Prop#329 Pool: Avoid sharing Guards and Middles between circuits.

Conflux must not use the same Guard for each leg; nor the same middle for each
leg.

src/core/or/circuitbuild.c

@@ -45,6 +45,7 @@
 #include "core/or/command.h"
 #include "core/or/connection_edge.h"
 #include "core/or/connection_or.h"
+#include "core/or/conflux_pool.h"
 #include "core/or/extendinfo.h"
 #include "core/or/onion.h"
 #include "core/or/ocirc_event.h"
@@ -89,7 +90,8 @@ static int circuit_send_first_onion_skin(origin_circuit_t *circ);
 static int circuit_build_no_more_hops(origin_circuit_t *circ);
 static int circuit_send_intermediate_onion_skin(origin_circuit_t *circ,
                                                 crypt_path_t *hop);
-static const node_t *choose_good_middle_server(uint8_t purpose,
+static const node_t *choose_good_middle_server(const origin_circuit_t *,
+                          uint8_t purpose,
                           cpath_build_state_t *state,
                           crypt_path_t *head,
                           int cur_len);
@@ -2313,7 +2315,8 @@ build_vanguard_middle_exclude_list(uint8_t purpose,
  * hop, based on already chosen nodes.
  */
 static smartlist_t *
-build_middle_exclude_list(uint8_t purpose,
+build_middle_exclude_list(const origin_circuit_t *circ,
+                          uint8_t purpose,
                           cpath_build_state_t *state,
                           crypt_path_t *head,
                           int cur_len)
@@ -2330,6 +2333,9 @@ build_middle_exclude_list(uint8_t purpose,
 
   excluded = smartlist_new();
 
+  // Exclude other middles on pending and built conflux circs
+  conflux_add_middles_to_exclude_list(circ, excluded);
+
   /* For non-vanguard circuits, add the exit and its family to the exclude list
    * (note that the exit/last hop is always chosen first in
    * circuit_establish_circuit()). */
@@ -2423,7 +2429,8 @@ pick_vanguard_middle_node(const or_options_t *options,
  * family, and make sure we don't duplicate any previous nodes or their
  * families. */
 static const node_t *
-choose_good_middle_server(uint8_t purpose,
+choose_good_middle_server(const origin_circuit_t * circ,
+                          uint8_t purpose,
                           cpath_build_state_t *state,
                           crypt_path_t *head,
                           int cur_len)
@@ -2438,7 +2445,7 @@ choose_good_middle_server(uint8_t purpose,
   log_debug(LD_CIRC, "Contemplating intermediate hop #%d: random choice.",
             cur_len+1);
 
-  excluded = build_middle_exclude_list(purpose, state, head, cur_len);
+  excluded = build_middle_exclude_list(circ, purpose, state, head, cur_len);
 
   flags |= cpath_build_state_to_crn_flags(state);
   flags |= cpath_build_state_to_crn_ipv6_extend_flag(state, cur_len);
@@ -2483,7 +2490,8 @@ choose_good_middle_server(uint8_t purpose,
  * guard worked or not.
  */
 const node_t *
-choose_good_entry_server(uint8_t purpose, cpath_build_state_t *state,
+choose_good_entry_server(const origin_circuit_t *circ,
+                         uint8_t purpose, cpath_build_state_t *state,
                          circuit_guard_state_t **guard_state_out)
 {
   const node_t *choice;
@@ -2505,7 +2513,7 @@ choose_good_entry_server(uint8_t purpose, cpath_build_state_t *state,
     /* This request is for an entry server to use for a regular circuit,
      * and we use entry guard nodes.  Just return one of the guard nodes.  */
     tor_assert(guard_state_out);
-    return guards_choose_guard(state, purpose, guard_state_out);
+    return guards_choose_guard(circ, state, purpose, guard_state_out);
   }
 
   excluded = smartlist_new();
@@ -2551,7 +2559,7 @@ onion_extend_cpath(origin_circuit_t *circ)
   if (cur_len == state->desired_path_len - 1) { /* Picking last node */
     info = extend_info_dup(state->chosen_exit);
   } else if (cur_len == 0) { /* picking first node */
-    const node_t *r = choose_good_entry_server(purpose, state,
+    const node_t *r = choose_good_entry_server(circ, purpose, state,
                                                &circ->guard_state);
     if (r) {
       /* If we're a client, use the preferred address rather than the
@@ -2564,7 +2572,7 @@ onion_extend_cpath(origin_circuit_t *circ)
     }
   } else {
     const node_t *r =
-      choose_good_middle_server(purpose, state, circ->cpath, cur_len);
+      choose_good_middle_server(circ, purpose, state, circ->cpath, cur_len);
     if (r) {
       info = extend_info_from_node(r, 0, false);
     }

src/core/or/circuitbuild.h

@@ -57,7 +57,8 @@ const char *build_state_get_exit_nickname(cpath_build_state_t *state);
 
 struct circuit_guard_state_t;
 
