Invisible reCAPTCHA

Google - Invisible reCAPTCHA your Webpage and Mobile Apps!

This blog Post will helps you to understand and learn how to enable and customize the Invisible reCAPTCHA on your webpage?. There are two ways to enable and customize the Google Invisible reCAPTCHA i.e.


HTML and JavaScript API Resource Configuration-
Steps 1 - Go to URL https://www.google.com/recaptcha/admin and login with your credentials.
Steps 2 - Register the reCAPTCHA for your site with your site Label.

Select your Invisible reCAPTCHA radio button. After selecting Invisible reCAPTCHA, we will need to add your Domains mane where you want to add this Invisible reCAPTCHA and click on register with terms of services.

For example - My added domain is - localhost and site Label is - test
After successful register, you can see a screen like below pic.

Generated Adding reCAPTCHA to your site -
Site key -********* and Secret key --********

Client side integration -  Script section - Paste this script before the closing </head> tag on your HTML page.
<script src='https://www.google.com/recaptcha/api.js'></script>

HTML Sections - Paste below code at the end of the <form> to create a button protected by the Invisible reCAPTCHA.
<button class="g-recaptcha" data-sitekey="6Lc*****EUAAAAANAzwf*****XmNmu2****"
        data-callback="YourOnSubmitFn"> Submit </button>

Full Example -
<html>
<head>
    <script>
  function onSubmit(token) {
    alert('thanks ' + document.getElementById('username').value);
  }

  function validate(event) {
    event.preventDefault();
    if (!document.getElementById('username').value) {
      alert("You must add text to the required username");
    }
            else {
      grecaptcha.execute();
    }
  }

  function onload() {
    var element = document.getElementById('submit');
    element.onclick = validate;
  }
    </script>
    <script src="https://www.google.com/recaptcha/api.js" async defer></script>
</head>
<body>
    <form>
        Name: (required) <input id="username" name="username">
        <div id='recaptcha' class="g-recaptcha"
             data-sitekey="6Lc***EUAAA*******PRUAIEbJR7z5ulMQz***"
             data-callback="onSubmit"
             data-size="invisible"></div>
        <button id='submit'>submit</button>
    </form>
    <script>onload();</script>
</body>
</html>

References -


Google's New Invisible reCAPTCHA in MVC (Using Action Filters) -

Step 1 - Go to URL https://www.google.com/recaptcha/admin and login with your credentials
Step 2 - Register the reCAPTCHA for your site with your site Label.

Select your Invisible reCAPTCHA radio button. After selecting Invisible reCAPTCHA, we will need to add your Domains mane where you want to add this Invisible reCAPTCHA and click on register with terms of services.

For example - My added domain is - localhost and site Label is - test. You can see the above steps for the same.

Step 3Add Script Bundle in the Bundle
  bundles.Add(new ScriptBundle("~/bundles/recaptcha", "//www.google.com/recaptcha/api.js").Include("~/Scripts/recaptcha-api.js"));

HTML page-
@model LoginViewModel
@using (Html.BeginForm("Login", "Account", new { ReturnUrl = ViewBag.ReturnUrl }, FormMethod.Post, new { @class = "", role = "form", id = "LoginForm" }))
{
    <div class="form-group" id="loginSection">
        @Html.AntiForgeryToken()
        @Html.ValidationSummary(true, "", new { @class = "text-danger" })
        @Html.TextBoxFor(m => m.Email, new { @class = "form-control", placeholder = "Email", id = "txtEmail", autofocus = "autofocus" })
        @Html.ValidationMessageFor(m => m.Email, "", new { @class = "text-danger" })
    </div>
    <div class="clr_10"></div>
    <button class="g-recaptcha btn btn-default"
            data-sitekey="@Model.RecaptchaPublicKey"
            data-callback="OnSubmit">
        Generate Pass Code
    </button>
}

And Load JavaScript API

@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
    @Scripts.Render("~/bundles/recaptcha")
    <script>
           function OnSubmit(token) {
                  document.getElementById("LoginForm").submit();
            }
    </script>
}

AND

    public class LoginViewModel
    {
        [Required]
        [Display(Name = "Email")]
        [EmailAddress]
        public string Email { get; set; }

        //[Required]
        [DataType(DataType.Password)]
        [Display(Name = "Password")]
        public string Password { get; set; }

        [Display(Name = "Remember me?")]
        public bool RememberMe { get; set; }

        public string RecaptchaPublicKey { get; }
        public LoginViewModel() { }
        public LoginViewModel(string recaptchaPublicKey)
        {
            RecaptchaPublicKey = recaptchaPublicKey;
        }
    }

Step 4 - Install Autofac and Autofac.MVC5 using Nuget package manager in the portal app.
Step 5 - Create Invisible reCAPTCHA Validation Service
Interface -
public interface ICaptchaValidationService
    {
        bool Validate(string response);
    }

Interface implementation -
public class InvisibleRecaptchaValidationService : ICaptchaValidationService
    {
        private const string API_URL = "https://www.google.com/recaptcha/api/siteverify";
        private readonly string _secretKey;

        public InvisibleRecaptchaValidationService(string secretKey)
        {
            _secretKey = secretKey;
        }

        public bool Validate(string response)
        {
            if (!string.IsNullOrWhiteSpace(response))
            {
                using (var client = new WebClient())
                {
                    var result = client.DownloadString($"{API_URL}?secret={_secretKey}&response={response}");
                    return ParseValidationResult(result);
                }
            }
            return false;
        }

        private bool ParseValidationResult(string validationResult) => (bool)JObject.Parse(validationResult).SelectToken("success");
    }

Step 6 - Create Validate reCAPTCHA on the Server using this custom Attribute
    public class ValidateRecaptchaAttribute : ActionFilterAttribute
    {
        private const string RECAPTCHA_RESPONSE_KEY = "g-recaptcha-response";
        public ICaptchaValidationService CaptchaService { get; set; }

        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            var isValidate =   new InvisibleRecaptchaValidationService(ConfigurationManager.AppSettings["RecaptchaSecretKey"]).Validate(filterContext.HttpContext.Request[RECAPTCHA_RESPONSE_KEY]);
            if (!isValidate)
                filterContext.Controller.ViewData.ModelState.AddModelError("Recaptcha", "Captcha validation failed.");
        }
    }

Step 7 -
    //GET: /Account/Login
    [AllowAnonymous]
    public ActionResult Login(string returnUrl)
    {
        if (System.Web.HttpContext.Current.User.Identity.IsAuthenticated)
        {
            return RedirectToAction("Index", "Home");
        }
        return View(new LoginViewModel(ConfigurationManager.AppSettings["RecaptchaPublicKey"]));
    }

Step 8 -
     //POST: /Account/Login
    [HttpPost]
    [AllowAnonymous]
    [ValidateRecaptcha]
    public ActionResult Login(LoginViewModel model, string returnUrl)
    {
        if (ModelState.IsValid)
        {

        }
        return View("Login");
    }

Step 9 - Add the below code in the config file.
    <add key="RecaptchaSecretKey" value="6Lcf****AAAEJN**EPRU***" />
    <add key="RecaptchaPublicKey" value="****b27MgXmNmu2****OocE" />
     
AND

<dependentAssembly>
        <assemblyIdentity name="Autofac" publicKeyToken="17863af14b0044da" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-4.6.1.0" newVersion="4.6.1.0" />
      </dependentAssembly>
    </assemblyBinding>

Live Result -

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ANIL SINGH

Anil Singh is an author, tech blogger, and software programmer. Book writing, tech blogging is something do extra and Anil love doing it. For more detail, kindly refer to this link..

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