gocaptcha

A simple captcha service written in Go. It generates a random captcha image and stores it in memory for a configurable amount of time. The image is then served as a PNG file.

The captcha image is generated using the comic.ttf font.

Verfication is done by checking if the captcha image is stored in memory. If it is, the captcha is considered valid.

Set envvar ALLOWED_ORIGINS if you want to call /getcaptcha from browser. If you won't set it, header Access-Control-Allow-Origin will be set to https://mozilla.org.

Deploy to Google Cloud Functions

echo '{ "ALLOWED_ORIGINS": "https://example.com,https://anotherdomain.com" }' > env.json

gcloud functions deploy CaptchaFunction \
--runtime go122 \
--trigger-http \
--env-vars-file env.json \
--allow-unauthenticated \
--region europe-north1 \
--entry-point CaptchaHandler

Usage

As a library

package main

import (
	"fmt"
	"net/http"

	"github.com/t0mk/gocaptcha"
)

func main() {
	// Set up routes
	http.HandleFunc("/getcaptcha", gocaptcha.CaptchaHandler)
	http.HandleFunc("/verify", gocaptcha.CaptchaHandler)

	// Start the HTTP server
	err := http.ListenAndServe(":8080", nil)
	if err != nil {
		fmt.Println("Failed to start server:", err)
	}
}

As a CLI

go run cli/main.go