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.

2 files changed, 47 insertions, 9 deletions

diff --git a/src/feature/client/entrynodes.c b/src/feature/client/entrynodes.c
index b078382e76..4783faf9dd 100644
--- a/src/feature/client/entrynodes.c
+++ b/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);
   }
diff --git a/src/feature/client/entrynodes.h b/src/feature/client/entrynodes.h
index 08fd7cf745..2a94775430 100644
--- a/src/feature/client/entrynodes.h
+++ b/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, \