Avoid disclosing exit IP addresses in exit policies by default

From 0.2.7.2-alpha onwards, Exits would reject all the IP addresses
they knew about in their exit policy. But this may have disclosed
addresses that were otherwise unlisted.

Now, only advertised addresses are rejected by default by
ExitPolicyRejectPrivate. All known addresses are only rejected when
ExitPolicyRejectLocalInterfaces is explicitly set to 1.

1 files changed, 57 insertions, 21 deletions

diff --git a/src/or/policies.c b/src/or/policies.c
index 2703d7edef..544c6b7dbb 100644
--- a/src/or/policies.c
+++ b/src/or/policies.c
@@ -1843,10 +1843,18 @@ policies_log_first_redundant_entry(const smartlist_t *policy)
  *
  * If <b>ipv6_exit</b> is false, prepend "reject *6:*" to the policy.
  *
+ * If <b>configured_addresses</b> contains addresses:
+ *   - prepend entries that reject the addresses in this list. These may be the
+ *     advertised relay addresses and/or the outbound bind addresses,
+ *     depending on the ExitPolicyRejectPrivate and
+ *     ExitPolicyRejectLocalInterfaces settings.
  * If <b>rejectprivate</b> is true:
  *   - prepend "reject private:*" to the policy.
- *   - prepend entries that reject publicly routable addresses on this exit
- *     relay by calling policies_parse_exit_policy_reject_private
+ * If <b>reject_interface_addresses</b> is true:
+ *   - prepend entries that reject publicly routable interface addresses on
+ *     this exit relay by calling policies_parse_exit_policy_reject_private
+ * If <b>reject_configured_port_addresses</b> is true:
+ *   - prepend entries that reject all configured port addresses
  *
  * If cfg doesn't end in an absolute accept or reject and if
  * <b>add_default_policy</b> is true, add the default exit
@@ -1874,13 +1882,16 @@ policies_parse_exit_policy_internal(config_line_t *cfg,
   if (rejectprivate) {
     /* Reject IPv4 and IPv6 reserved private netblocks */
     append_exit_policy_string(dest, "reject private:*");
-    /* Reject IPv4 and IPv6 publicly routable addresses on this exit relay */
-    policies_parse_exit_policy_reject_private(
-                                            dest, ipv6_exit,
+  }
+
+  /* Consider rejecting IPv4 and IPv6 advertised relay addresses, outbound bind
+   * addresses, publicly routable addresses, and configured port addresses
+   * on this exit relay */
+  policies_parse_exit_policy_reject_private(dest, ipv6_exit,
                                             configured_addresses,
                                             reject_interface_addresses,
                                             reject_configured_port_addresses);
-  }
+
   if (parse_addr_policy(cfg, dest, -1))
     return -1;
 
@@ -1908,8 +1919,14 @@ policies_parse_exit_policy_internal(config_line_t *cfg,
  * If <b>EXIT_POLICY_REJECT_PRIVATE</b> bit is set in <b>options</b>:
  *   - prepend an entry that rejects all destinations in all netblocks
  *     reserved for private use.
+ *   - prepend entries that reject the advertised relay addresses in
+ *     configured_addresses
+ * If <b>EXIT_POLICY_REJECT_LOCAL_INTERFACES</b> bit is set in <b>options</b>:
  *   - prepend entries that reject publicly routable addresses on this exit
  *     relay by calling policies_parse_exit_policy_internal
+ *   - prepend entries that reject the outbound bind addresses in
+ *     configured_addresses
+ *   - prepend entries that reject all configured port addresses
  *
  * If <b>EXIT_POLICY_ADD_DEFAULT</b> bit is set in <b>options</b>, append
  * default exit policy entries to <b>result</b> smartlist.
@@ -1922,12 +1939,14 @@ policies_parse_exit_policy(config_line_t *cfg, smartlist_t **dest,
   int ipv6_enabled = (options & EXIT_POLICY_IPV6_ENABLED) ? 1 : 0;
   int reject_private = (options & EXIT_POLICY_REJECT_PRIVATE) ? 1 : 0;
   int add_default = (options & EXIT_POLICY_ADD_DEFAULT) ? 1 : 0;
+  int reject_local_interfaces = (options &
+                                 EXIT_POLICY_REJECT_LOCAL_INTERFACES) ? 1 : 0;
 
   return policies_parse_exit_policy_internal(cfg,dest,ipv6_enabled,
                                              reject_private,
                                              configured_addresses,
-                                             reject_private,
-                                             reject_private,
+                                             reject_local_interfaces,
+                                             reject_local_interfaces,
                                              add_default);
 }
 
