mirror of
https://github.com/willchen96/mike.git
synced 2026-06-10 20:35:12 +02:00
eb4414092e
Resolves the issue where getSecret() silently fell back to the literal string "dev-secret" when neither DOWNLOAD_SIGNING_SECRET nor SUPABASE_SECRET_KEY was set. Because the codebase is public, that fallback let anyone forge valid /download/:token signatures against a mis-configured deployment. - Throw at first call instead of returning the hardcoded string, with a message pointing the operator at `openssl rand -hex 32`. - Document DOWNLOAD_SIGNING_SECRET in backend/.env.example so deployers following the README know to set it (and that it should be distinct from SUPABASE_SECRET_KEY). Closes #7
83 lines
2.5 KiB
TypeScript
83 lines
2.5 KiB
TypeScript
import crypto from "crypto";
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/**
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* HMAC-signed, non-expiring download tokens.
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*
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* The token encodes the R2 storage path + filename; the backend route
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* `/download/:token` validates the signature and streams the file. This
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* gives persistent links safe to store in chat history without signed-URL
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* expiry or R2 CORS headaches.
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*/
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function getSecret(): string {
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const secret =
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process.env.DOWNLOAD_SIGNING_SECRET ??
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process.env.SUPABASE_SECRET_KEY;
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if (!secret) {
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throw new Error(
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"DOWNLOAD_SIGNING_SECRET (or SUPABASE_SECRET_KEY as a fallback) must be set. " +
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"Generate a strong random value (e.g. `openssl rand -hex 32`) and set it in the environment.",
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);
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}
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return secret;
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}
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function b64urlEncode(buf: Buffer): string {
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return buf
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.toString("base64")
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.replace(/\+/g, "-")
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.replace(/\//g, "_")
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.replace(/=+$/g, "");
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}
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function b64urlDecode(s: string): Buffer {
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let t = s.replace(/-/g, "+").replace(/_/g, "/");
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while (t.length % 4) t += "=";
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return Buffer.from(t, "base64");
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}
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function timingSafeEqStr(a: string, b: string): boolean {
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if (a.length !== b.length) return false;
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return crypto.timingSafeEqual(Buffer.from(a), Buffer.from(b));
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}
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export function signDownload(path: string, filename: string): string {
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const payload = JSON.stringify({ p: path, f: filename });
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const enc = b64urlEncode(Buffer.from(payload, "utf8"));
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const sig = crypto
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.createHmac("sha256", getSecret())
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.update(enc)
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.digest();
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return `${enc}.${b64urlEncode(sig)}`;
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}
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export function verifyDownload(
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token: string,
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): { path: string; filename: string } | null {
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const parts = token.split(".");
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if (parts.length !== 2) return null;
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const [enc, sigEnc] = parts;
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const expected = crypto
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.createHmac("sha256", getSecret())
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.update(enc)
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.digest();
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if (!timingSafeEqStr(sigEnc, b64urlEncode(expected))) return null;
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try {
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const parsed = JSON.parse(b64urlDecode(enc).toString("utf8")) as {
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p: string;
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f: string;
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};
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if (!parsed?.p || !parsed?.f) return null;
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return { path: parsed.p, filename: parsed.f };
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} catch {
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return null;
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}
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}
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/**
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* Returns a relative download URL (e.g. "/download/abc.def"). The frontend
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* prefixes it with NEXT_PUBLIC_API_BASE_URL when rendering `<a href=…>`.
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*/
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export function buildDownloadUrl(path: string, filename: string): string {
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return `/download/${signDownload(path, filename)}`;
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}
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