-const node_t *choose_good_entry_server(uint8_t purpose,
+const node_t *choose_good_entry_server(const origin_circuit_t *circ,
+                           uint8_t purpose,
                            cpath_build_state_t *state,
                            struct circuit_guard_state_t **guard_state_out);
 void circuit_upgrade_circuits_from_guard_wait(void);

src/core/or/conflux_pool.c

@@ -31,6 +31,8 @@
 #include "core/or/crypt_path_st.h"
 #include "core/or/or_circuit_st.h"
 #include "core/or/origin_circuit_st.h"
+#include "core/or/extend_info_st.h"
+#include "core/or/conflux_st.h"
 
 #include "feature/nodelist/nodelist.h"
 
@@ -1092,6 +1094,127 @@ conflux_launch_leg(const uint8_t *nonce)
   return false;
 }
 
+/**
+ * Add the identity digest of the guard nodes of all legs of the conflux
+ * circuit.
+ *
+ * This function checks both pending and linked conflux circuits.
+ */
+void
+conflux_add_guards_to_exclude_list(const origin_circuit_t *orig_circ,
+                                   smartlist_t *excluded)
+{
+  tor_assert(orig_circ);
+  tor_assert(excluded);
+
+  /* Ease our lives. */
+  const circuit_t *circ = TO_CIRCUIT(orig_circ);
+
+  /* Ignore if this is not conflux related. */
+  if (!CIRCUIT_IS_CONFLUX(circ)) {
+    return;
+  }
+
+  /* When building a circuit, we should not have a conflux object
+   * ourselves (though one may exist elsewhere). */
+  tor_assert(!circ->conflux);
+
+  /* Getting here without a nonce is a code flow issue. */
+  if (BUG(!circ->conflux_pending_nonce)) {
+    return;
+  }
+
+  /* A linked set exists, use it. */
+  const conflux_t *cfx = linked_pool_get(circ->conflux_pending_nonce, true);
+  if (cfx) {
+    CONFLUX_FOR_EACH_LEG_BEGIN(cfx, leg) {
+      const origin_circuit_t *ocirc = CONST_TO_ORIGIN_CIRCUIT(leg->circ);
+      smartlist_add(excluded,
+                    tor_memdup(ocirc->cpath->extend_info->identity_digest,
+                               DIGEST_LEN));
+    } CONFLUX_FOR_EACH_LEG_END(leg);
+  }
+
+  /* An unlinked set might exist for this nonce, if so, add the second hop of
+   * the existing legs to the exclusion list. */
+  unlinked_circuits_t *unlinked =
+    unlinked_pool_get(circ->conflux_pending_nonce, true);
+  if (unlinked) {
+    tor_assert(unlinked->is_client);
+    SMARTLIST_FOREACH_BEGIN(unlinked->legs, leg_t *, leg) {
+      /* Convert to origin circ and get cpath */
+      const origin_circuit_t *ocirc = CONST_TO_ORIGIN_CIRCUIT(leg->circ);
+      smartlist_add(excluded,
+                    tor_memdup(ocirc->cpath->extend_info->identity_digest,
+                               DIGEST_LEN));
+    } SMARTLIST_FOREACH_END(leg);
+  }
+}
+
+/**
+ * Add the identity digest of the middle nodes of all legs of the conflux
+ * circuit.
+ *
+ * This function checks both pending and linked conflux circuits.
+ *
+ * XXX: The add guard and middle could be merged since it is the exact same
+ * code except for the cpath position and the identity digest vs node_t in
+ * the list. We could use an extra param indicating guard or middle. */
+void
+conflux_add_middles_to_exclude_list(const origin_circuit_t *orig_circ,
+                                    smartlist_t *excluded)
+{
+  tor_assert(orig_circ);
+  tor_assert(excluded);
+
+  /* Ease our lives. */
+  const circuit_t *circ = TO_CIRCUIT(orig_circ);
+
+  /* Ignore if this is not conflux related. */
+  if (!CIRCUIT_IS_CONFLUX(circ)) {
+    return;
+  }
+
+  /* When building a circuit, we should not have a conflux object
+   * ourselves (though one may exist elsewhere). */
+  tor_assert(!circ->conflux);
+
+  /* Getting here without a nonce is a code flow issue. */
+  if (BUG(!circ->conflux_pending_nonce)) {
+    return;
+  }
+
+  /* A linked set exists, use it. */
+  const conflux_t *cfx = linked_pool_get(circ->conflux_pending_nonce, true);
+  if (cfx) {
+    CONFLUX_FOR_EACH_LEG_BEGIN(cfx, leg) {
+      const origin_circuit_t *ocirc = CONST_TO_ORIGIN_CIRCUIT(leg->circ);
+      node_t *node = node_get_mutable_by_id(
+                     ocirc->cpath->next->extend_info->identity_digest);
+      if (node) {
+        smartlist_add(excluded, node);
+      }
+    } CONFLUX_FOR_EACH_LEG_END(leg);
+  }
+
+  /* An unlinked set might exist for this nonce, if so, add the second hop of
+   * the existing legs to the exclusion list. */
+  unlinked_circuits_t *unlinked =
+    unlinked_pool_get(circ->conflux_pending_nonce, true);
+  if (unlinked) {
+    tor_assert(unlinked->is_client);
+    SMARTLIST_FOREACH_BEGIN(unlinked->legs, leg_t *, leg) {
+      /* Convert to origin circ and get cpath */
+      const origin_circuit_t *ocirc = CONST_TO_ORIGIN_CIRCUIT(leg->circ);
+      node_t *node = node_get_mutable_by_id(
+                     ocirc->cpath->next->extend_info->identity_digest);
+      if (node) {
+        smartlist_add(excluded, node);
+      }
+    } SMARTLIST_FOREACH_END(leg);
+  }
+}
+
 /** The given circuit is conflux pending and has closed. This deletes the leg
  * from the set, attempt to finalize it and relaunch a new leg. If the set is
  * empty after removing this leg, it is deleted. */

