Revert "control/controlclient: back out HW key attestation (#17664)" (#17732)

This reverts commit a760cbe33f.

Signed-off-by: Andrew Lytvynov <awly@tailscale.com>

ipn/ipnlocal/profiles.go

@@ -19,7 +19,9 @@ import (
 	"tailscale.com/ipn"
 	"tailscale.com/ipn/ipnext"
 	"tailscale.com/tailcfg"
+	"tailscale.com/types/key"
 	"tailscale.com/types/logger"
+	"tailscale.com/types/persist"
 	"tailscale.com/util/clientmetric"
 	"tailscale.com/util/eventbus"
 )
@@ -654,6 +656,14 @@ func (pm *profileManager) loadSavedPrefs(k ipn.StateKey) (ipn.PrefsView, error)
 		return ipn.PrefsView{}, err
 	}
 	savedPrefs := ipn.NewPrefs()
+
+	// if supported by the platform, create an empty hardware attestation key to use when deserializing
+	// to avoid type exceptions from json.Unmarshaling into an interface{}.
+	hw, _ := key.NewEmptyHardwareAttestationKey()
+	savedPrefs.Persist = &persist.Persist{
+		AttestationKey: hw,
+	}
+
 	if err := ipn.PrefsFromBytes(bs, savedPrefs); err != nil {
 		return ipn.PrefsView{}, fmt.Errorf("parsing saved prefs: %v", err)
 	}