1 files changed, 50 insertions, 0 deletions
diff --git a/libkeccak_hmac_unmarshal.c b/libkeccak_hmac_unmarshal.c
new file mode 100644
index 0000000..e64cd08
--- /dev/null
+++ b/libkeccak_hmac_unmarshal.c
@@ -0,0 +1,50 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+/**
+ * Unmarshal a `libkeccak_hmac_state_t` from a buffer
+ * 
+ * @param   state  The slot for the unmarshalled state, must not be initialised (memory leak otherwise)
+ * @param   data   The input buffer
+ * @return         The number of bytes read from `data`, 0 on error
+ */
+size_t
+libkeccak_hmac_unmarshal(libkeccak_hmac_state_t *restrict state, const void *restrict data_)
+{
+	const char *restrict data = data_;
+	size_t parsed, size, i;
+
+	state->key_opad = NULL;
+	state->key_ipad = NULL;
+
+	parsed = libkeccak_state_unmarshal(&state->sponge, data);
+	if (parsed == 0)
+		return 0;
+
+	data += parsed / sizeof(char);
+	state->key_length = *(const size_t *)data;
+	data += sizeof(size_t) / sizeof(char);
+	size = (state->key_length + 7) >> 3;
+
+	state->key_opad = malloc(2 * size);
+	if (!state->key_opad) {
+		libkeccak_state_destroy(&state->sponge);
+		return 0;
+	}
+	memcpy(state->key_opad, data, size);
+	data += size / sizeof(char);
+
+	if (data[0]) {
+		state->key_ipad = state->key_opad + size / sizeof(char);
+		memcpy(state->key_ipad, state->key_opad, size);
+		for (i = 0; i < size / sizeof(char); i++)
+			state->key_ipad[i] ^= (char)(HMAC_OUTER_PAD ^ HMAC_INNER_PAD);
+	}
+
+	state->leftover = data[1];
+	state->buffer = NULL;
+	state->buffer_size = 0;
+
+	return parsed + sizeof(size_t) + size + 2 * sizeof(char);
+}