Merge branch 'maint-0.2.6' into release-0.2.6

changes/bug11447

@@ -0,0 +1,5 @@
+  o Minor features (DoS-resistance):
+    - Decrease the amount of reattempts that a hidden service is
+      willing to perform when its rendezvous circuits fail. This
+      reduces the computational cost for hidden service under heavy
+      load. Resolves ticket #11447.

changes/bug15515

@@ -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.

src/or/or.h

@@ -3181,6 +3181,9 @@ 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;
 

src/or/rendmid.c

@@ -149,6 +149,20 @@ 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.");
+    circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_TORPROTOCOL);
+    return -1;
+  }
+
+  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.

src/or/rendservice.c

@@ -90,7 +90,7 @@ typedef struct rend_service_port_config_t {
 #define MAX_INTRO_CIRCS_PER_PERIOD 10
 /** How many times will a hidden service operator attempt to connect to
  * a requested rendezvous point before giving up? */
-#define MAX_REND_FAILURES 8
+#define MAX_REND_FAILURES 1
 /** How many seconds should we spend trying to connect to a requested
  * rendezvous point before giving up? */
 #define MAX_REND_TIMEOUT 30