background.js

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * @author didierfred@gmail.com
 * @version 0.4
 */

'use strict';

let config;
let started = 'off';
let debug_mode = false;
const isChrome = navigator.userAgent.toLowerCase().indexOf('chrome') !== -1;

loadFromBrowserStorage(['config', 'started'], function (result) {
    // if old storage method
    if (result.config === undefined) loadConfigurationFromLocalStorage();
    else {
        started = result.started;
        config = JSON.parse(result.config);
    }

    if (started === 'on') {
        addListener();
        chrome.browserAction.setIcon({path: 'icons/modify-green-32.png'});
    } else if (started !== 'off') {
        started = 'off';
        storeInBrowserStorage({started: 'off'});
    }
    // listen for change in configuration or start/stop
    chrome.runtime.onMessage.addListener(notify);
});

function loadConfigurationFromLocalStorage() {
    // if configuration exist
    if (localStorage.getItem('config')) {
        console.log('Load standard config');
        config = JSON.parse(localStorage.getItem('config'));

        // If config 1.0 (Simple Modify headers V1.2) , save to format 1.1
        if (config.format_version === '1.0') {
            config.format_version = '1.2';
            for (let line of config.headers) {
                line.apply_on = 'req';
                line.url_contains = '';
            }
            config.debug_mode = false;
            config.use_url_contains = false;
            console.log('save new config' + JSON.stringify(config));
        }
        // If config 1.1 (Simple Modify headers V1.3 to version 1.5) , save to format 1.2
        if (config.format_version === '1.1') {
            config.format_version = '1.2';
            for (let line of config.headers) line.url_contains = '';
            config.use_url_contains = false;
            console.log('save new config' + JSON.stringify(config));
        }
    } else {
        // else check if old config exist (Simple Modify headers V1.1)
        if (localStorage.getItem('targetPage') && localStorage.getItem('modifyTable')) {
            console.log('Load old config');
            let headers = [];
            let modifyTable = JSON.parse(localStorage.getItem('modifyTable'));
            for (const to_modify of modifyTable) {
                headers.push({
                    action: to_modify[0],
                    url_contains: '',
                    header_name: to_modify[1],
                    header_value: to_modify[2],
                    comment: '',
                    apply_on: 'req',
                    status: to_modify[3]
                });
            }
            config = {
                format_version: '1.1',
                target_page: localStorage.getItem('targetPage'),
                headers: headers,
                debug_mode: false,
                use_url_contains: false
            };
        }
        //else no config exists, create a default one
        else {
            console.log('Load default config');
            let headers = [];
            headers.push({
                url_contains: '',
                action: 'add',
                header_name: 'test-header-name',
                header_value: 'test-header-value',
                comment: 'test',
                apply_on: 'req',
                status: 'on'
            });
            config = {
                format_version: '1.1',
                target_page: 'https://httpbin.org/*',
                headers: headers,
                debug_mode: false,
                use_url_contains: false
            };
        }
    }
    storeInBrowserStorage({config: JSON.stringify(config)});
    started = localStorage.getItem('started');
    if (started !== undefined) storeInBrowserStorage({started: started});
}

function loadFromBrowserStorage(item, callback_function) {
    chrome.storage.local.get(item, callback_function);
}

function storeInBrowserStorage(item, callback_function) {
    chrome.storage.local.set(item, callback_function);
}

