ASP.NET WEBAPI 的身份验证和授权

定义

身份验证（Authentication）：确定用户是谁。

授权(Authorization)：确定用户能做什么，不能做什么。

身份验证

WebApi 假定身份验证发生在宿主程序称中。对于 web-hosting，宿主是 IIS。这种情况下使用 HTTP Module 进行验证。

验证时，宿主会创建一个表示安全上下文的主体对象（实现 IPrincipal），将它附加到当前线程。主体对象包含一个存储用户信息的 Identity 对象。若验证成功，Identity.IsAuthenticated 属性将返回 true。

HTTP 消息处理程序（HTTP Message Handler）

可以用 HTTP 消息处理程序代替宿主进行身份验证。这种情况下，由 HTTP 消息处理程序检查请求并设置主体对象。

请考虑以下事项决定是否使用消息处理程序进行身份验证：

HTTP 模块检查所有经过 asp.net 管道的请求，消息处理程序只检查路由到 WebAPI的请求。
可以为每个路由单独设置消息处理程序。
HTTP 模块仅在 IIS 中可用。消息处理程序则与宿主无关，在 web-hosting 和 self-hosting 中均可用。
HTTP 模块参与IIS 日志和审计等功能。
HTTP模块在管道之前运行，主体在消息处理程序运行之前不会设置，当响应离开消息处理程序时，主体会恢复成原来的那个。

一般来说，不需要自承载时，HTTP 模块较好。

设置主体

进行自定义身份验证时，应在两个地方设置主体对象：

Thread.CurrentPrincipal，这是 .net 中设置线程主体的标准方式。
HttpContext.Current.User 这是特定于 ASP.NET 的属性。

private void SetPrincipal(IPrincipal principal)

{

    Thread.CurrentPrincipal = principal;

    if (HttpContext.Current != null)

    {

        HttpContext.Current.User = principal;

    }

}

采用 web-hosting 时，必须同时设置两处，避免安全上下文不一致。对于 self-hosting，HttpContext.Current 为 null，所以设置之前应进行检查。

授权

授权发生在管道中更接近 controller 的位置。

授权筛选器（Authorization filter）在 action 之前运行。若请求未授权，返回错误，action 不运行。
在 action 内部，可以用 ApiController.User 属性获取主体对象，做进一步的控制。

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" 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[Authorize] 属性

AuthorizeAttribute 是内置的授权筛选器。用户未通过身份验证时，它返回 HTTP 401 状态码。可以在全局，控制和 action 三个级别应用它。

在全局级别应用：

public static void Register(HttpConfiguration config)

{

    config.Filters.Add(new AuthorizeAttribute());

}

在控制器级别应用：

[Authorize]

public class ValuesController : ApiController

{

    public HttpResponseMessage Get(int id) { ... }

    public HttpResponseMessage Post() { ... }

}

在 Action 级别应用：

public class ValuesController : ApiController

{

    public HttpResponseMessage Get() { ... }

    [Authorize]

    public HttpResponseMessage Post() { ... }

}

在控制器上应用 [Authorize] 时，可以在 Action 上应用 [AllowAnonymous] 取消对某个 Action 的授权要求。上面的代码可以改成下面的形式：

[Authorize]

public class ValuesController : ApiController

{

    [AllowAnonymous]

    public HttpResponseMessage Get() { ... }

    public HttpResponseMessage Post() { ... }

}

指定用户和角色进行限制：

// 按用户限制访问

[Authorize(Users="Alice,Bob")]

public class ValuesController : ApiController

{

}

// 按角色限制访问

[Authorize(Roles="Administrators")]

public class ValuesController : ApiController

{

}

用于 WebAPI 的 AuthorizeAttribute 位于 System.Web.Http 命名空间。在 System.Web.Mvc 命名空间中有一个同名属性，不可用于 WebAPI。

自定义授权筛选器

可从以下类型派生自定义授权筛选器

AuthorizeAttribute，基于用户和角色进行授权。
AuthorizationFilterAttribute，不基于用户和角色的同步授权。
IAuthorizationFilter，实现此接口执行异步授权逻辑。例如，授权逻辑中有对 IO 或网络的异步调用。（CPU-bound的授权逻辑更适合从 AuthorizationFilterAttribute 派生，这样不必写异步方法）。

下图是 AuthorizeAttribute 类层次

aaarticlea/png;base64,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" alt="" />

在 Action 中执行验证

可在控制器中检查 ApiController.User 属性，根据用户和角色使用不同的逻辑。

public HttpResponseMessage Get()

{

    if (User.IsInRole("Administrators"))

    {

        // ...

    }

}

原文地址：http://www.asp.net/web-api/overview/security/authentication-and-authorization-in-aspnet-web-api