jellyfin/Jellyfin.Api/Middleware/BaseUrlRedirectionMiddleware.cs

using System;
using System.Threading.Tasks;
using MediaBrowser.Common.Net;
using MediaBrowser.Controller.Configuration;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;
using static MediaBrowser.Controller.Extensions.ConfigurationExtensions;

namespace Jellyfin.Api.Middleware;

/// <summary>
/// Redirect requests without baseurl prefix to the baseurl prefixed URL.
/// </summary>
public class BaseUrlRedirectionMiddleware
{
    private readonly RequestDelegate _next;
    private readonly ILogger<BaseUrlRedirectionMiddleware> _logger;
    private readonly IConfiguration _configuration;

    /// <summary>
    /// Initializes a new instance of the <see cref="BaseUrlRedirectionMiddleware"/> class.
    /// </summary>
    /// <param name="next">The next delegate in the pipeline.</param>
    /// <param name="logger">The logger.</param>
    /// <param name="configuration">The application configuration.</param>
    public BaseUrlRedirectionMiddleware(
        RequestDelegate next,
        ILogger<BaseUrlRedirectionMiddleware> logger,
        IConfiguration configuration)
    {
        _next = next;
        _logger = logger;
        _configuration = configuration;
    }

    /// <summary>
    /// Executes the middleware action.
    /// </summary>
    /// <param name="httpContext">The current HTTP context.</param>
    /// <param name="serverConfigurationManager">The server configuration manager.</param>
    /// <returns>The async task.</returns>
    public async Task Invoke(HttpContext httpContext, IServerConfigurationManager serverConfigurationManager)
    {
        var localPath = httpContext.Request.Path.ToString();
        var baseUrlPrefix = serverConfigurationManager.GetNetworkConfiguration().BaseUrl;

        if (string.IsNullOrEmpty(localPath)
            || string.Equals(localPath, baseUrlPrefix, StringComparison.OrdinalIgnoreCase)
            || string.Equals(localPath, baseUrlPrefix + "/", StringComparison.OrdinalIgnoreCase)
            || !localPath.StartsWith(baseUrlPrefix, StringComparison.OrdinalIgnoreCase)
           )
        {
            // Redirect health endpoint
            if (string.Equals(localPath, "/health", StringComparison.OrdinalIgnoreCase)
                || string.Equals(localPath, "/health/", StringComparison.OrdinalIgnoreCase))
            {
                _logger.LogDebug("Redirecting /health check");
                httpContext.Response.Redirect(baseUrlPrefix + "/health");
                return;
            }

            // Always redirect back to the default path if the base prefix is invalid or missing
            _logger.LogDebug("Normalizing an URL at {LocalPath}", localPath);

            var port = httpContext.Request.Host.Port ?? -1;
            var uri = new UriBuilder(httpContext.Request.Scheme, httpContext.Request.Host.Host, port, localPath).Uri;
            var redirectUri = new UriBuilder(httpContext.Request.Scheme, httpContext.Request.Host.Host, port, baseUrlPrefix + "/" + _configuration[DefaultRedirectKey]).Uri;
            var target = uri.MakeRelativeUri(redirectUri).ToString();
            _logger.LogDebug("Redirecting to {Target}", target);

            httpContext.Response.Redirect(target);
            return;
        }

        await _next(httpContext).ConfigureAwait(false);
    }
}