Split the behavior of node_supports_ed25519_link_authentication().

Before, this function meant "can we connect to this node and
authenticate it using its ed25519 key?"  Now it can additionally
mean, "when somebody else connects to this node, do we expect that
they can authenticate using the node's ed25519 key"?

This change lets us future-proof our link authentication a bit.

Closes ticket 20895.  No backport needed, since ed25519 link
authentication support has not been in any LTS release yet, and
existing releases with it should be obsolete before any releases
without support for linkauth=3 are released.

diff --git a/changes/ticket20895 b/changes/ticket20895
new file mode 100644 (file)
index 0000000..a1d8204
--- /dev/null
+++ b/changes/ticket20895
@@ -0,0 +1,6 @@
+  o Minor features (forward-compatibility):
+    - If a relay supports some link authentication protocol that we do not
+      recognize, then include that relay's ed25519 key when telling other
+      relays to extend to it.  Previously, we treated future versions as if
+      they were too old to support ed25519 link authentication.
+      Closes ticket 20895.

diff --git a/src/or/circuitbuild.c b/src/or/circuitbuild.c
index 279308afcbf9db1e26978bba73981e20a6b1b2a4..45bf0195450074009c50aa0cd71edd9126988d90 100644 (file)
--- a/src/or/circuitbuild.c
+++ b/src/or/circuitbuild.c
@@ -1290,7 +1290,7 @@ circuit_extend(cell_t *cell, circuit_t *circ)
     const node_t *node = node_get_by_id((const char*)ec.node_id);
     const ed25519_public_key_t *node_ed_id = NULL;
     if (node &&
-        node_supports_ed25519_link_authentication(node) &&
+        node_supports_ed25519_link_authentication(node, 1) &&
         (node_ed_id = node_get_ed25519_id(node))) {
       ed25519_pubkey_copy(&ec.ed_pubkey, node_ed_id);
     }
@@ -2698,7 +2698,7 @@ extend_info_from_node(const node_t *node, int for_direct_connect)
 
   /* Don't send the ed25519 pubkey unless the target node actually supports
    * authenticating with it. */
-  if (node_supports_ed25519_link_authentication(node)) {
+  if (node_supports_ed25519_link_authentication(node, 0)) {
     log_info(LD_CIRC, "Including Ed25519 ID for %s", node_describe(node));
     ed_pubkey = node_get_ed25519_id(node);
   } else if (node_get_ed25519_id(node)) {

diff --git a/src/or/connection_or.c b/src/or/connection_or.c
index d890b58da6fe04867f27ce43e3b8ba22ed2a5964..29c1166b3c58c66bd5021de3597997cb8f55835b 100644 (file)
--- a/src/or/connection_or.c
+++ b/src/or/connection_or.c
@@ -886,7 +886,7 @@ connection_or_check_canonicity(or_connection_t *conn, int started_here)
 
   const node_t *r = node_get_by_id(id_digest);
   if (r &&
-      node_supports_ed25519_link_authentication(r) &&
+      node_supports_ed25519_link_authentication(r, 1) &&
       ! node_ed25519_id_matches(r, ed_id)) {
     /* If this node is capable of proving an ed25519 ID,
      * we can't call this a canonical connection unless both IDs match. */

diff --git a/src/or/dirserv.c b/src/or/dirserv.c
index 06ac15d587c5392efbd439cf84fe8488b65ac862..75cd0879aa2104677c74309e9f5f0f3defda8966 100644 (file)
--- a/src/or/dirserv.c
+++ b/src/or/dirserv.c
@@ -3284,7 +3284,7 @@ dirserv_orconn_tls_done(const tor_addr_t *addr,
   ri = node->ri;
 
   if (get_options()->AuthDirTestEd25519LinkKeys &&
-      node_supports_ed25519_link_authentication(node) &&
+      node_supports_ed25519_link_authentication(node, 1) &&
       ri->cache_info.signing_key_cert) {
     /* We allow the node to have an ed25519 key if we haven't been told one in
      * the routerinfo, but if we *HAVE* been told one in the routerinfo, it
@@ -3367,7 +3367,7 @@ dirserv_single_reachability_test(time_t now, routerinfo_t *router)
   tor_assert(node);
 
   if (options->AuthDirTestEd25519LinkKeys &&
-      node_supports_ed25519_link_authentication(node)) {
+      node_supports_ed25519_link_authentication(node, 1)) {
     ed_id_key = &router->cache_info.signing_key_cert->signing_key;
   } else {
     ed_id_key = NULL;

diff --git a/src/or/hs_service.c b/src/or/hs_service.c
index 5759aa81273157bd97cc33d434bd5fd4eacc1c54..5ae7614e2963ac24e0d3400bbb9cf86fdff1dfc4 100644 (file)
--- a/src/or/hs_service.c
+++ b/src/or/hs_service.c
@@ -1494,7 +1494,7 @@ pick_intro_point(unsigned int direct_conn, smartlist_t *exclude_nodes)
   /* Let's do a basic sanity check here so that we don't end up advertising the
    * ed25519 identity key of relays that don't actually support the link
    * protocol */
-  if (!node_supports_ed25519_link_authentication(node)) {
+  if (!node_supports_ed25519_link_authentication(node, 0)) {
     tor_assert_nonfatal(ed25519_public_key_is_zero(&info->ed_identity));
   }
 

diff --git a/src/or/nodelist.c b/src/or/nodelist.c
index 00b8fb144fadbf68b3a20c41a3fff0620229364c..1f2d37f285f4773edf493e96c5566f8259350bd4 100644 (file)
--- a/src/or/nodelist.c
+++ b/src/or/nodelist.c
@@ -962,23 +962,29 @@ node_ed25519_id_matches(const node_t *node, const ed25519_public_key_t *id)
 }
 
