commitcaptcha/CaptchaManager.php

<?php declare(strict_types=1);
namespace commitcaptcha;
use Nette\Utils\Image;
use Chandler\Session\Session;
use Chandler\Patterns\TSimpleSingleton;

class CaptchaManager
{
    private $session;
    
    private function __construct()
    {
        $this->session = Session::i();
    }
    
    private function generateColor(bool $maxOutRed = false): array
    {
        return [
            "red"   => $maxOutRed ? 255 : random_int(0, 150),
            "green" => random_int(0, 100),
            "blue"  => random_int(0, 150),
            "alpha" => 0,
        ];
    }
    
    private function generateCode(): string
    {
        return mb_strtoupper(str_replace("/", "+", base64_encode(openssl_random_pseudo_bytes(6))));
    }
    
    private function applyNoiseOnImage(Image $image, \Closure $fun): void
    {
        $_noise = (function() use ($image) {
            foreach(range(1, 33) as $x)
                foreach(range(1, 13) as $y)
                    $image->setPixel($x * 5, $y * 5, $this->generateColor());
        });
        
        $_noise();
        $fun();
        $_noise();
    }
    
    private function applyLinesOnImage(Image $image, \Closure $fun): void
    {
        $_lines = (function() use ($image) {
            foreach(range(1, random_int(2, 6)) as $i)
                $image->line(random_int(0, 15), random_int(0, 65), random_int(150, 165), random_int(0, 65), $this->generateColor());
        });
        
        $_lines();
        $fun();
        $_lines();
    }
    
    private function generateCaptchaImage(string $code): Image
    {
        $image = Image::fromBlank(165, 65, $this->generateColor());
        
        $this->applyNoiseOnImage($image, function() use ($image, $code) {
            $this->applyLinesOnImage($image, function() use ($image, $code) {
                $length = iconv_strlen($code);
                $offset = 165 / $length;
                
                for($i = 0; $i < $length; $i++) {
                    $letter = $code[$i];
                    $font   = __DIR__ . "/data/san-francissco.ttf";
                    $x      = (int) ceil(0 + ($offset * $i));
                    $y      = random_int(45, 55);
                    
                    $image->ttfText(random_int(18, 28), random_int(-10, 10), $x, $y, $this->generateColor(true), $font, $letter);
                }
            });
        });
        
        return $image;
    }
    
    function getImage(): Image
    {
        $code  = $this->generateCode();
        $hash  = hash("crc32b", mb_strtolower($code));
        $image = $this->generateCaptchaImage($code);
        
        $nonce   = bin2hex(openssl_random_pseudo_bytes(SODIUM_CRYPTO_STREAM_NONCEBYTES / 2));
        $key     = substr(CHANDLER_ROOT_CONF["security"]["secret"], 0, SODIUM_CRYPTO_STREAM_KEYBYTES);
        $encHash = sodium_crypto_stream_xor($hash, $nonce, $key);
        $this->session->set("captcha", implode(":", [
            time(),
            $nonce,
            base64_encode($encHash),
        ]));
        
        return $image;
    }
    
    function verifyCaptcha(?string $input = NULL): bool
    {
        if(!COMMITCAPTCHA_ROOT_CONF["commitcaptcha"]["enable"])
            return true;
        
        if(!$input)
            $input = $_POST["captcha"];
        
        $data = $this->session->get("captcha");
        if(!$data)
            return false;
        
        $this->session->set("captcha", "");
        
        [$time, $nonce, $encHash] = explode(":", $data);
        if((time() - $time) > 3600)
            return false;
        
        $key  = substr(CHANDLER_ROOT_CONF["security"]["secret"], 0, SODIUM_CRYPTO_STREAM_KEYBYTES);
        $hash = sodium_crypto_stream_xor(base64_decode($encHash), $nonce, $key);
        return hash_equals(hash("crc32b", mb_strtolower($input)), $hash);
    }
    
    use TSimpleSingleton;
}