library/x509write_crt.c - mirror/mbed-tls.git - TrustedFirmware Git Browser

 /*
  *  X.509 certificate writing
  *
  *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
  *  SPDX-License-Identifier: Apache-2.0
  *
  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
  *  not use this file except in compliance with the License.
  *  You may obtain a copy of the License at
  *
  *  http://www.apache.org/licenses/LICENSE-2.0
  *
  *  Unless required by applicable law or agreed to in writing, software
  *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  *  See the License for the specific language governing permissions and
  *  limitations under the License.
  *
  *  This file is part of mbed TLS (https://tls.mbed.org)
  */
 /*
  * References:
  * - certificates: RFC 5280, updated by RFC 6818
  * - CSRs: PKCS#10 v1.7 aka RFC 2986
  * - attributes: PKCS#9 v2.0 aka RFC 2985
  */

 #if !defined(MBEDTLS_CONFIG_FILE)
 #include "mbedtls/config.h"
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif

 #if defined(MBEDTLS_X509_CRT_WRITE_C)

 #include "mbedtls/x509_crt.h"
 #include "mbedtls/oid.h"
 #include "mbedtls/asn1write.h"
 #include "mbedtls/sha1.h"
 #include "mbedtls/platform_util.h"

 #include <string.h>

 #if defined(MBEDTLS_PEM_WRITE_C)
 #include "mbedtls/pem.h"
 #endif /* MBEDTLS_PEM_WRITE_C */

 void mbedtls_x509write_crt_init( mbedtls_x509write_cert *ctx )
 {
     memset( ctx, 0, sizeof( mbedtls_x509write_cert ) );

     mbedtls_mpi_init( &ctx->serial );
     ctx->version = MBEDTLS_X509_CRT_VERSION_3;
 }

 void mbedtls_x509write_crt_free( mbedtls_x509write_cert *ctx )
 {
     mbedtls_mpi_free( &ctx->serial );

     mbedtls_asn1_free_named_data_list( &ctx->subject );
     mbedtls_asn1_free_named_data_list( &ctx->issuer );
     mbedtls_asn1_free_named_data_list( &ctx->extensions );

     mbedtls_platform_zeroize( ctx, sizeof( mbedtls_x509write_cert ) );
 }

 void mbedtls_x509write_crt_set_version( mbedtls_x509write_cert *ctx, int version )
 {
     ctx->version = version;
 }

 void mbedtls_x509write_crt_set_md_alg( mbedtls_x509write_cert *ctx, mbedtls_md_type_t md_alg )
 {
     ctx->md_alg = md_alg;
 }

 void mbedtls_x509write_crt_set_subject_key( mbedtls_x509write_cert *ctx, mbedtls_pk_context *key )
 {
     ctx->subject_key = key;
 }

 void mbedtls_x509write_crt_set_issuer_key( mbedtls_x509write_cert *ctx, mbedtls_pk_context *key )
 {
     ctx->issuer_key = key;
 }

 int mbedtls_x509write_crt_set_subject_name( mbedtls_x509write_cert *ctx,
                                     const char *subject_name )
 {
     return mbedtls_x509_string_to_names( &ctx->subject, subject_name );
 }

 int mbedtls_x509write_crt_set_issuer_name( mbedtls_x509write_cert *ctx,
                                    const char *issuer_name )
 {
     return mbedtls_x509_string_to_names( &ctx->issuer, issuer_name );
 }

 int mbedtls_x509write_crt_set_serial( mbedtls_x509write_cert *ctx, const mbedtls_mpi *serial )
 {
     int ret;

     if( ( ret = mbedtls_mpi_copy( &ctx->serial, serial ) ) != 0 )
         return( ret );

     return( 0 );
 }

 int mbedtls_x509write_crt_set_validity( mbedtls_x509write_cert *ctx, const char *not_before,
                                 const char *not_after )
 {
     if( strlen( not_before ) != MBEDTLS_X509_RFC5280_UTC_TIME_LEN - 1 ||
         strlen( not_after )  != MBEDTLS_X509_RFC5280_UTC_TIME_LEN - 1 )
     {
         return( MBEDTLS_ERR_X509_BAD_INPUT_DATA );
     }
     strncpy( ctx->not_before, not_before, MBEDTLS_X509_RFC5280_UTC_TIME_LEN );
     strncpy( ctx->not_after , not_after , MBEDTLS_X509_RFC5280_UTC_TIME_LEN );
     ctx->not_before[MBEDTLS_X509_RFC5280_UTC_TIME_LEN - 1] = 'Z';
     ctx->not_after[MBEDTLS_X509_RFC5280_UTC_TIME_LEN - 1] = 'Z';

