1 files changed, 78 insertions, 0 deletions
diff --git a/hmac/libkeccak_hmac_fast_digest.c b/hmac/libkeccak_hmac_fast_digest.c
new file mode 100644
index 0000000..dc98136
--- /dev/null
+++ b/hmac/libkeccak_hmac_fast_digest.c
@@ -0,0 +1,78 @@
+/* See LICENSE file for copyright and license details. */
+#include "../common.h"
+
+
+/**
+ * Absorb the last part of the message and fetch the hash
+ * without wiping sensitive data when possible
+ * 
+ * You may use `&state->sponge` for continued squeezing
+ * 
+ * @param   state    The hashing state
+ * @param   msg_     The rest of the message, may be `NULL`, may be modified
+ * @param   msglen   The length of the partial message
+ * @param   bits     The number of bits at the end of the message not covered by `msglen`
+ * @param   suffix   The suffix concatenate to the message, only '1':s and '0':s, and NUL-termination
+ * @param   hashsum  Output parameter for the hashsum, may be `NULL`
+ * @return           Zero on success, -1 on error
+ */
+int
+libkeccak_hmac_fast_digest(struct libkeccak_hmac_state *restrict state, const void *restrict msg_, size_t msglen,
+                           size_t bits, const char *restrict suffix, void *restrict hashsum)
+{
+	const unsigned char *restrict msg = msg_;
+	size_t hashsize = (size_t)state->sponge.n >> 3;
+	unsigned char *tmp = malloc((size_t)((state->sponge.n + 7) >> 3) * sizeof(char));
+	unsigned char leftover[2];
+	size_t newlen;
+
+	if (!tmp)
+		return -1;
+
+	if (!(state->key_length & 7)) {
+		if (libkeccak_fast_digest(&state->sponge, msg, msglen, bits, suffix, tmp) < 0)
+			goto fail;
+		goto stage_2;
+	}
+
+	if (libkeccak_hmac_fast_update(state, msg, msglen) < 0)
+		goto fail;
+	leftover[0] = state->leftover;
+	if (bits) {
+		leftover[0] |= (unsigned char)(msg[msglen] >> (state->key_length & 7));
+		leftover[1] = (unsigned char)(msg[msglen] << (8 - (state->key_length & 7)));
+	}
+	newlen = (state->key_length & 7) + bits;
+	if (libkeccak_fast_digest(&state->sponge, leftover, newlen >> 3, newlen & 7, suffix, tmp) < 0)
+		goto fail;
+
+stage_2:
+	bits = state->sponge.n & 7;
+	state->key_ipad = state->key_opad;
+	if (libkeccak_hmac_fast_update(state, NULL, 0) < 0)
+		goto fail;
+
+	if (!(state->key_length & 7)) {
+		if (libkeccak_fast_digest(&state->sponge, tmp, hashsize, bits, suffix, hashsum) < 0)
+			goto fail;
+		goto stage_3;
+	}
+
+	if (libkeccak_hmac_fast_update(state, tmp, hashsize) < 0)
+		goto fail;
+	leftover[0] = state->leftover;
+	if (bits) {
+		leftover[0] |= (unsigned char)(tmp[hashsize] >> (state->key_length & 7));
+		leftover[1] = (unsigned char)(tmp[hashsize] << (8 - (state->key_length & 7)));
+	}
+	newlen = (state->key_length & 7) + bits;
+	if (libkeccak_fast_digest(&state->sponge, leftover, newlen >> 3, newlen & 7, suffix, tmp) < 0)
+		goto fail;
+
+stage_3:
+	free(tmp);
+	return 0;
+fail:
+	free(tmp);
+	return -1;
+}