Rate limiting is an important technique to ensure the stability and security of web applications. In an ASP.NET application, rate limiting can be implemented in various ways. One approach is to use the ASP.NET Core Middleware pipeline to intercept incoming requests and check if they exceed a certain limit. If the limit is exceeded, the middleware can respond with an HTTP 429 status code indicating that the user has exceeded their rate limit. (more than usual requests to the server which is called a DoS attack)
Another approach (which is better than the previous one in my point of view) is to use a third-party library such as AspNetCoreRateLimit which provides a more advanced rate-limiting system with support for different rate-limiting algorithms, distributed caching, and client IP or identity-based rate limiting.
Note that It is so important to properly configure and tune the rate limiting system to ensure that it does not block legitimate traffic or cause unnecessary delays. Rate limiting can be an effective tool to prevent denial of service attacks, brute force attacks, and other malicious activities that can harm the web application or its users.
In order to implement via middleware, it could be a middleware like a bellow:
public class MyMiddleware
{
private readonly RequestDelegate _next;
public MyMiddleware(RequestDelegate next)
{
_next = next;
}
public async Task InvokeAsync(HttpContext context)
{
context.Response.Headers.Add("X-My-Custom-Header", "Hello, world!");
await _next(context);
}
}
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
app.UseMiddleware<MyMiddleware>();
}
In this example, we defined a custom middleware class MyMiddleware that adds a custom header to the HTTP response. The InvokeAsync method of the MyMiddleware class is called for each incoming request, and it passes the request to the next middleware in the pipeline using the await _next(context) statement. This allows other middleware components to handle the request before and after MyMiddleware has executed its logic.
And about the implementation via the mentioned library (AspNetCoreRateLimit):
// Register the AspNetCoreRateLimit middleware in the Startup.cs file
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
// ...
app.UseIpRateLimiting();
// ...
}
In this example, we're using the AspNetCoreRateLimit package to enable IP-based rate limiting for our application. We register the UseIpRateLimiting middleware in the Configure method of the Startup.cs file, which will automatically limit the number of requests that can be made to our application from a given IP address.
This middleware will intercept incoming requests and check if the IP address has exceeded its allowed request limit. If so, it will return a 429 "Too Many Requests" response. This helps to prevent overloading our application with too many requests from a single IP address. The AspNetCoreRateLimit package provides many other configuration options for rate limiting, including limiting based on other criteria such as HTTP headers or client ID. It's a powerful tool for controlling the flow of requests to our application and preventing it from becoming overloaded.
// Configure rate limiting options in the Startup.cs file
public void ConfigureServices(IServiceCollection services)
{
// ...
// Define the rate limiting options
var rateLimitOptions = new IpRateLimitOptions
{
GeneralRules = new List<RateLimitRule>
{
new RateLimitRule
{
Endpoint = "*",
Limit = 100,
Period = "1m"
},
new RateLimitRule
{
Endpoint = "*",
Limit = 1000,
Period = "1h"
}
},
// Define options for storing rate limit counters (e.g. in-memory or distributed cache)
// ...
};
// Register the rate limiting services and options
services.AddMemoryCache();
services.Configure<IpRateLimitOptions>(rateLimitOptions);
services.AddSingleton<IRateLimitCounterStore, MemoryCacheRateLimitCounterStore>();
services.AddSingleton<IIpPolicyStore, MemoryCacheIpPolicyStore>();
// ...
}
You can simply read the rateLimitOptions from appsetting as a config if you don’t like to be in ConfigureServices().