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TROVE-2017-004: Fix assertion failure in relay_send_end_cell_from_edge_

This fixes an assertion failure in relay_send_end_cell_from_edge_() when an
origin circuit and a cpath_layer = NULL were passed.

A service rendezvous circuit could do such a thing when a malformed BEGIN cell
is received but shouldn't in the first place because the service needs to send
an END cell on the circuit for which it can not do without a cpath_layer.

Fixes #22493

Reported-by: Roger Dingledine <arma@torproject.org>
Signed-off-by: David Goulet <dgoulet@torproject.org>
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dgoulet-tor authored and nmathewson committed Jun 5, 2017
1 parent 68c3df6 commit 79b59a2dfcb68897ee89d98587d09e55f07e68d7
Showing with 19 additions and 7 deletions.
  1. +5 −0 changes/trove-2017-004
  2. +14 −7 src/or/connection_edge.c
@@ -0,0 +1,5 @@
o Major bugfixes (hidden service, relay):
- Fix an assertion failure when an hidden service handles a malformed
BEGIN cell. This bug resulted in the service crashing triggered by a
tor_assert(). Part of TROVE-2017-004. Fixes bug 22493; bugfix on
tor-0.3.0.1-alpha. Found by armadev.
@@ -3091,14 +3091,21 @@ connection_exit_begin_conn(cell_t *cell, circuit_t *circ)
char *address = NULL;
uint16_t port = 0;
or_circuit_t *or_circ = NULL;
origin_circuit_t *origin_circ = NULL;
crypt_path_t *layer_hint = NULL;
const or_options_t *options = get_options();
begin_cell_t bcell;
int rv;
uint8_t end_reason=0;

assert_circuit_ok(circ);
if (!CIRCUIT_IS_ORIGIN(circ))
if (!CIRCUIT_IS_ORIGIN(circ)) {
or_circ = TO_OR_CIRCUIT(circ);
} else {
tor_assert(circ->purpose == CIRCUIT_PURPOSE_S_REND_JOINED);
origin_circ = TO_ORIGIN_CIRCUIT(circ);
layer_hint = origin_circ->cpath->prev;
}

relay_header_unpack(&rh, cell->payload);
if (rh.length > RELAY_PAYLOAD_SIZE)
@@ -3123,7 +3130,7 @@ connection_exit_begin_conn(cell_t *cell, circuit_t *circ)
return -END_CIRC_REASON_TORPROTOCOL;
} else if (rv == -1) {
tor_free(bcell.address);
relay_send_end_cell_from_edge(rh.stream_id, circ, end_reason, NULL);
relay_send_end_cell_from_edge(rh.stream_id, circ, end_reason, layer_hint);
return 0;
}

@@ -3160,7 +3167,7 @@ connection_exit_begin_conn(cell_t *cell, circuit_t *circ)
if (!directory_permits_begindir_requests(options) ||
circ->purpose != CIRCUIT_PURPOSE_OR) {
relay_send_end_cell_from_edge(rh.stream_id, circ,
END_STREAM_REASON_NOTDIRECTORY, NULL);
END_STREAM_REASON_NOTDIRECTORY, layer_hint);
return 0;
}
/* Make sure to get the 'real' address of the previous hop: the
@@ -3177,7 +3184,7 @@ connection_exit_begin_conn(cell_t *cell, circuit_t *circ)
} else {
log_warn(LD_BUG, "Got an unexpected command %d", (int)rh.command);
relay_send_end_cell_from_edge(rh.stream_id, circ,
END_STREAM_REASON_INTERNAL, NULL);
END_STREAM_REASON_INTERNAL, layer_hint);
return 0;
}

@@ -3188,7 +3195,7 @@ connection_exit_begin_conn(cell_t *cell, circuit_t *circ)
if (bcell.flags & BEGIN_FLAG_IPV4_NOT_OK) {
tor_free(address);
relay_send_end_cell_from_edge(rh.stream_id, circ,
END_STREAM_REASON_EXITPOLICY, NULL);
END_STREAM_REASON_EXITPOLICY, layer_hint);
return 0;
}
}
@@ -3211,7 +3218,7 @@ connection_exit_begin_conn(cell_t *cell, circuit_t *circ)
n_stream->deliver_window = STREAMWINDOW_START;

if (circ->purpose == CIRCUIT_PURPOSE_S_REND_JOINED) {
origin_circuit_t *origin_circ = TO_ORIGIN_CIRCUIT(circ);
tor_assert(origin_circ);
log_info(LD_REND,"begin is for rendezvous. configuring stream.");
n_stream->base_.address = tor_strdup("(rendezvous)");
n_stream->base_.state = EXIT_CONN_STATE_CONNECTING;
@@ -3231,7 +3238,7 @@ connection_exit_begin_conn(cell_t *cell, circuit_t *circ)
* the hidden service. */
relay_send_end_cell_from_edge(rh.stream_id, circ,
END_STREAM_REASON_DONE,
origin_circ->cpath->prev);
layer_hint);
connection_free(TO_CONN(n_stream));
tor_free(address);

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