commit 2ea2d6f30add2350adb29467d0f27203571388fc Author: Mike Perry mikeperry-git@torproject.org Date: Mon Aug 12 14:23:43 2019 -0500
Clarify comment for bug30942 and improve logline. --- src/core/or/circuitpadding.c | 28 +++++++++++++++++++++++----- 1 file changed, 23 insertions(+), 5 deletions(-)
diff --git a/src/core/or/circuitpadding.c b/src/core/or/circuitpadding.c index 9ccad8744..47870bcaa 100644 --- a/src/core/or/circuitpadding.c +++ b/src/core/or/circuitpadding.c @@ -1800,8 +1800,6 @@ circpad_check_received_cell(cell_t *cell, circuit_t *circ, crypt_path_t *layer_hint, const relay_header_t *rh) { - unsigned domain = layer_hint?LD_APP:LD_EXIT; - /* First handle the padding commands, since we want to ignore any other * commands if this circuit is padding-specific. */ switch (rh->command) { @@ -1818,10 +1816,30 @@ circpad_check_received_cell(cell_t *cell, circuit_t *circ, }
/* If this is a padding circuit we don't need to parse any other commands - * than the padding ones. Just drop them to the floor. */ + * than the padding ones. Just drop them to the floor. + * + * Note: we deliberately do not call circuit_read_valid_data() here. The + * vanguards addon (specifically the 'bandguards' component's dropped cell + * detection) will thus close this circuit, as it would for any other + * unexpected cell. However, default tor will *not* close the circuit. + * + * This is intentional. We are not yet certain that is it optimal to keep + * padding circuits open in cases like these, rather than closing them. + * We suspect that continuing to pad is optimal against a passive classifier, + * but as soon as the adversary is active (even as a client adversary) this + * might change. + * + * So as a way forward, we log the cell command and circuit number, to + * help us enumerate the most common instances of this in testing with + * vanguards, to see which are common enough to verify and handle + * properly. + * - Mike + */ if (circ->purpose == CIRCUIT_PURPOSE_C_CIRCUIT_PADDING) { - log_info(domain, "Ignored cell (%d) that arrived in padding circuit.", - rh->command); + log_fn(LOG_PROTOCOL_WARN, LD_CIRC, + "Ignored cell (%d) that arrived in padding circuit " + " %u.", rh->command, CIRCUIT_IS_ORIGIN(circ) ? + TO_ORIGIN_CIRCUIT(circ)->global_identifier : 0); return 0; }