Smartphone-based two-factor authentication
If the only protection between an attacker and a user account is a password, security-conscious administrators start to get nervous – and rightly so. Although strong passwords can be enforced, carelessness cannot be ruled out. Two-factor authentication (2FA) provides additional protection against unwanted visitors, even if a user chooses a weak password. While the user's password remains as the first authentication factor, a six-digit numerical code with a limited validity period generated by a smartphone authenticator app adds a second factor.
In this article, I will show how to require a one-time code at login (in addition to the user's password) by creating an app on the user's smartphone. This procedure was developed by the Initiative For Open Authentication (OATH) and has been an Internet Engineering Task Force (IETF) standard since 2011.
Getting Started
For this article, I am using Ubuntu 20.04, but the procedure is very similar on other distributions. You have a Linux client and a server. On the server, which goes by the name of influx in this example, I have an account belonging to user bob. Bob has been logging in with a password only. However, his organization now wants to switch Bob's account to 2FA.
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