r17554@catbus: nickm | 2008-01-10 12:48:29 -0500

Do not send bridge descriptors over unencrypted connections.


svn:r13094

ChangeLog

@@ -54,6 +54,10 @@ Changes in version 0.2.0.16-alpha - 2008-01-??
     - Actually implement the -s option to tor-gencert.
     - Add a manual page for tor-gencert.
 
+  o Minor features (bridges):
+    - Bridge authorities no longer serve bridge descriptors over unencrypted
+      connections.
+
   o Minor features (other):
     - Add hidden services and DNSPorts to the list of things that make
       Tor accept that it has running ports.  Change starting Tor with

doc/TODO

@@ -28,7 +28,7 @@ RK- make it easier to set up a private tor network on your own computer
   - Make BEGIN_DIR mandatory for asking questions of bridge authorities?
     (but only for bridge descriptors. not for ordinary cache stuff.)
     o Implement connection_dir_is_encrypted().
-    - set up a filter to not answer any bridge descriptors on a
+    o set up a filter to not answer any bridge descriptors on a
       non-encrypted request
   o write a tor-gencert man page
 

src/or/directory.c

@@ -2421,7 +2421,8 @@ directory_handle_command_get(dir_connection_t *conn, const char *headers,
     url += is_extra ? strlen("/tor/extra/") : strlen("/tor/server/");
     conn->fingerprint_stack = smartlist_create();
     res = dirserv_get_routerdesc_fingerprints(conn->fingerprint_stack, url,
-                                              &msg);
+                                          &msg,
+                                          !connection_dir_is_encrypted(conn));
 
     if (!strcmpstart(url, "fp/")) {
       request_type = deflated?"/tor/server/fp.z":"/tor/server/fp";

src/or/dirserv.c

@@ -57,7 +57,9 @@ dirserv_get_status_impl(const char *fp, const char *nickname,
                         const char *platform, const char *contact,
                         const char **msg, int should_log);
 static void clear_cached_dir(cached_dir_t *d);
-
+static signed_descriptor_t *get_signed_descriptor_by_fp(const char *fp,
+                                                        int extrainfo,
+                                                        time_t publish_cutoff);
 static int dirserv_add_extrainfo(extrainfo_t *ei, const char **msg);
 
 /************** Fingerprint handling code ************/
@@ -2571,8 +2573,9 @@ dirserv_get_networkstatus_v2(smartlist_t *result,
  */
 int
 dirserv_get_routerdesc_fingerprints(smartlist_t *fps_out, const char *key,
-                                    const char **msg)
+                                    const char **msg, int for_unencrypted_conn)
 {
+  int by_id = 1;
   *msg = NULL;
 
   if (!strcmp(key, "all")) {
@@ -2586,6 +2589,7 @@ dirserv_get_routerdesc_fingerprints(smartlist_t *fps_out, const char *key,
       smartlist_add(fps_out,
                     tor_memdup(ri->cache_info.identity_digest, DIGEST_LEN));
   } else if (!strcmpstart(key, "d/")) {
+    by_id = 0;
     key += strlen("d/");
     dir_split_resource_into_fingerprints(key, fps_out, NULL, 1, 1);
   } else if (!strcmpstart(key, "fp/")) {
@@ -2596,6 +2600,19 @@ dirserv_get_routerdesc_fingerprints(smartlist_t *fps_out, const char *key,
     return -1;
   }
 
