Software mock for yubikey / pkcs11

[emostov]

In order to do automated testing of our yubikey functionality, we need to be able to mock a yubikey card on any machine.

We may be able to do this by finding a PKCS 11 emulator.

Resources to look into:

• https://github.com/Yubico/yubico-piv-tool/blob/master/ykcs11/tests/ykcs11_tests.c

[cr-tk]

I'm aware of https://github.com/opendnssec/SoftHSMv2 as a software PKCS#11 emulator. As discussed, I doubt that it'll behave exactly like the Yubikey 5 series firmwares would, but it may be a start.

[cr-tk]

Looking at the open SoftHSMv2 issues and PRs, it appears that, as expected, it behaves differently under some edge cases than other PKCS#11 targets would, see OpenSC/libp11#440 . This may be an isolated issue, but highlights the need to check against actual Yubikey firmware behavior at some later point even if tests based on SoftHSMv2 run through without issues.