1 files changed, 31 insertions, 0 deletions
diff --git a/pigeonhole/src/lib-sieve/plugins/special-use/ext-special-use-common.c b/pigeonhole/src/lib-sieve/plugins/special-use/ext-special-use-common.c
new file mode 100644
index 0000000..fcaf1b5
--- /dev/null
+++ b/pigeonhole/src/lib-sieve/plugins/special-use/ext-special-use-common.c
@@ -0,0 +1,31 @@
+/* Copyright (c) 2019 Pigeonhole authors, see the included COPYING file */
+
+#include "lib.h"
+#include "imap-arg.h"
+
+#include "ext-special-use-common.h"
+
+bool ext_special_use_flag_valid(const char *flag)
+{
+	const char *p = flag;
+
+	/* RFC 6154, Section 6:
+
+	   use-attr        =  "\All" / "\Archive" / "\Drafts" / "\Flagged" /
+	                      "\Junk" / "\Sent" / "\Trash" / use-attr-ext
+	   use-attr-ext    =  "\" atom
+	 */
+
+	/* "\" */
+	if (*p != '\\')
+		return FALSE;
+	p++;
+
+	/* atom */
+	for (; *p != '\0'; p++) {
+		if (!IS_ATOM_CHAR(*p))
+			return FALSE;
+	}
+
+	return TRUE;
+}