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