fix: gate admin routes against cross-origin CSRF

app/api/admin/audit/route.ts

@@ -8,7 +8,7 @@ import { logger } from '@/lib/logger';
  */
 export async function GET(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const page = Math.max(1, parseInt(request.nextUrl.searchParams.get('page') || '1', 10));

app/api/admin/branding/route.ts

@@ -44,7 +44,7 @@ function sanitizeFilename(name: string): string {
  */
 export async function POST(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const ip = getClientIP(request);
@@ -114,7 +114,7 @@ export async function POST(request: NextRequest) {
  */
 export async function DELETE(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const ip = getClientIP(request);

app/api/admin/change-password/route.ts

@@ -9,7 +9,7 @@ import { logger } from '@/lib/logger';
  */
 export async function POST(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const ip = getClientIP(request);

app/api/admin/config/route.ts

@@ -20,9 +20,9 @@ const SENSITIVE_PLACEHOLDERS = new Set(['your-secret-key-here']);
  * the server so that an XSS or session-theft can't lift them in one
  * request and forge admin/user session cookies offline.
  */
-export async function GET() {
+export async function GET(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     await configManager.ensureLoaded();
@@ -54,7 +54,7 @@ export async function GET() {
  */
 export async function PATCH(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const ip = getClientIP(request);
@@ -109,7 +109,7 @@ export async function PATCH(request: NextRequest) {
  */
 export async function DELETE(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const ip = getClientIP(request);

app/api/admin/marketplace/[slug]/route.ts

@@ -19,11 +19,11 @@ const MAX_PREVIEW_SOURCE_LEN = 100_000;
  * Lets admins audit what they're about to install before pressing the button.
  */
 export async function GET(
-  _request: NextRequest,
+  request: NextRequest,
   { params }: { params: Promise<{ slug: string }> },
 ) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const { slug } = await params;

app/api/admin/marketplace/route.ts

@@ -28,7 +28,7 @@ const DIRECTORY_URL = process.env.EXTENSION_DIRECTORY_URL || 'https://extensions
  */
 export async function GET(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const { searchParams } = request.nextUrl;
@@ -93,7 +93,7 @@ export async function GET(request: NextRequest) {
  */
 export async function POST(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const ip = getClientIP(request);

app/api/admin/oauth/setup/route.ts

@@ -84,7 +84,7 @@ function isValidOriginUrl(value: string): boolean {
 
 export async function POST(request: NextRequest) {
   try {
-    const auth = await requireAdminAuth();
+    const auth = await requireAdminAuth(request);
     if ('error' in auth) return auth.error;
 
     const ip = getClientIP(request);

app/api/admin/plugin-approvals/route.ts

@@ -19,9 +19,9 @@ function isValidHash(s: unknown): s is string {
   return typeof s === 'string' && /^[a-f0-9]{16,128}$/i.test(s);
 }
 
-export async function GET() {
+export async function GET(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
     const entries = await listApprovals();
     return NextResponse.json({ entries }, { headers: { 'Cache-Control': 'no-store' } });
@@ -33,7 +33,7 @@ export async function GET() {
 
 export async function POST(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
     // AdminSessionPayload carries only role/iat/exp; we use a stable label
     // for the audit trail rather than a per-user identity.
@@ -62,7 +62,7 @@ export async function POST(request: NextRequest) {
 
 export async function DELETE(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
     // AdminSessionPayload carries only role/iat/exp; we use a stable label
     // for the audit trail rather than a per-user identity.

app/api/admin/plugins/[id]/config/route.ts

@@ -34,7 +34,7 @@ export async function GET(
       return NextResponse.json({ error: 'Invalid plugin ID' }, { status: 400 });
     }
 
-    const adminAuth = await requireAdminAuth();
+    const adminAuth = await requireAdminAuth(request);
     const isAdmin = !('error' in adminAuth);
 
     if (!isAdmin) {
@@ -85,7 +85,7 @@ export async function PUT(
   { params }: { params: Promise<{ id: string }> },
 ) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const { id } = await params;
@@ -139,7 +139,7 @@ export async function DELETE(
   { params }: { params: Promise<{ id: string }> },
 ) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const { id } = await params;

app/api/admin/plugins/route.ts

@@ -32,9 +32,9 @@ const SUSPICIOUS_JS_PATTERNS = [
 /**
  * GET /api/admin/plugins - List all admin-managed plugins
  */
-export async function GET() {
+export async function GET(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const [registry, devEntries] = await Promise.all([
@@ -64,7 +64,7 @@ export async function GET() {
  */
 export async function POST(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const ip = getClientIP(request);
@@ -222,7 +222,7 @@ export async function POST(request: NextRequest) {
  */
 export async function PATCH(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const ip = getClientIP(request);
@@ -264,7 +264,7 @@ export async function PATCH(request: NextRequest) {
  */
 export async function DELETE(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const ip = getClientIP(request);

app/api/admin/policy/route.ts

@@ -26,7 +26,7 @@ export async function GET() {
  */
 export async function PUT(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const ip = getClientIP(request);

