add TrustHosts middleware with exemption for healthchecks

app/Http/Kernel.php

@@ -15,6 +15,7 @@ use App\Http\Middleware\PreventRequestsDuringMaintenance;
 use App\Http\Middleware\RedirectIfAuthenticated;
 use App\Http\Middleware\ShareInertiaData;
 use App\Http\Middleware\TrimStrings;
+use App\Http\Middleware\TrustHosts;
 use App\Http\Middleware\TrustProxies;
 use App\Http\Middleware\ValidateSignature;
 use App\Http\Middleware\VerifyCsrfToken;
@@ -48,6 +49,7 @@ class Kernel extends HttpKernel
     protected $middleware = [
         ForceHttps::class,
         TrustProxies::class,
+        TrustHosts::class,
         HandleCors::class,
         PreventRequestsDuringMaintenance::class,
         ValidatePostSize::class,

app/Http/Middleware/TrustHosts.php

@@ -0,0 +1,57 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Http\Middleware;
+
+use Illuminate\Http\Middleware\TrustHosts as BaseTrustHosts;
+use Illuminate\Http\Request;
+use Symfony\Component\HttpFoundation\Response;
+
+/**
+ * Rejects requests whose Host is not trusted, preventing Host-header poisoning of
+ * generated URLs (password reset, SSO callback, invitations). Trusted = the
+ * APP_URL host and its subdomains, plus TRUSTED_HOSTS (for multi-host access such
+ * as a Tailscale name). Health-check endpoints are exempt (probed by IP).
+ */
+class TrustHosts extends BaseTrustHosts
+{
+    /**
+     * @return array<int, string|null>
+     */
+    public function hosts()
+    {
+        /** @var array<int, string> $configured */
+        $configured = config('app.trusted_hosts', []);
+
+        $extra = array_map(function (string $host): string {
+            $host = trim($host);
+
+            // "*.example.com" matches any subdomain, not the apex.
+            if (str_starts_with($host, '*.')) {
+                return '^.+\.'.preg_quote(substr($host, 2), '#').'$';
+            }
+
+            return '^'.preg_quote($host, '#').'$';
+        }, $configured);
+
+        return array_merge([$this->allSubdomainsOfApplicationUrl()], $extra);
+    }
+
+    /**
+     * @param  \Closure(Request): Response  $next
+     * @return Response
+     */
+    public function handle(Request $request, $next)
+    {
+        // Exempt health checks (probed by IP). Also reset the trusted hosts,
+        // since Octane leaks the static state across requests.
+        if ($request->is('health-check/*')) {
+            Request::setTrustedHosts([]);
+
+            return $next($request);
+        }
+
+        return parent::handle($request, $next);
+    }
+}