OpenSSH's `ssh-keygen` command just got a great upgrade.In today's episode, I cover how Ed25519 keys are now the default, and how it probably doesn't impact ...
  • aard@kyu.de
    20·
    10 months ago

    A surprising amount of services (including Azure last I tried) can only handle RSA keys, so after trying ecdsa only for a while I ended up adding a RSA key again.

    With that said - it’s 2023, in almost all cases you should have your keys in a hardware module nowadays, in which case you’d use a different command for keygeneration.

      • deepdive@lemmy.worldEnglish
        3·
        10 months ago

        Strange enough TLS 1.3 still doesn’t support signed ed25519 certificates :| P‐256, NIST P‐384 or NIST P‐521 curves are known to be “backdoored” or having deliberately chosen mathematical weakness. I’m not an expert and just a noob security/selfhoster enthusiast but I don’t want to depend on curves made by NSA or other spy agencies !

        I also wondering if the EU isn’t going to implement something similar with all their new spying laws currently discussed…

      • aard@kyu.de
        5·
        10 months ago

        Easiest and most affordable is probably a security key like the Nitrokey or the https://www.yubico.com/. I personally don’t like the company behind yubikey much, but if you want something small you can always leave in the device that’s pretty much your only option.

        For “cheaper, but a bit more effort” would be just getting a smartcard blank, a card reader (if you’re not lucky enough to have a notebook or computer with one built in), and then either write your own applet, or use one of the available opensource ones, and upload it to the card. A variant of that would be the Fidesmo card, where you get a card and their applet.

        Or you just use the TPM you may have in your system - though you’ll need to be careful with that: Typically one reason for using a hardware token is to make sure keys can’t get extracted, while TPMs often do allow key extraction. Software to make that work would be opencryptoki.

        Generally you’d use PKCS#11 to have the various components talk to each other. On your average Linux pretty much everything but GnuPG place nice. with PKCS#11. Typically you end up with pcscd to interface with the smartcard (the above USB tokens are technically also just USB smartcards), OpenSC as layer to provide PKCS#11 on top, and software (like OpenSSH) then talks to that.

        All of that should be available as packages in any Linux distribution nowadays - and typically will also provide p11-kit configured to use a proxy library to make multiple token sources easily available, and avoid blocking on concurrent access.

        ssh-add supports adding keys from pkcs#11 providers to the SSH agent (search pkcs11 in ssh-add manpage), with some distribution (like RedHat) also carrying patches allowing you to only select individual tokens for adding.

        If you’re also using GnuPG it gets more complicated - you pretty much have two options: Stick with PKCS#11, in which case you’d replace GPGs own smartcard agent with gnupg-pkcs11-scd, or you use GPGs own card implementation, in which case you can forget pretty much everything I wrote above, and just follow the security key manual for setting up a GPG card, enable SSH agent support in the GPG agent, and just use that for SSH authentication.