src/core/or/conflux_pool.h

@@ -21,6 +21,11 @@ void conflux_predict_new(time_t now);
 
 bool conflux_launch_leg(const uint8_t *nonce);
 
+void conflux_add_guards_to_exclude_list(const origin_circuit_t *circ,
+                                        smartlist_t *excluded);
+void conflux_add_middles_to_exclude_list(const origin_circuit_t *circ,
+                                    smartlist_t *excluded);
+
 void conflux_circuit_has_closed(circuit_t *circ);
 void conflux_circuit_has_opened(origin_circuit_t *orig_circ);
 void conflux_circuit_about_to_free(circuit_t *circ);

src/feature/client/entrynodes.c

@@ -126,6 +126,7 @@
 #include "core/or/circuitlist.h"
 #include "core/or/circuitstats.h"
 #include "core/or/circuituse.h"
+#include "core/or/conflux_pool.h"
 #include "core/or/policies.h"
 #include "feature/client/bridges.h"
 #include "feature/client/circpathbias.h"
@@ -151,6 +152,8 @@
 #include "core/or/origin_circuit_st.h"
 #include "app/config/or_state_st.h"
 
+#include "core/or/conflux_util.h"
+
 /** A list of existing guard selection contexts. */
 static smartlist_t *guard_contexts = NULL;
 /** The currently enabled guard selection context. */
@@ -1588,6 +1591,19 @@ guard_create_exit_restriction(const uint8_t *exit_id)
   return rst;
 }
 
+/* Allocate and return a new exit guard restriction that excludes all current
+ * and pending conflux guards */
+STATIC entry_guard_restriction_t *
+guard_create_conflux_restriction(const origin_circuit_t *circ)
+{
+  entry_guard_restriction_t *rst = NULL;
+  rst = tor_malloc_zero(sizeof(entry_guard_restriction_t));
+  rst->type = RST_EXCL_LIST;
+  rst->excluded = smartlist_new();
+  conflux_add_guards_to_exclude_list(circ, rst->excluded);
+  return rst;
+}
+
 /** If we have fewer than this many possible usable guards, don't set
  * MD-availability-based restrictions: we might denylist all of them. */
 #define MIN_GUARDS_FOR_MD_RESTRICTION 10
@@ -1680,6 +1696,8 @@ entry_guard_obeys_restriction(const entry_guard_t *guard,
     return guard_obeys_exit_restriction(guard, rst);
   } else if (rst->type == RST_OUTDATED_MD_DIRSERVER) {
     return guard_obeys_md_dirserver_restriction(guard);
+  } else if (rst->type == RST_EXCL_LIST) {
+    return !smartlist_contains_digest(rst->excluded, guard->identity);
   }
 
   tor_assert_nonfatal_unreached();
@@ -2427,6 +2445,11 @@ entry_guard_has_higher_priority(entry_guard_t *a, entry_guard_t *b)
 STATIC void
 entry_guard_restriction_free_(entry_guard_restriction_t *rst)
 {
+  if (rst && rst->excluded) {
+    SMARTLIST_FOREACH(rst->excluded, void *, g,
+                      tor_free(g));
+    smartlist_free(rst->excluded);
+  }
   tor_free(rst);
 }
 
