RequestSizeLimitAttribute: HTTP 500 instead of 413 in ASP.NET Core 2.1.401

Question

I have [RequestSizeLimit] on my API controller, and it kinda works as expected: requests bigger than specified limit are rejected.

    [HttpPut]
    [RequestSizeLimit(120_000_000)]
    public async Task<IActionResult> Put(IFormCollection form)
    {
       ...
    }

The problem is, an exception is thrown:

Microsoft.AspNetCore.Server.Kestrel.Core.BadHttpRequestException: Request body too large.
   at Microsoft.AspNetCore.Server.Kestrel.Core.BadHttpRequestException.Throw(RequestRejectionReason reason)
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.Http1MessageBody.ForContentLength.OnReadStarting()
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.MessageBody.TryInit()
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.MessageBody.ReadAsync(Memory`1 buffer, CancellationToken cancellationToken)
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpRequestStream.ReadAsyncInternal(Memory`1 buffer, CancellationToken cancellationToken)

So HTTP 500 is returned, but I would expect 413 or 400. And I don't expect an exception, since this is a perfectly normal situation.

Could not find any documentation on this. What is the right way to return 413 for requests that are too big?

Answer 1

Kestrel responds with a 413 Payload Too Large response, but HttpSys responds with a generic 500 Internal Server Error response. I assume you use the second one. In this case you can implement Exception handling middelware to handle this case:

public class ExceptionMiddleware
{
    private readonly RequestDelegate _next;

    public ExceptionMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task InvokeAsync(HttpContext httpContext)
    {
        try
        {
            await _next(httpContext);
        }
        catch (Exception ex)
        {
            HandleExceptionAsync(httpContext, ex);
        }
    }

    private static void HandleExceptionAsync(HttpContext context, Exception exception)
    {
        if (exception is BadHttpRequestException badRequestException && badRequestException.Message == "Request body too large.")
        {
            context.Response.StatusCode = (int) HttpStatusCode.RequestEntityTooLarge;
        }
    }
}

And register it in Configure in Startup.cs:

public void Configure(IApplicationBuilder app)
{
    ...
    app.UseMiddleware<ExceptionMiddleware>();
    ...
}

As alternative you can also use Exception filter