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server/contact.mjs

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+/**
+ * The contact form handler. nginx proxies POST /contact here; everything else on the site stays static.
+ *
+ * The form posts first_name, last_name, email, message, lang and the honeypot website. A browser
+ * with scripting asks for JSON and shows the result in place; without scripting the answer is a
+ * redirect to /contact/sent or /contact/error (under /de for German).
+ *
+ * Configuration comes from the environment only, see README.md.
+ */
+import { createServer } from 'node:http';
+import nodemailer from 'nodemailer';
+
+const env = process.env;
+const PORT = Number(env.CONTACT_PORT || 3000);
+const HOST = env.CONTACT_HOST || '127.0.0.1';
+const TO = env.CONTACT_TO || 'office@ciphercell.de';
+const FROM = env.CONTACT_FROM || env.SMTP_USER;
+const SMTP_PORT = Number(env.SMTP_PORT || 587);
+
+if (!env.SMTP_HOST || !FROM) {
+  console.error('contact: SMTP_HOST and CONTACT_FROM (or SMTP_USER) must be set.');
+  process.exit(78); // EX_CONFIG: the entrypoint does not restart on this one.
+}
+
+const transport = nodemailer.createTransport({
+  host: env.SMTP_HOST,
+  port: SMTP_PORT,
+  // 465 speaks TLS from the first byte; 587 and 25 upgrade with STARTTLS, which we then require.
+  // SMTP_REQUIRE_TLS=false is for a local mail catcher only.
+  secure: env.SMTP_SECURE ? env.SMTP_SECURE === 'true' : SMTP_PORT === 465,
+  requireTLS: env.SMTP_REQUIRE_TLS !== 'false' && SMTP_PORT !== 465,
+  auth: env.SMTP_USER ? { user: env.SMTP_USER, pass: env.SMTP_PASS } : undefined,
+});
+
+/* Limits. The body cap is generous for four short fields; the rate caps stop a flood, not a person. */
+const MAX_BODY = 32 * 1024;
+const MAX = { first_name: 100, last_name: 100, email: 254, message: 5000 };
+const PER_IP = { count: 5, windowMs: 10 * 60 * 1000 };
+const GLOBAL = { count: 60, windowMs: 60 * 60 * 1000 };
+
+const hits = new Map();
+const globalHits = [];
+function limited(ip, now = Date.now()) {
+  while (globalHits.length && now - globalHits[0] > GLOBAL.windowMs) globalHits.shift();
+  const mine = (hits.get(ip) || []).filter((t) => now - t < PER_IP.windowMs);
+  if (mine.length >= PER_IP.count || globalHits.length >= GLOBAL.count) return true;
+  mine.push(now);
+  hits.set(ip, mine);
+  globalHits.push(now);
+  return false;
+}
+setInterval(() => {
+  const now = Date.now();
+  for (const [ip, list] of hits) if (list.every((t) => now - t >= PER_IP.windowMs)) hits.delete(ip);
+}, PER_IP.windowMs).unref();
+
+const EMAIL = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
+const oneLine = (s) => s.replace(/[\r\n\t]+/g, ' ').trim();
+
+function validate(form) {
+  const data = {
+    first_name: oneLine(form.get('first_name') || ''),
+    last_name: oneLine(form.get('last_name') || ''),
+    email: oneLine(form.get('email') || ''),
+    message: (form.get('message') || '').replace(/\r\n/g, '\n').trim(),
+  };
+  for (const [key, max] of Object.entries(MAX)) {
+    if (!data[key] || data[key].length > max) return null;
+  }
+  return EMAIL.test(data.email) ? data : null;
+}
+
+function readBody(req) {
+  return new Promise((resolve, reject) => {
+    let size = 0;
+    const chunks = [];
+    req.on('data', (chunk) => {
+      size += chunk.length;
+      if (size > MAX_BODY) { reject(new Error('too large')); req.destroy(); return; }
+      chunks.push(chunk);
+    });
+    req.on('end', () => resolve(Buffer.concat(chunks).toString('utf8')));
+    req.on('error', reject);
+  });
+}
+
+function reply(req, res, lang, outcome) {
+  const status = { sent: 200, invalid: 400, limited: 429, failed: 502 }[outcome];
+  if ((req.headers.accept || '').includes('application/json')) {
+    res.writeHead(status, { 'Content-Type': 'application/json', 'Cache-Control': 'no-store' });
+    res.end(JSON.stringify({ ok: outcome === 'sent', outcome }));
+    return;
+  }
+  const page = outcome === 'sent' ? 'sent' : 'error';
+  res.writeHead(303, { Location: `${lang === 'de' ? '/de' : ''}/contact/${page}`, 'Cache-Control': 'no-store' });
+  res.end();
+}
+
+const server = createServer(async (req, res) => {
+  const path = (req.url || '').split('?')[0];
+  if (path === '/contact/healthz') { res.writeHead(200).end('ok\n'); return; }
+  if (req.method !== 'POST' || path !== '/contact') { res.writeHead(404).end(); return; }
+
+  // A cross-site post is not a visitor using the form.
+  const origin = req.headers.origin;
+  const host = req.headers['x-forwarded-host'] || req.headers.host;
+  if (origin && host && new URL(origin).host !== host) { res.writeHead(403).end(); return; }
+
+  let form;
+  try {
+    form = new URLSearchParams(await readBody(req));
+  } catch {
+    res.writeHead(413).end();
+    return;
+  }
+  const lang = form.get('lang') === 'de' ? 'de' : 'en';
+
+  // Filled honeypot: answer as if sent, so the bot learns nothing.
+  if (form.get('website')) { reply(req, res, lang, 'sent'); return; }
+
+  const data = validate(form);
+  if (!data) { reply(req, res, lang, 'invalid'); return; }
+
+  // nginx sets X-Real-IP from the proxy chain; fall back to the socket for local runs.
+  const ip = req.headers['x-real-ip'] || req.socket.remoteAddress || 'unknown';
+  if (limited(String(ip))) { reply(req, res, lang, 'limited'); return; }
+
+  const name = `${data.first_name} ${data.last_name}`;
+  try {
+    await transport.sendMail({
+      from: { name: 'CipherCell website', address: FROM },
+      to: TO,
+      replyTo: { name, address: data.email },
+      subject: `Website enquiry from ${name}`,
+      text: [
+        `Name: ${name}`,
+        `Email: ${data.email}`,
+        `Language: ${lang}`,
+        '',
+        data.message,
+        '',
+        '-- ',
+        'Sent from the contact form on ciphercell.de. Reply to this email to answer.',
+      ].join('\n'),
+    });
+    reply(req, res, lang, 'sent');
+  } catch (err) {
+    console.error('contact: sending failed:', err.message);
+    reply(req, res, lang, 'failed');
+  }
+});
+
+server.listen(PORT, HOST, () => console.log(`contact: listening on ${HOST}:${PORT}, delivering to ${TO}`));

