Generate Captcha using Golang
A detailed guide on how to generate Captcha using Golang to protect your web application from automated attacks and bots.
In this article, we'll learn how to create a simple Captcha using the github.com/dchest/captcha library in Golang. This guide provides a clear example to help you integrate Captcha into your web application.
Golang Code
package main
import (
"net/http"
"github.com/dchest/captcha"
)
func captchaHandler(w http.ResponseWriter, r *http.Request) {
captchaID := captcha.New()
http.ServeFile(w, r, "./index.html")
}
func captchaImageHandler(w http.ResponseWriter, r *http.Request) {
captchaID := r.URL.Query().Get("id")
captcha.WriteImage(w, captchaID, 240, 80)
}
func main() {
http.HandleFunc("/captcha", captchaHandler)
http.HandleFunc("/captcha/image", captchaImageHandler)
http.Handle("/captchaFiles/", http.StripPrefix("/captchaFiles/", http.FileServer(http.Dir("./"))))
http.ListenAndServe(":8080", nil)
}
index.html
<!DOCTYPE html>
<html>
<head>
<title>Captcha Demo</title>
</head>
<body>
<h1>Captcha Example</h1>
<form action="/verify" method="post">
<img src="/captcha/image?id={{.CaptchaID}}" alt="Captcha Image">
<input type="text" name="captcha" placeholder="Enter Captcha">
<input type="submit" value="Submit">
</form>
</body>
</html>
Detailed explanation:
-
captcha.New(): Creates a new Captcha ID. -
captcha.WriteImage: Converts the Captcha ID into an image and sends it to the user's browser. -
http.HandleFunc: Registers the handler functions for the endpoints. -
http.ListenAndServe(":8080", nil): Starts the server on port 8080.
System Requirements:
- Golang 1.15 or later
- Library
github.com/dchest/captcha
How to install the libraries needed to run the Golang code above:
Run the command:
go get github.com/dchest/captcha
Tips:
- Ensure you keep the
captchalibrary updated to avoid security vulnerabilities. - Adjust the Captcha size to fit your user interface appropriately.