text: /*
   * ASN.1 buffer writing functionality
   *
   *  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)
   */
  
  #if !defined(MBEDTLS_CONFIG_FILE)
  #include "config.h"
  #else
  #include MBEDTLS_CONFIG_FILE
  #endif
  
  #if defined(MBEDTLS_ASN1_WRITE_C)
  
  #include "asn1write.h"
  
  #include <string.h>
  
  #if defined(MBEDTLS_PLATFORM_C)
  #include "platform.h"
  #else
  #include <stdlib.h>
  #define mbedtls_calloc    calloc
  #define mbedtls_free       free
  #endif
  
  int mbedtls_asn1_write_len( unsigned char **p, unsigned char *start, size_t len )
  {
      if( len < 0x80 )
      {
          if( *p - start < 1 )
              return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
  
          *--(*p) = (unsigned char) len;
          return( 1 );
      }
  
      if( len <= 0xFF )
      {
          if( *p - start < 2 )
              return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
  
          *--(*p) = (unsigned char) len;
          *--(*p) = 0x81;
          return( 2 );
      }
  
      if( len <= 0xFFFF )
      {
          if( *p - start < 3 )
              return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
  
          *--(*p) = ( len       ) & 0xFF;
          *--(*p) = ( len >>  8 ) & 0xFF;
          *--(*p) = 0x82;
          return( 3 );
      }
  
      if( len <= 0xFFFFFF )
      {
          if( *p - start < 4 )
              return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
  
          *--(*p) = ( len       ) & 0xFF;
          *--(*p) = ( len >>  8 ) & 0xFF;
          *--(*p) = ( len >> 16 ) & 0xFF;
          *--(*p) = 0x83;
          return( 4 );
      }
  
  #if SIZE_MAX > 0xFFFFFFFF
      if( len <= 0xFFFFFFFF )
  #endif
      {
          if( *p - start < 5 )
              return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
  
          *--(*p) = ( len       ) & 0xFF;
          *--(*p) = ( len >>  8 ) & 0xFF;
          *--(*p) = ( len >> 16 ) & 0xFF;
          *--(*p) = ( len >> 24 ) & 0xFF;
          *--(*p) = 0x84;
          return( 5 );
      }
  
  #if SIZE_MAX > 0xFFFFFFFF
      return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
  #endif
  }
  
  int mbedtls_asn1_write_tag( unsigned char **p, unsigned char *start, unsigned char tag )
  {
      if( *p - start < 1 )
          return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
  
      *--(*p) = tag;
  
      return( 1 );
  }
  
  int mbedtls_asn1_write_raw_buffer( unsigned char **p, unsigned char *start,
                             const unsigned char *buf, size_t size )
  {
      size_t len = 0;
  
      if( *p < start || (size_t)( *p - start ) < size )
          return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
  
      len = size;
      (*p) -= len;
      memcpy( *p, buf, len );
  
      return( (int) len );
  }
  
  #if defined(MBEDTLS_BIGNUM_C)
  int mbedtls_asn1_write_mpi( unsigned char **p, unsigned char *start, const mbedtls_mpi *X )
  {
      int ret;
      size_t len = 0;
  
      // Write the MPI
      //
      len = mbedtls_mpi_size( X );
  
      if( *p < start || (size_t)( *p - start ) < len )
          return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
  
      (*p) -= len;
      MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( X, *p, len ) );
  
      // DER format assumes 2s complement for numbers, so the leftmost bit
      // should be 0 for positive numbers and 1 for negative numbers.
      //
      if( X->s ==1 && **p & 0x80 )
      {
          if( *p - start < 1 )
              return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
  
          *--(*p) = 0x00;
          len += 1;
      }
  
      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_INTEGER ) );
  
      ret = (int) len;
  
  cleanup:
      return( ret );
  }
  #endif /* MBEDTLS_BIGNUM_C */
  
  int mbedtls_asn1_write_null( unsigned char **p, unsigned char *start )
  {
      int ret;
      size_t len = 0;
  
      // Write NULL
      //
      MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, 0) );
      MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_NULL ) );
  
      return( (int) len );
  }
  
  int mbedtls_asn1_write_oid( unsigned char **p, unsigned char *start,
                      const char *oid, size_t oid_len )
  {
      int ret;
      size_t len = 0;
  
      MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
                                    (const unsigned char *) oid, oid_len ) );
      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_OID ) );
  
      return( (int) len );
  }
  
  int mbedtls_asn1_write_algorithm_identifier( unsigned char **p, unsigned char *start,
                                       const char *oid, size_t oid_len,
                                       size_t par_len )
  {
      int ret;
      size_t len = 0;
  
      if( par_len == 0 )
          MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_null( p, start ) );
      else
          len += par_len;
  
      MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_oid( p, start, oid, oid_len ) );
  
      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_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) );
  
      return( (int) len );
  }
  
  int mbedtls_asn1_write_bool( unsigned char **p, unsigned char *start, int boolean )
  {
      int ret;
      size_t len = 0;
  
      if( *p - start < 1 )
          return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
  
      *--(*p) = (boolean) ? 255 : 0;
      len++;
  
      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_BOOLEAN ) );
  
      return( (int) len );
  }
  
  int mbedtls_asn1_write_int( unsigned char **p, unsigned char *start, int val )
  {
      int ret;
      size_t len = 0;
  
      if( *p - start < 1 )
          return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
  
      len += 1;
      *--(*p) = val;
  
      if( val > 0 && **p & 0x80 )
      {
          if( *p - start < 1 )
              return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
  
