For the service, all we need to do is handle the `svc.SessionChange` command.
Upon receipt of a `windows.WTS_SESSION_UNLOCK` event, we fire off a goroutine to flush the DNS cache.
(Windows expects responses to service requests to be quick, so we don't want to do that synchronously.)
This is gated on an integral registry value named `FlushDNSOnSessionUnlock`,
whose value we obtain during service initialization.
(See [this link](https://docs.microsoft.com/en-us/windows/win32/api/winsvc/nc-winsvc-lphandler_function_ex) for information re: handling `SERVICE_CONTROL_SESSIONCHANGE`.)
Fixes#2956
Signed-off-by: Aaron Klotz <aaron@tailscale.com>
This helper allows us to retrieve `DWORD` and `QWORD` values from the Tailscale key in the Windows registry.
Signed-off-by: Aaron Klotz <aaron@tailscale.com>
We unconditionally set appropriate perms on the statefile dir.
We look at the basename of the statefile dir, and if it is "tailscale", then
we set perms as appropriate.
Fixes#2925
Updates #2856
Signed-off-by: Aaron Klotz <aaron@tailscale.com>
ProgramData has a permissive ACL. For us to safely store machine-wide
state information, we must set a more restrictive ACL on our state directory.
We set the ACL so that only talescaled's user (ie, LocalSystem) and the
Administrators group may access our directory.
We must include Administrators to ensure that logs continue to be easily
accessible; omitting that group would force users to use special tools to
log in interactively as LocalSystem, which is not ideal.
(Note that the ACL we apply matches the ACL that was used for LocalSystem's
AppData\Local).
There are two cases where we need to reset perms: One is during migration
from the old location to the new. The second case is for clean installations
where we are creating the file store for the first time.
Updates #2856
Signed-off-by: Aaron Klotz <aaron@tailscale.com>
Aaron Klotz
