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-rw-r--r--runsc/cmd/BUILD1
-rw-r--r--runsc/cmd/boot.go31
-rw-r--r--runsc/cmd/chroot.go95
-rw-r--r--runsc/cmd/cmd.go26
-rw-r--r--runsc/sandbox/BUILD1
-rw-r--r--runsc/sandbox/chroot.go97
-rw-r--r--runsc/sandbox/sandbox.go86
-rw-r--r--runsc/test/root/chroot_test.go16
8 files changed, 201 insertions, 152 deletions
diff --git a/runsc/cmd/BUILD b/runsc/cmd/BUILD
index 394bb0e1f..a908172af 100644
--- a/runsc/cmd/BUILD
+++ b/runsc/cmd/BUILD
@@ -8,6 +8,7 @@ go_library(
"boot.go",
"capability.go",
"checkpoint.go",
+ "chroot.go",
"cmd.go",
"create.go",
"debug.go",
diff --git a/runsc/cmd/boot.go b/runsc/cmd/boot.go
index bb3435284..7ca2744bd 100644
--- a/runsc/cmd/boot.go
+++ b/runsc/cmd/boot.go
@@ -60,6 +60,9 @@ type Boot struct {
// to the process.
applyCaps bool
+ // setUpChroot is set to true if the sandbox is started in an empty root.
+ setUpRoot bool
+
// cpuNum number of CPUs to create inside the sandbox.
cpuNum int
@@ -99,6 +102,7 @@ func (b *Boot) SetFlags(f *flag.FlagSet) {
f.Var(&b.stdioFDs, "stdio-fds", "list of FDs containing sandbox stdin, stdout, and stderr in that order")
f.BoolVar(&b.console, "console", false, "set to true if the sandbox should allow terminal ioctl(2) syscalls")
f.BoolVar(&b.applyCaps, "apply-caps", false, "if true, apply capabilities defined in the spec to the process")
+ f.BoolVar(&b.setUpRoot, "setup-root", false, "if true, set up an empty root for the process")
f.IntVar(&b.cpuNum, "cpu-num", 0, "number of CPUs to create inside the sandbox")
f.Uint64Var(&b.totalMem, "total-memory", 0, "sets the initial amount of total memory to report back to the container")
f.IntVar(&b.userLogFD, "user-log-fd", 0, "file descriptor to write user logs to. 0 means no logging.")
@@ -116,6 +120,31 @@ func (b *Boot) Execute(_ context.Context, f *flag.FlagSet, args ...interface{})
// Ensure that if there is a panic, all goroutine stacks are printed.
debug.SetTraceback("all")
+ if b.setUpRoot {
+ if err := setUpChroot(); err != nil {
+ Fatalf("error setting up chroot: %v", err)
+ }
+
+ specutils.ExePath = "/runsc"
+ if !b.applyCaps {
+ // Remove --setup-root arg to call myself.
+ var args []string
+ for _, arg := range os.Args {
+ if !strings.Contains(arg, "setup-root") {
+ args = append(args, arg)
+ }
+ }
+ // Note that we've already read the spec from the spec FD, and
+ // we will read it again after the exec call. This works
+ // because the ReadSpecFromFile function seeks to the beginning
+ // of the file before reading.
+ if err := callSelfAsNobody(args); err != nil {
+ Fatalf("%v", err)
+ }
+ panic("callSelfAsNobody must never return success")
+ }
+ }
+
// Get the spec from the specFD.
specFile := os.NewFile(uintptr(b.specFD), "spec file")
defer specFile.Close()
@@ -144,7 +173,7 @@ func (b *Boot) Execute(_ context.Context, f *flag.FlagSet, args ...interface{})
// Remove --apply-caps arg to call myself.
