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@@ -15,11 +15,13 @@
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#include "config.h"
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#include "networkstatus.h"
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+#include "nodelist.h"
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#include "hs_cache.h"
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#include "hs_common.h"
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#include "hs_service.h"
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#include "rendcommon.h"
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#include "rendservice.h"
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+#include "router.h"
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#include "shared_random.h"
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/* Ed25519 Basepoint value. Taken from section 5 of
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@@ -30,6 +32,48 @@ static const char *str_ed25519_basepoint =
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"463168356949264781694283940034751631413"
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"07993866256225615783033603165251855960)";
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+/* Helper function: The key is a digest that we compare to a node_t object
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+ * current hsdir_index. */
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+static int
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+compare_digest_to_current_hsdir_index(const void *_key, const void **_member)
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+{
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+ const char *key = _key;
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+ const node_t *node = *_member;
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+ return tor_memcmp(key, node->hsdir_index->current, DIGEST256_LEN);
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+}
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+
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+/* Helper function: The key is a digest that we compare to a node_t object
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+ * next hsdir_index. */
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+static int
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+compare_digest_to_next_hsdir_index(const void *_key, const void **_member)
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+{
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+ const char *key = _key;
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+ const node_t *node = *_member;
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+ return tor_memcmp(key, node->hsdir_index->next, DIGEST256_LEN);
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+}
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+
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+/* Helper function: Compare two node_t objects current hsdir_index. */
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+static int
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+compare_node_current_hsdir_index(const void **a, const void **b)
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+{
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+ const node_t *node1= *a;
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+ const node_t *node2 = *b;
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+ return tor_memcmp(node1->hsdir_index->current,
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+ node2->hsdir_index->current,
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+ DIGEST256_LEN);
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+}
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+
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+/* Helper function: Compare two node_t objects next hsdir_index. */
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+static int
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+compare_node_next_hsdir_index(const void **a, const void **b)
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+{
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+ const node_t *node1= *a;
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+ const node_t *node2 = *b;
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+ return tor_memcmp(node1->hsdir_index->next,
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+ node2->hsdir_index->next,
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+ DIGEST256_LEN);
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+}
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+
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/* Allocate and return a string containing the path to filename in directory.
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* This function will never return NULL. The caller must free this path. */
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char *
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@@ -887,6 +931,114 @@ hs_get_hsdir_spread_store(void)
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HS_DEFAULT_HSDIR_SPREAD_STORE, 1, 128);
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}
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+/* For a given blinded key and time period number, get the responsible HSDir
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+ * and put their routerstatus_t object in the responsible_dirs list. If
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+ * is_next_period is true, the next hsdir_index of the node_t is used. If
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+ * is_client is true, the spread fetch consensus parameter is used else the
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+ * spread store is used which is only for upload. This function can't fail but
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+ * it is possible that the responsible_dirs list contains fewer nodes than
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+ * expected.
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+ *
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+ * This function goes over the latest consensus routerstatus list and sorts it
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+ * by their node_t hsdir_index then does a binary search to find the closest
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+ * node. All of this makes it a bit CPU intensive so use it wisely. */
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+void
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+hs_get_responsible_hsdirs(const ed25519_public_key_t *blinded_pk,
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+ uint64_t time_period_num, int is_next_period,
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+ int is_client, smartlist_t *responsible_dirs)
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+{
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+ smartlist_t *sorted_nodes;
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+ /* The compare function used for the smartlist bsearch. We have two
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+ * different depending on is_next_period. */
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+ int (*cmp_fct)(const void *, const void **);
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+
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+ tor_assert(blinded_pk);
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+ tor_assert(responsible_dirs);
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+
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+ sorted_nodes = smartlist_new();
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+
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+ /* Add every node_t that support HSDir v3 for which we do have a valid
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+ * hsdir_index already computed for them for this consensus. */
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+ {
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+ networkstatus_t *c = networkstatus_get_latest_consensus();
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+ if (!c || smartlist_len(c->routerstatus_list) == 0) {
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+ log_warn(LD_REND, "No valid consensus so we can't get the responsible "
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+ "hidden service directories.");
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+ goto done;
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+ }
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+ SMARTLIST_FOREACH_BEGIN(c->routerstatus_list, const routerstatus_t *, rs) {
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+ /* Even though this node_t object won't be modified and should be const,
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+ * we can't add const object in a smartlist_t. */
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+ node_t *n = node_get_mutable_by_id(rs->identity_digest);
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+ tor_assert(n);
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+ if (node_supports_v3_hsdir(n) && rs->is_hs_dir) {
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+ if (BUG(n->hsdir_index == NULL)) {
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+ continue;
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+ }
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+ smartlist_add(sorted_nodes, n);
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+ }
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+ } SMARTLIST_FOREACH_END(rs);
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+ }
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+ if (smartlist_len(sorted_nodes) == 0) {
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+ log_warn(LD_REND, "No nodes found to be HSDir or supporting v3.");
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+ goto done;
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+ }
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+
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+ /* First thing we have to do is sort all node_t by hsdir_index. The
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+ * is_next_period tells us if we want the current or the next one. Set the
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+ * bsearch compare function also while we are at it. */
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+ if (is_next_period) {
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+ smartlist_sort(sorted_nodes, compare_node_next_hsdir_index);
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+ cmp_fct = compare_digest_to_next_hsdir_index;
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+ } else {
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+ smartlist_sort(sorted_nodes, compare_node_current_hsdir_index);
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+ cmp_fct = compare_digest_to_current_hsdir_index;
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+ }
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+
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+ /* For all replicas, we'll select a set of HSDirs using the consensus
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+ * parameters and the sorted list. The replica starting at value 1 is
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+ * defined by the specification. */
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+ for (int replica = 1; replica <= hs_get_hsdir_n_replicas(); replica++) {
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+ int idx, start, found, n_added = 0;
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+ uint8_t hs_index[DIGEST256_LEN] = {0};
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+ /* Number of node to add to the responsible dirs list depends on if we are
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+ * trying to fetch or store. A client always fetches. */
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+ int n_to_add = (is_client) ? hs_get_hsdir_spread_fetch() :
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+ hs_get_hsdir_spread_store();
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+
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+ /* Get the index that we should use to select the node. */
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+ hs_build_hs_index(replica, blinded_pk, time_period_num, hs_index);
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+ /* The compare function pointer has been set correctly earlier. */
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+ start = idx = smartlist_bsearch_idx(sorted_nodes, hs_index, cmp_fct,
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+ &found);
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+ /* Getting the length of the list if no member is greater than the key we
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+ * are looking for so start at the first element. */
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+ if (idx == smartlist_len(sorted_nodes)) {
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+ start = idx = 0;
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+ }
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+ while (n_added < n_to_add) {
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+ const node_t *node = smartlist_get(sorted_nodes, idx);
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+ /* If the node has already been selected which is possible between
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+ * replicas, the specification says to skip over. */
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+ if (!smartlist_contains(responsible_dirs, node->rs)) {
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+ smartlist_add(responsible_dirs, node->rs);
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+ ++n_added;
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+ }
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+ if (++idx == smartlist_len(sorted_nodes)) {
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+ /* Wrap if we've reached the end of the list. */
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+ idx = 0;
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+ }
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+ if (idx == start) {
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+ /* We've gone over the whole list, stop and avoid infinite loop. */
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+ break;
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+ }
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+ }
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+ }
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+
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+ done:
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+ smartlist_free(sorted_nodes);
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+}
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+
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/* Initialize the entire HS subsytem. This is called in tor_init() before any
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* torrc options are loaded. Only for >= v3. */
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void
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