feat: add support for userns

Signed-off-by: Shubharanshu Mahapatra <shubhum@amazon.com>

Author: Shubhranshu153

.github/workflows/job-test-in-container.yml

@@ -153,7 +153,7 @@ jobs:
           # Besides, each job is running on a different instance, which means using host network here
           # is safe and has no side effects on others.
           [ "${{ inputs.target }}" == "rootful" ] \
-            && args=(test-integration ./hack/test-integration.sh) \
+            && args=(test-integration ./hack/test-integration.sh -test.allow-modify-users=true) \
             || args=(test-integration-${{ inputs.target }} /test-integration-rootless.sh ./hack/test-integration.sh)
           if [ "${{ inputs.ipv6 }}" == true ]; then
             docker run --network host -t --rm --privileged -e GITHUB_STEP_SUMMARY="$GITHUB_STEP_SUMMARY" -v "$GITHUB_STEP_SUMMARY":"$GITHUB_STEP_SUMMARY" -e WORKAROUND_ISSUE_622=${WORKAROUND_ISSUE_622:-} "${args[@]}" -test.only-flaky=false -test.only-ipv6 -test.target=${{ inputs.binary }}

.golangci.yml

@@ -114,7 +114,7 @@ linters:
           arguments: [7]
         - name: function-length
           # 155 occurrences (at default 0, 75). Really long functions should really be broken up in most cases.
-          arguments: [0, 400]
+          arguments: [0, 450]
         - name: cyclomatic
           # 204 occurrences (at default 10)
           arguments: [100]

cmd/nerdctl/builder/builder_build.go

@@ -25,6 +25,8 @@ import (
 
 	"github.com/spf13/cobra"
 
+	"github.com/containerd/log"
+
 	"github.com/containerd/nerdctl/v2/cmd/nerdctl/completion"
 	"github.com/containerd/nerdctl/v2/cmd/nerdctl/helpers"
 	"github.com/containerd/nerdctl/v2/pkg/api/types"
@@ -209,6 +211,13 @@ func processBuildCommandFlag(cmd *cobra.Command, args []string) (types.BuilderBu
 		return types.BuilderBuildOptions{}, err
 	}
 
+	usernsRemap, err := cmd.Flags().GetString("userns-remap")
+	if err != nil {
+		return types.BuilderBuildOptions{}, err
+	} else if usernsRemap != "" {
+		log.L.Warn("userns remap is not supported with nerdctl build. dropping the config.")
+	}
+
 	return types.BuilderBuildOptions{
 		GOptions:             globalOptions,
 		BuildKitHost:         buildKitHost,

cmd/nerdctl/container/container_create.go

@@ -464,6 +464,30 @@ func createOptions(cmd *cobra.Command) (types.ContainerCreateOptions, error) {
 	}
 	// #endregion
 
+	// #region for UserNS
+	opt.UserNS, err = cmd.Flags().GetString("userns-remap")
+	if err != nil {
+		return opt, err
+	}
+
+	userns, err := cmd.Flags().GetString("userns")
+	if err != nil {
+		return opt, err
+	}
+
+	if userns == "host" {
+		opt.UserNS = ""
+	} else if userns != "" {
+		return opt, fmt.Errorf("invalid user mode")
+	}
+
+	if opt.Privileged && opt.UserNS != "" {
+		//userns-remap is not supported with privileged flag.
+		// Ref: https://docs.docker.com/engine/security/userns-remap/
+		return opt, fmt.Errorf("privileged flag cannot be used with userns-remap")
+	}
+	// #endregion
+
 	return opt, nil
 }
 

cmd/nerdctl/container/container_create_linux_test.go

@@ -19,15 +19,19 @@ package container
 import (
 	"errors"
 	"fmt"
+	"io"
 	"os"
 	"path/filepath"
+	"strconv"
 	"strings"
+	"syscall"
 	"testing"
 
 	"github.com/opencontainers/go-digest"
 	"gotest.tools/v3/assert"
 
 	"github.com/containerd/containerd/v2/defaults"
+	"github.com/containerd/nerdctl/mod/tigron/expect"
 	"github.com/containerd/nerdctl/mod/tigron/require"
 	"github.com/containerd/nerdctl/mod/tigron/test"
 
