With some easy and fast steps, you can enable Zammad to authenticate your users via Google.
Hint
Prior Zammad 2.9 it was necessary to activiate the Google+ API - it's deprecated, thus this authentication will only work with Zammad 2.9 and later.
First of all, we need to create a new project - you can skip this step if you already have one.
Hint
Use this link to create a new project: https://console.cloud.google.com/projectcreate
Now expand the menu, expand "APIs & Services" and select "Credentials". Go to the tab "OAuth consent screen" first and ensure to fill in the requested information - without doing so you can't create credentials!
After filling in and savingthe consent screen information, you can change to "Credentials" tab and create new "OAuth client ID"-Credentials.
Fill in the neceassary information, for restrictions you need the following (replace zammad_host with your FQDN):
Aplication type
[x] Web application
Authorized JavaScript origins
https://zammad_host/
Authorized redirect URIs
https://zammad_host/auth/google_oauth2/callback
After creating the credentials, go to your Zammad installation and navigate to "Admin -> Security -> Third Party Applications" -> Google. Enter your Client ID and Client secret here.
After submitting, the login via Google can be used.