1 /* $NetBSD: cipher-aesctr.c,v 1.2 2018/04/06 18:59:00 christos Exp $ */ 2 /* $OpenBSD: cipher-aesctr.c,v 1.2 2015/01/14 10:24:42 markus Exp $ */ 3 /* 4 * Copyright (c) 2003 Markus Friedl. All rights reserved. 5 * 6 * Permission to use, copy, modify, and distribute this software for any 7 * purpose with or without fee is hereby granted, provided that the above 8 * copyright notice and this permission notice appear in all copies. 9 * 10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 17 */ 18 #include "includes.h" 19 __RCSID("$NetBSD: cipher-aesctr.c,v 1.2 2018/04/06 18:59:00 christos Exp $"); 20 21 #include <sys/types.h> 22 #include <string.h> 23 24 #include "cipher-aesctr.h" 25 26 /* 27 * increment counter 'ctr', 28 * the counter is of size 'len' bytes and stored in network-byte-order. 29 * (LSB at ctr[len-1], MSB at ctr[0]) 30 */ 31 static __inline__ void 32 aesctr_inc(u8 *ctr, u32 len) 33 { 34 ssize_t i; 35 36 #ifndef CONSTANT_TIME_INCREMENT 37 for (i = len - 1; i >= 0; i--) 38 if (++ctr[i]) /* continue on overflow */ 39 return; 40 #else 41 u8 x, add = 1; 42 43 for (i = len - 1; i >= 0; i--) { 44 ctr[i] += add; 45 /* constant time for: x = ctr[i] ? 1 : 0 */ 46 x = ctr[i]; 47 x = (x | (x >> 4)) & 0xf; 48 x = (x | (x >> 2)) & 0x3; 49 x = (x | (x >> 1)) & 0x1; 50 add *= (x^1); 51 } 52 #endif 53 } 54 55 void 56 aesctr_keysetup(aesctr_ctx *x,const u8 *k,u32 kbits,u32 ivbits) 57 { 58 x->rounds = rijndaelKeySetupEnc(x->ek, k, kbits); 59 } 60 61 void 62 aesctr_ivsetup(aesctr_ctx *x,const u8 *iv) 63 { 64 memcpy(x->ctr, iv, AES_BLOCK_SIZE); 65 } 66 67 void 68 aesctr_encrypt_bytes(aesctr_ctx *x,const u8 *m,u8 *c,u32 bytes) 69 { 70 u32 n = 0; 71 u8 buf[AES_BLOCK_SIZE]; 72 73 while ((bytes--) > 0) { 74 if (n == 0) { 75 rijndaelEncrypt(x->ek, x->rounds, x->ctr, buf); 76 aesctr_inc(x->ctr, AES_BLOCK_SIZE); 77 } 78 *(c++) = *(m++) ^ buf[n]; 79 n = (n + 1) % AES_BLOCK_SIZE; 80 } 81 } 82