/*
 * This function set a key-value pair in HTTP header "Cookie",
 *   and returns the value of HTTP header after modification.
 * If key already exists, it modify the value.
 * If key doesn't exist, it add the key-value pair.
 * If value is undefined, it delete the key-value pair from cookies.
 *
 * Assuming that, the same key SHOULD NOT appear twice in cookies.
 * Also assuming that, all cookies doesn't contains semicolon.
 *   (99.9% websites are following these rules)
 *
 * Example:
 *   cookie_keyvalues_set("msg=good; user=recolic; password=test", "user", "p")
 *     => "msg=good; user=p; password=test"
 *   cookie_keyvalues_set("msg=good; user=recolic; password=test", "time", "night")
 *     => "msg=good; user=recolic; password=test;time=night"
 *
 * Recolic K <root@recolic.net>
 */
function cookie_keyvalues_set(original_cookies, key, value) {
    let new_element = ' ' + key + '=' + value; // not used if value is undefined.
    let cookies_ar = original_cookies.split(';').filter((e) => e.trim().length > 0);
    let selected_cookie_index = cookies_ar.findIndex((kv) => kv.trim().startsWith(key + '='));
    if (selected_cookie_index == -1 && value != undefined) cookies_ar.push(new_element);
    else {
        if (value === undefined) cookies_ar.splice(selected_cookie_index, 1);
        else cookies_ar.splice(selected_cookie_index, 1, new_element);
    }
    return cookies_ar.join(';');
}
/*
 * This function modify the HTTP response header "Set-Cookie",
 *   and replace the value of its cookie, to some new_value.
 * If key doesn't match original_set_cookie_header_content, new key is used in result.
 *
 * Example:
 *   set_cookie_modify_cookie_value("token=123; path=/; expires=Sat, 30 Oct 2021 17:57:32 GMT; secure; HttpOnly", "token", "bar")
 *     => "token=bar; path=/; expires=Sat, 30 Oct 2021 17:57:32 GMT; secure; HttpOnly"
 *   set_cookie_modify_cookie_value("  user=recolic", "user", "hacker")
 *     => "user=hacker"
 *   set_cookie_modify_cookie_value("user=recolic; path=/; HttpOnly", "token", "bar")
 *     => "token=bar; path=/; HttpOnly"
 *
 * Recolic K <root@recolic.net>
 */
function set_cookie_modify_cookie_value(original_set_cookie_header_content, key, new_value) {
    let trimmed = original_set_cookie_header_content.trimStart();
    let original_attributes = trimmed.indexOf(';') === -1 ? '' : trimmed.substring(trimmed.indexOf(';'));
    return key + '=' + new_value + original_attributes;
}

/*
 * Standard function to log messages
 *
 */

function log(message) {
    console.log(new Date() + ' SimpleModifyHeader : ' + message);
}

/*
 * Rewrite the request header (add , modify or delete)
 *
 */
function rewriteRequestHeader(e) {
    if (config.debug_mode) log('Start modify request headers for url ' + e.url);
    for (let to_modify of config.headers) {
        if (
            to_modify.status === 'on' &&
            to_modify.apply_on === 'req' &&
            (!config.use_url_contains ||
                (config.use_url_contains && doesUrlContainsAnUrlContains(e.url, to_modify.url_contains)))
        ) {
            if (to_modify.action === 'add') {
                let new_header = {name: to_modify.header_name, value: to_modify.header_value};
                e.requestHeaders.push(new_header);
                if (config.debug_mode)
                    log(
                        'Add request header : name=' +
                            to_modify.header_name +
                            ',value=' +
                            to_modify.header_value +
                            ' for url ' +
                            e.url
                    );
            } else if (to_modify.action === 'modify') {
                for (let header of e.requestHeaders) {
                    if (header.name.toLowerCase() === to_modify.header_name.toLowerCase()) {
                        if (config.debug_mode)
                            log(
                                'Modify request header :  name= ' +
                                    to_modify.header_name +
                                    ',old value=' +
                                    header.value +
                                    ',new value=' +
                                    to_modify.header_value +
                                    ' for url ' +
                                    e.url
                            );
                        header.value = to_modify.header_value;
                    }
                }
            } else if (to_modify.action === 'delete') {
                let index = -1;
                for (let i = 0; i < e.requestHeaders.length; i++) {
                    if (e.requestHeaders[i].name.toLowerCase() === to_modify.header_name.toLowerCase()) index = i;
                }
                if (index !== -1) {
                    e.requestHeaders.splice(index, 1);
                    if (config.debug_mode)
                        log(
                            'Delete request header :  name=' + to_modify.header_name.toLowerCase() + ' for url ' + e.url
                        );
                }
            } else if (to_modify.action === 'cookie_add_or_modify') {
                let header_cookie = e.requestHeaders.find((header) => header.name.toLowerCase() === 'cookie');
                let new_cookie = cookie_keyvalues_set(
                    header_cookie === undefined ? '' : header_cookie.value,
                    to_modify.header_name,
                    to_modify.header_value
                );
                if (header_cookie === undefined) {
                    e.requestHeaders.push({name: 'Cookie', value: new_cookie});
                    if (config.debug_mode)
                        log(
                            'cookie_add_or_modify.req new_header : name=Cookie,value=' +
                                new_cookie +
                                ' for url ' +
                                e.url
                        );
                } else {
                    header_cookie.value = new_cookie;
                    if (config.debug_mode)
                        log(
                            'cookie_add_or_modify.req modify_header : name=Cookie,value=' +
                                new_cookie +
                                ' for url ' +
                                e.url
                        );
                }
            } else if (to_modify.action === 'cookie_delete') {
                let header_cookie = e.requestHeaders.find((header) => header.name.toLowerCase() === 'cookie');
                let new_cookie = cookie_keyvalues_set(
                    header_cookie === undefined ? '' : header_cookie.value,
                    to_modify.header_name,
                    undefined
                );
                if (header_cookie === undefined) {
                    if (config.debug_mode)
                        log('cookie_delete.req: no cookie header found. doing nothing for url ' + e.url);
                } else {
                    header_cookie.value = new_cookie;
                    if (config.debug_mode)
                        log('cookie_delete.req modify_header : name=Cookie,value=' + new_cookie + ' for url ' + e.url);
                }
            }
        }
    }
    if (config.debug_mode) log('End modify request headers for url ' + e.url);
    return {requestHeaders: e.requestHeaders};
}

