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@@ -58,7 +58,6 @@ static crypt_path_t *onion_next_hop_in_cpath(crypt_path_t *cpath);
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static int onion_extend_cpath(origin_circuit_t *circ);
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static int count_acceptable_nodes(smartlist_t *routers);
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static int onion_append_hop(crypt_path_t **head_ptr, extend_info_t *choice);
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-static int circuits_can_use_ntor(void);
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/** This function tries to get a channel to the specified endpoint,
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* and then calls command_setup_channel() to give it the right
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@@ -780,10 +779,13 @@ should_use_create_fast_for_circuit(origin_circuit_t *circ)
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tor_assert(circ->cpath);
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tor_assert(circ->cpath->extend_info);
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- if (!circ->cpath->extend_info->onion_key)
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- return 1; /* our hand is forced: only a create_fast will work. */
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+ if (!circuit_has_usable_onion_key(circ)) {
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+ /* We don't have ntor, and we don't have or can't use TAP,
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+ * so our hand is forced: only a create_fast will work. */
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+ return 1;
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+ }
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if (public_server_mode(options)) {
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- /* We're a server, and we know an onion key. We can choose.
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+ /* We're a server, and we have a usable onion key. We can choose.
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* Prefer to blend our circuit into the other circuits we are
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* creating on behalf of others. */
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return 0;
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@@ -808,28 +810,20 @@ circuit_timeout_want_to_count_circ(origin_circuit_t *circ)
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&& circ->build_state->desired_path_len == DEFAULT_ROUTE_LEN;
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}
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-/** Return true if the ntor handshake is enabled in the configuration, or if
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- * it's been set to "auto" in the configuration and it's enabled in the
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- * consensus. */
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-static int
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-circuits_can_use_ntor(void)
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-{
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- const or_options_t *options = get_options();
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- if (options->UseNTorHandshake != -1)
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- return options->UseNTorHandshake;
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- return networkstatus_get_param(NULL, "UseNTorHandshake", 0, 0, 1);
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-}
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-
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/** Decide whether to use a TAP or ntor handshake for connecting to <b>ei</b>
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* directly, and set *<b>cell_type_out</b> and *<b>handshake_type_out</b>
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- * accordingly. */
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+ * accordingly.
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+ * Note that TAP handshakes are only used for direct connections:
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+ * - from Tor2web to intro points not in the client's consensus, and
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+ * - from Single Onions to rend points not in the service's consensus.
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+ * This is checked in onion_populate_cpath. */
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static void
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circuit_pick_create_handshake(uint8_t *cell_type_out,
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uint16_t *handshake_type_out,
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const extend_info_t *ei)
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{
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- /* XXXX029 Remove support for deciding to use TAP. */
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- if (extend_info_supports_ntor(ei) && circuits_can_use_ntor()) {
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+ /* XXXX030 Remove support for deciding to use TAP. */
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+ if (extend_info_supports_ntor(ei)) {
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*cell_type_out = CELL_CREATE2;
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*handshake_type_out = ONION_HANDSHAKE_TYPE_NTOR;
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return;
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@@ -841,9 +835,13 @@ circuit_pick_create_handshake(uint8_t *cell_type_out,
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/** Decide whether to use a TAP or ntor handshake for connecting to <b>ei</b>
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* directly, and set *<b>handshake_type_out</b> accordingly. Decide whether,
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- * in extending through <b>node_prev</b> to do so, we should use an EXTEND2 or
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- * an EXTEND cell to do so, and set *<b>cell_type_out</b> and
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- * *<b>create_cell_type_out</b> accordingly. */
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+ * in extending through <b>node</b> to do so, we should use an EXTEND2 or an
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+ * EXTEND cell to do so, and set *<b>cell_type_out</b> and
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+ * *<b>create_cell_type_out</b> accordingly.
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+ * Note that TAP handshakes are only used for extend handshakes:
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+ * - from clients to intro points, and
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+ * - from hidden services to rend points.
