crypto/modes/ofb128.c

/* ====================================================================
 * 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. 
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 * 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
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 * 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
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 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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 * ====================================================================
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 */

#include <openssl/crypto.h>
#include "modes_lcl.h"
#include <string.h>

#ifndef MODES_DEBUG
# ifndef NDEBUG
#  define NDEBUG
# endif
#endif
#include <assert.h>

/* The input and output encrypted as though 128bit ofb 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_ofb128_encrypt(const unsigned char *in, unsigned char *out,
			size_t len, const void *key,
			unsigned char ivec[16], int *num,
			block128_f block)
{
	unsigned int n;
	size_t l=0;

	assert(in && out && key && ivec && num);

	n = *num;

#if !defined(OPENSSL_SMALL_FOOTPRINT)
	if (16%sizeof(size_t) == 0) do { /* always true actually */
		while (n && len) {
			*(out++) = *(in++) ^ ivec[n];
			--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*)(out+n) =
				*(size_t*)(in+n) ^ *(size_t*)(ivec+n);
			len -= 16;
			out += 16;
			in  += 16;
			n = 0;
		}
		if (len) {
			(*block)(ivec, ivec, key);
			while (len--) {
				out[n] = in[n] ^ ivec[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] = in[l] ^ ivec[n];
		++l;
		n = (n+1) % 16;
	}

	*num=n;
}