![]() ![]() In the interest of simplicity, I’ve only shown basic usage of the library. The library also allows you to validate the generated 2FA codes, assuming they are valid for two 30-second windows. by generating a QR code) to generate 2FA codes, or use it to generate 2FA codes directly. After generating a secret from the otp library, you can either share it with your authenticator app (e.g. My earlier article showed how easy it is to work with 2FA codes using a TOTP library in C#, and in Go it’s no different. Or, you can accept the security tradeoff knowing that the 2FA codes are only valid for a minute, giving little opportunity for an attacker to exploit them. To do this, you’ll need to add additional state and logic to your application. In theory, you should prevent the application from accepting the same code twice, because they’re supposed to be one-time-passwords. Entering anything else (other than the current or previous code) returns false.Entering the same code after that returns false.Entering the same code still returns true within 30 seconds after it has stopped displaying in the authenticator app.Entering the same code twice returns true.Entering a code shown by the authenticator app returns true.While playing with this, you’ll notice that: TOTP in Go – Getting Startedīefore looking at TOTP, let’s first do the usual steps to create a simple program in Go:ĬodeIsValid := totp.Validate(input2faCode, secret)įmt.Println("Code is valid: ", codeIsValid) This might all sound a little abstract, but it will become clear shortly once we go through implementing TOTP on the server side and testing it out. Usually the server will accept that code during these 30 seconds and also for an additional 30 seconds while the next code is displayed. Once it acquires the shared secret from the server – typically by scanning a QR code – it then generates codes every 30 seconds. The client usually takes the form of an authenticator app – such as Google Authenticator, Microsoft Authenticator, or Authy – on a mobile device. The codes are generated based on a shared secret and the current time, so as long as the client and server are using the same secret and generate the codes at roughly the same time, they will match. The way TOTP works is that the client and server each generate a code, and these have to match. Among all these options, the Time-Based One-Time Password (TOTP) protocol is a simple way to provide the benefits of 2FA without the disadvantages of other options (such as SMS gateways being unreliable and expensive, and biometrics being complex to implement). Logins that use Two-Factor Authentication (2FA) typically rely on the user’s password as the first factor, as well as a second factor that could be anything from an email/SMS to something biometric. In this article, I’ll show how to do the same thing in Go. Back in 2019, I wrote “ Using Time-Based One-Time Passwords for Two-Factor Authentication“, explaining how to allow a server written in C# to generate and verify codes in sync with authenticator apps. ![]()
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