+  if (for_unencrypted_conn) {
+    /* Remove anything whose purpose isn't general. */
+    SMARTLIST_FOREACH(fps_out, char *, cp, {
+        signed_descriptor_t *sd =
+          by_id ? get_signed_descriptor_by_fp(cp,0,0) :
+                  router_get_by_descriptor_digest(cp);
+        if (sd && !sd->send_unencrypted) {
+          tor_free(cp);
+          SMARTLIST_DEL_CURRENT(fps_out, cp);
+        }
+      });
+  }
+
   if (!smartlist_len(fps_out)) {
     *msg = "Servers unavailable";
     return -1;
@@ -2618,8 +2635,8 @@ dirserv_get_routerdesc_fingerprints(smartlist_t *fps_out, const char *key,
  * If -1 is returned *<b>msg</b> will be set to an appropriate error
  * message.
  *
- * (Despite its name, this function is also called from the controller, which
+ * XXXX020 rename this function.  IT's only called from the controller.
- * exposes a similar means to fetch descriptors.)
+ * XXXX020 in fact, refactor this function, mergeing as much as possible.
  */
 int
 dirserv_get_routerdescs(smartlist_t *descs_out, const char *key,
@@ -2938,6 +2955,14 @@ connection_dirserv_add_servers_to_outbuf(dir_connection_t *conn)
     tor_free(fp);
     if (!sd)
       continue;
+    if (!connection_dir_is_encrypted(conn) && !sd->send_unencrypted) {
+      /* we did this check once before (so we could have an accurate size
+       * estimate and maybe send a 404 if somebody asked for only bridges on a
+       * connection), but we need to do it again in case a previously
+       * unknown bridge descriptor has shown up between then and now. */
+      continue;
+    }
+
     body = signed_descriptor_get_body(sd);
     if (conn->zlib_state) {
       int last = ! smartlist_len(conn->fingerprint_stack);

src/or/or.h

@@ -1245,6 +1245,8 @@ typedef struct signed_descriptor_t {
   /* If true, we got an extrainfo for this item, and the digest was right,
    * but it was incompatible. */
   unsigned int extrainfo_is_bogus : 1;
+  /* If true, we are willing to transmit this item unencrypted. */
+  unsigned int send_unencrypted : 1;
 } signed_descriptor_t;
 
 /** Information about another onion router in the network. */
@@ -3113,7 +3115,8 @@ void dirserv_get_networkstatus_v2(smartlist_t *result, const char *key);
 void dirserv_get_networkstatus_v2_fingerprints(smartlist_t *result,
                                                const char *key);
 int dirserv_get_routerdesc_fingerprints(smartlist_t *fps_out, const char *key,
-                                        const char **msg);
+                                        const char **msg,
+                                        int for_unencrypted_conn);
 int dirserv_get_routerdescs(smartlist_t *descs_out, const char *key,
                             const char **msg);
 void dirserv_orconn_tls_done(const char *address,

src/or/routerlist.c

@@ -4226,6 +4226,7 @@ routerinfo_incompatible_with_extrainfo(routerinfo_t *ri, extrainfo_t *ei,
       goto err; /* Bad signature, or no match. */
     }
 
+    ei->cache_info.send_unencrypted = ri->cache_info.send_unencrypted;
     tor_free(ei->pending_sig);
   }
 

src/or/routerparse.c

@@ -1172,6 +1172,8 @@ router_parse_entry_from_string(const char *s, const char *end,
   } else {
     router->purpose = ROUTER_PURPOSE_GENERAL;
   }
+  router->cache_info.send_unencrypted =
+    (router->purpose == ROUTER_PURPOSE_GENERAL) ? 1 : 0;
 
   if ((tok = find_first_by_keyword(tokens, K_UPTIME))) {
     tor_assert(tok->n_args >= 1);
@@ -1326,7 +1328,7 @@ extrainfo_parse_entry_from_string(const char *s, const char *end,
   smartlist_t *tokens = NULL;
   directory_token_t *tok;
   crypto_pk_env_t *key = NULL;
-  routerinfo_t *router;
+  routerinfo_t *router = NULL;
 
   if (!end) {
     end = s + strlen(s);
@@ -1405,6 +1407,9 @@ extrainfo_parse_entry_from_string(const char *s, const char *end,
     if (check_signature_token(digest, tok, key, 0, "extra-info") < 0)
       goto err;
 
+    if (router)
+      extrainfo->cache_info.send_unencrypted =
+        router->cache_info.send_unencrypted;
   } else {
     extrainfo->pending_sig = tor_memdup(tok->object_body,
                                         tok->object_size);