1 // SPDX-License-Identifier: Apache-2.0 2 /* 3 * Public Key layer for writing key files and structures 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_PK_WRITE_C) 29 30 #include "mbedtls/pk.h" 31 #include "mbedtls/asn1write.h" 32 #include "mbedtls/oid.h" 33 #include "mbedtls/platform_util.h" 34 35 #include <string.h> 36 37 #if defined(MBEDTLS_RSA_C) 38 #include "mbedtls/rsa.h" 39 #endif 40 #if defined(MBEDTLS_ECP_C) 41 #include "mbedtls/ecp.h" 42 #endif 43 #if defined(MBEDTLS_ECDSA_C) 44 #include "mbedtls/ecdsa.h" 45 #endif 46 #if defined(MBEDTLS_PEM_WRITE_C) 47 #include "mbedtls/pem.h" 48 #endif 49 50 #if defined(MBEDTLS_PLATFORM_C) 51 #include "mbedtls/platform.h" 52 #else 53 #include <stdlib.h> 54 #define mbedtls_calloc calloc 55 #define mbedtls_free free 56 #endif 57 58 /* Parameter validation macros based on platform_util.h */ 59 #define PK_VALIDATE_RET( cond ) \ 60 MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_PK_BAD_INPUT_DATA ) 61 #define PK_VALIDATE( cond ) \ 62 MBEDTLS_INTERNAL_VALIDATE( cond ) 63 64 #if defined(MBEDTLS_RSA_C) 65 /* 66 * RSAPublicKey ::= SEQUENCE { 67 * modulus INTEGER, -- n 68 * publicExponent INTEGER -- e 69 * } 70 */ 71 static int pk_write_rsa_pubkey( unsigned char **p, unsigned char *start, 72 mbedtls_rsa_context *rsa ) 73 { 74 int ret; 75 size_t len = 0; 76 mbedtls_mpi T; 77 78 mbedtls_mpi_init( &T ); 79 80 /* Export E */ 81 if ( ( ret = mbedtls_rsa_export( rsa, NULL, NULL, NULL, NULL, &T ) ) != 0 || 82 ( ret = mbedtls_asn1_write_mpi( p, start, &T ) ) < 0 ) 83 goto end_of_export; 84 len += ret; 85 86 /* Export N */ 87 if ( ( ret = mbedtls_rsa_export( rsa, &T, NULL, NULL, NULL, NULL ) ) != 0 || 88 ( ret = mbedtls_asn1_write_mpi( p, start, &T ) ) < 0 ) 89 goto end_of_export; 90 len += ret; 91 92 end_of_export: 93 94 mbedtls_mpi_free( &T ); 95 if( ret < 0 ) 96 return( ret ); 97 98 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) ); 99 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_CONSTRUCTED | 100 MBEDTLS_ASN1_SEQUENCE ) ); 101 102 return( (int) len ); 103 } 104 #endif /* MBEDTLS_RSA_C */ 105 106 #if defined(MBEDTLS_ECP_C) 107 /* 108 * EC public key is an EC point 109 */ 110 static int pk_write_ec_pubkey( unsigned char **p, unsigned char *start, 111 mbedtls_ecp_keypair *ec ) 112 { 113 int ret; 114 size_t len = 0; 115 unsigned char buf[MBEDTLS_ECP_MAX_PT_LEN]; 116 117 if( ( ret = mbedtls_ecp_point_write_binary( &ec->grp, &ec->Q, 118 MBEDTLS_ECP_PF_UNCOMPRESSED, 119 &len, buf, sizeof( buf ) ) ) != 0 ) 120 { 121 return( ret ); 122 } 123 124 if( *p < start || (size_t)( *p - start ) < len ) 125 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL ); 126 127 *p -= len; 128 memcpy( *p, buf, len ); 129 130 return( (int) len ); 131 } 132 133 /* 134 * ECParameters ::= CHOICE { 135 * namedCurve OBJECT IDENTIFIER 136 * } 137 */ 138 static int pk_write_ec_param( unsigned char **p, unsigned char *start, 139 mbedtls_ecp_keypair *ec ) 140 { 141 int ret; 142 size_t len = 0; 143 const char *oid; 144 size_t oid_len; 145 146 if( ( ret = mbedtls_oid_get_oid_by_ec_grp( ec->grp.id, &oid, &oid_len ) ) != 0 ) 147 return( ret ); 148 149 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_oid( p, start, oid, oid_len ) ); 150 151 return( (int) len ); 152 } 153 #endif /* MBEDTLS_ECP_C */ 154 155 int mbedtls_pk_write_pubkey( unsigned char **p, unsigned char *start, 156 const mbedtls_pk_context *key ) 157 { 158 int ret; 159 size_t len = 0; 160 161 PK_VALIDATE_RET( p != NULL ); 162 PK_VALIDATE_RET( *p != NULL ); 163 PK_VALIDATE_RET( start != NULL ); 164 PK_VALIDATE_RET( key != NULL ); 165 166 #if defined(MBEDTLS_RSA_C) 167 if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_RSA ) 168 MBEDTLS_ASN1_CHK_ADD( len, pk_write_rsa_pubkey( p, start, mbedtls_pk_rsa( *key ) ) ); 169 else 170 #endif 171 #if defined(MBEDTLS_ECP_C) 172 if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_ECKEY ) 173 MBEDTLS_ASN1_CHK_ADD( len, pk_write_ec_pubkey( p, start, mbedtls_pk_ec( *key ) ) ); 174 else 175 #endif 176 return( MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE ); 177 178 return( (int) len ); 179 } 180 181 int mbedtls_pk_write_pubkey_der( mbedtls_pk_context *key, unsigned char *buf, size_t size ) 182 { 183 int ret; 184 unsigned char *c; 185 size_t len = 0, par_len = 0, oid_len; 186 const char *oid; 187 188 PK_VALIDATE_RET( key != NULL ); 189 if( size == 0 ) 190 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL ); 191 PK_VALIDATE_RET( buf != NULL ); 192 193 c = buf + size; 194 195 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_pk_write_pubkey( &c, buf, key ) ); 196 197 if( c - buf < 1 ) 198 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL ); 199 200 /* 201 * SubjectPublicKeyInfo ::= SEQUENCE { 202 * algorithm AlgorithmIdentifier, 203 * subjectPublicKey BIT STRING } 204 */ 205 *--c = 0; 206 len += 1; 207 208 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) ); 209 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_BIT_STRING ) ); 210 211 if( ( ret = mbedtls_oid_get_oid_by_pk_alg( mbedtls_pk_get_type( key ), 212 &oid, &oid_len ) ) != 0 ) 213 { 214 return( ret ); 215 } 216 217 #if defined(MBEDTLS_ECP_C) 218 if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_ECKEY ) 219 { 220 MBEDTLS_ASN1_CHK_ADD( par_len, pk_write_ec_param( &c, buf, mbedtls_pk_ec( *key ) ) ); 221 } 222 #endif 223 224 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_algorithm_identifier( &c, buf, oid, oid_len, 225 par_len ) ); 226 227 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) ); 228 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_CONSTRUCTED | 229 MBEDTLS_ASN1_SEQUENCE ) ); 230 231 return( (int) len ); 232 } 233 234 int mbedtls_pk_write_key_der( mbedtls_pk_context *key, unsigned char *buf, size_t size ) 235 { 236 int ret; 237 unsigned char *c; 238 size_t len = 0; 239 240 PK_VALIDATE_RET( key != NULL ); 241 if( size == 0 ) 242 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL ); 243 PK_VALIDATE_RET( buf != NULL ); 244 245 c = buf + size; 246 247 #if defined(MBEDTLS_RSA_C) 248 if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_RSA ) 249 { 250 mbedtls_mpi T; /* Temporary holding the exported parameters */ 251 mbedtls_rsa_context *rsa = mbedtls_pk_rsa( *key ); 252 253 /* 254 * Export the parameters one after another to avoid simultaneous copies. 