     return( 0 );
 }

 int mbedtls_x509write_crt_set_extension( mbedtls_x509write_cert *ctx,
                                  const char *oid, size_t oid_len,
                                  int critical,
                                  const unsigned char *val, size_t val_len )
 {
     return mbedtls_x509_set_extension( &ctx->extensions, oid, oid_len,
                                critical, val, val_len );
 }

 int mbedtls_x509write_crt_set_basic_constraints( mbedtls_x509write_cert *ctx,
                                          int is_ca, int max_pathlen )
 {
     int ret;
     unsigned char buf[9];
     unsigned char *c = buf + sizeof(buf);
     size_t len = 0;

     memset( buf, 0, sizeof(buf) );

     if( is_ca && max_pathlen > 127 )
         return( MBEDTLS_ERR_X509_BAD_INPUT_DATA );

     if( is_ca )
     {
         if( max_pathlen >= 0 )
         {
             MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_int( &c, buf, max_pathlen ) );
         }
         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_bool( &c, buf, 1 ) );
     }

     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_CONSTRUCTED |
                                                 MBEDTLS_ASN1_SEQUENCE ) );

     return mbedtls_x509write_crt_set_extension( ctx, MBEDTLS_OID_BASIC_CONSTRAINTS,
                                         MBEDTLS_OID_SIZE( MBEDTLS_OID_BASIC_CONSTRAINTS ),
                                         0, buf + sizeof(buf) - len, len );
 }

 #if defined(MBEDTLS_SHA1_C)
 int mbedtls_x509write_crt_set_subject_key_identifier( mbedtls_x509write_cert *ctx )
 {
     int ret;
     unsigned char buf[MBEDTLS_MPI_MAX_SIZE * 2 + 20]; /* tag, length + 2xMPI */
     unsigned char *c = buf + sizeof(buf);
     size_t len = 0;

     memset( buf, 0, sizeof(buf) );
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_pk_write_pubkey( &c, buf, ctx->subject_key ) );

     ret = mbedtls_sha1_ret( buf + sizeof( buf ) - len, len,
                             buf + sizeof( buf ) - 20 );
     if( ret != 0 )
         return( ret );
     c = buf + sizeof( buf ) - 20;
     len = 20;

     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_OCTET_STRING ) );

     return mbedtls_x509write_crt_set_extension( ctx, MBEDTLS_OID_SUBJECT_KEY_IDENTIFIER,
                                         MBEDTLS_OID_SIZE( MBEDTLS_OID_SUBJECT_KEY_IDENTIFIER ),
                                         0, buf + sizeof(buf) - len, len );
 }

 int mbedtls_x509write_crt_set_authority_key_identifier( mbedtls_x509write_cert *ctx )
 {
     int ret;
     unsigned char buf[MBEDTLS_MPI_MAX_SIZE * 2 + 20]; /* tag, length + 2xMPI */
     unsigned char *c = buf + sizeof( buf );
     size_t len = 0;

     memset( buf, 0, sizeof(buf) );
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_pk_write_pubkey( &c, buf, ctx->issuer_key ) );

     ret = mbedtls_sha1_ret( buf + sizeof( buf ) - len, len,
                             buf + sizeof( buf ) - 20 );
     if( ret != 0 )
         return( ret );
     c = buf + sizeof( buf ) - 20;
     len = 20;

     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_CONTEXT_SPECIFIC | 0 ) );

     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_CONSTRUCTED |
                                                 MBEDTLS_ASN1_SEQUENCE ) );

     return mbedtls_x509write_crt_set_extension( ctx, MBEDTLS_OID_AUTHORITY_KEY_IDENTIFIER,
                                    MBEDTLS_OID_SIZE( MBEDTLS_OID_AUTHORITY_KEY_IDENTIFIER ),
                                    0, buf + sizeof( buf ) - len, len );
 }
 #endif /* MBEDTLS_SHA1_C */

 static size_t crt_get_unused_bits_for_named_bitstring( unsigned char bitstring,
                                                        size_t bit_offset )
 {
     size_t unused_bits;

      /* Count the unused bits removing trailing 0s */
     for( unused_bits = bit_offset; unused_bits < 8; unused_bits++ )
         if( ( ( bitstring >> unused_bits ) & 0x1 ) != 0 )
             break;

      return( unused_bits );
 }

 int mbedtls_x509write_crt_set_key_usage( mbedtls_x509write_cert *ctx,
                                          unsigned int key_usage )
 {
     unsigned char buf[4], ku;
     unsigned char *c;
     int ret;
     size_t unused_bits;
     const unsigned int allowed_bits = MBEDTLS_X509_KU_DIGITAL_SIGNATURE |
         MBEDTLS_X509_KU_NON_REPUDIATION   |
         MBEDTLS_X509_KU_KEY_ENCIPHERMENT  |
         MBEDTLS_X509_KU_DATA_ENCIPHERMENT |
         MBEDTLS_X509_KU_KEY_AGREEMENT     |
         MBEDTLS_X509_KU_KEY_CERT_SIGN     |
         MBEDTLS_X509_KU_CRL_SIGN;

