library/asn1parse.c - third_party/github/ARMmbed/mbedtls - Git at Google

 /*
  *  Generic ASN.1 parsing
  *
  *  Copyright The Mbed TLS Contributors
  *  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.
  */

 #include "common.h"

 #if defined(MBEDTLS_ASN1_PARSE_C)

 #include "mbedtls/asn1.h"
 #include "mbedtls/platform_util.h"
 #include "mbedtls/error.h"

 #include <string.h>

 #if defined(MBEDTLS_BIGNUM_C)
 #include "mbedtls/bignum.h"
 #endif

 #if defined(MBEDTLS_PLATFORM_C)
 #include "mbedtls/platform.h"
 #else
 #include <stdlib.h>
 #define mbedtls_calloc    calloc
 #define mbedtls_free       free
 #endif

 /*
  * ASN.1 DER decoding routines
  */
 int mbedtls_asn1_get_len( unsigned char **p,
                   const unsigned char *end,
                   size_t *len )
 {
     if( ( end - *p ) < 1 )
         return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );

     if( ( **p & 0x80 ) == 0 )
         *len = *(*p)++;
     else
     {
         switch( **p & 0x7F )
         {
         case 1:
             if( ( end - *p ) < 2 )
                 return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );

             *len = (*p)[1];
             (*p) += 2;
             break;

         case 2:
             if( ( end - *p ) < 3 )
                 return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );

             *len = ( (size_t)(*p)[1] << 8 ) | (*p)[2];
             (*p) += 3;
             break;

         case 3:
             if( ( end - *p ) < 4 )
                 return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );

             *len = ( (size_t)(*p)[1] << 16 ) |
                    ( (size_t)(*p)[2] << 8  ) | (*p)[3];
             (*p) += 4;
             break;

         case 4:
             if( ( end - *p ) < 5 )
                 return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );

             *len = ( (size_t)(*p)[1] << 24 ) | ( (size_t)(*p)[2] << 16 ) |
                    ( (size_t)(*p)[3] << 8  ) |           (*p)[4];
             (*p) += 5;
             break;

         default:
             return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
         }
     }

     if( *len > (size_t) ( end - *p ) )
         return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );

     return( 0 );
 }

 int mbedtls_asn1_get_tag( unsigned char **p,
                   const unsigned char *end,
                   size_t *len, int tag )
 {
     if( ( end - *p ) < 1 )
         return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );

     if( **p != tag )
         return( MBEDTLS_ERR_ASN1_UNEXPECTED_TAG );

     (*p)++;

     return( mbedtls_asn1_get_len( p, end, len ) );
 }

 int mbedtls_asn1_get_bool( unsigned char **p,
                    const unsigned char *end,
                    int *val )
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     size_t len;

     if( ( ret = mbedtls_asn1_get_tag( p, end, &len, MBEDTLS_ASN1_BOOLEAN ) ) != 0 )
         return( ret );

     if( len != 1 )
         return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );

     *val = ( **p != 0 ) ? 1 : 0;
     (*p)++;

     return( 0 );
 }

 static int asn1_get_tagged_int( unsigned char **p,
                                 const unsigned char *end,
                                 int tag, int *val )
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     size_t len;

     if( ( ret = mbedtls_asn1_get_tag( p, end, &len, tag ) ) != 0 )
         return( ret );

     /*
      * len==0 is malformed (0 must be represented as 020100 for INTEGER,
      * or 0A0100 for ENUMERATED tags
      */
     if( len == 0 )
         return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
     /* This is a cryptography library. Reject negative integers. */
     if( ( **p & 0x80 ) != 0 )
         return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );

     /* Skip leading zeros. */
     while( len > 0 && **p == 0 )
     {
         ++( *p );
         --len;
     }

     /* Reject integers that don't fit in an int. This code assumes that
      * the int type has no padding bit. */
     if( len > sizeof( int ) )
         return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
     if( len == sizeof( int ) && ( **p & 0x80 ) != 0 )
         return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );

