library/x509write.c - security/mbedtls - Rivoreo Source Code Repositories

 /*
  * X509 buffer writing functionality
  *
  *  Copyright (C) 2006-2013, Brainspark B.V.
  *
  *  This file is part of PolarSSL (http://www.polarssl.org)
  *  Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
  *
  *  All rights reserved.
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
  *  the Free Software Foundation; either version 2 of the License, or
  *  (at your option) any later version.
  *
  *  This program is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  *  GNU General Public License for more details.
  *
  *  You should have received a copy of the GNU General Public License along
  *  with this program; if not, write to the Free Software Foundation, Inc.,
  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */

 #include "polarssl/config.h"

 #if defined(POLARSSL_X509_WRITE_C)

 #include "polarssl/asn1write.h"
 #include "polarssl/x509write.h"
 #include "polarssl/x509.h"
 #include "polarssl/md.h"
 #include "polarssl/oid.h"

 #if defined(POLARSSL_MEMORY_C)
 #include "polarssl/memory.h"
 #else
 #include <stdlib.h>
 #define polarssl_malloc     malloc
 #define polarssl_free       free
 #endif

 void x509write_csr_init( x509_csr *ctx )
 {
     memset( ctx, 0, sizeof(x509_csr) );
 }

 void x509write_csr_free( x509_csr *ctx )
 {
     x509_req_name *cur;

     while( ( cur = ctx->subject ) != NULL )
     {
         ctx->subject = cur->next;
         polarssl_free( cur );
     }

     memset( ctx, 0, sizeof(x509_csr) );
 }

 void x509write_csr_set_md_alg( x509_csr *ctx, md_type_t md_alg )
 {
     ctx->md_alg = md_alg;
 }

 void x509write_csr_set_rsa_key( x509_csr *ctx, rsa_context *rsa )
 {
     ctx->rsa = rsa;
 }

 int x509write_csr_set_subject_name( x509_csr *ctx, char *subject_name )
 {
     int ret = 0;
     char *s = subject_name, *c = s;
     char *end = s + strlen( s );
     char *oid = NULL;
     int in_tag = 1;
     x509_req_name *cur;

     while( ctx->subject )
     {
         cur = ctx->subject;
         ctx->subject = ctx->subject->next;
         polarssl_free( cur );
     }

     while( c <= end )
     {
         if( in_tag && *c == '=' )
         {
             if( memcmp( s, "CN", 2 ) == 0 && c - s == 2 )
                 oid = OID_AT_CN;
             else if( memcmp( s, "C", 1 ) == 0 && c - s == 1 )
                 oid = OID_AT_COUNTRY;
             else if( memcmp( s, "O", 1 ) == 0 && c - s == 1 )
                 oid = OID_AT_ORGANIZATION;
             else if( memcmp( s, "L", 1 ) == 0 && c - s == 1 )
                 oid = OID_AT_LOCALITY;
             else if( memcmp( s, "R", 1 ) == 0 && c - s == 1 )
                 oid = OID_PKCS9_EMAIL;
             else if( memcmp( s, "OU", 2 ) == 0 && c - s == 2 )
                 oid = OID_AT_ORG_UNIT;
             else if( memcmp( s, "ST", 2 ) == 0 && c - s == 2 )
                 oid = OID_AT_STATE;
             else
             {
                 ret = POLARSSL_ERR_X509WRITE_UNKNOWN_OID;
                 goto exit;
             }

             s = c + 1;
             in_tag = 0;
         }

         if( !in_tag && ( *c == ',' || c == end ) )
         {
             if( c - s > 127 )
             {
                 ret = POLARSSL_ERR_X509WRITE_BAD_INPUT_DATA;
                 goto exit;
             }

             cur = polarssl_malloc( sizeof(x509_req_name) );

             if( cur == NULL )
             {
                 ret = POLARSSL_ERR_X509WRITE_MALLOC_FAILED;
                 goto exit;
             }

             memset( cur, 0, sizeof(x509_req_name) );

             cur->next = ctx->subject;
             ctx->subject = cur;

             strncpy( cur->oid, oid, strlen( oid ) );
             strncpy( cur->name, s, c - s );

             s = c + 1;
             in_tag = 1;
         }
         c++;
     }

 exit:

     return( ret );
 }

 int x509write_pubkey_der( rsa_context *rsa, unsigned char *buf, size_t size )
 {
     int ret;
     unsigned char *c;
     size_t len = 0;

     c = buf + size - 1;