     /* Check that nothing other than the allowed flags is set */
     if( ( key_usage & ~allowed_bits ) != 0 )
         return( MBEDTLS_ERR_X509_FEATURE_UNAVAILABLE );

     c = buf + 4;
     ku = (unsigned char)key_usage;
     unused_bits = crt_get_unused_bits_for_named_bitstring( ku, 1 );
     ret = mbedtls_asn1_write_bitstring( &c, buf, &ku, 8 - unused_bits );

     if( ret < 0 )
         return( ret );
     else if( ret < 3 || ret > 4 )
         return( MBEDTLS_ERR_X509_INVALID_FORMAT );

     ret = mbedtls_x509write_crt_set_extension( ctx, MBEDTLS_OID_KEY_USAGE,
                                        MBEDTLS_OID_SIZE( MBEDTLS_OID_KEY_USAGE ),
                                        1, c, (size_t)ret );
     if( ret != 0 )
         return( ret );

     return( 0 );
 }

 int mbedtls_x509write_crt_set_ns_cert_type( mbedtls_x509write_cert *ctx,
                                     unsigned char ns_cert_type )
 {
     unsigned char buf[4];
     unsigned char *c;
     size_t unused_bits;
     int ret;

     c = buf + 4;

     unused_bits = crt_get_unused_bits_for_named_bitstring( ns_cert_type, 0 );
     ret = mbedtls_asn1_write_bitstring( &c,
                                         buf,
                                         &ns_cert_type,
                                         8 - unused_bits );
     if( ret < 3 || ret > 4 )
         return( ret );

     ret = mbedtls_x509write_crt_set_extension( ctx, MBEDTLS_OID_NS_CERT_TYPE,
                                        MBEDTLS_OID_SIZE( MBEDTLS_OID_NS_CERT_TYPE ),
                                        0, c, (size_t)ret );
     if( ret != 0 )
         return( ret );

     return( 0 );
 }

 static int x509_write_time( unsigned char **p, unsigned char *start,
                             const char *t, size_t size )
 {
     int ret;
     size_t len = 0;

     /*
      * write MBEDTLS_ASN1_UTC_TIME if year < 2050 (2 bytes shorter)
      */
     if( t[0] == '2' && t[1] == '0' && t[2] < '5' )
     {
         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
                                              (const unsigned char *) t + 2,
                                              size - 2 ) );
         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_UTC_TIME ) );
     }
     else
     {
         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
                                                   (const unsigned char *) t,
                                                   size ) );
         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_GENERALIZED_TIME ) );
     }

     return( (int) len );
 }

 int mbedtls_x509write_crt_der( mbedtls_x509write_cert *ctx, unsigned char *buf, size_t size,
                        int (*f_rng)(void *, unsigned char *, size_t),
                        void *p_rng )
 {
     int ret;
     const char *sig_oid;
     size_t sig_oid_len = 0;
     unsigned char *c, *c2;
     unsigned char hash[64];
     unsigned char sig[MBEDTLS_MPI_MAX_SIZE];
     unsigned char tmp_buf[2048];
     size_t sub_len = 0, pub_len = 0, sig_and_oid_len = 0, sig_len;
     size_t len = 0;
     mbedtls_pk_type_t pk_alg;

     /*
      * Prepare data to be signed in tmp_buf
      */
     c = tmp_buf + sizeof( tmp_buf );

     /* Signature algorithm needed in TBS, and later for actual signature */

     /* There's no direct way of extracting a signature algorithm
      * (represented as an element of mbedtls_pk_type_t) from a PK instance. */
     if( mbedtls_pk_can_do( ctx->issuer_key, MBEDTLS_PK_RSA ) )
         pk_alg = MBEDTLS_PK_RSA;
     else if( mbedtls_pk_can_do( ctx->issuer_key, MBEDTLS_PK_ECDSA ) )
         pk_alg = MBEDTLS_PK_ECDSA;
     else
         return( MBEDTLS_ERR_X509_INVALID_ALG );

     if( ( ret = mbedtls_oid_get_oid_by_sig_alg( pk_alg, ctx->md_alg,
                                           &sig_oid, &sig_oid_len ) ) != 0 )
     {
         return( ret );
     }

