exceptions.txt

@@ -29,12 +29,12 @@
 #
 # Remember: It is better to fix the problem than to add a new exception!
 
-problem file-size /src/app/config/config.c 8494
-problem include-count /src/app/config/config.c 87
+problem file-size /src/app/config/config.c 8510
+problem include-count /src/app/config/config.c 88
 problem function-size /src/app/config/config.c:options_act_reversible() 296
 problem function-size /src/app/config/config.c:options_act() 588
 problem function-size /src/app/config/config.c:resolve_my_address() 192
-problem function-size /src/app/config/config.c:options_validate() 1209
+problem function-size /src/app/config/config.c:options_validate() 1220
 problem function-size /src/app/config/config.c:options_init_from_torrc() 202
 problem function-size /src/app/config/config.c:options_init_from_string() 173
 problem function-size /src/app/config/config.c:options_init_logs() 146

+ 10 - 0
src/app/config/config.c

@@ -597,6 +597,8 @@ static config_var_t option_vars_[] = {
   V(ReducedConnectionPadding,    BOOL,     "0"),
   V(ConnectionPadding,           AUTOBOOL, "auto"),
   V(RefuseUnknownExits,          AUTOBOOL, "auto"),
+  V(CircuitPadding,              BOOL,     "1"),
+  V(ReducedCircuitPadding,       BOOL,     "0"),
   V(RejectPlaintextPorts,        CSV,      ""),
   V(RelayBandwidthBurst,         MEMUNIT,  "0"),
   V(RelayBandwidthRate,          MEMUNIT,  "0"),
@@ -3744,6 +3746,14 @@ options_validate(or_options_t *old_options, or_options_t *options,
     REJECT("Relays cannot set ReducedConnectionPadding. ");
   }
 
+  if (server_mode(options) && options->CircuitPadding == 0) {
+    REJECT("Relays cannot set CircuitPadding to 0. ");
+  }
+
+  if (server_mode(options) && options->ReducedCircuitPadding == 1) {
+    REJECT("Relays cannot set ReducedCircuitPadding. ");
+  }
+
   if (options->BridgeDistribution) {
     if (!options->BridgeRelay) {
       REJECT("You set BridgeDistribution, but you didn't set BridgeRelay!");

+ 11 - 0
src/app/config/or_options_st.h

@@ -248,6 +248,17 @@ struct or_options_t {
    * pad to the server regardless of server support. */
   int ConnectionPadding;
 
+  /** Boolean: if true, then circuit padding will be negotiated by client
+   * and server, subject to consenus limits (default). If 0, it will be fully
+   * disabled. */
+  int CircuitPadding;
+
+  /** Boolean: if true, then this client will only use circuit padding
+   * algorithms that are known to use a low amount of overhead. If false,
+   * we will use all available circuit padding algorithms.
+   */
+  int ReducedCircuitPadding;
+
   /** To what authority types do we publish our descriptor? Choices are
    * "v1", "v2", "v3", "bridge", or "". */
   struct smartlist_t *PublishServerDescriptor;

+ 57 - 2
src/core/or/circuitpadding.c

@@ -81,6 +81,8 @@ static void circpad_setup_machine_on_circ(circuit_t *on_circ,
 static double circpad_distribution_sample(circpad_distribution_t dist);
 
 /** 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;
@@ -1081,6 +1083,14 @@ circpad_send_padding_callback(tor_timer_t *timer, void *args,
 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);
@@ -1094,6 +1104,24 @@ circpad_new_consensus_params(const networkstatus_t *ns)
          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.
@@ -1115,7 +1143,7 @@ circpad_machine_reached_padding_limit(circpad_machine_runtime_t *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 &&
+  if (machine->max_padding_percent &&
       mi->padding_sent >= machine->allowed_padding_count) {
     uint32_t total_cells = mi->padding_sent + mi->nonpadding_sent;
 
@@ -1162,6 +1190,18 @@ circpad_machine_schedule_padding,(circpad_machine_runtime_t *mi))
   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.");
@@ -1182,7 +1222,8 @@ circpad_machine_schedule_padding,(circpad_machine_runtime_t *mi))
            "Padding machine has reached padding limit on circuit %u",
              TO_ORIGIN_CIRCUIT(mi->on_circ)->global_identifier);
     } else {
-      log_fn(LOG_INFO, LD_CIRC,
+      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,
@@ -1621,6 +1662,19 @@ 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;
@@ -2166,6 +2220,7 @@ circpad_circ_client_machine_init(void)
   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;

+ 11 - 0
src/core/or/circuitpadding.h

@@ -152,6 +152,17 @@ typedef struct circpad_machine_conditions_t {
   /** Only apply the machine *if* vanguards are enabled */
   unsigned requires_vanguards : 1;
 
