Dir: when Tor's clock is behind, use a future consensus to bootstrap

When Tor's clock is behind the clocks on the authorities, allow Tor to
bootstrap successfully.

Fixes bug 28591; bugfix on 0.2.0.9-alpha.

6 files changed, 58 insertions, 26 deletions

diff --git a/changes/bug28591 b/changes/bug28591
new file mode 100644
index 0000000000..3a1c96ac16
--- /dev/null
+++ b/changes/bug28591
@@ -0,0 +1,4 @@
+  o Minor bugfixes (client, bootstrap):
+    - When Tor's clock is behind the clocks on the authorities, allow Tor to
+      bootstrap successfully. Fixes bug 28591; bugfix on 0.2.0.9-alpha.
+
diff --git a/src/feature/nodelist/microdesc.c b/src/feature/nodelist/microdesc.c
index 3f5085412f..8c5a9ee611 100644
--- a/src/feature/nodelist/microdesc.c
+++ b/src/feature/nodelist/microdesc.c
@@ -110,8 +110,9 @@ microdesc_note_outdated_dirserver(const char *relay_digest)
 
   /* If we have a reasonably live consensus, then most of our dirservers should
    * still be caching all the microdescriptors in it. Reasonably live
-   * consensuses are up to a day old. But microdescriptors expire 7 days after
-   * the last consensus that referenced them. */
+   * consensuses are up to a day old (or a day in the future). But
+   * microdescriptors expire 7 days after the last consensus that referenced
+   * them. */
   if (!networkstatus_get_reasonably_live_consensus(approx_time(),
                                                    FLAV_MICRODESC)) {
     return;
@@ -544,8 +545,8 @@ microdesc_cache_clean(microdesc_cache_t *cache, time_t cutoff, int force)
   size_t bytes_dropped = 0;
   time_t now = time(NULL);
 
-  /* If we don't know a live consensus, don't believe last_listed values: we
-   * might be starting up after being down for a while. */
+  /* If we don't know a reasonably live consensus, don't believe last_listed
+   * values: we might be starting up after being down for a while. */
   if (! force &&
       ! networkstatus_get_reasonably_live_consensus(now, FLAV_MICRODESC))
       return;
@@ -973,6 +974,7 @@ update_microdesc_downloads(time_t now)
   if (directory_too_idle_to_fetch_descriptors(options, now))
     return;
 
+  /* Give up if we don't have a reasonably live consensus. */
   consensus = networkstatus_get_reasonably_live_consensus(now, FLAV_MICRODESC);
   if (!consensus)
     return;
diff --git a/src/feature/nodelist/networkstatus.c b/src/feature/nodelist/networkstatus.c
index 51e720a984..a40c3dfb22 100644
--- a/src/feature/nodelist/networkstatus.c
+++ b/src/feature/nodelist/networkstatus.c
@@ -1377,7 +1377,7 @@ networkstatus_get_dl_status_by_flavor_running,(consensus_flavor_t flavor))
 }
 
 /** Return the most recent consensus that we have downloaded, or NULL if we
- * don't have one. */
+ * don't have one. May return future or expired consensuses. */
 MOCK_IMPL(networkstatus_t *,
 networkstatus_get_latest_consensus,(void))
 {
@@ -1388,7 +1388,7 @@ networkstatus_get_latest_consensus,(void))
 }
 
 /** Return the latest consensus we have whose flavor matches <b>f</b>, or NULL
- * if we don't have one. */
+ * if we don't have one. May return future or expired consensuses. */
 MOCK_IMPL(networkstatus_t *,
 networkstatus_get_latest_consensus_by_flavor,(consensus_flavor_t f))
 {
@@ -1422,10 +1422,11 @@ networkstatus_is_live(const networkstatus_t *ns, time_t now)
   return (ns->valid_after <= now && now <= ns->valid_until);
 }
 