     /*
      *  Extensions  ::=  SEQUENCE SIZE (1..MAX) OF Extension
      */

     /* Only for v3 */
     if( ctx->version == MBEDTLS_X509_CRT_VERSION_3 )
     {
         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_x509_write_extensions( &c, tmp_buf, ctx->extensions ) );
         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, len ) );
         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONSTRUCTED |
                                                            MBEDTLS_ASN1_SEQUENCE ) );
         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, len ) );
         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONTEXT_SPECIFIC |
                                                            MBEDTLS_ASN1_CONSTRUCTED | 3 ) );
     }

     /*
      *  SubjectPublicKeyInfo
      */
     MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_pk_write_pubkey_der( ctx->subject_key,
                                                 tmp_buf, c - tmp_buf ) );
     c -= pub_len;
     len += pub_len;

     /*
      *  Subject  ::=  Name
      */
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_x509_write_names( &c, tmp_buf, ctx->subject ) );

     /*
      *  Validity ::= SEQUENCE {
      *       notBefore      Time,
      *       notAfter       Time }
      */
     sub_len = 0;

     MBEDTLS_ASN1_CHK_ADD( sub_len, x509_write_time( &c, tmp_buf, ctx->not_after,
                                             MBEDTLS_X509_RFC5280_UTC_TIME_LEN ) );

     MBEDTLS_ASN1_CHK_ADD( sub_len, x509_write_time( &c, tmp_buf, ctx->not_before,
                                             MBEDTLS_X509_RFC5280_UTC_TIME_LEN ) );

     len += sub_len;
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, sub_len ) );
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONSTRUCTED |
                                                     MBEDTLS_ASN1_SEQUENCE ) );

     /*
      *  Issuer  ::=  Name
      */
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_x509_write_names( &c, tmp_buf, ctx->issuer ) );

     /*
      *  Signature   ::=  AlgorithmIdentifier
      */
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_algorithm_identifier( &c, tmp_buf,
                        sig_oid, strlen( sig_oid ), 0 ) );

     /*
      *  Serial   ::=  INTEGER
      */
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &c, tmp_buf, &ctx->serial ) );

     /*
      *  Version  ::=  INTEGER  {  v1(0), v2(1), v3(2)  }
      */

     /* Can be omitted for v1 */
     if( ctx->version != MBEDTLS_X509_CRT_VERSION_1 )
     {
         sub_len = 0;
         MBEDTLS_ASN1_CHK_ADD( sub_len, mbedtls_asn1_write_int( &c, tmp_buf, ctx->version ) );
         len += sub_len;
         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, sub_len ) );
         MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONTEXT_SPECIFIC |
                                                            MBEDTLS_ASN1_CONSTRUCTED | 0 ) );
     }

     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, len ) );
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONSTRUCTED |
                                                        MBEDTLS_ASN1_SEQUENCE ) );

     /*
      * Make signature
      */
     if( ( ret = mbedtls_md( mbedtls_md_info_from_type( ctx->md_alg ), c,
                             len, hash ) ) != 0 )
     {
         return( ret );
     }

     if( ( ret = mbedtls_pk_sign( ctx->issuer_key, ctx->md_alg, hash, 0, sig, &sig_len,
                          f_rng, p_rng ) ) != 0 )
     {
         return( ret );
     }

     /*
      * Write data to output buffer
      */
     c2 = buf + size;
     MBEDTLS_ASN1_CHK_ADD( sig_and_oid_len, mbedtls_x509_write_sig( &c2, buf,
                                         sig_oid, sig_oid_len, sig, sig_len ) );

     if( len > (size_t)( c2 - buf ) )
         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );

     c2 -= len;
     memcpy( c2, c, len );

     len += sig_and_oid_len;
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c2, buf, len ) );
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c2, buf, MBEDTLS_ASN1_CONSTRUCTED |
                                                  MBEDTLS_ASN1_SEQUENCE ) );

     return( (int) len );
 }

 #define PEM_BEGIN_CRT           "-----BEGIN CERTIFICATE-----\n"
 #define PEM_END_CRT             "-----END CERTIFICATE-----\n"

