在内容脚本之前注入javascript变量

Question

在内容脚本之前注入javascript变量

Sna*_*r26 3 javascript google-chrome-extension

使用我的后台脚本background.js,我需要在注入另一个文件inject.js作为内容脚本之前注入一个动态变量作为内容脚本.Inject.js需要访问此变量并在页面上的任何脚本运行之前运行它的代码.我无法从inject.js内容脚本访问动态变量.

的manifest.json

{
"name": "Shape Shifter",
"version": "1.0",
"description": "Anti browser fingerprinting web extension. Generates randomised values for HTTP request headers, javascript property values and javascript method return types.",
"manifest_version": 2,
"icons": {
    "32": "icons/person-32.png",
    "48": "icons/person-48.png"
},
"background": {
    "persistent": true,
    "scripts": ["js/ua.js", "js/words.js", "js/lib/seedrandom.min.js", "js/random.js", "js/background.js"]
},
"browser_action": {
    "default_title": "Shape Shifter",
    "default_icon": "icons/person-32.png",
    "default_popup": "html/popup.html"
},
"content_scripts": [
  {
    "run_at": "document_end",
    "matches": ["<all_urls>"],
    "js": ["js/inject.js"] 
  }
],
"permissions": [
    "webRequest",
    "webRequestBlocking",
    "webNavigation",
    "tabs",
    "activeTab",
    "storage",
    "<all_urls>"
],
"web_accessible_resources": [
    "js/ua.js",
    "js/words.js",
    "js/lib/seedrandom.min.js",
    "js/random.js",
    "js/api/document.js",
    "js/api/navigator.js",
    "js/api/canvas.js",
    "js/api/history.js",
    "js/api/battery.js",
    "js/api/audio.js",
    "js/api/element.js"
]

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}

background.js

"use strict";

console.log("Background Script Running ...");

function getSeed(origin) {
    // Get a Storage object
    var storage = window.localStorage;

    // Do we already have a seed in storage for this origin or not?
    var seed = storage.getItem(origin);

    if (seed === null) {
        // Initialise a 32 byte buffer
        seed = new Uint8Array(32);

        // Fill it with cryptographically random values
        window.crypto.getRandomValues(seed);

        // Save it to storage
        storage.setItem(origin, seed);
    }

    return seed;
}

// Methods to get HTTP headers
function getAcceptHeader(seed) {
    return "NotYetImplemented";
}
function getAcceptCharsetHeader(seed) {
    return "NotYetImplemented";
}
function getAcceptEncodingHeader(seed) {
    return "NotYetImplemented";
}
function getAcceptLanguageHeader() {
    // NOTE: TOR Browser uses American English
    return "en-US,en;q=0.5";
}
function getAuthorizationHeader(seed) {
    return "NotYetImplemented";
}
function getExpectHeader(seed) {
    return "NotYetImplemented";
}
function getFromHeader(seed) {
    return "NotYetImplemented";
}
function getHostHeader(seed) {
    return "NotYetImplemented";
}
function getIfMatchHeader(seed) {
    return "NotYetImplemented";
}
function getIfModifiedSinceHeader(seed) {
    return "NotYetImplemented";
}
function getIfNoneMatchHeader(seed) {
    return "NotYetImplemented";
}
function getIfRangeHeader(seed) {
    return "NotYetImplemented";
}
function getIfUnmodifiedSinceHeader(seed) {
    return "NotYetImplemented";
}
function getMaxForwardsHeader(seed) {
    return "NotYetImplemented";
}
function getProxyAuthorizationHeader(seed) {
    return "NotYetImplemented";
}
function getRangeHeader(seed) {
    return "NotYetImplemented";
}
function getRefererHeader() {
    // NOTE: From https://developer.mozilla.org/en-US/docs/Web/API/Document/referrer
    // NOTE: The value is an empty string if the user navigated to the page directly (not through a link, but, for example, via a bookmark).
    // NOTE: Since this property returns only a string, it does not give you DOM access to the referring page.

