ASP.NET Identity Two Factor Authentication Email Sendgrid OTP

A modification for the ASP.NET CORE Identity Razor Pages Scaffolding for using Email with SendGrid as IEmailSender as two factor authentication with the OTP

The main changes from the default Scaffolding are:

Path ~\Areas\Identity\Pages\Account\LoginWith2fa.cshtml.cs

method OnGetAsync

• Generates the new OTP
• Remove previous stored OTP
• Save / Set the new one
• Send it by email

method OnPostAsync

• Replace the call to TwoFactorAuthenticatorSignInAsync for TwoFactorSignInAsync where you can inform you will use TokenOptions.DefaultEmailProvider

Notes

This is not an elegant solution because several aspects:

• It invalidates the Authenticator App Solution that Microsoft brings to us by default of setting an Authenticator.
• The OTP is saved in plain text, It should be saved encrypted and encrypt the code informed by the user to compare.
• This repository is just reflecting a PoC as research purpose, don't use it in production without caring of this notes.
• SendGrid configuration comes from user secrets, you can find a reference here
• Remember to replace the DefaultConnection in ConnectionStrings, in appsettings.json
• The original idea and modifications are applied following the Microsoft Docs guidelines for Multi-Factor Authentication