NEEDS REVIEW. Act on previous comment, and handle named servers differently: now, we allow multiple servers with the same name in the routerlist even if that name is reserved, but we check whether names are reserved when we try to look up routers by nickname. This is a minor security fix. This makes router_add_to_routerlist O(1). This is a backport candidate.

svn:r8433

ChangeLog

@@ -1,9 +1,14 @@
 Changes in version 0.1.2.2-alpha - 2006-??-??
 
+  o Security Fixes, minor
+    - If a client asked for a server by name, and we didn't have a
+      descriptor for a named server with that name, we might return an old
+      one.
+
   o Minor Bugfixes
     - Small performance improvements on parsing descriptors.
     - Major performance descriptor on inserting descriptors; change
-      algorithm from O(n^2) to O(n). [Mostly.]
+      algorithm from O(n^2) to O(n).
     - Make the common memory allocation path faster on machines where
       malloc(0) returns a pointer.
 

src/common/util.c

@@ -204,6 +204,13 @@ _tor_memdup(const void *mem, size_t len DMALLOC_PARAMS)
   return dup;
 }
 
+/** Helper for places that need to take a function pointer to the right
+ * spelling of "free()". */
+void
+_tor_free(void *mem) {
+  tor_free(mem);
+}
+
 /* =====
  * String manipulation
  * ===== */

src/common/util.h

@@ -75,6 +75,7 @@ char *_tor_strndup(const char *s, size_t n DMALLOC_PARAMS)
   ATTR_MALLOC ATTR_NONNULL((1));
 void *_tor_memdup(const void *mem, size_t len DMALLOC_PARAMS)
   ATTR_MALLOC ATTR_NONNULL((1));
+void _tor_free(void *mem);
 #ifdef USE_DMALLOC
 extern int dmalloc_free(const char *file, const int line, void *pnt,
                         const int func_id);

src/or/routerlist.c

@@ -55,9 +55,13 @@ static routerlist_t *routerlist = NULL;
  * about.  This list is kept sorted by published_on. */
 static smartlist_t *networkstatus_list = NULL;
 
-/** Global list of local_routerstatus_t for each router, known or unknown. */
+/** Global list of local_routerstatus_t for each router, known or unknown.
+ * Kept sorted by digest. */
 static smartlist_t *routerstatus_list = NULL;
 
+/** Map from lowercase nickname to digest of named server, if any. */
+static strmap_t *named_server_map = NULL;
+
 /** True iff any member of networkstatus_list has changed since the last time
  * we called routerstatus_list_update_from_networkstatus(). */
 static int networkstatus_list_has_changed = 0;
@@ -1014,6 +1018,7 @@ router_get_by_nickname(const char *nickname, int warn_if_unnamed)
   char digest[DIGEST_LEN];
   routerinfo_t *best_match=NULL;
   int n_matches = 0;
+  char *named_digest = NULL;
 
   tor_assert(nickname);
   if (!routerlist)
@@ -1027,16 +1032,17 @@ router_get_by_nickname(const char *nickname, int warn_if_unnamed)
   maybedigest = (strlen(nickname) == HEX_DIGEST_LEN) &&
     (base16_decode(digest,DIGEST_LEN,nickname,HEX_DIGEST_LEN) == 0);
 
+  if (named_server_map &&
+      (named_digest = strmap_get_lc(named_server_map, nickname))) {
+    return digestmap_get(routerlist->identity_map, named_digest);
+  }
+
   SMARTLIST_FOREACH(routerlist->routers, routerinfo_t *, router,
   {
     if (!strcasecmp(router->nickname, nickname)) {
-      if (router->is_named)
-        return router;
-      else {
-        ++n_matches;
-        if (n_matches <= 1 || router->is_running)
-          best_match = router;
-      }
+      ++n_matches;
+      if (n_matches <= 1 || router->is_running)
+        best_match = router;
     } else if (maybedigest &&
                !memcmp(digest, router->cache_info.identity_digest, DIGEST_LEN)
                ) {
@@ -1738,7 +1744,7 @@ router_add_to_routerlist(routerinfo_t *router, const char **msg,
     }
   }
 
-#if 1
+#if 0
   /* XXXX This block is slow, and could be smarter.  All it does is ensure
    * that if we have a named server called "Foo", we will never have another
    * server called "Foo."  router_get_by_nickname() already knows to prefer
@@ -3132,6 +3138,10 @@ routerstatus_list_update_from_networkstatus(time_t now)
    * is a conflict on that nickname, map the lc nickname to conflict.
    */
   name_map = strmap_new();
+  /* Clear the global map... */
+  if (named_server_map)
+    strmap_free(named_server_map, _tor_free);
+  named_server_map = strmap_new();
   memset(conflict, 0xff, sizeof(conflict));
   for (i = 0; i < n_statuses; ++i) {
     if (!networkstatus[i]->binds_names)
@@ -3145,11 +3155,14 @@ routerstatus_list_update_from_networkstatus(time_t now)
       warned = smartlist_string_isin(warned_conflicts, rs->nickname);
       if (!other_digest) {
         strmap_set_lc(name_map, rs->nickname, rs->identity_digest);
+        strmap_set_lc(named_server_map, rs->nickname,
+                      tor_memdup(rs->identity_digest, DIGEST_LEN));
         if (warned)
           smartlist_string_remove(warned_conflicts, rs->nickname);
       } else if (memcmp(other_digest, rs->identity_digest, DIGEST_LEN) &&
                  other_digest != conflict) {
         if (!warned) {
+          char *d;
           int should_warn = options->DirPort && options->AuthoritativeDir;
           char fp1[HEX_DIGEST_LEN+1];
           char fp2[HEX_DIGEST_LEN+1];
@@ -3160,6 +3173,8 @@ routerstatus_list_update_from_networkstatus(time_t now)
                  "($%s vs $%s)",
                  rs->nickname, fp1, fp2);
           strmap_set_lc(name_map, rs->nickname, conflict);
+          d = strmap_remove_lc(named_server_map, rs->nickname);
+          tor_free(d);
           smartlist_add(warned_conflicts, tor_strdup(rs->nickname));
         }
       } else {
@@ -3322,6 +3337,7 @@ routerstatus_list_update_from_networkstatus(time_t now)
   }
   SMARTLIST_FOREACH(routerstatus_list, local_routerstatus_t *, rs,
                     local_routerstatus_free(rs));
+
   smartlist_free(routerstatus_list);
   routerstatus_list = result;