Historically, the syscall was controlled by a system-wide
perf_event_paranoid sysctl, which is not flexible enough to allow only
specific processes to use the syscall. However, SELinux support for the
syscall has been upstreamed recently[1] (and is being backported to
Android R release common kernels).
[1] da97e18458
As the presence of these hooks is not guaranteed on all Android R
platforms (since we support upgrades while keeping an older kernel), we
need to test for the feature dynamically. The LSM hooks themselves have
no way of being detected directly, so we instead test for their effects,
so we perform several syscalls, and look for a specific success/failure
combination, corresponding to the platform's SELinux policy.
If hooks are detected, perf_event_paranoid is set to -1 (unrestricted),
as the SELinux policy is then sufficient to control access.
This is done within init for several reasons:
* CAP_SYS_ADMIN side-steps perf_event_paranoid, so the tests can be done
if non-root users aren't allowed to use the syscall (the default).
* init is already the setter of the paranoid value (see init.rc), which
is also a privileged operation.
* the test itself is simple (couple of syscalls), so having a dedicated
test binary/domain felt excessive.
I decided to go through a new sysprop (set by a builtin test in
second-stage init), and keeping the actuation in init.rc. We can change
it to an immediate write to the paranoid value if a use-case comes up
that requires the decision to be made earlier in the init sequence.
Bug: 137092007
Change-Id: Ib13a31fee896f17a28910d993df57168a83a4b3d
Now that Result<T> is actually expected<T, ...>, and the expected
proposal states expected<void, ...> as the way to indicate an expected
object that returns either successfully with no object or an error,
let's move init's Result<Success> to the preferred Result<void>.
Bug: 132145659
Test: boot, init unit tests
Change-Id: Ib2f98396d8e6e274f95a496fcdfd8341f77585ee
One of the major aspects of treble is the compartmentalization of system
and vendor components, however init leaves a huge gap here, as vendor
init scripts run in the same context as system init scripts and thus can
access and modify the same properties, files, etc as the system can.
This change is meant to close that gap. It forks a separate 'subcontext'
init that runs in a different SELinux context with permissions that match
what vendors should have access to. Commands get sent over a socket to
this 'subcontext' init that then runs them in this SELinux context and
returns the result.
Note that not all commands run in the subcontext; some commands such as
those dealing with services only make sense in the context of the main
init process.
Bug: 62875318
Test: init unit tests, boot bullhead, boot sailfish
Change-Id: Idf4a4ebf98842d27b8627f901f961ab9eb412aee
We currently throw out the return values from builtin functions and
occasionally log errors with no supporting context. This change uses
the newly introduced Result<T> class to communicate a successful result
or an error back to callers in order to print an error with clear
context when a builtin fails.
Example:
init: Command 'write /sys/class/leds/vibrator/trigger transient' action=init (/init.rc:245) took 0ms and failed: Unable to write to file '/sys/class/leds/vibrator/trigger': open() failed: No such file or directory
Test: boot bullhead
Merged-In: Idc18f331d2d646629c6093c1e0f2996cf9b42aec
Change-Id: Idc18f331d2d646629c6093c1e0f2996cf9b42aec
This change splits out the selinux initialization and supporting
functionality into selinux.cpp and splits the security related
initialization of the rng, etc to security.cpp. It also provides
additional documentation for SEPolicy loading as this has been
requested by some teams.
It additionally cleans up sehandle and sehandle_prop. The former is
static within selinux.cpp and new wrapper functions are created around
selabel_lookup*() to better serve the users. The latter is moved to
property_service.cpp as it is isolated to that file for its usage.
Test: boot bullhead
Merged-In: Idc95d493cebc681fbe686b5160502f36af149f60
Change-Id: Idc95d493cebc681fbe686b5160502f36af149f60
