1 files changed, 27 insertions, 22 deletions

diff --git a/libkeccak_hmac_unmarshal.c b/libkeccak_hmac_unmarshal.c
index 9627f1e..452efa3 100644
--- a/libkeccak_hmac_unmarshal.c
+++ b/libkeccak_hmac_unmarshal.c
@@ -5,7 +5,8 @@
 /**
  * Unmarshal a `struct libkeccak_hmac_state` from a buffer
  * 
- * @param   state  The slot for the unmarshalled state, must not be initialised (memory leak otherwise)
+ * @param   state  The slot for the unmarshalled state, must not be
+ *                 initialised (memory leak otherwise), can be `NULL`
  * @param   data   The input buffer
  * @return         The number of bytes read from `data`, 0 on error
  */
@@ -18,33 +19,37 @@ libkeccak_hmac_unmarshal(struct libkeccak_hmac_state *restrict state, const void
 	state->key_opad = NULL;
 	state->key_ipad = NULL;
 
-	parsed = libkeccak_state_unmarshal(&state->sponge, data);
-	if (parsed == 0)
+	parsed = libkeccak_state_unmarshal(state ? &state->sponge : NULL, data);
+	if (!parsed)
 		return 0;
-
 	data += parsed / sizeof(char);
-	state->key_length = *(const size_t *)data;
+
+	size = *(const size_t *)data;
 	data += sizeof(size_t) / sizeof(char);
+	if (state)
+		size = state->key_length;
 	size = (state->key_length + 7) >> 3;
 
-	state->key_opad = malloc(2 * size);
-	if (!state->key_opad) {
-		libkeccak_state_destroy(&state->sponge);
-		return 0;
+	if (state) {
+		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;
 	}
-	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);
 }