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(*num < 16); 125 126 n = *num; 127 128 #if !defined(OPENSSL_SMALL_FOOTPRINT) 129 if (16%sizeof(size_t) == 0) do { /* always true actually */ 130 while (n && len) { 131 *(out++) = *(in++) ^ ecount_buf[n]; 132 --len; 133 n = (n+1) % 16; 134 } 135 136 #ifdef __STRICT_ALIGNMENT 137 if (((size_t)in|(size_t)out|(size_t)ivec)%sizeof(size_t) != 0) 138 break; 139 #endif 140 while (len>=16) { 141 (*block)(ivec, ecount_buf, key); 142 ctr128_inc_aligned(ivec); 143 for (; n<16; n+=sizeof(size_t)) 144 *(size_t *)(out+n) = 145 *(size_t *)(in+n) ^ *(size_t *)(ecount_buf+n); 146 len -= 16; 147 out += 16; 148 in += 16; 149 n = 0; 150 } 151 if (len) { 152 (*block)(ivec, ecount_buf, key); 153 ctr128_inc_aligned(ivec); 154 while (len--) { 155 out[n] = in[n] ^ ecount_buf[n]; 156 ++n; 157 } 158 } 159 *num = n; 160 return; 161 } while(0); 162 /* the rest would be commonly eliminated by x86* compiler */ 163 #endif 164 while (l<len) { 165 if (n==0) { 166 (*block)(ivec, ecount_buf, key); 167 ctr128_inc(ivec); 168 } 169 out[l] = in[l] ^ ecount_buf[n]; 170 ++l; 171 n = (n+1) % 16; 172 } 173 174 *num=n; 175 } 176 177 /* increment upper 96 bits of 128-bit counter by 1 */ 178 static void ctr96_inc(unsigned char *counter) { 179 u32 n=12; 180 u8 c; 181 182 do { 183 --n; 184 c = counter[n]; 185 ++c; 186 counter[n] = c; 187 if (c) return; 188 } while (n); 189 } 190 191 void CRYPTO_ctr128_encrypt_ctr32(const unsigned char *in, unsigned char *out, 192 size_t len, const void *key, 193 unsigned char ivec[16], unsigned char ecount_buf[16], 194 unsigned int *num, ctr128_f func) 195 { 196 unsigned int n,ctr32; 197 198 assert(*num < 16); 199 200 n = *num; 201 202 while (n && len) { 203 *(out++) = *(in++) ^ ecount_buf[n]; 204 --len; 205 n = (n+1) % 16; 206 } 207 208 ctr32 = GETU32(ivec+12); 209 while (len>=16) { 210 size_t blocks = len/16; 211 /* 212 * 1<<28 is just a not-so-small yet not-so-large number... 213 * Below condition is practically never met, but it has to 214 * be checked for code correctness. 215 */ 216 if (sizeof(size_t)>sizeof(unsigned int) && blocks>(1U<<28)) 217 blocks = (1U<<28); 218 /* 219 * As (*func) operates on 32-bit counter, caller 220 * has to handle overflow. 'if' below detects the 221 * overflow, which is then handled by limiting the 222 * amount of blocks to the exact overflow point... 223 */ 224 ctr32 += (u32)blocks; 225 if (ctr32 < blocks) { 226 blocks -= ctr32; 227 ctr32 = 0; 228 } 229 (*func)(in,out,blocks,key,ivec); 230 /* (*ctr) does not update ivec, caller does: */ 231 PUTU32(ivec+12,ctr32); 232 /* ... overflow was detected, propogate carry. */ 233 if (ctr32 == 0) ctr96_inc(ivec); 234 blocks *= 16; 235 len -= blocks; 236 out += blocks; 237 in += blocks; 238 } 239 if (len) { 240 memset(ecount_buf,0,16); 241 (*func)(ecount_buf,ecount_buf,1,key,ivec); 242 ++ctr32; 243 PUTU32(ivec+12,ctr32); 244 if (ctr32 == 0) ctr96_inc(ivec); 245 while (len--) { 246 out[n] = in[n] ^ ecount_buf[n]; 247 ++n; 248 } 249 } 250 251 *num=n; 252 } 253