git.zerfleddert.de Git - proxmark3-svn/blob - common/mbedtls/pkwrite.c

   1 /*
   2  *  Public Key layer for writing key files and structures
   3  *
   4  *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
   5  *  SPDX-License-Identifier: GPL-2.0
   6  *
   7  *  This program is free software; you can redistribute it and/or modify
   8  *  it under the terms of the GNU General Public License as published by
   9  *  the Free Software Foundation; either version 2 of the License, or
  10  *  (at your option) any later version.
  11  *
  12  *  This program is distributed in the hope that it will be useful,
  13  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  *  GNU General Public License for more details.
  16  *
  17  *  You should have received a copy of the GNU General Public License along
  18  *  with this program; if not, write to the Free Software Foundation, Inc.,
  19  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  *  This file is part of mbed TLS (https://tls.mbed.org)
  22  */
  23
  24 #if !defined(MBEDTLS_CONFIG_FILE)
  25 #include "mbedtls/config.h"
  26 #else
  27 #include MBEDTLS_CONFIG_FILE
  28 #endif
  29
  30 #if defined(MBEDTLS_PK_WRITE_C)
  31
  32 #include "mbedtls/pk.h"
  33 #include "mbedtls/asn1write.h"
  34 #include "mbedtls/oid.h"
  35
  36 #include <string.h>
  37
  38 #if defined(MBEDTLS_RSA_C)
  39 #include "mbedtls/rsa.h"
  40 #endif
  41 #if defined(MBEDTLS_ECP_C)
  42 #include "mbedtls/ecp.h"
  43 #endif
  44 #if defined(MBEDTLS_ECDSA_C)
  45 #include "mbedtls/ecdsa.h"
  46 #endif
  47 #if defined(MBEDTLS_PEM_WRITE_C)
  48 #include "mbedtls/pem.h"
  49 #endif
  50
  51 #if defined(MBEDTLS_PLATFORM_C)
  52 #include "mbedtls/platform.h"
  53 #else
  54 #include <stdlib.h>
  55 #define mbedtls_calloc    calloc
  56 #define mbedtls_free       free
  57 #endif
  58
  59 #if defined(MBEDTLS_RSA_C)
  60 /*
  61  *  RSAPublicKey ::= SEQUENCE {
  62  *      modulus           INTEGER,  -- n
  63  *      publicExponent    INTEGER   -- e
  64  *  }
  65  */
  66 static int pk_write_rsa_pubkey( unsigned char **p, unsigned char *start,
  67                                 mbedtls_rsa_context *rsa )
  68 {
  69     int ret;
  70     size_t len = 0;
  71     mbedtls_mpi T;
  72
  73     mbedtls_mpi_init( &T );
  74
  75     /* Export E */
  76     if ( ( ret = mbedtls_rsa_export( rsa, NULL, NULL, NULL, NULL, &T ) ) != 0 ||
  77          ( ret = mbedtls_asn1_write_mpi( p, start, &T ) ) < 0 )
  78         goto end_of_export;
  79     len += ret;
  80
  81     /* Export N */
  82     if ( ( ret = mbedtls_rsa_export( rsa, &T, NULL, NULL, NULL, NULL ) ) != 0 ||
  83          ( ret = mbedtls_asn1_write_mpi( p, start, &T ) ) < 0 )
  84         goto end_of_export;
  85     len += ret;
  86
  87 end_of_export:
  88
  89     mbedtls_mpi_free( &T );
  90     if( ret < 0 )
  91         return( ret );
  92
  93     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
  94     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_CONSTRUCTED |
  95                                                  MBEDTLS_ASN1_SEQUENCE ) );
  96
  97     return( (int) len );
  98 }
  99 #endif /* MBEDTLS_RSA_C */
 100
 101 #if defined(MBEDTLS_ECP_C)
 102 /*
 103  * EC public key is an EC point
 104  */
 105 static int pk_write_ec_pubkey( unsigned char **p, unsigned char *start,
 106                                mbedtls_ecp_keypair *ec )
 107 {
 108     int ret;
 109     size_t len = 0;
 110     unsigned char buf[MBEDTLS_ECP_MAX_PT_LEN];
 111
 112     if( ( ret = mbedtls_ecp_point_write_binary( &ec->grp, &ec->Q,
 113                                         MBEDTLS_ECP_PF_UNCOMPRESSED,
 114                                         &len, buf, sizeof( buf ) ) ) != 0 )
 115     {
 116         return( ret );
 117     }
 118
 119     if( *p < start || (size_t)( *p - start ) < len )