     /*
     *  RSAPublicKey ::= SEQUENCE {
     *      modulus           INTEGER,  -- n
     *      publicExponent    INTEGER   -- e
     *  }
     */
     ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->E ) );
     ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->N ) );

     ASN1_CHK_ADD( len, asn1_write_len( &c, buf, len ) );
     ASN1_CHK_ADD( len, asn1_write_tag( &c, buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );

     if( c - buf < 1 )
         return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );

     /*
      *  SubjectPublicKeyInfo  ::=  SEQUENCE  {
      *       algorithm            AlgorithmIdentifier,
      *       subjectPublicKey     BIT STRING }
      */
     *--c = 0;
     len += 1;

     ASN1_CHK_ADD( len, asn1_write_len( &c, buf, len ) );
     ASN1_CHK_ADD( len, asn1_write_tag( &c, buf, ASN1_BIT_STRING ) );

     ASN1_CHK_ADD( len, asn1_write_algorithm_identifier( &c, buf, OID_PKCS1_RSA ) );

     ASN1_CHK_ADD( len, asn1_write_len( &c, buf, len ) );
     ASN1_CHK_ADD( len, asn1_write_tag( &c, buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );

     return( len );
 }

 int x509write_key_der( rsa_context *rsa, unsigned char *buf, size_t size )
 {
     int ret;
     unsigned char *c;
     size_t len = 0;

     c = buf + size - 1;

     ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->QP ) );
     ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->DQ ) );
     ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->DP ) );
     ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->Q ) );
     ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->P ) );
     ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->D ) );
     ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->E ) );
     ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->N ) );
     ASN1_CHK_ADD( len, asn1_write_int( &c, buf, 0 ) );

     ASN1_CHK_ADD( len, asn1_write_len( &c, buf, len ) );
     ASN1_CHK_ADD( len, asn1_write_tag( &c, buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );

     // TODO: Make NON RSA Specific variant later on
 /*    *--c = 0;
     len += 1;

     len += asn1_write_len( &c, len);
     len += asn1_write_tag( &c, ASN1_BIT_STRING );

     len += asn1_write_oid( &c, OID_PKCS1_RSA );

     len += asn1_write_int( &c, 0 );

     len += asn1_write_len( &c, len);
     len += asn1_write_tag( &c, ASN1_CONSTRUCTED | ASN1_SEQUENCE );*/

 /*    for(i = 0; i < len; ++i)
     {
         if (i % 16 == 0 ) printf("\n");
         printf("%02x ", c[i]);
     }
     printf("\n");*/

     return( len );
 }

 static int x509_write_name( unsigned char **p, unsigned char *start, char *oid,
                             char *name )
 {
     int ret;
     size_t string_len = 0;
     size_t oid_len = 0;
     size_t len = 0;

     // Write PrintableString for all except OID_PKCS9_EMAIL
     //
     if( OID_SIZE( OID_PKCS9_EMAIL ) == strlen( oid ) &&
         memcmp( oid, OID_PKCS9_EMAIL, strlen( oid ) ) == 0 )
     {
         ASN1_CHK_ADD( string_len, asn1_write_ia5_string( p, start, name ) );
     }
     else
         ASN1_CHK_ADD( string_len, asn1_write_printable_string( p, start, name ) );

     // Write OID
     //
     ASN1_CHK_ADD( oid_len, asn1_write_oid( p, start, oid ) );

     len = oid_len + string_len;
     ASN1_CHK_ADD( len, asn1_write_len( p, start, oid_len + string_len ) );
     ASN1_CHK_ADD( len, asn1_write_tag( p, start, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );

     ASN1_CHK_ADD( len, asn1_write_len( p, start, len ) );
     ASN1_CHK_ADD( len, asn1_write_tag( p, start, ASN1_CONSTRUCTED | ASN1_SET ) );

     return( len );
 }

 static int x509_write_sig( unsigned char **p, unsigned char *start,
                            const char *oid, unsigned char *sig, size_t size )
 {
     int ret;
     size_t len = 0;

     if( *p - start < (int) size + 1 )
         return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );

     len = size;
     (*p) -= len;
     memcpy( *p, sig, len );

     *--(*p) = 0;
     len += 1;

