Broken Access Control in Fiber with Api Keys

Broken Access Control occurs when API endpoints do not properly enforce authorization between subjects with different privileges. In Fiber, using API keys as the sole authorization mechanism can create access control weaknesses when keys are not scoped, rotated, or validated with sufficient rigor. Unlike role-based or token-based systems, API keys are typically long-lived secrets; if they leak or are shared across environments, an attacker can impersonate any client allowed to use that key.

Endpoints that should be restricted to specific clients or roles may be inadvertently exposed if the application relies only on the presence of an API key without verifying scope, tenant, or intended consumer. For example, an endpoint like /api/admin/users might check for a key but not confirm that the key belongs to an administrative client. This becomes a BOLA/IDOR vector when object-level ownership is not checked alongside key validation.

Additionally, if the Fiber application uses middleware that attaches the API key value to the request context but does not enforce least privilege, any compromised key grants broader access than intended. A key provisioned for read-only data export could be reused to invoke state-changing methods if the route does not independently validate permissions. This intersects with BFLA/Privilege Escalation when lower-privilege keys are allowed to reach higher-privilege endpoints due to missing per-route checks.

Another scenario involves unauthenticated LLM endpoints or inventory management routes that return sensitive metadata about API usage or configurations. If these endpoints rely only on API keys that are embedded in client-side code or logs, they can be discovered and abused. The LLM/AI Security checks in middleBrick specifically flag such exposures when unauthenticated endpoints leak information that should be restricted.

Because middleBrick scans the unauthenticated attack surface, it can detect routes where API key presence is required but insufficient to prevent unauthorized access. Findings include missing per-method authorization, missing tenant validation, and missing checks for key scope against the requested action. These map to OWASP API Top 10 A01:2023 — Broken Object Level Authorization and align with relevant PCI-DSS and SOC2 controls around access management.

Remediation focuses on ensuring API keys are treated as credentials that must be validated, scoped, and monitored rather than as simple authentication tokens. In Fiber, you should centralize key validation and explicitly enforce authorization before executing business logic.

Use middleware to verify the key against a trusted store and attach a structured identity to the context. Then enforce route-level checks that consider scope and tenant, not merely the presence of a key.

import { app, Context, Next } from 'fiber';

// Example in-memory store; replace with a secure, encrypted datastore in production
interface ApiKeyRecord {
  key: string;
  scopes: string[];
  tenantId: string;
  active: boolean;
}

const apiKeys: Map = new Map([
  // key value -> metadata
  ['s3cr3tK3yTenantA', { key: 's3cr3tK3yTenantA', scopes: ['read:data', 'write:data'], tenantId: 'tenant-a', active: true }],
  ['s3cr3tK3yTenantB', { key: 's3cr3tK3yTenantB', scopes: ['read:data'], tenantId: 'tenant-b', active: true }],
]);

function ensureApiKey(ctx: Context, next: Next) {
  const supplied = ctx.get('X-API-Key');
  if (!supplied) {
    ctx.status = 401;
    ctx.body = { error: 'api_key_missing' };
    return;
  }
  const record = apiKeys.get(supplied);
  if (!record || !record.active) {
    ctx.status = 403;
    ctx.body = { error: 'invalid_api_key' };
    return;
  }
  // Attach enriched identity for downstream use
  ctx.set('x-tenant-id', record.tenantId);
  ctx.set('x-api-scopes', record.scopes.join(','));
  next();
}

// Apply globally or to specific routes
app.use(ensureApiKey);

// Scope and tenant enforcement for admin route
app.get('/api/admin/users', (ctx: Context) => {
  const tenant = ctx.get('x-tenant-id');
  const scopes = (ctx.get('x-api-scopes') || '').split(',');
  if (tenant !== 'tenant-a') {
    ctx.status = 403;
    ctx.body = { error: 'tenant_mismatch' };
    return;
  }
  if (!scopes.includes('read:data') && !scopes.includes('write:data')) {
    ctx.status = 403;
    ctx.body = { error: 'insufficient_scope' };
    return;
  }
  // Proceed with admin logic
  ctx.body = { users: [] };
});

// Least-privilege route: read-only key should not invoke writes
app.post('/api/data/export', (ctx: Context) => {
  const scopes = (ctx.get('x-api-scopes') || '').split(',');
  if (!scopes.includes('write:data')) {
    ctx.status = 403;
    ctx.body = { error: 'scope_required' };
    return;
  }
  // Perform export
  ctx.body = { exported: true };
});

Rotate keys regularly and avoid embedding them in client-side code or logs. Prefer short-lived keys where operational constraints allow, and combine API keys with additional checks such as IP allowlists or mTLS when handling sensitive operations. middleBrick’s CLI can be integrated into scripts to validate key handling patterns, and the Pro plan supports continuous monitoring to detect when keys are used in unexpected scopes or from unusual locations.