Directory authorities now call routers stable if they have an

uptime of at least 30 days, even if that's not the median uptime
in the network. Implements proposal 1xx, suggested by Kevin Bauer
and Damon McCoy.


svn:r9788

ChangeLog

@@ -1,4 +1,10 @@
 Changes in version 0.2.0.1-alpha - 2007-??-??
+  o Security fixes:
+    - Directory authorities now call routers stable if they have an
+      uptime of at least 30 days, even if that's not the median uptime
+      in the network. Implements proposal 1xx, suggested by Kevin Bauer
+      and Damon McCoy.
+
   o Minor features (build):
     - Make autoconf search for libevent and openssl consistently.
     - Update deprecated macros in configure.in

doc/spec/dir-spec.txt

@@ -441,10 +441,12 @@ $Id$
    "Running" -- A router is 'Running' if the authority managed to connect to
    it successfully within the last 30 minutes.
 
-   "Stable" -- A router is 'Stable' if its uptime is above median for known
-   running, valid routers, and it's running a version of Tor not known to
-   drop circuits stupidly.  (0.1.1.10-alpha through 0.1.1.16-rc are stupid
-   this way.)
+   "Stable" -- A router is 'Stable' if it is running, valid, not
+   hibernating, and either its uptime is at least the median uptime for
+   known running, valid, non-hibernating routers, or its uptime is at
+   least 30 days. Routers are never called stable if they are running
+   a version of Tor known to drop circuits stupidly.  (0.1.1.10-alpha
+   through 0.1.1.16-rc are stupid this way.)
 
    "Fast" -- A router is 'Fast' if its bandwidth is in the top 7/8ths for
    known running, valid routers.

src/or/dirserv.c

@@ -1364,6 +1364,13 @@ should_generate_v2_networkstatus(void)
     the_v2_networkstatus_is_dirty + DIR_REGEN_SLACK_TIME < time(NULL);
 }
 
+/** If a router's uptime is at least this value, then it is always
+ * considered stable, regardless of the rest of the network. This
+ * way we resist attacks where an attacker doubles the size of the
+ * network using allegedly high-uptime nodes, displacing all the
+ * current guards. */
+#define UPTIME_TO_GUARANTEE_STABLE (3600*24*30)
+
 /* Thresholds for server performance: set by
  * dirserv_compute_performance_thresholds, and used by
  * generate_v2_networkstatus */
@@ -1395,9 +1402,12 @@ dirserv_thinks_router_is_unreliable(time_t now,
                                     routerinfo_t *router,
                                     int need_uptime, int need_capacity)
 {
-  if (need_uptime &&
-      (unsigned)real_uptime(router, now) < stable_uptime)
-    return 1;
+  if (need_uptime) {
+    int uptime = real_uptime(router, now);
+    if ((unsigned)uptime < stable_uptime &&
+        (unsigned)uptime < UPTIME_TO_GUARANTEE_STABLE)
+      return 1;
+  }
   if (need_capacity &&
       router_get_advertised_bandwidth(router) < fast_bandwidth)
     return 1;