     *val = 0;
     while( len-- > 0 )
     {
         *val = ( *val << 8 ) | **p;
         (*p)++;
     }

     return( 0 );
 }

 int mbedtls_asn1_get_int( unsigned char **p,
                           const unsigned char *end,
                           int *val )
 {
     return( asn1_get_tagged_int( p, end, MBEDTLS_ASN1_INTEGER, val) );
 }

 int mbedtls_asn1_get_enum( unsigned char **p,
                            const unsigned char *end,
                            int *val )
 {
     return( asn1_get_tagged_int( p, end, MBEDTLS_ASN1_ENUMERATED, val) );
 }

 #if defined(MBEDTLS_BIGNUM_C)
 int mbedtls_asn1_get_mpi( unsigned char **p,
                   const unsigned char *end,
                   mbedtls_mpi *X )
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     size_t len;

     if( ( ret = mbedtls_asn1_get_tag( p, end, &len, MBEDTLS_ASN1_INTEGER ) ) != 0 )
         return( ret );

     ret = mbedtls_mpi_read_binary( X, *p, len );

     *p += len;

     return( ret );
 }
 #endif /* MBEDTLS_BIGNUM_C */

 int mbedtls_asn1_get_bitstring( unsigned char **p, const unsigned char *end,
                         mbedtls_asn1_bitstring *bs)
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

     /* Certificate type is a single byte bitstring */
     if( ( ret = mbedtls_asn1_get_tag( p, end, &bs->len, MBEDTLS_ASN1_BIT_STRING ) ) != 0 )
         return( ret );

     /* Check length, subtract one for actual bit string length */
     if( bs->len < 1 )
         return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );
     bs->len -= 1;

     /* Get number of unused bits, ensure unused bits <= 7 */
     bs->unused_bits = **p;
     if( bs->unused_bits > 7 )
         return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
     (*p)++;

     /* Get actual bitstring */
     bs->p = *p;
     *p += bs->len;

     if( *p != end )
         return( MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );

     return( 0 );
 }

 /*
  * Traverse an ASN.1 "SEQUENCE OF <tag>"
  * and call a callback for each entry found.
  */
 int mbedtls_asn1_traverse_sequence_of(
     unsigned char **p,
     const unsigned char *end,
     unsigned char tag_must_mask, unsigned char tag_must_val,
     unsigned char tag_may_mask, unsigned char tag_may_val,
     int (*cb)( void *ctx, int tag,
                unsigned char *start, size_t len ),
     void *ctx )
 {
     int ret;
     size_t len;

     /* Get main sequence tag */
     if( ( ret = mbedtls_asn1_get_tag( p, end, &len,
             MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
     {
         return( ret );
     }

     if( *p + len != end )
         return( MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );

     while( *p < end )
     {
         unsigned char const tag = *(*p)++;

         if( ( tag & tag_must_mask ) != tag_must_val )
             return( MBEDTLS_ERR_ASN1_UNEXPECTED_TAG );

         if( ( ret = mbedtls_asn1_get_len( p, end, &len ) ) != 0 )
             return( ret );

         if( ( tag & tag_may_mask ) == tag_may_val )
         {
             if( cb != NULL )
             {
                 ret = cb( ctx, tag, *p, len );
                 if( ret != 0 )
                     return( ret );
             }
         }

         *p += len;
     }

     return( 0 );
 }

 /*
  * Get a bit string without unused bits
  */
 int mbedtls_asn1_get_bitstring_null( unsigned char **p, const unsigned char *end,
                              size_t *len )
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

     if( ( ret = mbedtls_asn1_get_tag( p, end, len, MBEDTLS_ASN1_BIT_STRING ) ) != 0 )
         return( ret );

     if( *len == 0 )
         return( MBEDTLS_ERR_ASN1_INVALID_DATA );
     --( *len );

     if( **p != 0 )
         return( MBEDTLS_ERR_ASN1_INVALID_DATA );
     ++( *p );

     return( 0 );
 }

 void mbedtls_asn1_sequence_free( mbedtls_asn1_sequence *seq )
 {
     while( seq != NULL )
     {
         mbedtls_asn1_sequence *next = seq->next;
         mbedtls_platform_zeroize( seq, sizeof( *seq ) );
         mbedtls_free( seq );
         seq = next;
     }
 }

 typedef struct
 {
     int tag;
     mbedtls_asn1_sequence *cur;
 } asn1_get_sequence_of_cb_ctx_t;

