pkwrite.c

00001 /*
00002  *  Public Key layer for writing key files and structures
00003  *
00004  *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
00005  *  SPDX-License-Identifier: Apache-2.0
00006  *
00007  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
00008  *  not use this file except in compliance with the License.
00009  *  You may obtain a copy of the License at
00010  *
00011  *  http://www.apache.org/licenses/LICENSE-2.0
00012  *
00013  *  Unless required by applicable law or agreed to in writing, software
00014  *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
00015  *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00016  *  See the License for the specific language governing permissions and
00017  *  limitations under the License.
00018  *
00019  *  This file is part of mbed TLS (https://tls.mbed.org)
00020  */
00021 
00022 #if !defined(MBEDTLS_CONFIG_FILE)
00023 #include "mbedtls/config.h"
00024 #else
00025 #include MBEDTLS_CONFIG_FILE
00026 #endif
00027 
00028 #if defined(MBEDTLS_PK_WRITE_C)
00029 
00030 #include "mbedtls/pk.h"
00031 #include "mbedtls/asn1write.h"
00032 #include "mbedtls/oid.h"
00033 
00034 #include <string.h>
00035 
00036 #if defined(MBEDTLS_RSA_C)
00037 #include "mbedtls/rsa.h"
00038 #endif
00039 #if defined(MBEDTLS_ECP_C)
00040 #include "mbedtls/ecp.h"
00041 #endif
00042 #if defined(MBEDTLS_ECDSA_C)
00043 #include "mbedtls/ecdsa.h"
00044 #endif
00045 #if defined(MBEDTLS_PEM_WRITE_C)
00046 #include "mbedtls/pem.h"
00047 #endif
00048 
00049 #if defined(MBEDTLS_PLATFORM_C)
00050 #include "mbedtls/platform.h"
00051 #else
00052 #include <stdlib.h>
00053 #define mbedtls_calloc    calloc
00054 #define mbedtls_free       free
00055 #endif
00056 
00057 #if defined(MBEDTLS_RSA_C)
00058 /*
00059  *  RSAPublicKey ::= SEQUENCE {
00060  *      modulus           INTEGER,  -- n
00061  *      publicExponent    INTEGER   -- e
00062  *  }
00063  */
00064 static int pk_write_rsa_pubkey( unsigned char **p, unsigned char *start,
00065                                 mbedtls_rsa_context *rsa )
00066 {
00067     int ret;
00068     size_t len = 0;
00069     mbedtls_mpi T;
00070 
00071     mbedtls_mpi_init( &T );
00072 
00073     /* Export E */
00074     if ( ( ret = mbedtls_rsa_export( rsa, NULL, NULL, NULL, NULL, &T ) ) != 0 ||
00075          ( ret = mbedtls_asn1_write_mpi( p, start, &T ) ) < 0 )
00076         goto end_of_export;
00077     len += ret;
00078 
00079     /* Export N */
00080     if ( ( ret = mbedtls_rsa_export( rsa, &T, NULL, NULL, NULL, NULL ) ) != 0 ||
00081          ( ret = mbedtls_asn1_write_mpi( p, start, &T ) ) < 0 )
00082         goto end_of_export;
00083     len += ret;
00084 
00085 end_of_export:
00086 
00087     mbedtls_mpi_free( &T );
00088     if( ret < 0 )
00089         return( ret );
00090 
00091     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
00092     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_CONSTRUCTED |
00093                                                  MBEDTLS_ASN1_SEQUENCE ) );
00094 
00095     return( (int) len );
00096 }
00097 #endif /* MBEDTLS_RSA_C */
00098 
00099 #if defined(MBEDTLS_ECP_C)
00100 /*
00101  * EC public key is an EC point
00102  */
00103 static int pk_write_ec_pubkey( unsigned char **p, unsigned char *start,
00104                                mbedtls_ecp_keypair *ec )
00105 {
00106     int ret;
00107     size_t len = 0;
00108     unsigned char buf[MBEDTLS_ECP_MAX_PT_LEN];
00109 
00110     if( ( ret = mbedtls_ecp_point_write_binary( &ec->grp , &ec->Q ,
00111                                         MBEDTLS_ECP_PF_UNCOMPRESSED,
00112                                         &len, buf, sizeof( buf ) ) ) != 0 )
00113     {
00114         return( ret );
00115     }
00116 
00117     if( *p < start || (size_t)( *p - start ) < len )
00118         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00119 
00120     *p -= len;
