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/*
* Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#include "inner.h"
const unsigned char br_hkdf_no_salt = 0;
/* see bearssl_kdf.h */
void
br_hkdf_init(br_hkdf_context *hc, const br_hash_class *digest_vtable,
const void *salt, size_t salt_len)
{
br_hmac_key_context kc;
unsigned char tmp[64];
if (salt == BR_HKDF_NO_SALT) {
salt = tmp;
salt_len = br_digest_size(digest_vtable);
memset(tmp, 0, salt_len);
}
br_hmac_key_init(&kc, digest_vtable, salt, salt_len);
br_hmac_init(&hc->u.hmac_ctx, &kc, 0);
hc->dig_len = br_hmac_size(&hc->u.hmac_ctx);
}
/* see bearssl_kdf.h */
void
br_hkdf_inject(br_hkdf_context *hc, const void *ikm, size_t ikm_len)
{
br_hmac_update(&hc->u.hmac_ctx, ikm, ikm_len);
}
/* see bearssl_kdf.h */
void
br_hkdf_flip(br_hkdf_context *hc)
{
unsigned char tmp[64];
br_hmac_out(&hc->u.hmac_ctx, tmp);
br_hmac_key_init(&hc->u.prk_ctx,
br_hmac_get_digest(&hc->u.hmac_ctx), tmp, hc->dig_len);
hc->ptr = hc->dig_len;
hc->chunk_num = 0;
}
/* see bearssl_kdf.h */
size_t
br_hkdf_produce(br_hkdf_context *hc,
const void *info, size_t info_len, void *out, size_t out_len)
{
size_t tlen;
tlen = 0;
while (out_len > 0) {
size_t clen;
if (hc->ptr == hc->dig_len) {
br_hmac_context hmac_ctx;
unsigned char x;
hc->chunk_num ++;
if (hc->chunk_num == 256) {
return tlen;
}
x = hc->chunk_num;
br_hmac_init(&hmac_ctx, &hc->u.prk_ctx, 0);
if (x != 1) {
br_hmac_update(&hmac_ctx, hc->buf, hc->dig_len);
}
br_hmac_update(&hmac_ctx, info, info_len);
br_hmac_update(&hmac_ctx, &x, 1);
br_hmac_out(&hmac_ctx, hc->buf);
hc->ptr = 0;
}
clen = hc->dig_len - hc->ptr;
if (clen > out_len) {
clen = out_len;
}
memcpy(out, hc->buf + hc->ptr, clen);
out = (unsigned char *)out + clen;
out_len -= clen;
hc->ptr += clen;
tlen += clen;
}
return tlen;
}
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