Add Google Oauth2 authenticator. The current Google OpenID authentication has been deprecated by Google and will NOT work for any new websites.

lib/auth/google_oauth2_authenticator.rb

@@ -0,0 +1,67 @@
+class Auth::GoogleOAuth2Authenticator < Auth::Authenticator
+
+  def name
+    "google_oauth2"
+  end
+
+  def after_authenticate(auth_hash)
+    session_info = parse_hash(auth_hash)
+    google_hash = session_info[:google]
+
+    result = Auth::Result.new
+    result.email = session_info[:email]
+    result.email_valid = session_info[:email_valid]
+    result.name = session_info[:name]
+
+    result.extra_data = google_hash
+
+    user_info = GoogleUserInfo.find_by(google_user_id: google_hash[:google_user_id])
+    result.user = user_info.try(:user)
+
+    if !result.user && !result.email.blank? && result.user = User.find_by(email: Email.downcase(result.email))
+      GoogleUserInfo.create({user_id: result.user.id}.merge(google_hash))
+    end
+
+    result
+  end
+
+  def after_create_account(user, auth)
+    data = auth[:extra_data]
+    GoogleUserInfo.create({user_id: user.id}.merge(data))
+  end
+
+  def register_middleware(omniauth)
+    omniauth.provider :google_oauth2,
+           :setup => lambda { |env|
+              strategy = env["omniauth.strategy"]
+              strategy.options[:client_id] = SiteSetting.google_oauth2_client_id
+              strategy.options[:client_secret] = SiteSetting.google_oauth2_client_secret
+           }
+  end
+
+  protected
+
+  def parse_hash(hash)
+    extra = hash[:extra][:raw_info]
+
+    h = {}
+
+    h[:email] = hash[:info][:email]
+    h[:name] = hash[:info][:name]
+    h[:email_valid] = hash[:extra][:raw_info][:email_verified]
+
+    h[:google] = {
+      google_user_id: hash[:uid] || extra[:sub],
+      email: extra[:email],
+      first_name: extra[:given_name],
+      last_name: extra[:family_name],
+      gender: extra[:gender],
+      name: extra[:name],
+      link: extra[:hd],
+      profile_link: extra[:profile],
+      picture: extra[:picture]
+    }
+
+    h
+  end
+end