aspnetcore: Creating a System.IO.Compression.ZipArchive from FileMultipartSection.FileStream yields in errors.

Describe the bug

When you have a FileMultipartSection taken from a HttpContext.Request object that contains multipart/form-data content and contains valid file disposition, when you decide to create a ZipArchive out of the “FileStream” object, you get the following exception:

The Position must be positive. (Parameter 'value')
Actual value was -10.

In reality, I’m aware that the FileStream property to FileMultipartSection is not really a FileStream, but a MultipartReaderStream, still - it seems really confusing for this not to work.

If this is not a bug, could someone expand on exactly what’s going on here which leads to the above error?

Further technical details

ASP.NET Core version - .NET 5
Include the output of dotnet --info:

.NET SDK (reflecting any global.json):
 Version:   5.0.200-preview.20601.7
 Commit:    b3b934bbf2

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.19042
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\5.0.200-preview.20601.7\

Host (useful for support):
  Version: 5.0.5
  Commit:  2f740adc14

.NET SDKs installed:
  3.1.114 [C:\Program Files\dotnet\sdk]
  3.1.200-preview-015002 [C:\Program Files\dotnet\sdk]
  3.1.201 [C:\Program Files\dotnet\sdk]
  3.1.300-preview-015135 [C:\Program Files\dotnet\sdk]
  5.0.104 [C:\Program Files\dotnet\sdk]
  5.0.200-preview.20601.7 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.All 2.1.23 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.27 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.23 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.27 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.3 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.14 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.1.23 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.27 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.3 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.14 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.1.3 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.9 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.14 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.5 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

To install additional .NET runtimes or SDKs:
  https://aka.ms/dotnet-download

About this issue

Original URL
State: closed
Created 3 years ago
Comments: 16 (8 by maintainers)

Most upvoted comments

I’d be curious to see how one would be able to monitor these kinds of things. On a side-note: Is there an option of changing the default memory buffer of an IFormFile? The default is 32 kb.

You can configure FormOptions in ConfigureServices.

services.Configure<FormOptions>(o =>
{
     // Configure some defaults here                
});

@Tratcher the defaults for this type are poorly documented 😞

davidfowl on Apr 27, 2021

It’s likely related to https://github.com/dotnet/aspnetcore/issues/31753. When buffering is enabled the stream is seekable, but it’s not fully buffered yet and the length isn’t accurate.

Mitigations:

Fully buffer the stream first fileSection.FileStream.DrainAsync(); fileSection.FileStream.Position = 0;
Disable buffering.
Use Request.ReadFormAsync(), it pre-buffers the form parts separately. If you’re buffering anyways then this API seems easier to use.

Tratcher on Apr 24, 2021