test: Add unit tests for the DoS subsystem

Signed-off-by: David Goulet <dgoulet@torproject.org>

src/or/channel.c

@@ -3845,8 +3845,8 @@ channel_get_canonical_remote_descr(channel_t *chan)
  * supports this operation, and return 1.  Return 0 if the underlying transport
  * doesn't let us do this.
  */
-int
-channel_get_addr_if_possible(channel_t *chan, tor_addr_t *addr_out)
+MOCK_IMPL(int,
+channel_get_addr_if_possible,(channel_t *chan, tor_addr_t *addr_out))
 {
   tor_assert(chan);
   tor_assert(addr_out);

src/or/channel.h

@@ -550,7 +550,8 @@ MOCK_DECL(void, channel_dump_statistics, (channel_t *chan, int severity));
 void channel_dump_transport_statistics(channel_t *chan, int severity);
 const char * channel_get_actual_remote_descr(channel_t *chan);
 const char * channel_get_actual_remote_address(channel_t *chan);
-int channel_get_addr_if_possible(channel_t *chan, tor_addr_t *addr_out);
+MOCK_DECL(int, channel_get_addr_if_possible, (channel_t *chan,
+                                              tor_addr_t *addr_out));
 const char * channel_get_canonical_remote_descr(channel_t *chan);
 int channel_has_queued_writes(channel_t *chan);
 int channel_is_bad_for_new_circs(channel_t *chan);

src/test/include.am

@@ -87,6 +87,7 @@ src_test_test_SOURCES = \
 	src/test/test_controller.c \
 	src/test/test_controller_events.c \
 	src/test/test_crypto.c \
+	src/test/test_dos.c \
 	src/test/test_data.c \
 	src/test/test_dir.c \
 	src/test/test_dir_common.c \

src/test/test.c

@@ -1197,6 +1197,7 @@ struct testgroup_t testgroups[] = {
   { "control/", controller_tests },
   { "control/event/", controller_event_tests },
   { "crypto/", crypto_tests },
+  { "dos/", dos_tests },
   { "dir/", dir_tests },
   { "dir_handle_get/", dir_handle_get_tests },
   { "dir/md/", microdesc_tests },

src/test/test.h

@@ -190,6 +190,7 @@ extern struct testcase_t container_tests[];
 extern struct testcase_t controller_tests[];
 extern struct testcase_t controller_event_tests[];
 extern struct testcase_t crypto_tests[];
+extern struct testcase_t dos_tests[];
 extern struct testcase_t dir_tests[];
 extern struct testcase_t dir_handle_get_tests[];
 extern struct testcase_t entryconn_tests[];