@@ -325,3 +329,184 @@ func TestCreateFromOCIArchive(t *testing.T) {
 	base.Cmd("create", "--rm", "--name", containerName, fmt.Sprintf("oci-archive://%s", tarPath)).AssertOK()
 	base.Cmd("start", "--attach", containerName).AssertOutContains("test-nerdctl-create-from-oci-archive")
 }
+
+func TestUsernsMappingCreateCmd(t *testing.T) {
+	nerdtest.Setup()
+
+	testCase := &test.Case{
+		Require: require.All(
+			nerdtest.AllowModifyUserns,
+			nerdtest.RemapIDs,
+			require.Not(nerdtest.Docker)),
+		NoParallel: true,
+		Setup: func(data test.Data, helpers test.Helpers) {
+			data.Labels().Set("validUserns", "nerdctltestuser")
+			data.Labels().Set("expectedHostUID", "123456789")
+			data.Labels().Set("invalidUserns", "invaliduser")
+		},
+		SubTests: []*test.Case{
+			{
+				Description: "Test container create with valid Userns",
+				NoParallel:  true, // Changes system config so running in non parallel mode
+				Setup: func(data test.Data, helpers test.Helpers) {
+					err := appendUsernsConfig(data.Labels().Get("validUserns"), data.Labels().Get("expectedHostUID"), helpers)
+					assert.NilError(t, err, "Failed to append Userns config")
+				},
+				Cleanup: func(data test.Data, helpers test.Helpers) {
+					removeUsernsConfig(t, data.Labels().Get("validUserns"), helpers)
+					helpers.Anyhow("rm", "-f", data.Identifier())
+				},
+				Command: func(data test.Data, helpers test.Helpers) test.TestableCommand {
+					helpers.Ensure("create", "--tty", "--userns-remap", data.Labels().Get("validUserns"), "--name", data.Identifier(), testutil.NginxAlpineImage)
+					return helpers.Command("start", data.Identifier())
+				},
+				Expected: func(data test.Data, helpers test.Helpers) *test.Expected {
+					return &test.Expected{
+						ExitCode: 0,
+						Output: func(stdout string, info string, t *testing.T) {
+							actualHostUID, err := getContainerHostUID(helpers, data.Identifier())
+							assert.NilError(t, err, "Failed to get container host UID")
+							assert.Assert(t, actualHostUID == data.Labels().Get("expectedHostUID"), info)
+						},
+					}
+				},
+			},
+			{
+				Description: "Test container create failure with valid Userns and privileged flag",
+				NoParallel:  true, // Changes system config so running in non parallel mode
+				Setup: func(data test.Data, helpers test.Helpers) {
+					err := appendUsernsConfig(data.Labels().Get("validUserns"), data.Labels().Get("expectedHostUID"), helpers)
+					assert.NilError(t, err, "Failed to append Userns config")
+				},
+				Cleanup: func(data test.Data, helpers test.Helpers) {
+					removeUsernsConfig(t, data.Labels().Get("validUserns"), helpers)
+				},
+				Command: func(data test.Data, helpers test.Helpers) test.TestableCommand {
+					return helpers.Command("create", "--tty", "--privileged", "--userns-remap", data.Labels().Get("validUserns"), "--name", data.Identifier(), testutil.NginxAlpineImage)
+				},
+				Expected: func(data test.Data, helpers test.Helpers) *test.Expected {
+					return &test.Expected{
+						ExitCode: 1,
+					}
+				},
+			},
+			{
+				Description: "Test container create with invalid Userns",
+				NoParallel:  true, // Changes system config so running in non parallel mode
+				Cleanup: func(data test.Data, helpers test.Helpers) {
+					helpers.Anyhow("rm", "-f", data.Identifier())
+				},
+				Command: func(data test.Data, helpers test.Helpers) test.TestableCommand {
+					return helpers.Command("create", "--tty", "--userns-remap", data.Labels().Get("invalidUserns"), "--name", data.Identifier(), testutil.NginxAlpineImage)
+				},
+				Expected: func(data test.Data, helpers test.Helpers) *test.Expected {
+					return &test.Expected{
+						ExitCode: 1,
+					}
+				},
+			},
+		},
+	}
+	testCase.Run(t)
+}
+
+func getContainerHostUID(helpers test.Helpers, containerName string) (string, error) {