 static int asn1_get_sequence_of_cb( void *ctx,
                                     int tag,
                                     unsigned char *start,
                                     size_t len )
 {
     asn1_get_sequence_of_cb_ctx_t *cb_ctx =
         (asn1_get_sequence_of_cb_ctx_t *) ctx;
     mbedtls_asn1_sequence *cur =
         cb_ctx->cur;

     if( cur->buf.p != NULL )
     {
         cur->next =
             mbedtls_calloc( 1, sizeof( mbedtls_asn1_sequence ) );

         if( cur->next == NULL )
             return( MBEDTLS_ERR_ASN1_ALLOC_FAILED );

         cur = cur->next;
     }

     cur->buf.p = start;
     cur->buf.len = len;
     cur->buf.tag = tag;

     cb_ctx->cur = cur;
     return( 0 );
 }

 /*
  *  Parses and splits an ASN.1 "SEQUENCE OF <tag>"
  */
 int mbedtls_asn1_get_sequence_of( unsigned char **p,
                           const unsigned char *end,
                           mbedtls_asn1_sequence *cur,
                           int tag)
 {
     asn1_get_sequence_of_cb_ctx_t cb_ctx = { tag, cur };
     memset( cur, 0, sizeof( mbedtls_asn1_sequence ) );
     return( mbedtls_asn1_traverse_sequence_of(
                 p, end, 0xFF, tag, 0, 0,
                 asn1_get_sequence_of_cb, &cb_ctx ) );
 }

 int mbedtls_asn1_get_alg( unsigned char **p,
                   const unsigned char *end,
                   mbedtls_asn1_buf *alg, mbedtls_asn1_buf *params )
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     size_t len;

     if( ( ret = mbedtls_asn1_get_tag( p, end, &len,
             MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
         return( ret );

     if( ( end - *p ) < 1 )
         return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );

     alg->tag = **p;
     end = *p + len;

     if( ( ret = mbedtls_asn1_get_tag( p, end, &alg->len, MBEDTLS_ASN1_OID ) ) != 0 )
         return( ret );

     alg->p = *p;
     *p += alg->len;

     if( *p == end )
     {
         mbedtls_platform_zeroize( params, sizeof(mbedtls_asn1_buf) );
         return( 0 );
     }

     params->tag = **p;
     (*p)++;

     if( ( ret = mbedtls_asn1_get_len( p, end, &params->len ) ) != 0 )
         return( ret );

     params->p = *p;
     *p += params->len;

     if( *p != end )
         return( MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );

     return( 0 );
 }

 int mbedtls_asn1_get_alg_null( unsigned char **p,
                        const unsigned char *end,
                        mbedtls_asn1_buf *alg )
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     mbedtls_asn1_buf params;

     memset( &params, 0, sizeof(mbedtls_asn1_buf) );

     if( ( ret = mbedtls_asn1_get_alg( p, end, alg, &params ) ) != 0 )
         return( ret );

     if( ( params.tag != MBEDTLS_ASN1_NULL && params.tag != 0 ) || params.len != 0 )
         return( MBEDTLS_ERR_ASN1_INVALID_DATA );

     return( 0 );
 }

 void mbedtls_asn1_free_named_data( mbedtls_asn1_named_data *cur )
 {
     if( cur == NULL )
         return;

     mbedtls_free( cur->oid.p );
     mbedtls_free( cur->val.p );

     mbedtls_platform_zeroize( cur, sizeof( mbedtls_asn1_named_data ) );
 }

 void mbedtls_asn1_free_named_data_list( mbedtls_asn1_named_data **head )
 {
     mbedtls_asn1_named_data *cur;

     while( ( cur = *head ) != NULL )
     {
         *head = cur->next;
         mbedtls_asn1_free_named_data( cur );
         mbedtls_free( cur );
     }
 }

 const mbedtls_asn1_named_data *mbedtls_asn1_find_named_data( const mbedtls_asn1_named_data *list,
                                        const char *oid, size_t len )
 {
     while( list != NULL )
     {
         if( list->oid.len == len &&
             memcmp( list->oid.p, oid, len ) == 0 )
         {
             break;
         }

         list = list->next;
     }

     return( list );
 }

 #endif /* MBEDTLS_ASN1_PARSE_C */
	/*
	* Generic ASN.1 parsing
	*
	* Copyright The Mbed TLS Contributors
	* 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.
	*/

