HttpModule实现用户身份验证

(本文资源全部来自于园子里各牛)

之前看jimmyzhang的asp.net运行原理,开篇既说要明白验证就要先看asp.net运行原理,不然用控件就是"微软的用户"了

现在看到这总算反应过来,原来验证是在HttpModule里进行的(目前观点).

首先来看一下HttpModule的生命周期

为了证明这个图,来看一下下面这段代码.

 

public class ValidaterHttpModule : IHttpModule
{
    public void Dispose() { }

    public void Init(HttpApplication application)
    {
        application.BeginRequest += new EventHandler(application_BeginRequest);
        application.EndRequest += new EventHandler(application_EndRequest);
        application.PreRequestHandlerExecute += new EventHandler(application_PreRequestHandlerExecute);
        application.PostRequestHandlerExecute += new EventHandler(application_PostRequestHandlerExecute);
        application.ReleaseRequestState += new EventHandler(application_ReleaseRequestState);
        application.AcquireRequestState += new EventHandler(application_AcquireRequestState);
        application.AuthenticateRequest += new EventHandler(application_AuthenticateRequest);
        application.AuthorizeRequest += new EventHandler(application_AuthorizeRequest);
        application.ResolveRequestCache += new EventHandler(application_ResolveRequestCache);
        application.PreSendRequestHeaders += new EventHandler(application_PreSendRequestHeaders);
        application.PreSendRequestContent += new EventHandler(application_PreSendRequestContent);
    }
    void application_PreSendRequestContent(object sender, EventArgs e)
    {
        HttpApplication application = (HttpApplication)sender;
        application.Context.Response.Write("application_PreSendRequestContent<br/>");
    }
    void application_PreSendRequestHeaders(object sender, EventArgs e)
    {
        HttpApplication application = (HttpApplication)sender;
        application.Context.Response.Write("application_PreSendRequestHeaders<br/>");
    }
    void application_ResolveRequestCache(object sender, EventArgs e)
    {
        HttpApplication application = (HttpApplication)sender;
        application.Context.Response.Write("application_ResolveRequestCache<br/>");
    }
    void application_AuthorizeRequest(object sender, EventArgs e)
        {
            HttpApplication application = (HttpApplication)sender;
            application.Context.Response.Write("application_AuthorizeRequest<br/>");
        }
    void application_AuthenticateRequest(object sender, EventArgs e)
    {
        HttpApplication application = (HttpApplication)sender;
        application.Context.Response.Write("application_AuthenticateRequest<br/>");
    }
    void application_AcquireRequestState(object sender, EventArgs e)
    {
        HttpApplication application = (HttpApplication)sender;
        application.Context.Response.Write("application_AcquireRequestState<br/>");
    }
    void application_ReleaseRequestState(object sender, EventArgs e)
    {
        HttpApplication application = (HttpApplication)sender;
        application.Context.Response.Write("application_ReleaseRequestState<br/>");
    }
    void application_PostRequestHandlerExecute(object sender, EventArgs e)
    {
        HttpApplication application = (HttpApplication)sender;
        application.Context.Response.Write("application_PostRequestHandlerExecute<br/>");
    }
    void application_PreRequestHandlerExecute(object sender, EventArgs e)
    {
        HttpApplication application = (HttpApplication)sender;
        application.Context.Response.Write("application_PreRequestHandlerExecute<br/>");
    }

    void application_EndRequest(object sender, EventArgs e)
    {
        HttpApplication application = (HttpApplication)sender;
        application.Context.Response.Write("application_EndRequest<br/>");
    }
    void application_BeginRequest(object sender, EventArgs e)
    {
        HttpApplication application = (HttpApplication)sender;
        application.Context.Response.Write("application_BeginRequest<br/>");

    }
}

 

实现了IHttpModule接口.