src/test/test_dos.c

@@ -0,0 +1,248 @@
+/* Copyright (c) 2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#define DOS_PRIVATE
+#define TOR_CHANNEL_INTERNAL_
+#define CIRCUITLIST_PRIVATE
+
+#include "or.h"
+#include "dos.h"
+#include "circuitlist.h"
+#include "geoip.h"
+#include "channel.h"
+#include "test.h"
+#include "log_test_helpers.h"
+
+static unsigned int
+mock_enable_dos_protection(const networkstatus_t *ns)
+{
+  (void) ns;
+  return 1;
+}
+
+/** Test that the connection tracker of the DoS subsystem will block clients
+ *  who try to establish too many connections */
+static void
+test_dos_conn_creation(void *arg)
+{
+  (void) arg;
+
+  MOCK(get_param_cc_enabled, mock_enable_dos_protection);
+  MOCK(get_param_conn_enabled, mock_enable_dos_protection);
+
+  /* Initialize test data */
+  or_connection_t or_conn;
+  time_t now = 1281533250; /* 2010-08-11 13:27:30 UTC */
+  tt_int_op(AF_INET,OP_EQ, tor_addr_parse(&or_conn.real_addr,
+                                          "18.0.0.1"));
+  tor_addr_t *addr = &or_conn.real_addr;
+
+  /* Get DoS subsystem limits */
+  dos_init();
+  uint32_t max_concurrent_conns = get_param_conn_max_concurrent_count(NULL);
+
+  /* Introduce new client */
+  geoip_note_client_seen(GEOIP_CLIENT_CONNECT, addr, NULL, now);
+  { /* Register many conns from this client but not enough to get it blocked */
+    unsigned int i;
+    for (i = 0; i < max_concurrent_conns; i++) {
+      dos_new_client_conn(&or_conn);
+    }
+  }
+
+  /* Check that new conns are still permitted */
+  tt_int_op(DOS_CONN_DEFENSE_NONE, OP_EQ,
+            dos_conn_addr_get_defense_type(addr));
+
+  /* Register another conn and check that new conns are not allowed anymore */
+  dos_new_client_conn(&or_conn);
+  tt_int_op(DOS_CONN_DEFENSE_CLOSE, OP_EQ,
+            dos_conn_addr_get_defense_type(addr));
+
+  /* Close a client conn and see that a new conn will be permitted again */
+  dos_close_client_conn(&or_conn);
+  tt_int_op(DOS_CONN_DEFENSE_NONE, OP_EQ,
+            dos_conn_addr_get_defense_type(addr));
+
+  /* Register another conn and see that defense measures get reactivated */
+  dos_new_client_conn(&or_conn);
+  tt_int_op(DOS_CONN_DEFENSE_CLOSE, OP_EQ,
+            dos_conn_addr_get_defense_type(addr));
+
+ done:
+  dos_free_all();
+}
+
+/** Helper mock: Place a fake IP addr for this channel in <b>addr_out</b> */
+static int
+mock_channel_get_addr_if_possible(channel_t *chan, tor_addr_t *addr_out)
+{
+  (void)chan;
+  tt_int_op(AF_INET,OP_EQ, tor_addr_parse(addr_out, "18.0.0.1"));;
+  return 1;
+
+ done:
+  return 0;
+}
+
+/** Test that the circuit tracker of the DoS subsystem will block clients who
+ *  try to establish too many circuits. */
+static void
+test_dos_circuit_creation(void *arg)
+{
+  (void) arg;
+  unsigned int i;
+
+  MOCK(get_param_cc_enabled, mock_enable_dos_protection);
+  MOCK(get_param_conn_enabled, mock_enable_dos_protection);
+  MOCK(channel_get_addr_if_possible,
+       mock_channel_get_addr_if_possible);
+
+  /* Initialize channels/conns/circs that will be used */
+  channel_t *chan = tor_malloc_zero(sizeof(channel_t));
+  channel_init(chan);
+  chan->is_client = 1;
+
+  /* Initialize test data */
+  or_connection_t or_conn;
+  time_t now = 1281533250; /* 2010-08-11 13:27:30 UTC */
+  tt_int_op(AF_INET,OP_EQ, tor_addr_parse(&or_conn.real_addr,
+                                          "18.0.0.1"));
+  tor_addr_t *addr = &or_conn.real_addr;
+
+  /* Get DoS subsystem limits */
+  dos_init();
+  uint32_t max_circuit_count = get_param_cc_circuit_burst(NULL);
+  uint32_t min_conc_conns_for_cc =
+    get_param_cc_min_concurrent_connection(NULL);
+
+  /* Introduce new client and establish enough connections to activate the
+   * circuit counting subsystem */
+  geoip_note_client_seen(GEOIP_CLIENT_CONNECT, addr, NULL, now);
+  for (i = 0; i < min_conc_conns_for_cc ; i++) {
+    dos_new_client_conn(&or_conn);
+  }
+
+  /* Register new circuits for this client and conn, but not enough to get
+   * detected as dos */
+  for (i=0; i < max_circuit_count-1; i++) {
+    dos_cc_new_create_cell(chan);
+  }
+  /* see that we didn't get detected for dosing */
+  tt_int_op(DOS_CC_DEFENSE_NONE, OP_EQ, dos_cc_get_defense_type(chan));
+
