1 /* $OpenBSD: cmac.c,v 1.9 2014/07/12 14:58:32 miod Exp $ */ 2 /* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL 3 * project. 4 */ 5 /* ==================================================================== 6 * Copyright (c) 2010 The OpenSSL Project. All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in 17 * the documentation and/or other materials provided with the 18 * distribution. 19 * 20 * 3. All advertising materials mentioning features or use of this 21 * software must display the following acknowledgment: 22 * "This product includes software developed by the OpenSSL Project 23 * for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)" 24 * 25 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 26 * endorse or promote products derived from this software without 27 * prior written permission. For written permission, please contact 28 * licensing@OpenSSL.org. 29 * 30 * 5. Products derived from this software may not be called "OpenSSL" 31 * nor may "OpenSSL" appear in their names without prior written 32 * permission of the OpenSSL Project. 33 * 34 * 6. Redistributions of any form whatsoever must retain the following 35 * acknowledgment: 36 * "This product includes software developed by the OpenSSL Project 37 * for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)" 38 * 39 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 40 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 41 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 42 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 43 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 44 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 45 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 46 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 47 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 48 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 49 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 50 * OF THE POSSIBILITY OF SUCH DAMAGE. 51 * ==================================================================== 52 */ 53 54 #include <stdio.h> 55 #include <stdlib.h> 56 #include <string.h> 57 58 #include <openssl/cmac.h> 59 60 struct CMAC_CTX_st { 61 /* Cipher context to use */ 62 EVP_CIPHER_CTX cctx; 63 /* Keys k1 and k2 */ 64 unsigned char k1[EVP_MAX_BLOCK_LENGTH]; 65 unsigned char k2[EVP_MAX_BLOCK_LENGTH]; 66 /* Temporary block */ 67 unsigned char tbl[EVP_MAX_BLOCK_LENGTH]; 68 /* Last (possibly partial) block */ 69 unsigned char last_block[EVP_MAX_BLOCK_LENGTH]; 70 /* Number of bytes in last block: -1 means context not initialised */ 71 int nlast_block; 72 }; 73 74 75 /* Make temporary keys K1 and K2 */ 76 77 static void 78 make_kn(unsigned char *k1, unsigned char *l, int bl) 79 { 80 int i; 81 82 /* Shift block to left, including carry */ 83 for (i = 0; i < bl; i++) { 84 k1[i] = l[i] << 1; 85 if (i < bl - 1 && l[i + 1] & 0x80) 86 k1[i] |= 1; 87 } 88 /* If MSB set fixup with R */ 89 if (l[0] & 0x80) 90 k1[bl - 1] ^= bl == 16 ? 0x87 : 0x1b; 91 } 92 93 CMAC_CTX * 94 CMAC_CTX_new(void) 95 { 96 CMAC_CTX *ctx; 97 98 ctx = malloc(sizeof(CMAC_CTX)); 99 if (!ctx) 100 return NULL; 101 EVP_CIPHER_CTX_init(&ctx->cctx); 102 ctx->nlast_block = -1; 103 return ctx; 104 } 105 106 void 107 CMAC_CTX_cleanup(CMAC_CTX *ctx) 108 { 109 EVP_CIPHER_CTX_cleanup(&ctx->cctx); 110 explicit_bzero(ctx->tbl, EVP_MAX_BLOCK_LENGTH); 111 explicit_bzero(ctx->k1, EVP_MAX_BLOCK_LENGTH); 112 explicit_bzero(ctx->k2, EVP_MAX_BLOCK_LENGTH); 113 explicit_bzero(ctx->last_block, EVP_MAX_BLOCK_LENGTH); 114 ctx->nlast_block = -1; 115 } 116 117 EVP_CIPHER_CTX * 118 CMAC_CTX_get0_cipher_ctx(CMAC_CTX *ctx) 119 { 120 return &ctx->cctx; 121 } 122 123 void 124 CMAC_CTX_free(CMAC_CTX *ctx) 125 { 126 if (ctx == NULL) 127 return; 128 129 CMAC_CTX_cleanup(ctx); 130 free(ctx); 131 } 132 133 int 134 CMAC_CTX_copy(CMAC_CTX *out, const CMAC_CTX *in) 135 { 136 int bl; 137 138 if (in->nlast_block == -1) 139 return 0; 140 if (!EVP_CIPHER_CTX_copy(&out->cctx, &in->cctx)) 141 return 0; 142 