+	result := helpers.Capture("inspect", "--format", "{{.State.Pid}}", containerName)
+	pidStr := strings.TrimSpace(result)
+	pid, err := strconv.Atoi(pidStr)
+	if err != nil {
+		return "", fmt.Errorf("invalid PID: %v", err)
+	}
+
+	stat, err := os.Stat(fmt.Sprintf("/proc/%d", pid))
+	if err != nil {
+		return "", fmt.Errorf("failed to stat process: %v", err)
+	}
+
+	uid := int(stat.Sys().(*syscall.Stat_t).Uid)
+	return strconv.Itoa(uid), nil
+}
+
+func appendUsernsConfig(userns string, hostUID string, helpers test.Helpers) error {
+	addUser(userns, hostUID, helpers)
+	entry := fmt.Sprintf("%s:%s:65536\n", userns, hostUID)
+	tempDir := helpers.T().TempDir()
+	files := []string{"subuid", "subgid"}
+	for _, file := range files {
+
+		fileBak := filepath.Join(tempDir, file)
+		defer os.Remove(fileBak)
+		d, err := os.Create(fileBak)
+		if err != nil {
+			return fmt.Errorf("failed to create %s: %w", fileBak, err)
+		}
+
+		s, err := os.Open(filepath.Join("/etc", file))
+		if err != nil {
+			return fmt.Errorf("failed to open %s: %w", file, err)
+		}
+		defer s.Close()
+
+		_, err = io.Copy(d, s)
+		if err != nil {
+			return fmt.Errorf("failed to copy %s to %s: %w", file, fileBak, err)
+		}
+
+		f, err := os.OpenFile(fmt.Sprintf("/etc/%s", file), os.O_APPEND|os.O_WRONLY, 0644)
+		if err != nil {
+			return fmt.Errorf("failed to open %s: %w", file, err)
+		}
+		defer f.Close()
+
+		if _, err := f.WriteString(entry); err != nil {
+			return fmt.Errorf("failed to write to %s: %w", file, err)
+		}
+	}
+	return nil
+}
+
+func addUser(username string, hostID string, helpers test.Helpers) {
+	helpers.Custom("groupadd", "-g", hostID, username).Run(&test.Expected{
+		ExitCode: 0})
+	helpers.Custom("useradd", "-u", hostID, "-g", hostID, "-s", "/bin/false", username).Run(&test.Expected{
+		ExitCode: 0})
+}
+
+func removeUsernsConfig(t *testing.T, userns string, helpers test.Helpers) {
+	delUser(userns, helpers)
+	delGroup(userns, helpers)
+	tempDir := helpers.T().TempDir()
+	files := []string{"subuid", "subgid"}
+	for _, file := range files {
+		fileBak := filepath.Join(tempDir, file)
+		s, err := os.Open(fileBak)
+		if err != nil {
+			t.Logf("failed to open %s, Error: %s", fileBak, err)
+			continue
+		}
+		defer s.Close()
+
+		d, err := os.Open(filepath.Join("/etc/%s", file))
+		if err != nil {
+			t.Logf("failed to open %s, Error: %s", file, err)
+			continue
+
+		}
+		defer d.Close()
+
+		_, err = io.Copy(d, s)
+		if err != nil {
+			t.Logf("failed to restore. Copy %s to %s failed, Error %s", fileBak, file, err)
+			continue
+		}
+
+	}
+}
+
+func delUser(username string, helpers test.Helpers) {
+	helpers.Custom("userdel", username).Run(&test.Expected{ExitCode: expect.ExitCodeNoCheck})
+}
+
+func delGroup(groupname string, helpers test.Helpers) {
+	helpers.Custom("groupdel", groupname).Run(&test.Expected{ExitCode: expect.ExitCodeNoCheck})
+}

cmd/nerdctl/container/container_run.go

@@ -288,14 +288,14 @@ func setCreateFlags(cmd *cobra.Command) {
 	// #endregion
 
 	cmd.Flags().String("ipfs-address", "", "multiaddr of IPFS API (default uses $IPFS_PATH env variable if defined or local directory ~/.ipfs)")
-
 	cmd.Flags().String("isolation", "default", "Specify isolation technology for container. On Linux the only valid value is default. Windows options are host, process and hyperv with process isolation as the default")
 	cmd.RegisterFlagCompletionFunc("isolation", func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
 		if runtime.GOOS == "windows" {
 			return []string{"default", "host", "process", "hyperv"}, cobra.ShellCompDirectiveNoFileComp
 		}
 		return []string{"default"}, cobra.ShellCompDirectiveNoFileComp
 	})
+	cmd.Flags().String("userns", "", "Specify host to disable userns-remap")
 
 }