Kavita/API/Middleware/RateLimit/AuthenticationRateLimiterPolicy.cs

using System;
using System.Globalization;
using System.Threading;
using System.Threading.RateLimiting;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.RateLimiting;

namespace API.Middleware.RateLimit;

public class AuthenticationRateLimiterPolicy : IRateLimiterPolicy<string>
{
    public RateLimitPartition<string> GetPartition(HttpContext httpContext)
    {
        return RateLimitPartition.GetFixedWindowLimiter(httpContext.Request.Headers.Host.ToString(),
            partition => new FixedWindowRateLimiterOptions
            {
                AutoReplenishment = true,
                PermitLimit = 1,
                Window = TimeSpan.FromMinutes(10),
            });
    }

    public Func<OnRejectedContext, CancellationToken, ValueTask>? OnRejected { get; } =
        (context, _) =>
        {
            if (context.Lease.TryGetMetadata(MetadataName.RetryAfter, out var retryAfter))
            {
                context.HttpContext.Response.Headers.RetryAfter =
                    ((int) retryAfter.TotalSeconds).ToString(NumberFormatInfo.InvariantInfo);
            }

            context.HttpContext.Response.StatusCode = StatusCodes.Status429TooManyRequests;
            return new ValueTask();
        };
}