fix(backend): use the strong password generator for resets and enforce must_change_password (#1396)

Stable backport of 9bca4046 (main) for GHSA-h4w8-57xq-53fx.

Admin password reset generated a ~2^21-entropy password from a small
wordlist (generateReadablePassword) instead of the already-available
generateSecurePassword(16), and must_change_password was written on
reset but never checked by any route-blocking logic — a reset admin
could keep using the old/weak password indefinitely since the flag
only ever reached the frontend as a response field.

adminAuth() (backend/src/middleware/auth.js) is adapted for stable's
inline admin-lookup query (main's equivalent goes through the
sessionAccess.admin() abstraction, which doesn't exist on this branch):
both the roles-join select and its missing-roles-table fallback select
now also fetch must_change_password, and a flagged admin gets 403
MUST_CHANGE_PASSWORD on every adminAuth-gated route except
/api/admin/auth/change-password and /api/admin/auth/logout (verified
against this branch's actual routes/adminAuth.js).

resetAdminPassword() (backend/src/services/userManagementService.js)
now calls generateSecurePassword(16), which already exists on stable
with the same signature as main. generateReadablePassword itself is
left untouched since it's still used by the separate gallery-password
reset path (routes/adminEvents/resets.js).

Frontend already renders MandatoryPasswordChangeModal off
user.mustChangePassword (AdminAuthContext/AdminLayout), so this is
purely a server-side backstop, same as on main.

Co-authored-by: Paul Nothaft <[email protected]>

backend/__tests__/middleware/authMustChangePassword.test.js

@@ -0,0 +1,123 @@
+/**
+ * GHSA-h4w8-57xq-53fx enforcement half: `must_change_password` was written
+ * by the admin password-reset flow (userManagementService.resetAdminPassword)
+ * and returned in a few response payloads, but no route-blocking logic ever
+ * checked it — a reset admin could keep using the old/weak password on every
+ * protected route indefinitely. adminAuth() is now the server-side backstop:
+ * a flagged admin gets 403 MUST_CHANGE_PASSWORD on everything except the
+ * routes they need to clear the flag (change-password) or leave (logout).
+ *
+ * Mirrors the mocking shape of adminAuthRoleFallback.test.js — a stub `db`
+ * chain, no real SQLite needed, so this stays a fast unit test.
+ */
+
+const jwt = require('jsonwebtoken');
+
+jest.mock('../../src/utils/tokenRevocation', () => ({ isTokenRevoked: jest.fn().mockResolvedValue(false) }));
+jest.mock('../../src/utils/logger', () => ({ warn: jest.fn(), error: jest.fn(), debug: jest.fn(), info: jest.fn() }));
+
+let mockMustChangePassword = false;
+const mockAdminRow = { id: 7, username: 'scoped', email: '[email protected]', password_changed_at: null, role_id: 1, role_name: 'editor' };
+
+jest.mock('../../src/database/db', () => ({
+  db: () => ({
+    leftJoin() { return this; },
+    where() { return this; },
+    select() { return this; },
+    first: () => Promise.resolve({ ...mockAdminRow, must_change_password: mockMustChangePassword }),
+  }),
+}));
+
+const { adminAuth } = require('../../src/middleware/auth');
+
+const SECRET = 'test-secret-for-must-change-password';
+
+function makeReq(originalUrl) {
+  const token = jwt.sign(
+    { id: mockAdminRow.id, type: 'admin' },
+    SECRET,
+    { algorithm: 'HS256', issuer: 'picpeak-auth' },
+  );
+  return { headers: { authorization: `Bearer ${token}` }, ip: '127.0.0.1', connection: {}, originalUrl };
+}
+
+function makeRes() {
+  return {
+    statusCode: null,
+    body: null,
+    status(code) { this.statusCode = code; return this; },
+    json(payload) { this.body = payload; return this; },
+  };
+}
+
+describe('adminAuth must_change_password enforcement (GHSA-h4w8-57xq-53fx)', () => {
+  const OLD_SECRET = process.env.JWT_SECRET;
+  beforeAll(() => { process.env.JWT_SECRET = SECRET; });
+  afterAll(() => { process.env.JWT_SECRET = OLD_SECRET; });
+  beforeEach(() => { mockMustChangePassword = false; });
+
+  it('blocks an arbitrary protected route with 403 MUST_CHANGE_PASSWORD when the flag is set', async () => {
+    mockMustChangePassword = true;
+    const req = makeReq('/api/admin/dashboard/stats');
+    const res = makeRes();
+    const next = jest.fn();
+
+    await adminAuth(req, res, next);
+
+    expect(next).not.toHaveBeenCalled();
+    expect(res.statusCode).toBe(403);
+    expect(res.body).toEqual(expect.objectContaining({ code: 'MUST_CHANGE_PASSWORD' }));
+    expect(req.admin).toBeUndefined();
+  });
+
+  it('does not block when the flag is not set', async () => {
+    mockMustChangePassword = false;
+    const req = makeReq('/api/admin/dashboard/stats');
+    const res = makeRes();
+    const next = jest.fn();
+
+    await adminAuth(req, res, next);
+
+    expect(next).toHaveBeenCalled();
+    expect(req.admin.mustChangePassword).toBe(false);
+  });
+
+  it.each([
+    ['/api/admin/auth/change-password'],
+    ['/api/admin/auth/logout'],
+  ])('still allows %s through when the flag is set', async (originalUrl) => {
+    mockMustChangePassword = true;
+    const req = makeReq(originalUrl);
+    const res = makeRes();
+    const next = jest.fn();
+
+    await adminAuth(req, res, next);
+
+    expect(next).toHaveBeenCalled();
+    expect(req.admin.mustChangePassword).toBe(true);
+    expect(res.statusCode).toBeNull();
+  });
+
+  it('allows the exempt change-password path even with a query string', async () => {
+    mockMustChangePassword = true;
+    const req = makeReq('/api/admin/auth/change-password?foo=bar');
+    const res = makeRes();
+    const next = jest.fn();
+
+    await adminAuth(req, res, next);
+
+    expect(next).toHaveBeenCalled();
+  });
+
+  it('does not exempt a route that merely starts with the change-password path', async () => {
+    mockMustChangePassword = true;
+    const req = makeReq('/api/admin/auth/change-password-history');
+    const res = makeRes();
+    const next = jest.fn();
+
+    await adminAuth(req, res, next);
+
+    expect(next).not.toHaveBeenCalled();
+    expect(res.statusCode).toBe(403);
+  });
+});