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+ * This is checked in onion_populate_cpath. */
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static void
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circuit_pick_extend_handshake(uint8_t *cell_type_out,
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uint8_t *create_cell_type_out,
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@@ -854,18 +852,27 @@ circuit_pick_extend_handshake(uint8_t *cell_type_out,
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uint8_t t;
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circuit_pick_create_handshake(&t, handshake_type_out, ei);
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- /* XXXX029 Remove support for deciding to use TAP. */
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+ /* XXXX030 Remove support for deciding to use TAP. */
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+
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+ /* It is an error to extend if there is no previous node. */
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+ tor_assert_nonfatal(node_prev);
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+ /* It is an error for a node with a known version to be so old it does not
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+ * support ntor. */
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+ tor_assert_nonfatal(routerstatus_version_supports_ntor(node_prev->rs, 1));
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+
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+ /* Assume relays without tor versions or routerstatuses support ntor.
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+ * The authorities enforce ntor support, and assuming and failing is better
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+ * than allowing a malicious node to perform a protocol downgrade to TAP. */
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if (node_prev &&
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*handshake_type_out != ONION_HANDSHAKE_TYPE_TAP &&
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(node_has_curve25519_onion_key(node_prev) ||
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- (node_prev->rs &&
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- routerstatus_version_supports_ntor(node_prev->rs, 0)))) {
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- *cell_type_out = RELAY_COMMAND_EXTEND2;
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- *create_cell_type_out = CELL_CREATE2;
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- } else {
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- *cell_type_out = RELAY_COMMAND_EXTEND;
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- *create_cell_type_out = CELL_CREATE;
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- }
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+ (routerstatus_version_supports_ntor(node_prev->rs, 1)))) {
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+ *cell_type_out = RELAY_COMMAND_EXTEND2;
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+ *create_cell_type_out = CELL_CREATE2;
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+ } else {
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+ *cell_type_out = RELAY_COMMAND_EXTEND;
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+ *create_cell_type_out = CELL_CREATE;
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+ }
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}
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/** This is the backbone function for building circuits.
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@@ -2468,6 +2475,15 @@ extend_info_addr_is_allowed(const tor_addr_t *addr)
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return 0;
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}
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+/* Does ei have a valid TAP key? */
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+int
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+extend_info_supports_tap(const extend_info_t* ei)
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+{
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+ tor_assert(ei);
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+ /* Valid TAP keys are not NULL */
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+ return ei->onion_key != NULL;
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+}
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+
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/* Does ei have a valid ntor key? */
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int
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extend_info_supports_ntor(const extend_info_t* ei)
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@@ -2478,3 +2494,46 @@ extend_info_supports_ntor(const extend_info_t* ei)
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(const char*)ei->curve25519_onion_key.public_key,
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CURVE25519_PUBKEY_LEN);
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}
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+
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+/* Is circuit purpose allowed to use the deprecated TAP encryption protocol?
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+ * The hidden service protocol still uses TAP for some connections, because
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+ * ntor onion keys aren't included in HS descriptors or INTRODUCE cells. */
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+static int
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+circuit_purpose_can_use_tap_impl(uint8_t purpose)
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+{
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+ return (purpose == CIRCUIT_PURPOSE_S_CONNECT_REND ||
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+ purpose == CIRCUIT_PURPOSE_C_INTRODUCING);
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+}
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+
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+/* Is circ allowed to use the deprecated TAP encryption protocol?
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+ * The hidden service protocol still uses TAP for some connections, because
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+ * ntor onion keys aren't included in HS descriptors or INTRODUCE cells. */
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+int
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+circuit_can_use_tap(const origin_circuit_t *circ)
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+{
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+ tor_assert(circ);
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+ tor_assert(circ->cpath);
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+ tor_assert(circ->cpath->extend_info);
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+ return (circuit_purpose_can_use_tap_impl(circ->base_.purpose) &&
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+ extend_info_supports_tap(circ->cpath->extend_info));
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+}
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+
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+/* Does circ have an onion key which it's allowed to use? */
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+int
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+circuit_has_usable_onion_key(const origin_circuit_t *circ)
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+{
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+ tor_assert(circ);
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+ tor_assert(circ->cpath);
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+ tor_assert(circ->cpath->extend_info);
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+ return (extend_info_supports_ntor(circ->cpath->extend_info) ||
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+ circuit_can_use_tap(circ));
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+}
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+
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+/* Does ei have an onion key which it would prefer to use?
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+ * Currently, we prefer ntor keys*/
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+int
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+extend_info_has_preferred_onion_key(const extend_info_t* ei)
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+{
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+ tor_assert(ei);
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+ return extend_info_supports_ntor(ei);
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+}
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