recaptcha
- Installation
- Usage examples
  - reCAPTCHA v3
  - reCAPTCHA v2

recaptcha

The recaptcha middleware provides Google reCAPTCHAopen in new window integration for Flame instances.

You can read source code of this middleware on GitHubopen in new window and API documentation on pkg.go.devopen in new window.

Installation

The minimum requirement of Go is 1.16.

go get github.com/flamego/recaptcha

Usage examples

WARNING

Examples included in this section is to demonstrate the usage of the recaptcha middleware, by no means illustrates the idiomatic or even correct way of doing user authentication.

reCAPTCHA v3

The recaptcha.V3open in new window is used in combination with recaptcha.Optionsopen in new window for reCAPTCHA v3open in new window integration, and the recaptcha.RecaptchaV3.Verify should be used to verify response tokens:

main.go
templates/home.tmpl

package main
import (
    "fmt"
    "net/http"
    "github.com/flamego/flamego"
    "github.com/flamego/recaptcha"
    "github.com/flamego/template"
)
func main() {
    f := flamego.Classic()
    f.Use(template.Templater())
    f.Use(recaptcha.V3(
        recaptcha.Options{
            Secret:    "<SECRET>",
            VerifyURL: recaptcha.VerifyURLGoogle,
        },
    ))
    f.Get("/", func(t template.Template, data template.Data) {
        data["SiteKey"] = "<SITE KEY>"
        t.HTML(http.StatusOK, "home")
    })
    f.Post("/", func(w http.ResponseWriter, r *http.Request, re recaptcha.RecaptchaV3) {
        token := r.PostFormValue("g-recaptcha-response")
        resp, err := re.Verify(token)
        if err != nil {
            w.WriteHeader(http.StatusBadRequest)
            _, _ = w.Write([]byte(err.Error()))
            return
        } else if !resp.Success {
            w.WriteHeader(http.StatusBadRequest)
            _, _ = w.Write([]byte(fmt.Sprintf("Verification failed, error codes %v", resp.ErrorCodes)))
            return
        }
        w.WriteHeader(http.StatusOK)
        _, _ = w.Write([]byte("Verified!"))
    })
    f.Run()
}

<html>
<head>
  <script src="https://www.google.com/recaptcha/api.js"></script>
</head>
<body>
<script>
  function onSubmit(token) {
    document.getElementById("demo-form").submit();
  }
</script>
<form id="demo-form" method="POST">
  <button class="g-recaptcha"
    data-sitekey="{{.SiteKey}}"
    data-callback='onSubmit'
    data-action='submit'>Submit</button>
</form>
</body>
</html>

Because reCAPTCHA v3 is non-interruptive, you will not see any captcha image in the browser.

reCAPTCHA v2

The recaptcha.V2open in new window is used in combination with recaptcha.Optionsopen in new window for reCAPTCHA v2open in new window integration, and the recaptcha.RecaptchaV2.Verify should be used to verify response tokens.

The following example is using the “I’m not a robot” Checkbox type of challenge:

main.go
templates/home.tmpl

package main
import (
    "fmt"
    "net/http"
    "github.com/flamego/flamego"
    "github.com/flamego/recaptcha"
    "github.com/flamego/template"
)
func main() {
    f := flamego.Classic()
    f.Use(template.Templater())
    f.Use(recaptcha.V2(
        recaptcha.Options{
            Secret:    "<SECRET>",
            VerifyURL: recaptcha.VerifyURLGoogle,
        },
    ))
    f.Get("/", func(t template.Template, data template.Data) {
        data["SiteKey"] = "<SITE KEY>"
        t.HTML(http.StatusOK, "home")
    })
    f.Post("/", func(w http.ResponseWriter, r *http.Request, re recaptcha.RecaptchaV2) {
        token := r.PostFormValue("g-recaptcha-response")
        resp, err := re.Verify(token)
        if err != nil {
            w.WriteHeader(http.StatusBadRequest)
            _, _ = w.Write([]byte(err.Error()))
            return
        } else if !resp.Success {
            w.WriteHeader(http.StatusBadRequest)
            _, _ = w.Write([]byte(fmt.Sprintf("Verification failed, error codes %v", resp.ErrorCodes)))
            return
        }
        w.WriteHeader(http.StatusOK)
        _, _ = w.Write([]byte("Verified!"))
    })
    f.Run()
}

<html>
<head>
  <script src="https://www.google.com/recaptcha/api.js"></script>
</head>
<body>
  <form method="POST">
    <div class="g-recaptcha" data-sitekey="{{.SiteKey}}"></div>
    <input type="submit" name="button" value="Submit">
  </form>
</body>
</html>

Below is how it would look like in your browser for the above example: