cipher-aesctr.c revision 294332
1193323Sed/* $OpenBSD: cipher-aesctr.c,v 1.2 2015/01/14 10:24:42 markus Exp $ */ 2193323Sed/* 3193323Sed * Copyright (c) 2003 Markus Friedl. All rights reserved. 4193323Sed * 5193323Sed * Permission to use, copy, modify, and distribute this software for any 6193323Sed * purpose with or without fee is hereby granted, provided that the above 7193323Sed * copyright notice and this permission notice appear in all copies. 8193323Sed * 9193323Sed * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 10193323Sed * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11193323Sed * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 12193323Sed * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13193323Sed * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14193323Sed * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 15193323Sed * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16193323Sed */ 17193323Sed 18193323Sed#include "includes.h" 19193323Sed 20199481Srdivacky#include <sys/types.h> 21198090Srdivacky#include <string.h> 22193323Sed 23193323Sed#ifndef WITH_OPENSSL 24198090Srdivacky 25218893Sdim#include "cipher-aesctr.h" 26218893Sdim 27218893Sdim/* 28198090Srdivacky * increment counter 'ctr', 29198090Srdivacky * the counter is of size 'len' bytes and stored in network-byte-order. 30198090Srdivacky * (LSB at ctr[len-1], MSB at ctr[0]) 31198090Srdivacky */ 32198090Srdivackystatic inline void 33198090Srdivackyaesctr_inc(u8 *ctr, u32 len) 34198090Srdivacky{ 35193323Sed ssize_t i; 36193323Sed 37193323Sed#ifndef CONSTANT_TIME_INCREMENT 38193323Sed for (i = len - 1; i >= 0; i--) 39193323Sed if (++ctr[i]) /* continue on overflow */ 40193323Sed return; 41193323Sed#else 42199989Srdivacky u8 x, add = 1; 43193323Sed 44193323Sed for (i = len - 1; i >= 0; i--) { 45193323Sed ctr[i] += add; 46193323Sed /* constant time for: x = ctr[i] ? 1 : 0 */ 47226633Sdim x = ctr[i]; 48193323Sed x = (x | (x >> 4)) & 0xf; 49193323Sed x = (x | (x >> 2)) & 0x3; 50193323Sed x = (x | (x >> 1)) & 0x1; 51193323Sed add *= (x^1); 52193323Sed } 53193323Sed#endif 54193323Sed} 55193323Sed 56193323Sedvoid 57193323Sedaesctr_keysetup(aesctr_ctx *x,const u8 *k,u32 kbits,u32 ivbits) 58199989Srdivacky{ 59193323Sed x->rounds = rijndaelKeySetupEnc(x->ek, k, kbits); 60234353Sdim} 61234353Sdim 62234353Sdimvoid 63193323Sedaesctr_ivsetup(aesctr_ctx *x,const u8 *iv) 64193323Sed{ 65193323Sed memcpy(x->ctr, iv, AES_BLOCK_SIZE); 66193323Sed} 67193323Sed 68193323Sedvoid 69226633Sdimaesctr_encrypt_bytes(aesctr_ctx *x,const u8 *m,u8 *c,u32 bytes) 70193323Sed{ 71193323Sed u32 n = 0; 72193323Sed u8 buf[AES_BLOCK_SIZE]; 73193323Sed 74193323Sed while ((bytes--) > 0) { 75193323Sed if (n == 0) { 76193323Sed rijndaelEncrypt(x->ek, x->rounds, x->ctr, buf); 77193323Sed aesctr_inc(x->ctr, AES_BLOCK_SIZE); 78193323Sed } 79193323Sed *(c++) = *(m++) ^ buf[n]; 80193323Sed n = (n + 1) % AES_BLOCK_SIZE; 81193323Sed } 82193323Sed} 83193323Sed#endif /* !WITH_OPENSSL */ 84193323Sed