1 /* 2 * NIST SP800-38C compliant CCM implementation 3 * 4 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved 5 * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later 6 * 7 * This file is provided under the Apache License 2.0, or the 8 * GNU General Public License v2.0 or later. 9 * 10 * ********** 11 * Apache License 2.0: 12 * 13 * Licensed under the Apache License, Version 2.0 (the "License"); you may 14 * not use this file except in compliance with the License. 15 * You may obtain a copy of the License at 16 * 17 * http://www.apache.org/licenses/LICENSE-2.0 18 * 19 * Unless required by applicable law or agreed to in writing, software 20 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 21 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 22 * See the License for the specific language governing permissions and 23 * limitations under the License. 24 * 25 * ********** 26 * 27 * ********** 28 * GNU General Public License v2.0 or later: 29 * 30 * This program is free software; you can redistribute it and/or modify 31 * it under the terms of the GNU General Public License as published by 32 * the Free Software Foundation; either version 2 of the License, or 33 * (at your option) any later version. 34 * 35 * This program is distributed in the hope that it will be useful, 36 * but WITHOUT ANY WARRANTY; without even the implied warranty of 37 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 38 * GNU General Public License for more details. 39 * 40 * You should have received a copy of the GNU General Public License along 41 * with this program; if not, write to the Free Software Foundation, Inc., 42 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. 43 * 44 * ********** 45 * 46 * This file is part of mbed TLS (https://tls.mbed.org) 47 */ 48 49 /* 50 * Definition of CCM: 51 * http://csrc.nist.gov/publications/nistpubs/800-38C/SP800-38C_updated-July20_2007.pdf 52 * RFC 3610 "Counter with CBC-MAC (CCM)" 53 * 54 * Related: 55 * RFC 5116 "An Interface and Algorithms for Authenticated Encryption" 56 */ 57 58 #if !defined(MBEDTLS_CONFIG_FILE) 59 #include "mbedtls/config.h" 60 #else 61 #include MBEDTLS_CONFIG_FILE 62 #endif 63 64 #if defined(MBEDTLS_CCM_C) 65 66 #include "mbedtls/ccm.h" 67 68 #include <string.h> 69 70 #if defined(MBEDTLS_SELF_TEST) && defined(MBEDTLS_AES_C) 71 #if defined(MBEDTLS_PLATFORM_C) 72 #include "mbedtls/platform.h" 73 #else 74 #include <stdio.h> 75 #define mbedtls_printf printf 76 #endif /* MBEDTLS_PLATFORM_C */ 77 #endif /* MBEDTLS_SELF_TEST && MBEDTLS_AES_C */ 78 79 #if !defined(MBEDTLS_CCM_ALT) 80 81 /* Implementation that should never be optimized out by the compiler */ 82 static void mbedtls_zeroize( void *v, size_t n ) { 83 volatile unsigned char *p = (unsigned char*)v; while( n-- ) *p++ = 0; 84 } 85 86 #define CCM_ENCRYPT 0 87 #define CCM_DECRYPT 1 88 89 /* 90 * Initialize context 91 */ 92 void mbedtls_ccm_init( mbedtls_ccm_context *ctx ) 93 { 94 memset( ctx, 0, sizeof( mbedtls_ccm_context ) ); 95 } 96 97 int mbedtls_ccm_setkey( mbedtls_ccm_context *ctx, 98 mbedtls_cipher_id_t cipher, 99 const unsigned char *key, 100 unsigned int keybits ) 101 { 102 int ret; 103 const mbedtls_cipher_info_t *cipher_info; 104 105 cipher_info = mbedtls_cipher_info_from_values( cipher, keybits, MBEDTLS_MODE_ECB ); 106 if( cipher_info == NULL ) 107 return( MBEDTLS_ERR_CCM_BAD_INPUT ); 108 109 if( cipher_info->block_size != 16 ) 110 return( MBEDTLS_ERR_CCM_BAD_INPUT ); 111 112 