deskhub/DeskHub-Webseite/includes/smtp_mailer.php

<?php
/**
 * Einfacher SMTP-Client ohne externe Abhängigkeiten (kein Composer/PHPMailer).
 *
 * Grund: PHP mail() ist auf vielen Hosting-Paketen unzuverlässig (hängt vom
 * lokal konfigurierten Sendmail/Postfix ab, landet oft im Spam-Ordner ohne
 * korrekte SPF/DKIM-Anbindung des Hosters). Mit eigenen SMTP-Zugangsdaten
 * (z.B. vom E-Mail-Provider der Domain) wird stattdessen direkt und
 * zuverlässig über deren Mailserver versendet.
 *
 * Unterstützt: SMTP mit STARTTLS (Port 587), implizites SSL (Port 465),
 * unverschlüsselt (Port 25, nicht empfohlen) sowie AUTH LOGIN.
 */
class SmtpMailer
{
    private string $host;
    private int $port;
    private string $encryption; // 'none' | 'tls' | 'ssl'
    private string $username;
    private string $password;
    private int $timeout;
    private $socket = null;
    private string $lastError = '';

    public function __construct(string $host, int $port, string $encryption, string $username, string $password, int $timeout = 12)
    {
        $this->host = $host;
        $this->port = $port;
        $this->encryption = $encryption;
        $this->username = $username;
        $this->password = $password;
        $this->timeout = $timeout;
    }

    public function getLastError(): string
    {
        return $this->lastError;
    }

    /**
     * Sendet eine E-Mail. $to/$from können "Name <adresse>" oder nur die
     * Adresse sein. $htmlBody wird als text/html (UTF-8, Base64) versendet.
     */
    public function send(string $to, string $from, string $subject, string $htmlBody): bool
    {
        try {
            $this->connect();
            $this->ehlo();
            if ($this->encryption === 'tls') {
                $this->startTls();
                $this->ehlo(); // EHLO muss nach STARTTLS wiederholt werden
            }
            if ($this->username !== '') {
                $this->authLogin();
            }

            $fromEmail = $this->extractEmail($from);
            $toEmail = $this->extractEmail($to);

            $this->command("MAIL FROM:<{$fromEmail}>", [250]);
            $this->command("RCPT TO:<{$toEmail}>", [250, 251]);
            $this->command('DATA', [354]);

            $headers = $this->buildHeaders($to, $from, $subject);
            $encodedBody = chunk_split(base64_encode($htmlBody), 76, "\r\n");
            $payload = $headers . "\r\n" . $encodedBody . "\r\n.";
            $this->write($payload);
            $this->readResponse([250]);

            $this->command('QUIT', [221], false);
            $this->close();
            return true;
        } catch (\Throwable $e) {
            $this->lastError = $e->getMessage();
            $this->close();
            return false;
        }
    }

    private function connect(): void
    {
        $prefix = $this->encryption === 'ssl' ? 'ssl://' : 'tcp://';
        $this->socket = @stream_socket_client(
            "{$prefix}{$this->host}:{$this->port}",
            $errno, $errstr, $this->timeout,
            STREAM_CLIENT_CONNECT, stream_context_create(['ssl' => ['verify_peer' => true, 'verify_peer_name' => true]])
        );
        if (!$this->socket) {
            throw new \RuntimeException("Verbindung zu {$this->host}:{$this->port} fehlgeschlagen: {$errstr} ({$errno})");
        }
        stream_set_timeout($this->socket, $this->timeout);
        $this->readResponse([220]);
    }

    private function ehlo(): void
    {
        $domain = $_SERVER['SERVER_NAME'] ?? 'localhost';
        $this->command("EHLO {$domain}", [250]);
    }

    private function startTls(): void
    {
        $this->command('STARTTLS', [220]);
        $ok = @stream_socket_enable_crypto($this->socket, true, STREAM_CRYPTO_METHOD_TLS_CLIENT);
        if (!$ok) {
            throw new \RuntimeException('STARTTLS-Verschlüsselung konnte nicht aktiviert werden.');
        }
    }

    private function authLogin(): void
    {
        $this->command('AUTH LOGIN', [334]);
        $this->command(base64_encode($this->username), [334]);
        $this->command(base64_encode($this->password), [235]);
    }

    private function buildHeaders(string $to, string $from, string $subject): string
    {
        $encodedSubject = '=?UTF-8?B?' . base64_encode($subject) . '?=';
        $headers = [];
        $headers[] = "Date: " . date('r');
        $headers[] = "To: {$to}";
        $headers[] = "From: {$from}";
        $headers[] = "Subject: {$encodedSubject}";
        $headers[] = "MIME-Version: 1.0";
        $headers[] = "Content-Type: text/html; charset=UTF-8";
        $headers[] = "Content-Transfer-Encoding: base64";
        return implode("\r\n", $headers) . "\r\n";
    }

    /** Extrahiert nur die reine Adresse aus "Name <adresse@example.com>" für die SMTP-Hüllkommandos */
    private function extractEmail(string $addr): string
    {
        if (preg_match('/<([^>]+)>/', $addr, $m)) {
            return trim($m[1]);
        }
        return trim($addr);
    }

    private function command(string $cmd, array $expectedCodes, bool $expectResponse = true): void
    {
        $this->write($cmd);
        if ($expectResponse) {
            $this->readResponse($expectedCodes);
        }
    }

    private function write(string $data): void
    {
        if (@fwrite($this->socket, $data . "\r\n") === false) {
            throw new \RuntimeException('Schreiben zum SMTP-Server fehlgeschlagen.');
        }
    }

    private function readResponse(array $expectedCodes): string
    {
        $response = '';
        $code = null;
        while (!feof($this->socket)) {
            $line = fgets($this->socket, 515);
            if ($line === false) break;
            $response .= $line;
            // Letzte Zeile einer mehrzeiligen Antwort hat ein Leerzeichen statt "-" nach dem Code
            if (preg_match('/^(\d{3})([ -])/', $line, $m)) {
                $code = (int) $m[1];
                if ($m[2] === ' ') break;
            } else {
                break;
            }
        }
        if ($code === null || !in_array($code, $expectedCodes, true)) {
            throw new \RuntimeException("Unerwartete SMTP-Antwort: " . trim($response));
        }
        return $response;
    }

    private function close(): void
    {
        if ($this->socket) {
            @fclose($this->socket);
            $this->socket = null;
        }
    }
}