145 lines
4.9 KiB
C
145 lines
4.9 KiB
C
/* crypto/aes/aes_ctr.c -*- mode:C; c-file-style: "eay" -*- */
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/* ====================================================================
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* Copyright (c) 1998-2002 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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#ifndef AES_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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#include <openssl/aes.h>
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#include "aes_locl.h"
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/*
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* NOTE: the IV/counter CTR mode is big-endian. The rest of the AES code is
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* endian-neutral.
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*/
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/* increment counter (128-bit int) by 1 */
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static void AES_ctr128_inc(unsigned char *counter)
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{
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unsigned long c;
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/* Grab bottom dword of counter and increment */
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c = GETU32(counter + 12);
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c++;
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c &= 0xFFFFFFFF;
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PUTU32(counter + 12, c);
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/* if no overflow, we're done */
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if (c)
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return;
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/* Grab 1st dword of counter and increment */
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c = GETU32(counter + 8);
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c++;
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c &= 0xFFFFFFFF;
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PUTU32(counter + 8, c);
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/* if no overflow, we're done */
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if (c)
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return;
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/* Grab 2nd dword of counter and increment */
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c = GETU32(counter + 4);
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c++;
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c &= 0xFFFFFFFF;
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PUTU32(counter + 4, c);
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/* if no overflow, we're done */
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if (c)
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return;
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/* Grab top dword of counter and increment */
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c = GETU32(counter + 0);
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c++;
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c &= 0xFFFFFFFF;
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PUTU32(counter + 0, c);
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}
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/*
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* The input encrypted as though 128bit counter mode is being used. The
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* extra state information to record how much of the 128bit block we have
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* used is contained in *num, and the encrypted counter is kept in
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* ecount_buf. Both *num and ecount_buf must be initialised with zeros
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* before the first call to AES_ctr128_encrypt(). This algorithm assumes
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* that the counter is in the x lower bits of the IV (ivec), and that the
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* application has full control over overflow and the rest of the IV. This
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* implementation takes NO responsability for checking that the counter
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* doesn't overflow into the rest of the IV when incremented.
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*/
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void AES_ctr128_encrypt(const unsigned char *in, unsigned char *out,
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const unsigned long length, const AES_KEY *key,
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unsigned char ivec[AES_BLOCK_SIZE],
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unsigned char ecount_buf[AES_BLOCK_SIZE],
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unsigned int *num)
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{
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unsigned int n;
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unsigned long l = length;
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assert(in && out && key && counter && num);
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assert(*num < AES_BLOCK_SIZE);
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n = *num;
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while (l--) {
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if (n == 0) {
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AES_encrypt(ivec, ecount_buf, key);
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AES_ctr128_inc(ivec);
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}
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*(out++) = *(in++) ^ ecount_buf[n];
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n = (n + 1) % AES_BLOCK_SIZE;
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}
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*num = n;
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}
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