Potential buffer overflow with bson_object_to_string

[jacobkeeler]

Created from smartdevicelink/sdl_core#3887

if string len >512 docString overflow

char *bson_object_to_string(BsonObject *obj, char *out) {
  //TODO just move the pointer rather than keep a position variable
  int position = 0;
  MapIterator iterator = emhashmap_iterator(&obj->data);
  MapEntry *current = emhashmap_iterator_next(&iterator);
  position += sprintf(out, "{ ");
  while (current != NULL) {
    BsonElement *element = (BsonElement *)current->value;
    position += sprintf(&out[position], "\"%s\":", current->key);
    switch (element->type) {
      case TYPE_DOCUMENT: {
        // docString overflow
        char docString[512];
        position += sprintf(&out[position], "%s", bson_object_to_string(bson_object_get_object(obj, current->key), docString));
        break;
      }

A length will need to be provided in this method in order to make sure that the buffer does not overflow.