 120         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
 121
 122     *p -= len;
 123     memcpy( *p, buf, len );
 124
 125     return( (int) len );
 126 }
 127
 128 /*
 129  * ECParameters ::= CHOICE {
 130  *   namedCurve         OBJECT IDENTIFIER
 131  * }
 132  */
 133 static int pk_write_ec_param( unsigned char **p, unsigned char *start,
 134                               mbedtls_ecp_keypair *ec )
 135 {
 136     int ret;
 137     size_t len = 0;
 138     const char *oid;
 139     size_t oid_len;
 140
 141     if( ( ret = mbedtls_oid_get_oid_by_ec_grp( ec->grp.id, &oid, &oid_len ) ) != 0 )
 142         return( ret );
 143
 144     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_oid( p, start, oid, oid_len ) );
 145
 146     return( (int) len );
 147 }
 148 #endif /* MBEDTLS_ECP_C */
 149
 150 int mbedtls_pk_write_pubkey( unsigned char **p, unsigned char *start,
 151                              const mbedtls_pk_context *key )
 152 {
 153     int ret;
 154     size_t len = 0;
 155
 156 #if defined(MBEDTLS_RSA_C)
 157     if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_RSA )
 158         MBEDTLS_ASN1_CHK_ADD( len, pk_write_rsa_pubkey( p, start, mbedtls_pk_rsa( *key ) ) );
 159     else
 160 #endif
 161 #if defined(MBEDTLS_ECP_C)
 162     if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_ECKEY )
 163         MBEDTLS_ASN1_CHK_ADD( len, pk_write_ec_pubkey( p, start, mbedtls_pk_ec( *key ) ) );
 164     else
 165 #endif
 166         return( MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE );
 167
 168     return( (int) len );
 169 }
 170
 171 int mbedtls_pk_write_pubkey_der( mbedtls_pk_context *key, unsigned char *buf, size_t size )
 172 {
 173     int ret;
 174     unsigned char *c;
 175     size_t len = 0, par_len = 0, oid_len;
 176     const char *oid;
 177
 178     c = buf + size;
 179
 180     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_pk_write_pubkey( &c, buf, key ) );
 181
 182     if( c - buf < 1 )
 183         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
 184
 185     /*
 186      *  SubjectPublicKeyInfo  ::=  SEQUENCE  {
 187      *       algorithm            AlgorithmIdentifier,
 188      *       subjectPublicKey     BIT STRING }
 189      */
 190     *--c = 0;
 191     len += 1;
 192
 193     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
 194     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_BIT_STRING ) );
 195
 196     if( ( ret = mbedtls_oid_get_oid_by_pk_alg( mbedtls_pk_get_type( key ),
 197                                        &oid, &oid_len ) ) != 0 )
 198     {
 199         return( ret );
 200     }
 201
 202 #if defined(MBEDTLS_ECP_C)
 203     if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_ECKEY )
 204     {
 205         MBEDTLS_ASN1_CHK_ADD( par_len, pk_write_ec_param( &c, buf, mbedtls_pk_ec( *key ) ) );
 206     }
 207 #endif
 208
 209     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_algorithm_identifier( &c, buf, oid, oid_len,
 210                                                         par_len ) );
 211
 212     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
 213     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_CONSTRUCTED |
 214                                                 MBEDTLS_ASN1_SEQUENCE ) );
 215
 216     return( (int) len );
 217 }
 218
 219 int mbedtls_pk_write_key_der( mbedtls_pk_context *key, unsigned char *buf, size_t size )
 220 {
 221     int ret;
 222     unsigned char *c = buf + size;
 223     size_t len = 0;
 224
 225 #if defined(MBEDTLS_RSA_C)
 226     if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_RSA )
 227     {
 228         mbedtls_mpi T; /* Temporary holding the exported parameters */
 229         mbedtls_rsa_context *rsa = mbedtls_pk_rsa( *key );
 230
 231         /*
 232          * Export the parameters one after another to avoid simultaneous copies.
