On Wed, 25 Aug 2021, James Bottomley wrote: > > Would it be possible to extend OpenSSH support to include “rsa-sk” > > keys? > > > > Not sure what the process is, but could development of it be > > sponsored? > > The FIDO standard requires ECDSA keys (mainly, I suspect, because some > of the space constraints in the protocol are too small for RSA) so I > don't believe, even if you hacked the standard to support RSA keys, > that it would work in practice. AFAIK the FIDO2 standards include RSA keys, though I'm not aware of any physical FIDO tokens that support them (caveat: I haven't looked much). Adding another key type to OpenSSH is expensive - it needs to be plumbed through a lot of code, tests need to be written, documentation updated and fuzzing seed corpora need to be created. Maintenance once it has been added is less onerous, but still a factor - each supported key type basically increases the multiple (currently 7) of code paths that need care, test coverage and fuzzing. OTOH it's really hard to *remove* a key type, because there's always someone, somewhere with some use case that wants it. I'm expecting a big fight when I eventually push to remove ssh-dss, an algorithm that is demonstrably insecure, despite it being disabled by default for a long time. So anything we add, we're almost certainly on the hook to support for a decade+ Because of this, I'm quite reticent to add more key types without a really compelling reason. In the case of RSA/FIDO, it's really to support a single vendor (admittedly an important one), but using an algorithm (RSA) which almost everyone is moving away from in favour of elliptic-curve crypto, and that seems was chosen to support a legacy hardware standard (TPM 1.x) that is already superseded. It feels like adding FIDO/RSA is like running towards where the ball was a year ago rather than where it will be in the near future. -d _______________________________________________ openssh-unix-dev mailing list openssh-unix-dev@xxxxxxxxxxx https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev
