Haketilo

/**

 * This file is part of Haketilo.

 *

 * Function: Modify HTTP traffic usng webRequest API.

 *

 * Copyright (C) 2021 Wojtek Kosior <koszko@koszko.org>

 *

 * This program is free software: you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * As additional permission under GNU GPL version 3 section 7, you

 * may distribute forms of that code without the copy of the GNU

 * GPL normally required by section 4, provided you include this

 * license notice and, in case of non-source distribution, a URL

 * through which recipients can access the Corresponding Source.

 * If you modify file(s) with this exception, you may extend this

 * exception to your version of the file(s), but you are not

 * obligated to do so. If you do not wish to do so, delete this

 * exception statement from your version.

 *

 * As a special exception to the GPL, any HTML file which merely

 * makes function calls to this code, and for that purpose

 * includes it by reference shall be deemed a separate work for

 * copyright law purposes. If you modify this code, you may extend

 * this exception to your version of the code, but you are not

 * obligated to do so. If you do not wish to do so, delete this

 * exception statement from your version.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program.  If not, see <https://www.gnu.org/licenses/>.

 *

 * I, Wojtek Kosior, thereby promise not to sue for violation of this file's

 * license. Although I request that you do not make use of this code in a

 * proprietary program, I am not going to enforce this in court.

 */

#IMPORT common/indexeddb.js        AS haketilodb

#IF MOZILLA

#IMPORT background/stream_filter.js

#ENDIF

#FROM common/browser.js IMPORT browser

#FROM common/misc.js    IMPORT is_privileged_url, csp_header_regex

#FROM common/policy.js  IMPORT decide_policy

#FROM background/patterns_query_manager.js IMPORT tree, default_allow

let secret;

function on_headers_received(details)

{

    const url = details.url;

    if (is_privileged_url(details.url))

	return;

    let headers = details.responseHeaders;

    const policy =

	  decide_policy(tree, details.url, !!default_allow.value, secret);

    if (policy.allow)

	return;

    if (policy.payload)

	headers = headers.filter(h => !csp_header_regex.test(h.name));

    headers.push({name: "Content-Security-Policy", value: policy.csp});

#IF MOZILLA

    let skip = false;

    for (const header of headers) {

	if (header.name.toLowerCase().trim() !== "content-disposition")

	    continue;

	if (/^\s*attachment\s*(;.*)$/i.test(header.value)) {

		skip = true;

	} else {

	    skip = false;

	    break;

	}

    }

    skip = skip || (details.statusCode >= 300 && details.statusCode < 400);

    if (!skip)

	headers = stream_filter.apply(details, headers, policy);

#ENDIF

    return {responseHeaders: headers};

}

#IF CHROMIUM && MV2

const request_url_regex = /^[^?]*\?url=(.*)$/;

const redirect_url_template = browser.runtime.getURL("dummy") + "?settings=";

function on_before_request(details)

{

    /*

     * Content script will make a synchronous XmlHttpRequest to extension's

     * `dummy` file to query settings for given URL. We smuggle that

     * information in query parameter of the URL we redirect to.

     * A risk of fingerprinting arises if a page with script execution allowed

     * guesses the dummy file URL and makes an AJAX call to it. It is currently

     * a problem in ManifestV2 Chromium-family port of Haketilo because Chromium

     * uses predictable URLs for web-accessible resources. We plan to fix it in

     * the future ManifestV3 port.

     */

    if (details.type !== "xmlhttprequest")

	return {cancel: true};

    if (details.url.startsWith(redirect_url_template))

	return;

#IF DEBUG

    console.debug(`Haketilo: Settings queried using XHR for '${details.url}'.`);

#ENDIF

    /*

     * request_url should be of the following format:

     *     <url_for_extension's_dummy_file>?url=<valid_urlencoded_url>

     */

    const match = request_url_regex.exec(details.url);

    if (match) {

	const queried_url = decodeURIComponent(match[1]);

	if (details.initiator && details.initiator !== "null" &&

	    !queried_url.startsWith(details.initiator)) {

	    console.warn(`Haketilo: Blocked suspicious query of '${queried_url}' by '${details.initiator}'. This might be the result of page fingerprinting the browser.`);

	    return {cancel: true};

	}

	const policy =

	      decide_policy(tree, queried_url, !!default_allow.value, secret);

	if (!policy.error) {

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

	    return {redirectUrl: redirect_url_template + encoded_policy};

	}

    }

    console.warn(`Haketilo: Bad request! Expected ${browser.runtime.getURL("dummy")}?url=<valid_urlencoded_url>. Got ${details.url}. This might be the result of page fingerprinting the browser.`);

    return {cancel: true};

}

const all_types = [

    "main_frame", "sub_frame", "stylesheet", "script", "image", "font",

    "object", "xmlhttprequest", "ping", "csp_report", "media", "websocket",

    "other", "main_frame", "sub_frame"

];

#ENDIF

async function start(secret_)

{

    secret = secret_;

#IF CHROMIUM

    const extra_opts = ["blocking", "extraHeaders"];

#ELSE

    const extra_opts = ["blocking"];

#ENDIF

    browser.webRequest.onHeadersReceived.addListener(

	on_headers_received,

	{urls: ["<all_urls>"], types: ["main_frame", "sub_frame"]},

	extra_opts.concat("responseHeaders")

    );

#IF CHROMIUM && MV2

    browser.webRequest.onBeforeRequest.addListener(

	on_before_request,

	{urls: [browser.runtime.getURL("dummy") + "*"], types: all_types},

	extra_opts

    );

#ENDIF

}

#EXPORT start