In particular on Windows, the `transport.TPMCloser` we get is not safe
for concurrent use. This is especially noticeable because
`tpm.attestationKey.Clone` uses the same open handle as the original
key. So wrap the operations on ak.tpm with a mutex and make a deep copy
with a new connection in Clone.
Updates #15830
Updates #17662
Updates #17644
Signed-off-by: Andrew Lytvynov <awly@tailscale.com>
Extend Persist with AttestationKey to record a hardware-backed
attestation key for the node's identity.
Add a flag to tailscaled to allow users to control the use of
hardware-backed keys to bind node identity to individual machines.
Updates tailscale/corp#31269
Change-Id: Idcf40d730a448d85f07f1bebf387f086d4c58be3
Signed-off-by: Patrick O'Doherty <patrick@tailscale.com>
We will need this for unmarshaling node prefs: use the zero
HardwareAttestationKey implementation when parsing and later check
`IsZero` to see if anything was loaded.
Updates #15830
Signed-off-by: Andrew Lytvynov <awly@tailscale.com>