mbedtls_cipher_free( &ctx->cipher_ctx ); 113 114 if( ( ret = mbedtls_cipher_setup( &ctx->cipher_ctx, cipher_info ) ) != 0 ) 115 return( ret ); 116 117 if( ( ret = mbedtls_cipher_setkey( &ctx->cipher_ctx, key, keybits, 118 MBEDTLS_ENCRYPT ) ) != 0 ) 119 { 120 return( ret ); 121 } 122 123 return( 0 ); 124 } 125 126 /* 127 * Free context 128 */ 129 void mbedtls_ccm_free( mbedtls_ccm_context *ctx ) 130 { 131 mbedtls_cipher_free( &ctx->cipher_ctx ); 132 mbedtls_zeroize( ctx, sizeof( mbedtls_ccm_context ) ); 133 } 134 135 /* 136 * Macros for common operations. 137 * Results in smaller compiled code than static inline functions. 138 */ 139 140 /* 141 * Update the CBC-MAC state in y using a block in b 142 * (Always using b as the source helps the compiler optimise a bit better.) 143 */ 144 #define UPDATE_CBC_MAC \ 145 for( i = 0; i < 16; i++ ) \ 146 y[i] ^= b[i]; \ 147 \ 148 if( ( ret = mbedtls_cipher_update( &ctx->cipher_ctx, y, 16, y, &olen ) ) != 0 ) \ 149 return( ret ); 150 151 /* 152 * Encrypt or decrypt a partial block with CTR 153 * Warning: using b for temporary storage! src and dst must not be b! 154 * This avoids allocating one more 16 bytes buffer while allowing src == dst. 155 */ 156 #define CTR_CRYPT( dst, src, len ) \ 157 if( ( ret = mbedtls_cipher_update( &ctx->cipher_ctx, ctr, 16, b, &olen ) ) != 0 ) \ 158 return( ret ); \ 159 \ 160 for( i = 0; i < len; i++ ) \ 161 dst[i] = src[i] ^ b[i]; 162 163 /* 164 * Authenticated encryption or decryption 165 */ 166 static int ccm_auth_crypt( mbedtls_ccm_context *ctx, int mode, size_t length, 167 const unsigned char *iv, size_t iv_len, 168 const unsigned char *add, size_t add_len, 169 const unsigned char *input, unsigned char *output, 170 unsigned char *tag, size_t tag_len ) 171 { 172 int ret; 173 unsigned char i; 174 unsigned char q; 175 size_t len_left, olen; 176 unsigned char b[16]; 177 unsigned char y[16]; 178 unsigned char ctr[16]; 179 const unsigned char *src; 180 unsigned char *dst; 181 182 /* 183 * Check length requirements: SP800-38C A.1 184 * Additional requirement: a < 2^16 - 2^8 to simplify the code. 185 * 'length' checked later (when writing it to the first block) 186 */ 187 if( tag_len < 4 || tag_len > 16 || tag_len % 2 != 0 ) 188 return( MBEDTLS_ERR_CCM_BAD_INPUT ); 189 190 /* Also implies q is within bounds */ 191 if( iv_len < 7 || iv_len > 13 ) 192 return( MBEDTLS_ERR_CCM_BAD_INPUT ); 193 194 if( add_len > 0xFF00 ) 195 return( MBEDTLS_ERR_CCM_BAD_INPUT ); 196 197 q = 16 - 1 - (unsigned char) iv_len; 198 199 /* 200 * First block B_0: 201 * 0 .. 0 flags 202 * 1 .. iv_len nonce (aka iv) 203 * iv_len+1 .. 15 length 204 * 205 * With flags as (bits): 206 * 7 0 207 * 6 add present? 208 * 5 .. 3 (t - 2) / 2 209 * 2 .. 0 q - 1 210 */ 211 b[0] = 0; 212 b[0] |= ( add_len > 0 ) << 6; 213 b[0] |= ( ( tag_len - 2 ) / 2 ) << 3; 214 b[0] |= q - 1; 215 216 memcpy( b + 1, iv, iv_len ); 217 218 for( i = 0, len_left = length; i < q; i++, len_left >>= 8 ) 219 b[15-i] = (unsigned char)( len_left & 0xFF ); 220 221 if( len_left > 0 ) 222 return( MBEDTLS_ERR_CCM_BAD_INPUT ); 223 224 225 /* Start CBC-MAC with first block */ 226 memset( y, 0, 16 ); 227 UPDATE_CBC_MAC; 228 229 /* 230 * If there is additional data, update CBC-MAC with 231 * add_len, add, 0 (padding to a block boundary) 232 */ 233 if( add_len > 0 ) 234 { 235 size_t use_len; 236 len_left = add_len; 237 src = add; 238 239 memset( b, 0, 16 ); 240 b[0] = (unsigned char)( ( add_len >> 8 ) & 0xFF ); 241 b[1] = (unsigned char)( ( add_len ) & 0xFF ); 242 243 use_len = len_left < 16 - 2 ? len_left : 16 - 2; 244 memcpy( b + 2, src, use_len ); 245 len_left -= use_len; 246 src += use_len; 247 248 UPDATE_CBC_MAC; 249 250 while( len_left > 0 ) 251 { 252 use_len = len_left > 16 ? 