Haketilo

/**

 * Hachette injecting policy to page using webRequest

 *

 * Copyright (C) 2021 Wojtek Kosior

 * Copyright (C) 2021 jahoti

 * Redistribution terms are gathered in the `copyright' file.

 */

/*

 * IMPORTS_START

 * IMPORT get_storage

 * IMPORT browser

 * IMPORT is_chrome

 * IMPORT gen_nonce

 * IMPORT is_privileged_url

 * IMPORT sign_data

 * IMPORT extract_signed

 * IMPORT query_best

 * IMPORT sanitize_csp_header

 * IMPORT csp_rule

 * IMPORT is_csp_header_name

 * IMPORTS_END

 */

var storage;

function headers_inject(details)

{

    const url = details.url;

    if (is_privileged_url(url))

	return;

    const [pattern, settings] = query_best(storage, url);

    const allow = !!(settings && settings.allow);

    const nonce = gen_nonce();

    let orig_csp_headers;

    let old_signature;

    let hachette_header;

    let headers = details.responseHeaders;

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

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

	if (!match)

	    continue;

	const old_data = extract_signed(...match.splice(1, 2), [[0]]);

	if (!old_data || old_data.url !== url)

	    continue;

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

	orig_csp_headers = old_data.csp_headers;

	old_signature = old_data.policy_signature;

	hachette_header = header;

	break;

    }

    if (!hachette_header) {

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

	headers.push(hachette_header);

    }

    orig_csp_headers = orig_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, !allow));

    if (old_signature)

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

    const policy_object = {allow, nonce, url};

    const sanitizer = h => sanitize_csp_header(h, policy_object);

    headers.push(...orig_csp_headers.map(sanitizer));

    const policy = encodeURIComponent(JSON.stringify(policy_object));

    const policy_signature = sign_data(policy, new Date());

    const later_30sec = new Date(new Date().getTime() + 30000).toGMTString();

    headers.push({

	name: "Set-Cookie",

	value: `hachette-${policy_signature}=${policy}; Expires=${later_30sec};`

    });

    /*

     * 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: orig_csp_headers, policy_signature, url};

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

    hachette_header.value = sign_data(hachette_data, 0) + hachette_data;

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

    if (!allow)

	headers.push({name: "content-security-policy", value: csp_rule(nonce)});

    return {responseHeaders: headers};

}

async function start_policy_injector()

{

    storage = await get_storage();

    let extra_opts = ["blocking", "responseHeaders"];

    if (is_chrome)

	extra_opts.push("extraHeaders");

    browser.webRequest.onHeadersReceived.addListener(

	headers_inject,

	{

	    urls: ["<all_urls>"],

	    types: ["main_frame", "sub_frame"]

	},

	extra_opts

    );

}

/*

 * EXPORTS_START

 * EXPORT start_policy_injector

 * EXPORTS_END

 */