          *--(*p) = 0x00;
          len += 1;
      }
  
      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_INTEGER ) );
  
      return( (int) len );
  }
  
  int mbedtls_asn1_write_tagged_string( unsigned char **p, unsigned char *start, int tag,
      const char *text, size_t text_len )
  {
      int ret;
      size_t len = 0;
  
      MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
          (const unsigned char *) text, text_len ) );
  
      MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
      MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, tag ) );
  
      return( (int) len );
  }
  
  int mbedtls_asn1_write_utf8_string( unsigned char **p, unsigned char *start,
      const char *text, size_t text_len )
  {
      return( mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_UTF8_STRING, text, text_len) );
  }
  
  int mbedtls_asn1_write_printable_string( unsigned char **p, unsigned char *start,
                                   const char *text, size_t text_len )
  {
      return( mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_PRINTABLE_STRING, text, text_len) );
  }
  
  int mbedtls_asn1_write_ia5_string( unsigned char **p, unsigned char *start,
                             const char *text, size_t text_len )
  {
      return( mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_IA5_STRING, text, text_len) );
  }
  
  int mbedtls_asn1_write_named_bitstring( unsigned char **p,
                                          unsigned char *start,
                                          const unsigned char *buf,
                                          size_t bits )
  {
      size_t unused_bits, byte_len;
      const unsigned char *cur_byte;
      unsigned char cur_byte_shifted;
      unsigned char bit;
  
      byte_len = ( bits + 7 ) / 8;
      unused_bits = ( byte_len * 8 ) - bits;
  
      /*
       * Named bitstrings require that trailing 0s are excluded in the encoding
       * of the bitstring. Trailing 0s are considered part of the 'unused' bits
       * when encoding this value in the first content octet
       */
      if( bits != 0 )
      {
          cur_byte = buf + byte_len - 1;
          cur_byte_shifted = *cur_byte >> unused_bits;
  
          for( ; ; )
          {
              bit = cur_byte_shifted & 0x1;
              cur_byte_shifted >>= 1;
  
              if( bit != 0 )
                  break;
  
              bits--;
              if( bits == 0 )
                  break;
  
              if( bits % 8 == 0 )
                  cur_byte_shifted = *--cur_byte;
          }
      }
  
      return( mbedtls_asn1_write_bitstring( p, start, buf, bits ) );
  }
  
  int mbedtls_asn1_write_bitstring( unsigned char **p, unsigned char *start,
                            const unsigned char *buf, size_t bits )
  {
      int ret;
      size_t len = 0;
      size_t unused_bits, byte_len;
  
      byte_len = ( bits + 7 ) / 8;
      unused_bits = ( byte_len * 8 ) - bits;
  
      if( *p < start || (size_t)( *p - start ) < byte_len + 1 )
          return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
  
      len = byte_len + 1;
  
      /* Write the bitstring. Ensure the unused bits are zeroed */
      if( byte_len > 0 )
      {
          byte_len--;
          *--( *p ) = buf[byte_len] & ~( ( 0x1 << unused_bits ) - 1 );
          ( *p ) -= byte_len;
          memcpy( *p, buf, byte_len );
      }
  
      /* Write unused bits */
      *--( *p ) = (unsigned char)unused_bits;
  
      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_BIT_STRING ) );
  
      return( (int) len );
  }
  
  int mbedtls_asn1_write_octet_string( unsigned char **p, unsigned char *start,
                               const unsigned char *buf, size_t size )
  {
      int ret;
      size_t len = 0;
  
      MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start, buf, 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_OCTET_STRING ) );
  
      return( (int) len );
  }
  
  
  /* This is a copy of the ASN.1 parsing function mbedtls_asn1_find_named_data(),
   * which is replicated to avoid a dependency ASN1_WRITE_C on ASN1_PARSE_C. */
  static mbedtls_asn1_named_data *asn1_find_named_data(
                                                 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 );
  }
  
  mbedtls_asn1_named_data *mbedtls_asn1_store_named_data(
                                          mbedtls_asn1_named_data **head,
                                          const char *oid, size_t oid_len,
                                          const unsigned char *val,
                                          size_t val_len )
  {
      mbedtls_asn1_named_data *cur;
  
      if( ( cur = asn1_find_named_data( *head, oid, oid_len ) ) == NULL )
      {
          // Add new entry if not present yet based on OID
          //
          cur = (mbedtls_asn1_named_data*)mbedtls_calloc( 1,
                                              sizeof(mbedtls_asn1_named_data) );
          if( cur == NULL )
              return( NULL );
  
          cur->oid.len = oid_len;
          cur->oid.p = mbedtls_calloc( 1, oid_len );
          if( cur->oid.p == NULL )
          {
              mbedtls_free( cur );
              return( NULL );
          }
  
          memcpy( cur->oid.p, oid, oid_len );
  
          cur->val.len = val_len;
          cur->val.p = mbedtls_calloc( 1, val_len );
          if( cur->val.p == NULL )
          {
              mbedtls_free( cur->oid.p );
              mbedtls_free( cur );
              return( NULL );
          }
  
          cur->next = *head;
          *head = cur;
      }
      else if( cur->val.len < val_len )
      {
          /*
           * Enlarge existing value buffer if needed
           * Preserve old data until the allocation succeeded, to leave list in
           * a consistent state in case allocation fails.
           */
          void *p = mbedtls_calloc( 1, val_len );
          if( p == NULL )
              return( NULL );
  
          mbedtls_free( cur->val.p );
          cur->val.p = p;
          cur->val.len = val_len;
      }
  
      if( val != NULL )
          memcpy( cur->val.p, val, val_len );
  
      return( cur );
  }
  #endif /* MBEDTLS_ASN1_WRITE_C */
  