| 1 | /** |
| 2 | * The headers every answer from the site carries, and the policy its pages |
| 3 | * run under. No Workers imports, so it can be tested under Node. |
| 4 | * |
| 5 | * - Nothing is sniffed: a download or a data request is only the type it says. |
| 6 | * - A link to another site sends the origin, never the path. |
| 7 | * - No other site may put g1t's pages in a frame. |
| 8 | * - A page runs only the scripts the site served it: its own files, and the |
| 9 | * inline scripts React and React Router write, each carrying the page's |
| 10 | * nonce. Styles may be inline (highlighting and layout set them); images |
| 11 | * may come from any HTTPS address (pictures in a README); requests may go |
| 12 | * to any HTTPS address (the status page's summary). |
| 13 | */ |
| 14 | |
| 15 | /** A fresh nonce for one page: 128 random bits, base64. */ |
| 16 | export function makeNonce(): string { |
| 17 | const bytes = crypto.getRandomValues(new Uint8Array(16)); |
| 18 | return btoa(String.fromCharCode(...bytes)); |
| 19 | } |
| 20 | |
| 21 | /** The Content-Security-Policy of a page rendered with `nonce`. */ |
| 22 | export function pagePolicy(nonce: string): string { |
| 23 | return [ |
| 24 | "default-src 'self'", |
| 25 | // Cloudflare's Web Analytics beacon, when the zone turns it on. |
| 26 | `script-src 'self' 'nonce-${nonce}' https://static.cloudflareinsights.com`, |
| 27 | "style-src 'self' 'unsafe-inline'", |
| 28 | "img-src 'self' https: data: blob:", |
| 29 | "media-src 'self' https:", |
| 30 | "font-src 'self' data:", |
| 31 | "connect-src 'self' https:", |
| 32 | "frame-src 'none'", |
| 33 | "object-src 'none'", |
| 34 | "base-uri 'self'", |
| 35 | "frame-ancestors 'none'", |
| 36 | ].join("; "); |
| 37 | } |
| 38 | |
| 39 | /** |
| 40 | * The answer with the site's headers added. A header the answer already |
| 41 | * has is kept. An upgrade to a WebSocket is passed on as it is. |
| 42 | */ |
| 43 | export function withSiteHeaders(response: Response): Response { |
| 44 | if (response.status === 101 || (response as Response & { webSocket?: unknown }).webSocket) return response; |
| 45 | // A redirect's headers cannot be changed, so the answer is copied. |
| 46 | const answer = new Response(response.body, response); |
| 47 | const headers = answer.headers; |
| 48 | if (!headers.has("x-content-type-options")) headers.set("x-content-type-options", "nosniff"); |
| 49 | if (!headers.has("referrer-policy")) headers.set("referrer-policy", "strict-origin-when-cross-origin"); |
| 50 | if (/^text\/html\b/i.test(headers.get("content-type") ?? "") && !headers.has("x-frame-options")) { |
| 51 | headers.set("x-frame-options", "DENY"); |
| 52 | } |
| 53 | return answer; |
| 54 | } |