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OAuth2: Authenticate users with Google

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Caution

This page was migrated directly from the Manifest V2 documentation set. It has not yet been validated for compliance with Manifest V3.

OAuth2 is the industry-standard protocol for authorization. It provides a mechanism for users to grant web and desktop applications access to private information without sharing their username, password and other private credentials.

This tutorial builds an extension that accesses a user's Google contacts using the Google People API and the Chrome Identity API. Because extensions don't load over HTTPS, can't perform redirects or set cookies, they rely on the Chrome Identity API to use OAuth2.

Get started

Begin by creating a directory and the following starter files.

manifest.json

Add the manifest by creating a file called manifest.json and include the following code.

{
"name": "OAuth Tutorial FriendBlock",
"version": "1.0",
"description": "Uses OAuth to connect to Google's People API and display contacts photos.",
"manifest_version": 3,
"action": {
"default_title": "FriendBlock, friends face's in a block."
},
"background": {
"service_worker": "background.js"
}
}

background.js

Add the background service worker by creating a file called background.js and include the following code.

chrome.action.onClicked.addListener(function() {
chrome.tabs.create({url: 'index.html'});
});

index.html

Add an HTML file called index.html and include the following code.

<html>
<head>
<title>FriendBlock</title>
<style>
button {
padding: 10px;
background-color: #3C79F8;
display: inline-block;
}
</style>
</head>
<body>
<button>FriendBlock Contacts</button>
<div id="friendDiv"></div>
</body>
</html>

Keep a consistent extension ID

Preserving a single ID is essential during development. To keep a consistent ID, follow these steps:

Upload extension to the developer dashboard

Package the extension directory into a .zip file and upload it to the Chrome Developer Dashboard without publishing it:

  1. On the Developer Dashboard, click Add new item.
  2. Click Browse files, select the extension's zip file, and upload it.
  3. Go to the Package tab and click View public key.
Developer Dashboard Package tab

When the popup is open, follow these steps:

  1. Copy the code in between -----BEGIN PUBLIC KEY----- and -----END PUBLIC KEY-----.
  2. Remove the newlines in order to make it a single line of text.
Public key popup

Add the code to the manifest.json under the "key" field. This way the extension will use the same ID.

{ // manifest.json 
"manifest_version": 3,
...
"key": "ThisKeyIsGoingToBeVeryLong/go8GGC2u3UD9WI3MkmBgyiDPP2OreImEQhPvwpliioUMJmERZK3zPAx72z8MDvGp7Fx7ZlzuZpL4yyp4zXBI+MUhFGoqEh32oYnm4qkS4JpjWva5Ktn4YpAWxd4pSCVs8I4MZms20+yx5OlnlmWQEwQiiIwPPwG1e1jRw0Ak5duPpE3uysVGZXkGhC5FyOFM+oVXwc1kMqrrKnQiMJ3lgh59LjkX4z1cDNX3MomyUMJ+I+DaWC2VdHggB74BNANSd+zkPQeNKg3o7FetlDJya1bk8ofdNBARxHFMBtMXu/ONfCT3Q2kCY9gZDRktmNRiHG/1cXhkIcN1RWrbsCkwIDAQAB",
}

Compare IDs

Open the Extensions Management page at chrome://extensions, ensure Developer mode is enabled, and upload the unpackaged extension directory. Compare the extension ID on the extensions management page to the Item ID in the Developer Dashboard. They should match.

The ID of the extension match

Create OAuth client ID

Navigate to the Google API console and create a new project. Once ready, select Credentials in the sidebar, click Create credentials and choose OAuth client ID.

Create credentials for extension

On the Create client ID page, select Chrome App. Fill out the name of the extension and place the extension ID at the end of the URL in the Application ID field.

Fill out extension information

Finish by clicking create. The console will provide an OAuth client ID.

Register OAuth in manifest

Include the "oauth2" field in the extension manifest. Place the generated OAuth client ID under "client_id". Include an empty string in "scopes" for now.

{
"name": "OAuth Tutorial FriendBlock",
...
"oauth2": {
"client_id": "yourExtensionOAuthClientIDWillGoHere.apps.googleusercontent.com",
"scopes":[""]
},
...
}

Initiate first OAuth flow

Register the identity permission in the manifest.

{
"name": "OAuth Tutorial FriendBlock",
...
"permissions": [
"identity"
],
...
}

Create a file to manage the OAuth flow called oauth.js and include the following code.

window.onload = function() {
document.querySelector('button').addEventListener('click', function() {
chrome.identity.getAuthToken({interactive: true}, function(token) {
console.log(token);
});
});
};

Place a script tag for oauth.js in the head of index.html.

...
<head>
<title>FriendBlock</title>
...
<script type="text/javascript" src="oauth.js"></script>
</head>
...

Reload the extension and click on the browser icon to open index.html. Open the console and click on the "FriendBlock Contacts" button. An OAuth token will appear in the console.

View the token in the console

Enable the Google People API

Return to the Google API console and select Library from the sidebar. Search for "Google People API", click on the correct result and enable it.

Enable the People API

Add the Google People API client library to "scopes" in the extension manifest.

{
"name": "OAuth Tutorial FriendBlock",
...
"oauth2": {
"client_id": "yourExtensionOAuthClientIDWillGoHere.apps.googleusercontent.com",
"scopes": [
"https://www.googleapis.com/auth/contacts.readonly"
]
},
...
}

Return to the Google API console and navigate back to credentials. Click "Create credentials" and select "API key" from the dropdown.

Create People API credentials

Keep the generated API key for later use.

Create first API request

Now that the extension has proper permissions, credentials, and can authorize a Google user, it can request data through the People API. Update the code in oauth.js to match below.

window.onload = function() {
document.querySelector('button').addEventListener('click', function() {
chrome.identity.getAuthToken({interactive: true}, function(token) {
let init = {
method: 'GET',
async: true,
headers: {
Authorization: 'Bearer ' + token,
'Content-Type': 'application/json'
},
'contentType': 'json'
};
fetch(
'https://people.googleapis.com/v1/contactGroups/all?maxMembers=20&key=API_KEY',
init)
.then((response) => response.json())
.then(function(data) {
console.log(data)
});
});
});
};

Replace API_KEY with the API key generated from the Google API console. The extension should log a JSON object that includes an array of people/account_ids under the memberResourceNames field.

Block faces

Now that the extension is returning a list of the user's contacts, it can make additional requests to retrieve those contact's profiles and information . The extension will use the memberResourceNames to retrieve the photo information of user contacts. Update oauth.js to include the following code.

window.onload = function() {
document.querySelector('button').addEventListener('click', function() {
chrome.identity.getAuthToken({interactive: true}, function(token) {
let init = {
method: 'GET',
async: true,
headers: {
Authorization: 'Bearer ' + token,
'Content-Type': 'application/json'
},
'contentType': 'json'
};
fetch(
'https://people.googleapis.com/v1/contactGroups/all?maxMembers=20&key=<API_Key_Here>',
init)
.then((response) => response.json())
.then(function(data) {
let photoDiv = document.querySelector('#friendDiv');
let returnedContacts = data.memberResourceNames;
for (let i = 0; i < returnedContacts.length; i++) {
fetch(
'https://people.googleapis.com/v1/' + returnedContacts[i] +
'?personFields=photos&key=API_KEY',
init)
.then((response) => response.json())
.then(function(data) {
let profileImg = document.createElement('img');
profileImg.src = data.photos[0].url;
photoDiv.appendChild(profileImg);
});
};
});
});
});
};

Reload and return to the extension. Click the FriendBlock button and ta-da! Enjoy contact's faces in a block.

Contact faces in a block

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