 233          */
 234
 235         mbedtls_mpi_init( &T );
 236
 237         /* Export QP */
 238         if( ( ret = mbedtls_rsa_export_crt( rsa, NULL, NULL, &T ) ) != 0 ||
 239             ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
 240             goto end_of_export;
 241         len += ret;
 242
 243         /* Export DQ */
 244         if( ( ret = mbedtls_rsa_export_crt( rsa, NULL, &T, NULL ) ) != 0 ||
 245             ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
 246             goto end_of_export;
 247         len += ret;
 248
 249         /* Export DP */
 250         if( ( ret = mbedtls_rsa_export_crt( rsa, &T, NULL, NULL ) ) != 0 ||
 251             ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
 252             goto end_of_export;
 253         len += ret;
 254
 255         /* Export Q */
 256         if ( ( ret = mbedtls_rsa_export( rsa, NULL, NULL,
 257                                          &T, NULL, NULL ) ) != 0 ||
 258              ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
 259             goto end_of_export;
 260         len += ret;
 261
 262         /* Export P */
 263         if ( ( ret = mbedtls_rsa_export( rsa, NULL, &T,
 264                                          NULL, NULL, NULL ) ) != 0 ||
 265              ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
 266             goto end_of_export;
 267         len += ret;
 268
 269         /* Export D */
 270         if ( ( ret = mbedtls_rsa_export( rsa, NULL, NULL,
 271                                          NULL, &T, NULL ) ) != 0 ||
 272              ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
 273             goto end_of_export;
 274         len += ret;
 275
 276         /* Export E */
 277         if ( ( ret = mbedtls_rsa_export( rsa, NULL, NULL,
 278                                          NULL, NULL, &T ) ) != 0 ||
 279              ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
 280             goto end_of_export;
 281         len += ret;
 282
 283         /* Export N */
 284         if ( ( ret = mbedtls_rsa_export( rsa, &T, NULL,
 285                                          NULL, NULL, NULL ) ) != 0 ||
 286              ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
 287             goto end_of_export;
 288         len += ret;
 289
 290     end_of_export:
 291
 292         mbedtls_mpi_free( &T );
 293         if( ret < 0 )
 294             return( ret );
 295
 296         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_int( &c, buf, 0 ) );
 297         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
 298         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c,
 299                                                buf, MBEDTLS_ASN1_CONSTRUCTED |
 300                                                MBEDTLS_ASN1_SEQUENCE ) );
 301     }
 302     else
 303 #endif /* MBEDTLS_RSA_C */
 304 #if defined(MBEDTLS_ECP_C)
 305     if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_ECKEY )
 306     {
 307         mbedtls_ecp_keypair *ec = mbedtls_pk_ec( *key );
 308         size_t pub_len = 0, par_len = 0;
 309
 310         /*
 311          * RFC 5915, or SEC1 Appendix C.4
 312          *
 313          * ECPrivateKey ::= SEQUENCE {
 314          *      version        INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
 315          *      privateKey     OCTET STRING,
 316          *      parameters [0] ECParameters {{ NamedCurve }} OPTIONAL,
 317          *      publicKey  [1] BIT STRING OPTIONAL
 318          *    }
 319          */
 320
 321         /* publicKey */
 322         MBEDTLS_ASN1_CHK_ADD( pub_len, pk_write_ec_pubkey( &c, buf, ec ) );
 323
 324         if( c - buf < 1 )
 325             return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
 326         *--c = 0;
 327         pub_len += 1;
 328
 329         MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_asn1_write_len( &c, buf, pub_len ) );
