openssh/cipher-aesctr.c
Damien Miller 72ef7c148c support --without-openssl at configure time
Disables and removes dependency on OpenSSL. Many features don't
work and the set of crypto options is greatly restricted. This
will only work on system with native arc4random or /dev/urandom.

Considered highly experimental for now.
2015-01-15 02:28:36 +11:00

82 lines
2.0 KiB
C

/* $OpenBSD: cipher-aesctr.c,v 1.2 2015/01/14 10:24:42 markus Exp $ */
/*
* Copyright (c) 2003 Markus Friedl. All rights reserved.
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/types.h>
#include <string.h>
#ifndef WITH_OPENSSL
#include "cipher-aesctr.h"
/*
* increment counter 'ctr',
* the counter is of size 'len' bytes and stored in network-byte-order.
* (LSB at ctr[len-1], MSB at ctr[0])
*/
static __inline__ void
aesctr_inc(u8 *ctr, u32 len)
{
ssize_t i;
#ifndef CONSTANT_TIME_INCREMENT
for (i = len - 1; i >= 0; i--)
if (++ctr[i]) /* continue on overflow */
return;
#else
u8 x, add = 1;
for (i = len - 1; i >= 0; i--) {
ctr[i] += add;
/* constant time for: x = ctr[i] ? 1 : 0 */
x = ctr[i];
x = (x | (x >> 4)) & 0xf;
x = (x | (x >> 2)) & 0x3;
x = (x | (x >> 1)) & 0x1;
add *= (x^1);
}
#endif
}
void
aesctr_keysetup(aesctr_ctx *x,const u8 *k,u32 kbits,u32 ivbits)
{
x->rounds = rijndaelKeySetupEnc(x->ek, k, kbits);
}
void
aesctr_ivsetup(aesctr_ctx *x,const u8 *iv)
{
memcpy(x->ctr, iv, AES_BLOCK_SIZE);
}
void
aesctr_encrypt_bytes(aesctr_ctx *x,const u8 *m,u8 *c,u32 bytes)
{
u32 n = 0;
u8 buf[AES_BLOCK_SIZE];
while ((bytes--) > 0) {
if (n == 0) {
rijndaelEncrypt(x->ek, x->rounds, x->ctr, buf);
aesctr_inc(x->ctr, AES_BLOCK_SIZE);
}
*(c++) = *(m++) ^ buf[n];
n = (n + 1) % AES_BLOCK_SIZE;
}
}
#endif /* !WITH_OPENSSL */