ip-check: add 'auto' self public-IP mode + matcher list

src/ip-check.js

@@ -1,40 +1,98 @@
 import dns from 'dns/promises'
 
-// OFFICE_IP_CHECK supports: static IP, CIDR range, DDNS hostname, or 'disabled'
-const config = process.env.OFFICE_IP_CHECK || 'disabled'
-let cachedIP = null
-let cacheExpiry = 0
+// OFFICE_IP_CHECK: a comma-separated list of matchers — a request is "onsite"
+// if ANY matcher matches. Each matcher can be:
+//   'disabled'        → onsite check off (everyone allowed)
+//   <ip>              → exact static public IP
+//   <cidr>            → e.g. 10.4.0.0/22 (matches onsite LAN clients)
+//   <ddns-hostname>   → resolved via DNS (dynamic public IP via a DDNS service)
+//   'auto'            → detect the SITE's own public IP (no DDNS service needed)
+//
+// Typical dynamic-IP config: "10.4.0.0/22,auto"
+//   - LAN clients match the CIDR (onsite via internal DNS / LAN)
+//   - clients arriving via the public IP (NAT hairpin) match 'auto'
+//   - offsite clients (different public IP) match neither → blocked
+const raw = (process.env.OFFICE_IP_CHECK || 'disabled').trim()
+const matchers = raw.split(',').map(s => s.trim()).filter(Boolean)
+
+const TTL = 5 * 60 * 1000 // 5 min cache for dynamic lookups (auto / ddns)
+const cache = new Map()   // key → { ip, expiry }
+
+// External "what's my IP" endpoints, tried in order until one answers.
+const PUBLIC_IP_URLS = [
+  'https://api.ipify.org',
+  'https://ifconfig.co/ip',
+  'https://icanhazip.com',
+]
+
+function normalizeIP(ip) {
+  // strip IPv4-mapped IPv6 prefix (::ffff:1.2.3.4)
+  return ip?.startsWith('::ffff:') ? ip.slice(7) : ip
+}
+
+function isIPv4(s) {
+  return /^\d{1,3}(\.\d{1,3}){3}$/.test(s)
+}
 
 function ipInCidr(ip, cidr) {
   const [range, bits] = cidr.split('/')
+  if (!isIPv4(ip) || !isIPv4(range)) return false
   const mask = ~(2 ** (32 - parseInt(bits)) - 1) >>> 0
   const toInt = s => s.split('.').reduce((a, o) => (a << 8) + parseInt(o), 0) >>> 0
   return (toInt(ip) & mask) === (toInt(range) & mask)
 }
 
-async function getOfficeIP() {
-  if (config === 'disabled') return null
-  if (Date.now() < cacheExpiry && cachedIP) return cachedIP
-
-  const isHostname = /[a-zA-Z]/.test(config) && !config.includes('/')
-  if (isHostname) {
+async function fetchPublicIP() {
+  for (const url of PUBLIC_IP_URLS) {
     try {
-      const addrs = await dns.resolve4(config)
-      cachedIP = addrs[0]
-      cacheExpiry = Date.now() + 5 * 60 * 1000 // 5 min TTL
+      const ctrl = new AbortController()
+      const timer = setTimeout(() => ctrl.abort(), 4000)
+      const res = await fetch(url, { signal: ctrl.signal })
+      clearTimeout(timer)
+      if (!res.ok) continue
+      const ip = (await res.text()).trim()
+      if (isIPv4(ip)) return ip
     } catch {
-      // DNS failed — keep last known good IP rather than locking everyone out
+      // try the next endpoint
     }
-  } else {
-    cachedIP = config
-    cacheExpiry = Infinity
   }
-  return cachedIP
+  return null
+}
+
+// Resolve a dynamic matcher (auto/ddns) with caching + graceful fallback:
+// on lookup failure, keep the last known good value rather than locking out.
+async function resolveDynamic(key, resolver) {
+  const hit = cache.get(key)
+  if (hit && Date.now() < hit.expiry) return hit.ip
+  const ip = await resolver()
+  if (ip) {
+    cache.set(key, { ip, expiry: Date.now() + TTL })
+    return ip
+  }
+  return hit ? hit.ip : null // stale-but-usable fallback
 }
 
 export async function isOnsite(requestIP) {
-  if (config === 'disabled') return true
-  const officeIP = await getOfficeIP()
-  if (!officeIP) return true
-  return officeIP.includes('/') ? ipInCidr(requestIP, officeIP) : requestIP === officeIP
+  if (matchers.length === 0 || matchers.includes('disabled')) return true
+  const ip = normalizeIP(requestIP)
+  if (!ip) return false
+
+  for (const m of matchers) {
+    if (m === 'auto') {
+      const pub = await resolveDynamic('auto', fetchPublicIP)
+      if (pub && ip === pub) return true
+    } else if (m.includes('/')) {
+      if (ipInCidr(ip, m)) return true
+    } else if (/[a-zA-Z]/.test(m)) {
+      // DDNS hostname
+      const resolved = await resolveDynamic(m, async () => {
+        try { return (await dns.resolve4(m))[0] } catch { return null }
+      })
+      if (resolved && ip === resolved) return true
+    } else {
+      // exact static IP
+      if (ip === m) return true
+    }
+  }
+  return false
 }