00121     memcpy( *p, buf, len );
00122 
00123     return( (int) len );
00124 }
00125 
00126 /*
00127  * ECParameters ::= CHOICE {
00128  *   namedCurve         OBJECT IDENTIFIER
00129  * }
00130  */
00131 static int pk_write_ec_param( unsigned char **p, unsigned char *start,
00132                               mbedtls_ecp_keypair *ec )
00133 {
00134     int ret;
00135     size_t len = 0;
00136     const char *oid;
00137     size_t oid_len;
00138 
00139     if( ( ret = mbedtls_oid_get_oid_by_ec_grp( ec->grp .id , &oid, &oid_len ) ) != 0 )
00140         return( ret );
00141 
00142     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_oid( p, start, oid, oid_len ) );
00143 
00144     return( (int) len );
00145 }
00146 #endif /* MBEDTLS_ECP_C */
00147 
00148 int mbedtls_pk_write_pubkey( unsigned char **p, unsigned char *start,
00149                              const mbedtls_pk_context *key )
00150 {
00151     int ret;
00152     size_t len = 0;
00153 
00154 #if defined(MBEDTLS_RSA_C)
00155     if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_RSA )
00156         MBEDTLS_ASN1_CHK_ADD( len, pk_write_rsa_pubkey( p, start, mbedtls_pk_rsa( *key ) ) );
00157     else
00158 #endif
00159 #if defined(MBEDTLS_ECP_C)
00160     if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_ECKEY )
00161         MBEDTLS_ASN1_CHK_ADD( len, pk_write_ec_pubkey( p, start, mbedtls_pk_ec( *key ) ) );
00162     else
00163 #endif
00164         return( MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE );
00165 
00166     return( (int) len );
00167 }
00168 
00169 int mbedtls_pk_write_pubkey_der( mbedtls_pk_context *key, unsigned char *buf, size_t size )
00170 {
00171     int ret;
00172     unsigned char *c;
00173     size_t len = 0, par_len = 0, oid_len;
00174     const char *oid;
00175 
00176     c = buf + size;
00177 
00178     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_pk_write_pubkey( &c, buf, key ) );
00179 
00180     if( c - buf < 1 )
00181         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00182 
00183     /*
00184      *  SubjectPublicKeyInfo  ::=  SEQUENCE  {
00185      *       algorithm            AlgorithmIdentifier,
00186      *       subjectPublicKey     BIT STRING }
00187      */
00188     *--c = 0;
00189     len += 1;
00190 
00191     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
00192     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_BIT_STRING ) );
00193 
00194     if( ( ret = mbedtls_oid_get_oid_by_pk_alg( mbedtls_pk_get_type( key ),
00195                                        &oid, &oid_len ) ) != 0 )
00196     {
00197         return( ret );
00198     }
00199 
00200 #if defined(MBEDTLS_ECP_C)
00201     if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_ECKEY )
00202     {
00203         MBEDTLS_ASN1_CHK_ADD( par_len, pk_write_ec_param( &c, buf, mbedtls_pk_ec( *key ) ) );
00204     }
00205 #endif
00206 
00207     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_algorithm_identifier( &c, buf, oid, oid_len,
00208                                                         par_len ) );
00209 
00210     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
00211     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_CONSTRUCTED |
00212                                                 MBEDTLS_ASN1_SEQUENCE ) );
00213 
00214     return( (int) len );
00215 }
00216 
00217 int mbedtls_pk_write_key_der( mbedtls_pk_context *key, unsigned char *buf, size_t size )
00218 {
00219     int ret;
00220     unsigned char *c = buf + size;
00221     size_t len = 0;
00222 
00223 #if defined(MBEDTLS_RSA_C)
00224     if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_RSA )
00225     {
00226         mbedtls_mpi T; /* Temporary holding the exported parameters */
00227         mbedtls_rsa_context *rsa = mbedtls_pk_rsa( *key );
00228 
00229         /*
00230          * Export the parameters one after another to avoid simultaneous copies.
