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🛡️ Sentinel: [HIGH] Add Content-Security-Policy and Permissions-Policy headers #148

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🛡️ Sentinel: [HIGH] Add Content-Security-Policy and Permissions-Policy headers #148

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4 changes: 4 additions & 0 deletions .jules/sentinel.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
## 2025-02-18 - [API Security Headers]
**Vulnerability:** Missing Content-Security-Policy (CSP) and Permissions-Policy headers in API responses.
**Learning:** The API server also serves the static UI in production, making CSP crucial for mitigating XSS risks. Also, `bun test` requires explicit mocks for dependencies when `node_modules` are incomplete or path mappings are broken.
**Prevention:** Enforce security headers in the central CORS/headers middleware (`applyCors`) to ensure they apply to all responses.
10 changes: 9 additions & 1 deletion src/api/server.ts
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Expand Up @@ -4240,7 +4240,7 @@ function resolveCorsOrigin(origin?: string): string | null {
return null;
}

function applyCors(
export function applyCors(
req: http.IncomingMessage,
res: http.ServerResponse,
): boolean {
Expand Down Expand Up @@ -4268,6 +4268,14 @@ function applyCors(
res.setHeader("X-Frame-Options", "DENY");
res.setHeader("X-XSS-Protection", "1; mode=block");
res.setHeader("Referrer-Policy", "strict-origin-when-cross-origin");
res.setHeader(
"Content-Security-Policy",
"default-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval' blob:; style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; img-src 'self' data: blob: https:; font-src 'self' data: https://fonts.gstatic.com; connect-src 'self' ws: wss: https:; media-src 'self' blob:; frame-ancestors 'none'; upgrade-insecure-requests",
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@gemini-code-assist gemini-code-assist bot Feb 26, 2026

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security-critical critical

The script-src directive includes 'unsafe-inline' and 'unsafe-eval', which significantly weakens the security posture against Cross-Site Scripting (XSS) attacks. These keywords allow the execution of inline scripts and dynamic code from strings, which are common XSS vectors. A strong Content Security Policy should avoid these to be effective.

To improve this:

  1. Remove 'unsafe-inline' and 'unsafe-eval' from script-src. This is the most critical change.
  2. Refactor any inline scripts (<script>...</script> or onclick="...") into separate .js files served from your origin ('self').
  3. For any inline scripts that cannot be moved, use a nonce-based or hash-based approach. This involves generating a unique nonce on the server for each request and adding it to the CSP header and the script tags.

Additionally, for even stronger security:

  • style-src also contains 'unsafe-inline', which should ideally be removed.
  • img-src and connect-src allow loading resources from any https: source, which is very broad. Consider restricting this to specific, trusted domains.
Suggested change
"default-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval' blob:; style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; img-src 'self' data: blob: https:; font-src 'self' data: https://fonts.gstatic.com; connect-src 'self' ws: wss: https:; media-src 'self' blob:; frame-ancestors 'none'; upgrade-insecure-requests",
"default-src 'self'; script-src 'self' blob:; style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; img-src 'self' data: blob: https:; font-src 'self' data: https://fonts.gstatic.com; connect-src 'self' ws: wss: https:; media-src 'self' blob:; frame-ancestors 'none'; upgrade-insecure-requests",

);
res.setHeader(
"Permissions-Policy",
"accelerometer=(), camera=(), geolocation=(), gyroscope=(), magnetometer=(), payment=(), usb=()",
);

return true;
}
Expand Down
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