Block multiple introductions on the same intro circuit.

This commit is contained in:
George Kadianakis 2015-04-01 14:33:09 +01:00 committed by Nick Mathewson
parent 2bcb596dcf
commit 8dba8a088d
3 changed files with 20 additions and 0 deletions

4
changes/bug15515 Normal file
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@ -0,0 +1,4 @@
o Minor features (DoS-resistance):
- Make it harder for attackers to overwhelm hidden services with
introductions, by blocking multiple introduction requests on the
same circuit. Resolves ticket #15515.

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@ -3157,6 +3157,9 @@ typedef struct or_circuit_t {
* to the specification? */
unsigned int remaining_relay_early_cells : 4;
/* We have already received an INTRODUCE1 cell on this circuit. */
unsigned int already_received_introduce1 : 1;
/** True iff this circuit was made with a CREATE_FAST cell. */
unsigned int is_first_hop : 1;

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@ -149,6 +149,19 @@ rend_mid_introduce(or_circuit_t *circ, const uint8_t *request,
goto err;
}
/* We have already done an introduction on this circuit but we just
received a request for another one. We block it since this might
be an attempt to DoS a hidden service (#15515). */
if (circ->already_received_introduce1) {
log_fn(LOG_PROTOCOL_WARN, LD_REND,
"Blocking multiple introductions on the same circuit. "
"Someone might be trying to attack a hidden service through "
"this relay.");
goto err;
}
circ->already_received_introduce1 = 1;
/* We could change this to MAX_HEX_NICKNAME_LEN now that 0.0.9.x is
* obsolete; however, there isn't much reason to do so, and we're going
* to revise this protocol anyway.