@@ -3780,7 +3803,8 @@ guards_update_all(void)
 /** Helper: pick a guard for a circuit, with whatever algorithm is
     used. */
 const node_t *
-guards_choose_guard(cpath_build_state_t *state,
+guards_choose_guard(const origin_circuit_t *circ,
+                    cpath_build_state_t *state,
                     uint8_t purpose,
                     circuit_guard_state_t **guard_state_out)
 {
@@ -3788,14 +3812,18 @@ guards_choose_guard(cpath_build_state_t *state,
   const uint8_t *exit_id = NULL;
   entry_guard_restriction_t *rst = NULL;
 
-  /* Only apply restrictions if we have a specific exit node in mind, and only
-   * if we are not doing vanguard circuits: we don't want to apply guard
-   * restrictions to vanguard circuits. */
-  if (state && !circuit_should_use_vanguards(purpose) &&
+  /* If we this is a conflux circuit, build an exclusion list for it. */
+  if (CIRCUIT_IS_CONFLUX(TO_CIRCUIT(circ))) {
+    rst = guard_create_conflux_restriction(circ);
+    /* Don't allow connecting back to the exit if there is one */
+    if (state && (exit_id = build_state_get_exit_rsa_id(state))) {
+      /* add the exit_id to the excluded list */
+      smartlist_add(rst->excluded, tor_memdup(exit_id, DIGEST_LEN));
+    }
+  } else if (state && !circuit_should_use_vanguards(purpose) &&
       (exit_id = build_state_get_exit_rsa_id(state))) {
     /* We're building to a targeted exit node, so that node can't be
-     * chosen as our guard for this circuit.  Remember that fact in a
-     * restriction. */
+     * chosen as our guard for this circuit, unless we're vanguards. */
     rst = guard_create_exit_restriction(exit_id);
     tor_assert(rst);
   }

src/feature/client/entrynodes.h

@@ -294,7 +294,9 @@ typedef enum guard_restriction_type_t {
   /* Don't pick the same guard node as our exit node (or its family) */
   RST_EXIT_NODE = 0,
   /* Don't pick dirguards that have previously shown to be outdated */
-  RST_OUTDATED_MD_DIRSERVER = 1
+  RST_OUTDATED_MD_DIRSERVER = 1,
+  /* Don't pick guards if they are in the exclusion list */
+  RST_EXCL_LIST = 2,
 } guard_restriction_type_t;
 
 /**
@@ -312,6 +314,10 @@ struct entry_guard_restriction_t {
    * digest must not equal this; and it must not be in the same family as any
    * node with this digest. */
   uint8_t exclude_id[DIGEST_LEN];
+
+  /* In the case of RST_EXCL_LIST, any identity digests in this list
+   * must not be used. */
+  smartlist_t *excluded;
 };
 
 /**
@@ -337,7 +343,8 @@ struct circuit_guard_state_t {
 
 /* Common entry points for old and new guard code */
 int guards_update_all(void);
-const node_t *guards_choose_guard(cpath_build_state_t *state,
+const node_t *guards_choose_guard(const origin_circuit_t *circ,
+                                  cpath_build_state_t *state,
                                   uint8_t purpose,
                                   circuit_guard_state_t **guard_state_out);
 const node_t *guards_choose_dirguard(uint8_t dir_purpose,
@@ -597,6 +604,9 @@ STATIC entry_guard_restriction_t *guard_create_exit_restriction(
 
 STATIC entry_guard_restriction_t *guard_create_dirserver_md_restriction(void);
 
+STATIC entry_guard_restriction_t * guard_create_conflux_restriction(
+                   const origin_circuit_t *circ);
+
 STATIC void entry_guard_restriction_free_(entry_guard_restriction_t *rst);
 #define entry_guard_restriction_free(rst)  \
   FREE_AND_NULL(entry_guard_restriction_t, \