Fix bug when %including folder with comment only files. #31408

When processing a %included folder, a bug caused the pointer to
the last element of the options list to be set to NULL when
processing a file with only comments or whitepace. This could
cause options from other files on the same folder to be
discarded depending on the lines after the affected %include.

2 files changed, 74 insertions, 4 deletions

diff --git a/src/lib/fs/conffile.c b/src/lib/fs/conffile.c
index 7bb2f23931..0d5d56b335 100644
--- a/src/lib/fs/conffile.c
+++ b/src/lib/fs/conffile.c
@@ -153,16 +153,18 @@ config_process_include(const char *path, int recursion_level, int extended,
   int rv = -1;
   SMARTLIST_FOREACH_BEGIN(config_files, const char *, config_file) {
     config_line_t *included_config = NULL;
+    config_line_t *included_config_last = NULL;
     if (config_get_included_config(config_file, recursion_level, extended,
-                                   &included_config, list_last,
+                                   &included_config, &included_config_last,
                                    opened_lst) < 0) {
       goto done;
     }
 
     *next = included_config;
-    if (*list_last)
-      next = &(*list_last)->next;
-
+    if (included_config_last) {
+      next = &included_config_last->next;
+      *list_last = included_config_last;
+    }
   } SMARTLIST_FOREACH_END(config_file);
   *list = ret_list;
   rv = 0;
diff --git a/src/test/test_config.c b/src/test/test_config.c
index 0de6b12919..8f011ce1f1 100644
--- a/src/test/test_config.c
+++ b/src/test/test_config.c
@@ -5287,6 +5287,73 @@ test_config_include_folder_order(void *data)
 }
 
 static void
+test_config_include_blank_file_last(void *data)
+{
+  (void)data;
+
+  config_line_t *result = NULL;
+  char *torrcd = NULL;
+  char *path = NULL;
+  char *dir = tor_strdup(get_fname("test_include_blank_file_last"));
+  tt_ptr_op(dir, OP_NE, NULL);
+
+#ifdef _WIN32
+  tt_int_op(mkdir(dir), OP_EQ, 0);
+#else
+  tt_int_op(mkdir(dir, 0700), OP_EQ, 0);
+#endif
+
+  tor_asprintf(&torrcd, "%s"PATH_SEPARATOR"%s", dir, "torrc.d");
+
+#ifdef _WIN32
+  tt_int_op(mkdir(torrcd), OP_EQ, 0);
+#else
+  tt_int_op(mkdir(torrcd, 0700), OP_EQ, 0);
+#endif
+
+  tor_asprintf(&path, "%s"PATH_SEPARATOR"%s", torrcd, "aa_1st");
+  tt_int_op(write_str_to_file(path, "Test 1\n", 0), OP_EQ, 0);
+  tor_free(path);
+
+  tor_asprintf(&path, "%s"PATH_SEPARATOR"%s", torrcd, "bb_2nd");
+  tt_int_op(write_str_to_file(path, "Test 2\n", 0), OP_EQ, 0);
+  tor_free(path);
+
+  tor_asprintf(&path, "%s"PATH_SEPARATOR"%s", torrcd, "cc_comment");
+  tt_int_op(write_str_to_file(path, "# comment only\n", 0), OP_EQ, 0);
+  tor_free(path);
+
+  char torrc_contents[1000];
+  tor_snprintf(torrc_contents, sizeof(torrc_contents),
+               "%%include %s\n"
+               "Test 3\n",
+               torrcd);
+
+  int include_used;
+  tt_int_op(config_get_lines_include(torrc_contents, &result, 0, &include_used,
+            NULL), OP_EQ, 0);
+  tt_ptr_op(result, OP_NE, NULL);
+  tt_int_op(include_used, OP_EQ, 1);
+
+  int len = 0;
+  config_line_t *next;
+  for (next = result; next != NULL; next = next->next) {
+    char expected[10];
+    tor_snprintf(expected, sizeof(expected), "%d", len + 1);
+    tt_str_op(next->key, OP_EQ, "Test");
+    tt_str_op(next->value, OP_EQ, expected);
+    len++;
+  }
+  tt_int_op(len, OP_EQ, 3);
+
+ done:
+  config_free_lines(result);
+  tor_free(torrcd);
+  tor_free(path);
+  tor_free(dir);
+}
+
+static void
 test_config_include_path_syntax(void *data)
 {
   (void)data;
@@ -5848,6 +5915,7 @@ struct testcase_t config_tests[] = {
   CONFIG_TEST(include_recursion_before_after, 0),
   CONFIG_TEST(include_recursion_after_only, 0),
   CONFIG_TEST(include_folder_order, 0),
+  CONFIG_TEST(include_blank_file_last, 0),
   CONFIG_TEST(include_path_syntax, 0),
   CONFIG_TEST(include_not_processed, 0),
   CONFIG_TEST(include_has_include, 0),