Out Of Bounds Read in Feathersjs with Api Keys

An Out Of Bounds Read occurs when an application reads memory or data beyond the intended allocation boundary. In FeathersJS applications that use Api Keys for service authentication, this typically arises when array or buffer indices derived from user-controlled input are not properly validated before being used to access collections or buffers. If an API key–based authorization layer uses an unchecked index—such as iterating over allowed keys with an attacker-supplied numeric parameter—it can read past the end of the array and potentially leak adjacent memory contents or trigger undefined behavior.

Consider a FeathersJS service that maps incoming Api Keys to permissions using a zero-indexed array. If the code computes an index from an unvalidated numeric query parameter or header without verifying that it falls within the array length, an out-of-bounds read can occur. For example, using a parameter like keyIndex directly as an array position enables reading beyond the stored keys, which may expose other service configuration data or process memory depending on runtime and language specifics. This pattern is especially risky when the service relies on unauthenticated endpoints or public routes where an attacker can probe numeric indices without needing prior authentication.

Because FeathersJS often exposes data as REST or GraphQL-like interfaces, an out-of-bounds read can be chained with weak authorization checks—such as missing or misconfigured Api Key validation—to reach across logical boundaries. The framework does not inherently prevent such index misuse; developers must ensure that any lookup based on Api Keys or derived indices is bounded and type-safe. Real-world manifestations may include information disclosure through error messages or indirect data leaks when the runtime returns adjacent buffer contents. The vulnerability is not in Api Keys themselves but in how their associated metadata is accessed and indexed.

In the context of the 12 security checks run by middleBrick, an out-of-bounds read related to Api Keys may surface under Property Authorization, Input Validation, or Unsafe Consumption. These checks analyze runtime behavior against known attack patterns, including OWASP API Top 10 risks such as Broken Object Level Authorization. Because the scan is unauthenticated and probes public endpoints, it can detect anomalies where numeric identifiers lead to irregular data exposure without requiring credentials.

Using middleBrick’s OpenAPI/Swagger analysis, such issues can be cross-referenced between the spec definition and runtime findings. If the spec defines an keyIndex parameter as an integer with no range constraints, and runtime tests show that the endpoint returns different data when this parameter traverses array boundaries, the scanner can flag this as a high-risk finding. Developers receive prioritized remediation guidance that emphasizes input validation and strict bounds checking rather than assuming framework-level protection.

Remediation focuses on ensuring that any use of Api Keys and related indices is bounded and validated before accessing arrays or buffers. Replace numeric index-based lookups with map-based key access where possible, and enforce strict type and range checks when indices are necessary. Below are concrete FeathersJS code examples demonstrating secure patterns.

Example 1: Safe Api Key lookup using a Map

Instead of using an array index derived from user input, store keys in a JavaScript Map and validate presence before access.

const { Forbidden } = require('@feathersjs/errors');

const apiKeys = new Map([
  ['ak_live_abc123', { scope: 'read-write', owner: 'service-a' }],
  ['ak_test_xyz789', { scope: 'read-only', owner: 'service-b' }]
]);

app.use('/secure', {
  before: {
    all: [context => {
      const key = context.params.headers['x-api-key'];
      if (!key || !apiKeys.has(key)) {
        throw new Forbidden('Invalid or missing Api Key');
      }
      // Attach key metadata safely without index-based access
      context.params.keyInfo = apiKeys.get(key);
      return context;
    }]
  }
});

Example 2: Validated numeric index access with boundary checks

If you must use numeric indices, validate the index against the array length and reject out-of-range values explicitly.

const permissions = [
  { role: 'admin', services: ['all'] },
  { role: 'member', services: ['read'] }
];

app.use('/roles', {
  before: {
    all: [context => {
      const requestedIndex = Number(context.query.index);
      if (!Number.isInteger(requestedIndex) || requestedIndex < 0 || requestedIndex >= permissions.length) {
        throw new Forbidden('Invalid index');
      }
      context.result = permissions[requestedIndex];
      return context;
    }]
  }
});

Example 3: Middleware to reject non-integer and out-of-bounds parameters

Add a reusable hook that ensures numeric query or path parameters are within expected bounds before any data access occurs.

function validateIndexParam(max) {
  return context => {
    const raw = context.params.query?.index ?? context.params.route?.index;
    const idx = Number(raw);
    if (!Number.isInteger(idx) || idx < 0 || idx >= max) {
      throw new Forbidden('Index out of bounds');
    }
    return context;
  };
}

// Usage in a FeathersJS service hook
app.use('/items', {
  before: {
    all: [validateIndexParam(2)] // Only allow indices 0 and 1
  }
});

General hardening recommendations

• Always treat user-supplied indices as untrusted input; validate type, integer-ness, and range.
• Use maps or object key lookups instead of numeric indices when the key is directly available (e.g., the Api Key string itself).
• Ensure error messages do not disclose memory layout or adjacent data, which could aid an attacker in an out-of-bounds read scenario.
• Leverage middleBrick’s CLI or Web Dashboard to continuously test for improper bounds handling, especially when endpoints accept numeric identifiers related to authorization metadata.