+  /**
+   * This machine is ok to use if reduced padding is set in consensus
+   * or torrc. This machine will still be applied even if reduced padding
+   * is not set; this flag only acts to exclude machines that don't have
+   * it set when reduced padding is requested. Therefore, reduced padding
+   * machines should appear at the lowest priority in the padding machine
+   * lists (aka first in the list), so that non-reduced padding machines
+   * for the same purpose are given a chance to apply when reduced padding
+   * is not requested. */
+  unsigned reduced_padding_ok : 1;
+
   /** Only apply the machine *if* the circuit's state matches any of
    *  the bits set in this bitmask. */
   circpad_circuit_state_t state_mask;

+ 155 - 2
src/test/test_circuitpadding.c

@@ -1685,8 +1685,11 @@ static void
 helper_create_conditional_machines(void)
 {
   circpad_machine_spec_t *add = helper_create_conditional_machine();
-  origin_padding_machines = smartlist_new();
-  relay_padding_machines = smartlist_new();
+
+  if (!origin_padding_machines)
+    origin_padding_machines = smartlist_new();
+  if (!relay_padding_machines)
+    relay_padding_machines = smartlist_new();
 
   add->machine_num = 2;
   add->is_origin_side = 1;
@@ -2398,6 +2401,155 @@ test_circuitpadding_global_rate_limiting(void *arg)
   smartlist_free(vote1.net_params);
 }
 
+/* Test reduced and disabled padding */
+static void
+test_circuitpadding_reduce_disable(void *arg)
+{
+  (void) arg;
+  int64_t actual_mocked_monotime_start;
+
+  MOCK(circuitmux_attach_circuit, circuitmux_attach_circuit_mock);
+
+  nodes_init();
+  dummy_channel.cmux = circuitmux_alloc();
+  relay_side = (circuit_t *)new_fake_orcirc(&dummy_channel,
+                                            &dummy_channel);
+  client_side = (circuit_t *)origin_circuit_new();
+  relay_side->purpose = CIRCUIT_PURPOSE_OR;
+  client_side->purpose = CIRCUIT_PURPOSE_C_GENERAL;
+
+  circpad_machines_init();
+  helper_create_conditional_machines();
+
+  monotime_init();
+  monotime_enable_test_mocking();
+  actual_mocked_monotime_start = MONOTIME_MOCK_START;
+  monotime_set_mock_time_nsec(actual_mocked_monotime_start);
+  monotime_coarse_set_mock_time_nsec(actual_mocked_monotime_start);
+  curr_mocked_time = actual_mocked_monotime_start;
+  timers_initialize();
+
+  /* This is needed so that we are not considered to be dormant */
+  note_user_activity(20);
+
+  MOCK(circuit_package_relay_cell,
+       circuit_package_relay_cell_mock);
+  MOCK(node_get_by_id,
+       node_get_by_id_mock);
+
+  /* Simulate extend. This should result in the original machine getting
+   * added, since the circuit is not built */
+  simulate_single_hop_extend(client_side, relay_side, 1);
+  simulate_single_hop_extend(client_side, relay_side, 1);
+
+  /* Verify that machine #2 is added */
+  tt_int_op(client_side->padding_machine[0]->machine_num, OP_EQ, 2);
+  tt_int_op(relay_side->padding_machine[0]->machine_num, OP_EQ, 2);
+
+  /* Deliver a padding cell to the client, to trigger burst state */
+  circpad_cell_event_padding_sent(client_side);
+
+  /* This should have trigger length shutdown condition on client.. */
+  tt_ptr_op(client_side->padding_info[0], OP_EQ, NULL);
+  tt_ptr_op(client_side->padding_machine[0], OP_EQ, NULL);
+
+  /* Verify machine is gone from both sides */
+  tt_ptr_op(relay_side->padding_info[0], OP_EQ, NULL);
+  tt_ptr_op(relay_side->padding_machine[0], OP_EQ, NULL);
+
+  /* Now test the reduced padding machine by setting up the consensus */
+  networkstatus_t vote1;
+  vote1.net_params = smartlist_new();
+  smartlist_split_string(vote1.net_params,
+         "circpad_padding_reduced=1", NULL, 0, 0);
+
+  /* Register reduced padding machine with the padding subsystem */
+  circpad_new_consensus_params(&vote1);
+
+  simulate_single_hop_extend(client_side, relay_side, 1);
+
+  /* Verify that machine #0 is added */
+  tt_int_op(client_side->padding_machine[0]->machine_num, OP_EQ, 0);
+  tt_int_op(relay_side->padding_machine[0]->machine_num, OP_EQ, 0);
+
+  tt_int_op(
+    circpad_machine_reached_padding_limit(client_side->padding_info[0]),
+    OP_EQ, 0);
+  tt_int_op(
+    circpad_machine_reached_padding_limit(relay_side->padding_info[0]),
+    OP_EQ, 0);
+
+  /* Test that machines get torn down when padding is disabled */
+  SMARTLIST_FOREACH(vote1.net_params, char *, cp, tor_free(cp));
+  smartlist_free(vote1.net_params);
+  vote1.net_params = smartlist_new();
+  smartlist_split_string(vote1.net_params,
+         "circpad_padding_disabled=1", NULL, 0, 0);
+
+  /* Register reduced padding machine with the padding subsystem */
+  circpad_new_consensus_params(&vote1);
+
+  tt_int_op(
+    circpad_machine_schedule_padding(client_side->padding_info[0]),
+    OP_EQ, CIRCPAD_STATE_UNCHANGED);
+  tt_int_op(
+    circpad_machine_schedule_padding(relay_side->padding_info[0]),
+    OP_EQ, CIRCPAD_STATE_UNCHANGED);
+
+  /* Signal that circuit is built: this event causes us to re-evaluate
+   * machine conditions (which don't apply because padding is disabled). */
+  circpad_machine_event_circ_built(TO_ORIGIN_CIRCUIT(client_side));
+
+  tt_ptr_op(client_side->padding_info[0], OP_EQ, NULL);
+  tt_ptr_op(client_side->padding_machine[0], OP_EQ, NULL);
+  tt_ptr_op(relay_side->padding_info[0], OP_EQ, NULL);
+  tt_ptr_op(relay_side->padding_machine[0], OP_EQ, NULL);
+
+  SMARTLIST_FOREACH(vote1.net_params, char *, cp, tor_free(cp));
+  smartlist_free(vote1.net_params);
+  vote1.net_params = NULL;
+  circpad_new_consensus_params(&vote1);
+
+  get_options_mutable()->ReducedCircuitPadding = 1;
+
+  simulate_single_hop_extend(client_side, relay_side, 1);
+
+  /* Verify that machine #0 is added */
+  tt_int_op(client_side->padding_machine[0]->machine_num, OP_EQ, 0);
+  tt_int_op(relay_side->padding_machine[0]->machine_num, OP_EQ, 0);
+
+  tt_int_op(
+    circpad_machine_reached_padding_limit(client_side->padding_info[0]),
+    OP_EQ, 0);
+  tt_int_op(
+    circpad_machine_reached_padding_limit(relay_side->padding_info[0]),
+    OP_EQ, 0);
+
+  get_options_mutable()->CircuitPadding = 0;
+
+  tt_int_op(
+    circpad_machine_schedule_padding(client_side->padding_info[0]),
+    OP_EQ, CIRCPAD_STATE_UNCHANGED);
+  tt_int_op(
+    circpad_machine_schedule_padding(relay_side->padding_info[0]),
+    OP_EQ, CIRCPAD_STATE_UNCHANGED);
+
+  /* Signal that circuit is built: this event causes us to re-evaluate
+   * machine conditions (which don't apply because padding is disabled). */
+
+  circpad_machine_event_circ_built(TO_ORIGIN_CIRCUIT(client_side));
+
+  tt_ptr_op(client_side->padding_info[0], OP_EQ, NULL);
+  tt_ptr_op(client_side->padding_machine[0], OP_EQ, NULL);
+  tt_ptr_op(relay_side->padding_info[0], OP_EQ, NULL);
+  tt_ptr_op(relay_side->padding_machine[0], OP_EQ, NULL);
+
+ done:
+  free_fake_orcirc(relay_side);
+  circuitmux_detach_all_circuits(dummy_channel.cmux, NULL);
+  circuitmux_free(dummy_channel.cmux);
+}
+
 #define TEST_CIRCUITPADDING(name, flags) \
     { #name, test_##name, (flags), NULL, NULL }
 