16 : len_left; 253 254 memset( b, 0, 16 ); 255 memcpy( b, src, use_len ); 256 UPDATE_CBC_MAC; 257 258 len_left -= use_len; 259 src += use_len; 260 } 261 } 262 263 /* 264 * Prepare counter block for encryption: 265 * 0 .. 0 flags 266 * 1 .. iv_len nonce (aka iv) 267 * iv_len+1 .. 15 counter (initially 1) 268 * 269 * With flags as (bits): 270 * 7 .. 3 0 271 * 2 .. 0 q - 1 272 */ 273 ctr[0] = q - 1; 274 memcpy( ctr + 1, iv, iv_len ); 275 memset( ctr + 1 + iv_len, 0, q ); 276 ctr[15] = 1; 277 278 /* 279 * Authenticate and {en,de}crypt the message. 280 * 281 * The only difference between encryption and decryption is 282 * the respective order of authentication and {en,de}cryption. 283 */ 284 len_left = length; 285 src = input; 286 dst = output; 287 288 while( len_left > 0 ) 289 { 290 size_t use_len = len_left > 16 ? 16 : len_left; 291 292 if( mode == CCM_ENCRYPT ) 293 { 294 memset( b, 0, 16 ); 295 memcpy( b, src, use_len ); 296 UPDATE_CBC_MAC; 297 } 298 299 CTR_CRYPT( dst, src, use_len ); 300 301 if( mode == CCM_DECRYPT ) 302 { 303 memset( b, 0, 16 ); 304 memcpy( b, dst, use_len ); 305 UPDATE_CBC_MAC; 306 } 307 308 dst += use_len; 309 src += use_len; 310 len_left -= use_len; 311 312 /* 313 * Increment counter. 314 * No need to check for overflow thanks to the length check above. 315 */ 316 for( i = 0; i < q; i++ ) 317 if( ++ctr[15-i] != 0 ) 318 break; 319 } 320 321 /* 322 * Authentication: reset counter and crypt/mask internal tag 323 */ 324 for( i = 0; i < q; i++ ) 325 ctr[15-i] = 0; 326 327 CTR_CRYPT( y, y, 16 ); 328 memcpy( tag, y, tag_len ); 329 330 return( 0 ); 331 } 332 333 /* 334 * Authenticated encryption 335 */ 336 int mbedtls_ccm_encrypt_and_tag( mbedtls_ccm_context *ctx, size_t length, 337 const unsigned char *iv, size_t iv_len, 338 const unsigned char *add, size_t add_len, 339 const unsigned char *input, unsigned char *output, 340 unsigned char *tag, size_t tag_len ) 341 { 342 return( ccm_auth_crypt( ctx, CCM_ENCRYPT, length, iv, iv_len, 343 add, add_len, input, output, tag, tag_len ) ); 344 } 345 346 /* 347 * Authenticated decryption 348 */ 349 int mbedtls_ccm_auth_decrypt( mbedtls_ccm_context *ctx, size_t length, 350 const unsigned char *iv, size_t iv_len, 351 const unsigned char *add, size_t add_len, 352 const unsigned char *input, unsigned char *output, 353 const unsigned char *tag, size_t tag_len ) 354 { 355 int ret; 356 unsigned char check_tag[16]; 357 unsigned char i; 358 int diff; 359 360 if( ( ret = ccm_auth_crypt( ctx, CCM_DECRYPT, length, 361 iv, iv_len, add, add_len, 362 input, output, check_tag, tag_len ) ) != 0 ) 363 { 364 return( ret ); 365 } 366 367 /* Check tag in "constant-time" */ 368 for( diff = 0, i = 0; i < tag_len; i++ ) 369 diff |= tag[i] ^ check_tag[i]; 370 371 if( diff != 0 ) 372 { 373 mbedtls_zeroize( output, length ); 374 return( MBEDTLS_ERR_CCM_AUTH_FAILED ); 375 } 376 377 return( 0 ); 378 } 379 380 #endif /* !MBEDTLS_CCM_ALT */ 381 382 #if defined(MBEDTLS_SELF_TEST) && defined(MBEDTLS_AES_C) 383 /* 384 * Examples 1 to 3 from SP800-38C Appendix C 385 */ 386 387 #define NB_TESTS 3 388 #define CCM_SELFTEST_PT_MAX_LEN 24 389 #define CCM_SELFTEST_CT_MAX_LEN 32 390 /* 391 * The data is the same for