Open Redirect in Feathersjs with Dynamodb

An Open Redirect in a Feathersjs service that uses Dynamodb typically occurs when a client-supplied URL or redirect target is used without validation before returning a 3xx HTTP response. Because Feathersjs is a framework-agnostic layer, the redirect behavior is often implemented in a hook or a custom service method. If the target URL is taken directly from request parameters (for example, a next or redirect query/string) and passed to res.redirect() or an equivalent mechanism, an attacker can craft a URL that sends victims to arbitrary destinations.

With Dynamodb as the persistence layer, the risk is not the database itself but how data retrieved from Dynamodb is used to construct a redirect. For instance, if a service stores user-specific redirect URLs or referrer targets in a Dynamodb table and later uses that stored value in a redirect without strict validation, an attacker who can control or influence what is stored can cause an open redirect. Additionally, if API responses include a URL field from Dynamodb (such as a callback or return URL) and the client is instructed to follow that URL, the lack of server-side validation means a malicious entry in Dynamodb can compromise any user who triggers the redirect.

Feathersjs hooks that return a redirect are especially sensitive when they combine data from multiple sources (query, body, headers, and Dynamodb results). Consider a pattern where a user profile stored in Dynamodb includes a redirect_uri field used after login. If this field is not constrained to same-origin or an allowlist, and the application directly redirects to it, the combination of Feathersjs routing, hook logic, and Dynamodb-stored values creates an exploitable open redirect.

Because middleBrick scans the unauthenticated attack surface and includes checks for SSRF and related injection issues, it can flag endpoints that accept redirect inputs without strict allowlists. Note that middleBrick detects and reports such risky patterns and provides remediation guidance, but it does not automatically fix implementation logic.

To remediate open redirects when using Dynamodb in Feathersjs, validate and constrain any redirect target before using it in a response. Prefer same-origin paths or an allowlist of trusted domains, and avoid using raw user input or untrusted data from Dynamodb as the redirect target. Below are concrete code examples showing a vulnerable pattern and a fixed pattern.

Vulnerable pattern (do not use)

// Feathers service hook that uses a redirect_url from Dynamodb without validation
// Assume user record from Dynamodb contains redirect_url
app.service('auth').hooks({
  after: {
    async redirectUser(context) {
      const { redirect_url } = context.result.user; // value from Dynamodb
      // UNSAFE: direct use of external URL
      context.result.redirect = redirect_url;
      return context;
    }
  }
});

Fixed pattern with validation and allowlist

const allowedHosts = new Set(['app.example.com', 'dashboard.example.com']);

function isSameOrigin(url) {
  try {
    const u = new URL(url, 'http://localhost');
    return allowedHosts.has(u.hostname);
  } catch (err) {
    return false;
  }
}

// Feathers hook with validation
app.service('auth').hooks({
  after: {
    async redirectUser(context) {
      const { redirect_url } = context.result.user; // value from Dynamodb
      if (!redirect_url || !isSameOrigin(redirect_url)) {
        // Fallback to a safe default path
        context.result.redirect = '/dashboard';
      } else {
        context.result.redirect = redirect_url;
      }
      return context;
    }
  }
});

Client-side guidance and response shaping

Instead of relying on a redirect issued by the server, return a safe path or a boolean and let the client navigate within an allowlist. This avoids coupling Dynamodb entries to navigation decisions on the server.

// Return safe navigation target from the service
app.service('auth').hooks({
  after: {
    async loginUser(context) {
      const { return_path } = context.data; // client-supplied input
      const user = context.result.user; // data from Dynamodb
      const safePath = isSameOrigin(return_path) ? return_path : '/home';
      // Do not set context.result.redirect; send a safe location to the client
      context.result = { user, navigateTo: safePath };
      return context;
    }
  }
});

Input validation and sanitization

Use a validation library to ensure URLs conform to expected formats and are restricted to same-origin or approved domains. Never trust data stored in Dynamodb without re-validation at the point of use.

// Example using a simple validation step before redirect
function validateRedirect(input) {
  if (typeof input !== 'string') return null;
  try {
    const url = new URL(input, 'http://localhost');
    if (allowedHosts.has(url.hostname)) return url.toString();
  } catch (_) {}
  return null;
}

General security practices

• Use HTTP-only, Secure cookies for session tokens and avoid embedding redirect targets in tokens or cookies that an attacker can modify.
• Apply the principle of least privilege to Dynamodb access so that services cannot read or write unexpected attributes that could be abused for redirects.
• Log suspicious redirect attempts for monitoring, but do not rely on logging alone to prevent exploitation.