1 files changed, 53 insertions, 0 deletions
diff --git a/hmac_init.c b/hmac_init.c
new file mode 100644
index 0000000..c16998a
--- /dev/null
+++ b/hmac_init.c
@@ -0,0 +1,53 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+/**
+ * Initialise an HMAC state
+ * 
+ * @param   state        The state that should be initialised
+ * @param   algorithm    The hashing algorithm
+ * @param   key          The key
+ * @param   key_length   The length of key, in bits
+ * @return               Zero on success, -1 on error
+ */
+int
+libsha1_hmac_init(struct libsha1_hmac_state *restrict state, enum libsha1_algorithm algorithm,
+                  const void *restrict key_, size_t keylen)
+{
+	const unsigned char *restrict key = key_;
+	size_t i;
+
+	state->sha1_state.algorithm = algorithm;
+	state->outsize = libsha1_algorithm_output_size(algorithm) * 8;
+	if (!state->outsize) {
+		errno = EINVAL;
+		return -1;
+	}
+	state->inited = 0;
+
+	if (keylen <= 64 * 8) {
+		memset(state->ipad, 0x36, sizeof(state->ipad));
+		memset(state->opad, 0x5C, sizeof(state->opad));
+		for (i = 0; i < keylen / 8; i++) {
+			state->ipad[i] ^= key[i];
+			state->opad[i] ^= key[i];
+		}
+		if (keylen & 7) {
+			state->ipad[i] ^= (unsigned char)(key[i] << (8 - (keylen & 7)));
+			state->opad[i] ^= (unsigned char)(key[i] << (8 - (keylen & 7)));
+		}
+	} else {
+		memset(state->ipad, 0, sizeof(state->ipad));
+		if (libsha1_init(&state->sha1_state, algorithm))
+			return -1;
+		libsha1_digest(&state->sha1_state, key, keylen, state->ipad);
+		memcpy(state->opad, state->ipad, sizeof(state->ipad));
+		for (i = 0; i < sizeof(state->ipad); i++) {
+			state->ipad[i] ^= 0x36;
+			state->opad[i] ^= 0x5C;
+		}
+	}
+
+	return 0;
+}