     ASN1_CHK_ADD( len, asn1_write_len( p, start, len ) );
     ASN1_CHK_ADD( len, asn1_write_tag( p, start, ASN1_BIT_STRING ) );

     // Write OID
     //
     ASN1_CHK_ADD( len, asn1_write_algorithm_identifier( p, start, oid ) );

     return( len );
 }

 int x509write_csr_der( x509_csr *ctx, unsigned char *buf, size_t size )
 {
     int ret;
     const char *sig_oid;
     unsigned char *c, *c2;
     unsigned char hash[64];
     unsigned char sig[POLARSSL_MPI_MAX_SIZE];
     unsigned char tmp_buf[2048];
     size_t sub_len = 0, pub_len = 0, sig_len = 0;
     size_t len = 0;
     x509_req_name *cur = ctx->subject;

     c = tmp_buf + 2048 - 1;

     ASN1_CHK_ADD( len, asn1_write_len( &c, tmp_buf, 0 ) );
     ASN1_CHK_ADD( len, asn1_write_tag( &c, tmp_buf, ASN1_CONSTRUCTED | ASN1_CONTEXT_SPECIFIC ) );

     ASN1_CHK_ADD( pub_len, asn1_write_mpi( &c, tmp_buf, &ctx->rsa->E ) );
     ASN1_CHK_ADD( pub_len, asn1_write_mpi( &c, tmp_buf, &ctx->rsa->N ) );

     ASN1_CHK_ADD( pub_len, asn1_write_len( &c, tmp_buf, pub_len ) );
     ASN1_CHK_ADD( pub_len, asn1_write_tag( &c, tmp_buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );

     if( c - tmp_buf < 1 )
         return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );

     /*
      *  AlgorithmIdentifier  ::=  SEQUENCE  {
      *       algorithm               OBJECT IDENTIFIER,
      *       parameters              ANY DEFINED BY algorithm OPTIONAL  }
      */
     *--c = 0;
     pub_len += 1;

     ASN1_CHK_ADD( pub_len, asn1_write_len( &c, tmp_buf, pub_len ) );
     ASN1_CHK_ADD( pub_len, asn1_write_tag( &c, tmp_buf, ASN1_BIT_STRING ) );

     ASN1_CHK_ADD( pub_len, asn1_write_algorithm_identifier( &c, tmp_buf, OID_PKCS1_RSA ) );

     len += pub_len;
     ASN1_CHK_ADD( len, asn1_write_len( &c, tmp_buf, pub_len ) );
     ASN1_CHK_ADD( len, asn1_write_tag( &c, tmp_buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );

     while( cur != NULL )
     {
         ASN1_CHK_ADD( sub_len, x509_write_name( &c, tmp_buf, cur->oid, cur->name ) );

         cur = cur->next;
     }

     len += sub_len;
     ASN1_CHK_ADD( len, asn1_write_len( &c, tmp_buf, sub_len ) );
     ASN1_CHK_ADD( len, asn1_write_tag( &c, tmp_buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );

     /*
      *  Version  ::=  INTEGER  {  v1(0), v2(1), v3(2)  }
      */
     ASN1_CHK_ADD( len, asn1_write_int( &c, tmp_buf, 0 ) );

     ASN1_CHK_ADD( len, asn1_write_len( &c, tmp_buf, len ) );
     ASN1_CHK_ADD( len, asn1_write_tag( &c, tmp_buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );

     md( md_info_from_type( ctx->md_alg ), c, len, hash );

     rsa_pkcs1_sign( ctx->rsa, NULL, NULL, RSA_PRIVATE, ctx->md_alg, 0, hash, sig );

     // Generate correct OID
     //
     ret = oid_get_oid_by_sig_alg( POLARSSL_PK_RSA, ctx->md_alg, &sig_oid );

     c2 = buf + size - 1;
     ASN1_CHK_ADD( sig_len, x509_write_sig( &c2, buf, sig_oid, sig, ctx->rsa->len ) );

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

     len += sig_len;
     ASN1_CHK_ADD( len, asn1_write_len( &c2, buf, len ) );
     ASN1_CHK_ADD( len, asn1_write_tag( &c2, buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );

     return( len );
 }

 #endif
	/*
	* X509 buffer writing functionality
	*
	* Copyright (C) 2006-2013, Brainspark B.V.
	*
	* This file is part of PolarSSL (http://www.polarssl.org)
	* Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
	*
	* All rights reserved.
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License along
	* with this program; if not, write to the Free Software Foundation, Inc.,
	* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
	*/

