Create Google Drive App to View and Upload Files Using OAuth 2.0 and Flask

For authentication and authorization processes, we can use OAuth 2.0 framework. It is an industry standard authorization protocol. This is a direct authentication pattern. So users can login using their other public profiles. No need to register and enter password. Because of that, this is often called the password anti-pattern.

How Aouth works?

When web application redirects a browser to a Google URLauthorization sequence begins; the URL includes query parameters that indicate the type of access being requested. Google manages the user authentication and session selection. The result is an authorization code, which the application can exchange for an access token and a refresh token [6].

Authentication process - source - https://developers.google.com/identity/protocols/OAuth2

The application should store the refresh token for future use and use the access token to access a Google API. Once the access token expires, the application uses the refresh token to obtain a new one[6].

Here, we are creating a web application to  login to google using AOuth 2.0 ,view files from google drive and upload files to google drive.

1. Create / Register google app

• Go to https://console.developers.google.com
• Create a new project

• Enter project name and continue

• Click on "Enable services and APIs" button and enable google drive api
• Then, Add credentials for the project

• create OAuth client ID using below values

• Download the json file and rename it as client_id.json
• 
  

2. Create web application

• Install following dependancies

pip install flask google-api-python-client

pip install oauth2client

• Create home page  to do the OAuth authentication on behalf of the logged in user.

 get_credentials()- checks the local access token file credentials

 fetch() -that displays the list of all root folders ,files and documents

In here if the user is not logged in browser redirect to google login page by calling the below function. Otherwise, using authorized code, app loads google drive files from the authorized user account.

• callback function

If the user is not loged in , application calls this function. Then using google app client id key and secret key application sends request to login, then server pass the authorized token values.

• file upload function

# upload file to google drive@app.route('/uploads', methods=['GET', 'POST'])
def upload():
    credentials = get_credentials()
    http = credentials.authorize(httplib2.Http())
    service = discovery.build('drive', 'v3', http=http)

    if request.method == 'POST':
        # check if the post request has the file part        

if 'file' not in request.files:

            print('no file part')
            return redirect(request.url)
        file = request.files['file']

        # if user does not select file, browser also submit a empty part

 without filename

        if file.filename == '':

            print('no selected file')
            return redirect(request.url)
        if file:
            filename = file.filename
            print(filename)

            #set write access to upload folder            os.chmod(UPLOAD_FOLDER, 0o777)
            os.access('files', os.W_OK)  # Check for write access            os.access('files', os.R_OK)

            #save file in upload folder            file.save(os.path.join(app.config['UPLOAD_FOLDER'], filename))

            #get file path            filepath=os.path.join(app.config['UPLOAD_FOLDER'], filename)

            #set file meta data            file_metadata = {'name': filename}

            #set upload file mime type            media = MediaFileUpload(filepath, mimetype='image/png')
            file = service.files().create(body=file_metadata,

media_body=media,fields='id').execute()
            print ('File ID: %s' % file.get('id'))

    return render_template('success.html')

Visit https://github.com/Madhushani96/Aouth2.0_flask_web_application to download the code

3.Output

4. Resources

[1] https://developers.google.com/drive/api/v3/about-sdk

[2] https://developers.google.com/drive/api/v3/manage-uploads

[3] https://oauth.net/2/

[4] https://console.cloud.google.com

[5] https://flask-oauthlib.readthedocs.io/en/latest/oauth2.html

[6] https://developers.google.com/identity/protocols/OAuth2