Crlf Injection in Strapi with Api Keys

Crlf Injection occurs when untrusted input containing carriage return (CR, \r) and line feed (\n) characters is reflected into HTTP headers without sanitization. In Strapi, this can intersect with API Keys in ways that expose account takeover or information disclosure risks. Strapi’s admin panel and plugin-generated routes often rely on header-based routing or session handling, and if an API Key is echoed into a header value (e.g., via a custom header like X-API-Key) and that value is not sanitized, an attacker can inject additional headers.

Consider a scenario where a Strapi plugin uses the API Key in a header for downstream service authorization and reflects user-controlled input into the same header or another header. An attacker could provide an API Key-like value such as abc123\r\nX-Admin: true. If the value is placed into a header without validation, the injected X-Admin: true line may be processed by an upstream service or middleware, effectively elevating privileges. This becomes particularly dangerous when combined with Strapi’s role-based permissions, where an attacker might try to inject headers to bypass intended access controls or impersonate a service account.

During a black-box scan, middleBrick tests such vectors by submitting API Key values containing CR/LF sequences into parameters that influence request routing or headers. It then inspects responses for header smuggling, reflected headers, or unauthorized behavior. Because Strapi supports OpenAPI specs, middleBrick’s OpenAPI/Swagger analysis correlates spec-defined security schemes (e.g., header API Key locations) with runtime injection findings, increasing detection accuracy for misconfigurations where API Key handling intersects with header manipulation.

The LLM/AI Security checks are not directly relevant to Crlf Injection in Strapi with API Keys, but the scanner’s parallel checks—such as Input Validation, Authentication, and Property Authorization—help identify whether malformed API Key inputs trigger unexpected header parsing or authentication bypass. Findings are mapped to the OWASP API Top 10 (e.g., API1:2023 Broken Object Level Authorization when injection leads to privilege escalation) and include prioritized remediation guidance.

Remediation focuses on input validation and safe handling of API Keys. Never reflect untrusted input into HTTP headers. If you must include an API Key in headers, ensure it is strictly validated and encoded. Strapi allows custom request handling in controllers and policies; use these to sanitize values before they reach headers or downstream services.

Example 1: Safe API Key validation in a Strapi policy. This policy checks that the API Key matches an expected pattern and does not contain CR or LF characters before allowing the request to proceed.

// api::api-key-policy/api-key-policy.js
module.exports = {
  validateApiKey: (ctx) => {
    const apiKey = ctx.request.header['x-api-key'];
    if (!apiKey) {
      ctx.throw(401, 'API Key missing');
    }
    // Allow only alphanumeric and limited safe characters; reject CR/LF
    const safePattern = /^[A-Za-z0-9\-_]+$/;
    if (!safePattern.test(apiKey)) {
      ctx.throw(400, 'Invalid API Key format');
    }
    // Proceed to check against stored keys via Strapi services
    return apiKey;
  },
};

Example 2: Using the validated API Key in a service call without injecting it into headers. Instead of passing the raw key to external headers, use it as a bearer token in an Authorization header constructed safely.

// services/external-service.js
const axios = require('axios');

module.exports = {
  callExternal: async (userProvidedKey) => {
    const apiKey = userProvidedKey; // already validated by policy
    try {
      const response = await axios.get('https://external.example.com/protected', {
        headers: {
          Authorization: `Bearer ${apiKey}`, // safe construction
        },
      });
      return response.data;
    } catch (error) {
      strapi.log.error('External service call failed', { error });
      throw new Error('External service unavailable');
    }n  },
};

Example 3: If you must echo a header value for logging, ensure you do not pass untrusted input directly. Use a sanitized representation or omit the header entirely.

// api::orders/orders.js (controller snippet)
'use strict';

module.exports = {
  create: async (ctx) => {
    const apiKey = ctx.request.header['x-api-key'];
    // Validate before use
    const safeKey = apiKey.replace(/[\r\n]/g, '');
    // Do not set X-API-Key back into response headers
    ctx.response.set('X-Request-ID', safeKey); // unsafe if raw; prefer generated IDs
    // ... rest of controller logic
  },
};

Additionally, leverage Strapi’s built-in security settings: enforce strong key generation, rotate keys regularly, and use environment variables for storage. In the Dashboard, monitor scans for header injection findings; in the CLI, run middlebrick scan <url> to detect these issues early. For teams requiring continuous coverage, the Pro plan’s continuous monitoring and GitHub Action integration can fail builds if a scan detects header injection risks, helping maintain secure API Key handling across deployments.