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-rw-r--r--hmac/libkeccak_hmac_fast_digest.c78
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;
+}