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/* backport of cfb.c for CFB8
Cipher feedback mode.
Copyright (C) 2015, 2017 Dmitry Eremin-Solenikov
Copyright (C) 2001, 2011 Niels Möller
This file is part of GNU Nettle.
GNU Nettle is free software: you can redistribute it and/or
modify it under the terms of either:
* the GNU Lesser General Public License as published by the Free
Software Foundation; either version 3 of the License, or (at your
option) any later version.
or
* the GNU General Public License as published by the Free
Software Foundation; either version 2 of the License, or (at your
option) any later version.
or both in parallel, as here.
GNU Nettle is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received copies of the GNU General Public License and
the GNU Lesser General Public License along with this program. If
not, see https://www.gnu.org/licenses/.
*/
/* #############################################
* THIS IS A BACKPORT FROM NETTLE, DO NOT MODIFY
* #############################################
*/
#ifndef HAVE_NETTLE_CFB8_ENCRYPT
#include "cfb8.h"
#include <string.h>
#include <nettle/memxor.h>
/* CFB-8 uses slight optimization: it encrypts or decrypts up to block_size
* bytes and does memcpy/memxor afterwards */
void
cfb8_encrypt(const void *ctx, nettle_cipher_func *f,
size_t block_size, uint8_t *iv,
size_t length, uint8_t *dst,
const uint8_t *src)
{
TMP_DECL(buffer, uint8_t, NETTLE_MAX_CIPHER_BLOCK_SIZE * 2);
TMP_DECL(outbuf, uint8_t, NETTLE_MAX_CIPHER_BLOCK_SIZE);
TMP_ALLOC(buffer, block_size * 2);
TMP_ALLOC(outbuf, block_size);
uint8_t pos;
memcpy(buffer, iv, block_size);
pos = 0;
while (length)
{
uint8_t t;
if (pos == block_size)
{
memcpy(buffer, buffer + block_size, block_size);
pos = 0;
}
f(ctx, block_size, outbuf, buffer + pos);
t = *(dst++) = *(src++) ^ outbuf[0];
buffer[pos + block_size] = t;
length--;
pos ++;
}
memcpy(iv, buffer + pos, block_size);
}
void
cfb8_decrypt(const void *ctx, nettle_cipher_func *f,
size_t block_size, uint8_t *iv,
size_t length, uint8_t *dst,
const uint8_t *src)
{
TMP_DECL(buffer, uint8_t, NETTLE_MAX_CIPHER_BLOCK_SIZE * 2);
TMP_DECL(outbuf, uint8_t, NETTLE_MAX_CIPHER_BLOCK_SIZE * 2);
TMP_ALLOC(buffer, block_size * 2);
TMP_ALLOC(outbuf, block_size * 2);
uint8_t i = 0;
memcpy(buffer, iv, block_size);
memcpy(buffer + block_size, src,
length < block_size ? length : block_size);
while (length)
{
for (i = 0; i < length && i < block_size; i++)
f(ctx, block_size, outbuf + i, buffer + i);
memxor3(dst, src, outbuf, i);
length -= i;
src += i;
dst += i;
memcpy(buffer, buffer + block_size, block_size);
memcpy(buffer + block_size, src,
length < block_size ? length : block_size);
}
memcpy(iv, buffer + i, block_size);
}
#endif /* HAVE_NETTLE_CFB8_ENCRYPT */
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