00231          */
00232 
00233         mbedtls_mpi_init( &T );
00234 
00235         /* Export QP */
00236         if( ( ret = mbedtls_rsa_export_crt( rsa, NULL, NULL, &T ) ) != 0 ||
00237             ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
00238             goto end_of_export;
00239         len += ret;
00240 
00241         /* Export DQ */
00242         if( ( ret = mbedtls_rsa_export_crt( rsa, NULL, &T, NULL ) ) != 0 ||
00243             ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
00244             goto end_of_export;
00245         len += ret;
00246 
00247         /* Export DP */
00248         if( ( ret = mbedtls_rsa_export_crt( rsa, &T, NULL, NULL ) ) != 0 ||
00249             ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
00250             goto end_of_export;
00251         len += ret;
00252 
00253         /* Export Q */
00254         if ( ( ret = mbedtls_rsa_export( rsa, NULL, NULL,
00255                                          &T, NULL, NULL ) ) != 0 ||
00256              ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
00257             goto end_of_export;
00258         len += ret;
00259 
00260         /* Export P */
00261         if ( ( ret = mbedtls_rsa_export( rsa, NULL, &T,
00262                                          NULL, NULL, NULL ) ) != 0 ||
00263              ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
00264             goto end_of_export;
00265         len += ret;
00266 
00267         /* Export D */
00268         if ( ( ret = mbedtls_rsa_export( rsa, NULL, NULL,
00269                                          NULL, &T, NULL ) ) != 0 ||
00270              ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
00271             goto end_of_export;
00272         len += ret;
00273 
00274         /* Export E */
00275         if ( ( ret = mbedtls_rsa_export( rsa, NULL, NULL,
00276                                          NULL, NULL, &T ) ) != 0 ||
00277              ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
00278             goto end_of_export;
00279         len += ret;
00280 
00281         /* Export N */
00282         if ( ( ret = mbedtls_rsa_export( rsa, &T, NULL,
00283                                          NULL, NULL, NULL ) ) != 0 ||
00284              ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
00285             goto end_of_export;
00286         len += ret;
00287 
00288     end_of_export:
00289 
00290         mbedtls_mpi_free( &T );
00291         if( ret < 0 )
00292             return( ret );
00293 
00294         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_int( &c, buf, 0 ) );
00295         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
00296         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c,
00297                                                buf, MBEDTLS_ASN1_CONSTRUCTED |
00298                                                MBEDTLS_ASN1_SEQUENCE ) );
00299     }
00300     else
00301 #endif /* MBEDTLS_RSA_C */
00302 #if defined(MBEDTLS_ECP_C)
00303     if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_ECKEY )
00304     {
00305         mbedtls_ecp_keypair *ec = mbedtls_pk_ec( *key );
00306         size_t pub_len = 0, par_len = 0;
00307 
00308         /*
00309          * RFC 5915, or SEC1 Appendix C.4
00310          *
00311          * ECPrivateKey ::= SEQUENCE {
00312          *      version        INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
00313          *      privateKey     OCTET STRING,
00314          *      parameters [0] ECParameters {{ NamedCurve }} OPTIONAL,
00315          *      publicKey  [1] BIT STRING OPTIONAL
00316          *    }
00317          */
00318 
00319         /* publicKey */
00320         MBEDTLS_ASN1_CHK_ADD( pub_len, pk_write_ec_pubkey( &c, buf, ec ) );
00321 
00322         if( c - buf < 1 )
00323             return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
00324         *--c = 0;
00325         pub_len += 1;
00326 
00327         MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_asn1_write_len( &c, buf, pub_len ) );