+  /* Register another CREATE cell that will push us over the limit. Check that
+   * the cell gets refused. */
+  dos_cc_new_create_cell(chan);
+  tt_int_op(DOS_CC_DEFENSE_REFUSE_CELL, OP_EQ, dos_cc_get_defense_type(chan));
+
+  /* TODO: Wait a few seconds before sending the cell, and check that the
+     buckets got refilled properly. */
+  /* TODO: Actually send a Tor cell (instead of calling the DoS function) and
+   * check that it will get refused */
+
+ done:
+  tor_free(chan);
+  dos_free_all();
+}
+
+/** Test that the DoS subsystem properly refills the circuit token buckets. */
+static void
+test_dos_bucket_refill(void *arg)
+{
+  (void) arg;
+  int i;
+  /* For this test, this variable is set to the current circ count of the token
+   * bucket. */
+  uint32_t current_circ_count;
+
+  MOCK(get_param_cc_enabled, mock_enable_dos_protection);
+  MOCK(get_param_conn_enabled, mock_enable_dos_protection);
+  MOCK(channel_get_addr_if_possible,
+       mock_channel_get_addr_if_possible);
+
+  time_t now = 1281533250; /* 2010-08-11 13:27:30 UTC */
+  update_approx_time(now);
+
+  /* Initialize channels/conns/circs that will be used */
+  channel_t *chan = tor_malloc_zero(sizeof(channel_t));
+  channel_init(chan);
+  chan->is_client = 1;
+  or_connection_t or_conn;
+  tt_int_op(AF_INET,OP_EQ, tor_addr_parse(&or_conn.real_addr,
+                                          "18.0.0.1"));
+  tor_addr_t *addr = &or_conn.real_addr;
+
+  /* Initialize DoS subsystem and get relevant limits */
+  dos_init();
+  uint32_t max_circuit_count = get_param_cc_circuit_burst(NULL);
+  int circ_rate = tor_lround(get_circuit_rate_per_second());
+  /* Check that the circuit rate is a positive number and smaller than the max
+   * circuit count */
+  tt_int_op(circ_rate, OP_GT, 1);
+  tt_int_op(circ_rate, OP_LT, max_circuit_count);
+
+  /* Register this client */
+  geoip_note_client_seen(GEOIP_CLIENT_CONNECT, addr, NULL, now);
+  dos_new_client_conn(&or_conn);
+
+  /* Fetch this client from the geoip cache and get its DoS structs */
+  clientmap_entry_t *entry = geoip_lookup_client(addr, NULL,
+                                                 GEOIP_CLIENT_CONNECT);
+  tt_assert(entry);
+  dos_client_stats_t* dos_stats = &entry->dos_stats;
+  /* Check that the circuit bucket is still uninitialized */
+  tt_uint_op(dos_stats->cc_stats.circuit_bucket, OP_EQ, 0);
+
+  /* Send a create cell: then check that the circ token bucket got initialized
+   * and one circ was subtracted. */
+  dos_cc_new_create_cell(chan);
+  current_circ_count = max_circuit_count - 1;
+  tt_uint_op(dos_stats->cc_stats.circuit_bucket, OP_EQ, current_circ_count);
+
+  /* Now send 29 more CREATEs and ensure that the bucket is missing 30
+   * tokens */
+  for (i=0; i < 29; i++) {
+   dos_cc_new_create_cell(chan);
+   current_circ_count--;
+  }
+  tt_uint_op(dos_stats->cc_stats.circuit_bucket, OP_EQ, current_circ_count);
+
+  /* OK! Progress time forward one sec, refill the bucket and check that the
+   * refill happened correctly. */
+  now += 1;
+  update_approx_time(now);
+  cc_stats_refill_bucket(&dos_stats->cc_stats, addr);
+  /* check refill */
+  current_circ_count += circ_rate;
+  tt_uint_op(dos_stats->cc_stats.circuit_bucket, OP_EQ, current_circ_count);
+
+  /* Now send as many CREATE cells as needed to deplete our token bucket
+   * completely */
+  for (; current_circ_count != 0; current_circ_count--) {
+   dos_cc_new_create_cell(chan);
+  }
+  tt_uint_op(current_circ_count, OP_EQ, 0);
+  tt_uint_op(dos_stats->cc_stats.circuit_bucket, OP_EQ, current_circ_count);
+
+  /* Now progress time a week forward, and check that the token bucket does not
+   * have more than max_circs allowance, even tho we let it simmer for so
+   * long. */
+  now += 604800; /* a week */
+  update_approx_time(now);
+  cc_stats_refill_bucket(&dos_stats->cc_stats, addr);
+  current_circ_count += max_circuit_count;
+  tt_uint_op(dos_stats->cc_stats.circuit_bucket, OP_EQ, current_circ_count);
+
+ done:
+  tor_free(chan);
+  dos_free_all();
+}
+
+struct testcase_t dos_tests[] = {
+  { "conn_creation", test_dos_conn_creation, TT_FORK, NULL, NULL },
+  { "circuit_creation", test_dos_circuit_creation, TT_FORK, NULL, NULL },
+  { "bucket_refill", test_dos_bucket_refill, TT_FORK, NULL, NULL },
+  END_OF_TESTCASES
+};
+