.Net Core 2.0 preview1实现自定义认证方案

public void ConfigureServices(IServiceCollection services)
{
　　services.AddAuthentication();
}

public void Configure(IApplicationBuilder app)
{
　　app.UseJwtBearerAuthentication(new JwtBearerOptions
　　{
　　Authority = Configuration["jwt:authority"],
　　Audience = Configuration["jwt:audience"],
　　Events = new JwtBearerEvents()
　　{
　　　　OnAuthenticationFailed = c =>
　　　　{
　　　　　　c.HandleResponse();
　　　　　　c.Response.StatusCode = 500;
　　　　　　c.Response.ContentType = "text/plain";
　　　　　　if (Environment.IsDevelopment())
　　　　　　{
　　　　　　　　return c.Response.WriteAsync(c.Exception.ToString());
　　　　　　}
　　　　　　return c.Response.WriteAsync("An error occurred processing your authentication.");
　　　　}　　
　　}
});

        public static IApplicationBuilder UseJwtBearerAuthentication(this IApplicationBuilder app, JwtBearerOptions options)
        {
            if (app == null)
            {
                throw new ArgumentNullException(nameof(app));
            }
            if (options == null)
            {
                throw new ArgumentNullException(nameof(options));
            }

            return app.UseMiddleware<JwtBearerMiddleware>(Options.Create(options));
        }

public void ConfigureServices(IServiceCollection services)
{
　　services.AddJwtBearerAuthentication(o =>
　　{
　　　　o.Authority = Configuration["jwt:authority"];
　　　　o.Audience = Configuration["jwt:audience"];
　　　　o.Events = new JwtBearerEvents()
　　　　{
　　　　　　OnAuthenticationFailed = c =>
　　　　　　{
              c.HandleResponse();
              c.Response.StatusCode = 500;
              c.Response.ContentType = "text/plain";
              if (Environment.IsDevelopment())
              {
                  return c.Response.WriteAsync(c.Exception.ToString());
              }
              return c.Response.WriteAsync("An error occurred processing your authentication.");
          }
       };
    });
}

public void Configure(IApplicationBuilder app)
{
    app.UseAuthentication();
}　　

public static IServiceCollection AddJwtBearerAuthentication(this IServiceCollection services, string authenticationScheme, Action<JwtBearerOptions> configureOptions)
{
    return services.AddScheme<JwtBearerOptions, JwtBearerHandler>(authenticationScheme, configureOptions);
}

public static IApplicationBuilder UseAuthentication(this IApplicationBuilder app)
{
　　if (app == null)
   {
   　　throw new ArgumentNullException(nameof(app));
   }         
   return app.UseMiddleware<AuthenticationMiddleware>();
}

namespace Microsoft.AspNetCore.Authentication
{
    public class AuthenticationMiddleware
    {
        private readonly RequestDelegate _next;

        public AuthenticationMiddleware(RequestDelegate next, IAuthenticationSchemeProvider schemes)
        {
            if (next == null)
            {
                throw new ArgumentNullException(nameof(next));
            }
            if (schemes == null)
            {
                throw new ArgumentNullException(nameof(schemes));
            }

            _next = next;
            Schemes = schemes;
        }

        public IAuthenticationSchemeProvider Schemes { get; set; }

        public async Task Invoke(HttpContext context)
        {
            context.Features.Set<IAuthenticationFeature>(new AuthenticationFeature
            {
                OriginalPath = context.Request.Path,
                OriginalPathBase = context.Request.PathBase
            });

            // REVIEW: alternatively could depend on a routing middleware to do this

            // Give any IAuthenticationRequestHandler schemes a chance to handle the request
            var handlers = context.RequestServices.GetRequiredService<IAuthenticationHandlerProvider>();
            foreach (var scheme in await Schemes.GetRequestHandlerSchemesAsync())
            {
                var handler = await handlers.GetHandlerAsync(context, scheme.Name) as IAuthenticationRequestHandler;
                if (handler != null && await handler.HandleRequestAsync())
                {
                    return;
                }
            }

            var defaultAuthenticate = await Schemes.GetDefaultAuthenticateSchemeAsync();
            if (defaultAuthenticate != null)
            {
                var result = await context.AuthenticateAsync(defaultAuthenticate.Name);
                if (result?.Principal != null)
                {
                    context.User = result.Principal;
                }
            }

            await _next(context);
        }
    }
}