preventing cross-site request forgery (csrf) attacks in asp.net web forms

Question

I have created an ASP.Net Web Forms application using Visual Studio 2013 and I am using .NET Framework 4.5. I want to make sure my site is secure from Cross-Site Request For

Answer 1

When you create a new 'Web Form Application' project in VS 2013, the site.master.cs will automatically include the XSRF/CSRF code in the Page_Init section of the class. If you still dont get the generated code, you can manually Copy + Paste the code. If you are using C#, then use the below:-

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];
        Guid requestCookieGuidValue;
        if (requestCookie != null && Guid.TryParse(requestCookie.Value, out 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.");
            }
        }
    }