all tests, only the used length changes 392 */ 393 static const unsigned char key[] = { 394 0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 395 0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f 396 }; 397 398 static const unsigned char iv[] = { 399 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 400 0x18, 0x19, 0x1a, 0x1b 401 }; 402 403 static const unsigned char ad[] = { 404 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 405 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 406 0x10, 0x11, 0x12, 0x13 407 }; 408 409 static const unsigned char msg[CCM_SELFTEST_PT_MAX_LEN] = { 410 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 411 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 412 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 413 }; 414 415 static const size_t iv_len [NB_TESTS] = { 7, 8, 12 }; 416 static const size_t add_len[NB_TESTS] = { 8, 16, 20 }; 417 static const size_t msg_len[NB_TESTS] = { 4, 16, 24 }; 418 static const size_t tag_len[NB_TESTS] = { 4, 6, 8 }; 419 420 static const unsigned char res[NB_TESTS][CCM_SELFTEST_CT_MAX_LEN] = { 421 { 0x71, 0x62, 0x01, 0x5b, 0x4d, 0xac, 0x25, 0x5d }, 422 { 0xd2, 0xa1, 0xf0, 0xe0, 0x51, 0xea, 0x5f, 0x62, 423 0x08, 0x1a, 0x77, 0x92, 0x07, 0x3d, 0x59, 0x3d, 424 0x1f, 0xc6, 0x4f, 0xbf, 0xac, 0xcd }, 425 { 0xe3, 0xb2, 0x01, 0xa9, 0xf5, 0xb7, 0x1a, 0x7a, 426 0x9b, 0x1c, 0xea, 0xec, 0xcd, 0x97, 0xe7, 0x0b, 427 0x61, 0x76, 0xaa, 0xd9, 0xa4, 0x42, 0x8a, 0xa5, 428 0x48, 0x43, 0x92, 0xfb, 0xc1, 0xb0, 0x99, 0x51 } 429 }; 430 431 int mbedtls_ccm_self_test( int verbose ) 432 { 433 mbedtls_ccm_context ctx; 434 /* 435 * Some hardware accelerators require the input and output buffers 436 * would be in RAM, because the flash is not accessible. 437 * Use buffers on the stack to hold the test vectors data. 438 */ 439 unsigned char plaintext[CCM_SELFTEST_PT_MAX_LEN]; 440 unsigned char ciphertext[CCM_SELFTEST_CT_MAX_LEN]; 441 size_t i; 442 int ret; 443 444 mbedtls_ccm_init( &ctx ); 445 446 if( mbedtls_ccm_setkey( &ctx, MBEDTLS_CIPHER_ID_AES, key, 8 * sizeof key ) != 0 ) 447 { 448 if( verbose != 0 ) 449 mbedtls_printf( " CCM: setup failed" ); 450 451 return( 1 ); 452 } 453 454 for( i = 0; i < NB_TESTS; i++ ) 455 { 456 if( verbose != 0 ) 457 mbedtls_printf( " CCM-AES #%u: ", (unsigned int) i + 1 ); 458 459 memset( plaintext, 0, CCM_SELFTEST_PT_MAX_LEN ); 460 memset( ciphertext, 0, CCM_SELFTEST_CT_MAX_LEN ); 461 memcpy( plaintext, msg, msg_len[i] ); 462 463 ret = mbedtls_ccm_encrypt_and_tag( &ctx, msg_len[i], 464 iv, iv_len[i], ad, add_len[i], 465 plaintext, ciphertext, 466 ciphertext + msg_len[i], tag_len[i] ); 467 468 if( ret != 0 || 469 memcmp( ciphertext, res[i], msg_len[i] + tag_len[i] ) != 0 ) 470 { 471 if( verbose != 0 ) 472 mbedtls_printf( "failed\n" ); 473 474 return( 1 ); 475 } 476 memset( plaintext, 0, CCM_SELFTEST_PT_MAX_LEN ); 477 478 ret = mbedtls_ccm_auth_decrypt( &ctx, msg_len[i], 479 iv, iv_len[i], ad, add_len[i], 480 ciphertext, plaintext, 481 ciphertext + msg_len[i], tag_len[i] ); 482 483 if( ret != 0 || 484 memcmp( plaintext, msg, msg_len[i] ) != 0 ) 485 { 486 if( verbose != 0 ) 487 mbedtls_printf( "failed\n" ); 488 489 return( 1 ); 490 } 491 492 if( verbose != 0 ) 493 mbedtls_printf( "passed\n" ); 494 } 495 496 mbedtls_ccm_free( &ctx ); 497 498 if( verbose != 0 ) 499 mbedtls_printf( "\n" ); 500 501 return( 0 ); 502 } 503 504 #endif /* MBEDTLS_SELF_TEST && MBEDTLS_AES_C */ 505 506 #endif /* MBEDTLS_CCM_C */ 507