Netflow record collapsing defense.

This defense will cause Cisco, Juniper, Fortinet, and other routers operating
in the default configuration to collapse netflow records that would normally
be split due to the 15 second flow idle timeout.

Collapsing these records should greatly reduce the utility of default netflow
data for correlation attacks, since all client-side records should become 30
minute chunks of total bytes sent/received, rather than creating multiple
separate records for every webpage load/ssh command interaction/XMPP chat/whatever
else happens to be inactive for more than 15 seconds.

The defense adds consensus parameters to govern the range of timeout values
for sending padding packets, as well as for keeping connections open.

The defense only sends padding when connections are otherwise inactive, and it
does not pad connections used solely for directory traffic at all. By default
it also doesn't pad inter-relay connections.

Statistics on the total padding in the last 24 hours are exported to the
extra-info descriptors.

1 files changed, 22 insertions, 1 deletions

diff --git a/src/or/main.c b/src/or/main.c
index 5549f97998..ef4a1ffdd0 100644
--- a/src/or/main.c
+++ b/src/or/main.c
@@ -54,6 +54,7 @@
 #include "buffers.h"
 #include "channel.h"
 #include "channeltls.h"
+#include "channelpadding.h"
 #include "circuitbuild.h"
 #include "circuitlist.h"
 #include "circuituse.h"
@@ -176,7 +177,7 @@ static int signewnym_is_pending = 0;
 static unsigned newnym_epoch = 0;
 
 /** Smartlist of all open connections. */
-static smartlist_t *connection_array = NULL;
+STATIC smartlist_t *connection_array = NULL;
 /** List of connections that have been marked for close and need to be freed
  * and removed from connection_array. */
 static smartlist_t *closeable_connection_lst = NULL;
@@ -1119,6 +1120,8 @@ run_connection_housekeeping(int i, time_t now)
     memset(&cell,0,sizeof(cell_t));
     cell.command = CELL_PADDING;
     connection_or_write_cell_to_buf(&cell, or_conn);
+  } else {
+    channelpadding_decide_to_pad_channel(chan);
   }
 }
 
@@ -1184,6 +1187,7 @@ CALLBACK(check_dns_honesty);
 CALLBACK(write_bridge_ns);
 CALLBACK(check_fw_helper_app);
 CALLBACK(heartbeat);
+CALLBACK(reset_padding_counts);
 
 #undef CALLBACK
 
@@ -1215,6 +1219,7 @@ static periodic_event_item_t periodic_events[] = {
   CALLBACK(write_bridge_ns),
   CALLBACK(check_fw_helper_app),
   CALLBACK(heartbeat),
+  CALLBACK(reset_padding_counts),
   END_OF_PERIODIC_EVENTS
 };
 #undef CALLBACK
@@ -1724,6 +1729,17 @@ write_stats_file_callback(time_t now, const or_options_t *options)
  * Periodic callback: Write bridge statistics to disk if appropriate.
  */
 static int
+reset_padding_counts_callback(time_t now, const or_options_t *options)
+{
+  if (options->PaddingStatistics) {
+    rep_hist_prep_published_padding_counts(now);
+  }
+
+  rep_hist_reset_padding_counts();
+  return REPHIST_CELL_PADDING_COUNTS_INTERVAL;
+}
+
+static int
 record_bridge_stats_callback(time_t now, const or_options_t *options)
 {
   static int should_init_bridge_stats = 1;
@@ -2336,6 +2352,8 @@ do_main_loop(void)
   }
 
   handle_signals(1);
+  monotime_init();
+  timers_initialize();
 
   /* load the private keys, if we're supposed to have them, and set up the
    * TLS context. */
@@ -3196,6 +3214,9 @@ tor_cleanup(void)
       rep_hist_record_mtbf_data(now, 0);
     keypin_close_journal();
   }
+
+  timers_shutdown();
+
 #ifdef USE_DMALLOC
   dmalloc_log_stats();
 #endif