1 // SPDX-License-Identifier: Apache-2.0 2 /* 3 * ASN.1 buffer writing functionality 4 * 5 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved 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 #if !defined(MBEDTLS_CONFIG_FILE) 23 #include "mbedtls/config.h" 24 #else 25 #include MBEDTLS_CONFIG_FILE 26 #endif 27 28 #if defined(MBEDTLS_ASN1_WRITE_C) 29 30 #include "mbedtls/asn1write.h" 31 #include "mbedtls/error.h" 32 33 #include <string.h> 34 35 #if defined(MBEDTLS_PLATFORM_C) 36 #include "mbedtls/platform.h" 37 #else 38 #include <stdlib.h> 39 #define mbedtls_calloc calloc 40 #define mbedtls_free free 41 #endif 42 43 int mbedtls_asn1_write_len( unsigned char **p, unsigned char *start, size_t len ) 44 { 45 if( len < 0x80 ) 46 { 47 if( *p - start < 1 ) 48 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL ); 49 50 *--(*p) = (unsigned char) len; 51 return( 1 ); 52 } 53 54 if( len <= 0xFF ) 55 { 56 if( *p - start < 2 ) 57 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL ); 58 59 *--(*p) = (unsigned char) len; 60 *--(*p) = 0x81; 61 return( 2 ); 62 } 63 64 if( len <= 0xFFFF ) 65 { 66 if( *p - start < 3 ) 67 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL ); 68 69 *--(*p) = ( len ) & 0xFF; 70 *--(*p) = ( len >> 8 ) & 0xFF; 71 *--(*p) = 0x82; 72 return( 3 ); 73 } 74 75 if( len <= 0xFFFFFF ) 76 { 77 if( *p - start < 4 ) 78 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL ); 79 80 *--(*p) = ( len ) & 0xFF; 81 *--(*p) = ( len >> 8 ) & 0xFF; 82 *--(*p) = ( len >> 16 ) & 0xFF; 83 *--(*p) = 0x83; 84 return( 4 ); 85 } 86 87 #if SIZE_MAX > 0xFFFFFFFF 88 if( len <= 0xFFFFFFFF ) 89 #endif 90 { 91 if( *p - start < 5 ) 92 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL ); 93 94 *--(*p) = ( len ) & 0xFF; 95 *--(*p) = ( len >> 8 ) & 0xFF; 96 *--(*p) = ( len >> 16 ) & 0xFF; 97 *--(*p) = ( len >> 24 ) & 0xFF; 98 *--(*p) = 0x84; 99 return( 5 ); 100 } 101 102 #if SIZE_MAX > 0xFFFFFFFF 103 return( MBEDTLS_ERR_ASN1_INVALID_LENGTH ); 104 #endif 105 } 106 107 int mbedtls_asn1_write_tag( unsigned char **p, unsigned char *start, unsigned char tag ) 108 { 109 if( *p - start < 1 ) 110 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL ); 111 112 *--(*p) = tag; 113 114 return( 1 ); 115 } 116 117 int mbedtls_asn1_write_raw_buffer( unsigned char **p, unsigned char *start, 118 const unsigned char *buf, size_t size ) 119 { 120 size_t len = 0; 121 122 if( *p < start || (size_t)( *p - start ) < size ) 123 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL ); 124 125 len = size; 126 (*p) -= len; 127 memcpy( *p, buf, len ); 128 129 return( (int) len ); 130 } 131 132 #if defined(MBEDTLS_BIGNUM_C) 133 int mbedtls_asn1_write_mpi( unsigned char **p, unsigned char *start, const mbedtls_mpi *X ) 134 { 135 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; 136 size_t len = 0; 137 138 // Write the MPI 139 // 140 len = mbedtls_mpi_size( X ); 141 142 if( *p < start || (size_t)( *p - start ) < len ) 143 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL ); 144 145 (*p) -= len; 146 MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( X, *p, len ) ); 147 148 // DER format assumes 2s complement for numbers, so the leftmost bit 149 // should be 0 for positive numbers and 1 for negative numbers. 150 // 151 if( X->s ==1 && **p & 0x80 ) 152 { 153 if( *p - start < 1 ) 154 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL ); 155 156 *--(*p) = 0x00; 157 len += 1; 158 } 159 160 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) ); 161 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_INTEGER ) ); 162 163 ret = (int) len; 164 165 cleanup: 166 return( ret ); 167 } 168 #endif /* MBEDTLS_BIGNUM_C */ 169 170 int mbedtls_asn1_write_null( unsigned char **p, unsigned char *start ) 171 { 172 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; 173 size_t len = 0; 174 175 // Write NULL 176 // 177 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, 0) ); 178 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_NULL ) ); 179 180 return( (int) len ); 181 } 182 183 int mbedtls_asn1_write_oid( unsigned char **p, unsigned char *start, 184 const char *oid, size_t oid_len ) 185 { 186 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; 