	#include "polarssl/config.h"

	#if defined(POLARSSL_X509_WRITE_C)

	#include "polarssl/asn1write.h"
	#include "polarssl/x509write.h"
	#include "polarssl/x509.h"
	#include "polarssl/md.h"
	#include "polarssl/oid.h"

	#if defined(POLARSSL_MEMORY_C)
	#include "polarssl/memory.h"
	#else
	#include <stdlib.h>
	#define polarssl_malloc malloc
	#define polarssl_free free
	#endif

	void x509write_csr_init( x509_csr *ctx )
	{
	memset( ctx, 0, sizeof(x509_csr) );
	}

	void x509write_csr_free( x509_csr *ctx )
	{
	x509_req_name *cur;

	while( ( cur = ctx->subject ) != NULL )
	{
	ctx->subject = cur->next;
	polarssl_free( cur );
	}

	memset( ctx, 0, sizeof(x509_csr) );
	}

	void x509write_csr_set_md_alg( x509_csr *ctx, md_type_t md_alg )
	{
	ctx->md_alg = md_alg;
	}

	void x509write_csr_set_rsa_key( x509_csr ctx, rsa_context rsa )
	{
	ctx->rsa = rsa;
	}

	int x509write_csr_set_subject_name( x509_csr ctx, char subject_name )
	{
	int ret = 0;
	char s = subject_name, c = s;
	char *end = s + strlen( s );
	char *oid = NULL;
	int in_tag = 1;
	x509_req_name *cur;

	while( ctx->subject )
	{
	cur = ctx->subject;
	ctx->subject = ctx->subject->next;
	polarssl_free( cur );
	}

	while( c <= end )
	{
	if( in_tag && *c == '=' )
	{
	if( memcmp( s, "CN", 2 ) == 0 && c - s == 2 )
	oid = OID_AT_CN;
	else if( memcmp( s, "C", 1 ) == 0 && c - s == 1 )
	oid = OID_AT_COUNTRY;
	else if( memcmp( s, "O", 1 ) == 0 && c - s == 1 )
	oid = OID_AT_ORGANIZATION;
	else if( memcmp( s, "L", 1 ) == 0 && c - s == 1 )
	oid = OID_AT_LOCALITY;
	else if( memcmp( s, "R", 1 ) == 0 && c - s == 1 )
	oid = OID_PKCS9_EMAIL;
	else if( memcmp( s, "OU", 2 ) == 0 && c - s == 2 )
	oid = OID_AT_ORG_UNIT;
	else if( memcmp( s, "ST", 2 ) == 0 && c - s == 2 )
	oid = OID_AT_STATE;
	else
	{
	ret = POLARSSL_ERR_X509WRITE_UNKNOWN_OID;
	goto exit;
	}

	s = c + 1;
	in_tag = 0;
	}

	if( !in_tag && ( *c == ',' \|\| c == end ) )
	{
	if( c - s > 127 )
	{
	ret = POLARSSL_ERR_X509WRITE_BAD_INPUT_DATA;
	goto exit;
	}

	cur = polarssl_malloc( sizeof(x509_req_name) );

	if( cur == NULL )
	{
	ret = POLARSSL_ERR_X509WRITE_MALLOC_FAILED;
	goto exit;
	}

	memset( cur, 0, sizeof(x509_req_name) );

	cur->next = ctx->subject;
	ctx->subject = cur;

	strncpy( cur->oid, oid, strlen( oid ) );
	strncpy( cur->name, s, c - s );

	s = c + 1;
	in_tag = 1;
	}
	c++;
	}

	exit:

	return( ret );
	}

	int x509write_pubkey_der( rsa_context rsa, unsigned char buf, size_t size )
	{
	int ret;
	unsigned char *c;
	size_t len = 0;

	c = buf + size - 1;

	/*
	* RSAPublicKey ::= SEQUENCE {
	* modulus INTEGER, -- n
	* publicExponent INTEGER -- e
	* }
	*/
	ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->E ) );
	ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->N ) );

