What is it?

A C# dotnet 8 implementation of the TUS-protocol for resumable file uploads for an ASP.NET Core application.

Why create another TUS library?
This library's purpose is to be simple and give the consumer more options on how to authorize and authenticate requests.
Which I felt that other libraries did not provide.
SolidTUS is a more Controller/Action oriented and integrates well with a Web API or an MVC project.

If you have any suggestions or improvements please do not hesitate to contribute.

Current TUS features

SolidTUS currently implements the following.

Basic features:

• Core-protocol v.1.0.0 (stop and resume uploads)
• Max-size (define a hard limit for upload size)
• Tus-metadata validation
• Options (server feature announcements)

Extensions:

• Creation
• Creation-With-Upload
• Expiration
• Concatenation
• Checksum *
• Termination **

Notes:
* Checksum feature does not implement the trailing header feature, i.e. A checksum value must be provided upon sending the http request.
** Termination must be implemented by yourself. See examples and documentation on how to and why.

Other:
The API is not stable, still trying to find an easy to use and understandable API - thus I might experiment and change usage.
Versioning does not follow semantic versioning.

Other TUS libraries for C#

• tusdotnet

Quickstart

Add the package to your project:

$ dotnet add package SolidTUS

Register the service in the startup process:

// Register TUS services
builder.Services.AddTUS();

Using MVC

In your Controller add the TusCreation-attribute to the action method endpoint.

Get upload info

[TusCreation("/upload/{myArg}")]
[Microsoft.AspNetCore.Mvc.RequestSizeLimit(5_000_000_000)]
public async Task<ActionResult> CreateFileInfo(string myArg)
{
    // Create a globally unique file id string
    var myFileId = Guid.NewGuid().ToString("N");

    // Read Metadata
    var metadata = HttpContext.TusInfo().TusMetadata();
    if (metadata is not null)
    {
        // The client (uploader) sets the metadata
        // so they may not exist
        var filename = metadata["filename"];
        var mime = metadata["contentType"];
        Console.WriteLine("Filename is: {0}\nMime-type is: {1}", filename, mime);
    }

    // Construct upload URL
    TusCreationContext ctx = HttpContext
        .TusCreation(myFileId)
        .Build("fileId", ("name", "World"));
        // Must provide the name of the file id parameter
        // and any additional parameters for the endpoint

    // Note if the request contains upload data in the body
    // This will start the upload - normally upload data is
    // done on TusUpload endpoint.
    await ctx.StartCreationAsync(HttpContext);

    // Converts a success to 201 created
    // With a Location header to the upload URL
    return Ok();
}

This will not upload any file (unless the client explicitly uses the TUS-extension Creation-With-Upload feature).
This only sets the ground work for getting information such as file size, and where to upload the data.

When building the TusCreationContext ctx the Build method must have the name of the parameter name for the file id. Any extra arguments should be in the tuple format ("parameterName", "value").

The upload URL is constructed using these values to set the Location header, furthermore, these values will be used when decoding Upload-Concat requests from the client.

The RequestSizeLimit is the actual allowed upload size when using Creation-With-Upload TUS-extension, which is different from the TusOptions.MaxSize. The TusOptions.MaxSize checks the Content-Length header if it is within the limit.

Next the upload

[TusUpload("{fileId}/hello/{name}")]
[RequestSizeLimit(5_000_000_000)]
public async Task<ActionResult> Upload(string fileId, string name)
{
    var ctx = HttpContext
        .TusUpload(fileId)
        .Build();
    await ctx.StartAppendDataAsync(HttpContext);

    // Must always return 204 on upload success with no Body content
    return NoContent();
}

And done...

Congratulations you now have a very basic upload / pause / resume functionality.