 #if defined(MBEDTLS_PEM_WRITE_C)
 int mbedtls_x509write_crt_pem( mbedtls_x509write_cert *crt, unsigned char *buf, size_t size,
                        int (*f_rng)(void *, unsigned char *, size_t),
                        void *p_rng )
 {
     int ret;
     unsigned char output_buf[4096];
     size_t olen = 0;

     if( ( ret = mbedtls_x509write_crt_der( crt, output_buf, sizeof(output_buf),
                                    f_rng, p_rng ) ) < 0 )
     {
         return( ret );
     }

     if( ( ret = mbedtls_pem_write_buffer( PEM_BEGIN_CRT, PEM_END_CRT,
                                   output_buf + sizeof(output_buf) - ret,
                                   ret, buf, size, &olen ) ) != 0 )
     {
         return( ret );
     }

     return( 0 );
 }
 #endif /* MBEDTLS_PEM_WRITE_C */

 #endif /* MBEDTLS_X509_CRT_WRITE_C */
	/*
	* X.509 certificate writing
	*
	* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
	* SPDX-License-Identifier: Apache-2.0
	*
	* Licensed under the Apache License, Version 2.0 (the "License"); you may
	* not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
	* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*
	* This file is part of mbed TLS (https://tls.mbed.org)
	*/
	/*
	* References:
	* - certificates: RFC 5280, updated by RFC 6818
	* - CSRs: PKCS#10 v1.7 aka RFC 2986
	* - attributes: PKCS#9 v2.0 aka RFC 2985
	*/

	#if !defined(MBEDTLS_CONFIG_FILE)
	#include "mbedtls/config.h"
	#else
	#include MBEDTLS_CONFIG_FILE
	#endif

	#if defined(MBEDTLS_X509_CRT_WRITE_C)

	#include "mbedtls/x509_crt.h"
	#include "mbedtls/oid.h"
	#include "mbedtls/asn1write.h"
	#include "mbedtls/sha1.h"
	#include "mbedtls/platform_util.h"

	#include <string.h>

	#if defined(MBEDTLS_PEM_WRITE_C)
	#include "mbedtls/pem.h"
	#endif /* MBEDTLS_PEM_WRITE_C */

	void mbedtls_x509write_crt_init( mbedtls_x509write_cert *ctx )
	{
	memset( ctx, 0, sizeof( mbedtls_x509write_cert ) );

	mbedtls_mpi_init( &ctx->serial );
	ctx->version = MBEDTLS_X509_CRT_VERSION_3;
	}

	void mbedtls_x509write_crt_free( mbedtls_x509write_cert *ctx )
	{
	mbedtls_mpi_free( &ctx->serial );

	mbedtls_asn1_free_named_data_list( &ctx->subject );
	mbedtls_asn1_free_named_data_list( &ctx->issuer );
	mbedtls_asn1_free_named_data_list( &ctx->extensions );

	mbedtls_platform_zeroize( ctx, sizeof( mbedtls_x509write_cert ) );
	}

	void mbedtls_x509write_crt_set_version( mbedtls_x509write_cert *ctx, int version )
	{
	ctx->version = version;
	}

	void mbedtls_x509write_crt_set_md_alg( mbedtls_x509write_cert *ctx, mbedtls_md_type_t md_alg )
	{
	ctx->md_alg = md_alg;
	}

	void mbedtls_x509write_crt_set_subject_key( mbedtls_x509write_cert ctx, mbedtls_pk_context key )
	{
	ctx->subject_key = key;
	}

	void mbedtls_x509write_crt_set_issuer_key( mbedtls_x509write_cert ctx, mbedtls_pk_context key )
	{
	ctx->issuer_key = key;
	}

	int mbedtls_x509write_crt_set_subject_name( mbedtls_x509write_cert *ctx,
	const char *subject_name )
	{
	return mbedtls_x509_string_to_names( &ctx->subject, subject_name );
	}

	int mbedtls_x509write_crt_set_issuer_name( mbedtls_x509write_cert *ctx,
	const char *issuer_name )
	{
	return mbedtls_x509_string_to_names( &ctx->issuer, issuer_name );
	}

	int mbedtls_x509write_crt_set_serial( mbedtls_x509write_cert ctx, const mbedtls_mpi serial )
	{
	int ret;

	if( ( ret = mbedtls_mpi_copy( &ctx->serial, serial ) ) != 0 )
	return( ret );

	return( 0 );
	}

	int mbedtls_x509write_crt_set_validity( mbedtls_x509write_cert ctx, const char not_before,
	const char *not_after )
	{
	if( strlen( not_before ) != MBEDTLS_X509_RFC5280_UTC_TIME_LEN - 1 \|\|
	strlen( not_after ) != MBEDTLS_X509_RFC5280_UTC_TIME_LEN - 1 )
	{
	return( MBEDTLS_ERR_X509_BAD_INPUT_DATA );
	}
	strncpy( ctx->not_before, not_before, MBEDTLS_X509_RFC5280_UTC_TIME_LEN );
	strncpy( ctx->not_after , not_after , MBEDTLS_X509_RFC5280_UTC_TIME_LEN );
	ctx->not_before[MBEDTLS_X509_RFC5280_UTC_TIME_LEN - 1] = 'Z';
	ctx->not_after[MBEDTLS_X509_RFC5280_UTC_TIME_LEN - 1] = 'Z';