bl = EVP_CIPHER_CTX_block_size(&in->cctx); 143 memcpy(out->k1, in->k1, bl); 144 memcpy(out->k2, in->k2, bl); 145 memcpy(out->tbl, in->tbl, bl); 146 memcpy(out->last_block, in->last_block, bl); 147 out->nlast_block = in->nlast_block; 148 return 1; 149 } 150 151 int 152 CMAC_Init(CMAC_CTX *ctx, const void *key, size_t keylen, 153 const EVP_CIPHER *cipher, ENGINE *impl) 154 { 155 static unsigned char zero_iv[EVP_MAX_BLOCK_LENGTH]; 156 157 /* All zeros means restart */ 158 if (!key && !cipher && !impl && keylen == 0) { 159 /* Not initialised */ 160 if (ctx->nlast_block == -1) 161 return 0; 162 if (!EVP_EncryptInit_ex(&ctx->cctx, NULL, NULL, NULL, zero_iv)) 163 return 0; 164 memset(ctx->tbl, 0, EVP_CIPHER_CTX_block_size(&ctx->cctx)); 165 ctx->nlast_block = 0; 166 return 1; 167 } 168 /* Initialiase context */ 169 if (cipher && !EVP_EncryptInit_ex(&ctx->cctx, cipher, impl, NULL, NULL)) 170 return 0; 171 /* Non-NULL key means initialisation complete */ 172 if (key) { 173 int bl; 174 175 if (!EVP_CIPHER_CTX_cipher(&ctx->cctx)) 176 return 0; 177 if (!EVP_CIPHER_CTX_set_key_length(&ctx->cctx, keylen)) 178 return 0; 179 if (!EVP_EncryptInit_ex(&ctx->cctx, NULL, NULL, key, zero_iv)) 180 return 0; 181 bl = EVP_CIPHER_CTX_block_size(&ctx->cctx); 182 if (!EVP_Cipher(&ctx->cctx, ctx->tbl, zero_iv, bl)) 183 return 0; 184 make_kn(ctx->k1, ctx->tbl, bl); 185 make_kn(ctx->k2, ctx->k1, bl); 186 explicit_bzero(ctx->tbl, bl); 187 /* Reset context again ready for first data block */ 188 if (!EVP_EncryptInit_ex(&ctx->cctx, NULL, NULL, NULL, zero_iv)) 189 return 0; 190 /* Zero tbl so resume works */ 191 memset(ctx->tbl, 0, bl); 192 ctx->nlast_block = 0; 193 } 194 return 1; 195 } 196 197 int 198 CMAC_Update(CMAC_CTX *ctx, const void *in, size_t dlen) 199 { 200 const unsigned char *data = in; 201 size_t bl; 202 203 if (ctx->nlast_block == -1) 204 return 0; 205 if (dlen == 0) 206 return 1; 207 bl = EVP_CIPHER_CTX_block_size(&ctx->cctx); 208 /* Copy into partial block if we need to */ 209 if (ctx->nlast_block > 0) { 210 size_t nleft; 211 212 nleft = bl - ctx->nlast_block; 213 if (dlen < nleft) 214 nleft = dlen; 215 memcpy(ctx->last_block + ctx->nlast_block, data, nleft); 216 dlen -= nleft; 217 ctx->nlast_block += nleft; 218 /* If no more to process return */ 219 if (dlen == 0) 220 return 1; 221 data += nleft; 222 /* Else not final block so encrypt it */ 223 if (!EVP_Cipher(&ctx->cctx, ctx->tbl, ctx->last_block, bl)) 224 return 0; 225 } 226 /* Encrypt all but one of the complete blocks left */ 227 while (dlen > bl) { 228 if (!EVP_Cipher(&ctx->cctx, ctx->tbl, data, bl)) 229 return 0; 230 dlen -= bl; 231 data += bl; 232 } 233 /* Copy any data left to last block buffer */ 234 memcpy(ctx->last_block, data, dlen); 235 ctx->nlast_block = dlen; 236 return 1; 237 } 238 239 int 240 CMAC_Final(CMAC_CTX *ctx, unsigned char *out, size_t *poutlen) 241 { 242 int i, bl, lb; 243 244 if (ctx->nlast_block == -1) 245 return 0; 246 bl = EVP_CIPHER_CTX_block_size(&ctx->cctx); 247 *poutlen = (size_t)bl; 248 if (!out) 249 return 1; 250 lb = ctx->nlast_block; 251 /* Is last block complete? */ 252 if (lb == bl) { 253 for (i = 0; i < bl; i++) 254 out[i] = ctx->last_block[i] ^ ctx->k1[i]; 255 } else { 256 ctx->last_block[lb] = 0x80; 257 if (bl - lb > 1) 258 memset(ctx->last_block + lb + 1, 0, bl - lb - 1); 259 for (i = 0; i < bl; i++) 260 out[i] = ctx->last_block[i] ^ ctx->k2[i]; 261 } 262 if (!EVP_Cipher(&ctx->cctx, out, out, bl)) { 263 explicit_bzero(out, bl); 264 return 0; 265 } 266 return 1; 267 } 268 269 int 270 CMAC_resume(CMAC_CTX *ctx) 271 { 272 if (ctx->nlast_block == -1) 273 return 0; 274 /* The buffer "tbl" containes the last fully encrypted block 275 * which is the last IV (or all zeroes if no last encrypted block). 276 * The last block has not been modified since CMAC_final(). 277 * So reinitialising using the last decrypted block will allow 278 * CMAC to continue after calling CMAC_Final(). 279 */ 280 return EVP_EncryptInit_ex(&ctx->cctx, NULL, NULL, NULL, ctx->tbl); 281 } 282