openssl/crypto/aes/aes_ctr.c
Richard Levitte dbcc560717 The AES CTR API was buggy, we need to save the encrypted counter as well
between calls, or that will be lost if it returned with *num non-zero.
2002-10-11 22:37:44 +00:00

118 lines
3.8 KiB
C

/* crypto/aes/aes_ctr.c -*- mode:C; c-file-style: "eay" -*- */
/* ====================================================================
* Copyright (c) 1998-2002 The OpenSSL Project. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
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*
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*
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*
* 3. All advertising materials mentioning features or use of this
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* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
*
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*
* 5. Products derived from this software may not be called "OpenSSL"
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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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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
* ====================================================================
*
*/
#include <assert.h>
#include <openssl/aes.h>
#include "aes_locl.h"
/* NOTE: CTR mode is big-endian. The rest of the AES code
* is endian-neutral. */
/* increment counter (128-bit int) by 2^64 */
static void AES_ctr128_inc(unsigned char *counter) {
unsigned long c;
/* Grab 3rd dword of counter and increment */
#ifdef L_ENDIAN
c = GETU32(counter + 8);
c++;
PUTU32(counter + 8, c);
#else
c = GETU32(counter + 4);
c++;
PUTU32(counter + 4, c);
#endif
/* if no overflow, we're done */
if (c)
return;
/* Grab top dword of counter and increment */
#ifdef L_ENDIAN
c = GETU32(counter + 12);
c++;
PUTU32(counter + 12, c);
#else
c = GETU32(counter + 0);
c++;
PUTU32(counter + 0, c);
#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;
*/
void AES_ctr128_encrypt(const unsigned char *in, unsigned char *out,
const unsigned long length, const AES_KEY *key,
unsigned char counter[AES_BLOCK_SIZE],
unsigned char ecount_buf[AES_BLOCK_SIZE],
unsigned int *num) {
unsigned int n;
unsigned long l=length;
assert(in && out && key && counter && num);
n = *num;
while (l--) {
if (n == 0) {
AES_encrypt(counter, ecount_buf, key);
AES_ctr128_inc(counter);
}
*(out++) = *(in++) ^ ecount_buf[n];
n = (n+1) % AES_BLOCK_SIZE;
}
*num=n;
}