	#include "common.h"

	#if defined(MBEDTLS_ASN1_PARSE_C)

	#include "mbedtls/asn1.h"
	#include "mbedtls/platform_util.h"
	#include "mbedtls/error.h"

	#include <string.h>

	#if defined(MBEDTLS_BIGNUM_C)
	#include "mbedtls/bignum.h"
	#endif

	#if defined(MBEDTLS_PLATFORM_C)
	#include "mbedtls/platform.h"
	#else
	#include <stdlib.h>
	#define mbedtls_calloc calloc
	#define mbedtls_free free
	#endif

	/*
	* ASN.1 DER decoding routines
	*/
	int mbedtls_asn1_get_len( unsigned char **p,
	const unsigned char *end,
	size_t *len )
	{
	if( ( end - *p ) < 1 )
	return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );

	if( ( **p & 0x80 ) == 0 )
	len = (*p)++;
	else
	{
	switch( **p & 0x7F )
	{
	case 1:
	if( ( end - *p ) < 2 )
	return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );

	len = (p)[1];
	(*p) += 2;
	break;

	case 2:
	if( ( end - *p ) < 3 )
	return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );

	len = ( (size_t)(p)[1] << 8 ) \| (*p)[2];
	(*p) += 3;
	break;

	case 3:
	if( ( end - *p ) < 4 )
	return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );

	len = ( (size_t)(p)[1] << 16 ) \|
	( (size_t)(p)[2] << 8 ) \| (p)[3];
	(*p) += 4;
	break;

	case 4:
	if( ( end - *p ) < 5 )
	return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );

	len = ( (size_t)(p)[1] << 24 ) \| ( (size_t)(*p)[2] << 16 ) \|
	( (size_t)(p)[3] << 8 ) \| (p)[4];
	(*p) += 5;
	break;

	default:
	return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
	}
	}

	if( len > (size_t) ( end - p ) )
	return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );

	return( 0 );
	}

	int mbedtls_asn1_get_tag( unsigned char **p,
	const unsigned char *end,
	size_t *len, int tag )
	{
	if( ( end - *p ) < 1 )
	return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );

	if( **p != tag )
	return( MBEDTLS_ERR_ASN1_UNEXPECTED_TAG );

	(*p)++;

	return( mbedtls_asn1_get_len( p, end, len ) );
	}

	int mbedtls_asn1_get_bool( unsigned char **p,
	const unsigned char *end,
	int *val )
	{
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
	size_t len;

	if( ( ret = mbedtls_asn1_get_tag( p, end, &len, MBEDTLS_ASN1_BOOLEAN ) ) != 0 )
	return( ret );

	if( len != 1 )
	return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );

	val = ( *p != 0 ) ? 1 : 0;
	(*p)++;

	return( 0 );
	}

	static int asn1_get_tagged_int( unsigned char **p,
	const unsigned char *end,
	int tag, int *val )
	{
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
	size_t len;

	if( ( ret = mbedtls_asn1_get_tag( p, end, &len, tag ) ) != 0 )
	return( ret );

	/*
	* len==0 is malformed (0 must be represented as 020100 for INTEGER,
	* or 0A0100 for ENUMERATED tags
	*/
	if( len == 0 )
	return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
	/* This is a cryptography library. Reject negative integers. */
	if( ( **p & 0x80 ) != 0 )
	return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );

	/* Skip leading zeros. */
	while( len > 0 && **p == 0 )
	{
	++( *p );
	--len;
	}

	/* Reject integers that don't fit in an int. This code assumes that
	* the int type has no padding bit. */
	if( len > sizeof( int ) )
	return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
	if( len == sizeof( int ) && ( **p & 0x80 ) != 0 )
	return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );

	*val = 0;
	while( len-- > 0 )
	{
	val = ( val << 8 ) \| **p;
	(*p)++;
	}

	return( 0 );
	}

	int mbedtls_asn1_get_int( unsigned char **p,
	const unsigned char *end,
	int *val )
	{
	return( asn1_get_tagged_int( p, end, MBEDTLS_ASN1_INTEGER, val) );
	}

	int mbedtls_asn1_get_enum( unsigned char **p,
	const unsigned char *end,
	int *val )
	{
	return( asn1_get_tagged_int( p, end, MBEDTLS_ASN1_ENUMERATED, val) );
	}

