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Block multiple introductions on the same intro circuit.
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changes/bug15515
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4
changes/bug15515
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@ -0,0 +1,4 @@
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o Minor features (DoS-resistance):
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- Make it harder for attackers to overwhelm hidden services with
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introductions, by blocking multiple introduction requests on the
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same circuit. Resolves ticket #15515.
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@ -3157,6 +3157,9 @@ typedef struct or_circuit_t {
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* to the specification? */
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unsigned int remaining_relay_early_cells : 4;
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/* We have already received an INTRODUCE1 cell on this circuit. */
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unsigned int already_received_introduce1 : 1;
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/** True iff this circuit was made with a CREATE_FAST cell. */
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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,
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goto err;
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}
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/* We have already done an introduction on this circuit but we just
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received a request for another one. We block it since this might
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be an attempt to DoS a hidden service (#15515). */
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if (circ->already_received_introduce1) {
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log_fn(LOG_PROTOCOL_WARN, LD_REND,
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"Blocking multiple introductions on the same circuit. "
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"Someone might be trying to attack a hidden service through "
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"this relay.");
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goto err;
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}
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circ->already_received_introduce1 = 1;
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/* We could change this to MAX_HEX_NICKNAME_LEN now that 0.0.9.x is
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* obsolete; however, there isn't much reason to do so, and we're going
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* to revise this protocol anyway.
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