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Detect bug 6252 (unexpected sendme cell)

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I only check on circuits, not streams, since bloating your stream
window past the initial circuit window can't help you much.

Also, I compare to CIRCWINDOW_START_MAX so we don't have surprising
races if we lower CIRCWINDOW_START for an experiment.
This commit is contained in:
Roger Dingledine 2012-06-28 14:00:01 -04:00
parent 9c5a118272
commit c32ec9c425
2 changed files with 22 additions and 0 deletions
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8
changes/bug6252 Normal file
View File

@ -0,0 +1,8 @@
o Security fixes:
- Tear down the circuit if we get an unexpected SENDME cell. Clients
could use this trick to make their circuits receive cells faster
than our flow control would have allowed, or to gum up the network,
or possibly to do targeted memory denial-of-service attacks on
entry nodes. Fixes bug 6252. Bugfix on the 54th commit on Tor --
from July 2002, before the release of Tor 0.0.0.

14
src/or/relay.c
View File

@ -1265,11 +1265,25 @@ connection_edge_process_relay_cell(cell_t *cell, circuit_t *circ,
case RELAY_COMMAND_SENDME:
if (!conn) {
if (layer_hint) {
if (layer_hint->package_window + CIRCWINDOW_INCREMENT >
CIRCWINDOW_START_MAX) {
log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
"Bug/attack: unexpected sendme cell from exit relay. "
"Closing circ.");
return -END_CIRC_REASON_TORPROTOCOL;
}
layer_hint->package_window += CIRCWINDOW_INCREMENT;
log_debug(LD_APP,"circ-level sendme at origin, packagewindow %d.",
layer_hint->package_window);
circuit_resume_edge_reading(circ, layer_hint);
} else {
if (circ->package_window + CIRCWINDOW_INCREMENT >
CIRCWINDOW_START_MAX) {
log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
"Bug/attack: unexpected sendme cell from client. "
"Closing circ.");
return -END_CIRC_REASON_TORPROTOCOL;
}
circ->package_window += CIRCWINDOW_INCREMENT;
log_debug(LD_APP,
"circ-level sendme at non-origin, packagewindow %d.",