sendme: Never fallback to v0 if unknown version

There was a missing cell version check against our max supported version. In
other words, we do not fallback to v0 anymore in case we do know the SENDME
version.

We can either handle it or not, never fallback to the unauthenticated version
in order to avoid gaming the authenticated logic.

Add a unit tests making sure we properly test that and also test that we can
always handle the default emit and accepted versions.

Fixes #30428

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

1 files changed, 31 insertions, 2 deletions

diff --git a/src/test/test_sendme.c b/src/test/test_sendme.c
index 463a0ec086..a36c904c28 100644
--- a/src/test/test_sendme.c
+++ b/src/test/test_sendme.c
@@ -122,9 +122,9 @@ test_v1_consensus_params(void *arg)
   smartlist_add(current_md_consensus->net_params,
                 (void *) "sendme_accept_min_version=1");
   /* Minimum acceptable value is 1. */
-  tt_int_op(cell_version_is_valid(1), OP_EQ, true);
+  tt_int_op(cell_version_can_be_handled(1), OP_EQ, true);
   /* Minimum acceptable value is 1 so a cell version of 0 is refused. */
-  tt_int_op(cell_version_is_valid(0), OP_EQ, false);
+  tt_int_op(cell_version_can_be_handled(0), OP_EQ, false);
 
  done:
   free_mock_consensus();
@@ -239,6 +239,33 @@ test_cell_payload_pad(void *arg)
   ;
 }
 
+static void
+test_cell_version_validation(void *arg)
+{
+  (void) arg;
+
+  /* We currently only support up to SENDME_MAX_SUPPORTED_VERSION so we are
+   * going to test the boundaries there. */
+
+  tt_assert(cell_version_can_be_handled(SENDME_MAX_SUPPORTED_VERSION));
+
+  /* Version below our supported should pass. */
+  tt_assert(cell_version_can_be_handled(SENDME_MAX_SUPPORTED_VERSION - 1));
+
+  /* Extra version from our supported should fail. */
+  tt_assert(!cell_version_can_be_handled(SENDME_MAX_SUPPORTED_VERSION + 1));
+
+  /* Simple check for version 0. */
+  tt_assert(cell_version_can_be_handled(0));
+
+  /* We MUST handle the default cell version that we emit or accept. */
+  tt_assert(cell_version_can_be_handled(SENDME_EMIT_MIN_VERSION_DEFAULT));
+  tt_assert(cell_version_can_be_handled(SENDME_ACCEPT_MIN_VERSION_DEFAULT));
+
+ done:
+  ;
+}
+
 struct testcase_t sendme_tests[] = {
   { "v1_record_digest", test_v1_record_digest, TT_FORK,
     NULL, NULL },
@@ -248,6 +275,8 @@ struct testcase_t sendme_tests[] = {
     NULL, NULL },
   { "cell_payload_pad", test_cell_payload_pad, TT_FORK,
     NULL, NULL },
+  { "cell_version_validation", test_cell_version_validation, TT_FORK,
+    NULL, NULL },
 
   END_OF_TESTCASES
 };