dir: Look if circuit is closed in connection_dir_is_anonymous()

Before inspecting the p_chan, we must check if the circuit is marked for close
because if it is the case, the channels are nullified from the circuit.

Several valid cases can mark the circuit for close of the directory
connection.

Fixes #31958

Signed-off-by: David Goulet <dgoulet@torproject.org>

1 files changed, 11 insertions, 1 deletions

diff --git a/src/feature/dircommon/directory.c b/src/feature/dircommon/directory.c
index b3db0aa108..1ac35dd8b5 100644
--- a/src/feature/dircommon/directory.c
+++ b/src/feature/dircommon/directory.c
@@ -225,7 +225,17 @@ connection_dir_is_anonymous(const dir_connection_t *dir_conn)
     return false;
   }
 
-  /* Get the previous channel to learn if it is a client or relay link. */
+  /* It is possible that the circuit was closed because one of the channel was
+   * closed or a DESTROY cell was received. Either way, this connection can
+   * not continue so return that it is not anonymous since we can not know for
+   * sure if it is. */
+  if (circ->marked_for_close) {
+    return false;
+  }
+
+  /* Get the previous channel to learn if it is a client or relay link. We
+   * BUG() because if the circuit is not mark for close, we ought to have a
+   * p_chan else we have a code flow issue. */
   if (BUG(CONST_TO_OR_CIRCUIT(circ)->p_chan == NULL)) {
     log_info(LD_DIR, "Rejected HSDir request: no p_chan");
     return false;