function doesUrlContainsAnUrlContains(url, url_contains) {
    if (url_contains === undefined || url_contains === '') return true;
    url_contains = url_contains.trim();
    if (url_contains.includes(';')) {
        let url_contains_array = url_contains.split(';');
        for (let i = 0; i < url_contains_array.length; i++) {
            if (url_contains_array[i].length > 0 && url.includes(url_contains_array[i])) return true;
        }
        return false;
    }
    return url.includes(url_contains);
};
/*
 * Rewrite the response header (add , modify or delete)
 *
 */
function rewriteResponseHeader(e) {
    if (config.debug_mode) log('Start modify response headers for url ' + e.url);
    for (let to_modify of config.headers) {
        if (
            to_modify.status === 'on' &&
            to_modify.apply_on === 'res' &&
            (!config.use_url_contains || (config.use_url_contains && doesUrlContainsAnUrlContains(e.url, to_modify.url_contains)))
        ) {
            if (to_modify.action === 'add') {
                let new_header = {name: to_modify.header_name, value: to_modify.header_value};
                e.responseHeaders.push(new_header);
                if (config.debug_mode)
                    log(
                        'Add response header : name=' +
                            to_modify.header_name +
                            ',value=' +
                            to_modify.header_value +
                            ' for url ' +
                            e.url
                    );
            } else if (to_modify.action === 'modify') {
                for (let header of e.responseHeaders) {
                    if (header.name.toLowerCase() === to_modify.header_name.toLowerCase()) {
                        if (config.debug_mode)
                            log(
                                'Modify response header :  name= ' +
                                    to_modify.header_name +
                                    ',old value=' +
                                    header.value +
                                    ',new value=' +
                                    to_modify.header_value +
                                    ' for url ' +
                                    e.url
                            );
                        header.value = to_modify.header_value;
                    }
                }
            } else if (to_modify.action === 'delete') {
                let index = -1;
                for (let i = 0; i < e.responseHeaders.length; i++) {
                    if (e.responseHeaders[i].name.toLowerCase() === to_modify.header_name.toLowerCase()) index = i;
                }
                if (index !== -1) {
                    e.responseHeaders.splice(index, 1);
                    if (config.debug_mode)
                        log(
                            'Delete response header :  name=' +
                                to_modify.header_name.toLowerCase() +
                                ' for url ' +
                                e.url
                        );
                }
            } else if (to_modify.action === 'cookie_add_or_modify') {
                let header_cookie = e.responseHeaders.find(
                    (header) =>
                        header.name.toLowerCase() === 'set-cookie' &&
                        header.value
                            .toLowerCase()
                            .trim()
                            .startsWith(to_modify.header_name.toLowerCase() + '=')
                );
                let new_header_value = set_cookie_modify_cookie_value(
                    header_cookie === undefined ? '' : header_cookie.value,
                    to_modify.header_name,
                    to_modify.header_value
                );
                if (header_cookie === undefined) {
                    log(
                        "SimpleModifyHeaders.Warning: you're using cookie_add_or_modify in Response. While adding new cookie in response, this plugin only generates `Set-Cookie: cookie-name=cookie-value `, without ANY additional attributes. Add a `Set-Cookie` header if you need them. "
                    );
                    e.responseHeaders.push({name: 'Set-Cookie', value: new_header_value});
                    if (config.debug_mode)
                        log(
                            'cookie_add_or_modify.resp new_header : name=Cookie,value=' +
                                new_header_value +
                                ' for url ' +
                                e.url
                        );
                } else {
                    header_cookie.value = new_header_value;
                    if (config.debug_mode)
                        log(
                            'cookie_add_or_modify.resp modify_header : name=Cookie,value=' +
                                new_header_value +
                                ' for url ' +
                                e.url
                        );
                }
            } else if (to_modify.action === 'cookie_delete') {
                let index = e.responseHeaders.findIndex(
                    (header) =>
                        header.name.toLowerCase() === 'set-cookie' &&
                        header.value
                            .toLowerCase()
                            .trim()
                            .startsWith(to_modify.header_name.toLowerCase() + '=')
                );
                if (index === -1) {
                    if (config.debug_mode)
                        log('cookie_delete.resp: no matching set-cookie header. doing nothing for url ' + e.url);
                } else {
                    e.responseHeaders.splice(index, 1);
                    if (config.debug_mode)
                        log('cookie_delete.resp delete_header : name=' + to_modify.header_name + ' for url ' + e.url);
                }
            }
        }
    }
    if (config.debug_mode) log('End modify response headers for url ' + e.url);
    return {responseHeaders: e.responseHeaders};
}

