fix: bypass cacheable-lookup when resolving localhost

validation for ipv6 was sort of broken where for example `::1` was being sent as `1`, therefore,
logins were broken. This PR fixes it by using nodejs `net.isIPv4()` & `net.isIPv6` for ipv4 and ipv6
validation.

possibly related to and fixes #795

server/index.ts

@@ -27,6 +27,7 @@ import type CacheableLookupType from 'cacheable-lookup';
 import { TypeormStore } from 'connect-typeorm/out';
 import cookieParser from 'cookie-parser';
 import csurf from 'csurf';
+import { lookup } from 'dns';
 import type { NextFunction, Request, Response } from 'express';
 import express from 'express';
 import * as OpenApiValidator from 'express-openapi-validator';
@@ -54,6 +55,19 @@ app
     const CacheableLookup = (await _importDynamic('cacheable-lookup'))
       .default as typeof CacheableLookupType;
     const cacheable = new CacheableLookup();
+
+    const originalLookup = cacheable.lookup;
+
+    // if hostname is localhost use dns.lookup instead of cacheable-lookup
+    cacheable.lookup = (...args: any) => {
+      const [hostname] = args;
+      if (hostname === 'localhost') {
+        lookup(...(args as Parameters<typeof lookup>));
+      } else {
+        originalLookup(...(args as Parameters<typeof originalLookup>));
+      }
+    };
+
     cacheable.install(http.globalAgent);
     cacheable.install(https.globalAgent);
 

server/routes/auth.ts

@@ -14,6 +14,7 @@ import { ApiError } from '@server/types/error';
 import * as EmailValidator from 'email-validator';
 import { Router } from 'express';
 import gravatarUrl from 'gravatar-url';
+import net from 'net';
 
 const authRoutes = Router();
 
@@ -271,11 +272,21 @@ authRoutes.post('/jellyfin', async (req, res, next) => {
       ? jellyfinHost.slice(0, -1)
       : jellyfinHost;
 
-    const ip = req.ip ? req.ip.split(':').reverse()[0] : undefined;
+    const ip = req.ip;
+    let clientIp;
+
+    if (ip) {
+      if (net.isIPv4(ip)) {
+        clientIp = ip;
+      } else if (net.isIPv6(ip)) {
+        clientIp = ip.startsWith('::ffff:') ? ip.substring(7) : ip;
+      }
+    }
+
     const account = await jellyfinserver.login(
       body.username,
       body.password,
-      ip
+      clientIp
     );
 
     // Next let's see if the user already exists