SELinux: per-command whitelisting of ioctls

SELinux: per-command whitelisting of ioctls

Extend the generic ioctl permission check with support for per-command
filtering. Source/target/class sets including the ioctl permission may
additionally include a set of commands. Example:

allow <source> <target>:<class> { 0x8910-0x8926 0x892A-0x8935 }
auditallow <source> <target>:<class> 0x892A

When ioctl commands are omitted only the permissions are checked. This
feature is intended to provide finer granularity for the ioctl
permission which may be too imprecise in some circumstances. For
example, the same driver may use ioctls to provide important and
benign functionality such as driver version or socket type as well as
dangerous capabilities such as debugging features, read/write/execute
to physical memory or access to sensitive data. Per-command filtering
provides a mechanism to reduce the attack surface of the kernel, and
limit applications to the subset of commands required.

The format of the policy binary has been modified to include ioctl
commands, and the policy version number has been incremented to
POLICYDB_VERSION_IOCTL_OPERATIONS=30 to account for the format change.

Bug: 18087110
Change-Id: Ibf0e36728f6f3f0d5af56ccdeddee40800af689d
Signed-off-by: Jeff Vander Stoep <jeffv@google.com>