 /** Return true iff <b>node</b> supports authenticating itself
- * by ed25519 ID during the link handshake in a way that we can understand
- * when we probe it. */
+ * by ed25519 ID during the link handshake.  If <b>compatible_with_us</b>,
+ * it needs to be using a link authentication method that we understand.
+ * If not, any plausible link authentication method will do. */
 int
-node_supports_ed25519_link_authentication(const node_t *node)
+node_supports_ed25519_link_authentication(const node_t *node,
+                                          int compatible_with_us)
 {
-  /* XXXX Oh hm. What if some day in the future there are link handshake
-   * versions that aren't 3 but which are ed25519 */
   if (! node_get_ed25519_id(node))
     return 0;
   if (node->ri) {
     const char *protos = node->ri->protocol_list;
     if (protos == NULL)
       return 0;
-    return protocol_list_supports_protocol(protos, PRT_LINKAUTH, 3);
+    if (compatible_with_us)
+      return protocol_list_supports_protocol(protos, PRT_LINKAUTH, 3);
+    else
+      return protocol_list_supports_protocol_or_later(protos, PRT_LINKAUTH, 3);
   }
   if (node->rs) {
-    return node->rs->supports_ed25519_link_handshake;
+    if (compatible_with_us)
+      return node->rs->supports_ed25519_link_handshake_compat;
+    else
+      return node->rs->supports_ed25519_link_handshake_any;
   }
   tor_assert_nonfatal_unreached_once();
   return 0;

diff --git a/src/or/nodelist.h b/src/or/nodelist.h
index 427e449ad92a1ce81925e916c41da5fa3430d7d3..58743c5e78d7d4911d8a7bc93fe5b0afd30aaf80 100644 (file)
--- a/src/or/nodelist.h
+++ b/src/or/nodelist.h
@@ -65,7 +65,8 @@ const smartlist_t *node_get_declared_family(const node_t *node);
 const ed25519_public_key_t *node_get_ed25519_id(const node_t *node);
 int node_ed25519_id_matches(const node_t *node,
                             const ed25519_public_key_t *id);
-int node_supports_ed25519_link_authentication(const node_t *node);
+int node_supports_ed25519_link_authentication(const node_t *node,
+                                              int compatible_with_us);
 int node_supports_v3_hsdir(const node_t *node);
 int node_supports_ed25519_hs_intro(const node_t *node);
 int node_supports_v3_rendezvous_point(const node_t *node);

diff --git a/src/or/or.h b/src/or/or.h
index 161d80ed96ca5d099fe030db6e1d940e6be1ff99..8e1d15b8cbab711ca1d042731dc6414983a7b317 100644 (file)
--- a/src/or/or.h
+++ b/src/or/or.h
@@ -2316,8 +2316,12 @@ typedef struct routerstatus_t {
   unsigned int supports_extend2_cells:1;
 
   /** True iff this router has a protocol list that allows it to negotiate
-   * ed25519 identity keys on a link handshake. */
-  unsigned int supports_ed25519_link_handshake:1;
+   * ed25519 identity keys on a link handshake with us. */
+  unsigned int supports_ed25519_link_handshake_compat:1;
+
+  /** True iff this router has a protocol list that allows it to negotiate
+   * ed25519 identity keys on a link handshake, at all. */
+  unsigned int supports_ed25519_link_handshake_any:1;
 
   /** True iff this router has a protocol list that allows it to be an
    * introduction point supporting ed25519 authentication key which is part of

diff --git a/src/or/routerparse.c b/src/or/routerparse.c
index 08c3fc0a026b263bca69cc16f4c3d2d384c51389..b26231db01a401fd170307325029d40cb39efd74 100644 (file)
--- a/src/or/routerparse.c
+++ b/src/or/routerparse.c
@@ -2701,8 +2701,10 @@ routerstatus_parse_entry_from_string(memarea_t *area,
     rs->protocols_known = 1;
     rs->supports_extend2_cells =
       protocol_list_supports_protocol(tok->args[0], PRT_RELAY, 2);
-    rs->supports_ed25519_link_handshake =
+    rs->supports_ed25519_link_handshake_compat =
       protocol_list_supports_protocol(tok->args[0], PRT_LINKAUTH, 3);
+    rs->supports_ed25519_link_handshake_any =
+      protocol_list_supports_protocol_or_later(tok->args[0], PRT_LINKAUTH, 3);
     rs->supports_ed25519_hs_intro =
       protocol_list_supports_protocol(tok->args[0], PRT_HSINTRO, 4);
     rs->supports_v3_hsdir =