How to implement reCaptcha V3 in ASP.NET

Does anyone have a full implementation demo of reCaptcha V3 in ASP.NET?

I found this article: Google Recaptcha v3 example demo

At the moment I am using reCaptcha V2 with the following code:

public bool RecaptchaValidate()
    {
        string Response = Request.Form["g-recaptcha-response"];//Getting Response String Append to Post Method
        bool Valid = false;
        //Request to Google Server
        var CaptchaSiteKey = Settings["NewUserRegCaptchaSecretSiteKey"].ToString();
        HttpWebRequest req = (HttpWebRequest)WebRequest.Create
        (" https://www.google.com/recaptcha/api/siteverify?secret=" + CaptchaSiteKey + "&response=" + Response);
        try
        {
            //Google recaptcha Response
            using (WebResponse wResponse = req.GetResponse())
            {

                using (StreamReader readStream = new StreamReader(wResponse.GetResponseStream()))
                {
                    string jsonResponse = readStream.ReadToEnd();

                    JavaScriptSerializer js = new JavaScriptSerializer();
                    ReCaptchaObject data = js.Deserialize<ReCaptchaObject>(jsonResponse);// Deserialize Json

                    Valid = Convert.ToBoolean(data.success);
                }
            }

            return Valid;
        }
        catch (WebException ex)
        {
            throw ex;
        }
    }

On the view.ascx page I have:

<%@ Register TagPrefix="recaptcha" Namespace="Recaptcha" Assembly="Recaptcha" %>

<script src='https://www.google.com/recaptcha/api.js'></script>

<scrip>
var recap = grecaptcha.getResponse();
if (recap.length == 0) {
                $("#verifyhuman").css("display", "block");
            }
</script>

 <div class="g-recaptcha" data-sitekey="<%=ReCaptchaPublicKey%>" id="recaptcha" data-callback="recaptchaCallback"></div>

Contents hide

Answers:

Method 1

Method 2

Method 3

Method 4

Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

The simplest implementation:

In your cshtml file (at the top)

@section Scripts
{
    <script src="https://www.google.com/recaptcha/api.js?render=your site key"></script>
    <script>
        grecaptcha.ready(function () {
            grecaptcha.execute('your site key', { action: 'homepage' }).then(function (token) {
                document.getElementById("foo").value = token;
            });
        });
    </script>
}

In your cshtml, inside the form (just before </form>):
```
<input type="hidden" id="foo" name="foo" />
```

A function inside your Pagemodel class. See the documentation for the response object:

public static bool ReCaptchaPassed(string gRecaptchaResponse)
{
    HttpClient httpClient = new HttpClient();

    var res = httpClient.GetAsync($"https://www.google.com/recaptcha/api/siteverify?secret=your secret key no quotes&response={gRecaptchaResponse}").Result;

    if (res.StatusCode != HttpStatusCode.OK) 
    {
        return false;
    }
    string JSONres = res.Content.ReadAsStringAsync().Result;
    dynamic JSONdata = JObject.Parse(JSONres);

    if (JSONdata.success != "true" || JSONdata.score <= 0.5m)
    {
        return false;
    }

    return true;
}

Finally, inside your OnPostAsync() handler, at the top:

if (!ModelState.IsValid) 
{
    return Page();
}
else
{
    if (!ReCaptchaPassed(Request.Form["foo"]))
    {
        ModelState.AddModelError(string.Empty, "You failed the CAPTCHA.");
        return Page();
    }
}

Method 2

Edit : I have added a demo project . Check this github repository .
https://github.com/NIHAR-SARKAR/GoogleRecaptchav3-example-In-asp.net

From frontend (.aspx page) you need to send ajax request to pass the token to backend server . Using “recaptcha.execute” U can get the response , and pass the token using ajax request .Please check the code block .

 <script src="https://www.google.com/recaptcha/api.js?render=recaptchaSiteKey"></script>
<script>
 grecaptcha.ready(function() {
 grecaptcha.execute('recaptchaSiteKey', {action: 'homepage'}).then(function(token) {

            $.ajax({
                //pass the toket to Webmethod using Ajax
            });
          });
     });
</script>

Reference link:
https://developers.google.com/recaptcha/docs/verify
https://developers.google.com/recaptcha/docs/display#js_api

Now in the aspx.cs you need to write a “[WebMethod]” to receive the token from Ajax request .

    [WebMethod]
    public static void CaptchaVerify(string token)
    {
            var responseString = RecaptchaVerify(token);
            ResponseToken response = new ResponseToken();
            response = Newtonsoft.Json.JsonConvert.DeserializeObject<ResponseToken>(responseString.Result);

    }

To get the response from google recapcha api u need to use async call using httpClient . you also need to create a class which will contain same properties like the response string . After getting the “responseString” u need to convert the response to ResponseToken object by using Newtonsoft.Json.
response = Newtonsoft.Json.JsonConvert.DeserializeObject<ResponseToken>(responseString.Result);

private string apiAddress = "https://www.google.com/recaptcha/api/siteverify";

private string recaptchaSecret = googleRecaptchaSecret;

        public async Task<string> RecaptchaVerify(string recaptchaToken)
        {
            string url = $"{apiAddress}?secret={recaptchaSecret}&response={recaptchaToken}";
            using (var httpClient = new HttpClient())
            {
                try
                {

                    string responseString=  httpClient.GetStringAsync(url).Result;
                    return responseString;

                }
                catch (Exception ex)
                {
                    throw new Exception(ex.Message);
                }
            }
        }


        public class ResponseToken
        {

            public DateTime challenge_ts { get; set; }
            public float score { get; set; }
            public List<string> ErrorCodes { get; set; }
            public bool Success { get; set; }
            public string hostname { get; set; }
        }

Method 3

The accepted answer on this page is totally wrong!!! Google returns a score between 0 and 1 to indicate whether the submission is likely to be a bot or likely to be a human.

The success property returned only means that the recaptcha token was processed correctly.

It is the score property that should be checked, not the success property

These lines are the probelem

if (JSONdata.success != "true")
    return false;

return true;

The actual score to compare will probably be in a variable that can be adjusted if need be. Google recommends starting with 0.5.

So the code should change to something like:

var recaptchaScore = 0.5m; // this could be in appSettings or whereever/however you are storing your constants

if (JSONdata.success != "true" || JSONdata.score <= recaptchaScore)
    return false;

return true;

Of course you will likely want to add logging etc to this answer but this is the bare logic that is required.

Method 4

There are several Recaptcha libraries available for ASP.Net. I chose to use reCAPTCHA.AspNetCore because it provides an HtmlHelper.

Please note that this library only supports one ReCatpcha per page, and it doesn’t support Recaptcha v3 passive monitoring on non-form pages.

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

0 0 votes

Article Rating