this feature gate was meant to be ephemeral, and only was used for guaranteeing a
cluster admin didn't accidentally relax PSA policies before the kubelet would deny a pod
was created if it didn't support user namespaces. As of kube 1.33, the supported apiserver version
skew of n-3 guarantees that all supported kubelets are of 1.30 or later, meaning they do this.
Now, we can unconditionally relax PSA policy if a pod is in a user namespace.
This PR reserves older policies default behavior by never relaxing
Signed-off-by: Peter Hunt <pehunt@redhat.com>
The core functionality was enabled by default in 1.34 without any issues that
would have suggested turning it off, so now we can lock it to on-by-default.
Tests which cover disabling the feature must use version emulation.
This reverts commit 2e756e7412,
which addressed the data race only for test/integration/apiserver/oidc.
It also occurs for test/integration/controlplane/transformation:
WARNING: DATA RACE
Read at 0x000008b9de38 by goroutine 104616:
k8s.io/kubernetes/plugin/pkg/admission/defaulttolerationseconds.RegisterFlags()
/home/prow/go/src/k8s.io/kubernetes/plugin/pkg/admission/defaulttolerationseconds/admission.go:42 +0x30
k8s.io/kubernetes/pkg/kubeapiserver/options.registerAllAdmissionPluginFlags()
/home/prow/go/src/k8s.io/kubernetes/pkg/kubeapiserver/options/plugins.go:115 +0x64
k8s.io/kubernetes/pkg/kubeapiserver/options.(*AdmissionOptions).AddFlags()
/home/prow/go/src/k8s.io/kubernetes/pkg/kubeapiserver/options/admission.go:73 +0x55
k8s.io/kubernetes/pkg/controlplane/apiserver/options.(*Options).AddFlags()
/home/prow/go/src/k8s.io/kubernetes/pkg/controlplane/apiserver/options/options.go:154 +0x388
k8s.io/kubernetes/cmd/kube-apiserver/app/options.(*ServerRunOptions).Flags()
/home/prow/go/src/k8s.io/kubernetes/cmd/kube-apiserver/app/options/options.go:101 +0x73
k8s.io/kubernetes/cmd/kube-apiserver/app/testing.StartTestServer()
/home/prow/go/src/k8s.io/kubernetes/cmd/kube-apiserver/app/testing/testserver.go:219 +0xb77
k8s.io/kubernetes/test/integration/controlplane/transformation.newTransformTest()
/home/prow/go/src/k8s.io/kubernetes/test/integration/controlplane/transformation/transformation_test.go:131 +0x6d0
k8s.io/kubernetes/test/integration/controlplane/transformation.TestKMSv2Healthz()
/home/prow/go/src/k8s.io/kubernetes/test/integration/controlplane/transformation/kmsv2_transformation_test.go:874 +0x1c8
testing.tRunner()
/usr/local/go/src/testing/testing.go:1792 +0x225
testing.(*T).Run.gowrap1()
/usr/local/go/src/testing/testing.go:1851 +0x44
Previous write at 0x000008b9de38 by goroutine 111926:
github.com/spf13/pflag.newInt64Value()
/home/prow/go/src/k8s.io/kubernetes/vendor/github.com/spf13/pflag/int64.go:9 +0x49
github.com/spf13/pflag.(*FlagSet).Int64Var()
/home/prow/go/src/k8s.io/kubernetes/vendor/github.com/spf13/pflag/int64.go:41 +0x3d
k8s.io/kubernetes/plugin/pkg/admission/defaulttolerationseconds.RegisterFlags()
/home/prow/go/src/k8s.io/kubernetes/plugin/pkg/admission/defaulttolerationseconds/admission.go:42 +0x25
k8s.io/kubernetes/pkg/kubeapiserver/options.registerAllAdmissionPluginFlags()
/home/prow/go/src/k8s.io/kubernetes/pkg/kubeapiserver/options/plugins.go:115 +0x64
k8s.io/kubernetes/pkg/kubeapiserver/options.(*AdmissionOptions).AddFlags()
/home/prow/go/src/k8s.io/kubernetes/pkg/kubeapiserver/options/admission.go:73 +0x55
k8s.io/kubernetes/pkg/controlplane/apiserver/options.(*Options).AddFlags()
/home/prow/go/src/k8s.io/kubernetes/pkg/controlplane/apiserver/options/options.go:154 +0x388
k8s.io/kubernetes/cmd/kube-apiserver/app/options.(*ServerRunOptions).Flags()
/home/prow/go/src/k8s.io/kubernetes/cmd/kube-apiserver/app/options/options.go:101 +0x73
k8s.io/kubernetes/cmd/kube-apiserver/app/testing.StartTestServer()
/home/prow/go/src/k8s.io/kubernetes/cmd/kube-apiserver/app/testing/testserver.go:219 +0xb77
k8s.io/kubernetes/test/integration/controlplane/transformation.newTransformTest()
/home/prow/go/src/k8s.io/kubernetes/test/integration/controlplane/transformation/transformation_test.go:131 +0x6d0
k8s.io/kubernetes/test/integration/controlplane/transformation.TestKMSv2FeatureFlag()
/home/prow/go/src/k8s.io/kubernetes/test/integration/controlplane/transformation/kmsv2_transformation_test.go:1009 +0x117
testing.tRunner()
/usr/local/go/src/testing/testing.go:1792 +0x225
testing.(*T).Run.gowrap1()
/usr/local/go/src/testing/testing.go:1851 +0x44
A more general solution is to lock while registering the variables (= write)
and while reading the variables once in InspectFeatureGates.
If someone gains the ability to create static pods, they might try to use that
ability to run code which gets access to the resources associated with some
existing claim which was previously allocated for some other pod. Such an
attempt already fails because the claim status tracks which pods are allowed to
use the claim, the static pod is not in that list, the node is not authorized
to add it, and the kubelet checks that list before starting the pod in
195803cde5/pkg/kubelet/cm/dra/manager.go (L218-L222).
Even if the pod were started, DRA drivers typically manage node-local resources
which can already be accessed via such an attack without involving DRA. DRA
drivers which manage non-node-local resources have to consider access by a
compromised node as part of their threat model.
Nonetheless, it is better to not accept static pods which reference
ResourceClaims or ResourceClaimTemplates in the first place because there
is no valid use case for it.
This is done at different levels for defense in depth:
- configuration validation in the kubelet
- admission checking of node restrictions
- API validation
Co-authored-by: Jordan Liggitt <liggitt@google.com>
Code changes by Jordan, with one small change (resourceClaims -> resourceclaims).
Unit tests by Patrick.
The "// import <path>" comment has been superseded by Go modules.
We don't have to remove them, but doing so has some advantages:
- They are used inconsistently, which is confusing.
- We can then also remove the (currently broken) hack/update-vanity-imports.sh.
- Last but not least, it would be a first step towards avoiding the k8s.io domain.
This commit was generated with
sed -i -e 's;^package \(.*\) // import.*;package \1;' $(git grep -l '^package.*// import' | grep -v 'vendor/')
Everything was included, except for
package labels // import k8s.io/kubernetes/pkg/util/labels
because that package is marked as "read-only".
