07_01_2009.c

static int checkEncapsulate( FILE *inFile, const int length ) {   
      ASN1_ITEM nestedItem;
      const int currentPos = fPos;
      int diffPos;
      
      /* If we're not looking for encapsulated objects, return */
      if( !checkEncaps )
          return( FALSE );
      
      /* Read the details of the next item in the input stream */
      getItem( inFile, &nestedItem );
      diffPos = fPos - currentPos;
      fPos = currentPos;
      fseek( inFile, -diffPos, SEEK_CUR );
      
      /* If it's not a standard tag class, don't try and dig down into it */
      if( ( nestedItem.id & CLASS_MASK ) != UNIVERSAL && \
              ( nestedItem.id & CLASS_MASK ) != CONTEXT )
          return( FALSE );
      
      /* If it doesn't fit exactly within the current item it's not an-
         encapsulated object */
      if( nestedItem.length != length - diffPos )
          return( FALSE );
      
      /* If it doesn't have a valid-looking tag, don't try and go any further */
      if( nestedItem.tag <= 0 || nestedItem.tag > 0x31 )
          return( FALSE );
      
      /* Now things get a bit complicated because it's possible to get some-
         (very rare) false positives, for example if a NUMERICSTRING of
         exactly the right length is nested within an OCTET STRING, since-
         numeric values all look like constructed tags of some kind.  To-
         handle this we look for nested constructed items that should really
         be primitive */
      if( ( nestedItem.id & FORM_MASK ) == PRIMITIVE )
          return( TRUE );
      
      /* It's constructed, make sure that it's something for which it makes
         sense as a constructed object.  At worst this will give some false
         negatives for really wierd objects (nested constructed strings inside
         OCTET STRINGs), but these should probably never occur anyway */
      if( nestedItem.tag == SEQUENCE || \
              nestedItem.tag == SET )
          return( TRUE );
      
      return( FALSE );
}

22_02_2003.c

static int checkEncapsulate( FILE *inFile, const int tag, const int length )
{
    ASN1_ITEM nestedItem;
    const int currentPos = fPos;
    int diffPos;

    /* If we're not looking for encapsulated objects, return */
    if( !checkEncaps )
        return( FALSE );

    /* Read the details of the next item in the input stream */
    getItem( inFile, &nestedItem );
    diffPos = fPos - currentPos;
    fPos = currentPos;
    fseek( inFile, -diffPos, SEEK_CUR );

    /* If it fits exactly within the current item and has a valid-looking
       tag, treat it as nested data */
    if( ( ( nestedItem.id & CLASS_MASK ) == UNIVERSAL || \
                ( nestedItem.id & CLASS_MASK ) == CONTEXT ) && \
            ( nestedItem.tag > 0 && nestedItem.tag <= 0x31 ) && \
            nestedItem.length == length - diffPos )
        return( TRUE );

    return( FALSE );
}