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": "service-worker.js"
}
}
service-worker.js
Add the extension service worker by creating a file called service-worker.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:
- On the Developer Dashboard, click Add new item.
- Click Browse files, select the extension's zip file, and upload it.
- Go to the Package tab and click View public key.
When the popup is open, follow these steps:
- Copy the code in between
-----BEGIN PUBLIC KEY-----and-----END PUBLIC KEY-----. - Remove the newlines in order to make it a single line of text.
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.
Create an 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.
On the Create client ID page, select Chrome Extension. Fill out the name of the extension and place the extension ID at the end of the URL in the Application ID field.
Finish by clicking create. The console will provide an OAuth client ID.
Register OAuth in the 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 the browser icon to open index.html. Open the console and click the "FriendBlock Contacts" button. An OAuth token will appear 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 the correct result and enable it.
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.
Keep the generated API key for later use.
Create the 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.
