You can automatically HTML encode field in custom Model Binder. My solution some different, I put error in ModelState and display error message near the field. It`s easy to modify this code for automatically encode
public class AppModelBinder : DefaultModelBinder
{
protected override object CreateModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Type modelType)
{
try
{
return base.CreateModel(controllerContext, bindingContext, modelType);
}
catch (HttpRequestValidationException e)
{
HandleHttpRequestValidationException(bindingContext, e);
return null; // Encode here
}
}
protected override object GetPropertyValue(ControllerContext controllerContext, ModelBindingContext bindingContext,
PropertyDescriptor propertyDescriptor, IModelBinder propertyBinder)
{
try
{
return base.GetPropertyValue(controllerContext, bindingContext, propertyDescriptor, propertyBinder);
}
catch (HttpRequestValidationException e)
{
HandleHttpRequestValidationException(bindingContext, e);
return null; // Encode here
}
}
protected void HandleHttpRequestValidationException(ModelBindingContext bindingContext, HttpRequestValidationException ex)
{
var valueProviderCollection = bindingContext.ValueProvider as ValueProviderCollection;
if (valueProviderCollection != null)
{
ValueProviderResult valueProviderResult = valueProviderCollection.GetValue(bindingContext.ModelName, skipValidation: true);
bindingContext.ModelState.SetModelValue(bindingContext.ModelName, valueProviderResult);
}
string errorMessage = string.Format(CultureInfo.CurrentCulture, "{0} contains invalid symbols: <, &",
bindingContext.ModelMetadata.DisplayName);
bindingContext.ModelState.AddModelError(bindingContext.ModelName, errorMessage);
}
}
In Application_Start:
ModelBinders.Binders.DefaultBinder = new AppModelBinder();
Note that it works only for form fields. Dangerous value not passed to controller model, but stored in ModelState and can be redisplayed on form with error message.
Dangerous chars in URL may be handled this way:
private void Application_Error(object sender, EventArgs e)
{
Exception exception = Server.GetLastError();
HttpContext httpContext = HttpContext.Current;
HttpException httpException = exception as HttpException;
if (httpException != null)
{
RouteData routeData = new RouteData();
routeData.Values.Add("controller", "Error");
var httpCode = httpException.GetHttpCode();
switch (httpCode)
{
case (int)HttpStatusCode.BadRequest /* 400 */:
if (httpException.Message.Contains("Request.Path"))
{
httpContext.Response.Clear();
RequestContext requestContext = new RequestContext(new HttpContextWrapper(Context), routeData);
requestContext.RouteData.Values["action"] ="InvalidUrl";
requestContext.RouteData.Values["controller"] ="Error";
IControllerFactory factory = ControllerBuilder.Current.GetControllerFactory();
IController controller = factory.CreateController(requestContext, "Error");
controller.Execute(requestContext);
httpContext.Server.ClearError();
Response.StatusCode = (int)HttpStatusCode.BadRequest /* 400 */;
}
break;
}
}
}
ErrorController:
public class ErrorController : Controller
{
public ActionResult InvalidUrl()
{
return View();
}
}
