1 /* $OpenBSD: ctr128.c,v 1.7 2017/08/13 17:46:24 bcook 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 #if BYTE_ORDER == LITTLE_ENDIAN 85 ctr128_inc(counter); 86 #else 87 size_t *data, c, n; 88 data = (size_t *)counter; 89 n = 16 / sizeof(size_t); 90 do { 91 --n; 92 c = data[n]; 93 ++c; 94 data[n] = c; 95 if (c) 96 return; 97 } while (n); 98 #endif 99 } 100 #endif 101 102 /* The input encrypted as though 128bit counter mode is being 103 * used. The extra state information to record how much of the 104 * 128bit block we have used is contained in *num, and the 105 * encrypted counter is kept in ecount_buf. Both *num and 106 * ecount_buf must be initialised with zeros before the first 107 * call to CRYPTO_ctr128_encrypt(). 108 * 109 * This algorithm assumes that the counter is in the x lower bits 110 * of the IV (ivec), and that the application has full control over 111 * overflow and the rest of the IV. This implementation takes NO 112 * responsability for checking that the counter doesn't overflow 113 * into the rest of the IV when incremented. 114 */ 115 void CRYPTO_ctr128_encrypt(const unsigned char *in, unsigned char *out, 116 size_t len, const void *key, 117 unsigned char ivec[16], unsigned char ecount_buf[16], 118 unsigned int *num, block128_f block) 119 { 120 unsigned int n; 121 size_t l=0; 122 123 assert(*num < 16); 124 125 n = *num; 126 127 #if !defined(OPENSSL_SMALL_FOOTPRINT) 128 if (16%sizeof(size_t) == 0) do { /* always true actually */ 129 while (n && len) { 130 *(out++) = *(in++) ^ ecount_buf[n]; 131 --len; 132 n = (n+1) % 16; 133 } 134 135 #ifdef __STRICT_ALIGNMENT 136 if (((size_t)in|(size_t)out|(size_t)ivec)%sizeof(size_t) != 0) 137 break; 138 #endif 139 while (len>=16) { 140 (*block)(ivec, ecount_buf, key); 141 ctr128_inc_aligned(ivec); 142 for (; n<16; n+=sizeof(size_t)) 143 *(size_t *)(out+n) = 144 *(size_t *)(in+n) ^ *(size_t *)(ecount_buf+n); 145 len -= 16; 146 out += 16; 147 in += 16; 148 n = 0; 149 } 150 if (len) { 151 (*block)(ivec, ecount_buf, key); 152 ctr128_inc_aligned(ivec); 153 while (len--) { 154 out[n] = in[n] ^ ecount_buf[n]; 155 ++n; 156 } 157 } 158 *num = n; 159 return; 160 } while(0); 161 /* the rest would be commonly eliminated by x86* compiler */ 162 #endif 163 while (l<len) { 164 if (n==0) { 165 (*block)(ivec, ecount_buf, key); 166 ctr128_inc(ivec); 167 } 168 out[l] = in[l] ^ ecount_buf[n]; 169 ++l; 170 n = (n+1) % 16; 171 } 172 173 *num=n; 174 } 175 176 /* increment upper 96 bits of 128-bit counter by 1 */ 177 static void ctr96_inc(unsigned char *counter) { 178 u32 n=12; 179 u8 c; 180 181 do { 182 --n; 183 c = counter[n]; 184 ++c; 185 counter[n] = c; 186 if (c) return; 187 } while (n); 188 } 189 190 void CRYPTO_ctr128_encrypt_ctr32(const unsigned char *in, unsigned char *out, 191 size_t len, const void *key, 192 unsigned char ivec[16], unsigned char ecount_buf[16], 193 unsigned int *num, ctr128_f func) 194 { 195 unsigned int n,ctr32; 196 197 assert(*num < 16); 198 199 n = *num; 200 201 while (n && len) { 202 *(out++) = *(in++) ^ ecount_buf[n]; 203 --len; 204 n = (n+1) % 16; 205 } 206 207 ctr32 = GETU32(ivec+12); 208 while (len>=16) { 209 size_t blocks = len/16; 210 /* 211 * 1<<28 is just a not-so-small yet not-so-large number... 212 * Below condition is practically never met, but it has to 213 * be checked for code correctness. 214 */ 215 if (sizeof(size_t)>sizeof(unsigned int) && blocks>(1U<<28)) 216 blocks = (1U<<28); 217 /* 218 * As (*func) operates on 32-bit counter, caller 219 * has to handle overflow. 'if' below detects the 220 * overflow, which is then handled by limiting the 221 * amount of blocks to the exact overflow point... 222 */ 223 ctr32 += (u32)blocks; 224 if (ctr32 < blocks) { 225 blocks -= ctr32; 226 ctr32 = 0; 227 } 228 (*func)(in,out,blocks,key,ivec); 229 /* (*ctr) does not update ivec, caller does: */ 230 PUTU32(ivec+12,ctr32); 231 /* ... overflow was detected, propogate carry. */ 232 if (ctr32 == 0) ctr96_inc(ivec); 233 blocks *= 16; 234 len -= blocks; 235 out += blocks; 236 in += blocks; 237 } 238 if (len) { 239 memset(ecount_buf,0,16); 240 (*func)(ecount_buf,ecount_buf,1,key,ivec); 241 ++ctr32; 242 PUTU32(ivec+12,ctr32); 243 if (ctr32 == 0) ctr96_inc(ivec); 244 while (len--) { 245 out[n] = in[n] ^ ecount_buf[n]; 246 ++n; 247 } 248 } 249 250 *num=n; 251 } 252