1 /* $OpenBSD: cipher-aesctr.c,v 1.2 2015/01/14 10:24:42 markus Exp $ */ 2 /* 3 * Copyright (c) 2003 Markus Friedl. All rights reserved. 4 * 5 * Permission to use, copy, modify, and distribute this software for any 6 * purpose with or without fee is hereby granted, provided that the above 7 * copyright notice and this permission notice appear in all copies. 8 * 9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16 */ 17 18 #include "includes.h" 19 20 #include <sys/types.h> 21 #include <string.h> 22 23 #ifndef WITH_OPENSSL 24 25 #include "cipher-aesctr.h" 26 27 /* 28 * increment counter 'ctr', 29 * the counter is of size 'len' bytes and stored in network-byte-order. 30 * (LSB at ctr[len-1], MSB at ctr[0]) 31 */ 32 static inline void 33 aesctr_inc(u8 *ctr, u32 len) 34 { 35 ssize_t i; 36 37 #ifndef CONSTANT_TIME_INCREMENT 38 for (i = len - 1; i >= 0; i--) 39 if (++ctr[i]) /* continue on overflow */ 40 return; 41 #else 42 u8 x, add = 1; 43 44 for (i = len - 1; i >= 0; i--) { 45 ctr[i] += add; 46 /* constant time for: x = ctr[i] ? 1 : 0 */ 47 x = ctr[i]; 48 x = (x | (x >> 4)) & 0xf; 49 x = (x | (x >> 2)) & 0x3; 50 x = (x | (x >> 1)) & 0x1; 51 add *= (x^1); 52 } 53 #endif 54 } 55 56 void 57 aesctr_keysetup(aesctr_ctx *x,const u8 *k,u32 kbits,u32 ivbits) 58 { 59 x->rounds = rijndaelKeySetupEnc(x->ek, k, kbits); 60 } 61 62 void 63 aesctr_ivsetup(aesctr_ctx *x,const u8 *iv) 64 { 65 memcpy(x->ctr, iv, AES_BLOCK_SIZE); 66 } 67 68 void 69 aesctr_encrypt_bytes(aesctr_ctx *x,const u8 *m,u8 *c,u32 bytes) 70 { 71 u32 n = 0; 72 u8 buf[AES_BLOCK_SIZE]; 73 74 while ((bytes--) > 0) { 75 if (n == 0) { 76 rijndaelEncrypt(x->ek, x->rounds, x->ctr, buf); 77 aesctr_inc(x->ctr, AES_BLOCK_SIZE); 78 } 79 *(c++) = *(m++) ^ buf[n]; 80 n = (n + 1) % AES_BLOCK_SIZE; 81 } 82 } 83 #endif /* !WITH_OPENSSL */ 84