1 /* $OpenBSD: ctr128.c,v 1.5 2014/07/09 16:06:13 miod Exp $ */ 2 /* ==================================================================== 3 * Copyright (c) 2008 The OpenSSL Project. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in 14 * the documentation and/or other materials provided with the 15 * distribution. 16 * 17 * 3. All advertising materials mentioning features or use of this 18 * software must display the following acknowledgment: 19 * "This product includes software developed by the OpenSSL Project 20 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 21 * 22 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 23 * endorse or promote products derived from this software without 24 * prior written permission. For written permission, please contact 25 * openssl-core@openssl.org. 26 * 27 * 5. Products derived from this software may not be called "OpenSSL" 28 * nor may "OpenSSL" appear in their names without prior written 29 * permission of the OpenSSL Project. 30 * 31 * 6. Redistributions of any form whatsoever must retain the following 32 * acknowledgment: 33 * "This product includes software developed by the OpenSSL Project 34 * for use in the OpenSSL Toolkit (http://www.openssl.org/)" 35 * 36 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 37 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 38 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 39 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 40 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 41 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 42 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 43 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 44 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 45 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 46 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 47 * OF THE POSSIBILITY OF SUCH DAMAGE. 48 * ==================================================================== 49 * 50 */ 51 52 #include <openssl/crypto.h> 53 #include "modes_lcl.h" 54 #include <string.h> 55 56 #ifndef MODES_DEBUG 57 # ifndef NDEBUG 58 # define NDEBUG 59 # endif 60 #endif 61 #include <assert.h> 62 63 /* NOTE: the IV/counter CTR mode is big-endian. The code itself 64 * is endian-neutral. */ 65 66 /* increment counter (128-bit int) by 1 */ 67 static void ctr128_inc(unsigned char *counter) { 68 u32 n=16; 69 u8 c; 70 71 do { 72 --n; 73 c = counter[n]; 74 ++c; 75 counter[n] = c; 76 if (c) return; 77 } while (n); 78 } 79 80 #if !defined(OPENSSL_SMALL_FOOTPRINT) 81 static void 82 ctr128_inc_aligned(unsigned char *counter) 83 { 84 size_t *data,c,n; 85 86 if (BYTE_ORDER == LITTLE_ENDIAN) { 87 ctr128_inc(counter); 88 return; 89 } 90 91 data = (size_t *)counter; 92 n = 16/sizeof(size_t); 93 do { 94 --n; 95 c = data[n]; 96 ++c; 97 data[n] = c; 98 if (c) return; 99 } while (n); 100 } 101 #endif 102 103 /* The input encrypted as though 128bit counter mode is being 104 * used. The extra state information to record how much of the 105 * 128bit block we have used is contained in *num, and the 106 * encrypted counter is kept in ecount_buf. Both *num and 107 * ecount_buf must be initialised with zeros before the first 108 * call to CRYPTO_ctr128_encrypt(). 109 * 110 * This algorithm assumes that the counter is in the x lower bits 111 * of the IV (ivec), and that the application has full control over 112 * overflow and the rest of the IV. This implementation takes NO 113 * responsability for checking that the counter doesn't overflow 114 * into the rest of the IV when incremented. 