	ASN1_CHK_ADD( len, asn1_write_len( &c, buf, len ) );
	ASN1_CHK_ADD( len, asn1_write_tag( &c, buf, ASN1_CONSTRUCTED \| ASN1_SEQUENCE ) );

	if( c - buf < 1 )
	return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );

	/*
	* SubjectPublicKeyInfo ::= SEQUENCE {
	* algorithm AlgorithmIdentifier,
	* subjectPublicKey BIT STRING }
	*/
	*--c = 0;
	len += 1;

	ASN1_CHK_ADD( len, asn1_write_len( &c, buf, len ) );
	ASN1_CHK_ADD( len, asn1_write_tag( &c, buf, ASN1_BIT_STRING ) );

	ASN1_CHK_ADD( len, asn1_write_algorithm_identifier( &c, buf, OID_PKCS1_RSA ) );

	ASN1_CHK_ADD( len, asn1_write_len( &c, buf, len ) );
	ASN1_CHK_ADD( len, asn1_write_tag( &c, buf, ASN1_CONSTRUCTED \| ASN1_SEQUENCE ) );

	return( len );
	}

	int x509write_key_der( rsa_context rsa, unsigned char buf, size_t size )
	{
	int ret;
	unsigned char *c;
	size_t len = 0;

	c = buf + size - 1;

	ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->QP ) );
	ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->DQ ) );
	ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->DP ) );
	ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->Q ) );
	ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->P ) );
	ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->D ) );
	ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->E ) );
	ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->N ) );
	ASN1_CHK_ADD( len, asn1_write_int( &c, buf, 0 ) );

	ASN1_CHK_ADD( len, asn1_write_len( &c, buf, len ) );
	ASN1_CHK_ADD( len, asn1_write_tag( &c, buf, ASN1_CONSTRUCTED \| ASN1_SEQUENCE ) );

	// TODO: Make NON RSA Specific variant later on
	/* *--c = 0;
	len += 1;

	len += asn1_write_len( &c, len);
	len += asn1_write_tag( &c, ASN1_BIT_STRING );

	len += asn1_write_oid( &c, OID_PKCS1_RSA );

	len += asn1_write_int( &c, 0 );

	len += asn1_write_len( &c, len);
	len += asn1_write_tag( &c, ASN1_CONSTRUCTED \| ASN1_SEQUENCE );*/

	/* for(i = 0; i < len; ++i)
	{
	if (i % 16 == 0 ) printf("\n");
	printf("%02x ", c[i]);
	}
	printf("\n");*/

	return( len );
	}

	static int x509_write_name( unsigned char *p, unsigned char start, char *oid,
	char *name )
	{
	int ret;
	size_t string_len = 0;
	size_t oid_len = 0;
	size_t len = 0;

	// Write PrintableString for all except OID_PKCS9_EMAIL
	//
	if( OID_SIZE( OID_PKCS9_EMAIL ) == strlen( oid ) &&
	memcmp( oid, OID_PKCS9_EMAIL, strlen( oid ) ) == 0 )
	{
	ASN1_CHK_ADD( string_len, asn1_write_ia5_string( p, start, name ) );
	}
	else
	ASN1_CHK_ADD( string_len, asn1_write_printable_string( p, start, name ) );

	// Write OID
	//
	ASN1_CHK_ADD( oid_len, asn1_write_oid( p, start, oid ) );

	len = oid_len + string_len;
	ASN1_CHK_ADD( len, asn1_write_len( p, start, oid_len + string_len ) );
	ASN1_CHK_ADD( len, asn1_write_tag( p, start, ASN1_CONSTRUCTED \| ASN1_SEQUENCE ) );

	ASN1_CHK_ADD( len, asn1_write_len( p, start, len ) );
	ASN1_CHK_ADD( len, asn1_write_tag( p, start, ASN1_CONSTRUCTED \| ASN1_SET ) );

	return( len );
	}

	static int x509_write_sig( unsigned char *p, unsigned char start,
	const char oid, unsigned char sig, size_t size )
	{
	int ret;
	size_t len = 0;

	if( *p - start < (int) size + 1 )
	return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );

	len = size;
	(*p) -= len;
	memcpy( *p, sig, len );

	--(p) = 0;
	len += 1;

	ASN1_CHK_ADD( len, asn1_write_len( p, start, len ) );
	ASN1_CHK_ADD( len, asn1_write_tag( p, start, ASN1_BIT_STRING ) );

