We replace the cmd.exe invocation with RtlGetNtVersionNumbers for the first
three fields. On Windows 10+, we query for the fourth field which is available
via the registry.
The fourth field is not really documented anywhere; Firefox has been querying
it successfully since Windows 10 was released, so we can be pretty confident in
its longevity at this point.
Fixes https://github.com/tailscale/tailscale/issues/1478
Signed-off-by: Aaron Klotz <aaron@tailscale.com>
utils/winutil/vss contains just enough COM wrapping to query the Volume Shadow Copy service for snapshots.
WalkSnapshotsForLegacyStateDir is the friendlier interface that adds awareness of our actual use case,
mapping the snapshots and locating our legacy state directory.
Updates #3011
Signed-off-by: Aaron Klotz <aaron@tailscale.com>
Moving this information into a centralized place so that it is accessible to
code in subsequent commits.
Updates #3011
Signed-off-by: Aaron Klotz <aaron@tailscale.com>
This feature wasn't working until I realized that we also need to opt into
the events. MSDN wasn't so generous as to make this easy to deduce.
Updates #2956
Signed-off-by: Aaron Klotz <aaron@tailscale.com>
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
