tor

commit 0f8195406e0a2a97a3167d4bb40484f4bd091289
parent 705fd37875c4acd61037da6a2680678ae128e4a4
Author: David Goulet <dgoulet@torproject.org>
Date:   Wed,  3 Feb 2021 08:51:36 -0500

Merge branch 'maint-0.3.5' into maint-0.4.3

Diffstat:
M
src/core/or/connection_edge.c
 | 
12
++++++++++++
M
src/feature/nodelist/nodelist.c
 | 
8
++++++--

2 files changed, 18 insertions(+), 2 deletions(-)
diff --git a/src/core/or/connection_edge.c b/src/core/or/connection_edge.c
@@ -4149,6 +4149,15 @@ my_exit_policy_rejects(const tor_addr_t *addr,
   return 0;
 }
 
+/** Return true iff the consensus allows network reentry. The default value is
+ * false if the parameter is not found. */
+static bool
+network_reentry_is_allowed(void)
+{
+  /* Default is false, re-entry is not allowed. */
+  return !!networkstatus_get_param(NULL, "allow-network-reentry", 0, 0, 1);
+}
+
 /** Connect to conn's specified addr and port. If it worked, conn
  * has now been added to the connection_array.
  *
@@ -4186,6 +4195,8 @@ connection_exit_connect(edge_connection_t *edge_conn)
    * infinite-length circuits (see "A Practical Congestion Attack on Tor Using
    * Long Paths", Usenix Security 2009). See also ticket 2667.
    *
+   * Skip this if the network reentry is allowed (known from the consensus).
+   *
    * The TORPROTOCOL reason is used instead of EXITPOLICY so client do NOT
    * attempt to retry connecting onto another circuit that will also fail
    * bringing considerable more load on the network if so.
@@ -4196,6 +4207,7 @@ connection_exit_connect(edge_connection_t *edge_conn)
    * reason that makes the client retry results in much worst consequences in
    * case of an attack so this is a small price to pay. */
   if (!connection_edge_is_rendezvous_stream(edge_conn) &&
+      !network_reentry_is_allowed() &&
       nodelist_reentry_probably_contains(&conn->addr, conn->port)) {
     log_info(LD_EXIT, "%s:%d tried to connect back to a known relay address. "
                       "Closing.", escaped_safe_str_client(conn->address),
diff --git a/src/feature/nodelist/nodelist.c b/src/feature/nodelist/nodelist.c
@@ -674,8 +674,12 @@ nodelist_set_consensus(networkstatus_t *ns)
   address_set_free(the_nodelist->node_addrs);
   addr_port_set_free(the_nodelist->reentry_set);
   the_nodelist->node_addrs = address_set_new(estimated_addresses);
-  /* Times two here is for both the ORPort and DirPort. */
-  the_nodelist->reentry_set = addr_port_set_new(estimated_addresses * 2);
+  /* Times two here is for both the ORPort and DirPort. We double it again in
+   * order to minimize as much as possible the false positive when looking up
+   * this set. Reason is that Exit streams that are legitimate but end up a
+   * false positive against this set will thus be considered reentry and be
+   * rejected which means a bad UX. */
+  the_nodelist->reentry_set = addr_port_set_new(estimated_addresses * 2 * 2);
 
   SMARTLIST_FOREACH_BEGIN(ns->routerstatus_list, routerstatus_t *, rs) {
     node_t *node = node_get_or_create(rs->identity_digest);