00328         MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_BIT_STRING ) );
00329 
00330         MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_asn1_write_len( &c, buf, pub_len ) );
00331         MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_asn1_write_tag( &c, buf,
00332                             MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 1 ) );
00333         len += pub_len;
00334 
00335         /* parameters */
00336         MBEDTLS_ASN1_CHK_ADD( par_len, pk_write_ec_param( &c, buf, ec ) );
00337 
00338         MBEDTLS_ASN1_CHK_ADD( par_len, mbedtls_asn1_write_len( &c, buf, par_len ) );
00339         MBEDTLS_ASN1_CHK_ADD( par_len, mbedtls_asn1_write_tag( &c, buf,
00340                             MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 0 ) );
00341         len += par_len;
00342 
00343         /* privateKey: write as MPI then fix tag */
00344         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &c, buf, &ec->d  ) );
00345         *c = MBEDTLS_ASN1_OCTET_STRING;
00346 
00347         /* version */
00348         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_int( &c, buf, 1 ) );
00349 
00350         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
00351         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_CONSTRUCTED |
00352                                                     MBEDTLS_ASN1_SEQUENCE ) );
00353     }
00354     else
00355 #endif /* MBEDTLS_ECP_C */
00356         return( MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE );
00357 
00358     return( (int) len );
00359 }
00360 
00361 #if defined(MBEDTLS_PEM_WRITE_C)
00362 
00363 #define PEM_BEGIN_PUBLIC_KEY    "-----BEGIN PUBLIC KEY-----\n"
00364 #define PEM_END_PUBLIC_KEY      "-----END PUBLIC KEY-----\n"
00365 
00366 #define PEM_BEGIN_PRIVATE_KEY_RSA   "-----BEGIN RSA PRIVATE KEY-----\n"
00367 #define PEM_END_PRIVATE_KEY_RSA     "-----END RSA PRIVATE KEY-----\n"
00368 #define PEM_BEGIN_PRIVATE_KEY_EC    "-----BEGIN EC PRIVATE KEY-----\n"
00369 #define PEM_END_PRIVATE_KEY_EC      "-----END EC PRIVATE KEY-----\n"
00370 
00371 /*
00372  * Max sizes of key per types. Shown as tag + len (+ content).
00373  */
00374 
00375 #if defined(MBEDTLS_RSA_C)
00376 /*
00377  * RSA public keys:
00378  *  SubjectPublicKeyInfo  ::=  SEQUENCE  {          1 + 3
00379  *       algorithm            AlgorithmIdentifier,  1 + 1 (sequence)
00380  *                                                + 1 + 1 + 9 (rsa oid)
00381  *                                                + 1 + 1 (params null)
00382  *       subjectPublicKey     BIT STRING }          1 + 3 + (1 + below)
00383  *  RSAPublicKey ::= SEQUENCE {                     1 + 3
00384  *      modulus           INTEGER,  -- n            1 + 3 + MPI_MAX + 1
00385  *      publicExponent    INTEGER   -- e            1 + 3 + MPI_MAX + 1
00386  *  }
00387  */
00388 #define RSA_PUB_DER_MAX_BYTES   38 + 2 * MBEDTLS_MPI_MAX_SIZE
00389 
00390 /*
00391  * RSA private keys:
00392  *  RSAPrivateKey ::= SEQUENCE {                    1 + 3
00393  *      version           Version,                  1 + 1 + 1
00394  *      modulus           INTEGER,                  1 + 3 + MPI_MAX + 1
00395  *      publicExponent    INTEGER,                  1 + 3 + MPI_MAX + 1
00396  *      privateExponent   INTEGER,                  1 + 3 + MPI_MAX + 1
00397  *      prime1            INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
00398  *      prime2            INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
00399  *      exponent1         INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
00400  *      exponent2         INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
00401  *      coefficient       INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
00402  *      otherPrimeInfos   OtherPrimeInfos OPTIONAL  0 (not supported)
00403  *  }
00404  */
00405 #define MPI_MAX_SIZE_2          MBEDTLS_MPI_MAX_SIZE / 2 + \
00406                                 MBEDTLS_MPI_MAX_SIZE % 2
