In v1.78, we started acquiring the GP lock when reading policy settings. This led to a deadlock during
Tailscale installation via Group Policy Software Installation because the GP engine holds the write lock
for the duration of policy processing, which in turn waits for the installation to complete, which in turn
waits for the service to enter the running state.
In this PR, we prevent the acquisition of GP locks (aka EnterCriticalPolicySection) during service startup
and update the Windows Registry-based util/syspolicy/source.PlatformPolicyStore to handle this failure
gracefully. The GP lock is somewhat optional; it’s safe to read policy settings without it, but acquiring
the lock is recommended when reading multiple values to prevent the Group Policy engine from modifying
settings mid-read and to avoid inconsistent results.
Fixes#14416
Signed-off-by: Nick Khyl <nickk@tailscale.com>
In this PR, we implement (but do not use yet, pending #13727 review) a syspolicy/source.Store
that reads policy settings from environment variables. It converts a CamelCase setting.Key,
such as AuthKey or ExitNodeID, to a SCREAMING_SNAKE_CASE, TS_-prefixed environment
variable name, such as TS_AUTH_KEY and TS_EXIT_NODE_ID. It then looks up the variable
and attempts to parse it according to the expected value type. If the environment variable
is not set, the policy setting is considered not configured in this store (the syspolicy package
will still read it from other sources). Similarly, if the environment variable has an invalid value
for the setting type, it won't be used (though the reported/logged error will differ).
Updates #13193
Updates #12687
Signed-off-by: Nick Khyl <nickk@tailscale.com>
We add package defining interfaces for policy stores, enabling creation of policy sources
and reading settings from them. It includes a Windows-specific PlatformPolicyStore for GP and MDM
policies stored in the Registry, and an in-memory TestStore for testing purposes.
We also include an internal package that tracks and reports policy usage metrics when a policy setting
is read from a store. Initially, it will be used only on Windows and Android, as macOS, iOS, and tvOS
report their own metrics. However, we plan to use it across all platforms eventually.
Updates #12687
Signed-off-by: Nick Khyl <nickk@tailscale.com>
Nick Khyl