@@ -2412,6 +2564,7 @@ struct testcase_t circuitpadding_tests[] = {
   TEST_CIRCUITPADDING(circuitpadding_sample_distribution, TT_FORK),
   TEST_CIRCUITPADDING(circuitpadding_machine_rate_limiting, TT_FORK),
   TEST_CIRCUITPADDING(circuitpadding_global_rate_limiting, TT_FORK),
+  TEST_CIRCUITPADDING(circuitpadding_reduce_disable, TT_FORK),
   TEST_CIRCUITPADDING(circuitpadding_token_removal_lower, TT_FORK),
   TEST_CIRCUITPADDING(circuitpadding_token_removal_higher, TT_FORK),
   TEST_CIRCUITPADDING(circuitpadding_closest_token_removal, TT_FORK),

+ 1 - 0
src/test/test_options.c

@@ -430,6 +430,7 @@ get_options_test_data(const char *conf)
   // Being kinda lame and just fixing the immedate breakage for now..
   result->opt->ConnectionPadding = -1; // default must be "auto"
   result->opt->DormantClientTimeout = 1800; // must be over 600.
+  result->opt->CircuitPadding = 1; // default must be "1"
 
   rv = config_get_lines(conf, &cl, 1);
   tt_int_op(rv, OP_EQ, 0);