1 /* ==================================================================== 2 * Copyright (c) 2008 The OpenSSL Project. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in 13 * the documentation and/or other materials provided with the 14 * distribution. 15 * 16 * 3. All advertising materials mentioning features or use of this 17 * software must display the following acknowledgment: 18 * "This product includes software developed by the OpenSSL Project 19 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 20 * 21 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 22 * endorse or promote products derived from this software without 23 * prior written permission. For written permission, please contact 24 * openssl-core (at) openssl.org. 25 * 26 * 5. Products derived from this software may not be called "OpenSSL" 27 * nor may "OpenSSL" appear in their names without prior written 28 * permission of the OpenSSL Project. 29 * 30 * 6. Redistributions of any form whatsoever must retain the following 31 * acknowledgment: 32 * "This product includes software developed by the OpenSSL Project 33 * for use in the OpenSSL Toolkit (http://www.openssl.org/)" 34 * 35 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 36 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 37 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 38 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 39 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 40 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 41 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 42 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 43 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 44 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 45 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 46 * OF THE POSSIBILITY OF SUCH DAMAGE. 47 * ==================================================================== */ 48 49 #include <openssl/type_check.h> 50 51 #include <assert.h> 52 #include <string.h> 53 54 #include "internal.h" 55 56 57 // NOTE: the IV/counter CTR mode is big-endian. The code itself 58 // is endian-neutral. 59 60 // increment counter (128-bit int) by 1 61 static void ctr128_inc(uint8_t *counter) { 62 uint32_t n = 16, c = 1; 63 64 do { 65 --n; 66 c += counter[n]; 67 counter[n] = (uint8_t) c; 68 c >>= 8; 69 } while (n); 70 } 71 72 OPENSSL_COMPILE_ASSERT((16 % sizeof(size_t)) == 0, bad_size_t_size_ctr); 73 74 // The input encrypted as though 128bit counter mode is being used. The extra 75 // state information to record how much of the 128bit block we have used is 76 // contained in *num, and the encrypted counter is kept in ecount_buf. Both 77 // *num and ecount_buf must be initialised with zeros before the first call to 78 // CRYPTO_ctr128_encrypt(). 79 // 80 // This algorithm assumes that the counter is in the x lower bits of the IV 81 // (ivec), and that the application has full control over overflow and the rest 82 // of the IV. This implementation takes NO responsibility for checking that 83 // the counter doesn't overflow into the rest of the IV when incremented. 84 void CRYPTO_ctr128_encrypt(const uint8_t *in, uint8_t *out, size_t len, 85 const void *key, uint8_t ivec[16], 86 uint8_t ecount_buf[16], unsigned int *num, 87 block128_f block) { 88 unsigned int n; 89 90 assert(key && ecount_buf && num); 91 assert(len == 0 || (in && out)); 92 assert(*num < 16); 93 94 n = *num; 95 96 while (n && len) { 97 *(out++) = *(in++) ^ ecount_buf[n]; 98 --len; 99 n = (n + 1) % 16; 100 } 101 102 #if STRICT_ALIGNMENT 103 if (((uintptr_t)in | (uintptr_t)out | 104 (uintptr_t)ecount_buf) % sizeof(size_t) != 0) { 105 size_t l = 0; 106 while (l < len) { 107 if (n == 0) { 108 (*block)(ivec, ecount_buf, key); 109 ctr128_inc(ivec); 110 } 111 out[l] = in[l] ^ ecount_buf[n]; 112 ++l; 113 n = (n + 1) % 16; 114 } 115 116 *num = n; 117 return; 118 } 119 #endif 120 121 while (len >= 16) { 122 (*block)(ivec, ecount_buf, key); 123 ctr128_inc(ivec); 124 for (n = 0; n < 16; n += sizeof(size_t)) { 125 store_word_le(out + n, 126 load_word_le(in + n) ^ load_word_le(ecount_buf + n)); 127 } 128 len -= 16; 129 out += 16; 130 in += 16; 131 n = 0; 132 } 133 if (len) { 134 (*block)(ivec, ecount_buf, key); 135 ctr128_inc(ivec); 136 while (len--) { 137 out[n] = in[n] ^ ecount_buf[n]; 138 ++n; 139 } 140 } 141 *num = n; 142 } 143 144 // increment upper 96 bits of 128-bit counter by 1 145 static void ctr96_inc(uint8_t *counter) { 146 uint32_t n = 12, c = 1; 147 148 do { 149 --n; 150 c += counter[n]; 151 counter[n] = (uint8_t) c; 152 c >>= 8; 153 } while (n); 154 } 155 156 void CRYPTO_ctr128_encrypt_ctr32(const uint8_t *in, uint8_t *out, 157 size_t len, const void *key, 158 uint8_t ivec[16], 159 uint8_t ecount_buf[16], 160 unsigned int *num, ctr128_f func) { 161 unsigned int n, ctr32; 162 163 assert(key && ecount_buf && num); 164 assert(len == 0 || (in && out)); 165 assert(*num < 16); 166 167 n = *num; 168 169 while (n && len) { 170 *(out++) = *(in++) ^ ecount_buf[n]; 171 --len; 172 n = (n + 1) % 16; 173 } 174 175 ctr32 = GETU32(ivec + 12); 176 while (len >= 16) { 177 size_t blocks = len / 16; 178 // 1<<28 is just a not-so-small yet not-so-large number... 179 // Below condition is practically never met, but it has to 180 // be checked for code correctness. 181 if (sizeof(size_t) > sizeof(unsigned int) && blocks > (1U << 28)) { 182 blocks = (1U << 28); 183 } 184 // As (*func) operates on 32-bit counter, caller 185 // has to handle overflow. 'if' below detects the 186 // overflow, which is then handled by limiting the 187 // amount of blocks to the exact overflow point... 188 ctr32 += (uint32_t)blocks; 189 if (ctr32 < blocks) { 190 blocks -= ctr32; 191 ctr32 = 0; 192 } 193 (*func)(in, out, blocks, key, ivec); 194 // (*func) does not update ivec, caller does: 195 PUTU32(ivec + 12, ctr32); 196 // ... overflow was detected, propogate carry. 197 if (ctr32 == 0) { 198 ctr96_inc(ivec); 199 } 200 blocks *= 16; 201 len -= blocks; 202 out += blocks; 203 in += blocks; 204 } 205 if (len) { 206 OPENSSL_memset(ecount_buf, 0, 16); 207 (*func)(ecount_buf, ecount_buf, 1, key, ivec); 208 ++ctr32; 209 PUTU32(ivec + 12, ctr32); 210 if (ctr32 == 0) { 211 ctr96_inc(ivec); 212 } 213 while (len--) { 214 out[n] = in[n] ^ ecount_buf[n]; 215 ++n; 216 } 217 } 218 219 *num = n; 220 } 221