187 size_t len = 0; 188 189 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start, 190 (const unsigned char *) oid, oid_len ) ); 191 MBEDTLS_ASN1_CHK_ADD( len , mbedtls_asn1_write_len( p, start, len ) ); 192 MBEDTLS_ASN1_CHK_ADD( len , mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_OID ) ); 193 194 return( (int) len ); 195 } 196 197 int mbedtls_asn1_write_algorithm_identifier( unsigned char **p, unsigned char *start, 198 const char *oid, size_t oid_len, 199 size_t par_len ) 200 { 201 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; 202 size_t len = 0; 203 204 if( par_len == 0 ) 205 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_null( p, start ) ); 206 else 207 len += par_len; 208 209 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_oid( p, start, oid, oid_len ) ); 210 211 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) ); 212 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, 213 MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ); 214 215 return( (int) len ); 216 } 217 218 int mbedtls_asn1_write_bool( unsigned char **p, unsigned char *start, int boolean ) 219 { 220 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; 221 size_t len = 0; 222 223 if( *p - start < 1 ) 224 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL ); 225 226 *--(*p) = (boolean) ? 255 : 0; 227 len++; 228 229 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) ); 230 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_BOOLEAN ) ); 231 232 return( (int) len ); 233 } 234 235 static int asn1_write_tagged_int( unsigned char **p, unsigned char *start, int val, int tag ) 236 { 237 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; 238 size_t len = 0; 239 240 do 241 { 242 if( *p - start < 1 ) 243 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL ); 244 len += 1; 245 *--(*p) = val & 0xff; 246 val >>= 8; 247 } 248 while( val > 0 ); 249 250 if( **p & 0x80 ) 251 { 252 if( *p - start < 1 ) 253 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL ); 254 *--(*p) = 0x00; 255 len += 1; 256 } 257 258 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) ); 259 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, tag ) ); 260 261 return( (int) len ); 262 } 263 264 int mbedtls_asn1_write_int( unsigned char **p, unsigned char *start, int val ) 265 { 266 return( asn1_write_tagged_int( p, start, val, MBEDTLS_ASN1_INTEGER ) ); 267 } 268 269 int mbedtls_asn1_write_enum( unsigned char **p, unsigned char *start, int val ) 270 { 271 return( asn1_write_tagged_int( p, start, val, MBEDTLS_ASN1_ENUMERATED ) ); 272 } 273 274 int mbedtls_asn1_write_tagged_string( unsigned char **p, unsigned char *start, int tag, 275 const char *text, size_t text_len ) 276 { 277 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; 278 size_t len = 0; 279 280 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start, 281 (const unsigned char *) text, text_len ) ); 282 283 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) ); 284 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, tag ) ); 285 286 return( (int) len ); 287 } 288 289 int mbedtls_asn1_write_utf8_string( unsigned char **p, unsigned char *start, 290 const char *text, size_t text_len ) 291 { 292 return( mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_UTF8_STRING, text, text_len) ); 293 } 294 295 int mbedtls_asn1_write_printable_string( unsigned char **p, unsigned char *start, 296 const char *text, size_t text_len ) 297 { 298 return( mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_PRINTABLE_STRING, text, text_len) ); 299 } 300 301 int mbedtls_asn1_write_ia5_string( unsigned char **p, unsigned char *start, 302 const char *text, size_t text_len ) 303 { 304 return( mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_IA5_STRING, text, text_len) ); 305 } 306 307 int mbedtls_asn1_write_named_bitstring( unsigned char **p, 308 unsigned char *start, 309 const unsigned char *buf, 310 size_t bits ) 311 { 312 size_t unused_bits, byte_len; 313 const unsigned char *cur_byte; 314 unsigned char cur_byte_shifted; 315 unsigned char bit; 316 317 byte_len = ( bits + 7 ) / 8; 318 unused_bits = ( byte_len * 8 ) - bits; 319 320 /* 321 * Named bitstrings require