Add comments and changes file for 4361; tweak control flow a bit

2 files changed, 21 insertions, 7 deletions

diff --git a/changes/bug4361 b/changes/bug4361
new file mode 100644
index 000000000..887eb9f3f
--- /dev/null
+++ b/changes/bug4361
@@ -0,0 +1,4 @@
+  o Minor bugfixes:
+    - Spec conformance: on a v3 handshake, do not send a NETINFO cell until
+      after we have received a CERTS cell. Bugfix on 0.2.3.6-alpha;
+      fixes bug 4361; patch by "frosty".
diff --git a/src/or/command.c b/src/or/command.c
index 808333e2b..e61fef7c2 100644
--- a/src/or/command.c
+++ b/src/or/command.c
@@ -686,8 +686,8 @@ command_process_versions_cell(var_cell_t *cell, or_connection_t *conn)
     const int send_certs = !started_here || public_server_mode(get_options());
     /* If we're a relay that got a connection, ask for authentication. */
     const int send_chall = !started_here && public_server_mode(get_options());
-    /* If our certs cell will authenticate us, or if we have no intention of
-     * authenticating, send a netinfo cell right now. */
+    /* If our certs cell will authenticate us, we can send a netinfo cell
+     * right now. */
     const int send_netinfo = !started_here;
     const int send_any =
       send_versions || send_certs || send_chall || send_netinfo;
@@ -915,6 +915,7 @@ command_process_cert_cell(var_cell_t *cell, or_connection_t *conn)
 
   uint8_t *ptr;
   int n_certs, i;
+  int send_netinfo = 0;
 
   if (conn->_base.state != OR_CONN_STATE_OR_HANDSHAKING_V3)
     ERR("We're not doing a v3 handshake!");
@@ -1020,12 +1021,12 @@ command_process_cert_cell(var_cell_t *cell, or_connection_t *conn)
 
     conn->handshake_state->id_cert = id_cert;
     id_cert = NULL;
+
     if (!public_server_mode(get_options())) {
-      if (connection_or_send_netinfo(conn) < 0) {
-        log_warn(LD_OR, "Couldn't send netinfo cell");
-        connection_mark_for_close(TO_CONN(conn));
-        goto err;
-      }
+      /* If we initiated the connection and we are not a public server, we
+       * aren't planning to authenticate at all.  At this point we know who we
+       * are talking to, so we can just send a netinfo now. */
+      send_netinfo = 1;
     }
   } else {
     if (! (id_cert && auth_cert))
@@ -1048,6 +1049,15 @@ command_process_cert_cell(var_cell_t *cell, or_connection_t *conn)
   }
 
   conn->handshake_state->received_cert_cell = 1;
+
+  if (send_netinfo) {
+    if (connection_or_send_netinfo(conn) < 0) {
+      log_warn(LD_OR, "Couldn't send netinfo cell");
+      connection_mark_for_close(TO_CONN(conn));
+      goto err;
+    }
+  }
+
  err:
   tor_cert_free(id_cert);
   tor_cert_free(link_cert);