Using minimal API

Add an endpoint to your minimal api:

app.MapTusCreation("/upload/{myArg}", async (HttpContext context, string myArg) =>
{
    var myFileId = Guid.NewGuid().ToString("N");
    var create = context
        .TusCreation(myFileId)
        .Build("fileId", ("hello", "world"));

    await create.StartCreationAsync(context);

    // A success will be converted to 201
    // with a Location header pointing to the upload endpoint
    return Results.Ok();
});

Then define the upload endpoint:

app.MapTusUpload("/upload/{fileId}/{hello}", async (HttpContext http, string fileId, string hello) =>
{
    var upload = http
        .TusUpload(fileId)
        .Build();
    await upload.StartAppendDataAsync(http);
    return Results.NoContent();
});

Important: The fileId in the MapTusUpload method assumes that the 2nd parameter is fileId (index = 1).
To change it call the MapTusUpload method like so:

app.MapTusUpload("/upload/{fileId}/{hello}", async (string fileId, [FromServices] HttpContext http, string hello) =>
{
    // ... Omitted
}, fileIdIndex: 0);

Extra options

To see all the configurations go to the wiki.

Configurations

SolidTUS can be configured through the TusOptions object, either on startup or using environment variables.

// Custom metadata provider or set maximum TUS protocol file size
builder.Services
  .AddTUS(options =>
  {
    // This max size is different than the ASP.NET specified max size.
    // To change the request size limit do it per Action with an attribute (recommended).
    options.MaxSize = 5_000_000_000;
  })
  .SetMetadataValidator(metadata => metadata.ContainsKey("filename"))
  .AllowEmptyMetadata(true);

All options are mentioned in the wiki/tus-options
Note: to change request size limits see: Microsoft documentation

If you don't want to use the default FileUploadStorageHandler you can provide your own, maybe you want to save the files to a database?

// Add custom storage handler
builder.Services
  .AddTUS()
  .AddStorageHandler<MyStorageHandler>(); // <-- must implement IUploadStorageHandler interface

If you use the default FileUploadStorageHandler you can configure the directory where to store files:

// Add custom checksum validator
builder.Services
  .AddTUS()
  .FileStorageConfiguration(options =>
  {
    options.DirectoryPath = "path/to/where/save/upload/files";
  });

Context Builders

The context builders are meant to be used in conjunction with the Tus attributes. These context builders are created using extension methods on the HttpContext.

So that TusCreation extension method should be used with the TusCreation attribute, etc.

Each context builder uses a fluent interface to construct a tus context to be used in the library.

The attribute and their purpose

The TusCreation attribute is responsible for:

1. Creating new uploads, by creating the UploadFileInfo metadata resource
2. Merging finished partial uploads into a single file

The TusUpload attribute is responsible for:

1. Storing upload data from the client
2. Keeping the UploadFileInfo in-sync with upload

The TusDelete attribute is responsible for:

1. Terminating an upload
2. Must have the same endpoint route as TusUpload

Limitations

The library current limitations, are:

• Cannot specify where the UploadFileInfo metadata should be stored on a per upload basis.

This is due to the SolidTUS FileUploadMetaHandler only searching for metadata in a specific directory.

The TUS protocol with SolidTUS simplified

In essence the client sends a request to an endpoint as marked by the TusCreation attribute:

POST /files HTTP/1.1
Host: tus.example.org
Content-Length: 0
Upload-Length: 100
Tus-Resumable: 1.0.0

The server then knows to expect an upload file with a total size of 100 bytes and at which point SolidTUS creates an UploadFileInfo which contains this metadata.
The server responds on success where the file can be uploaded:

HTTP/1.1 201 Created
Location: https://tus.example.org/files/24e533e02ec3bc40c387f1a0e460e216
Tus-Resumable: 1.0.0

In this example the file has an ID of 24e533e02ec3bc40c387f1a0e460e216.
The client then uploads the data to that location as marked by the TusUpload attribute:

PATCH /files/24e533e02ec3bc40c387f1a0e460e216 HTTP/1.1
Host: tus.example.org
Content-Type: application/offset+octet-stream
Content-Length: 30
Upload-Offset: 70
Tus-Resumable: 1.0.0

[remaining 30 bytes]

After some while the upload starts from byte 70 and has a total size of 100, the missing 30 bytes are in the PATCH body. This data is directed to the OnPartialUploadAsync method in the IUploadStorageHandler.

When finished successfully the server responds:

HTTP/1.1 204 No Content
Tus-Resumable: 1.0.0
Upload-Offset: 100

Test methodology

Using unit tests and manually making TUS-request with the official javascript client in the examples folder.

TODO

• Create wiki pages for all the configuration options
• Create wiki pages for library design, and how to extend
• Add section in readme for examples
• Make the minimal API functional with OpenApi (Swagger)

References

• TUS-protocol