	return( 0 );
	}

	int mbedtls_x509write_crt_set_extension( mbedtls_x509write_cert *ctx,
	const char *oid, size_t oid_len,
	int critical,
	const unsigned char *val, size_t val_len )
	{
	return mbedtls_x509_set_extension( &ctx->extensions, oid, oid_len,
	critical, val, val_len );
	}

	int mbedtls_x509write_crt_set_basic_constraints( mbedtls_x509write_cert *ctx,
	int is_ca, int max_pathlen )
	{
	int ret;
	unsigned char buf[9];
	unsigned char *c = buf + sizeof(buf);
	size_t len = 0;

	memset( buf, 0, sizeof(buf) );

	if( is_ca && max_pathlen > 127 )
	return( MBEDTLS_ERR_X509_BAD_INPUT_DATA );

	if( is_ca )
	{
	if( max_pathlen >= 0 )
	{
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_int( &c, buf, max_pathlen ) );
	}
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_bool( &c, buf, 1 ) );
	}

	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_CONSTRUCTED \|
	MBEDTLS_ASN1_SEQUENCE ) );

	return mbedtls_x509write_crt_set_extension( ctx, MBEDTLS_OID_BASIC_CONSTRAINTS,
	MBEDTLS_OID_SIZE( MBEDTLS_OID_BASIC_CONSTRAINTS ),
	0, buf + sizeof(buf) - len, len );
	}

	#if defined(MBEDTLS_SHA1_C)
	int mbedtls_x509write_crt_set_subject_key_identifier( mbedtls_x509write_cert *ctx )
	{
	int ret;
	unsigned char buf[MBEDTLS_MPI_MAX_SIZE * 2 + 20]; /* tag, length + 2xMPI */
	unsigned char *c = buf + sizeof(buf);
	size_t len = 0;

	memset( buf, 0, sizeof(buf) );
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_pk_write_pubkey( &c, buf, ctx->subject_key ) );

	ret = mbedtls_sha1_ret( buf + sizeof( buf ) - len, len,
	buf + sizeof( buf ) - 20 );
	if( ret != 0 )
	return( ret );
	c = buf + sizeof( buf ) - 20;
	len = 20;

	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_OCTET_STRING ) );

	return mbedtls_x509write_crt_set_extension( ctx, MBEDTLS_OID_SUBJECT_KEY_IDENTIFIER,
	MBEDTLS_OID_SIZE( MBEDTLS_OID_SUBJECT_KEY_IDENTIFIER ),
	0, buf + sizeof(buf) - len, len );
	}

	int mbedtls_x509write_crt_set_authority_key_identifier( mbedtls_x509write_cert *ctx )
	{
	int ret;
	unsigned char buf[MBEDTLS_MPI_MAX_SIZE * 2 + 20]; /* tag, length + 2xMPI */
	unsigned char *c = buf + sizeof( buf );
	size_t len = 0;

	memset( buf, 0, sizeof(buf) );
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_pk_write_pubkey( &c, buf, ctx->issuer_key ) );

	ret = mbedtls_sha1_ret( buf + sizeof( buf ) - len, len,
	buf + sizeof( buf ) - 20 );
	if( ret != 0 )
	return( ret );
	c = buf + sizeof( buf ) - 20;
	len = 20;

	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_CONTEXT_SPECIFIC \| 0 ) );

	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_CONSTRUCTED \|
	MBEDTLS_ASN1_SEQUENCE ) );

	return mbedtls_x509write_crt_set_extension( ctx, MBEDTLS_OID_AUTHORITY_KEY_IDENTIFIER,
	MBEDTLS_OID_SIZE( MBEDTLS_OID_AUTHORITY_KEY_IDENTIFIER ),
	0, buf + sizeof( buf ) - len, len );
	}
	#endif /* MBEDTLS_SHA1_C */

	static size_t crt_get_unused_bits_for_named_bitstring( unsigned char bitstring,
	size_t bit_offset )
	{
	size_t unused_bits;

	/* Count the unused bits removing trailing 0s */
	for( unused_bits = bit_offset; unused_bits < 8; unused_bits++ )
	if( ( ( bitstring >> unused_bits ) & 0x1 ) != 0 )
	break;

	return( unused_bits );
	}

	int mbedtls_x509write_crt_set_key_usage( mbedtls_x509write_cert *ctx,
	unsigned int key_usage )
	{
	unsigned char buf[4], ku;
	unsigned char *c;
	int ret;
	size_t unused_bits;
	const unsigned int allowed_bits = MBEDTLS_X509_KU_DIGITAL_SIGNATURE \|
	MBEDTLS_X509_KU_NON_REPUDIATION \|
	MBEDTLS_X509_KU_KEY_ENCIPHERMENT \|
	MBEDTLS_X509_KU_DATA_ENCIPHERMENT \|
	MBEDTLS_X509_KU_KEY_AGREEMENT \|
	MBEDTLS_X509_KU_KEY_CERT_SIGN \|
	MBEDTLS_X509_KU_CRL_SIGN;

