PodSecurity: check: addCapabilities

This commit is contained in:
Jordan Liggitt 2021-06-27 04:01:09 -04:00
parent 3733e209c9
commit 93c6f8969a
2 changed files with 198 additions and 0 deletions

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/*
Copyright 2021 The Kubernetes Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package policy
import (
"fmt"
corev1 "k8s.io/api/core/v1"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apimachinery/pkg/util/sets"
"k8s.io/apimachinery/pkg/util/validation/field"
"k8s.io/pod-security-admission/api"
)
func init() {
addCheck(CheckAddCapabilities)
}
// CheckAddCapabilities returns a baseline level check
// that limits the capabilities that can be added in 1.0+
func CheckAddCapabilities() Check {
return Check{
ID: "addCapabilities",
Level: api.LevelBaseline,
Versions: []VersionedCheck{
{
MinimumVersion: api.MajorMinorVersion(1, 0),
CheckPod: addCapabilities_1_0,
},
},
}
}
var (
capabilities_allowed_1_0 = sets.NewString(
"AUDIT_WRITE",
"CHOWN",
"DAC_OVERRIDE",
"FOWNER",
"FSETID",
"KILL",
"MKNOD",
"NET_BIND_SERVICE",
"SETFCAP",
"SETGID",
"SETPCAP",
"SETUID",
"SYS_CHROOT",
)
)
func addCapabilities_1_0(podMetadata *metav1.ObjectMeta, podSpec *corev1.PodSpec) CheckResult {
forbiddenContainers := sets.NewString()
forbiddenCapabilities := sets.NewString()
visitContainersWithPath(podSpec, field.NewPath("spec"), func(container *corev1.Container, path *field.Path) {
if container.SecurityContext != nil && container.SecurityContext.Capabilities != nil {
for _, c := range container.SecurityContext.Capabilities.Add {
if !capabilities_allowed_1_0.Has(string(c)) {
forbiddenContainers.Insert(container.Name)
forbiddenCapabilities.Insert(string(c))
}
}
}
})
if len(forbiddenCapabilities) > 0 {
return CheckResult{
Allowed: false,
ForbiddenReason: "forbidden capabilities",
ForbiddenDetail: fmt.Sprintf(
"containers %q added %q",
forbiddenContainers.List(),
forbiddenCapabilities.List(),
),
}
}
return CheckResult{Allowed: true}
}

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/*
Copyright 2021 The Kubernetes Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package test
import (
corev1 "k8s.io/api/core/v1"
"k8s.io/pod-security-admission/api"
)
/*
TODO: include field paths in reflect-based unit test
containerFields: []string{
`securityContext.capabilities.add`,
},
*/
// ensureCapabilities ensures the pod and all initContainers and containers have a non-nil capabilities.
func ensureCapabilities(p *corev1.Pod) *corev1.Pod {
p = ensureSecurityContext(p)
for i := range p.Spec.Containers {
if p.Spec.Containers[i].SecurityContext.Capabilities == nil {
p.Spec.Containers[i].SecurityContext.Capabilities = &corev1.Capabilities{}
}
}
for i := range p.Spec.InitContainers {
if p.Spec.InitContainers[i].SecurityContext.Capabilities == nil {
p.Spec.InitContainers[i].SecurityContext.Capabilities = &corev1.Capabilities{}
}
}
return p
}
func init() {
fixtureData_1_0 := fixtureGenerator{
expectErrorSubstring: "forbidden capabilities",
generatePass: func(p *corev1.Pod) []*corev1.Pod {
p = ensureCapabilities(p)
return []*corev1.Pod{
// all allowed capabilities
tweak(p, func(p *corev1.Pod) {
p.Spec.Containers[0].SecurityContext.Capabilities.Add = []corev1.Capability{
"AUDIT_WRITE", "CHOWN", "DAC_OVERRIDE", "FOWNER", "FSETID", "KILL", "MKNOD", "NET_BIND_SERVICE", "SETFCAP", "SETGID", "SETPCAP", "SETUID", "SYS_CHROOT",
}
}),
tweak(p, func(p *corev1.Pod) {
p.Spec.InitContainers[0].SecurityContext.Capabilities.Add = []corev1.Capability{
"AUDIT_WRITE", "CHOWN", "DAC_OVERRIDE", "FOWNER", "FSETID", "KILL", "MKNOD", "NET_BIND_SERVICE", "SETFCAP", "SETGID", "SETPCAP", "SETUID", "SYS_CHROOT",
}
}),
}
},
generateFail: func(p *corev1.Pod) []*corev1.Pod {
p = ensureCapabilities(p)
return []*corev1.Pod{
// NET_RAW
tweak(p, func(p *corev1.Pod) {
p.Spec.Containers[0].SecurityContext.Capabilities.Add = []corev1.Capability{"NET_RAW"}
}),
tweak(p, func(p *corev1.Pod) {
p.Spec.InitContainers[0].SecurityContext.Capabilities.Add = []corev1.Capability{"NET_RAW"}
}),
// case-difference
tweak(p, func(p *corev1.Pod) {
p.Spec.Containers[0].SecurityContext.Capabilities.Add = []corev1.Capability{"chown"}
}),
tweak(p, func(p *corev1.Pod) {
p.Spec.InitContainers[0].SecurityContext.Capabilities.Add = []corev1.Capability{"chown"}
}),
// unknown capability
tweak(p, func(p *corev1.Pod) {
p.Spec.Containers[0].SecurityContext.Capabilities.Add = []corev1.Capability{"bogus"}
}),
tweak(p, func(p *corev1.Pod) {
p.Spec.InitContainers[0].SecurityContext.Capabilities.Add = []corev1.Capability{"bogus"}
}),
// CAP_ prefix
tweak(p, func(p *corev1.Pod) {
p.Spec.Containers[0].SecurityContext.Capabilities.Add = []corev1.Capability{"CAP_CHOWN"}
}),
tweak(p, func(p *corev1.Pod) {
p.Spec.InitContainers[0].SecurityContext.Capabilities.Add = []corev1.Capability{"CAP_CHOWN"}
}),
}
},
}
registerFixtureGenerator(
fixtureKey{level: api.LevelBaseline, version: api.MajorMinorVersion(1, 0), check: "addCapabilities"},
fixtureData_1_0,
)
}