SoftU2F-Win VS openssh-sk-winhello

It's been a few years, but the main references I remember using:

1. Windows: https://github.com/frankmorgner/vsmartcard/tree/master/virtu..., which is a fix-up of the older https://www.codeproject.com/Articles/134010/An-UMDF-Driver-f..., and https://github.com/Watfaq/SoftU2F-Win/tree/master/SoftU2FDri.... Note that neither of these actually implement CTAP2.

2. Linux: There's plenty to refer to on HID gadgets, but https://blog.hansenpartnership.com/webauthn-in-linux-with-a-... and the code at https://git.kernel.org/pub/scm/linux/kernel/git/jejb/fido2-c... were my entrypoint.

3. Mac: I ended up not implementing a Mac version, but GitHub themselves used to support a CTAP1/U2F software authenticator, now archived at https://github.com/github/SoftU2F. I was going to work from that.

For the service I looked at different software "devices" interfacing with these kinds of drivers (or just the browser directly in Firefox's case).

1. Generic NIST SP 800-73 PIV: https://github.com/CCob/PIVert. Very limited scope, pentest tool with no extraneous features. It uses the BixVReader driver.

For Windows, it seems it's possible[0, see footnote], however there are problems like general incompatibilities [1], and official support status is " We have this in our backlog. At this point it's not prioritized.".

0: https://github.com/tavrez/openssh-sk-winhello

0.footnote: "Windows Hello also supports other types of authenticators like internal TPM device(if they support generating ECDSA or Ed25519 keys, they can be used instead of FIDO/U2F security keys)."

1: https://github.com/tavrez/openssh-sk-winhello/issues

2: https://github.com/PowerShell/Win32-OpenSSH/issues/1804#issu...

Awesome article! Also found this tool (tavrez/OpenSsh-sk-winhello) for windows that lets you do this without admin access

Which is also how they are generated when retrieving them on a new computer via ssh-keygen -K since I used the application=ssh:yubikey_5 flag when first generating them. So something like ssh-keygen -t ed25519-sk -O resident -O application=ssh:yubikey_5c, but because I am on Windows I also had the -w winhello.dll flag (In case anyone stumbles on this question)

This is what i used but YMMV https://github.com/tavrez/openssh-sk-winhello/releases/tag/v2.0.0

> Because AFAIK, (Fido) yubikey support is still missing.

Correct, hopefully Microsoft will provide an updated SSH client soon. It only requires recompiling OpenSSH with the correct flags.

Alternatively, use these build instruction for openssh with FIDO for windows:

https://gist.github.com/martelletto/6a7cf806c6433ac9ce71d66a...

> Using either the PKCS#11 support or the gpg applet requires some extra piece of software

For those wanting to do that, here are some ways:

Using a premade dll:

https://github-wiki-see.page/m/mooltipass/minible/wiki/Setti...

Or with a middleware:

https://github.com/mgbowen/windows-fido-bridge

Using the Hello API:

https://github.com/tavrez/openssh-sk-winhello

Given how many people came with their own ways, I believe there's enough demand for Microsoft to fix that.

My knowledge of WebAuthn is limited but their invocation of the relevant API seems like it should work for fingerprints also.

[1] https://github.com/tavrez/openssh-sk-winhello