lilcrypto/auth_hmac.c

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/*
* Copyright (c) 2024 Lucas Gabriel Vuotto <lucas@lgv5.net>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include "internal.h"
#include "util.h"
#define HMAC_IPAD UINT8_C(0x36)
#define HMAC_OPAD UINT8_C(0x5c)
static int
hmac_init(void *arg, void *initparams)
{
struct hmac_state *state = arg;
struct lc_hmac_params *params = initparams;
uint8_t ikeypad[HMAC_BLOCKLEN_MAX];
size_t i, olen, blen, keylen;
state->hash = params->hash;
keylen = params->keylen;
blen = params->hash->impl->blocklen;
if (keylen > blen) {
if (!lc_hash(state->hash->impl, state->key, &olen, params->key,
keylen))
return 0;
keylen = olen;
} else
for (i = 0; i < keylen; i++)
state->key[i] = params->key[i];
for (i = keylen; i < blen; i++)
state->key[i] = 0;
for (i = 0; i < blen; i++)
ikeypad[i] = state->key[i] ^ HMAC_IPAD;
return lc_hash_init(state->hash) &&
lc_hash_update(state->hash, ikeypad, blen);
}
static int
hmac_update(void *arg, const uint8_t *in, size_t inlen)
{
struct hmac_state *state = arg;
return lc_hash_update(state->hash, in, inlen);
}
static int
hmac_final(void *arg, uint8_t *out, size_t *outlen)
{
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struct lc_hash_ctx *hash;
struct hmac_state *state = arg;
uint8_t m[HMAC_BLOCKLEN_MAX],
okeypad[HMAC_BLOCKLEN_MAX];
size_t i, olen, blen;
int rc;
if (out == NULL) {
*outlen = state->hash->impl->hashlen;
return 1;
}
*outlen = 0;
blen = state->hash->impl->blocklen;
for (i = 0; i < blen; i++)
okeypad[i] = state->key[i] ^ HMAC_OPAD;
rc = lc_hash_final(state->hash, m, &olen) &&
lc_hash_init(state->hash) &&
lc_hash_update(state->hash, okeypad, blen) &&
lc_hash_update(state->hash, m, olen) &&
lc_hash_final(state->hash, out, outlen);
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hash = state->hash;
lc_scrub(state, sizeof(*state));
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state->hash = hash;
return rc;
}
static int
hmac_auth(uint8_t *out, size_t *outlen, void *initparams, const uint8_t *in,
size_t inlen)
{
struct lc_hmac_params *params = initparams;
struct hmac_state state;
if (out == NULL) {
*outlen = params->hash->impl->hashlen;
return 1;
}
return hmac_init(&state, initparams) &&
hmac_update(&state, in, inlen) &&
hmac_final(&state, out, outlen);
}
const struct lc_auth_impl *
lc_auth_impl_hmac(void)
{
static struct lc_auth_impl hmac_impl = {
.init = &hmac_init,
.update = &hmac_update,
.final = &hmac_final,
.auth = &hmac_auth,
.argsz = sizeof(struct hmac_state),
.blocklen = 0,
.taglen = 0,
};
return &hmac_impl;
}