 330         MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_BIT_STRING ) );
 331
 332         MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_asn1_write_len( &c, buf, pub_len ) );
 333         MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_asn1_write_tag( &c, buf,
 334                             MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 1 ) );
 335         len += pub_len;
 336
 337         /* parameters */
 338         MBEDTLS_ASN1_CHK_ADD( par_len, pk_write_ec_param( &c, buf, ec ) );
 339
 340         MBEDTLS_ASN1_CHK_ADD( par_len, mbedtls_asn1_write_len( &c, buf, par_len ) );
 341         MBEDTLS_ASN1_CHK_ADD( par_len, mbedtls_asn1_write_tag( &c, buf,
 342                             MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 0 ) );
 343         len += par_len;
 344
 345         /* privateKey: write as MPI then fix tag */
 346         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &c, buf, &ec->d ) );
 347         *c = MBEDTLS_ASN1_OCTET_STRING;
 348
 349         /* version */
 350         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_int( &c, buf, 1 ) );
 351
 352         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
 353         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_CONSTRUCTED |
 354                                                     MBEDTLS_ASN1_SEQUENCE ) );
 355     }
 356     else
 357 #endif /* MBEDTLS_ECP_C */
 358         return( MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE );
 359
 360     return( (int) len );
 361 }
 362
 363 #if defined(MBEDTLS_PEM_WRITE_C)
 364
 365 #define PEM_BEGIN_PUBLIC_KEY    "-----BEGIN PUBLIC KEY-----\n"
 366 #define PEM_END_PUBLIC_KEY      "-----END PUBLIC KEY-----\n"
 367
 368 #define PEM_BEGIN_PRIVATE_KEY_RSA   "-----BEGIN RSA PRIVATE KEY-----\n"
 369 #define PEM_END_PRIVATE_KEY_RSA     "-----END RSA PRIVATE KEY-----\n"
 370 #define PEM_BEGIN_PRIVATE_KEY_EC    "-----BEGIN EC PRIVATE KEY-----\n"
 371 #define PEM_END_PRIVATE_KEY_EC      "-----END EC PRIVATE KEY-----\n"
 372
 373 /*
 374  * Max sizes of key per types. Shown as tag + len (+ content).
 375  */
 376
 377 #if defined(MBEDTLS_RSA_C)
 378 /*
 379  * RSA public keys:
 380  *  SubjectPublicKeyInfo  ::=  SEQUENCE  {          1 + 3
 381  *       algorithm            AlgorithmIdentifier,  1 + 1 (sequence)
 382  *                                                + 1 + 1 + 9 (rsa oid)
 383  *                                                + 1 + 1 (params null)
 384  *       subjectPublicKey     BIT STRING }          1 + 3 + (1 + below)
 385  *  RSAPublicKey ::= SEQUENCE {                     1 + 3
 386  *      modulus           INTEGER,  -- n            1 + 3 + MPI_MAX + 1
 387  *      publicExponent    INTEGER   -- e            1 + 3 + MPI_MAX + 1
 388  *  }
 389  */
 390 #define RSA_PUB_DER_MAX_BYTES   38 + 2 * MBEDTLS_MPI_MAX_SIZE
 391
 392 /*
 393  * RSA private keys:
 394  *  RSAPrivateKey ::= SEQUENCE {                    1 + 3
 395  *      version           Version,                  1 + 1 + 1
 396  *      modulus           INTEGER,                  1 + 3 + MPI_MAX + 1
 397  *      publicExponent    INTEGER,                  1 + 3 + MPI_MAX + 1
 398  *      privateExponent   INTEGER,                  1 + 3 + MPI_MAX + 1
 399  *      prime1            INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
 400  *      prime2            INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
 401  *      exponent1         INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
 402  *      exponent2         INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
 403  *      coefficient       INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
 404  *      otherPrimeInfos   OtherPrimeInfos OPTIONAL  0 (not supported)
 405  *  }
 406  */
 407 #define MPI_MAX_SIZE_2          MBEDTLS_MPI_MAX_SIZE / 2 + \
 408                                 MBEDTLS_MPI_MAX_SIZE % 2