255 */ 256 257 mbedtls_mpi_init( &T ); 258 259 /* Export QP */ 260 if( ( ret = mbedtls_rsa_export_crt( rsa, NULL, NULL, &T ) ) != 0 || 261 ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 ) 262 goto end_of_export; 263 len += ret; 264 265 /* Export DQ */ 266 if( ( ret = mbedtls_rsa_export_crt( rsa, NULL, &T, NULL ) ) != 0 || 267 ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 ) 268 goto end_of_export; 269 len += ret; 270 271 /* Export DP */ 272 if( ( ret = mbedtls_rsa_export_crt( rsa, &T, NULL, NULL ) ) != 0 || 273 ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 ) 274 goto end_of_export; 275 len += ret; 276 277 /* Export Q */ 278 if ( ( ret = mbedtls_rsa_export( rsa, NULL, NULL, 279 &T, NULL, NULL ) ) != 0 || 280 ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 ) 281 goto end_of_export; 282 len += ret; 283 284 /* Export P */ 285 if ( ( ret = mbedtls_rsa_export( rsa, NULL, &T, 286 NULL, NULL, NULL ) ) != 0 || 287 ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 ) 288 goto end_of_export; 289 len += ret; 290 291 /* Export D */ 292 if ( ( ret = mbedtls_rsa_export( rsa, NULL, NULL, 293 NULL, &T, NULL ) ) != 0 || 294 ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 ) 295 goto end_of_export; 296 len += ret; 297 298 /* Export E */ 299 if ( ( ret = mbedtls_rsa_export( rsa, NULL, NULL, 300 NULL, NULL, &T ) ) != 0 || 301 ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 ) 302 goto end_of_export; 303 len += ret; 304 305 /* Export N */ 306 if ( ( ret = mbedtls_rsa_export( rsa, &T, NULL, 307 NULL, NULL, NULL ) ) != 0 || 308 ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 ) 309 goto end_of_export; 310 len += ret; 311 312 end_of_export: 313 314 mbedtls_mpi_free( &T ); 315 if( ret < 0 ) 316 return( ret ); 317 318 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_int( &c, buf, 0 ) ); 319 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) ); 320 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, 321 buf, MBEDTLS_ASN1_CONSTRUCTED | 322 MBEDTLS_ASN1_SEQUENCE ) ); 323 } 324 else 325 #endif /* MBEDTLS_RSA_C */ 326 #if defined(MBEDTLS_ECP_C) 327 if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_ECKEY ) 328 { 329 mbedtls_ecp_keypair *ec = mbedtls_pk_ec( *key ); 330 size_t pub_len = 0, par_len = 0; 331 332 /* 333 * RFC 5915, or SEC1 Appendix C.4 334 * 335 * ECPrivateKey ::= SEQUENCE { 336 * version INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1), 337 * privateKey OCTET STRING, 338 * parameters [0] ECParameters {{ NamedCurve }} OPTIONAL, 339 * publicKey [1] BIT STRING OPTIONAL 340 * } 341 */ 342 343 /* publicKey */ 344 MBEDTLS_ASN1_CHK_ADD( pub_len, pk_write_ec_pubkey( &c, buf, ec ) ); 345 346 if( c - buf < 1 ) 347 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL ); 348 *--c = 0; 349 pub_len += 1; 350 351 MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_asn1_write_len( &c, buf, pub_len ) ); 352 MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_BIT_STRING ) ); 353 354 MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_asn1_write_len( &c, buf, pub_len ) ); 355 MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_asn1_write_tag( &c, buf, 356 MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 1 ) ); 357 len += pub_len; 358 359 /* parameters */ 360 MBEDTLS_ASN1_CHK_ADD( par_len, pk_write_ec_param( &c, buf, ec ) ); 361 362 MBEDTLS_ASN1_CHK_ADD( par_len, mbedtls_asn1_write_len( &c, buf, par_len ) ); 363 MBEDTLS_ASN1_CHK_ADD( par_len, mbedtls_asn1_write_tag( &c, buf, 364 MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 0 ) ); 365 len += par_len; 366 367 /* privateKey: write as MPI then fix tag */ 368 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &c, buf, &ec->d ) ); 369 *c = MBEDTLS_ASN1_OCTET_STRING; 370 371 /* version */ 372 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_int( &c, buf, 1 ) ); 373 374 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) ); 375 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_CONSTRUCTED | 376 MBEDTLS_ASN1_SEQUENCE ) ); 377 } 378 else 379 #endif /* MBEDTLS_ECP_C */ 380 return( MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE ); 381 382 return( (int) len ); 383 } 384 385 #if defined(MBEDTLS_PEM_WRITE_C) 386 387 #define PEM_BEGIN_PUBLIC_KEY "-----BEGIN PUBLIC KEY-----\n" 388 #define PEM_END_PUBLIC_KEY "-----END PUBLIC KEY-----\n" 389 390 #define PEM_BEGIN_PRIVATE_KEY_RSA "-----BEGIN RSA PRIVATE KEY-----\n" 391 #define PEM_END_PRIVATE_KEY_RSA "-----END RSA PRIVATE KEY-----\n" 392 #define PEM_BEGIN_PRIVATE_KEY_EC "-----BEGIN EC PRIVATE KEY-----\n" 393 #define PEM_END_PRIVATE_KEY_EC "-----END EC PRIVATE KEY-----\n" 394 395 /* 396 * Max sizes of key per types. Shown as tag + len (+ content). 397 */ 398 399 #if defined(MBEDTLS_RSA_C) 400 /* 401 * RSA public keys: 402 * SubjectPublicKeyInfo ::= SEQUENCE { 1 + 3 403 * algorithm AlgorithmIdentifier, 1 + 1 (sequence) 404 * + 1 + 1 + 9 (rsa oid) 405 * + 1 + 1 (params null) 406 * subjectPublicKey BIT STRING } 1 + 3 + (1 + below) 407 * RSAPublicKey ::= SEQUENCE { 1 + 3 408 * modulus INTEGER, -- n 1 + 3 + MPI_MAX + 1 409 * publicExponent INTEGER -- e 1 + 3 + MPI_MAX + 1 410 * } 411 */ 412 #define RSA_PUB_DER_MAX_BYTES 38 + 2 * MBEDTLS_MPI_MAX_SIZE 413 414 /* 415 * RSA private keys: 416 * RSAPrivateKey ::= SEQUENCE { 1 + 3 417 * version Version, 1 + 1 + 1 418 * modulus INTEGER, 1 + 3 + MPI_MAX + 1 419 * publicExponent INTEGER, 1 + 3 + MPI_MAX + 1 420 * privateExponent INTEGER, 1 + 3 + MPI_MAX + 1 421 * prime1 INTEGER, 1 + 3 + MPI_MAX / 2 + 1 422 * prime2 INTEGER, 1 + 3 + MPI_MAX / 2 + 1 423 * exponent1 INTEGER, 1 + 3 + MPI_MAX / 2 + 1 424 * exponent2 INTEGER, 1 + 3 + MPI_MAX / 2 + 1 425 * coefficient INTEGER, 1 + 3 + MPI_MAX / 2 + 1 426 * otherPrimeInfos OtherPrimeInfos OPTIONAL 0 (not supported) 427 * } 428 */ 429 #define MPI_MAX_SIZE_2 MBEDTLS_MPI_MAX_SIZE / 2 + \ 430 MBEDTLS_MPI_MAX_SIZE % 2 431 #define RSA_PRV_DER_MAX_BYTES 47 + 3 * MBEDTLS_MPI_MAX_SIZE \ 432 + 5 * MPI_MAX_SIZE_2 433 434 #else /* MBEDTLS_RSA_C */ 435 436 #define