fix: Client-IP haerten (CF-Connecting-IP, X-Real-IP, Admin-Session)

- CF-Connecting-IP gilt nur noch als oeffentliche Unicast-Adresse
  (nicht 0/8, 10/8, 100.64/10, 127/8, 169.254/16, 172.16/12,
  192.168/16, 240/4, Broadcast, ::, ::1, fc00::/7, fe80::/10,
  ::ffff:privat); sonst gilt die Gegenstelle.
- X-Real-IP ohne X-Forwarded-For nur noch ausserhalb von Produktion;
  in Produktion ergibt das "unknown".
- Neuer Helfer headersWithClientIp, von withClientIp und der
  Admin-Session-Pruefung genutzt: ein vom Client gesendeter
  x-artista-client-ip-Wert wird nie geglaubt.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

src/lib/admin-auth.ts

@@ -7,6 +7,7 @@ import { headers } from "next/headers";
 import { redirect } from "next/navigation";
 import type { Actor } from "./audit";
 import { getAuth } from "./auth";
+import { headersWithClientIp } from "./rate-limit";
 
 export type AdminUser = { id: string; email: string; name: string; twoFactorEnabled: boolean };
 
@@ -15,7 +16,7 @@ async function currentAdmin(): Promise<AdminUser | null> {
   // Sonst versucht "next build" sie vorab zu rendern und scheitert ohne
   // Secrets im Container (getAuth() braucht BETTER_AUTH_SECRET).
   const requestHeaders = await headers();
-  const session = await getAuth().api.getSession({ headers: requestHeaders });
+  const session = await getAuth().api.getSession({ headers: headersWithClientIp(requestHeaders) });
   if (!session) return null;
   const user = session.user as typeof session.user & { twoFactorEnabled?: boolean | null };
   return { id: user.id, email: user.email, name: user.name, twoFactorEnabled: Boolean(user.twoFactorEnabled) };

src/lib/rate-limit.ts

@@ -67,6 +67,26 @@ const CLOUDFLARE: [string, number, "ipv4" | "ipv6"][] = [
 const cloudflare = new BlockList();
 for (const [net, prefix, family] of CLOUDFLARE) cloudflare.addSubnet(net, prefix, family);
 
+/** Nicht oeffentliche Bereiche; 240/4 nutzt Cloudflare fuer "Pseudo IPv4". */
+const NON_PUBLIC_V4 = ["0.0.0.0/8", "10.0.0.0/8", "100.64.0.0/10", "127.0.0.0/8", "169.254.0.0/16", "172.16.0.0/12", "192.168.0.0/16", "240.0.0.0/4"];
+const nonPublic = new BlockList();
+for (const cidr of NON_PUBLIC_V4) nonPublic.addSubnet(cidr.split("/")[0]!, Number(cidr.split("/")[1]), "ipv4");
+nonPublic.addAddress("255.255.255.255", "ipv4");
+nonPublic.addAddress("::", "ipv6");
+nonPublic.addAddress("::1", "ipv6");
+nonPublic.addSubnet("fc00::", 7, "ipv6");
+nonPublic.addSubnet("fe80::", 10, "ipv6");
+
+function isPublicUnicast(ip: string): boolean {
+  if (isIP(ip) === 4) return !nonPublic.check(ip, "ipv4");
+  const groups = ipv6Groups(ip);
+  if (groups.slice(0, 5).every((group) => group === 0) && groups[5] === 0xffff) {
+    const [high = 0, low = 0] = groups.slice(6);
+    return !nonPublic.check([high >> 8, high & 0xff, low >> 8, low & 0xff].join("."), "ipv4");
+  }
+  return !nonPublic.check(ip, "ipv6");
+}
+
 function validIp(value: string | null | undefined): string | null {
   const ip = value?.trim();
   return ip && isIP(ip) ? ip : null;
@@ -82,10 +102,11 @@ function validIp(value: string | null | undefined): string | null {
  */
 export function clientIp(headers: Headers): string {
   const forwarded = headers.get("x-forwarded-for");
-  const peer = forwarded === null ? validIp(headers.get("x-real-ip")) : validIp(forwarded.split(",").at(-1));
+  const realIp = process.env.NODE_ENV === "production" ? null : validIp(headers.get("x-real-ip"));
+  const peer = forwarded === null ? realIp : validIp(forwarded.split(",").at(-1));
   if (!peer) return "unknown";
   const viaCloudflare = validIp(headers.get("cf-connecting-ip"));
-  return viaCloudflare && cloudflare.check(peer, isIP(peer) === 6 ? "ipv6" : "ipv4") ? viaCloudflare : peer;
+  return viaCloudflare && isPublicUnicast(viaCloudflare) && cloudflare.check(peer, isIP(peer) === 6 ? "ipv6" : "ipv4") ? viaCloudflare : peer;
 }
 
 /** Die acht 16-Bit-Gruppen einer gueltigen IPv6-Adresse; eine IPv4-Endung (::ffff:a.b.c.d) wird umgerechnet. */
@@ -119,9 +140,14 @@ export function rateLimitSubject(ip: string): string {
   return `${groups.slice(0, 4).map((group) => group.toString(16)).join(":")}::/64`;
 }
 
+/** Kopie der Header mit CLIENT_IP_HEADER aus clientIp(); ein mitgeschickter Wert wird ersetzt. */
+export function headersWithClientIp(source: Headers): Headers {
+  const headers = new Headers(source);
+  headers.set(CLIENT_IP_HEADER, clientIp(source));
+  return headers;
+}
+
 /** Kopie der Anfrage mit CLIENT_IP_HEADER aus clientIp(); ein mitgeschickter Wert wird ersetzt. */
 export function withClientIp(request: Request): Request {
-  const headers = new Headers(request.headers);
-  headers.set(CLIENT_IP_HEADER, clientIp(request.headers));
-  return new Request(request, { headers });
+  return new Request(request, { headers: headersWithClientIp(request.headers) });
 }