Step-up auth for transfers/wires/payments

A session token that grants access to wire transfers and payments is the highest-value credential in a financial application. If that token is stolen — via XSS, network interception, or session fixation — the attacker can execute high-value transactions without any additional authentication barrier. Step-up authentication requires a second proof-of-identity at the moment the sensitive operation is initiated, so a stolen token alone is insufficient. CWE-306 (Missing Authentication for Critical Function), OWASP A07, PCI-DSS Req 8.4, and NIST 800-63B IA-11 all address this gap. Without server-side step-up enforcement, client-side UI guards are trivially bypassed with a direct API call.

Enforce step-up via server-side middleware, not client state, in src/middleware/requireStepUp.ts:

export async function requireStepUp(req: Request): Promise<Response | null> {
  const session = await getSession(req);
  const verified = await checkStepUpStatus(session.id);
  if (!verified) {
    return Response.json(
      { error: 'Step-up authentication required' },
      { status: 403 }
    );
  }
  return null; // proceed
}

// src/app/api/transfer/route.ts
export async function POST(req: Request) {
  const block = await requireStepUp(req);
  if (block) return block;
  // safe to process transfer
}

Apply requireStepUp to every sensitive route: transfers, wires, payments, account changes, and password resets. Do not rely on a client-side flag or cookie indicating that step-up was completed — verify the server-side step-up record on every request.

• ID: finserv-session-security.step-up-auth.step-up-sensitive-ops
• Severity: high
• What to look for: Enumerate all sensitive financial operation endpoints (transfers, wires, payments, account changes, password reset) and count every endpoint that has server-side step-up middleware. Quote the actual step-up verification function found. An endpoint that only checks client-side step-up state does not count as pass — do not pass if step-up is client-only.
• Pass criteria: At least 90% of sensitive financial operation endpoints have server-side step-up authentication middleware. Count all sensitive endpoints — report the ratio even on pass (e.g., "5 of 5 sensitive endpoints require step-up: /api/transfer, /api/wire, /api/payment, /api/account/change, /api/password/reset").
• Fail criteria: Any sensitive operation can be executed with only the current session token and no additional authentication challenge, or step-up is client-side only.
• Skip (N/A) when: The application has no operations classified as sensitive — cite the actual routes found.
• Detail on fail: "2 of 5 sensitive endpoints lack step-up — POST /api/transfer and POST /api/wire have session-only auth. 0 step-up middleware found on these routes."
• Cross-reference: Check finserv-session-security.step-up-auth.step-up-strength-equivalent for strength requirements, and finserv-session-security.session-integrity.suspicious-activity-step-up for anomaly-triggered step-up.
• Remediation: Add step-up auth middleware for sensitive routes (in src/middleware/requireStepUp.ts):

  // middleware/requireStepUp.ts
  export async function requireStepUp(req: Request) {
    const session = await getSession(req);
    const stepUpVerified = await checkStepUpStatus(session.id);
    if (!stepUpVerified) {
      return Response.json({ error: 'Step-up authentication required' }, { status: 403 });
    }
  }
  
  // app/api/transfer/route.ts
  export async function POST(req: Request) {
    await requireStepUp(req); // Enforces step-up before processing
    const { fromAccount, toAccount, amount } = await req.json();
    // Process transfer
  }