Stop putting unsupported ed25519 link auth in v3 onion service descs

Stop putting ed25519 link specifiers in v3 onion service descriptors,
when the intro point doesn't support ed25519 link authentication.

Fixes bug 26627; bugfix on 0.3.2.4-alpha.

changes/bug26627

@@ -2,3 +2,6 @@
     - Stop sending ed25519 link specifiers in v3 onion service introduce
       cells, when the rendezvous point doesn't support ed25519 link
       authentication. Fixes bug 26627; bugfix on 0.3.2.4-alpha.
+    - Stop putting ed25519 link specifiers in v3 onion service descriptors,
+      when the intro point doesn't support ed25519 link authentication.
+      Fixes bug 26627; bugfix on 0.3.2.4-alpha.

src/or/hs_service.c

@@ -376,17 +376,21 @@ service_intro_point_free_void(void *obj)
 }
 
 /* Return a newly allocated service intro point and fully initialized from the
- * given extend_info_t ei if non NULL. If is_legacy is true, we also generate
- * the legacy key. On error, NULL is returned.
+ * given extend_info_t ei if non NULL.
+ * If is_legacy is true, we also generate the legacy key.
+ * If supports_ed25519_link_handshake_any is true, we add the relay's ed25519
+ * key to the link specifiers.
  *
  * If ei is NULL, returns a hs_service_intro_point_t with an empty link
  * specifier list and no onion key. (This is used for testing.)
+ * On any other error, NULL is returned.
  *
  * ei must be an extend_info_t containing an IPv4 address. (We will add supoort
  * for IPv6 in a later release.) When calling extend_info_from_node(), pass
  * 0 in for_direct_connection to make sure ei always has an IPv4 address. */
 STATIC hs_service_intro_point_t *
-service_intro_point_new(const extend_info_t *ei, unsigned int is_legacy)
+service_intro_point_new(const extend_info_t *ei, unsigned int is_legacy,
+                        unsigned int supports_ed25519_link_handshake_any)
 {
   hs_desc_link_specifier_t *ls;
   hs_service_intro_point_t *ip;
@@ -453,10 +457,13 @@ service_intro_point_new(const extend_info_t *ei, unsigned int is_legacy)
   }
   smartlist_add(ip->base.link_specifiers, ls);
 
-  /* ed25519 identity key is optional for intro points */
-  ls = hs_desc_link_specifier_new(ei, LS_ED25519_ID);
-  if (ls) {
-    smartlist_add(ip->base.link_specifiers, ls);
+  /* ed25519 identity key is optional for intro points. If the node supports
+   * ed25519 link authentication, we include it. */
+  if (supports_ed25519_link_handshake_any) {
+    ls = hs_desc_link_specifier_new(ei, LS_ED25519_ID);
+    if (ls) {
+      smartlist_add(ip->base.link_specifiers, ls);
+    }
   }
 
   /* IPv6 is not supported in this release. */
@@ -1586,8 +1593,12 @@ pick_intro_point(unsigned int direct_conn, smartlist_t *exclude_nodes)
     tor_assert_nonfatal(!ed25519_public_key_is_zero(&info->ed_identity));
   }
 
-  /* Create our objects and populate them with the node information. */
-  ip = service_intro_point_new(info, !node_supports_ed25519_hs_intro(node));
+  /* Create our objects and populate them with the node information.
+   * We don't care if the intro's link auth is compatible with us, because
+   * we are sending the ed25519 key to a remote client via the descriptor. */
+  ip = service_intro_point_new(info, !node_supports_ed25519_hs_intro(node),
+                               node_supports_ed25519_link_authentication(node,
+                                                                         0));
   if (ip == NULL) {
     goto err;
   }

src/or/hs_service.h

@@ -307,8 +307,9 @@ STATIC void remove_service(hs_service_ht *map, hs_service_t *service);
 STATIC int register_service(hs_service_ht *map, hs_service_t *service);
 /* Service introduction point functions. */
 STATIC hs_service_intro_point_t *service_intro_point_new(
-                                         const extend_info_t *ei,
-                                         unsigned int is_legacy);
+                            const extend_info_t *ei,
+                            unsigned int is_legacy,
+                            unsigned int supports_ed25519_link_handshake_any);
 STATIC void service_intro_point_free_(hs_service_intro_point_t *ip);
 #define service_intro_point_free(ip)                            \
   FREE_AND_NULL(hs_service_intro_point_t,             \

src/test/test_hs_cell.c

@@ -38,7 +38,7 @@ test_gen_establish_intro_cell(void *arg)
      attempt to parse it. */
   {
     /* We only need the auth key pair here. */
-    hs_service_intro_point_t *ip = service_intro_point_new(NULL, 0);
+    hs_service_intro_point_t *ip = service_intro_point_new(NULL, 0, 0);
     /* Auth key pair is generated in the constructor so we are all set for
      * using this IP object. */
     ret = hs_cell_build_establish_intro(circ_nonce, ip, buf);
@@ -106,7 +106,7 @@ test_gen_establish_intro_cell_bad(void *arg)
      ed25519_sign_prefixed() function and make it fail. */
   cell = trn_cell_establish_intro_new();
   tt_assert(cell);
-  ip = service_intro_point_new(NULL, 0);
+  ip = service_intro_point_new(NULL, 0, 0);
   cell_len = hs_cell_build_establish_intro(circ_nonce, ip, NULL);
   service_intro_point_free(ip);
   expect_log_msg_containing("Unable to make signature for "

src/test/test_hs_intropoint.c

@@ -49,7 +49,7 @@ new_establish_intro_cell(const char *circ_nonce,
 
   /* Auth key pair is generated in the constructor so we are all set for
    * using this IP object. */
-  ip = service_intro_point_new(NULL, 0);
+  ip = service_intro_point_new(NULL, 0, 0);
   tt_assert(ip);
   cell_len = hs_cell_build_establish_intro(circ_nonce, ip, buf);
   tt_i64_op(cell_len, OP_GT, 0);
@@ -75,7 +75,7 @@ new_establish_intro_encoded_cell(const char *circ_nonce, uint8_t *cell_out)
 
   /* Auth key pair is generated in the constructor so we are all set for
    * using this IP object. */
-  ip = service_intro_point_new(NULL, 0);
+  ip = service_intro_point_new(NULL, 0, 0);
   tt_assert(ip);
   cell_len = hs_cell_build_establish_intro(circ_nonce, ip, cell_out);
   tt_i64_op(cell_len, OP_GT, 0);

src/test/test_hs_service.c

@@ -241,7 +241,7 @@ static hs_service_intro_point_t *
 helper_create_service_ip(void)
 {
   hs_desc_link_specifier_t *ls;
-  hs_service_intro_point_t *ip = service_intro_point_new(NULL, 0);
+  hs_service_intro_point_t *ip = service_intro_point_new(NULL, 0, 0);
   tor_assert(ip);
   /* Add a first unused link specifier. */
   ls = tor_malloc_zero(sizeof(*ls));