@@ -1993,6 +2012,7 @@ policies_copy_outbound_addresses_to_smartlist(smartlist_t *addr_list,
  *    add it to the list of configured addresses.
  *  - if ipv6_local_address is non-NULL, and not the null tor_addr_t, add it
  *    to the list of configured addresses.
+ * If <b>or_options->ExitPolicyRejectLocalInterfaces</b> is true:
  *  - if or_options->OutboundBindAddressIPv4_ is not the null tor_addr_t, add
  *    it to the list of configured addresses.
  *  - if or_options->OutboundBindAddressIPv6_ is not the null tor_addr_t, add
@@ -2036,11 +2056,20 @@ policies_parse_exit_policy_from_options(const or_options_t *or_options,
     parser_cfg |= EXIT_POLICY_ADD_DEFAULT;
   }
 
+  if (or_options->ExitPolicyRejectLocalInterfaces) {
+    parser_cfg |= EXIT_POLICY_REJECT_LOCAL_INTERFACES;
+  }
+
   /* Copy the configured addresses into the tor_addr_t* list */
-  policies_copy_ipv4h_to_smartlist(configured_addresses, local_address);
-  policies_copy_addr_to_smartlist(configured_addresses, ipv6_local_address);
-  policies_copy_outbound_addresses_to_smartlist(configured_addresses,
-                                                or_options);
+  if (or_options->ExitPolicyRejectPrivate) {
+    policies_copy_ipv4h_to_smartlist(configured_addresses, local_address);
+    policies_copy_addr_to_smartlist(configured_addresses, ipv6_local_address);
+  }
+
+  if (or_options->ExitPolicyRejectLocalInterfaces) {
+    policies_copy_outbound_addresses_to_smartlist(configured_addresses,
+                                                  or_options);
+  }
 
   rv = policies_parse_exit_policy(or_options->ExitPolicy, result, parser_cfg,
                                   configured_addresses);
@@ -2820,7 +2849,8 @@ getinfo_helper_policies(control_connection_t *conn,
       return -1;
     }
 
-    if (!options->ExitPolicyRejectPrivate) {
+    if (!options->ExitPolicyRejectPrivate &&
+        !options->ExitPolicyRejectLocalInterfaces) {
       *answer = tor_strdup("");
       return 0;
     }
@@ -2829,16 +2859,22 @@ getinfo_helper_policies(control_connection_t *conn,
     smartlist_t *configured_addresses = smartlist_new();
 
     /* Copy the configured addresses into the tor_addr_t* list */
-    policies_copy_ipv4h_to_smartlist(configured_addresses, me->addr);
-    policies_copy_addr_to_smartlist(configured_addresses, &me->ipv6_addr);
-    policies_copy_outbound_addresses_to_smartlist(configured_addresses,
-                                                  options);
+    if (options->ExitPolicyRejectPrivate) {
+      policies_copy_ipv4h_to_smartlist(configured_addresses, me->addr);
+      policies_copy_addr_to_smartlist(configured_addresses, &me->ipv6_addr);
+    }
+
+    if (options->ExitPolicyRejectLocalInterfaces) {
+      policies_copy_outbound_addresses_to_smartlist(configured_addresses,
+                                                    options);
+    }
 
     policies_parse_exit_policy_reject_private(
-                                            &private_policy_list,
-                                            options->IPv6Exit,
-                                            configured_addresses,
-                                            1, 1);
+                                      &private_policy_list,
+                                      options->IPv6Exit,
+                                      configured_addresses,
+                                      options->ExitPolicyRejectLocalInterfaces,
+                                      options->ExitPolicyRejectLocalInterfaces);
     *answer = policy_dump_to_string(private_policy_list, 1, 1);
 
     addr_policy_list_free(private_policy_list);