Add username to /etc/passwd inside of container if --userns keep-id

cmd/podman/common/specgen.go

@@ -241,6 +241,8 @@ func FillOutSpecGen(s *specgen.SpecGenerator, c *ContainerCLIOpts, args []string
 	// If some mappings are specified, assume a private user namespace
 	if userNS.IsDefaultValue() && (!s.IDMappings.HostUIDMapping || !s.IDMappings.HostGIDMapping) {
 		s.UserNS.NSMode = specgen.Private
+	} else {
+		s.UserNS.NSMode = specgen.NamespaceMode(userNS)
 	}
 
 	s.Terminal = c.TTY

libpod/container.go

@@ -278,6 +278,9 @@ type ContainerConfig struct {
 	User string `json:"user,omitempty"`
 	// Additional groups to add
 	Groups []string `json:"groups,omitempty"`
+	// AddCurrentUserPasswdEntry indicates that the current user passwd entry
+	// should be added to the /etc/passwd within the container
+	AddCurrentUserPasswdEntry bool `json:"addCurrentUserPasswdEntry,omitempty"`
 
 	// Namespace Config
 	// IDs of container to share namespaces with
@@ -786,7 +789,10 @@ func (c *Container) Hostname() string {
 
 // WorkingDir returns the containers working dir
 func (c *Container) WorkingDir() string {
-	return c.config.Spec.Process.Cwd
+	if c.config.Spec.Process != nil {
+		return c.config.Spec.Process.Cwd
+	}
+	return "/"
 }
 
 // State Accessors

libpod/container_internal_linux.go

@@ -9,6 +9,7 @@ import (
 	"io/ioutil"
 	"net"
 	"os"
+	"os/user"
 	"path"
 	"path/filepath"
 	"strconv"
@@ -34,7 +35,7 @@ import (
 	"github.com/containers/libpod/v2/utils"
 	"github.com/containers/storage/pkg/archive"
 	securejoin "github.com/cyphar/filepath-securejoin"
-	"github.com/opencontainers/runc/libcontainer/user"
+	User "github.com/opencontainers/runc/libcontainer/user"
 	spec "github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/opencontainers/runtime-tools/generate"
 	"github.com/opencontainers/selinux/go-selinux/label"
@@ -1448,9 +1449,23 @@ func (c *Container) getHosts() string {
 	return hosts
 }
 
-// generatePasswd generates a container specific passwd file,
-// iff g.config.User is a number
-func (c *Container) generatePasswd() (string, error) {
+// generateCurrentUserPasswdEntry generates an /etc/passwd entry for the user
+// running the container engine
+func (c *Container) generateCurrentUserPasswdEntry() (string, error) {
+	uid := rootless.GetRootlessUID()
+	if uid == 0 {
+		return "", nil
+	}
+	u, err := user.LookupId(strconv.Itoa(rootless.GetRootlessUID()))
+	if err != nil {
+		return "", errors.Wrapf(err, "failed to get current user")
+	}
+	return fmt.Sprintf("%s:x:%s:%s:%s:%s:/bin/sh\n", u.Username, u.Uid, u.Gid, u.Username, c.WorkingDir()), nil
+}
+
+// generateUserPasswdEntry generates an /etc/passwd entry for the container user
+// to run in the container.
+func (c *Container) generateUserPasswdEntry() (string, error) {
 	var (
 		groupspec string
 		gid       int
@@ -1468,14 +1483,16 @@ func (c *Container) generatePasswd() (string, error) {
 	if err != nil {
 		return "", nil
 	}
+
 	// Lookup the user to see if it exists in the container image
 	_, err = lookup.GetUser(c.state.Mountpoint, userspec)
-	if err != nil && err != user.ErrNoPasswdEntries {
+	if err != nil && err != User.ErrNoPasswdEntries {
 		return "", err
 	}
 	if err == nil {
 		return "", nil
 	}
+
 	if groupspec != "" {
 		ugid, err := strconv.ParseUint(groupspec, 10, 32)
 		if err == nil {
@@ -1488,14 +1505,39 @@ func (c *Container) generatePasswd() (string, error) {
 			gid = group.Gid
 		}
 	}
+	return fmt.Sprintf("%d:x:%d:%d:container user:%s:/bin/sh\n", uid, uid, gid, c.WorkingDir()), nil
+}
+
+// generatePasswd generates a container specific passwd file,
+// iff g.config.User is a number
+func (c *Container) generatePasswd() (string, error) {
+	if !c.config.AddCurrentUserPasswdEntry && c.config.User == "" {
+		return "", nil
+	}
+	pwd := ""
+	if c.config.User != "" {
+		entry, err := c.generateUserPasswdEntry()
+		if err != nil {
+			return "", err
+		}
+		pwd += entry
+	}
+	if c.config.AddCurrentUserPasswdEntry {
+		entry, err := c.generateCurrentUserPasswdEntry()
+		if err != nil {
+			return "", err
+		}
+		pwd += entry
+	}
+	if pwd == "" {
+		return "", nil
+	}
 	originPasswdFile := filepath.Join(c.state.Mountpoint, "/etc/passwd")
 	orig, err := ioutil.ReadFile(originPasswdFile)
 	if err != nil && !os.IsNotExist(err) {
 		return "", errors.Wrapf(err, "unable to read passwd file %s", originPasswdFile)
 	}
-
-	pwd := fmt.Sprintf("%s%d:x:%d:%d:container user:%s:/bin/sh\n", orig, uid, uid, gid, c.WorkingDir())
-	passwdFile, err := c.writeStringToRundir("passwd", pwd)
+	passwdFile, err := c.writeStringToRundir("passwd", string(orig)+pwd)
 	if err != nil {
 		return "", errors.Wrapf(err, "failed to create temporary passwd file")
 	}