	#if defined(MBEDTLS_BIGNUM_C)
	int mbedtls_asn1_get_mpi( unsigned char **p,
	const unsigned char *end,
	mbedtls_mpi *X )
	{
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
	size_t len;

	if( ( ret = mbedtls_asn1_get_tag( p, end, &len, MBEDTLS_ASN1_INTEGER ) ) != 0 )
	return( ret );

	ret = mbedtls_mpi_read_binary( X, *p, len );

	*p += len;

	return( ret );
	}
	#endif /* MBEDTLS_BIGNUM_C */

	int mbedtls_asn1_get_bitstring( unsigned char *p, const unsigned char end,
	mbedtls_asn1_bitstring *bs)
	{
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

	/* Certificate type is a single byte bitstring */
	if( ( ret = mbedtls_asn1_get_tag( p, end, &bs->len, MBEDTLS_ASN1_BIT_STRING ) ) != 0 )
	return( ret );

	/* Check length, subtract one for actual bit string length */
	if( bs->len < 1 )
	return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );
	bs->len -= 1;

	/* Get number of unused bits, ensure unused bits <= 7 */
	bs->unused_bits = **p;
	if( bs->unused_bits > 7 )
	return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
	(*p)++;

	/* Get actual bitstring */
	bs->p = *p;
	*p += bs->len;

	if( *p != end )
	return( MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );

	return( 0 );
	}

	/*
	* Traverse an ASN.1 "SEQUENCE OF <tag>"
	* and call a callback for each entry found.
	*/
	int mbedtls_asn1_traverse_sequence_of(
	unsigned char **p,
	const unsigned char *end,
	unsigned char tag_must_mask, unsigned char tag_must_val,
	unsigned char tag_may_mask, unsigned char tag_may_val,
	int (cb)( void ctx, int tag,
	unsigned char *start, size_t len ),
	void *ctx )
	{
	int ret;
	size_t len;

	/* Get main sequence tag */
	if( ( ret = mbedtls_asn1_get_tag( p, end, &len,
	MBEDTLS_ASN1_CONSTRUCTED \| MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
	{
	return( ret );
	}

	if( *p + len != end )
	return( MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );

	while( *p < end )
	{
	unsigned char const tag = (p)++;

	if( ( tag & tag_must_mask ) != tag_must_val )
	return( MBEDTLS_ERR_ASN1_UNEXPECTED_TAG );

	if( ( ret = mbedtls_asn1_get_len( p, end, &len ) ) != 0 )
	return( ret );

	if( ( tag & tag_may_mask ) == tag_may_val )
	{
	if( cb != NULL )
	{
	ret = cb( ctx, tag, *p, len );
	if( ret != 0 )
	return( ret );
	}
	}

	*p += len;
	}

	return( 0 );
	}

	/*
	* Get a bit string without unused bits
	*/
	int mbedtls_asn1_get_bitstring_null( unsigned char *p, const unsigned char end,
	size_t *len )
	{
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

	if( ( ret = mbedtls_asn1_get_tag( p, end, len, MBEDTLS_ASN1_BIT_STRING ) ) != 0 )
	return( ret );

	if( *len == 0 )
	return( MBEDTLS_ERR_ASN1_INVALID_DATA );
	--( *len );

	if( **p != 0 )
	return( MBEDTLS_ERR_ASN1_INVALID_DATA );
	++( *p );

	return( 0 );
	}

	void mbedtls_asn1_sequence_free( mbedtls_asn1_sequence *seq )
	{
	while( seq != NULL )
	{
	mbedtls_asn1_sequence *next = seq->next;
	mbedtls_platform_zeroize( seq, sizeof( *seq ) );
	mbedtls_free( seq );
	seq = next;
	}
	}

	typedef struct
	{
	int tag;
	mbedtls_asn1_sequence *cur;
	} asn1_get_sequence_of_cb_ctx_t;

