1 files changed, 46 insertions, 0 deletions
diff --git a/libkeccak_hmac_set_key.c b/libkeccak_hmac_set_key.c
new file mode 100644
index 0000000..4f450f8
--- /dev/null
+++ b/libkeccak_hmac_set_key.c
@@ -0,0 +1,46 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+/**
+ * Change the HMAC-hashing key on the state
+ * 
+ * @param   state       The state that should be reset
+ * @param   key         The new key
+ * @param   key_length  The length of key, in bits
+ * @return              Zero on success, -1 on error
+ */
+int
+libkeccak_hmac_set_key(libkeccak_hmac_state_t *restrict state, const void *restrict key, size_t key_length)
+{
+	size_t i, size, new_key_length, key_bytes;
+	char *old;
+
+	size = (size_t)(state->sponge.r) > key_length ? (size_t)(state->sponge.r) : key_length;
+	new_key_length = size;
+	size = (size + 7) >> 3;
+	key_bytes = (key_length + 7) >> 3;
+
+	if (size != key_bytes) {
+		state->key_opad = realloc(old = state->key_opad, 2 * size);
+		if (!state->key_opad)
+			return state->key_opad = old, -1;
+		state->key_ipad = state->key_opad + size / sizeof(char);
+	}
+
+	memcpy(state->key_opad, key, key_bytes);
+	if (key_length & 7)
+		state->key_opad[(key_bytes >> 3) - 1] &= (char)((1 << (key_length & 7)) - 1);
+
+	if ((size_t)(state->sponge.r) > key_length)
+		__builtin_memset(state->key_opad + key_bytes / sizeof(char), 0, size - key_bytes);
+
+	for (i = 0; i < size; i++) {
+		state->key_ipad[i] = state->key_opad[i] ^ HMAC_INNER_PAD;
+		state->key_opad[i] ^= HMAC_OUTER_PAD;
+	}
+
+	state->key_length = new_key_length;
+
+	return 0;
+}