/*
 * Listen for message form config.js
 * if message is reload : reload the configuration
 * if message is on : start the modify header
 * if message is off : stop the modify header
 *
 **/
function notify(message) {
    if (message === 'reload') {
        if (config.debug_mode) log('Reload configuration');
        loadFromBrowserStorage(['config'], function (result) {
            config = JSON.parse(result.config);
            if (started === 'on') {
                removeListener();
                addListener();
            }
        });
    } else if (message === 'off') {
        removeListener();
        chrome.browserAction.setIcon({path: 'icons/modify-32.png'});
        started = 'off';
        if (config.debug_mode) log('Stop modifying headers');
    } else if (message === 'on') {
        addListener();
        chrome.browserAction.setIcon({path: 'icons/modify-green-32.png'});
        started = 'on';
        if (config.debug_mode) log('Start modifying headers');
    }
}

/*
 * Add rewriteRequestHeader as a listener to onBeforeSendHeaders, only for the target pages.
 * Add rewriteResponseHeader as a listener to onHeadersReceived, only for the target pages.
 * Make it "blocking" so we can modify the headers.
 */
function addListener() {
    let target = config.target_page.replaceAll(' ', '');
    if (target === '*' || target === '') target = '<all_urls>';
    chrome.webRequest.onBeforeSendHeaders.addListener(rewriteRequestHeader, {urls: target.split(';')}, [
        'blocking',
        'requestHeaders'
    ]);
    chrome.webRequest.onHeadersReceived.addListener(rewriteResponseHeader, {urls: target.split(';')}, [
        'blocking',
        'responseHeaders'
    ]);
}

/*
 * Remove the two listener
 *
 */
function removeListener() {
    chrome.webRequest.onBeforeSendHeaders.removeListener(rewriteRequestHeader);
    chrome.webRequest.onHeadersReceived.removeListener(rewriteResponseHeader);
}