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gorhillgorhill
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Add trusted-prevent-fetch scriptlet
Related feedback: uBlockOrigin/uBlock-discussions#915 (comment)
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‎src/js/resources/prevent-fetch.js

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/*******************************************************************************
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uBlock Origin - a comprehensive, efficient content blocker
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Copyright (C) 2019-present Raymond Hill
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see {http://www.gnu.org/licenses/}.
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Home: https://github.com/gorhill/uBlock
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*/
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import { generateContentFn } from './utils.js';
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import { proxyApplyFn } from './proxy-apply.js';
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import { registerScriptlet } from './base.js';
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import { safeSelf } from './safe-self.js';
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/******************************************************************************/
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function preventFetchFn(
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trusted = false,
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propsToMatch = '',
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responseBody = '',
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responseType = ''
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) {
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const safe = safeSelf();
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const scriptletName = `${trusted ? 'trusted-' : ''}prevent-fetch`;
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const logPrefix = safe.makeLogPrefix(
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scriptletName,
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propsToMatch,
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responseBody,
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responseType
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);
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const needles = [];
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for ( const condition of safe.String_split.call(propsToMatch, /\s+/) ) {
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if ( condition === '' ) { continue; }
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const pos = condition.indexOf(':');
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let key, value;
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if ( pos !== -1 ) {
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key = condition.slice(0, pos);
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value = condition.slice(pos + 1);
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} else {
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key = 'url';
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value = condition;
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}
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needles.push({ key, pattern: safe.initPattern(value, { canNegate: true }) });
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}
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const validResponseProps = {
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ok: [ false, true ],
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statusText: [ '', 'Not Found' ],
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type: [ 'basic', 'cors', 'default', 'error', 'opaque' ],
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};
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const responseProps = {
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statusText: { value: 'OK' },
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};
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if ( /^\{.*\}$/.test(responseType) ) {
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try {
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Object.entries(JSON.parse(responseType)).forEach(([ p, v ]) => {
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if ( validResponseProps[p] === undefined ) { return; }
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if ( validResponseProps[p].includes(v) === false ) { return; }
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responseProps[p] = { value: v };
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});
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}
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catch { }
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} else if ( responseType !== '' ) {
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if ( validResponseProps.type.includes(responseType) ) {
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responseProps.type = { value: responseType };
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}
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}
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proxyApplyFn('fetch', function fetch(context) {
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const { callArgs } = context;
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const details = callArgs[0] instanceof self.Request
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? callArgs[0]
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: Object.assign({ url: callArgs[0] }, callArgs[1]);
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let proceed = true;
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try {
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const props = new Map();
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for ( const prop in details ) {
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let v = details[prop];
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if ( typeof v !== 'string' ) {
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try { v = safe.JSON_stringify(v); }
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catch { }
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}
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if ( typeof v !== 'string' ) { continue; }
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props.set(prop, v);
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}
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if ( safe.logLevel > 1 || propsToMatch === '' && responseBody === '' ) {
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const out = Array.from(props).map(a => `${a[0]}:${a[1]}`);
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safe.uboLog(logPrefix, `Called: ${out.join('\n')}`);
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}
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if ( propsToMatch === '' && responseBody === '' ) {
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return context.reflect();
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}
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proceed = needles.length === 0;
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for ( const { key, pattern } of needles ) {
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if (
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pattern.expect && props.has(key) === false ||
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safe.testPattern(pattern, props.get(key)) === false
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) {
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proceed = true;
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break;
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}
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}
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} catch {
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}
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if ( proceed ) {
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return context.reflect();
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}
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return Promise.resolve(generateContentFn(trusted, responseBody)).then(text => {
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safe.uboLog(logPrefix, `Prevented with response "${text}"`);
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const response = new Response(text, {
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headers: {
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'Content-Length': text.length,
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}
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});
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const props = Object.assign(
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{ url: { value: details.url } },
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responseProps
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);
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safe.Object_defineProperties(response, props);
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return response;
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});
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});
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}
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registerScriptlet(preventFetchFn, {
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name: 'prevent-fetch.fn',
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dependencies: [
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generateContentFn,
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proxyApplyFn,
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safeSelf,
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],
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});
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/******************************************************************************/
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/**
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* @scriptlet prevent-fetch
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*
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* @description
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* Prevent a fetch() call from making a network request to a remote server.
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*
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* @param propsToMatch
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* The fetch arguments to match for the prevention to be triggered. The
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* untrusted flavor limits the realm of response to return to safe values.
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*
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* @param [responseBody]
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* Optional. The reponse to return when the prevention occurs.
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*
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* @param [responseType]
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* Optional. The response type to use when emitting a dummy response as a
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* result of the prevention.
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*
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* */
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function preventFetch(...args) {
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preventFetchFn(false, ...args);
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}
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registerScriptlet(preventFetch, {
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name: 'prevent-fetch.js',
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aliases: [
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'no-fetch-if.js',
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],
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dependencies: [
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preventFetchFn,
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],
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});
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/******************************************************************************/
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/**
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* @scriptlet trusted-prevent-fetch
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*
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* @description
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* Prevent a fetch() call from making a network request to a remote server.
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*
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* @param propsToMatch
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* The fetch arguments to match for the prevention to be triggered.
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*
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* @param [responseBody]
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* Optional. The reponse to return when the prevention occurs. The trusted
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* flavor allows to return any response.
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*
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* @param [responseType]
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* Optional. The response type to use when emitting a dummy response as a
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* result of the prevention.
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*
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* */
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function trustedPreventFetch(...args) {
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preventFetchFn(true, ...args);
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}
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registerScriptlet(trustedPreventFetch, {
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name: 'trusted-prevent-fetch.js',
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requiresTrust: true,
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dependencies: [
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preventFetchFn,
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],
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});
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/******************************************************************************/

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