/*
* Copyright 2008-2020 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <openssl/crypto.h>
#include "modes_local.h"
#include <string.h>
#if defined(__GNUC__) && !defined(STRICT_ALIGNMENT)
typedef size_t size_t_aX __attribute((__aligned__(1)));
#else
typedef size_t size_t_aX;
#endif
/*
* The input and output encrypted as though 128bit cfb mode is being used.
* The extra state information to record how much of the 128bit block we have
* used is contained in *num;
*/
void CRYPTO_cfb128_encrypt(const unsigned char *in, unsigned char *out,
size_t len, const void *key,
unsigned char ivec[16], int *num,
int enc, block128_f block)
{
unsigned int n;
size_t l = 0;
n = *num;
if (enc) {
#if !defined(OPENSSL_SMALL_FOOTPRINT)
if (16 % sizeof(size_t) == 0) { /* always true actually */
do {
while (n && len) {
*(out++) = ivec[n] ^= *(in++);
--len;
n = (n + 1) % 16;
}
# if defined(STRICT_ALIGNMENT)
if (((size_t)in | (size_t)out | (size_t)ivec) %
sizeof(size_t) != 0)
break;
# endif
while (len >= 16) {
(*block) (ivec, ivec, key);
for (; n < 16; n += sizeof(size_t)) {
*(size_t_aX *)(out + n) =
*(size_t_aX *)(ivec + n)
^= *(size_t_aX *)(in + n);
}
len -= 16;
out += 16;
in += 16;
n = 0;
}
if (len) {
(*block) (ivec, ivec, key);
while (len--) {
out[n] = ivec[n] ^= in[n];
++n;
}
}
*num = n;
return;
} while (0);
}
/* the rest would be commonly eliminated by x86* compiler */
#endif
while (l < len) {
if (n == 0) {
(*block) (ivec, ivec, key);
}
out[l] = ivec[n] ^= in[l];
++l;
n = (n + 1) % 16;
}
*num = n;
} else {
#if !defined(OPENSSL_SMALL_FOOTPRINT)
if (16 % sizeof(size_t) == 0) { /* always true actually */
do {
while (n && len) {
unsigned char c;
*(out++) = ivec[n] ^ (c = *(in++));
ivec[n] = c;
--len;
n = (n + 1) % 16;
}
# if defined(STRICT_ALIGNMENT)
if (((size_t)in | (size_t)out | (size_t)ivec) %
sizeof(size_t) != 0)
break;
# endif
while (len >= 16) {
(*block) (ivec, ivec, key);
for (; n < 16; n += sizeof(size_t)) {
size_t t = *(size_t_aX *)(in + n);
*(size_t_aX *)(out + n)
= *(size_t_aX *)(ivec + n) ^ t;
*(size_t_aX *)(ivec + n) = t;
}
len -= 16;
out += 16;
in += 16;
n = 0;
}
if (len) {
(*block) (ivec, ivec, key);
while (len--) {
unsigned char c;
out[n] = ivec[n] ^ (c = in[n]);
ivec[n] = c;
++n;
}
}
*num = n;
return;
} while (0);
}
/* the rest would be commonly eliminated by x86* compiler */
#endif
while (l < len) {
unsigned char c;
if (n == 0) {
(*block) (ivec, ivec, key);
}
out[l] = ivec[n] ^ (c = in[l]);
ivec[n] = c;
++l;
n = (n + 1) % 16;
}
*num = n;
}
}
/*
* This expects a single block of size nbits for both in and out. Note that
* it corrupts any extra bits in the last byte of out
*/
static void cfbr_encrypt_block(const unsigned char *in, unsigned char *out,
int nbits, const void *key,
unsigned char ivec[16], int enc,
block128_f block)
{
int n, rem, num;
unsigned char ovec[16 * 2 + 1]; /* +1 because we dereference (but don't
* use) one byte off the end */
if (nbits <= 0 || nbits > 128)
return;
/* fill in the first half of the new IV with the current IV */
memcpy(ovec, ivec, 16);
/* construct the new IV */
(*block) (ivec, ivec, key);
num = (nbits + 7) / 8;
if (enc) /* encrypt the input */
for (n = 0; n < num; ++n)
out[n] = (ovec[16 + n] = in[n] ^ ivec[n]);
else /* decrypt the input */
for (n = 0; n < num; ++n)
out[n] = (ovec[16 + n] = in[n]) ^ ivec[n];
/* shift ovec left... */
rem = nbits % 8;
num = nbits / 8;
if (rem == 0)
memcpy(ivec, ovec + num, 16);
else
for (n = 0; n < 16; ++n)
ivec[n] = ovec[n + num] << rem | ovec[n + num + 1] >> (8 - rem);
/* it is not necessary to cleanse ovec, since the IV is not secret */
}
/* N.B. This expects the input to be packed, MS bit first */
void CRYPTO_cfb128_1_encrypt(const unsigned char *in, unsigned char *out,
size_t bits, const void *key,
unsigned char ivec[16], int *num,
int enc, block128_f block)
{
size_t n;
unsigned char c[1], d[1];
for (n = 0; n < bits; ++n) {
c[0] = (in[n / 8] & (1 << (7 - n % 8))) ? 0x80 : 0;
cfbr_encrypt_block(c, d, 1, key, ivec, enc, block);
out[n / 8] = (out[n / 8] & ~(1 << (unsigned int)(7 - n % 8))) |
((d[0] & 0x80) >> (unsigned int)(n % 8));
}
}
void CRYPTO_cfb128_8_encrypt(const unsigned char *in, unsigned char *out,
size_t length, const void *key,
unsigned char ivec[16], int *num,
int enc, block128_f block)
{
size_t n;
for (n = 0; n < length; ++n)
cfbr_encrypt_block(&in[n], &out[n], 8, key, ivec, enc, block);
}