libpod/container_internal_linux_test.go

@@ -0,0 +1,42 @@
+// +build linux
+
+package libpod
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+
+	spec "github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGenerateUserPasswdEntry(t *testing.T) {
+	dir, err := ioutil.TempDir("", "libpod_test_")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(dir)
+
+	c := Container{
+		config: &ContainerConfig{
+			User: "123:456",
+			Spec: &spec.Spec{},
+		},
+		state: &ContainerState{
+			Mountpoint: "/does/not/exist/tmp/",
+		},
+	}
+	user, err := c.generateUserPasswdEntry()
+	if err != nil {
+		t.Fatal(err)
+	}
+	assert.Equal(t, user, "123:x:123:456:container user:/:/bin/sh\n")
+
+	c.config.User = "567"
+	user, err = c.generateUserPasswdEntry()
+	if err != nil {
+		t.Fatal(err)
+	}
+	assert.Equal(t, user, "567:x:567:0:container user:/:/bin/sh\n")
+}

libpod/options.go

@@ -866,6 +866,20 @@ func WithPIDNSFrom(nsCtr *Container) CtrCreateOption {
 	}
 }
 
+// WithAddCurrentUserPasswdEntry indicates that container should add current
+// user entry to /etc/passwd, since the UID will be mapped into the container,
+// via user namespace
+func WithAddCurrentUserPasswdEntry() CtrCreateOption {
+	return func(ctr *Container) error {
+		if ctr.valid {
+			return define.ErrCtrFinalized
+		}
+
+		ctr.config.AddCurrentUserPasswdEntry = true
+		return nil
+	}
+}
+
 // WithUserNSFrom indicates the the container should join the user namespace of
 // the given container.
 // If the container has joined a pod, it can only join the namespaces of

pkg/specgen/generate/namespaces.go

@@ -153,7 +153,9 @@ func namespaceOptions(ctx context.Context, s *specgen.SpecGenerator, rt *libpod.
 	// User
 	switch s.UserNS.NSMode {
 	case specgen.KeepID:
-		if !rootless.IsRootless() {
+		if rootless.IsRootless() {
+			toReturn = append(toReturn, libpod.WithAddCurrentUserPasswdEntry())
+		} else {
 			// keep-id as root doesn't need a user namespace
 			s.UserNS.NSMode = specgen.Host
 		}

test/e2e/run_userns_test.go

@@ -89,6 +89,16 @@ var _ = Describe("Podman UserNS support", func() {
 		Expect(ok).To(BeTrue())
 	})
 
+	It("podman --userns=keep-id check passwd", func() {
+		session := podmanTest.Podman([]string{"run", "--userns=keep-id", "alpine", "id", "-un"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		u, err := user.Current()
+		Expect(err).To(BeNil())
+		ok, _ := session.GrepString(u.Name)
+		Expect(ok).To(BeTrue())
+	})
+
 	It("podman --userns=keep-id root owns /usr", func() {
 		session := podmanTest.Podman([]string{"run", "--userns=keep-id", "alpine", "stat", "-c%u", "/usr"})
 		session.WaitWithDefaultTimeout()