1 files changed, 31 insertions, 0 deletions
diff --git a/lib/cookies/nonce.h b/lib/cookies/nonce.h
new file mode 100644
index 0000000..6c2970f
--- /dev/null
+++ b/lib/cookies/nonce.h
@@ -0,0 +1,31 @@
+/*  Copyright (C) CZ.NIC, z.s.p.o. <knot-resolver@labs.nic.cz>
+ *  SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#pragma once
+
+#include "lib/defines.h"
+
+/* RFC7873 Appendix B.2 mentions an algorithm using two values before the
+ * actual server cookie hash. */
+
+/** Nonce value length. */
+#define KR_NONCE_LEN 8
+
+/** Input data to generate nonce from. */
+struct kr_nonce_input {
+	uint32_t rand; /**< some random value */
+	uint32_t time; /**< time stamp */
+};
+
+/**
+ * @brief Writes server cookie nonce value into given buffer.
+ *
+ * @param buf     buffer to write nonce data in wire format into
+ * @param buf_len buffer size
+ * @param input   data to generate wire data from
+ * @return non-zero size of written data on success, 0 on failure
+ */
+KR_EXPORT
+uint16_t kr_nonce_write_wire(uint8_t *buf, uint16_t buf_len,
+                             const struct kr_nonce_input *input);