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/*
* Copyright (c) 2016 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"
/* see bearssl_block.h */
void
br_aes_small_ctr_init(br_aes_small_ctr_keys *ctx,
const void *key, size_t len)
{
ctx->vtable = &br_aes_small_ctr_vtable;
ctx->num_rounds = br_aes_keysched(ctx->skey, key, len);
}
static void
xorbuf(void *dst, const void *src, size_t len)
{
unsigned char *d;
const unsigned char *s;
d = dst;
s = src;
while (len -- > 0) {
*d ++ ^= *s ++;
}
}
/* see bearssl_block.h */
uint32_t
br_aes_small_ctr_run(const br_aes_small_ctr_keys *ctx,
const void *iv, uint32_t cc, void *data, size_t len)
{
unsigned char *buf;
buf = data;
while (len > 0) {
unsigned char tmp[16];
memcpy(tmp, iv, 12);
br_enc32be(tmp + 12, cc ++);
br_aes_small_encrypt(ctx->num_rounds, ctx->skey, tmp);
if (len <= 16) {
xorbuf(buf, tmp, len);
break;
}
xorbuf(buf, tmp, 16);
buf += 16;
len -= 16;
}
return cc;
}
/* see bearssl_block.h */
const br_block_ctr_class br_aes_small_ctr_vtable = {
sizeof(br_aes_small_ctr_keys),
16,
4,
(void (*)(const br_block_ctr_class **, const void *, size_t))
&br_aes_small_ctr_init,
(uint32_t (*)(const br_block_ctr_class *const *,
const void *, uint32_t, void *, size_t))
&br_aes_small_ctr_run
};
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