expand SELinux policy #888
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Silences the kernel warning during startup: "Context system_u:object_r:container_file_t:s0 is not valid" Signed-off-by: Ben Cressey <[email protected]>
This extends the initial implementation of the policy with a complete set of all classes and available actions as of the 5.4 kernel. We also include the permissions expected by systemd and dbus-broker. In a few cases, actions that no longer exist in the kernel have been removed, for example the "entrypoint" permission for the "chr_file" class. The more comprehensive policy now denies unknown actions by default, which creates some risk for kernel updates, but also acts as a nudge to revisit the policy periodically. Any newly added classes and actions will be logged by the kernel when the policy is loaded. The 5.4 kernel added support for restricting file watches through inotify(), dnotify(), and fanotify(). Related rules were added as a special case to the policy to prevent processes running in containers from blocking the host's access to its own files. Other uses are still allowed. Since classes related to sockets, networks, and IPCs are now defined in the policy, it also includes rules to permit almost all actions without restriction. The only exceptions are the actions related to SELinux labeling, all of which are reserved for the host OS. Because the policy defines userspace classes and actions, we can now restrict interactions with systemd and dbus-broker to the host OS. These programs are regarded as implementation details and not meant for direct use by processes running in containers. Other management functions, notably including the ability to load and manage the SELinux policy, have also been reserved for the host OS. We now include all relevant capabilities in the policy, to enable the full set of policy features, and to ensure that all defined classes and actions are used. Signed-off-by: Ben Cressey <[email protected]>
tjkirch
approved these changes
Apr 6, 2020
iliana
approved these changes
Apr 8, 2020
jamieand
approved these changes
Apr 9, 2020
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Issue number:
#764
Description of changes:
Expand the SELinux policy to include all classes and actions in the 5.4 kernel, as well as those expected by
systemdanddbus-broker.Also fixes a minor issue with
kubeletusing an unknown label.Testing done:
Verified that the kernel no longer reports missing classes or actions when loading the policy at startup, and that the listed capabilities match the policy.
Built the
aws-devvariant. Ran under KVM. Pulled and started a Docker container. Found no AVC denials.Built the
aws-k8s-1.15variant; registered as an AMI; joined to a cluster. Ransonobuoytests. Launched a pod using an EFS CSI persistent volume claim. Found no AVC denials.Verified that interactions with systemd from a
container_tprocess generated the expected denials.Terms of contribution:
By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.