Haketilo

 * IMPORT csp_rule

    let csp_headers;

    let old_signature;

    let hachette_header;

    for (const header of headers.filter(h => h.name === "x-hachette")) {

	/* x-hachette header has format: <signature>_0_<data> */

	const match = /^([^_]+)_(0_.*)$/.exec(header.value);

	if (!match)

	    continue;

	const result = extract_signed(...match.slice(1, 3));

	if (result.fail)

	    continue;

	/* This should succeed - it's our self-produced valid JSON. */

	const old_data = JSON.parse(decodeURIComponent(result.data));

	/* Confirmed- it's the originals, smuggled in! */

	csp_headers = old_data.csp_headers;

	old_signature = old_data.policy_sig;

	hachette_header = header;

	break;

    }

    if (!hachette_header) {

	hachette_header = {name: "x-hachette"};

	headers.push(hachette_header);

    csp_headers = csp_headers ||

	headers.filter(h => is_csp_header_name(h.name));

    /* When blocking remove report-only CSP headers that snitch on us. */

    headers = headers.filter(h => !is_csp_header_name(h.name, !policy.allow));

    if (old_signature)

	headers = headers.filter(h => h.value.search(old_signature) === -1);

    headers.push(...csp_headers.map(h => sanitize_csp_header(h, policy)));

    /*

     * Smuggle in the signature and the original CSP headers for future use.

     * These are signed with a time of 0, as it's not clear there is a limit on

     * how long Firefox might retain headers in the cache.

     */

    let hachette_data = {csp_headers, policy_sig: signed_policy[0]};

    hachette_data = encodeURIComponent(JSON.stringify(hachette_data));

    hachette_header.value = sign_data(hachette_data, 0).join("_");

    /* To ensure there is a CSP header if required */

    if (!policy.allow)

	headers.push({

	    name: "content-security-policy",

	    value: csp_rule(policy.nonce)

	});