docs: add docs on usernamespace support in k8s

Add docs and test for usernamespaces support in Kubernetes.

Fixes: #8554

Signed-off-by: Noel Georgi <git@frezbo.dev>

.github/workflows/ci.yaml

@@ -1,6 +1,6 @@
 # THIS FILE WAS AUTOMATICALLY GENERATED, PLEASE DO NOT EDIT.
 #
-# Generated on 2024-10-23T17:20:56Z by kres 6d3cad4.
+# Generated on 2024-11-07T15:01:48Z by kres 1fc767a.
 
 name: default
 concurrency:
@@ -2407,6 +2407,13 @@ jobs:
           WITH_APPARMOR_LSM_ENABLED: "yes"
         run: |
           sudo -E make e2e-qemu
+      - name: e2e-k8s-user-namespace
+        env:
+          IMAGE_REGISTRY: registry.dev.siderolabs.io
+          SHORT_INTEGRATION_TEST: "yes"
+          WITH_CONFIG_PATCH: '@hack/test/patches/usernamespace.yaml'
+        run: |
+          sudo -E make e2e-qemu
       - name: save artifacts
         if: always()
         uses: actions/upload-artifact@v4

.github/workflows/integration-misc-4-cron.yaml

@@ -1,6 +1,6 @@
 # THIS FILE WAS AUTOMATICALLY GENERATED, PLEASE DO NOT EDIT.
 #
-# Generated on 2024-09-12T16:43:46Z by kres 8be5fa7.
+# Generated on 2024-11-07T15:01:48Z by kres 1fc767a.
 
 name: integration-misc-4-cron
 concurrency:
@@ -109,6 +109,13 @@ jobs:
           WITH_APPARMOR_LSM_ENABLED: "yes"
         run: |
           sudo -E make e2e-qemu
+      - name: e2e-k8s-user-namespace
+        env:
+          IMAGE_REGISTRY: registry.dev.siderolabs.io
+          SHORT_INTEGRATION_TEST: "yes"
+          WITH_CONFIG_PATCH: '@hack/test/patches/usernamespace.yaml'
+        run: |
+          sudo -E make e2e-qemu
       - name: save artifacts
         if: always()
         uses: actions/upload-artifact@v4

.kres.yaml

@@ -953,6 +953,13 @@ spec:
             SHORT_INTEGRATION_TEST: yes
             WITH_APPARMOR_LSM_ENABLED: yes
             IMAGE_REGISTRY: registry.dev.siderolabs.io
+        - name: e2e-k8s-user-namespace
+          command: e2e-qemu
+          withSudo: true
+          environment:
+            SHORT_INTEGRATION_TEST: yes
+            WITH_CONFIG_PATCH: "@hack/test/patches/usernamespace.yaml"
+            IMAGE_REGISTRY: registry.dev.siderolabs.io
         - name: save-talos-logs
           conditions:
             - always

hack/release.toml

@@ -25,6 +25,13 @@ Kubernetes: 1.32.0-beta.0
 runc: 1.2.1
 
 Talos is built with Go 1.23.2.
+"""
+
+    [notes.usernamespaces]
+        title = "User Namespaces"
+        description = """\
+Talos Linux now supports running Kubernetes pods with user namespaces enabled.
+Refer to the [documentation](https://www.talos.dev/v1.9/kubernetes-guides/configuration/usernamespace/) for more information.
 """
 
     [notes.apparmor]

hack/test/patches/usernamespace.yaml

@@ -0,0 +1,13 @@
+---
+cluster:
+  apiServer:
+    extraArgs:
+      feature-gates: UserNamespacesSupport=true,UserNamespacesPodSecurityStandards=true
+machine:
+  sysctls:
+    user.max_user_namespaces: "11255"
+  kubelet:
+    extraConfig:
+      featureGates:
+        UserNamespacesSupport: true
+        UserNamespacesPodSecurityStandards: true

internal/integration/k8s/testdata/usernamespace.yaml

@@ -0,0 +1,12 @@
+apiVersion: v1
+kind: Pod
+metadata:
+  name: userns
+  namespace: default
+spec:
+  hostUsers: false
+  containers:
+  - name: userns
+    command: ["/bin/sh", "-c", "--"]
+    args: ["trap : TERM INT; (sleep 1000) & wait"]
+    image: alpine

