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Security: Guddy0101/StellarEduPay

Security

docs/security.md

Security

Content Security Policy (CSP)

StellarEduPay enforces a Content Security Policy on all HTTP responses to mitigate XSS attacks. The policy is applied at two layers: the Next.js frontend and the Express backend.

Threat model

Without CSP, a successful XSS injection (e.g. a malicious student name rendered in the dashboard) can execute arbitrary JavaScript in the admin's browser, steal the JWT from localStorage, and exfiltrate school data. CSP prevents this by restricting which scripts, styles, and network destinations the browser will allow.

Frontend CSP (frontend/next.config.js)

Applied to every HTML response via the Next.js headers() API:

Content-Security-Policy:
  default-src 'self';
  script-src  'self';
  style-src   'self';
  img-src     'self' data:;
  font-src    'self';
  connect-src 'self' https://horizon-testnet.stellar.org https://horizon.stellar.org;
  object-src  'none';
  frame-ancestors 'none';
  base-uri    'self';
  form-action 'self'
Directive Value Rationale
default-src 'self' Deny all unlisted resource types by default
script-src 'self' No inline scripts, no eval, no third-party JS
style-src 'self' No inline styles, no third-party CSS
img-src 'self' data: Allows inline SVG/base64 images used by the UI
font-src 'self' Self-hosted fonts only
connect-src 'self' https://horizon-testnet.stellar.org https://horizon.stellar.org Allows fetch/XHR to the backend API and both Stellar Horizon endpoints
object-src 'none' Blocks Flash and other plugins
frame-ancestors 'none' Prevents clickjacking (equivalent to X-Frame-Options: DENY)
base-uri 'self' Prevents base-tag hijacking
form-action 'self' Restricts form submissions to the same origin

Additional security headers set alongside CSP:

Header Value
X-Frame-Options DENY
X-Content-Type-Options nosniff
Referrer-Policy strict-origin-when-cross-origin

Backend CSP (backend/src/app.js)

The Express backend serves only JSON API responses — directives for scripts, styles, and images are irrelevant. Helmet is configured with a minimal policy appropriate for an API:

helmet({
  contentSecurityPolicy: {
    directives: {
      defaultSrc: ["'none'"],
      frameAncestors: ["'none'"],
    },
  },
})

default-src 'none' means the browser should load nothing from this origin as a document resource. frame-ancestors 'none' prevents the API responses from being embedded in frames.

Verification

The CSP configuration is covered by tests/csp.test.js, which verifies:

  • The frontend next.config.js exports a headers() function returning a catch-all entry with a Content-Security-Policy header.
  • The frontend CSP includes default-src 'self', script-src 'self', frame-ancestors 'none', object-src 'none', and the Stellar Horizon connect-src allowlist.
  • The frontend CSP does not contain 'unsafe-inline' or 'unsafe-eval'.
  • The backend app.js sets defaultSrc: ["'none'"] and frameAncestors: ["'none'"] and does not include scriptSrc, styleSrc, imgSrc, 'unsafe-inline', or 'unsafe-eval'.

Run the tests with:

npm test -- tests/csp.test.js

Adding new external origins

If a new external service needs to be reachable from the frontend (e.g. a currency conversion API), add its origin to the connect-src directive in frontend/next.config.js and update the test in tests/csp.test.js accordingly.

Do not add 'unsafe-inline' or 'unsafe-eval' to script-src. If a third-party library requires inline scripts, use a nonce-based approach instead.

There aren't any published security advisories