Kestrel settings are not applied if configure KestrelServerOptions in appsettings.json file

[mm-ryo]

I am unable to configure KestrelServerOptions in appsettings.json file.
I tested the below settings, it doesn't work. it still takes default value (30,000,000 bytes => 28.6MB).
-- MaxRequestBodySize
-- MaxRequestHeaderCount

{
  "Kestrel": {
    "Limits": {
      "MaxRequestBodySize": 3000000,
      "MaxRequestHeaderCount": 10
    },
    "EndPoints": {
      "Http": {
        "Url": "http://*:10110"
      }
    }
  }
}

if I do it in C# code, it works.

services.Configure<FormOptions>(opt =>
{
    opt.MultipartBodyLengthLimit = 3000000;
});

services.Configure<KestrelServerOptions>(opt =>
{
    opt.Limits.MaxRequestBodySize = 3000000;
});

Further technical details

• ASP.NET Core version: 5.0
• The IDE (VS / VS Code/ VS4Mac) you're running on, and its version: vs2019 v16.11.4
• Include the output of dotnet --info:

dotnet --info Output

.NET SDK (reflecting any global.json):
 Version:   6.0.100-rc.1.21463.6
 Commit:    e627d556a1

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.19041
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\6.0.100-rc.1.21463.6\

Host (useful for support):
  Version: 6.0.0-rc.1.21451.13
  Commit:  d7619cd4b1

.NET SDKs installed:
  1.1.14 [C:\Program Files\dotnet\sdk]
  2.1.526 [C:\Program Files\dotnet\sdk]
  2.1.818 [C:\Program Files\dotnet\sdk]
  2.2.402 [C:\Program Files\dotnet\sdk]
  3.1.118 [C:\Program Files\dotnet\sdk]
  5.0.100 [C:\Program Files\dotnet\sdk]
  5.0.102 [C:\Program Files\dotnet\sdk]
  5.0.104 [C:\Program Files\dotnet\sdk]
  5.0.301 [C:\Program Files\dotnet\sdk]
  5.0.303 [C:\Program Files\dotnet\sdk]
  5.0.401 [C:\Program Files\dotnet\sdk]
  6.0.100-rc.1.21463.6 [C:\Program Files\dotnet\sdk]

[Tratcher]

MultipartBodyLengthLimit is a different limit than you've set in config. Which exception do you get during a request?

[mm-ryo]

MultipartBodyLengthLimit is a different limit than you've set in config. Which exception do you get during a request?

if the upload file size exceeds the limitation it throws BadHttpRequestException.
I am also unable to catch this exception in my ExceptionMiddleware.
BadHttpRequestException: Request body too large.

[Tratcher]

This is a known limitation of Kestrel's config integration, it only supports Endpoints, not other options. To read options you need to add this:

        services.Configure<KestrelServerOptions>(
            Configuration.GetSection("Kestrel"));

https://docs.microsoft.com/en-us/aspnet/core/fundamentals/servers/kestrel/options?view=aspnetcore-5.0

[Tratcher]

Duplicate of #4765

[mm-ryo]

Hi @Tratcher,
Where can I handle BadHttpRequestException?
we already have an exception middleware to handle exceptions that throw out from requests.
but it never steps into it if throws BadHttpRequestException.

[Tratcher]

Then where do you see the BadHttpRequestException?

[mm-ryo]

Then where do you see the BadHttpRequestException?

I saw it in my "ValidateModelFilter : IActionFilter" and in Browser i saw this (see below img)

[Tratcher]

Model binding has an opportunity to catch and handle request body exceptions.

A connection reset is expected when the request body size limits are exceeded, disconnecting the client is the only mitigation for a potential DOS attack.