    // NOTE: Make websites think we always go to them directly rather than being referred.
    return "";
}
function getTEHeader(seed) {
    return "NotYetImplemented";
}
function getUserAgentHeader(seed) {
    Math.seedrandom(seed);

    return userAgents[randomNumber(0, userAgents.length)];
}

function rewriteHttpHeaders(e) {
    // Create URL object from url string
    var serverUrl = new URL(e.url);

    console.log(e);

    // Get the origin (hostname)
    var origin = serverUrl.hostname;

    var seed = getSeed(origin);

    console.log("Background - Seed for origin " + origin + ": " + seed);

    for (var header of e.requestHeaders) {
        if (header.name.toLowerCase() === "accept") {
        }
        else if (header.name.toLowerCase() === "accept-charset") {
        }
        else if (header.name.toLowerCase() === "accept-encoding") {
        }
        else if (header.name.toLowerCase() === "accept-language") {
            header.value = getAcceptLanguageHeader();
        }
        else if (header.name.toLowerCase() === "authorization") {
        }
        else if (header.name.toLowerCase() === "expect") {
        }
        else if (header.name.toLowerCase() === "from") {
        }
        else if (header.name.toLowerCase() === "host") {
        }
        else if (header.name.toLowerCase() === "if-match") {
        }
        else if (header.name.toLowerCase() === "if-modified-since") {
        }
        else if (header.name.toLowerCase() === "if-none-match") {
        }
        else if (header.name.toLowerCase() === "if-range") {
        }
        else if (header.name.toLowerCase() === "if-unmodified-since") {
        }
        else if (header.name.toLowerCase() === "max-forwards") {
        }
        else if (header.name.toLowerCase() === "proxy-authorization") {
        }
        else if (header.name.toLowerCase() === "range") {
        }
        else if (header.name.toLowerCase() === "referer") {
            header.value = getRefererHeader();
        }
        else if (header.name.toLowerCase() === "te") {
        }
        else if (header.name.toLowerCase() === "user-agent") {
            header.value = getUserAgentHeader(seed);
        }
    }

    return {requestHeaders: e.requestHeaders};
}

chrome.webRequest.onBeforeSendHeaders.addListener(rewriteHttpHeaders, {urls: ["<all_urls>"]}, ["blocking", "requestHeaders"]);

chrome.webNavigation.onBeforeNavigate.addListener(function(details) {
    // Create URL object from url string
    var serverUrl = new URL(details.url);

    // Get the origin (hostname)
    var origin = serverUrl.hostname;

    var seed = "Some dynamic value";

    console.log("Injecting Value");
    chrome.tabs.executeScript(details.tabId, {code: "var seed = '" + seed + "';console.log(seed);", runAt: "document_start"}, function() {
        console.log("Value Injected");
    });
});

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inject.js

(function() {
  function inject(filePath) {
    var script = document.createElement('script');
    script.src = chrome.extension.getURL(filePath);
    script.onload = function() {
      this.remove();
    };
    (document.head || document.documentElement).appendChild(script);
  }

  function injectText(text) {
    var script = document.createElement('script');
    script.textContent = text;
    script.onload = function() {
      this.remove();
    };
    (document.head || document.documentElement).appendChild(script);
  }

  console.log("CONTENT SCRIPT RUNNING");

  console.log(seed); // SEED IS NOT DEFINED HERE ???

  injectText("var seed = 'hello';");
  console.log("[INFO] Injected Seed ...");
  inject("js/ua.js");
  console.log("[INFO] Injected UA ...");
  inject("js/words.js");
  console.log("[INFO] Injected Words ...");
  inject("js/lib/seedrandom.min.js");
  console.log("[INFO] Injected Seed Random ...");
  inject("js/random.js");
  console.log("[INFO] Injected Random ...");
  inject("js/api/document.js");
  console.log("[INFO] Injected Document API ...");
  inject("js/api/navigator.js");
  console.log("[INFO] Injected Navigator API ...");
  inject("js/api/canvas.js");
  console.log("[INFO] Injected Canvas API ...");
  inject("js/api/history.js");
  console.log("[INFO] Injected History API ...");
  inject("js/api/battery.js");
  console.log("[INFO] Injected Battery API ...");
  inject("js/api/audio.js");
  console.log("[INFO] Injected Audio API ...");
  inject("js/api/element.js");
  console.log("[INFO] Injected Element API ...");
})();