	/* Check that nothing other than the allowed flags is set */
	if( ( key_usage & ~allowed_bits ) != 0 )
	return( MBEDTLS_ERR_X509_FEATURE_UNAVAILABLE );

	c = buf + 4;
	ku = (unsigned char)key_usage;
	unused_bits = crt_get_unused_bits_for_named_bitstring( ku, 1 );
	ret = mbedtls_asn1_write_bitstring( &c, buf, &ku, 8 - unused_bits );

	if( ret < 0 )
	return( ret );
	else if( ret < 3 \|\| ret > 4 )
	return( MBEDTLS_ERR_X509_INVALID_FORMAT );

	ret = mbedtls_x509write_crt_set_extension( ctx, MBEDTLS_OID_KEY_USAGE,
	MBEDTLS_OID_SIZE( MBEDTLS_OID_KEY_USAGE ),
	1, c, (size_t)ret );
	if( ret != 0 )
	return( ret );

	return( 0 );
	}

	int mbedtls_x509write_crt_set_ns_cert_type( mbedtls_x509write_cert *ctx,
	unsigned char ns_cert_type )
	{
	unsigned char buf[4];
	unsigned char *c;
	size_t unused_bits;
	int ret;

	c = buf + 4;

	unused_bits = crt_get_unused_bits_for_named_bitstring( ns_cert_type, 0 );
	ret = mbedtls_asn1_write_bitstring( &c,
	buf,
	&ns_cert_type,
	8 - unused_bits );
	if( ret < 3 \|\| ret > 4 )
	return( ret );

	ret = mbedtls_x509write_crt_set_extension( ctx, MBEDTLS_OID_NS_CERT_TYPE,
	MBEDTLS_OID_SIZE( MBEDTLS_OID_NS_CERT_TYPE ),
	0, c, (size_t)ret );
	if( ret != 0 )
	return( ret );

	return( 0 );
	}

	static int x509_write_time( unsigned char *p, unsigned char start,
	const char *t, size_t size )
	{
	int ret;
	size_t len = 0;

	/*
	* write MBEDTLS_ASN1_UTC_TIME if year < 2050 (2 bytes shorter)
	*/
	if( t[0] == '2' && t[1] == '0' && t[2] < '5' )
	{
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
	(const unsigned char *) t + 2,
	size - 2 ) );
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_UTC_TIME ) );
	}
	else
	{
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
	(const unsigned char *) t,
	size ) );
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_GENERALIZED_TIME ) );
	}

	return( (int) len );
	}

	int mbedtls_x509write_crt_der( mbedtls_x509write_cert ctx, unsigned char buf, size_t size,
	int (f_rng)(void , unsigned char *, size_t),
	void *p_rng )
	{
	int ret;
	const char *sig_oid;
	size_t sig_oid_len = 0;
	unsigned char c, c2;
	unsigned char hash[64];
	unsigned char sig[MBEDTLS_MPI_MAX_SIZE];
	unsigned char tmp_buf[2048];
	size_t sub_len = 0, pub_len = 0, sig_and_oid_len = 0, sig_len;
	size_t len = 0;
	mbedtls_pk_type_t pk_alg;

	/*
	* Prepare data to be signed in tmp_buf
	*/
	c = tmp_buf + sizeof( tmp_buf );

	/* Signature algorithm needed in TBS, and later for actual signature */

	/* There's no direct way of extracting a signature algorithm
	* (represented as an element of mbedtls_pk_type_t) from a PK instance. */
	if( mbedtls_pk_can_do( ctx->issuer_key, MBEDTLS_PK_RSA ) )
	pk_alg = MBEDTLS_PK_RSA;
	else if( mbedtls_pk_can_do( ctx->issuer_key, MBEDTLS_PK_ECDSA ) )
	pk_alg = MBEDTLS_PK_ECDSA;
	else
	return( MBEDTLS_ERR_X509_INVALID_ALG );

	if( ( ret = mbedtls_oid_get_oid_by_sig_alg( pk_alg, ctx->md_alg,
	&sig_oid, &sig_oid_len ) ) != 0 )
	{
	return( ret );
	}