	static int asn1_get_sequence_of_cb( void *ctx,
	int tag,
	unsigned char *start,
	size_t len )
	{
	asn1_get_sequence_of_cb_ctx_t *cb_ctx =
	(asn1_get_sequence_of_cb_ctx_t *) ctx;
	mbedtls_asn1_sequence *cur =
	cb_ctx->cur;

	if( cur->buf.p != NULL )
	{
	cur->next =
	mbedtls_calloc( 1, sizeof( mbedtls_asn1_sequence ) );

	if( cur->next == NULL )
	return( MBEDTLS_ERR_ASN1_ALLOC_FAILED );

	cur = cur->next;
	}

	cur->buf.p = start;
	cur->buf.len = len;
	cur->buf.tag = tag;

	cb_ctx->cur = cur;
	return( 0 );
	}

	/*
	* Parses and splits an ASN.1 "SEQUENCE OF <tag>"
	*/
	int mbedtls_asn1_get_sequence_of( unsigned char **p,
	const unsigned char *end,
	mbedtls_asn1_sequence *cur,
	int tag)
	{
	asn1_get_sequence_of_cb_ctx_t cb_ctx = { tag, cur };
	memset( cur, 0, sizeof( mbedtls_asn1_sequence ) );
	return( mbedtls_asn1_traverse_sequence_of(
	p, end, 0xFF, tag, 0, 0,
	asn1_get_sequence_of_cb, &cb_ctx ) );
	}

	int mbedtls_asn1_get_alg( unsigned char **p,
	const unsigned char *end,
	mbedtls_asn1_buf alg, mbedtls_asn1_buf params )
	{
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
	size_t len;

	if( ( ret = mbedtls_asn1_get_tag( p, end, &len,
	MBEDTLS_ASN1_CONSTRUCTED \| MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
	return( ret );

	if( ( end - *p ) < 1 )
	return( MBEDTLS_ERR_ASN1_OUT_OF_DATA );

	alg->tag = **p;
	end = *p + len;

	if( ( ret = mbedtls_asn1_get_tag( p, end, &alg->len, MBEDTLS_ASN1_OID ) ) != 0 )
	return( ret );

	alg->p = *p;
	*p += alg->len;

	if( *p == end )
	{
	mbedtls_platform_zeroize( params, sizeof(mbedtls_asn1_buf) );
	return( 0 );
	}

	params->tag = **p;
	(*p)++;

	if( ( ret = mbedtls_asn1_get_len( p, end, &params->len ) ) != 0 )
	return( ret );

	params->p = *p;
	*p += params->len;

	if( *p != end )
	return( MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );

	return( 0 );
	}

	int mbedtls_asn1_get_alg_null( unsigned char **p,
	const unsigned char *end,
	mbedtls_asn1_buf *alg )
	{
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
	mbedtls_asn1_buf params;

	memset( &params, 0, sizeof(mbedtls_asn1_buf) );

	if( ( ret = mbedtls_asn1_get_alg( p, end, alg, &params ) ) != 0 )
	return( ret );

	if( ( params.tag != MBEDTLS_ASN1_NULL && params.tag != 0 ) \|\| params.len != 0 )
	return( MBEDTLS_ERR_ASN1_INVALID_DATA );

	return( 0 );
	}

	void mbedtls_asn1_free_named_data( mbedtls_asn1_named_data *cur )
	{
	if( cur == NULL )
	return;

	mbedtls_free( cur->oid.p );
	mbedtls_free( cur->val.p );

	mbedtls_platform_zeroize( cur, sizeof( mbedtls_asn1_named_data ) );
	}

	void mbedtls_asn1_free_named_data_list( mbedtls_asn1_named_data **head )
	{
	mbedtls_asn1_named_data *cur;

	while( ( cur = *head ) != NULL )
	{
	*head = cur->next;
	mbedtls_asn1_free_named_data( cur );
	mbedtls_free( cur );
	}
	}

	const mbedtls_asn1_named_data mbedtls_asn1_find_named_data( const mbedtls_asn1_named_data list,
	const char *oid, size_t len )
	{
	while( list != NULL )
	{
	if( list->oid.len == len &&
	memcmp( list->oid.p, oid, len ) == 0 )
	{
	break;
	}

	list = list->next;
	}

	return( list );
	}

	#endif /* MBEDTLS_ASN1_PARSE_C */