server/package-lock.json

@@ -0,0 +1,25 @@
+{
+  "name": "ciphercell-contact",
+  "lockfileVersion": 3,
+  "requires": true,
+  "packages": {
+    "": {
+      "name": "ciphercell-contact",
+      "dependencies": {
+        "nodemailer": "^7.0.13"
+      },
+      "engines": {
+        "node": ">=20"
+      }
+    },
+    "node_modules/nodemailer": {
+      "version": "7.0.13",
+      "resolved": "https://registry.npmjs.org/nodemailer/-/nodemailer-7.0.13.tgz",
+      "integrity": "sha512-PNDFSJdP+KFgdsG3ZzMXCgquO7I6McjY2vlqILjtJd0hy8wEvtugS9xKRF2NWlPNGxvLCXlTNIae4serI7dinw==",
+      "license": "MIT-0",
+      "engines": {
+        "node": ">=6.0.0"
+      }
+    }
+  }
+}

server/package.json

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+{
+  "name": "ciphercell-contact",
+  "private": true,
+  "type": "module",
+  "description": "Receives the contact form and sends it on by SMTP. Runs next to nginx; see README.",
+  "scripts": {
+    "start": "node contact.mjs"
+  },
+  "engines": {
+    "node": ">=20"
+  },
+  "dependencies": {
+    "nodemailer": "^7.0.13"
+  }
+}