5 ms·

An ssh key is 2FA

michaelmior 7y ago
How so? An SSH key is a single factor. You could argue that a password-protected private key provides a second factor, but that still falls in the category of "something you know."
- will4274 7y ago
  How many people can recite their SSH key? Surely an SSH key is "something you have".
  - wnevets 7y ago
    Having two different static passwords on an account isn't actually two different factors, whether you can recite them or not. The fact that one time passwords expire and change is what makes them a different factor than a static password.
    - thaumasiotes 7y ago
      > The fact that one time passwords expire and change is what makes them a different factor than a static password. If you're getting your 2FA code by SMS message or the like, this can be true. If you're using TOTP (e.g. Google Authenticator), that's just as static as your other passwords. The TOTP code never expires nor changes. What changes is the code you're supposed to send over the wire.
      - theamk 7y ago
        Eh? TOTP usually expire in 60 seconds, so in most cases even if you accidentally leak it, it will be safe. (and you are not likely to leak it anyway -- with something that changes that often, you are not going to have an incentive to write it to files)
        thaumasiotes 7y ago
        A 60-second TOTP code is a fully deterministic function of a permanent, unchangeable secret. That's why you and the server can agree on what the code should be without needing to communicate beyond setting up the code originally. This makes it identical to a password from a theoretical perspective. There's really no difference between a TOTP secret that you keep in a TOTP app and haven't memorized, and a password you keep in your password manager and also haven't memorized. Both are "something you know", and nothing else. You're correct that leaking a temporary code from a single login attempt doesn't compromise the TOTP secret. That is an artifact of the login process, not of whether the mechanism is labeled "2FA" or "password". You can do the same thing while calling the secret a password: https://en.wikipedia.org/wiki/Secure_Remote_Password_protocol https://en.wikipedia.org/wiki/Secure_Remote_Password_protoco...
        theamk 7y ago
        I disagree, I believe TOTP belongs firmly in the "something you have" category. You cannot memorize TOTP password, nor you can store in your password manager. You also cannot pass that knowledge to another person. So this is more like a public key than a password. Ultimately, everything is "permanent, unchangeable secret", including private key and biometric data. Where the data is stored and how is it accessed makes all the difference. I could not find the original definition of "something you have", but modern standards like PCI actually give OTP auth as an example of "something you have" (p. 4 of [1]) (I am not looking at the degenerate case of running TOTP app on the same device / same security domain -- it does not describe most cases, and there are some fairly straightforward technical measures to defeat this) [1] https://www.pcisecuritystandards.org/pdfs/Multi-Factor-Authentication-Guidance-v1.pdf https://www.pcisecuritystandards.org/pdfs/Multi-Factor-Authe...
        thaumasiotes 7y ago
        > You cannot memorize TOTP password, nor you can store in your password manager. You also cannot pass that knowledge to another person. But none of these things are true. For example, my most recent job involved sharing a 2FA-protected online account. We all had the code.
- thaumasiotes 7y ago
  A TOTP challenge is also "something you know", which is a really large portion of total "2FA".
ralph84 7y ago
An SSH key is one factor. There are various methods for protecting the key with additional factors, but none of the git hosts provide a way to require those additional factors. So as an org owner you're left either trusting every one of your users not to get sloppy with keys, or installing spyware on their computers to make sure they're not using unprotected keys.

An ssh key is 2FA

How so? An SSH key is a single factor. You could argue that a password-protected private key provides a second factor, but that still falls in the category of "something you know."

will4274 7y ago
How many people can recite their SSH key? Surely an SSH key is "something you have".
- wnevets 7y ago
  Having two different static passwords on an account isn't actually two different factors, whether you can recite them or not. The fact that one time passwords expire and change is what makes them a different factor than a static password.
  - thaumasiotes 7y ago
    > The fact that one time passwords expire and change is what makes them a different factor than a static password. If you're getting your 2FA code by SMS message or the like, this can be true. If you're using TOTP (e.g. Google Authenticator), that's just as static as your other passwords. The TOTP code never expires nor changes. What changes is the code you're supposed to send over the wire.
    - theamk 7y ago
      Eh? TOTP usually expire in 60 seconds, so in most cases even if you accidentally leak it, it will be safe. (and you are not likely to leak it anyway -- with something that changes that often, you are not going to have an incentive to write it to files)
      - thaumasiotes 7y ago
        A 60-second TOTP code is a fully deterministic function of a permanent, unchangeable secret. That's why you and the server can agree on what the code should be without needing to communicate beyond setting up the code originally. This makes it identical to a password from a theoretical perspective. There's really no difference between a TOTP secret that you keep in a TOTP app and haven't memorized, and a password you keep in your password manager and also haven't memorized. Both are "something you know", and nothing else. You're correct that leaking a temporary code from a single login attempt doesn't compromise the TOTP secret. That is an artifact of the login process, not of whether the mechanism is labeled "2FA" or "password". You can do the same thing while calling the secret a password: https://en.wikipedia.org/wiki/Secure_Remote_Password_protocol https://en.wikipedia.org/wiki/Secure_Remote_Password_protoco...
        theamk 7y ago
        I disagree, I believe TOTP belongs firmly in the "something you have" category. You cannot memorize TOTP password, nor you can store in your password manager. You also cannot pass that knowledge to another person. So this is more like a public key than a password. Ultimately, everything is "permanent, unchangeable secret", including private key and biometric data. Where the data is stored and how is it accessed makes all the difference. I could not find the original definition of "something you have", but modern standards like PCI actually give OTP auth as an example of "something you have" (p. 4 of [1]) (I am not looking at the degenerate case of running TOTP app on the same device / same security domain -- it does not describe most cases, and there are some fairly straightforward technical measures to defeat this) [1] https://www.pcisecuritystandards.org/pdfs/Multi-Factor-Authentication-Guidance-v1.pdf https://www.pcisecuritystandards.org/pdfs/Multi-Factor-Authe...
        thaumasiotes 7y ago
        > You cannot memorize TOTP password, nor you can store in your password manager. You also cannot pass that knowledge to another person. But none of these things are true. For example, my most recent job involved sharing a 2FA-protected online account. We all had the code.
thaumasiotes 7y ago
A TOTP challenge is also "something you know", which is a really large portion of total "2FA".

ralph84 7y ago

An SSH key is one factor. There are various methods for protecting the key with additional factors, but none of the git hosts provide a way to require those additional factors. So as an org owner you're left either trusting every one of your users not to get sloppy with keys, or installing spyware on their computers to make sure they're not using unprotected keys.