that trailing 0s are excluded in the encoding 322 * of the bitstring. Trailing 0s are considered part of the 'unused' bits 323 * when encoding this value in the first content octet 324 */ 325 if( bits != 0 ) 326 { 327 cur_byte = buf + byte_len - 1; 328 cur_byte_shifted = *cur_byte >> unused_bits; 329 330 for( ; ; ) 331 { 332 bit = cur_byte_shifted & 0x1; 333 cur_byte_shifted >>= 1; 334 335 if( bit != 0 ) 336 break; 337 338 bits--; 339 if( bits == 0 ) 340 break; 341 342 if( bits % 8 == 0 ) 343 cur_byte_shifted = *--cur_byte; 344 } 345 } 346 347 return( mbedtls_asn1_write_bitstring( p, start, buf, bits ) ); 348 } 349 350 int mbedtls_asn1_write_bitstring( unsigned char **p, unsigned char *start, 351 const unsigned char *buf, size_t bits ) 352 { 353 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; 354 size_t len = 0; 355 size_t unused_bits, byte_len; 356 357 byte_len = ( bits + 7 ) / 8; 358 unused_bits = ( byte_len * 8 ) - bits; 359 360 if( *p < start || (size_t)( *p - start ) < byte_len + 1 ) 361 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL ); 362 363 len = byte_len + 1; 364 365 /* Write the bitstring. Ensure the unused bits are zeroed */ 366 if( byte_len > 0 ) 367 { 368 byte_len--; 369 *--( *p ) = buf[byte_len] & ~( ( 0x1 << unused_bits ) - 1 ); 370 ( *p ) -= byte_len; 371 memcpy( *p, buf, byte_len ); 372 } 373 374 /* Write unused bits */ 375 *--( *p ) = (unsigned char)unused_bits; 376 377 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) ); 378 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_BIT_STRING ) ); 379 380 return( (int) len ); 381 } 382 383 int mbedtls_asn1_write_octet_string( unsigned char **p, unsigned char *start, 384 const unsigned char *buf, size_t size ) 385 { 386 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; 387 size_t len = 0; 388 389 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start, buf, size ) ); 390 391 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) ); 392 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_OCTET_STRING ) ); 393 394 return( (int) len ); 395 } 396 397 398 /* This is a copy of the ASN.1 parsing function mbedtls_asn1_find_named_data(), 399 * which is replicated to avoid a dependency ASN1_WRITE_C on ASN1_PARSE_C. */ 400 static mbedtls_asn1_named_data *asn1_find_named_data( 401 mbedtls_asn1_named_data *list, 402 const char *oid, size_t len ) 403 { 404 while( list != NULL ) 405 { 406 if( list->oid.len == len && 407 memcmp( list->oid.p, oid, len ) == 0 ) 408 { 409 break; 410 } 411 412 list = list->next; 413 } 414 415 return( list ); 416 } 417 418 mbedtls_asn1_named_data *mbedtls_asn1_store_named_data( 419 mbedtls_asn1_named_data **head, 420 const char *oid, size_t oid_len, 421 const unsigned char *val, 422 size_t val_len ) 423 { 424 mbedtls_asn1_named_data *cur; 425 426 if( ( cur = asn1_find_named_data( *head, oid, oid_len ) ) == NULL ) 427 { 428 // Add new entry if not present yet based on OID 429 // 430 cur = (mbedtls_asn1_named_data*)mbedtls_calloc( 1, 431 sizeof(mbedtls_asn1_named_data) ); 432 if( cur == NULL ) 433 return( NULL ); 434 435 cur->oid.len = oid_len; 436 cur->oid.p = mbedtls_calloc( 1, oid_len ); 437 if( cur->oid.p == NULL ) 438 { 439 mbedtls_free( cur ); 440 return( NULL ); 441 } 442 443 memcpy( cur->oid.p, oid, oid_len ); 444 445 cur->val.len = val_len; 446 if( val_len != 0 ) 447 { 448 cur->val.p = mbedtls_calloc( 1, val_len ); 449 if( cur->val.p == NULL ) 450 { 451 mbedtls_free( cur->oid.p ); 452 mbedtls_free( cur ); 453 return( NULL ); 454 } 455 } 456 457 cur->next = *head; 458 *head = cur; 459 } 460 else if( val_len == 0 ) 461 { 462 mbedtls_free( cur->val.p ); 463 cur->val.p = NULL; 464 } 465 else if( cur->val.len != val_len ) 466 { 467 /* 468 * Enlarge existing value buffer if needed 469 * Preserve old data until the allocation succeeded, to leave list in 470 * a consistent state in case allocation fails. 471 */ 472 void *p = mbedtls_calloc( 1, val_len ); 473 if( p == NULL ) 474 return( NULL ); 475 476 mbedtls_free( cur->val.p ); 477 cur->val.p = p; 478 cur->val.len = val_len; 479 } 480 481 if( val != NULL ) 482 memcpy( cur->val.p, val, val_len ); 483 484 return( cur ); 485 } 486 #endif /* MBEDTLS_ASN1_WRITE_C */ 487