internal/integration/k8s/usernamespace.go

@@ -0,0 +1,128 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+//go:build integration_k8s
+
+package k8s
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	_ "embed"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/siderolabs/talos/internal/integration/base"
+	"github.com/siderolabs/talos/pkg/machinery/client"
+	"github.com/siderolabs/talos/pkg/machinery/config/machine"
+)
+
+// UserNamespaceSuite verifies that a pod with user namespace works.
+type UserNamespaceSuite struct {
+	base.K8sSuite
+}
+
+//go:embed testdata/usernamespace.yaml
+var userNamespacePodSpec []byte
+
+// SuiteName returns the name of the suite.
+func (suite *UserNamespaceSuite) SuiteName() string {
+	return "k8s.UserNamespaceSuite"
+}
+
+// TestUserNamespace verifies that a pod with user namespace works.
+//
+//nolint:gocyclo
+func (suite *UserNamespaceSuite) TestUserNamespace() {
+	if suite.Cluster == nil {
+		suite.T().Skip("without full cluster state reaching out to the node IP is not reliable")
+	}
+
+	if suite.Cluster.Provisioner() != base.ProvisionerQEMU {
+		suite.T().Skip("skipping usernamespace test since provisioner is not qemu")
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Minute)
+	suite.T().Cleanup(cancel)
+
+	node := suite.RandomDiscoveredNodeInternalIP(machine.TypeWorker)
+
+	nodeCtx := client.WithNodes(ctx, node)
+
+	reader, err := suite.Client.Read(nodeCtx, "/proc/sys/user/max_user_namespaces")
+	suite.Require().NoError(err)
+
+	var maxUserNamespaces bytes.Buffer
+
+	_, err = maxUserNamespaces.ReadFrom(reader)
+	suite.Require().NoError(err)
+
+	if strings.TrimSpace(maxUserNamespaces.String()) == "0" {
+		suite.T().Skip("skipping test since user namespace is disabled")
+	}
+
+	usernamespacePodManifest := suite.ParseManifests(userNamespacePodSpec)
+
+	suite.T().Cleanup(func() {
+		cleanUpCtx, cleanupCancel := context.WithTimeout(context.Background(), time.Minute)
+		defer cleanupCancel()
+
+		suite.DeleteManifests(cleanUpCtx, usernamespacePodManifest)
+	})
+
+	suite.ApplyManifests(ctx, usernamespacePodManifest)
+
+	suite.Require().NoError(suite.WaitForPodToBeRunning(ctx, time.Minute, "default", "userns"))
+
+	processResp, err := suite.Client.Processes(nodeCtx)
+	suite.Require().NoError(err)
+
+	var sleepProcessPID int
+
+	for _, processInfo := range processResp.Messages {
+		for _, process := range processInfo.Processes {
+			if strings.Contains(process.Args, "sleep 1000") {
+				sleepProcessPID = int(process.Pid)
+
+				break
+			}
+		}
+	}
+
+	suite.Require().NotZero(sleepProcessPID, "sleep process not found for user namespace test")
+
+	reader, err = suite.Client.Read(nodeCtx, fmt.Sprintf("/proc/%d/status", sleepProcessPID))
+	suite.Require().NoError(err)
+
+	var processStatus bytes.Buffer
+
+	_, err = processStatus.ReadFrom(reader)
+	suite.Require().NoError(err)
+
+	scanner := bufio.NewScanner(&processStatus)
+
+	var processUsingUserNamespace bool
+
+	for scanner.Scan() {
+		line := scanner.Text()
+
+		if strings.HasPrefix(line, "Uid:") {
+			fields := strings.Fields(line)
+
+			if fields[0] != "0" && fields[1] != "0" && fields[2] != "0" && fields[3] != "0" {
+				processUsingUserNamespace = true
+			}
+
+			break
+		}
+	}
+
+	suite.Require().True(processUsingUserNamespace, "sleep process should not have root UID in host namespace\n", processStatus.String())
+}
+
+func init() {
+	allSuites = append(allSuites, new(UserNamespaceSuite))
+}

website/content/v1.9/kubernetes-guides/configuration/usernamespace.md

@@ -0,0 +1,30 @@
+---
+title: "User Namespaces"
+description: "Guide on how to configure Talos Cluster to support User Namespaces"
+---
+
+User Namespaces are a feature of the Linux kernel that allows unprivileged users to have their own range of UIDs and GIDs, without needing to be root.
+
+Refer to the [official documentation](https://kubernetes.io/docs/concepts/workloads/pods/user-namespaces/) for more information on Usernamespaces.
+
+## Enabling Usernamespaces
+
+To enable User Namespaces in Talos, you need to add the following configuration to Talos machine configuration:
+
+```yaml
+---
+cluster:
+  apiServer:
+    extraArgs:
+      feature-gates: UserNamespacesSupport=true,UserNamespacesPodSecurityStandards=true
+machine:
+  sysctls:
+    user.max_user_namespaces: "11255"
+  kubelet:
+    extraConfig:
+      featureGates:
+        UserNamespacesSupport: true
+        UserNamespacesPodSecurityStandards: true
+```
+
+After applying the configuration, refer to the [official documentation](https://kubernetes.io/docs/tasks/configure-pod-container/user-namespaces/) to configure workloads to use User Namespaces.