00407 #define RSA_PRV_DER_MAX_BYTES   47 + 3 * MBEDTLS_MPI_MAX_SIZE \
00408                                    + 5 * MPI_MAX_SIZE_2
00409 
00410 #else /* MBEDTLS_RSA_C */
00411 
00412 #define RSA_PUB_DER_MAX_BYTES   0
00413 #define RSA_PRV_DER_MAX_BYTES   0
00414 
00415 #endif /* MBEDTLS_RSA_C */
00416 
00417 #if defined(MBEDTLS_ECP_C)
00418 /*
00419  * EC public keys:
00420  *  SubjectPublicKeyInfo  ::=  SEQUENCE  {      1 + 2
00421  *    algorithm         AlgorithmIdentifier,    1 + 1 (sequence)
00422  *                                            + 1 + 1 + 7 (ec oid)
00423  *                                            + 1 + 1 + 9 (namedCurve oid)
00424  *    subjectPublicKey  BIT STRING              1 + 2 + 1               [1]
00425  *                                            + 1 (point format)        [1]
00426  *                                            + 2 * ECP_MAX (coords)    [1]
00427  *  }
00428  */
00429 #define ECP_PUB_DER_MAX_BYTES   30 + 2 * MBEDTLS_ECP_MAX_BYTES
00430 
00431 /*
00432  * EC private keys:
00433  * ECPrivateKey ::= SEQUENCE {                  1 + 2
00434  *      version        INTEGER ,                1 + 1 + 1
00435  *      privateKey     OCTET STRING,            1 + 1 + ECP_MAX
00436  *      parameters [0] ECParameters OPTIONAL,   1 + 1 + (1 + 1 + 9)
00437  *      publicKey  [1] BIT STRING OPTIONAL      1 + 2 + [1] above
00438  *    }
00439  */
00440 #define ECP_PRV_DER_MAX_BYTES   29 + 3 * MBEDTLS_ECP_MAX_BYTES
00441 
00442 #else /* MBEDTLS_ECP_C */
00443 
00444 #define ECP_PUB_DER_MAX_BYTES   0
00445 #define ECP_PRV_DER_MAX_BYTES   0
00446 
00447 #endif /* MBEDTLS_ECP_C */
00448 
00449 #define PUB_DER_MAX_BYTES   RSA_PUB_DER_MAX_BYTES > ECP_PUB_DER_MAX_BYTES ? \
00450                             RSA_PUB_DER_MAX_BYTES : ECP_PUB_DER_MAX_BYTES
00451 #define PRV_DER_MAX_BYTES   RSA_PRV_DER_MAX_BYTES > ECP_PRV_DER_MAX_BYTES ? \
00452                             RSA_PRV_DER_MAX_BYTES : ECP_PRV_DER_MAX_BYTES
00453 
00454 int mbedtls_pk_write_pubkey_pem( mbedtls_pk_context *key, unsigned char *buf, size_t size )
00455 {
00456     int ret;
00457     unsigned char output_buf[PUB_DER_MAX_BYTES];
00458     size_t olen = 0;
00459 
00460     if( ( ret = mbedtls_pk_write_pubkey_der( key, output_buf,
00461                                      sizeof(output_buf) ) ) < 0 )
00462     {
00463         return( ret );
00464     }
00465 
00466     if( ( ret = mbedtls_pem_write_buffer( PEM_BEGIN_PUBLIC_KEY, PEM_END_PUBLIC_KEY,
00467                                   output_buf + sizeof(output_buf) - ret,
00468                                   ret, buf, size, &olen ) ) != 0 )
00469     {
00470         return( ret );
00471     }
00472 
00473     return( 0 );
00474 }
00475 
00476 int mbedtls_pk_write_key_pem( mbedtls_pk_context *key, unsigned char *buf, size_t size )
00477 {
00478     int ret;
00479     unsigned char output_buf[PRV_DER_MAX_BYTES];
00480     const char *begin, *end;
00481     size_t olen = 0;
00482 
00483     if( ( ret = mbedtls_pk_write_key_der( key, output_buf, sizeof(output_buf) ) ) < 0 )
00484         return( ret );
00485 
00486 #if defined(MBEDTLS_RSA_C)
00487     if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_RSA )
00488     {
00489         begin = PEM_BEGIN_PRIVATE_KEY_RSA;
00490         end = PEM_END_PRIVATE_KEY_RSA;
00491     }
00492     else
00493 #endif
00494 #if defined(MBEDTLS_ECP_C)
00495     if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_ECKEY )
00496     {
00497         begin = PEM_BEGIN_PRIVATE_KEY_EC;
00498         end = PEM_END_PRIVATE_KEY_EC;
00499     }
00500     else
00501 #endif
00502         return( MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE );
00503 
00504     if( ( ret = mbedtls_pem_write_buffer( begin, end,
00505                                   output_buf + sizeof(output_buf) - ret,
00506                                   ret, buf, size, &olen ) ) != 0 )
00507     {
00508         return( ret );
00509     }
00510 
00511     return( 0 );
00512 }
00513 #endif /* MBEDTLS_PEM_WRITE_C */
00514 
00515 #endif /* MBEDTLS_PK_WRITE_C */