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@@ -1824,8 +1824,6 @@ circpad_check_received_cell(cell_t *cell, circuit_t *circ,
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crypt_path_t *layer_hint,
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const relay_header_t *rh)
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{
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- unsigned domain = layer_hint?LD_APP:LD_EXIT;
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-
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/* First handle the padding commands, since we want to ignore any other
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* commands if this circuit is padding-specific. */
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switch (rh->command) {
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@@ -1842,10 +1840,30 @@ circpad_check_received_cell(cell_t *cell, circuit_t *circ,
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}
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/* If this is a padding circuit we don't need to parse any other commands
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- * than the padding ones. Just drop them to the floor. */
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+ * than the padding ones. Just drop them to the floor.
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+ *
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+ * Note: we deliberately do not call circuit_read_valid_data() here. The
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+ * vanguards addon (specifically the 'bandguards' component's dropped cell
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+ * detection) will thus close this circuit, as it would for any other
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+ * unexpected cell. However, default tor will *not* close the circuit.
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+ *
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+ * This is intentional. We are not yet certain that is it optimal to keep
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+ * padding circuits open in cases like these, rather than closing them.
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+ * We suspect that continuing to pad is optimal against a passive classifier,
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+ * but as soon as the adversary is active (even as a client adversary) this
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+ * might change.
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+ *
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+ * So as a way forward, we log the cell command and circuit number, to
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+ * help us enumerate the most common instances of this in testing with
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+ * vanguards, to see which are common enough to verify and handle
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+ * properly.
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+ * - Mike
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+ */
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if (circ->purpose == CIRCUIT_PURPOSE_C_CIRCUIT_PADDING) {
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- log_info(domain, "Ignored cell (%d) that arrived in padding circuit.",
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- rh->command);
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+ log_fn(LOG_PROTOCOL_WARN, LD_CIRC,
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+ "Ignored cell (%d) that arrived in padding circuit "
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+ " %u.", rh->command, CIRCUIT_IS_ORIGIN(circ) ?
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+ TO_ORIGIN_CIRCUIT(circ)->global_identifier : 0);
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return 0;
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}
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