252 lines
6.7 KiB
C
252 lines
6.7 KiB
C
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/* $OpenBSD: ctr128.c,v 1.7 2017/08/13 17:46:24 bcook Exp $ */
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/* ====================================================================
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* Copyright (c) 2008 The OpenSSL Project. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* 3. All advertising materials mentioning features or use of this
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* software must display the following acknowledgment:
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* "This product includes software developed by the OpenSSL Project
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* for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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*
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* 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
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* endorse or promote products derived from this software without
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* prior written permission. For written permission, please contact
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* openssl-core@openssl.org.
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*
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* 5. Products derived from this software may not be called "OpenSSL"
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* nor may "OpenSSL" appear in their names without prior written
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* permission of the OpenSSL Project.
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*
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* 6. Redistributions of any form whatsoever must retain the following
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* acknowledgment:
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* "This product includes software developed by the OpenSSL Project
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* for use in the OpenSSL Toolkit (http://www.openssl.org/)"
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*
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* THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
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* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
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* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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* ====================================================================
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*
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*/
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#include <openssl/crypto.h>
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#include "modes_lcl.h"
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#include <string.h>
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#ifndef MODES_DEBUG
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# ifndef NDEBUG
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# define NDEBUG
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# endif
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#endif
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#include <assert.h>
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/* NOTE: the IV/counter CTR mode is big-endian. The code itself
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* is endian-neutral. */
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/* increment counter (128-bit int) by 1 */
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static void ctr128_inc(unsigned char *counter) {
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u32 n=16;
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u8 c;
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do {
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--n;
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c = counter[n];
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++c;
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counter[n] = c;
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if (c) return;
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} while (n);
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}
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#if !defined(OPENSSL_SMALL_FOOTPRINT)
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static void
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ctr128_inc_aligned(unsigned char *counter)
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{
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#if BYTE_ORDER == LITTLE_ENDIAN
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ctr128_inc(counter);
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#else
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size_t *data, c, n;
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data = (size_t *)counter;
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n = 16 / sizeof(size_t);
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do {
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--n;
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c = data[n];
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++c;
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data[n] = c;
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if (c)
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return;
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} while (n);
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#endif
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}
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#endif
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/* The input encrypted as though 128bit counter mode is being
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* used. The extra state information to record how much of the
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* 128bit block we have used is contained in *num, and the
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* encrypted counter is kept in ecount_buf. Both *num and
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* ecount_buf must be initialised with zeros before the first
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* call to CRYPTO_ctr128_encrypt().
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*
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* This algorithm assumes that the counter is in the x lower bits
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* of the IV (ivec), and that the application has full control over
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* overflow and the rest of the IV. This implementation takes NO
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* responsability for checking that the counter doesn't overflow
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* into the rest of the IV when incremented.
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*/
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void CRYPTO_ctr128_encrypt(const unsigned char *in, unsigned char *out,
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size_t len, const void *key,
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unsigned char ivec[16], unsigned char ecount_buf[16],
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unsigned int *num, block128_f block)
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{
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unsigned int n;
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size_t l=0;
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assert(*num < 16);
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n = *num;
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#if !defined(OPENSSL_SMALL_FOOTPRINT)
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if (16%sizeof(size_t) == 0) do { /* always true actually */
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while (n && len) {
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*(out++) = *(in++) ^ ecount_buf[n];
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--len;
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n = (n+1) % 16;
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}
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#ifdef __STRICT_ALIGNMENT
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if (((size_t)in|(size_t)out|(size_t)ivec)%sizeof(size_t) != 0)
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break;
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#endif
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while (len>=16) {
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(*block)(ivec, ecount_buf, key);
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ctr128_inc_aligned(ivec);
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for (; n<16; n+=sizeof(size_t))
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*(size_t *)(out+n) =
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*(size_t *)(in+n) ^ *(size_t *)(ecount_buf+n);
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len -= 16;
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out += 16;
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in += 16;
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n = 0;
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}
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if (len) {
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(*block)(ivec, ecount_buf, key);
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ctr128_inc_aligned(ivec);
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while (len--) {
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out[n] = in[n] ^ ecount_buf[n];
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++n;
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}
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}
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*num = n;
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return;
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} while(0);
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/* the rest would be commonly eliminated by x86* compiler */
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#endif
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while (l<len) {
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if (n==0) {
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(*block)(ivec, ecount_buf, key);
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ctr128_inc(ivec);
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}
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out[l] = in[l] ^ ecount_buf[n];
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++l;
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n = (n+1) % 16;
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}
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*num=n;
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}
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/* increment upper 96 bits of 128-bit counter by 1 */
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static void ctr96_inc(unsigned char *counter) {
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u32 n=12;
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u8 c;
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do {
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--n;
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c = counter[n];
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++c;
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counter[n] = c;
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if (c) return;
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} while (n);
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}
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void CRYPTO_ctr128_encrypt_ctr32(const unsigned char *in, unsigned char *out,
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size_t len, const void *key,
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unsigned char ivec[16], unsigned char ecount_buf[16],
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unsigned int *num, ctr128_f func)
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{
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unsigned int n,ctr32;
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assert(*num < 16);
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n = *num;
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while (n && len) {
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*(out++) = *(in++) ^ ecount_buf[n];
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--len;
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n = (n+1) % 16;
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}
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ctr32 = GETU32(ivec+12);
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while (len>=16) {
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size_t blocks = len/16;
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/*
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* 1<<28 is just a not-so-small yet not-so-large number...
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* Below condition is practically never met, but it has to
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* be checked for code correctness.
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*/
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if (sizeof(size_t)>sizeof(unsigned int) && blocks>(1U<<28))
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blocks = (1U<<28);
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/*
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* As (*func) operates on 32-bit counter, caller
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* has to handle overflow. 'if' below detects the
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* overflow, which is then handled by limiting the
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* amount of blocks to the exact overflow point...
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*/
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ctr32 += (u32)blocks;
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if (ctr32 < blocks) {
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blocks -= ctr32;
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ctr32 = 0;
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}
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(*func)(in,out,blocks,key,ivec);
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/* (*ctr) does not update ivec, caller does: */
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PUTU32(ivec+12,ctr32);
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/* ... overflow was detected, propogate carry. */
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if (ctr32 == 0) ctr96_inc(ivec);
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blocks *= 16;
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len -= blocks;
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out += blocks;
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in += blocks;
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}
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if (len) {
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memset(ecount_buf,0,16);
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(*func)(ecount_buf,ecount_buf,1,key,ivec);
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++ctr32;
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PUTU32(ivec+12,ctr32);
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if (ctr32 == 0) ctr96_inc(ivec);
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while (len--) {
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out[n] = in[n] ^ ecount_buf[n];
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++n;
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}
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}
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*num=n;
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}
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