From c5b00c5a514a6b40e5245bc1fd78fe5490922739 Mon Sep 17 00:00:00 2001
From: David Goulet <dgoulet@torproject.org>
Date: Tue, 11 Jun 2019 08:28:13 -0400
Subject: hs-v3: Add consensus parameters for DoS defenses

Part of #15516

Signed-off-by: David Goulet <dgoulet@torproject.org>
---
 src/feature/hs/hs_dos.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)

(limited to 'src/feature/hs/hs_dos.c')

diff --git a/src/feature/hs/hs_dos.c b/src/feature/hs/hs_dos.c
index ad9d044f48..25d282adbc 100644
--- a/src/feature/hs/hs_dos.c
+++ b/src/feature/hs/hs_dos.c
@@ -18,14 +18,92 @@
 
 #define HS_DOS_PRIVATE
 
+#include "core/or/or.h"
+#include "app/config/config.h"
+
 #include "core/or/circuitlist.h"
 
+#include "feature/nodelist/networkstatus.h"
+#include "feature/relay/routermode.h"
+
+#include "lib/evloop/token_bucket.h"
+
 #include "hs_dos.h"
 
+/* Default value of the allowed INTRODUCE2 cell rate per second. Above that
+ * value per second, the introduction is denied. */
+#define HS_DOS_INTRODUCE_CELL_RATE_PER_SEC 25
+
+/* Default value of the allowed INTRODUCE2 cell burst per second. This is the
+ * maximum value a token bucket has per second. We thus allow up to this value
+ * of INTRODUCE2 cell per second but the bucket is refilled by the rate value
+ * but never goes above that burst value. */
+#define HS_DOS_INTRODUCE_CELL_BURST_PER_SEC 200
+
+/* Consensus parameters. */
+static uint32_t hs_dos_introduce_rate_per_sec =
+  HS_DOS_INTRODUCE_CELL_RATE_PER_SEC;
+static uint32_t hs_dos_introduce_burst_per_sec =
+  HS_DOS_INTRODUCE_CELL_BURST_PER_SEC;
+
+/* Return the parameter for the introduction rate per sec. */
+static uint32_t
+get_param_rate_per_sec(const networkstatus_t *ns)
+{
+  return networkstatus_get_param(ns, "HiddenServiceEnableIntroDoSRatePerSec",
+                                 HS_DOS_INTRODUCE_CELL_RATE_PER_SEC,
+                                 0, INT32_MAX);
+}
+
+/* Return the parameter for the introduction burst per sec. */
+static uint32_t
+get_param_burst_per_sec(const networkstatus_t *ns)
+{
+  return networkstatus_get_param(ns, "HiddenServiceEnableIntroDoSBurstPerSec",
+                                 HS_DOS_INTRODUCE_CELL_BURST_PER_SEC,
+                                 0, INT32_MAX);
+}
+
+/* Set consensus parameters. */
+static void
+set_consensus_parameters(const networkstatus_t *ns)
+{
+  hs_dos_introduce_rate_per_sec = get_param_rate_per_sec(ns);
+  hs_dos_introduce_burst_per_sec = get_param_burst_per_sec(ns);
+}
+
 /*
  * Public API.
  */
 
+/* Return the INTRODUCE2 cell rate per second. */
+uint32_t
+hs_dos_get_intro2_rate(void)
+{
+  return hs_dos_introduce_rate_per_sec;
+}
+
+/* Return the INTRODUCE2 cell burst per second. */
+uint32_t
+hs_dos_get_intro2_burst(void)
+{
+  return hs_dos_introduce_burst_per_sec;
+}
+
+/* Called when the consensus has changed. We might have new consensus
+ * parameters to look at. */
+void
+hs_dos_consensus_has_changed(const networkstatus_t *ns)
+{
+  /* No point on updating these values if we are not a public relay that can
+   * be picked to be an introduction point. */
+  if (!public_server_mode(get_options())) {
+    return;
+  }
+
+  set_consensus_parameters(ns);
+}
+
 /* Return true iff an INTRODUCE2 cell can be sent on the given service
  * introduction circuit. */
 bool
@@ -58,3 +136,10 @@ hs_dos_can_send_intro2(or_circuit_t *s_intro_circ)
   /* Finally, we can send a new INTRODUCE2 if there are still tokens. */
   return token_bucket_ctr_get(&s_intro_circ->introduce2_bucket) > 0;
 }
+
+/* Initialize the onion service Denial of Service subsystem. */
+void
+hs_dos_init(void)
+{
+  set_consensus_parameters(NULL);
+}
-- 
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