1 files changed, 61 insertions, 0 deletions
diff --git a/include/hkdf.h b/include/hkdf.h
new file mode 100644
index 0000000..460e203
--- /dev/null
+++ b/include/hkdf.h
@@ -0,0 +1,61 @@
+/*
+* Copyright (c) 2024 Vaughn Nugent
+*
+* Package: noscrypt
+* File: hkdf.h
+*
+* This library is free software; you can redistribute it and/or
+* modify it under the terms of the GNU Lesser General Public License
+* as published by the Free Software Foundation; either version 2.1
+* of the License, or  (at your option) any later version.
+*
+* This library is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+* Lesser General Public License for more details.
+*
+* You should have received a copy of the GNU Lesser General Public License
+* along with noscrypt. If not, see http://www.gnu.org/licenses/.
+*/
+
+#pragma once
+
+#ifndef _NC_HKDF_H
+#define _NC_HKDF_H
+
+#include "nc-util.h"
+#include "nc-crypto.h"
+
+/*
+* IMPORTANT:
+*	The HKDF_IN_BUF_SIZE defintion sets the internal stack buffer size to use
+*	during fallback HKDF_Expand operations.
+*
+*	128 bytes should be more than enough for most use cases, without going 
+*	overboard. Could be dialed in better for specific use cases later.
+*/
+
+#ifndef HKDF_IN_BUF_SIZE
+	#define HKDF_IN_BUF_SIZE	0x80	
+#endif
+
+
+/* typedefs for hdkf callback functions */
+
+typedef cstatus_t (*hmac_hash_func)(void* ctx, const cspan_t* data);
+typedef cstatus_t (*hmac_finish_fn)(void* ctx, sha256_t hmacOut32);
+
+struct nc_hkdf_fn_cb_struct
+{
+	hmac_hash_func update;
+	hmac_finish_fn finish;
+};
+
+cstatus_t hkdfExpandProcess(
+	const struct nc_hkdf_fn_cb_struct* handler,
+	void* ctx,
+	const cspan_t* info,
+	span_t* okm
+);
+
+#endif /* !_NC_HKDF_H */