2025年6月24日 星期二

[研究]ASP.NET, WebForm, MasterPage, 跨站請求偽造 XSRF/CSRF(Cross-Site Request Forgery)防護

[研究]ASP.NET, WebForm, MasterPage, 跨站請求偽造 XSRF/CSRF(Cross-Site Request Forgery)防護

2025-06-24

環境:Visual Studio 2022 + ASP.NET + WebForm + Web Application + C# + SQL Server 2019 + SQL Server Management Studio (SSMS) 19

********************************************************************************

Site1.master
<%@ Master Language="C#" AutoEventWireup="true" CodeBehind="Site1.master.cs" 
    Inherits="WebApplication1.Site1" %>

<!DOCTYPE html>

<html>
<head runat="server">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
    <title></title>
    <asp:ContentPlaceHolder ID="head" runat="server">
    </asp:ContentPlaceHolder>
</head>
<body>
    <form id="form1" runat="server">
        <asp:HiddenField ID="AntiCsrfToken" runat="server" />
        <asp:ContentPlaceHolder ID="ContentPlaceHolder1" runat="server">
        </asp:ContentPlaceHolder>
    </form>
</body>
</html>


Site1.master.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace WebApplication1
{
    public partial class Site1 : System.Web.UI.MasterPage
    {
        private const string AntiXsrfTokenKey = "__AntiXsrfToken";
        private const string AntiXsrfUserNameKey = "__AntiXsrfUserName";
        private string _antiXsrfTokenValue;

        protected void Page_Init(object sender, EventArgs e)
        {
            // The code below helps to protect against XSRF attacks
            var requestCookie = Request.Cookies[AntiXsrfTokenKey];

            if (requestCookie != null && Guid.TryParse(requestCookie.Value, out Guid requestCookieGuidValue))
            {
                // Use the Anti-XSRF token from the cookie
                _antiXsrfTokenValue = requestCookie.Value;
                Page.ViewStateUserKey = _antiXsrfTokenValue;
            }
            else
            {
                // Generate a new Anti-XSRF token and save to the cookie
                _antiXsrfTokenValue = Guid.NewGuid().ToString("N");
                Page.ViewStateUserKey = _antiXsrfTokenValue;

                var responseCookie = new HttpCookie(AntiXsrfTokenKey)
                {
                    HttpOnly = true,
                    Value = _antiXsrfTokenValue
                };
                if (FormsAuthentication.RequireSSL && Request.IsSecureConnection)
                {
                    responseCookie.Secure = true;
                }
                Response.Cookies.Set(responseCookie);
            }

            Page.PreLoad += master_Page_PreLoad;
        }
        protected void master_Page_PreLoad(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                // Set Anti-XSRF token
                ViewState[AntiXsrfTokenKey] = Page.ViewStateUserKey;
                ViewState[AntiXsrfUserNameKey] = Context.User.Identity.Name ?? string.Empty;
            }
            else
            {
                // Validate the Anti-XSRF token
                if ((string)ViewState[AntiXsrfTokenKey] != _antiXsrfTokenValue 
                    || (string)ViewState[AntiXsrfUserNameKey] != (Context.User.Identity.Name ?? string.Empty))
                {
                    throw new InvalidOperationException("Validation of Anti-XSRF token failed.");
                }
            }
        }
        protected void Page_Load(object sender, EventArgs e)
        {
        }
    }
}


Default.aspx

<%@ Page Title="" Language="C#" MasterPageFile="~/Site1.Master" AutoEventWireup="true"
    CodeBehind="Default.aspx.cs" Inherits="WebApplication1.Default" %>
<asp:Content ID="Content1" ContentPlaceHolderID="head" runat="server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">
    <asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />
</asp:Content>


Default.aspx.cs

using System;

namespace WebApplication1
{
    public partial class Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void Button1_Click(object sender, EventArgs e)
        {
            Response.Write("XSRF (CSRF) 測試範例!");
        }
    }
}

用 OWASP Zed Attack Proxy (ZAP) 2.16.1 (2025-03-26 釋出) 測試

(完)

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