	// Write OID
	//
	ASN1_CHK_ADD( len, asn1_write_algorithm_identifier( p, start, oid ) );

	return( len );
	}

	int x509write_csr_der( x509_csr ctx, unsigned char buf, size_t size )
	{
	int ret;
	const char *sig_oid;
	unsigned char c, c2;
	unsigned char hash[64];
	unsigned char sig[POLARSSL_MPI_MAX_SIZE];
	unsigned char tmp_buf[2048];
	size_t sub_len = 0, pub_len = 0, sig_len = 0;
	size_t len = 0;
	x509_req_name *cur = ctx->subject;

	c = tmp_buf + 2048 - 1;

	ASN1_CHK_ADD( len, asn1_write_len( &c, tmp_buf, 0 ) );
	ASN1_CHK_ADD( len, asn1_write_tag( &c, tmp_buf, ASN1_CONSTRUCTED \| ASN1_CONTEXT_SPECIFIC ) );

	ASN1_CHK_ADD( pub_len, asn1_write_mpi( &c, tmp_buf, &ctx->rsa->E ) );
	ASN1_CHK_ADD( pub_len, asn1_write_mpi( &c, tmp_buf, &ctx->rsa->N ) );

	ASN1_CHK_ADD( pub_len, asn1_write_len( &c, tmp_buf, pub_len ) );
	ASN1_CHK_ADD( pub_len, asn1_write_tag( &c, tmp_buf, ASN1_CONSTRUCTED \| ASN1_SEQUENCE ) );

	if( c - tmp_buf < 1 )
	return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );

	/*
	* AlgorithmIdentifier ::= SEQUENCE {
	* algorithm OBJECT IDENTIFIER,
	* parameters ANY DEFINED BY algorithm OPTIONAL }
	*/
	*--c = 0;
	pub_len += 1;

	ASN1_CHK_ADD( pub_len, asn1_write_len( &c, tmp_buf, pub_len ) );
	ASN1_CHK_ADD( pub_len, asn1_write_tag( &c, tmp_buf, ASN1_BIT_STRING ) );

	ASN1_CHK_ADD( pub_len, asn1_write_algorithm_identifier( &c, tmp_buf, OID_PKCS1_RSA ) );

	len += pub_len;
	ASN1_CHK_ADD( len, asn1_write_len( &c, tmp_buf, pub_len ) );
	ASN1_CHK_ADD( len, asn1_write_tag( &c, tmp_buf, ASN1_CONSTRUCTED \| ASN1_SEQUENCE ) );

	while( cur != NULL )
	{
	ASN1_CHK_ADD( sub_len, x509_write_name( &c, tmp_buf, cur->oid, cur->name ) );

	cur = cur->next;
	}

	len += sub_len;
	ASN1_CHK_ADD( len, asn1_write_len( &c, tmp_buf, sub_len ) );
	ASN1_CHK_ADD( len, asn1_write_tag( &c, tmp_buf, ASN1_CONSTRUCTED \| ASN1_SEQUENCE ) );

	/*
	* Version ::= INTEGER { v1(0), v2(1), v3(2) }
	*/
	ASN1_CHK_ADD( len, asn1_write_int( &c, tmp_buf, 0 ) );

	ASN1_CHK_ADD( len, asn1_write_len( &c, tmp_buf, len ) );
	ASN1_CHK_ADD( len, asn1_write_tag( &c, tmp_buf, ASN1_CONSTRUCTED \| ASN1_SEQUENCE ) );

	md( md_info_from_type( ctx->md_alg ), c, len, hash );

	rsa_pkcs1_sign( ctx->rsa, NULL, NULL, RSA_PRIVATE, ctx->md_alg, 0, hash, sig );

	// Generate correct OID
	//
	ret = oid_get_oid_by_sig_alg( POLARSSL_PK_RSA, ctx->md_alg, &sig_oid );

	c2 = buf + size - 1;
	ASN1_CHK_ADD( sig_len, x509_write_sig( &c2, buf, sig_oid, sig, ctx->rsa->len ) );

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

	len += sig_len;
	ASN1_CHK_ADD( len, asn1_write_len( &c2, buf, len ) );
	ASN1_CHK_ADD( len, asn1_write_tag( &c2, buf, ASN1_CONSTRUCTED \| ASN1_SEQUENCE ) );

	return( len );
	}

	#endif