	/*
	* Extensions ::= SEQUENCE SIZE (1..MAX) OF Extension
	*/

	/* Only for v3 */
	if( ctx->version == MBEDTLS_X509_CRT_VERSION_3 )
	{
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_x509_write_extensions( &c, tmp_buf, ctx->extensions ) );
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, len ) );
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONSTRUCTED \|
	MBEDTLS_ASN1_SEQUENCE ) );
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, len ) );
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONTEXT_SPECIFIC \|
	MBEDTLS_ASN1_CONSTRUCTED \| 3 ) );
	}

	/*
	* SubjectPublicKeyInfo
	*/
	MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_pk_write_pubkey_der( ctx->subject_key,
	tmp_buf, c - tmp_buf ) );
	c -= pub_len;
	len += pub_len;

	/*
	* Subject ::= Name
	*/
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_x509_write_names( &c, tmp_buf, ctx->subject ) );

	/*
	* Validity ::= SEQUENCE {
	* notBefore Time,
	* notAfter Time }
	*/
	sub_len = 0;

	MBEDTLS_ASN1_CHK_ADD( sub_len, x509_write_time( &c, tmp_buf, ctx->not_after,
	MBEDTLS_X509_RFC5280_UTC_TIME_LEN ) );

	MBEDTLS_ASN1_CHK_ADD( sub_len, x509_write_time( &c, tmp_buf, ctx->not_before,
	MBEDTLS_X509_RFC5280_UTC_TIME_LEN ) );

	len += sub_len;
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, sub_len ) );
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONSTRUCTED \|
	MBEDTLS_ASN1_SEQUENCE ) );

	/*
	* Issuer ::= Name
	*/
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_x509_write_names( &c, tmp_buf, ctx->issuer ) );

	/*
	* Signature ::= AlgorithmIdentifier
	*/
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_algorithm_identifier( &c, tmp_buf,
	sig_oid, strlen( sig_oid ), 0 ) );

	/*
	* Serial ::= INTEGER
	*/
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &c, tmp_buf, &ctx->serial ) );

	/*
	* Version ::= INTEGER { v1(0), v2(1), v3(2) }
	*/

	/* Can be omitted for v1 */
	if( ctx->version != MBEDTLS_X509_CRT_VERSION_1 )
	{
	sub_len = 0;
	MBEDTLS_ASN1_CHK_ADD( sub_len, mbedtls_asn1_write_int( &c, tmp_buf, ctx->version ) );
	len += sub_len;
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, sub_len ) );
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONTEXT_SPECIFIC \|
	MBEDTLS_ASN1_CONSTRUCTED \| 0 ) );
	}

	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, len ) );
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONSTRUCTED \|
	MBEDTLS_ASN1_SEQUENCE ) );

	/*
	* Make signature
	*/
	if( ( ret = mbedtls_md( mbedtls_md_info_from_type( ctx->md_alg ), c,
	len, hash ) ) != 0 )
	{
	return( ret );
	}

	if( ( ret = mbedtls_pk_sign( ctx->issuer_key, ctx->md_alg, hash, 0, sig, &sig_len,
	f_rng, p_rng ) ) != 0 )
	{
	return( ret );
	}

	/*
	* Write data to output buffer
	*/
	c2 = buf + size;
	MBEDTLS_ASN1_CHK_ADD( sig_and_oid_len, mbedtls_x509_write_sig( &c2, buf,
	sig_oid, sig_oid_len, sig, sig_len ) );

	if( len > (size_t)( c2 - buf ) )
	return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );

	c2 -= len;
	memcpy( c2, c, len );

	len += sig_and_oid_len;
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c2, buf, len ) );
	MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c2, buf, MBEDTLS_ASN1_CONSTRUCTED \|
	MBEDTLS_ASN1_SEQUENCE ) );

	return( (int) len );
	}

	#define PEM_BEGIN_CRT "-----BEGIN CERTIFICATE-----\n"
	#define PEM_END_CRT "-----END CERTIFICATE-----\n"

	#if defined(MBEDTLS_PEM_WRITE_C)
	int mbedtls_x509write_crt_pem( mbedtls_x509write_cert crt, unsigned char buf, size_t size,
	int (f_rng)(void , unsigned char *, size_t),
	void *p_rng )
	{
	int ret;
	unsigned char output_buf[4096];
	size_t olen = 0;

	if( ( ret = mbedtls_x509write_crt_der( crt, output_buf, sizeof(output_buf),
	f_rng, p_rng ) ) < 0 )
	{
	return( ret );
	}

	if( ( ret = mbedtls_pem_write_buffer( PEM_BEGIN_CRT, PEM_END_CRT,
	output_buf + sizeof(output_buf) - ret,
	ret, buf, size, &olen ) ) != 0 )
	{
	return( ret );
	}

	return( 0 );
	}
	#endif /* MBEDTLS_PEM_WRITE_C */

	#endif /* MBEDTLS_X509_CRT_WRITE_C */