-/** Determine if <b>consensus</b> is valid or expired recently enough that
- * we can still use it.
+/** Determine if <b>consensus</b> is valid, or expired recently enough, or not
+ * too far in the future, so that we can still use it.
  *
- * Return 1 if the consensus is reasonably live, or 0 if it is too old.
+ * Return 1 if the consensus is reasonably live, or 0 if it is too old or
+ * too new.
  */
 int
 networkstatus_consensus_reasonably_live(const networkstatus_t *consensus,
@@ -1434,29 +1435,42 @@ networkstatus_consensus_reasonably_live(const networkstatus_t *consensus,
   if (BUG(!consensus))
     return 0;
 
-  return networkstatus_valid_until_is_reasonably_live(consensus->valid_until,
+  return networkstatus_valid_after_is_reasonably_live(consensus->valid_after,
+                                                      now) &&
+         networkstatus_valid_until_is_reasonably_live(consensus->valid_until,
                                                       now);
 }
 
+#define REASONABLY_LIVE_TIME (24*60*60)
+
+/** As networkstatus_consensus_reasonably_live, but takes a valid_after
+ * time, and checks to see if it is in the past, or not too far in the future.
+ */
+int
+networkstatus_valid_after_is_reasonably_live(time_t valid_after,
+                                             time_t now)
+{
+  return (now >= valid_after - REASONABLY_LIVE_TIME);
+}
+
 /** As networkstatus_consensus_reasonably_live, but takes a valid_until
- * time rather than an entire consensus. */
+ * time, and checks to see if it is in the future, or not too far in the past.
+ */
 int
 networkstatus_valid_until_is_reasonably_live(time_t valid_until,
                                              time_t now)
 {
-#define REASONABLY_LIVE_TIME (24*60*60)
   return (now <= valid_until + REASONABLY_LIVE_TIME);
 }
 
 /** As networkstatus_get_live_consensus(), but is way more tolerant of expired
- * consensuses. */
+ *  and future consensuses. */
 MOCK_IMPL(networkstatus_t *,
 networkstatus_get_reasonably_live_consensus,(time_t now, int flavor))
 {
   networkstatus_t *consensus =
     networkstatus_get_latest_consensus_by_flavor(flavor);
   if (consensus &&
-      consensus->valid_after <= now &&
       networkstatus_consensus_reasonably_live(consensus, now))
     return consensus;
   else
@@ -2082,7 +2096,6 @@ networkstatus_set_current_consensus(const char *consensus,
 
     nodelist_set_consensus(c);
 
-    /* XXXXNM Microdescs: needs a non-ns variant. ???? NM*/
     update_consensus_networkstatus_fetch_time(now);
 
     /* Change the cell EWMA settings */
diff --git a/src/feature/nodelist/networkstatus.h b/src/feature/nodelist/networkstatus.h
index 7b1a0ff72f..6f1d15d532 100644
--- a/src/feature/nodelist/networkstatus.h
+++ b/src/feature/nodelist/networkstatus.h
@@ -87,6 +87,8 @@ MOCK_DECL(networkstatus_t *, networkstatus_get_live_consensus,(time_t now));
 int networkstatus_is_live(const networkstatus_t *ns, time_t now);
 int networkstatus_consensus_reasonably_live(const networkstatus_t *consensus,
                                             time_t now);
+int networkstatus_valid_after_is_reasonably_live(time_t valid_after,
+                                                 time_t now);
 int networkstatus_valid_until_is_reasonably_live(time_t valid_until,
                                                  time_t now);
 MOCK_DECL(networkstatus_t *,networkstatus_get_reasonably_live_consensus,
diff --git a/src/test/test_entrynodes.c b/src/test/test_entrynodes.c
index 52b87a84a8..348c642a23 100644
--- a/src/test/test_entrynodes.c
+++ b/src/test/test_entrynodes.c
@@ -127,6 +127,9 @@ big_fake_network_cleanup(const struct testcase_t *testcase, void *ptr)
   return 1; /* NOP */
 }
 
