chrome.webRequest not working?

Question

I'm trying to implement the chrome.webRequest API in my extension but for some reason it's just not working no matter what I do. Can someone post an example of usage? or correct my mistakes? Basically what I'm trying to do is to intercept the recieved headers from a response.

This is an implementation for onBeforeSendHeaders but I'd like to use OnHeadersRecieved as well :

var requestFilter = {
    urls: [ "<all_urls>" ]
  },
  // The 'extraInfoSpec' parameter modifies how Chrome calls your
  // listener function. 'requestHeaders' ensures that the 'details'
  // object has a key called 'requestHeaders' containing the headers,
  // and 'blocking' ensures that the object your function returns is
  // used to overwrite the headers
  extraInfoSpec = ['requestHeaders','blocking'],
  // Chrome will call your listener function in response to every
  // HTTP request
  handler = function( details ) {
    alert(details);
    var headers = details.requestHeaders,
      blockingResponse = {};

    // Each header parameter is stored in an array. Since Chrome
    // makes no guarantee about the contents/order of this array,
    // you'll have to iterate through it to find for the
    // 'User-Agent' element
    for( var i = 0, l = headers.length; i < l; ++i ) {
      if( headers[i].name == 'User-Agent' ) {
        headers[i].value = '>>> Your new user agent string here <<<';
        break;
      }
      // If you want to modify other headers, this is the place to
      // do it. Either remove the 'break;' statement and add in more
      // conditionals or use a 'switch' statement on 'headers[i].name'
    }

    blockingResponse.requestHeaders = headers;
    return blockingResponse;
  };

chrome.webRequest.onBeforeSendHeaders.addListener( handler, requestFilter, extraInfoSpec );

this is my manifest file:

    {
   "background_page": "iRBackground.html",
   "browser_action": {
      "default_icon": "Off.png",
      "popup": "iRMenu.html"
   },
   "content_scripts": [ {
      "js": [ "Content.js" ],
      "matches": [ "http://*/*" ],
      "run_at": "document_start"
   } ],
   "description": "***",
   "icons": {
      "128": "On128x128.png",
      "16": "On.png",
      "48": "On48x48.png"
   },
   "key": "****",
   "manifest_version": 2,
   "name": "***",
   "permissions": [ "tabs", "notifications", "unlimitedStorage", "webRequest", “webRequestBlocking”, “<all_urls>”],
   "update_url": "***/Chrome/UpdateVersion.xml",
   "version": "1.3"
}

the error I get from Chrome is: Uncaught TypeError: Cannot read property 'onBeforeSendHeaders' of undefined

Anyone see anything wrong??? thanks

Answer 1

Well for an example of usage I can give you this working code. I wrote it this way because the other way seems backwards to me but that is just my personal preference, they should both work the same.

Manifest

{   "name": "Chrome webrequest test",   "version": "0.1",   "description": "A test for webrequest",   "manifest_version": 2,   "permissions": [     "<all_urls>","webRequest","webRequestBlocking"   ],   "background": {     "scripts": ["bgp.js"],     "persistent": true   } } 

bgp.js

chrome.webRequest.onBeforeSendHeaders.addListener(function(details){   //console.log(JSON.stringify(details));   var headers = details.requestHeaders,   blockingResponse = {};    // Each header parameter is stored in an array. Since Chrome   // makes no guarantee about the contents/order of this array,   // you'll have to iterate through it to find for the   // 'User-Agent' element   for( var i = 0, l = headers.length; i < l; ++i ) {     if( headers[i].name == 'User-Agent' ) {       headers[i].value = '>>> Your new user agent string here <<<';       console.log(headers[i].value);       break;     }     // If you want to modify other headers, this is the place to     // do it. Either remove the 'break;' statement and add in more     // conditionals or use a 'switch' statement on 'headers[i].name'   }    blockingResponse.requestHeaders = headers;   return blockingResponse; }, {urls: [ "<all_urls>" ]},['requestHeaders','blocking']); 

Answer 2

I just fixed this in my extension here: https://github.com/devinrhode2/tweet-bar What I needed to do was use chrome.webRequest.onBeforeSendHeaders.addListener, but that also meant adding in the webRequest, webRequestBlocking permissions.. would be better to use declarativeWebRequest, but this project isn't that important to me.

Key things:

• manifest.json "background": { "persistent": true,
• "permissions": [ "webRequest", "webRequestBlocking",

When you make these changes in the manifest.json, you should actually consider re-installing the extension just to make sure the change is being picked up.

This is my filter code. Yours should not be identical. See the docs here https://developer.chrome.com/extensions/webRequest

chrome.webRequest.onBeforeSendHeaders.addListener((req) => {
  console.log('onBeforeSendHeaders');
  req.requestHeaders.forEach(function(header, index){
    console.log(header.name+':', header.value);
    if (headers[header.name.toLowerCase()]) {
      console.log('set header:'+header.name, 'to:'+headers[header.name.toLowerCase()]);
      req.requestHeaders[index].value = headers[header.name.toLowerCase()]
    }
  })
  return {requestHeaders: req.requestHeaders};
},{
  urls: ['https://twitter.com/i/tweet/create'],
  types: ["xmlhttprequest"]
},[
  'blocking',
  'requestHeaders'
]);

I also added these headers to my xhr request, which doesn't hurt, makes you appear more similar to the normal site:

  //add headers:
  var headers = {
    'content-type': 'application/x-www-form-urlencoded',
    accept: 'application/json, text/javascript, */*; q=0.01',
    origin: 'https://twitter.com',
    referer: 'https://twitter.com/',
    'x-requested-with': 'XMLHttpRequest'
  };
  console.log('change')
  Object.keys(headers).forEach((header) => {
    postXhr.setRequestHeader(header, headers[header]);
  })