ReadFormAsync continues reading after exception

[yshahin]

Describe the bug

ReadFormAsync keeps reading form data after exception thrown for invalid data.

To Reproduce

Send binary data file to api with content-type "application/x-www-form-urlencoded".
File must be large to see the problem, 10MB file will do it.
Since this is invalid data an exception System.IO.InvalidDataException is thrown.

System.IO.InvalidDataException
  HResult=0x80131501
  Message=Form key length limit 2048 exceeded.
  Source=Microsoft.AspNetCore.WebUtilities
  StackTrace:
   at Microsoft.AspNetCore.WebUtilities.FormPipeReader.ThrowKeyTooLargeException() in /_/src/Http/WebUtilities/src/FormPipeReader.cs:line 308

The using the code snippet below, the exception will be caught and and 400 sent back.

app.Use(async (context, next) =>
{
    try
    {
        // TODO: try-catch log unexpected errors
        await next.Invoke().ConfigureAwait(true);
    }
    catch (InvalidDataException dataEx)
    {
        context.Response.StatusCode = (int)HttpStatusCode.BadRequest;
        await context.Response.WriteAsync("BadRequest").ConfigureAwait(false);
    }
});

Since the data is large and ReadFormAsync doesn't stop reading, we get this exception System.InvalidOperationException: 'Reading is already in progress.'.

System.InvalidOperationException
  HResult=0x80131509
  Message=Reading is already in progress.
  Source=Microsoft.AspNetCore.Server.Kestrel.Core
  StackTrace:
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.Http1ContentLengthMessageBody.TryReadInternal(ReadResult& readResult) in /_/src/Servers/Kestrel/Core/src/Internal/Http/Http1ContentLengthMessageBody.cs:line 126

Further technical details

• ASP.NET Core version 3
• Include the output of dotnet --info
  .NET Core SDK (reflecting any global.json):
  Version: 3.1.100
  Commit: cd82f021f4
  Runtime Environment:
  OS Name: Windows
  OS Version: 10.0.18363
  OS Platform: Windows
  RID: win10-x64
  Base Path: C:\Program Files\dotnet\sdk\3.1.100
  Host (useful for support):
  Version: 3.1.0
  Commit: 65f04fb6db
  .NET Core SDKs installed:
  2.1.202 [C:\Program Files\dotnet\sdk]
  2.1.507 [C:\Program Files\dotnet\sdk]
  2.1.509 [C:\Program Files\dotnet\sdk]
  2.1.701 [C:\Program Files\dotnet\sdk]
  2.1.801 [C:\Program Files\dotnet\sdk]
  2.1.802 [C:\Program Files\dotnet\sdk]
  2.2.401 [C:\Program Files\dotnet\sdk]
  3.0.100 [C:\Program Files\dotnet\sdk]
  3.1.100 [C:\Program Files\dotnet\sdk]
  .NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.12 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.12 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.12 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
• The IDE (VS / VS Code/ VS4Mac) you're running on, and it's version
  Microsoft Visual Studio Enterprise 2019
  Version 16.3.8
  VisualStudio.16.Release/16.3.8+29503.13
  Microsoft .NET Framework
  Version 4.8.03752

[Tratcher]

Duplicate of #14727 which is already fixed in 3.1.

[Tratcher]

I see you're using the 3.1 SDK, but can you clarify that you're using the 3.0 runtime / target framework?

[yshahin]

@Tratcher I have 3.1 installed but I am using 3.0 for my project. I will test with 3.1 and reply back

[yshahin]

@Tratcher I tested on 3.1 and the problem is still there, it is not resolved.

[Tratcher]

@halter73 @jkotalik

[Tratcher]

@yshahin can you attach a Fiddler trace of the malformed request?

[halter73]

In this case, it looks like the bug is that FormPipeReader.ReadFormAsync doesn't call PipeReader.AdvanceTo() when ParseFormValues throws. The call to AdvanceTo should probably be moved to a finally.

https://github.com/aspnet/AspNetCore/blob/0792e9a4f56de47580c4490c27ca453934552246/src/Http/WebUtilities/src/FormPipeReader.cs#L85-L114

Kestrel doesn't try to put the pipe back into a readable state if middleware calls PipeReader.ReadAsync() without calling PipeReader.AdvanceTo() before exiting. The bug in 3.0 was in HttpRequestStream (i.e. HttpContext.Request.Body) itself.