About

MagicNumbers is a .NET library for file binary header validation against file extension. This package determines if the received file has the original extension or if it has been changed, by matching binary header data for every extension provided by MagicNumbers wiki.

Package name	Description	.NET	NuGet
File.Validator	Base file validator for regular use
File.Validator.Web	.NET Core REST API Middleware and annotations for MVC controllers

Getting started

Base Package

dotnet add package File.Validator --version 1.0.0

.NET MVC

dotnet add package File.Validator.Web --version 1.0.0

Usage

Base package

Using isValidExtension from the FileValidator class required File.Validator package. By providing the binary stream, and expected extension, you can determine whether file data matches, that extension.

var extension = "exe";
var stream = new MemoryStream();

bool isValid = FileValidator.isValidExtension(stream, extension);

MVC REST API

File.Validator.Web provides one additional middleware for automatic file validation before request finalization. IApplicationBuilder interface extension from FileExtensionValidatorMiddlewareExtension should be used to register the middleware with UseFileValidation.

Note

To use annotations, middleware should be registered after endpoing routing middleware.

// Program.cs
app.UseRouting();
app.UseFileValidation();

Using controller annotations requires File.Validator.Web.Annotations.

Annotation	Description	Parameter
AllowedOnlyExtensions	If extension NOT IN list, expect unauthorized. (still do validation)	string[]
IgnoredExtensions	If extension in list, skip file validation	string[]
RejectedExtensions	If extension IN list, expect unauthorized. (Do not do validation)	string[]

[AllowedOnlyExtensions(new string[] {"pdf"})]
public IActionResult Index(IFormFile formFile)
{
    return View();
}