1 files changed, 140 insertions, 0 deletions
diff --git a/src/or/dos.h b/src/or/dos.h
new file mode 100644
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+++ b/src/or/dos.h
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+/* Copyright (c) 2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/*
+ * \file dos.h
+ * \brief Header file for dos.c
+ */
+
+#ifndef TOR_DOS_H
+#define TOR_DOS_H
+
+/* Structure that keeps stats of client connection per-IP. */
+typedef struct cc_client_stats_t {
+  /* Number of allocated circuits remaining for this address.  It is
+   * decremented every time a new circuit is seen for this client address and
+   * if the count goes to 0, we have a positive detection. */
+  uint32_t circuit_bucket;
+
+  /* When was the last time we've refilled the circuit bucket? This is used to
+   * know if we need to refill the bucket when a new circuit is seen. It is
+   * synchronized using approx_time(). */
+  time_t last_circ_bucket_refill_ts;
+
+  /* This client address was detected to be above the circuit creation rate
+   * and this timestamp indicates until when it should remain marked as
+   * detected so we can apply a defense for the address. It is synchronized
+   * using the approx_time(). */
+  time_t marked_until_ts;
+} cc_client_stats_t;
+
+/* This object is a top level object that contains everything related to the
+ * per-IP client DoS mitigation. Because it is per-IP, it is used in the geoip
+ * clientmap_entry_t object. */
+typedef struct dos_client_stats_t {
+  /* Concurrent connection count from the specific address. 2^32 is most
+   * likely way too big for the amount of allowed file descriptors. */
+  uint32_t concurrent_count;
+
+  /* Circuit creation statistics. This is only used if the circuit creation
+   * subsystem has been enabled (dos_cc_enabled). */
+  cc_client_stats_t cc_stats;
+} dos_client_stats_t;
+
+/* General API. */
+
+/* Stub. */
+struct clientmap_entry_t;
+
+void dos_init(void);
+void dos_free_all(void);
+void dos_consensus_has_changed(const networkstatus_t *ns);
+int dos_enabled(void);
+void dos_log_heartbeat(void);
+void dos_geoip_entry_about_to_free(const struct clientmap_entry_t *geoip_ent);
+
+void dos_new_client_conn(or_connection_t *or_conn);
+void dos_close_client_conn(const or_connection_t *or_conn);
+
+int dos_should_refuse_single_hop_client(void);
+void dos_note_refuse_single_hop_client(void);
+
+/*
+ * Circuit creation DoS mitigation subsystemn interface.
+ */
+
+/* DoSCircuitCreationEnabled default. Disabled by default. */
+#define DOS_CC_ENABLED_DEFAULT 0
+/* DoSCircuitCreationDefenseType maps to the dos_cc_defense_type_t enum. */
+#define DOS_CC_DEFENSE_TYPE_DEFAULT DOS_CC_DEFENSE_REFUSE_CELL
+/* DoSCircuitCreationMinConnections default */
+#define DOS_CC_MIN_CONCURRENT_CONN_DEFAULT 3
+/* DoSCircuitCreationRateTenths is 3 per seconds. */
+#define DOS_CC_CIRCUIT_RATE_DEFAULT 3
+/* DoSCircuitCreationBurst default. */
+#define DOS_CC_CIRCUIT_BURST_DEFAULT 90
+/* DoSCircuitCreationDefenseTimePeriod in seconds. */
+#define DOS_CC_DEFENSE_TIME_PERIOD_DEFAULT (60 * 60)
+
+/* Type of defense that we can use for the circuit creation DoS mitigation. */
+typedef enum dos_cc_defense_type_t {
+  /* No defense used. */
+  DOS_CC_DEFENSE_NONE             = 1,
+  /* Refuse any cells which means a DESTROY cell will be sent back. */
+  DOS_CC_DEFENSE_REFUSE_CELL      = 2,
+
+  /* Maximum value that can be used. Useful for the boundaries of the
+   * consensus parameter. */
+  DOS_CC_DEFENSE_MAX              = 2,
+} dos_cc_defense_type_t;
+
+void dos_cc_new_create_cell(channel_t *channel);
+dos_cc_defense_type_t dos_cc_get_defense_type(channel_t *chan);
+
+/*
+ * Concurrent connection DoS mitigation interface.
+ */
+
+/* DoSConnectionEnabled default. Disabled by default. */
+#define DOS_CONN_ENABLED_DEFAULT 0
+/* DoSConnectionMaxConcurrentCount default. */
+#define DOS_CONN_MAX_CONCURRENT_COUNT_DEFAULT 100
+/* DoSConnectionDefenseType maps to the dos_conn_defense_type_t enum. */
+#define DOS_CONN_DEFENSE_TYPE_DEFAULT DOS_CONN_DEFENSE_CLOSE
+
+/* Type of defense that we can use for the concurrent connection DoS
+ * mitigation. */
+typedef enum dos_conn_defense_type_t {
+  /* No defense used. */
+  DOS_CONN_DEFENSE_NONE             = 1,
+  /* Close immediately the connection meaning refuse it. */
+  DOS_CONN_DEFENSE_CLOSE            = 2,
+
+  /* Maximum value that can be used. Useful for the boundaries of the
+   * consensus parameter. */
+  DOS_CONN_DEFENSE_MAX              = 2,
+} dos_conn_defense_type_t;
+
+dos_conn_defense_type_t dos_conn_addr_get_defense_type(const tor_addr_t *addr);
+
+#ifdef DOS_PRIVATE
+
+STATIC uint32_t get_param_conn_max_concurrent_count(
+                                              const networkstatus_t *ns);
+STATIC uint32_t get_param_cc_circuit_burst(const networkstatus_t *ns);
+STATIC uint32_t get_param_cc_min_concurrent_connection(
+                                            const networkstatus_t *ns);
+
+STATIC uint64_t get_circuit_rate_per_second(void);
+STATIC void cc_stats_refill_bucket(cc_client_stats_t *stats,
+                                   const tor_addr_t *addr);
+
+MOCK_DECL(STATIC unsigned int, get_param_cc_enabled,
+          (const networkstatus_t *ns));
+MOCK_DECL(STATIC unsigned int, get_param_conn_enabled,
+          (const networkstatus_t *ns));
+
+#endif /* TOR_DOS_PRIVATE */
+
+#endif /* TOR_DOS_H */
+