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prop289: Add random bytes to the unused portion of the cell

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Signed-off-by: David Goulet <dgoulet@torproject.org>
This commit is contained in:
David Goulet 2019-02-19 15:02:11 -05:00
parent 402f0a4f5d
commit a6e012508e
1 changed files with 8 additions and 0 deletions
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8
src/core/or/relay.c
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@ -572,6 +572,14 @@ relay_send_command_from_edge_,(streamid_t stream_id, circuit_t *circ,
if (payload_len)
memcpy(cell.payload+RELAY_HEADER_SIZE, payload, payload_len);
/* Add random bytes to the unused portion of the payload, to foil attacks
* where the other side can predict all of the bytes in the payload and thus
* compute authenticated sendme cells without seeing the traffic. See
* proposal 289. */
crypto_fast_rng_getbytes(get_thread_fast_rng(),
cell.payload + RELAY_HEADER_SIZE + payload_len,
RELAY_PAYLOAD_SIZE - payload_len);
log_debug(LD_OR,"delivering %d cell %s.", relay_command,
cell_direction == CELL_DIRECTION_OUT ? "forward" : "backward");