var args []string
for _, arg := range os.Args {
- if !strings.Contains(arg, "apply-caps") {
+ if !strings.Contains(arg, "setup-root") && !strings.Contains(arg, "apply-caps") {
args = append(args, arg)
}
}
diff --git a/runsc/cmd/chroot.go b/runsc/cmd/chroot.go
new file mode 100644
index 000000000..b53085934
--- /dev/null
+++ b/runsc/cmd/chroot.go
@@ -0,0 +1,95 @@
+// Copyright 2019 Google LLC
+//
+// 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 cmd
+
+import (
+ "fmt"
+ "os"
+ "path/filepath"
+ "syscall"
+
+ "gvisor.googlesource.com/gvisor/pkg/log"
+ "gvisor.googlesource.com/gvisor/runsc/specutils"
+)
+
+// chrootBinPath is the location inside the chroot where the runsc binary will
+// be mounted.
+const chrootBinPath = "/runsc"
+
+// mountInChroot creates the destination mount point in the given chroot and
+// mounts the source.
+func mountInChroot(chroot, src, dst, typ string, flags uint32) error {
+ chrootDst := filepath.Join(chroot, dst)
+ log.Infof("Mounting %q at %q", src, chrootDst)
+
+ if err := specutils.Mount(src, chrootDst, typ, flags); err != nil {
+ return fmt.Errorf("error mounting %q at %q: %v", src, chrootDst, err)
+ }
+ return nil
+}
+
+// setUpChroot creates an empty directory with runsc mounted at /runsc and proc
+// mounted at /proc.
+func setUpChroot() error {
+ // We are a new mount namespace, so we can use /tmp as a directory to
+ // construct a new root.
+ chroot := os.TempDir()
+
+ log.Infof("Setting up sandbox chroot in %q", chroot)
+
+ // Convert all shared mounts into slave to be sure that nothing will be
+ // propagated outside of our namespace.
+ if err := syscall.Mount("", "/", "", syscall.MS_SLAVE|syscall.MS_REC, ""); err != nil {
+ return fmt.Errorf("error converting mounts: %v", err)
+ }
+
+ if err := syscall.Mount("runsc-root", chroot, "tmpfs", syscall.MS_NOSUID|syscall.MS_NODEV|syscall.MS_NOEXEC, ""); err != nil {
+ return fmt.Errorf("error mounting tmpfs in choot: %v", err)
+ }
+
+ if err := mountInChroot(chroot, "/proc", "/proc", "bind", syscall.MS_BIND|syscall.MS_RDONLY|syscall.MS_REC); err != nil {
+ return fmt.Errorf("error mounting proc in chroot: %v", err)
+ }
+
+ if err := mountInChroot(chroot, specutils.ExePath, chrootBinPath, "bind", syscall.MS_BIND|syscall.MS_RDONLY); err != nil {
+ return fmt.Errorf("error mounting runsc in chroot: %v", err)
+ }
+
+ if err := os.Chdir(chroot); err != nil {
+ return fmt.Errorf("error changing working directory: %v", err)
+ }
+
+ if err := syscall.Mount("", chroot, "", syscall.MS_REMOUNT|syscall.MS_RDONLY|syscall.MS_BIND, ""); err != nil {
+ return fmt.Errorf("error remounting chroot in read-only: %v", err)
+ }
+ // pivot_root(new_root, put_old) moves the root filesystem (old_root)
+ // of the calling process to the directory put_old and makes new_root
+ // the new root filesystem of the calling process.
+ //
+ // pivot_root(".", ".") makes a mount of the working directory the new
+ // root filesystem, so it will be moved in "/" and then the old_root
+ // will be moved to "/" too. The parent mount of the old_root will be
+ // new_root, so after umounting the old_root, we will see only
+ // the new_root in "/".
