Merge pull request #2028 from giuseppe/fix-rootless-export

rootless: fix export when using fuse-overlayfs

cmd/podman/export.go

@@ -1,9 +1,13 @@
 package main
 
 import (
+	"io/ioutil"
 	"os"
+	"strconv"
 
 	"github.com/containers/libpod/cmd/podman/libpodruntime"
+	"github.com/containers/libpod/libpod"
+	"github.com/containers/libpod/pkg/rootless"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
 	"github.com/urfave/cli"
@@ -35,6 +39,9 @@ func exportCmd(c *cli.Context) error {
 	if err := validateFlags(c, exportFlags); err != nil {
 		return err
 	}
+	if os.Geteuid() != 0 {
+		rootless.SetSkipStorageSetup(true)
+	}
 
 	runtime, err := libpodruntime.GetRuntime(c)
 	if err != nil {
@@ -66,5 +73,37 @@ func exportCmd(c *cli.Context) error {
 		return errors.Wrapf(err, "error looking up container %q", args[0])
 	}
 
+	if os.Geteuid() != 0 {
+		state, err := ctr.State()
+		if err != nil {
+			return errors.Wrapf(err, "cannot read container state %q", ctr.ID())
+		}
+		if state == libpod.ContainerStateRunning || state == libpod.ContainerStatePaused {
+			data, err := ioutil.ReadFile(ctr.Config().ConmonPidFile)
+			if err != nil {
+				return errors.Wrapf(err, "cannot read conmon PID file %q", ctr.Config().ConmonPidFile)
+			}
+			conmonPid, err := strconv.Atoi(string(data))
+			if err != nil {
+				return errors.Wrapf(err, "cannot parse PID %q", data)
+			}
+			became, ret, err := rootless.JoinDirectUserAndMountNS(uint(conmonPid))
+			if err != nil {
+				return err
+			}
+			if became {
+				os.Exit(ret)
+			}
+		} else {
+			became, ret, err := rootless.BecomeRootInUserNS()
+			if err != nil {
+				return err
+			}
+			if became {
+				os.Exit(ret)
+			}
+		}
+	}
+
 	return ctr.Export(output)
 }

cmd/podman/main.go

@@ -30,6 +30,7 @@ var cmdsNotRequiringRootless = map[string]bool{
 	"version": true,
 	"create":  true,
 	"exec":    true,
+	"export":  true,
 	// `info` must be executed in an user namespace.
 	// If this change, please also update libpod.refreshRootless()
 	"login":   true,

libpod/runtime_ctr.go

@@ -8,6 +8,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/containers/libpod/pkg/rootless"
 	"github.com/containers/storage"
 	"github.com/containers/storage/pkg/stringid"
 	spec "github.com/opencontainers/runtime-spec/specs-go"
@@ -154,6 +155,10 @@ func (r *Runtime) newContainer(ctx context.Context, rSpec *spec.Spec, options ..
 		}
 	}()
 
+	if rootless.IsRootless() && ctr.config.ConmonPidFile == "" {
+		ctr.config.ConmonPidFile = filepath.Join(ctr.state.RunDir, "conmon.pid")
+	}
+
 	// Go through the volume mounts and check for named volumes
 	// If the named volme already exists continue, otherwise create
 	// the storage for the named volume.

pkg/rootless/rootless_linux.c

@@ -99,7 +99,7 @@ get_cmd_line_args (pid_t pid)
 }
 
 int
-reexec_userns_join (int userns)
+reexec_userns_join (int userns, int mountns)
 {
   pid_t ppid = getpid ();
   char uid[16];
@@ -131,6 +131,13 @@ reexec_userns_join (int userns)
     }
   close (userns);
 