+#define REASONABLY_FUTURE " reasonably-future"
+#define REASONABLY_PAST " reasonably-past"
+
 /* Unittest setup function: Setup a fake network. */
 static void *
 big_fake_network_setup(const struct testcase_t *testcase)
@@ -138,9 +141,10 @@ big_fake_network_setup(const struct testcase_t *testcase)
   const int N_NODES = 271;
 
   const char *argument = testcase->setup_data;
-  int reasonably_live_consensus = 0;
+  int reasonably_future_consensus = 0, reasonably_past_consensus = 0;
   if (argument) {
-    reasonably_live_consensus = strstr(argument, "reasonably-live") != NULL;
+    reasonably_future_consensus = strstr(argument, REASONABLY_FUTURE) != NULL;
+    reasonably_past_consensus = strstr(argument, REASONABLY_PAST) != NULL;
   }
 
   big_fake_net_nodes = smartlist_new();
@@ -198,11 +202,15 @@ big_fake_network_setup(const struct testcase_t *testcase)
 
   dummy_state = tor_malloc_zero(sizeof(or_state_t));
   dummy_consensus = tor_malloc_zero(sizeof(networkstatus_t));
-  if (reasonably_live_consensus) {
-    /* Make the dummy consensus valid from 4 hours ago, but expired an hour
+  if (reasonably_future_consensus) {
+    /* Make the dummy consensus valid in 6 hours, and expiring in 7 hours. */
+    dummy_consensus->valid_after = approx_time() + 6*3600;
+    dummy_consensus->valid_until = approx_time() + 7*3600;
+  } else if (reasonably_past_consensus) {
+    /* Make the dummy consensus valid from 16 hours ago, but expired 12 hours
      * ago. */
-    dummy_consensus->valid_after = approx_time() - 4*3600;
-    dummy_consensus->valid_until = approx_time() - 3600;
+    dummy_consensus->valid_after = approx_time() - 16*3600;
+    dummy_consensus->valid_until = approx_time() - 12*3600;
   } else {
     /* Make the dummy consensus valid for an hour either side of now. */
     dummy_consensus->valid_after = approx_time() - 3600;
@@ -3035,13 +3043,17 @@ static const struct testcase_setup_t upgrade_circuits = {
 
 #define BFN_TEST(name) \
   EN_TEST_BASE(name, TT_FORK, &big_fake_network, NULL), \
-  { #name "_reasonably_live", test_entry_guard_ ## name, TT_FORK, \
-    &big_fake_network, (void*)("reasonably-live") }
+  { #name "_reasonably_future", test_entry_guard_ ## name, TT_FORK, \
+    &big_fake_network, (void*)(REASONABLY_FUTURE) }, \
+  { #name "_reasonably_past", test_entry_guard_ ## name, TT_FORK, \
+    &big_fake_network, (void*)(REASONABLY_PAST) }
 
 #define UPGRADE_TEST(name, arg) \
   EN_TEST_BASE(name, TT_FORK, &upgrade_circuits, arg), \
-  { #name "_reasonably_live", test_entry_guard_ ## name, TT_FORK, \
-    &upgrade_circuits, (void*)(arg " reasonably-live") }
+  { #name "_reasonably_future", test_entry_guard_ ## name, TT_FORK, \
+    &upgrade_circuits, (void*)(arg REASONABLY_FUTURE) }, \
+  { #name "_reasonably_past", test_entry_guard_ ## name, TT_FORK, \
+    &upgrade_circuits, (void*)(arg REASONABLY_PAST) }
 
 struct testcase_t entrynodes_tests[] = {
   NO_PREFIX_TEST(node_preferred_orport),
diff --git a/src/test/test_routerlist.c b/src/test/test_routerlist.c
index 67af2fd484..6ba4877b91 100644
--- a/src/test/test_routerlist.c
+++ b/src/test/test_routerlist.c
@@ -301,7 +301,6 @@ test_router_pick_directory_server_impl(void *arg)
   tt_assert(!networkstatus_consensus_is_bootstrapping(con_md->valid_until
                                                       + 24*60*60));
   /* These times are outside the test validity period */
-  tt_assert(networkstatus_consensus_is_bootstrapping(now));
   tt_assert(networkstatus_consensus_is_bootstrapping(now + 2*24*60*60));
   tt_assert(networkstatus_consensus_is_bootstrapping(now - 2*24*60*60));