lilcrypto/kdf_hkdf.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 <string.h>
#include "internal.h"
static int
hkdf_kdf(uint8_t *out, size_t *outlen, void *initparams, size_t len)
{
struct lc_hkdf_params *params = initparams;
struct lc_hmac_params hmacparams;
uint8_t prk[HMAC_HASHLEN_MAX];
uint8_t t[HMAC_HASHLEN_MAX], tn[HMAC_HASHLEN_MAX];
size_t hashlen, olen;
uint8_t ctr;
/* Only accept HMAC as auth_impl. */
if (params->hmac == NULL ||
params->hmac->impl != lc_auth_impl_hmac())
return 0;
hashlen = params->hash->impl->hashlen;
/* XXX *outlen = 0 ? */
if (len > hashlen * 255)
return 0;
if (out == NULL) {
*outlen = len;
return 1;
}
*outlen = 0;
hmacparams.hash = params->hash;
if (params->saltlen == 0) {
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hmacparams.key = zerobuf;
hmacparams.keylen = hashlen;
} else {
hmacparams.key = params->salt;
hmacparams.keylen = params->saltlen;
}
if (!lc_auth(params->hmac->impl, prk, &olen, &hmacparams, params->ikm,
params->ikmlen))
return 0;
hmacparams.key = prk;
hmacparams.keylen = olen;
olen = 0;
ctr = 1;
while (len >= hashlen) {
memcpy(t, tn, olen);
if (!lc_auth_init(params->hmac, &hmacparams) ||
!lc_auth_update(params->hmac, t, olen) ||
!lc_auth_update(params->hmac, params->info,
params->infolen) ||
!lc_auth_update(params->hmac, &ctr, sizeof(ctr)) ||
!lc_auth_final(params->hmac, tn, &olen))
return 0;
ctr++;
memcpy(out, tn, hashlen);
*outlen += hashlen;
out += hashlen;
len -= hashlen;
}
memcpy(t, tn, olen);
if (!lc_auth_init(params->hmac, &hmacparams) ||
!lc_auth_update(params->hmac, t, olen) ||
!lc_auth_update(params->hmac, params->info, params->infolen) ||
!lc_auth_update(params->hmac, &ctr, sizeof(ctr)) ||
!lc_auth_final(params->hmac, tn, &olen))
return 0;
memcpy(out, tn, len);
*outlen += len;
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lc_scrub(prk, sizeof(prk));
return 1;
}
const struct lc_kdf_impl *
lc_kdf_impl_hkdf(void)
{
static struct lc_kdf_impl hkdf_impl = {
.kdf = &hkdf_kdf,
};
return &hkdf_impl;
}