+  if (mountns >= 0 && setns (mountns, 0) < 0)
+    {
+      fprintf (stderr, "cannot setns: %s\n", strerror (errno));
+      _exit (EXIT_FAILURE);
+    }
+  close (userns);
+
   if (syscall_setresgid (0, 0, 0) < 0)
     {
       fprintf (stderr, "cannot setresgid: %s\n", strerror (errno));

pkg/rootless/rootless_linux.go

@@ -25,7 +25,7 @@ import (
 /*
 extern int reexec_in_user_namespace(int ready);
 extern int reexec_in_user_namespace_wait(int pid);
-extern int reexec_userns_join(int userns);
+extern int reexec_userns_join(int userns, int mountns);
 */
 import "C"
 
@@ -112,7 +112,40 @@ func JoinNS(pid uint) (bool, int, error) {
 	}
 	defer userNS.Close()
 
-	pidC := C.reexec_userns_join(C.int(userNS.Fd()))
+	pidC := C.reexec_userns_join(C.int(userNS.Fd()), -1)
+	if int(pidC) < 0 {
+		return false, -1, errors.Errorf("cannot re-exec process")
+	}
+
+	ret := C.reexec_in_user_namespace_wait(pidC)
+	if ret < 0 {
+		return false, -1, errors.New("error waiting for the re-exec process")
+	}
+
+	return true, int(ret), nil
+}
+
+// JoinDirectUserAndMountNS re-exec podman in a new userNS and join the user and mount
+// namespace of the specified PID without looking up its parent.  Useful to join directly
+// the conmon process.
+func JoinDirectUserAndMountNS(pid uint) (bool, int, error) {
+	if os.Geteuid() == 0 || os.Getenv("_LIBPOD_USERNS_CONFIGURED") != "" {
+		return false, -1, nil
+	}
+
+	userNS, err := os.Open(fmt.Sprintf("/proc/%d/ns/user", pid))
+	if err != nil {
+		return false, -1, err
+	}
+	defer userNS.Close()
+
+	mountNS, err := os.Open(fmt.Sprintf("/proc/%d/ns/mnt", pid))
+	if err != nil {
+		return false, -1, err
+	}
+	defer userNS.Close()
+
+	pidC := C.reexec_userns_join(C.int(userNS.Fd()), C.int(mountNS.Fd()))
 	if int(pidC) < 0 {
 		return false, -1, errors.Errorf("cannot re-exec process")
 	}
@@ -138,7 +171,7 @@ func JoinNSPath(path string) (bool, int, error) {
 	}
 	defer userNS.Close()
 
-	pidC := C.reexec_userns_join(C.int(userNS.Fd()))
+	pidC := C.reexec_userns_join(C.int(userNS.Fd()), -1)
 	if int(pidC) < 0 {
 		return false, -1, errors.Errorf("cannot re-exec process")
 	}

test/e2e/rootless_test.go

@@ -7,6 +7,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"runtime"
+	"strings"
 	"syscall"
 
 	. "github.com/containers/libpod/test/utils"
@@ -245,6 +246,22 @@ var _ = Describe("Podman rootless", func() {
 			cmd.WaitWithDefaultTimeout()
 			Expect(cmd.ExitCode()).To(Equal(0))
 			Expect(cmd.LineInOutputContains("hello")).To(BeTrue())
+
+			cmd = rootlessTest.PodmanAsUser([]string{"ps", "-l", "-q"}, 1000, 1000, env)
+			cmd.WaitWithDefaultTimeout()
+			Expect(cmd.ExitCode()).To(Equal(0))
+			cid := cmd.OutputToString()
+
+			cmd = rootlessTest.PodmanAsUser([]string{"exec", "-l", "sh", "-c", "echo SeCreTMessage > /file"}, 1000, 1000, env)
+			cmd.WaitWithDefaultTimeout()
+			Expect(cmd.ExitCode()).To(Equal(0))
+
+			path := filepath.Join(home, "export.tar")
+			cmd = rootlessTest.PodmanAsUser([]string{"export", "-o", path, cid}, 1000, 1000, env)
+			cmd.WaitWithDefaultTimeout()
+			content, err := ioutil.ReadFile(path)
+			Expect(err).To(BeNil())
+			Expect(strings.Contains(string(content), "SeCreTMessage")).To(BeTrue())
 		}
 		runInRootlessContext(f)
 	}