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尝试将种子记录到控制台时出现错误:

inject.js:26 Uncaught ReferenceError: seed is not defined
    at inject.js:26
    at inject.js:52

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有任何想法吗？

Answer 1

Xan*_*Xan 5

这将非常棘手.

让我们来看看你的要求.

Inject.js需要访问此变量并在页面上的任何脚本运行之前运行它的代码.

这不是您的代码目前的工作方式.你inject.js的执行是document_end- 在整个DOM树被解析之后发生,这意味着在所有页面脚本运行之后(禁止异步部分和async脚本加载).

Chrome有一个解决方案 - 您可以将执行设置为document_start.然后你的代码将真正运行在其他所有内容之前,而DOM仍未被解析(因此document基本上是空的).使用您的代码所做的事情,它不应该产生问题(它只依赖于document.documentElement,它将存在).

问题是,所有代码都必须同步才能享受"先行之前运行"属性.只要代码的同步部分运行,Chrome就会暂停DOM解析,但随后所有的赌注都会关闭,因为它会继续解析(并运行代码)文档.

例如,这会取消资格chrome.storage和消息传递,因为对它的访问必然是异步的.

我需要注入一个动态变量[在页面加载]

这意味着您无法预先将其存储在某些同步可用的存储中(例如,在localStorage网站的cookie或网站中),如果您事先不知道域,这将是有问题的.

请注意,特别是对于您的代码,这可能不是那么多因素; 您的"动态"值实际上是每个域固定的.您仍然不知道将访问哪个域,但您至少可以保证在第二次加载时它将在那里.

使用我的后台脚本background.js,我需要在注入另一个文件之前注入一个动态变量作为内容脚本[仍然需要在页面上的其他所有内容之前运行]

这是棘手的部分.事实上,如上所述,这根本不可能.您正试图从后台捕获提交导航之间的确切时刻,以便Chrome将页面切换到新域以及执行document_start脚本.

那里没有可检测到的差距,也没办法告诉Chrome等待.这是一个你无望解决的竞争条件.

您尝试使用webNavigation.onBeforeNavigate- 甚至在提交导航之前.所以你injectScript甚至可能会转到上一页,使它无用.如果你尝试其他一些事件,例如.onCommitted,到目前为止还没有确切injectScript知道何时会得到对待.可能在你的脚本之后.

那么,如何解决这一切呢？

幸运的是,内存脚本可以使用一些同步存储,您可以在最早的脚本执行之前将某些信息推送到其中.

饼干.

但是,使用chrome.cookiesAPI无济于事.您需要主动将cookie值注入请求中webRequest.onHeadersReceived.

您必须同步准备值以使用阻止处理程序来处理它onHeadersReceived,但是您可以简单地添加一个Set-Cookie标头并立即将其提供document.cookies给您inject.js.

// background.js
function addSeedCookie(details) {
  seed = SomethingSynchronous();
  details.responseHeaders.push({
    name: "Set-Cookie",
    value: `seed_goes_here=${seed};`
  });
  return {
    responseHeaders: details.responseHeaders
  };
}

chrome.webRequest.onHeadersReceived.addListener(
  addSeedCookie, {urls: ["<all_urls>"]}, ["blocking", "responseHeaders"]
);

// inject.js
function getCookie(cookie) { // https://stackoverflow.com/a/19971550/934239
  return document.cookie.split(';').reduce(function(prev, c) {
    var arr = c.split('=');
    return (arr[0].trim() === cookie) ? arr[1] : prev;
  }, undefined);
}

var seed = getCookie("seed_goes_here");

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注意:上面的代码是未经测试的,仅用于说明这个想法.

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