Add Google Authentication (Users)

using Microsoft.Extensions.Options;
using Umbraco.Cms.Api.Management.Security;
using Umbraco.Cms.Core;

namespace MyCustomUmbracoProject.ExternalUserLogin.GoogleAuthentication;

public class GoogleBackOfficeExternalLoginProviderOptions : IConfigureNamedOptions<BackOfficeExternalLoginProviderOptions>
{
    public const string SchemeName = "Google";

    public void Configure(string? name, BackOfficeExternalLoginProviderOptions options)
    {
        if (name != Constants.Security.BackOfficeExternalAuthenticationTypePrefix + SchemeName)
        {
            return;
        }

        Configure(options);
    }

    public void Configure(BackOfficeExternalLoginProviderOptions options)
    {
        options.AutoLinkOptions = new ExternalSignInAutoLinkOptions(
            // must be true for auto-linking to be enabled
            autoLinkExternalAccount: true,

            // Optionally specify default user group, else
            // assign in the OnAutoLinking callback
            // (default is editor)
            defaultUserGroups: new[] { Constants.Security.EditorGroupAlias },

            // Optionally specify the default culture to create
            // the user as. If null it will use the default
            // culture defined in the web.config, or it can
            // be dynamically assigned in the OnAutoLinking
            // callback.
            defaultCulture: null,
            // Optionally you can disable the ability to link/unlink
            // manually from within the back office. Set this to false
            // if you don't want the user to unlink from this external
            // provider.
            allowManualLinking: true
        )
        {
            // Optional callback
            OnAutoLinking = (autoLinkUser, loginInfo) =>
            {
                // You can customize the user before it's linked.
                // i.e. Modify the user's groups based on the Claims returned
                // in the externalLogin info

                // see https://github.com/umbraco/Umbraco-CMS/issues/12487
                autoLinkUser.IsApproved = true;
            },
            OnExternalLogin = (user, loginInfo) =>
            {
                // You can customize the user before it's saved whenever they have
                // logged in with the external provider.
                // That is to sync the user's name based on the Claims returned
                // in the externalLogin info

                return true; //returns a boolean indicating if sign-in should continue or not.
            },
        };
    }
}

using Microsoft.AspNetCore.Authentication.Google;
using Microsoft.Extensions.Options;
using Umbraco.Cms.Api.Management.Security;
using Umbraco.Cms.Web.Common.Helpers;
using Umbraco.Cms.Web.UI.Custom;

namespace MyCustomUmbracoProject.ExternalUserLogin.GoogleAuthentication;

public class GoogleBackOfficeAuthenticationOptions : IConfigureNamedOptions<GoogleOptions>
{
    private readonly OAuthOptionsHelper _helper;

    public GoogleBackOfficeAuthenticationOptions(OAuthOptionsHelper helper)
    {
        _helper = helper;
    }

    public void Configure(GoogleOptions options)
    {
        // since we have access to dependency injection, these values can be read from the app settings using the IOptions pattern
        options.CallbackPath = "/umbraco-google-signin"; // can be anything as middleware will add this to the route table
        options.ClientId = "your client id for the google login provider";
        options.ClientSecret = "your client secret for the google login provider";
        options.Scope.Add("https://www.googleapis.com/auth/userinfo.email"); // email is needed for auto linking purposes

        // This will redirect error responses from the login provider towards the default umbraco oath login error page
        // which will try to display the error state in a meaningful way.
        // You can implement your own error handling by handling options.Events.OnAccessDenied & options.Events.OnRemoteFailure
        _helper.SetDefaultErrorEventHandling(options, GoogleBackOfficeExternalLoginProviderOptions.SchemeName);
    }

    public void Configure(string? name, GoogleOptions options)
    {
        // only configure the options if it is for the backend
        if (name == BackOfficeAuthenticationBuilder.SchemeForBackOffice(GoogleBackOfficeExternalLoginProviderOptions
                .SchemeName))
        {
            Configure(options);
        }
    }
}

using Umbraco.Cms.Api.Management.Security;
using Umbraco.Cms.Core.Composing;
using Umbraco.Cms.Web.UI.Custom;

namespace MyCustomUmbracoProject.ExternalUserLogin.GoogleAuthentication;

public class GoogleBackOfficeExternalLoginComposer : IComposer
{
    public void Compose(IUmbracoBuilder builder)
    {
        builder.Services.ConfigureOptions<GoogleBackOfficeExternalLoginProviderOptions>();
        builder.Services.ConfigureOptions<GoogleBackOfficeAuthenticationOptions>();

        builder.AddBackOfficeExternalLogins(logins =>
        {
            logins.AddBackOfficeLogin(
                backOfficeAuthenticationBuilder =>
                {
                    // this Add... method will be part of the OathProvider nuget package you install
                    backOfficeAuthenticationBuilder.AddGoogle(
                        BackOfficeAuthenticationBuilder.SchemeForBackOffice(
                            GoogleBackOfficeExternalLoginProviderOptions
                                .SchemeName)!,
                        options =>
                        {
                            // need to give an empty action here for the options pattern configuration to work
                            // if you do not wish to use the umbraco default error handling and hardcode all your values instead of injecting them,
                            // you can set the configuration right here instead. You can then remove the `GoogleBackOfficeAuthenticationOptions` class
                        });
                });
        });
    }
}

{
  "$schema": "../../umbraco-package-schema.json",
  "name": "My Auth Package",
  "allowPublicAccess": true,
  "extensions": [
    {
      "type": "authProvider",
      "alias": "My.AuthProvider.Google",
      "name": "My Google Auth Provider",
      "forProviderName": "Umbraco.Google",
      "meta": {
        "label": "Login with Google"
      }
    }
  ]
}