app/api/admin/telemetry/route.ts

@@ -19,9 +19,9 @@ import {
  * Returns current consent + endpoint + next/last send + a live preview
  * of exactly what the next heartbeat would contain.
  */
-export async function GET() {
+export async function GET(request: NextRequest) {
   try {
-    const auth = await requireAdminAuth();
+    const auth = await requireAdminAuth(request);
     if ('error' in auth) return auth.error;
 
     const { consent, source, state } = await effectiveConsent();
@@ -61,7 +61,7 @@ export async function GET() {
  */
 export async function POST(request: NextRequest) {
   try {
-    const auth = await requireAdminAuth();
+    const auth = await requireAdminAuth(request);
     if ('error' in auth) return auth.error;
     const ip = getClientIP(request);
 

app/api/admin/themes/route.ts

@@ -16,9 +16,9 @@ import { sanitizeThemeCSS, validateThemeCSSSafety } from '@/lib/theme-loader';
 /**
  * GET /api/admin/themes - List all admin-managed themes
  */
-export async function GET() {
+export async function GET(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const registry = await getThemeRegistry();
@@ -36,7 +36,7 @@ export async function GET() {
  */
 export async function POST(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const ip = getClientIP(request);
@@ -156,7 +156,7 @@ export async function POST(request: NextRequest) {
  */
 export async function PATCH(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const ip = getClientIP(request);
@@ -193,7 +193,7 @@ export async function PATCH(request: NextRequest) {
  */
 export async function DELETE(request: NextRequest) {
   try {
-    const result = await requireAdminAuth();
+    const result = await requireAdminAuth(request);
     if ('error' in result) return result.error;
 
     const ip = getClientIP(request);

app/api/admin/version/route.ts

@@ -13,9 +13,9 @@ import {
  * GET /api/admin/version
  * Returns the cached update status, last check times, and effective config.
  */
-export async function GET() {
+export async function GET(request: NextRequest) {
   try {
-    const auth = await requireAdminAuth();
+    const auth = await requireAdminAuth(request);
     if ('error' in auth) return auth.error;
 
     const state = await loadState();
@@ -47,7 +47,7 @@ export async function GET() {
  */
 export async function POST(req: NextRequest) {
   try {
-    const auth = await requireAdminAuth();
+    const auth = await requireAdminAuth(req);
     if ('error' in auth) return auth.error;
 
     const body = (await req.json().catch(() => null)) as { action?: string } | null;

lib/admin/session.ts

@@ -81,9 +81,52 @@ export function verifyAdminSession(token: string): AdminSessionPayload | null {
 }
 
 /**
- * Validate the admin session from cookies. Returns the payload or a 401 response.
+ * CSRF gate for cookie-authed admin requests.
+ *
+ * The admin session cookie is `SameSite=Lax`, which still allows top-level
+ * cross-site POST navigations (e.g. a form auto-submitted by an attacker
+ * page the admin is tricked into visiting). Without a CSRF check, any such
+ * page can trigger arbitrary state changes carrying the admin cookie.
+ *
+ * Strategy: state-changing requests must come from the same origin. Modern
+ * browsers (since 2020) always send `Sec-Fetch-Site` and that header
+ * cannot be set by JS, so it is the authoritative signal. Older browsers
+ * fall back to `Origin`. Non-browser clients (curl, scripts) send neither
+ * header and cannot ride a victim's cookie cross-origin, so the absence
+ * of both headers is allowed.
  */
-export async function requireAdminAuth(): Promise<{ payload: AdminSessionPayload } | { error: NextResponse }> {
+export function isSameOriginRequest(request: Request): boolean {
+  const method = request.method.toUpperCase();
+  if (method === 'GET' || method === 'HEAD' || method === 'OPTIONS') return true;
+
+  const fetchSite = request.headers.get('sec-fetch-site');
+  if (fetchSite !== null) {
+    return fetchSite === 'same-origin';
+  }
+
+  const origin = request.headers.get('origin');
+  if (!origin) return true;
+
+  try {
+    const originHost = new URL(origin).host;
+    const requestHost = request.headers.get('x-forwarded-host') ?? request.headers.get('host');
+    return !!requestHost && originHost === requestHost;
+  } catch {
+    return false;
+  }
+}
+
+/**
+ * Validate the admin session from cookies. Returns the payload or a 401 response.
+ *
+ * Also rejects cross-origin state-changing requests with 403 to prevent CSRF
+ * against cookie-authenticated admin actions.
+ */
+export async function requireAdminAuth(request: Request): Promise<{ payload: AdminSessionPayload } | { error: NextResponse }> {
+  if (!isSameOriginRequest(request)) {
+    return { error: NextResponse.json({ error: 'Cross-origin request rejected' }, { status: 403 }) };
+  }
+
   const cookieStore = await cookies();
   const token = cookieStore.get(ADMIN_SESSION_COOKIE)?.value;