RSA_PUB_DER_MAX_BYTES 0 437 #define RSA_PRV_DER_MAX_BYTES 0 438 439 #endif /* MBEDTLS_RSA_C */ 440 441 #if defined(MBEDTLS_ECP_C) 442 /* 443 * EC public keys: 444 * SubjectPublicKeyInfo ::= SEQUENCE { 1 + 2 445 * algorithm AlgorithmIdentifier, 1 + 1 (sequence) 446 * + 1 + 1 + 7 (ec oid) 447 * + 1 + 1 + 9 (namedCurve oid) 448 * subjectPublicKey BIT STRING 1 + 2 + 1 [1] 449 * + 1 (point format) [1] 450 * + 2 * ECP_MAX (coords) [1] 451 * } 452 */ 453 #define ECP_PUB_DER_MAX_BYTES 30 + 2 * MBEDTLS_ECP_MAX_BYTES 454 455 /* 456 * EC private keys: 457 * ECPrivateKey ::= SEQUENCE { 1 + 2 458 * version INTEGER , 1 + 1 + 1 459 * privateKey OCTET STRING, 1 + 1 + ECP_MAX 460 * parameters [0] ECParameters OPTIONAL, 1 + 1 + (1 + 1 + 9) 461 * publicKey [1] BIT STRING OPTIONAL 1 + 2 + [1] above 462 * } 463 */ 464 #define ECP_PRV_DER_MAX_BYTES 29 + 3 * MBEDTLS_ECP_MAX_BYTES 465 466 #else /* MBEDTLS_ECP_C */ 467 468 #define ECP_PUB_DER_MAX_BYTES 0 469 #define ECP_PRV_DER_MAX_BYTES 0 470 471 #endif /* MBEDTLS_ECP_C */ 472 473 #define PUB_DER_MAX_BYTES RSA_PUB_DER_MAX_BYTES > ECP_PUB_DER_MAX_BYTES ? \ 474 RSA_PUB_DER_MAX_BYTES : ECP_PUB_DER_MAX_BYTES 475 #define PRV_DER_MAX_BYTES RSA_PRV_DER_MAX_BYTES > ECP_PRV_DER_MAX_BYTES ? \ 476 RSA_PRV_DER_MAX_BYTES : ECP_PRV_DER_MAX_BYTES 477 478 int mbedtls_pk_write_pubkey_pem( mbedtls_pk_context *key, unsigned char *buf, size_t size ) 479 { 480 int ret; 481 unsigned char output_buf[PUB_DER_MAX_BYTES]; 482 size_t olen = 0; 483 484 PK_VALIDATE_RET( key != NULL ); 485 PK_VALIDATE_RET( buf != NULL || size == 0 ); 486 487 if( ( ret = mbedtls_pk_write_pubkey_der( key, output_buf, 488 sizeof(output_buf) ) ) < 0 ) 489 { 490 return( ret ); 491 } 492 493 if( ( ret = mbedtls_pem_write_buffer( PEM_BEGIN_PUBLIC_KEY, PEM_END_PUBLIC_KEY, 494 output_buf + sizeof(output_buf) - ret, 495 ret, buf, size, &olen ) ) != 0 ) 496 { 497 return( ret ); 498 } 499 500 return( 0 ); 501 } 502 503 int mbedtls_pk_write_key_pem( mbedtls_pk_context *key, unsigned char *buf, size_t size ) 504 { 505 int ret; 506 unsigned char output_buf[PRV_DER_MAX_BYTES]; 507 const char *begin, *end; 508 size_t olen = 0; 509 510 PK_VALIDATE_RET( key != NULL ); 511 PK_VALIDATE_RET( buf != NULL || size == 0 ); 512 513 if( ( ret = mbedtls_pk_write_key_der( key, output_buf, sizeof(output_buf) ) ) < 0 ) 514 return( ret ); 515 516 #if defined(MBEDTLS_RSA_C) 517 if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_RSA ) 518 { 519 begin = PEM_BEGIN_PRIVATE_KEY_RSA; 520 end = PEM_END_PRIVATE_KEY_RSA; 521 } 522 else 523 #endif 524 #if defined(MBEDTLS_ECP_C) 525 if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_ECKEY ) 526 { 527 begin = PEM_BEGIN_PRIVATE_KEY_EC; 528 end = PEM_END_PRIVATE_KEY_EC; 529 } 530 else 531 #endif 532 return( MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE ); 533 534 if( ( ret = mbedtls_pem_write_buffer( begin, end, 535 output_buf + sizeof(output_buf) - ret, 536 ret, buf, size, &olen ) ) != 0 ) 537 { 538 return( ret ); 539 } 540 541 return( 0 ); 542 } 543 #endif /* MBEDTLS_PEM_WRITE_C */ 544 545 #endif /* MBEDTLS_PK_WRITE_C */ 546