aspnetcore 认证相关类简要说明三

今天我们再来了解一个很重要的接口IAuthenticationService的实现类AuthenticationService：

public class AuthenticationService : IAuthenticationService
{
        public AuthenticationService(IAuthenticationSchemeProvider schemes, IAuthenticationHandlerProvider handlers, IClaimsTransformation transform)
        {
            Schemes = schemes;
            Handlers = handlers;
            Transform = transform;
        }

        public IAuthenticationSchemeProvider Schemes { get; }
        public IAuthenticationHandlerProvider Handlers { get; }
        public IClaimsTransformation Transform { get; }

        public virtual async Task<AuthenticateResult> AuthenticateAsync(HttpContext context, string scheme)
        {
            if (scheme == null)
            {
                var defaultScheme = await Schemes.GetDefaultAuthenticateSchemeAsync();
                scheme = defaultScheme?.Name;
                if (scheme == null)
                {
                    throw new InvalidOperationException($"No authenticationScheme was specified, and there was no DefaultAuthenticateScheme found.");
                }
            }

            var handler = await Handlers.GetHandlerAsync(context, scheme);
            if (handler == null)
            {
                throw await CreateMissingHandlerException(scheme);
            }

            var result = await handler.AuthenticateAsync();
            if (result != null && result.Succeeded)
            {
                var transformed = await Transform.TransformAsync(result.Principal);
                return AuthenticateResult.Success(new AuthenticationTicket(transformed, result.Properties, result.Ticket.AuthenticationScheme));
            }
            return result;
        }

        /// <summary>
        /// Challenge the specified authentication scheme.
        /// </summary>
        /// <param name="context">The <see cref="HttpContext"/>.</param>
        /// <param name="scheme">The name of the authentication scheme.</param>
        /// <param name="properties">The <see cref="AuthenticationProperties"/>.</param>
        /// <returns>A task.</returns>
        public virtual async Task ChallengeAsync(HttpContext context, string scheme, AuthenticationProperties properties)
        {
            if (scheme == null)
            {
                var defaultChallengeScheme = await Schemes.GetDefaultChallengeSchemeAsync();
                scheme = defaultChallengeScheme?.Name;
                if (scheme == null)
                {
                    throw new InvalidOperationException($"No authenticationScheme was specified, and there was no DefaultChallengeScheme found.");
                }
            }

            var handler = await Handlers.GetHandlerAsync(context, scheme);
            if (handler == null)
            {
                throw await CreateMissingHandlerException(scheme);
            }

            await handler.ChallengeAsync(properties);
        }

        /// <summary>
        /// Forbid the specified authentication scheme.
        /// </summary>
        public virtual async Task ForbidAsync(HttpContext context, string scheme, AuthenticationProperties properties)
        {
            if (scheme == null)
            {
                var defaultForbidScheme = await Schemes.GetDefaultForbidSchemeAsync();
                scheme = defaultForbidScheme?.Name;
                ...
            }

            var handler = await Handlers.GetHandlerAsync(context, scheme);
　　　　　　　...await handler.ForbidAsync(properties);
        }

        /// <summary>
        /// Sign a principal in for the specified authentication scheme.
        /// </summary>
        public virtual async Task SignInAsync(HttpContext context, string scheme, ClaimsPrincipal principal, AuthenticationProperties properties)
        {
　　　　　　　...
　　　　　　　if (scheme == null)
            {
                var defaultScheme = await Schemes.GetDefaultSignInSchemeAsync();
                scheme = defaultScheme?.Name;
                ...
            }

            var handler = await Handlers.GetHandlerAsync(context, scheme);
            ...
　　　　　　　var signInHandler = handler as IAuthenticationSignInHandler;
            ...
　　　　　　　await signInHandler.SignInAsync(principal, properties);
        }

        /// <summary>
        /// Sign out the specified authentication scheme.
        /// </summary>
        public virtual async Task SignOutAsync(HttpContext context, string scheme, AuthenticationProperties properties)
        {
            if (scheme == null)
            {
                var defaultScheme = await Schemes.GetDefaultSignOutSchemeAsync();
                scheme = defaultScheme?.Name;
                if (scheme == null)
                {
                    throw new InvalidOperationException($"No authenticationScheme was specified, and there was no DefaultSignOutScheme found.");
                }
            }

            var handler = await Handlers.GetHandlerAsync(context, scheme);
            if (handler == null)
            {
                throw await CreateMissingSignOutHandlerException(scheme);
            }

            var signOutHandler = handler as IAuthenticationSignOutHandler;
            if (signOutHandler == null)
            {
                throw await CreateMismatchedSignOutHandlerException(scheme, handler);
            }

            await signOutHandler.SignOutAsync(properties);
        }
}

该类通过构造方法，将我们前两篇中讲到了IAuthenticationSchemeProvider和IAuthenticationHandlerProvider注入了进来，第三个参数不是很重要就飘过了。接下来我们看看它的这几个方法AuthenticateAsync、ChallengeAsync、ForbidAsync、SignInAsync和SignOutAsync等方法，他们的套路几乎都一样的，通过注入进来的两个接口的实例，最终获得到IAuthenticationHandler接口实例，并调用同名方法。

关于IAuthenticationService、IAuthenticationHandlerProvider和IAuthenticationSchemeProvider我们又是什么时候注入到服务容器里去的呢？它是在AuthenticationCoreServiceCollectionExtensions这个静态类中的AddAuthenticationCore扩展方法注入到容器中的，还有AuthenticationOptions也是在这里注入到依赖注入系统的容器中的：

    public static class AuthenticationCoreServiceCollectionExtensions
    {
        public static IServiceCollection AddAuthenticationCore(this IServiceCollection services)
        {
　　　　　　　...
            services.TryAddScoped<IAuthenticationService, AuthenticationService>();
            services.TryAddSingleton<IClaimsTransformation, NoopClaimsTransformation>(); // Can be replaced with scoped ones that use DbContext
            services.TryAddScoped<IAuthenticationHandlerProvider, AuthenticationHandlerProvider>();
            services.TryAddSingleton<IAuthenticationSchemeProvider, AuthenticationSchemeProvider>();
            return services;
        }

        public static IServiceCollection AddAuthenticationCore(this IServiceCollection services, Action<AuthenticationOptions> configureOptions) {
            ...
            services.AddAuthenticationCore();
            services.Configure(configureOptions);
            return services;
        }
    }

该扩展方法是在Startup的ConfigureServices方法调用的。这个就不贴代码了。

注入完以后呢？怎么使用呢？为了方便使用，aspnetcore为我们在外面又裹了一层，那就是AuthenticationHttpContextExtensions为HttpContext添加的扩展方法。我们可以在Controller如下调用：

public class HomeController : Controller
{
        public IActionResult Index()
        {
            var result = HttpContext.AuthenticateAsync();
            return View(result.Result);
        }
}

至此认证相关的核心元素介绍完成，本篇到此结束。