 409 #define RSA_PRV_DER_MAX_BYTES   47 + 3 * MBEDTLS_MPI_MAX_SIZE \
 410                                    + 5 * MPI_MAX_SIZE_2
 411
 412 #else /* MBEDTLS_RSA_C */
 413
 414 #define RSA_PUB_DER_MAX_BYTES   0
 415 #define RSA_PRV_DER_MAX_BYTES   0
 416
 417 #endif /* MBEDTLS_RSA_C */
 418
 419 #if defined(MBEDTLS_ECP_C)
 420 /*
 421  * EC public keys:
 422  *  SubjectPublicKeyInfo  ::=  SEQUENCE  {      1 + 2
 423  *    algorithm         AlgorithmIdentifier,    1 + 1 (sequence)
 424  *                                            + 1 + 1 + 7 (ec oid)
 425  *                                            + 1 + 1 + 9 (namedCurve oid)
 426  *    subjectPublicKey  BIT STRING              1 + 2 + 1               [1]
 427  *                                            + 1 (point format)        [1]
 428  *                                            + 2 * ECP_MAX (coords)    [1]
 429  *  }
 430  */
 431 #define ECP_PUB_DER_MAX_BYTES   30 + 2 * MBEDTLS_ECP_MAX_BYTES
 432
 433 /*
 434  * EC private keys:
 435  * ECPrivateKey ::= SEQUENCE {                  1 + 2
 436  *      version        INTEGER ,                1 + 1 + 1
 437  *      privateKey     OCTET STRING,            1 + 1 + ECP_MAX
 438  *      parameters [0] ECParameters OPTIONAL,   1 + 1 + (1 + 1 + 9)
 439  *      publicKey  [1] BIT STRING OPTIONAL      1 + 2 + [1] above
 440  *    }
 441  */
 442 #define ECP_PRV_DER_MAX_BYTES   29 + 3 * MBEDTLS_ECP_MAX_BYTES
 443
 444 #else /* MBEDTLS_ECP_C */
 445
 446 #define ECP_PUB_DER_MAX_BYTES   0
 447 #define ECP_PRV_DER_MAX_BYTES   0
 448
 449 #endif /* MBEDTLS_ECP_C */
 450
 451 #define PUB_DER_MAX_BYTES   RSA_PUB_DER_MAX_BYTES > ECP_PUB_DER_MAX_BYTES ? \
 452                             RSA_PUB_DER_MAX_BYTES : ECP_PUB_DER_MAX_BYTES
 453 #define PRV_DER_MAX_BYTES   RSA_PRV_DER_MAX_BYTES > ECP_PRV_DER_MAX_BYTES ? \
 454                             RSA_PRV_DER_MAX_BYTES : ECP_PRV_DER_MAX_BYTES
 455
 456 int mbedtls_pk_write_pubkey_pem( mbedtls_pk_context *key, unsigned char *buf, size_t size )
 457 {
 458     int ret;
 459     unsigned char output_buf[PUB_DER_MAX_BYTES];
 460     size_t olen = 0;
 461
 462     if( ( ret = mbedtls_pk_write_pubkey_der( key, output_buf,
 463                                      sizeof(output_buf) ) ) < 0 )
 464     {
 465         return( ret );
 466     }
 467
 468     if( ( ret = mbedtls_pem_write_buffer( PEM_BEGIN_PUBLIC_KEY, PEM_END_PUBLIC_KEY,
 469                                   output_buf + sizeof(output_buf) - ret,
 470                                   ret, buf, size, &olen ) ) != 0 )
 471     {
 472         return( ret );
 473     }
 474
 475     return( 0 );
 476 }
 477
 478 int mbedtls_pk_write_key_pem( mbedtls_pk_context *key, unsigned char *buf, size_t size )
 479 {
 480     int ret;
 481     unsigned char output_buf[PRV_DER_MAX_BYTES];
 482     const char *begin, *end;
 483     size_t olen = 0;
 484
 485     if( ( ret = mbedtls_pk_write_key_der( key, output_buf, sizeof(output_buf) ) ) < 0 )
 486         return( ret );
 487
 488 #if defined(MBEDTLS_RSA_C)
 489     if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_RSA )
 490     {
 491         begin = PEM_BEGIN_PRIVATE_KEY_RSA;
 492         end = PEM_END_PRIVATE_KEY_RSA;
 493     }
 494     else
 495 #endif
 496 #if defined(MBEDTLS_ECP_C)
 497     if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_ECKEY )
 498     {
 499         begin = PEM_BEGIN_PRIVATE_KEY_EC;
 500         end = PEM_END_PRIVATE_KEY_EC;
 501     }
 502     else
 503 #endif
 504         return( MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE );
 505
 506     if( ( ret = mbedtls_pem_write_buffer( begin, end,
 507                                   output_buf + sizeof(output_buf) - ret,
 508                                   ret, buf, size, &olen ) ) != 0 )
 509     {
 510         return( ret );
 511     }
 512
 513     return( 0 );
 514 }
 515 #endif /* MBEDTLS_PEM_WRITE_C */
 516
 517 #endif /* MBEDTLS_PK_WRITE_C */