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fix(csp): warn when useNonce falls back to unsafe-inline #3881

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fix(csp): warn when useNonce falls back to unsafe-inline #3881

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11 changes: 11 additions & 0 deletions packages/fresh/src/middlewares/csp.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -129,6 +129,17 @@ export function csp<State>(options: CSPOptions = {}): Middleware<State> {
return d;
});
} else {
// The route returned a response without going through ctx.render(),
// so Fresh never attached a nonce. The merged directives still
// contain 'unsafe-inline' for script-src / style-src and the user's
// intent (useNonce: true) was a locked-down policy — warn loudly so
// they know the handler needs to switch to ctx.render().
// deno-lint-ignore no-console
console.warn(
`🍋 [fresh] csp middleware: useNonce is true but the response ${
ctx.url.pathname
} has no nonce (handler likely returned ctx.html/ctx.json/ctx.text instead of ctx.render). Falling back to 'unsafe-inline'.`,
);
directives = merged;
}

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54 changes: 54 additions & 0 deletions packages/fresh/src/middlewares/csp_test.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -165,6 +165,60 @@ Deno.test("CSP - useNonce with non-rendered response falls back to unsafe-inline
expect(cspHeader).toContain("'unsafe-inline'");
});

Deno.test("CSP - useNonce with non-rendered response warns the developer", async () => {
const warnings: string[] = [];
const original = console.warn;
// deno-lint-ignore no-console
console.warn = (msg: string) => {
warnings.push(String(msg));
};
try {
const app = new App()
.use(csp({ useNonce: true }))
.get("/api", () => new Response(JSON.stringify({ ok: true })));
const server = new FakeServer(app.handler());
const res = await server.get("/api");
await res.body?.cancel();
} finally {
// deno-lint-ignore no-console
console.warn = original;
}

expect(warnings).toHaveLength(1);
expect(warnings[0]).toContain("/api");
expect(warnings[0]).toContain("useNonce is true");
expect(warnings[0]).toContain("unsafe-inline");
});

Deno.test("CSP - useNonce with rendered response does not warn", async () => {
const warnings: string[] = [];
const original = console.warn;
// deno-lint-ignore no-console
console.warn = (msg: string) => {
warnings.push(String(msg));
};
try {
const app = new App()
.use(csp({ useNonce: true }))
.get("/", (ctx) => {
return ctx.render(
<html>
<head />
<body>hello</body>
</html>,
);
});
const server = new FakeServer(app.handler());
const res = await server.get("/");
await res.body?.cancel();
} finally {
// deno-lint-ignore no-console
console.warn = original;
}

expect(warnings).toHaveLength(0);
});

Deno.test("CSP - useNonce generates unique nonce per request", async () => {
const app = new App()
.use(csp({ useNonce: true }))
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