Commit adb248b6 authored by David Goulet's avatar David Goulet 🐼 Committed by Nick Mathewson
Browse files

TROVE-2021-003: Check layer_hint before half-closed end and resolve cells 

This issue was reported by Jann Horn part of Google's Project Zero.

Jann's one-sentence summary: entry/middle relays can spoof RELAY_END cells on
half-closed streams, which can lead to stream confusion between OP and
exit.

Fixes #40389
parent d71bf986

changes/ticket40389

0 → 100644
+3 −0
Original line number Diff line number Diff line 
  o Major bugfixes (relay, TROVE):

    - Don't allow entry or middle relays to spoof RELAY_END or RELAY_RESOLVED

      cell on half-closed streams. Fixes bug 40389; bugfix on 0.3.5.1-alpha.

src/core/or/relay.c

+23 −2
Original line number Diff line number Diff line
@@ -1428,6 +1428,25 @@ connection_edge_process_relay_cell_not_open( 
//  return -1;

}



/**

 * Return true iff our decryption layer_hint is from the last hop

 * in a circuit.

 */

static bool

relay_crypt_from_last_hop(origin_circuit_t *circ, crypt_path_t *layer_hint)

{

  tor_assert(circ);

  tor_assert(layer_hint);

  tor_assert(circ->cpath);



  if (layer_hint != circ->cpath->prev) {

    log_fn(LOG_PROTOCOL_WARN, LD_CIRC,

           "Got unexpected relay data from intermediate hop");

    return false;

  }

  return true;

}



/** An incoming relay cell has arrived on circuit <b>circ</b>. If

 * <b>conn</b> is NULL this is a control cell, else <b>cell</b> is

 * destined for <b>conn</b>.
@@ -1616,7 +1635,8 @@ connection_edge_process_relay_cell(cell_t *cell, circuit_t *circ, 
      if (!conn) {

        if (CIRCUIT_IS_ORIGIN(circ)) {

          origin_circuit_t *ocirc = TO_ORIGIN_CIRCUIT(circ);

          if (connection_half_edge_is_valid_end(ocirc->half_streams,

          if (relay_crypt_from_last_hop(ocirc, layer_hint) &&

              connection_half_edge_is_valid_end(ocirc->half_streams,

                                                rh.stream_id)) {



            circuit_read_valid_data(ocirc, rh.length);
@@ -1918,7 +1938,8 @@ connection_edge_process_relay_cell(cell_t *cell, circuit_t *circ, 


      if (CIRCUIT_IS_ORIGIN(circ)) {

        origin_circuit_t *ocirc = TO_ORIGIN_CIRCUIT(circ);

        if (connection_half_edge_is_valid_resolved(ocirc->half_streams,

        if (relay_crypt_from_last_hop(ocirc, layer_hint) &&

            connection_half_edge_is_valid_resolved(ocirc->half_streams,

                                                    rh.stream_id)) {

          circuit_read_valid_data(ocirc, rh.length);

          log_info(domain,