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/* $OpenBSD: ctr128.c,v 1.7 2017/08/13 17:46:24 bcook Exp $ */
/* ====================================================================
* Copyright (c) 2008 The OpenSSL Project. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. All advertising materials mentioning features or use of this
* software must display the following acknowledgment:
* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
*
* 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
* endorse or promote products derived from this software without
* prior written permission. For written permission, please contact
* openssl-core@openssl.org.
*
* 5. Products derived from this software may not be called "OpenSSL"
* nor may "OpenSSL" appear in their names without prior written
* permission of the OpenSSL Project.
*
* 6. Redistributions of any form whatsoever must retain the following
* acknowledgment:
* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit (http://www.openssl.org/)"
*
* THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
* ====================================================================
*
*/
#include <openssl/crypto.h>
#include "modes_lcl.h"
#include <string.h>
#ifndef MODES_DEBUG
# ifndef NDEBUG
# define NDEBUG
# endif
#endif
#include <assert.h>
/* NOTE: the IV/counter CTR mode is big-endian. The code itself
* is endian-neutral. */
/* increment counter (128-bit int) by 1 */
static void ctr128_inc(unsigned char *counter) {
u32 n=16;
u8 c;
do {
--n;
c = counter[n];
++c;
counter[n] = c;
if (c) return;
} while (n);
}
#if !defined(OPENSSL_SMALL_FOOTPRINT)
static void
ctr128_inc_aligned(unsigned char *counter)
{
#if BYTE_ORDER == LITTLE_ENDIAN
ctr128_inc(counter);
#else
size_t *data, c, n;
data = (size_t *)counter;
n = 16 / sizeof(size_t);
do {
--n;
c = data[n];
++c;
data[n] = c;
if (c)
return;
} while (n);
#endif
}
#endif
/* The input encrypted as though 128bit counter mode is being
* used. The extra state information to record how much of the
* 128bit block we have used is contained in *num, and the
* encrypted counter is kept in ecount_buf. Both *num and
* ecount_buf must be initialised with zeros before the first
* call to CRYPTO_ctr128_encrypt().
*
* This algorithm assumes that the counter is in the x lower bits
* of the IV (ivec), and that the application has full control over
* overflow and the rest of the IV. This implementation takes NO
* responsability for checking that the counter doesn't overflow
* into the rest of the IV when incremented.
*/
void CRYPTO_ctr128_encrypt(const unsigned char *in, unsigned char *out,
size_t len, const void *key,
unsigned char ivec[16], unsigned char ecount_buf[16],
unsigned int *num, block128_f block)
{
unsigned int n;
size_t l=0;
assert(*num < 16);
n = *num;
#if !defined(OPENSSL_SMALL_FOOTPRINT)
if (16%sizeof(size_t) == 0) do { /* always true actually */
while (n && len) {
*(out++) = *(in++) ^ ecount_buf[n];
--len;
n = (n+1) % 16;
}
#ifdef __STRICT_ALIGNMENT
if (((size_t)in|(size_t)out|(size_t)ivec)%sizeof(size_t) != 0)
break;
#endif
while (len>=16) {
(*block)(ivec, ecount_buf, key);
ctr128_inc_aligned(ivec);
for (; n<16; n+=sizeof(size_t))
*(size_t *)(out+n) =
*(size_t *)(in+n) ^ *(size_t *)(ecount_buf+n);
len -= 16;
out += 16;
in += 16;
n = 0;
}
if (len) {
(*block)(ivec, ecount_buf, key);
ctr128_inc_aligned(ivec);
while (len--) {
out[n] = in[n] ^ ecount_buf[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, ecount_buf, key);
ctr128_inc(ivec);
}
out[l] = in[l] ^ ecount_buf[n];
++l;
n = (n+1) % 16;
}
*num=n;
}
/* increment upper 96 bits of 128-bit counter by 1 */
static void ctr96_inc(unsigned char *counter) {
u32 n=12;
u8 c;
do {
--n;
c = counter[n];
++c;
counter[n] = c;
if (c) return;
} while (n);
}
void CRYPTO_ctr128_encrypt_ctr32(const unsigned char *in, unsigned char *out,
size_t len, const void *key,
unsigned char ivec[16], unsigned char ecount_buf[16],
unsigned int *num, ctr128_f func)
{
unsigned int n,ctr32;
assert(*num < 16);
n = *num;
while (n && len) {
*(out++) = *(in++) ^ ecount_buf[n];
--len;
n = (n+1) % 16;
}
ctr32 = GETU32(ivec+12);
while (len>=16) {
size_t blocks = len/16;
/*
* 1<<28 is just a not-so-small yet not-so-large number...
* Below condition is practically never met, but it has to
* be checked for code correctness.
*/
if (sizeof(size_t)>sizeof(unsigned int) && blocks>(1U<<28))
blocks = (1U<<28);
/*
* As (*func) operates on 32-bit counter, caller
* has to handle overflow. 'if' below detects the
* overflow, which is then handled by limiting the
* amount of blocks to the exact overflow point...
*/
ctr32 += (u32)blocks;
if (ctr32 < blocks) {
blocks -= ctr32;
ctr32 = 0;
}
(*func)(in,out,blocks,key,ivec);
/* (*ctr) does not update ivec, caller does: */
PUTU32(ivec+12,ctr32);
/* ... overflow was detected, propogate carry. */
if (ctr32 == 0) ctr96_inc(ivec);
blocks *= 16;
len -= blocks;
out += blocks;
in += blocks;
}
if (len) {
memset(ecount_buf,0,16);
(*func)(ecount_buf,ecount_buf,1,key,ivec);
++ctr32;
PUTU32(ivec+12,ctr32);
if (ctr32 == 0) ctr96_inc(ivec);
while (len--) {
out[n] = in[n] ^ ecount_buf[n];
++n;
}
}
*num=n;
}
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