Remove long-obsolete members from the state file.

Tor has a feature to preserve unrecognized state file entries in
order to maintain forward compatibility.  But this feature, along
with some unused code that we never actually removed, led to us
keeping items that were of no use to the user, other than at worst
to preserve ancient information about them.

This commit adds a feature to remove obsolete entries when we load
the file.

Closes ticket 40137.

1 files changed, 56 insertions, 0 deletions

diff --git a/src/test/test_statefile.c b/src/test/test_statefile.c
new file mode 100644
index 0000000000..dc9ecfee3e
--- /dev/null
+++ b/src/test/test_statefile.c
@@ -0,0 +1,56 @@
+/* Copyright (c) 2001-2004, Roger Dingledine.
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2020, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#include "orconfig.h"
+
+#define STATEFILE_PRIVATE
+
+#include "core/or/or.h"
+#include "lib/encoding/confline.h"
+#include "app/config/statefile.h"
+
+#include "test/test.h"
+
+static void
+test_statefile_remove_obsolete(void *arg)
+{
+  (void)arg;
+  config_line_t *inp = NULL;
+  /* try empty config */
+  or_state_remove_obsolete_lines(&inp);
+  tt_assert(!inp);
+
+  /* try removing every line */
+  config_line_append(&inp, "EntryGuard", "doesn't matter");
+  config_line_append(&inp, "HidServRevCounter", "ignore");
+  config_line_append(&inp, "hidservrevcounter", "foobar"); // note case
+  or_state_remove_obsolete_lines(&inp);
+  tt_assert(!inp);
+
+  /* Now try removing a subset of lines. */
+  config_line_append(&inp, "EntryGuard", "doesn't matter");
+  config_line_append(&inp, "Guard", "in use");
+  config_line_append(&inp, "HidServRevCounter", "ignore");
+  config_line_append(&inp, "TorVersion", "this test doesn't care");
+  or_state_remove_obsolete_lines(&inp);
+  tt_assert(inp);
+  tt_str_op(inp->key, OP_EQ, "Guard");
+  tt_str_op(inp->value, OP_EQ, "in use");
+  tt_assert(inp->next);
+  tt_str_op(inp->next->key, OP_EQ, "TorVersion");
+  tt_str_op(inp->next->value, OP_EQ, "this test doesn't care");
+  tt_assert(! inp->next->next);
+
+ done:
+  config_free_lines(inp);
+}
+
+#define T(name) \
+  { #name, test_statefile_##name, 0, NULL, NULL }
+
+struct testcase_t statefile_tests[] = {
+  T(remove_obsolete),
+  END_OF_TESTCASES
+};