ctl/filestore: Add check for filestore directory

Up until now, suricatactl would delete any directory that is provided as
an argument on command line. This patch adds a basic test for the
directories `tmp`, `00` and `ff` in order to justify that the provided
directory is actually a filestore directory.

Additionally, some code has been broken up and made more readable and
pythonic.

Closes redmine ticket #2843

python/suricata/ctl/filestore.py

@@ -82,22 +82,32 @@ def remove_file(path, dry_run):
     return size
 
 
-def prune(args):
+def set_logger_level(args):
     if args.verbose:
         logger.setLevel(logging.DEBUG)
     if args.quiet:
         logger.setLevel(logging.WARNING)
 
-    if not args.directory:
-        print(
-            "error: the filestore directory must be provided with --directory",
-            file=sys.stderr)
-        return 1
 
-    if not args.age:
-        print("error: no age provided, nothing to do", file=sys.stderr)
-        return 1
+def perform_sanity_checks(args):
+    set_logger_level(args)
+    err_msg = {
+            "directory": "filestore directory must be provided",
+            "age": "no age provided, nothing to do",
+            }
+    for val, msg in err_msg.items():
+        if not getattr(args, val):
+            print("Error: {}".format(msg), file=sys.stderr)
+            sys.exit(1)
+    required_dirs = ["tmp", "00", "ff"]
+    for required_dir in required_dirs:
+        if not os.path.exists(os.path.join(args.directory, required_dir)):
+            logger.error("Provided directory is not a filestore directory")
+            sys.exit(1)
+
 
+def prune(args):
+    perform_sanity_checks(args)
     age = parse_age(args.age)
     now = time.time()
     size = 0