115 */ 116 void CRYPTO_ctr128_encrypt(const unsigned char *in, unsigned char *out, 117 size_t len, const void *key, 118 unsigned char ivec[16], unsigned char ecount_buf[16], 119 unsigned int *num, block128_f block) 120 { 121 unsigned int n; 122 size_t l=0; 123 124 assert(in && out && key && ecount_buf && num); 125 assert(*num < 16); 126 127 n = *num; 128 129 #if !defined(OPENSSL_SMALL_FOOTPRINT) 130 if (16%sizeof(size_t) == 0) do { /* always true actually */ 131 while (n && len) { 132 *(out++) = *(in++) ^ ecount_buf[n]; 133 --len; 134 n = (n+1) % 16; 135 } 136 137 #ifdef __STRICT_ALIGNMENT 138 if (((size_t)in|(size_t)out|(size_t)ivec)%sizeof(size_t) != 0) 139 break; 140 #endif 141 while (len>=16) { 142 (*block)(ivec, ecount_buf, key); 143 ctr128_inc_aligned(ivec); 144 for (; n<16; n+=sizeof(size_t)) 145 *(size_t *)(out+n) = 146 *(size_t *)(in+n) ^ *(size_t *)(ecount_buf+n); 147 len -= 16; 148 out += 16; 149 in += 16; 150 n = 0; 151 } 152 if (len) { 153 (*block)(ivec, ecount_buf, key); 154 ctr128_inc_aligned(ivec); 155 while (len--) { 156 out[n] = in[n] ^ ecount_buf[n]; 157 ++n; 158 } 159 } 160 *num = n; 161 return; 162 } while(0); 163 /* the rest would be commonly eliminated by x86* compiler */ 164 #endif 165 while (l<len) { 166 if (n==0) { 167 (*block)(ivec, ecount_buf, key); 168 ctr128_inc(ivec); 169 } 170 out[l] = in[l] ^ ecount_buf[n]; 171 ++l; 172 n = (n+1) % 16; 173 } 174 175 *num=n; 176 } 177 178 /* increment upper 96 bits of 128-bit counter by 1 */ 179 static void ctr96_inc(unsigned char *counter) { 180 u32 n=12; 181 u8 c; 182 183 do { 184 --n; 185 c = counter[n]; 186 ++c; 187 counter[n] = c; 188 if (c) return; 189 } while (n); 190 } 191 192 void CRYPTO_ctr128_encrypt_ctr32(const unsigned char *in, unsigned char *out, 193 size_t len, const void *key, 194 unsigned char ivec[16], unsigned char ecount_buf[16], 195 unsigned int *num, ctr128_f func) 196 { 197 unsigned int n,ctr32; 198 199 assert(in && out && key && ecount_buf && num); 200 assert(*num < 16); 201 202 n = *num; 203 204 while (n && len) { 205 *(out++) = *(in++) ^ ecount_buf[n]; 206 --len; 207 n = (n+1) % 16; 208 } 209 210 ctr32 = GETU32(ivec+12); 211 while (len>=16) { 212 size_t blocks = len/16; 213 /* 214 * 1<<28 is just a not-so-small yet not-so-large number... 215 * Below condition is practically never met, but it has to 216 * be checked for code correctness. 217 */ 218 if (sizeof(size_t)>sizeof(unsigned int) && blocks>(1U<<28)) 219 blocks = (1U<<28); 220 /* 221 * As (*func) operates on 32-bit counter, caller 222 * has to handle overflow. 'if' below detects the 223 * overflow, which is then handled by limiting the 224 * amount of blocks to the exact overflow point... 225 */ 226 ctr32 += (u32)blocks; 227 if (ctr32 < blocks) { 228 blocks -= ctr32; 229 ctr32 = 0; 230 } 231 (*func)(in,out,blocks,key,ivec); 232 /* (*ctr) does not update ivec, caller does: */ 233 PUTU32(ivec+12,ctr32); 234 /* ... overflow was detected, propogate carry. */ 235 if (ctr32 == 0) ctr96_inc(ivec); 236 blocks *= 16; 237 len -= blocks; 238 out += blocks; 239 in += blocks; 240 } 241 if (len) { 242 memset(ecount_buf,0,16); 243 (*func)(ecount_buf,ecount_buf,1,key,ivec); 244 ++ctr32; 245 PUTU32(ivec+12,ctr32); 246 if (ctr32 == 0) ctr96_inc(ivec); 247 while (len--) { 248 out[n] = in[n] ^ ecount_buf[n]; 249 ++n; 250 } 251 } 252 253 *num=n; 254 } 255