运行如下:application_BeginRequest
application_AuthenticateRequest
application_AuthorizeRequest
application_ResolveRequestCache
application_AcquireRequestState
application_PreRequestHandlerExecute

application_PostRequestHandlerExecute
application_ReleaseRequestState
application_EndRequest
application_PreSendRequestHeaders

看来确实是如此.

下面就是实现用户验证的简单例子

 

public class UserAuthorizationModule : IHttpModule
{
    public void Dispose(){ }

    public void Init(HttpApplication context)
    {
        context.AcquireRequestState += new EventHandler(context_AcquireRequestState);
    }

    void context_AcquireRequestState(object sender, EventArgs e)
    {
        // 获取应用程序
        HttpApplication application = (HttpApplication)sender;

        // 检查用户是否已经登录
        if (application.Context.Session["UserName"] == null || application.Context.Session["UserName"].ToString().Trim() == "")
        {
            // 获取Url
            string requestUrl = application.Request.Url.ToString();
            string requestPage = requestUrl.Substring(requestUrl.LastIndexOf('/') + 1);
            // 如果请求的页面不是登录页面，刚重定向到登录页面。
            if (requestPage != "Login.aspx")
                application.Server.Transfer("Login.aspx");
        }
        else
        {
            // 已经登录，向每个请求的页面打印欢迎词。
            application.Response.Write(string.Format("欢迎您！{0}！", application.Context.Session["UserName"]));
        }
   }
}

 

 

  public class SystemModuleAuthorizationModule : IHttpModule

    {
        public void Dispose() { }

        public void Init(HttpApplication context)
        {
            context.AcquireRequestState += new EventHandler(context_AcquireRequestState);
        }
 
        void context_AcquireRequestState(object sender, EventArgs e)
        {
            HttpApplication application = (HttpApplication)sender;

            // 如果用户未登录，则无需检查模块授权，因为请求会被用户登录Module重定向到登录页面。
            if (application.Session["UserName"] == null)
                return;

            // 获取用户名和Url
            string userName = application.Session["UserName"].ToString();
            string url = application.Request.Url.ToString();
 
            // 如果用户没有被授权，请求被终止，并打印提示信息。
            if (!Validator.CanUseModule(userName, url))
            {
                application.CompleteRequest();
                application.Response.Write(string.Format("对不起！{0}，您无权访问此模块！", userName));
            }
        }
    }

    public class Validator
    {
        public static bool CanUseModule(string userName, string url)
        {
            if (!url.Contains("模块"))
                return true;
            else if (userName == "文野" && url.Contains("模块1"))
                return true;
            else if (userName == "stwyhm" && url.Contains("模块2"))
                return true;
            else
                return false;
        }
    }

 

在webconfig注册完成后,就可以运行看看效果了(页面上的关于session代码肯定再熟悉不过了).

 这里两个自定义的HttpModule实现了它们各自所要达到的过滤请求的功能，一个限制用户登录，一个限制模块访问，当然实际应用中比这要复杂许多。这样的验证方式是简单的、安全的，代码在修改时只要修改相应的HttpModule就可以了，无需在每个页面都写相同的验证代码，也不会发生在Url地址栏里输入一段Url就可以跳过登录及其它验证的情况了。在这两个HttpModule中，因为都要涉及到对Session的访问，所有都使用了AcquireRequestState事件

 

一个完整的HTTP请求在ASP.NET Framework的处理过程如下：

HttpRequest ——> inetinfo.exe ——> ASPNET_ISAPI.dll ——> Http Pipeline ——> ASPNET_WP.exe ——> HttpRuntime ——> HttpApplication Factory  ——> HttpApplication  ——> HttpModule ——> HttpHandler Factory  ——> HttpHandler  ——> HttpHandler.ProcessRequest()

HTTP Handler提供了类似于ISAPI Server Extention的功能，而HttpModule实现了类似于ISAPI Filter的功能。使用自定义的Handler会覆盖系统默认的Handler，而Module是可以多个同时存在的。