feat(auth): add an admin-managed login allowlist

Lets the admin restrict which pubkeys may log in, enforced server-side
at /api/auth/login before a session is issued. Disabled by default;
the admin and the bootstrap (no-admin-claimed-yet) case always pass.
Manageable via the existing settings UI/API (npub or hex, one per line).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

server/src/app.test.ts

@@ -79,6 +79,78 @@ describe('auth', () => {
   });
 });
 
+describe('login allowlist', () => {
+  const sk2 = generateSecretKey();
+  const pk2 = getPublicKey(sk2);
+
+  function nip98Header2(url: string, method: string): string {
+    const event = finalizeEvent(
+      {
+        kind: 27235,
+        created_at: Math.floor(Date.now() / 1000),
+        content: '',
+        tags: [['u', url], ['method', method], ['nonce', Math.random().toString(36).slice(2)]],
+      },
+      sk2,
+    );
+    return `Nostr ${Buffer.from(JSON.stringify(event)).toString('base64')}`;
+  }
+
+  it('rejects a non-listed pubkey once the allowlist is enabled, admin still logs in', async () => {
+    const enable = await app.inject({
+      method: 'PUT',
+      url: '/api/settings',
+      headers: { cookie, 'content-type': 'application/json' },
+      payload: { login_allowlist_enabled: true, login_allowlist: [] },
+    });
+    expect(enable.statusCode).toBe(200);
+
+    const blocked = await app.inject({
+      method: 'POST',
+      url: '/api/auth/login',
+      headers: { authorization: nip98Header2('http://localhost:8095/api/auth/login', 'POST') },
+    });
+    expect(blocked.statusCode).toBe(403);
+
+    const adminStillIn = await app.inject({
+      method: 'POST',
+      url: '/api/auth/login',
+      headers: { authorization: nip98Header('http://localhost:8095/api/auth/login', 'POST') },
+    });
+    expect(adminStillIn.statusCode).toBe(200);
+    expect(adminStillIn.json().isAdmin).toBe(true);
+  });
+
+  it('allows a pubkey once it is added to the allowlist', async () => {
+    const update = await app.inject({
+      method: 'PUT',
+      url: '/api/settings',
+      headers: { cookie, 'content-type': 'application/json' },
+      payload: { login_allowlist: [pk2] },
+    });
+    expect(update.statusCode).toBe(200);
+    expect(update.json().login_allowlist).toEqual([pk2]);
+
+    const res = await app.inject({
+      method: 'POST',
+      url: '/api/auth/login',
+      headers: { authorization: nip98Header2('http://localhost:8095/api/auth/login', 'POST') },
+    });
+    expect(res.statusCode).toBe(200);
+    expect(res.json().pubkey).toBe(pk2);
+  });
+
+  afterAll(async () => {
+    // Leave the allowlist disabled so later describe blocks aren't affected.
+    await app.inject({
+      method: 'PUT',
+      url: '/api/settings',
+      headers: { cookie, 'content-type': 'application/json' },
+      payload: { login_allowlist_enabled: false },
+    });
+  });
+});
+
 describe('podcasts, episodes, feed', () => {
   let podcastId: string;
   const sha = 'c'.repeat(64);

server/src/routes/auth.ts

@@ -24,6 +24,9 @@ export default async function authRoutes(app: FastifyInstance) {
       if (err instanceof Nip98Error) return reply.code(401).send({ error: err.message });
       throw err;
     }
+    if (!settings.isLoginAllowed(pubkey)) {
+      return reply.code(403).send({ error: 'this account is not on the login allowlist' });
+    }
     upsertUser.run(pubkey, nowSecs(), nowSecs());
     settings.claimAdminIfUnset(pubkey);
 

server/src/routes/settings.ts

@@ -6,6 +6,8 @@ const updateSchema = z.object({
   relays: z.array(z.string().regex(/^wss?:\/\//)).optional(),
   public_url: z.string().url().optional(),
   cashu_mint_url: z.string().url().optional(),
+  login_allowlist_enabled: z.boolean().optional(),
+  login_allowlist: z.array(z.string().regex(/^[0-9a-f]{64}$/i)).optional(),
 });
 
 export default async function settingsRoutes(app: FastifyInstance) {
@@ -33,11 +35,24 @@ export default async function settingsRoutes(app: FastifyInstance) {
     }
     const parsed = updateSchema.safeParse(req.body);
     if (!parsed.success) return reply.code(400).send({ error: parsed.error.message });
-    const { blossom_url, relays, public_url, cashu_mint_url } = parsed.data;
+    const {
+      blossom_url,
+      relays,
+      public_url,
+      cashu_mint_url,
+      login_allowlist_enabled,
+      login_allowlist,
+    } = parsed.data;
     if (blossom_url !== undefined) settings.set('blossom_url', blossom_url);
     if (relays !== undefined) settings.set('relays', JSON.stringify(relays));
     if (public_url !== undefined) settings.set('public_url', public_url);
     if (cashu_mint_url !== undefined) settings.set('cashu_mint_url', cashu_mint_url);
+    if (login_allowlist_enabled !== undefined) {
+      settings.set('login_allowlist_enabled', login_allowlist_enabled ? 'true' : 'false');
+    }
+    if (login_allowlist !== undefined) {
+      settings.set('login_allowlist', JSON.stringify(login_allowlist.map((pk) => pk.toLowerCase())));
+    }
     return settings.all();
   });
 }

server/src/services/settings.ts

@@ -7,6 +7,8 @@ export interface Settings {
   public_url: string;
   admin_pubkey: string | null;
   cashu_mint_url: string;
+  login_allowlist_enabled: boolean;
+  login_allowlist: string[];
 }
 
 export class SettingsService {
@@ -32,6 +34,8 @@ export class SettingsService {
       public_url: this.get('public_url') ?? this.config.PUBLIC_URL,
       admin_pubkey: this.get('admin_pubkey'),
       cashu_mint_url: this.get('cashu_mint_url') ?? this.config.CASHU_MINT_URL_DEFAULT,
+      login_allowlist_enabled: this.get('login_allowlist_enabled') === 'true',
+      login_allowlist: JSON.parse(this.get('login_allowlist') ?? '[]'),
     };
   }
 
@@ -64,4 +68,17 @@ export class SettingsService {
   isAdmin(pubkey: string): boolean {
     return this.get('admin_pubkey') === pubkey;
   }
+
+  /**
+   * Whether a pubkey may log in. Disabled by default (everyone allowed). When enabled,
+   * the admin and no-admin-claimed-yet bootstrap case always pass, otherwise the pubkey
+   * must be in the allowlist.
+   */
+  isLoginAllowed(pubkey: string): boolean {
+    if (this.get('login_allowlist_enabled') !== 'true') return true;
+    if (!this.get('admin_pubkey')) return true;
+    if (this.isAdmin(pubkey)) return true;
+    const list: string[] = JSON.parse(this.get('login_allowlist') ?? '[]');
+    return list.includes(pubkey);
+  }
 }