als-captcha
v1.0.0
Published
Advanced CAPTCHA library
Downloads
19
Maintainers
alexsorkinReadme
als-captcha
als-captcha is a Node.js library for generating and validating a simple yet effective captcha. It employs a combination of image recognition with noise and tilt, basic math problem solving, and several other strategies to differentiate between human users and bots.
Installation
To install als-captcha, use npm:
npm i als-captchaUsage
Generating Captcha HTML
To generate a captcha, you need to create a route that returns HTML containing the captcha challenge. The als-captcha library provides an easy way to generate this HTML.
Example:
const { createCaptcha } = require('als-captcha');
app.get('/captcha', (req, res) => {
const captchaHtml = createCaptcha({ includeAudio:true, maxAge:1000*60*10 })
res.send(`<!DOCTYPE html>
<html lang="en">
<head>
<title>HEllo</title>
</head>
<body>
<form>
${captchaHtml}
</form>
<body>
</html>
`);
});Parameters:
includeAudio:(default:true) - if true, sends audio for listening problem to solvemaxAge:(default:10006010) - captcha life time (after this time, captcha outdated)
Validating Captcha
To validate the captcha, create a route where the captcha form is submitted. The als-captcha library provides a function to validate the captcha response.
Example:
const { checkCaptcha } = require('als-captcha');
app.post('/submit-captcha', (req, res) => {
if (checkCaptcha(req.body)) {
res.send("right");
} else {
res.send("wrong");
}
});Security Strategies
als-captcha uses multiple strategies to enhance security:
- Image Recognition Challenge: A captcha image with noise, tilt, and bot-unfriendly font.
- Math Problem Solving: A basic math problem that must be solved correctly, ensuring complete text recognition.
- Hidden
importantInfoField: Remains empty and is used to detect bots that might fill it. - Bot Detection through
onchangeEvent: If theonchangeevent does not trigger, thebotfield retains its default value, indicating a bot. - Timestamp and Screen Dimension Check: Captures the time taken to complete the captcha and multiplies the screen's color depth with its width to generate a unique number, which helps in bot detection.