+ if err := syscall.PivotRoot(".", "."); err != nil {
+ return fmt.Errorf("error changing root filesystem: %v", err)
+ }
+
+ if err := syscall.Unmount(".", syscall.MNT_DETACH); err != nil {
+ return fmt.Errorf("error umounting the old root file system: %v", err)
+ }
+
+ return nil
+}
diff --git a/runsc/cmd/cmd.go b/runsc/cmd/cmd.go
index a1c3491a3..fbfc18fc9 100644
--- a/runsc/cmd/cmd.go
+++ b/runsc/cmd/cmd.go
@@ -86,6 +86,28 @@ func setCapsAndCallSelf(args []string, caps *specs.LinuxCapabilities) error {
}
log.Infof("Execve %q again, bye!", binPath)
- syscall.Exec(binPath, args, []string{})
- panic("unreachable")
+ err = syscall.Exec(binPath, args, []string{})
+ return fmt.Errorf("error executing %s: %v", binPath, err)
+}
+
+// callSelfAsNobody sets UID and GID to nobody and then execve's itself again.
+func callSelfAsNobody(args []string) error {
+ // Keep thread locked while user/group are changed.
+ runtime.LockOSThread()
+ defer runtime.UnlockOSThread()
+
+ const nobody = 65534
+
+ if _, _, err := syscall.RawSyscall(syscall.SYS_SETGID, uintptr(nobody), 0, 0); err != 0 {
+ return fmt.Errorf("error setting uid: %v", err)
+ }
+ if _, _, err := syscall.RawSyscall(syscall.SYS_SETUID, uintptr(nobody), 0, 0); err != 0 {
+ return fmt.Errorf("error setting gid: %v", err)
+ }
+
+ binPath := "/runsc"
+
+ log.Infof("Execve %q again, bye!", binPath)
+ err := syscall.Exec(binPath, args, []string{})
+ return fmt.Errorf("error executing %s: %v", binPath, err)
}
diff --git a/runsc/sandbox/BUILD b/runsc/sandbox/BUILD
index d6043bcf7..899fd99de 100644
--- a/runsc/sandbox/BUILD
+++ b/runsc/sandbox/BUILD
@@ -5,7 +5,6 @@ package(licenses = ["notice"]) # Apache 2.0
go_library(
name = "sandbox",
srcs = [
- "chroot.go",
"network.go",
"sandbox.go",
],
diff --git a/runsc/sandbox/chroot.go b/runsc/sandbox/chroot.go
deleted file mode 100644
index 354049871..000000000
--- a/runsc/sandbox/chroot.go
+++ /dev/null
@@ -1,97 +0,0 @@
-// Copyright 2018 Google LLC
-//
-// 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 sandbox
-
-import (
- "fmt"
- "io/ioutil"
- "os"
- "path/filepath"
- "syscall"
-
- "gvisor.googlesource.com/gvisor/pkg/log"
- "gvisor.googlesource.com/gvisor/runsc/specutils"
-)
-
-// chrootBinPath is the location inside the chroot where the runsc binary will
-// be mounted.
-const chrootBinPath = "/runsc"
-
-// mountInChroot creates the destination mount point in the given chroot and
-// mounts the source.
-func mountInChroot(chroot, src, dst, typ string, flags uint32) error {
- chrootDst := filepath.Join(chroot, dst)
- log.Infof("Mounting %q at %q", src, chrootDst)
-
- if err := specutils.Mount(src, chrootDst, typ, flags); err != nil {
- return fmt.Errorf("error mounting %q at %q: %v", src, chrootDst, err)
- }
- return nil
-}
-
-// setUpChroot creates an empty directory with runsc mounted at /runsc and proc
-// mounted at /proc.
-func setUpChroot() (string, error) {
- // Create the chroot directory and make it accessible to all users.
- chroot, err := ioutil.TempDir("", "runsc-sandbox-chroot-")
- if err != nil {
- return "", fmt.Errorf("TempDir() failed: %v", err)
- }
- if err := os.Chmod(chroot, 0777); err != nil {
- return "", fmt.Errorf("Chmod(%q) failed: %v", chroot, err)
- }
- log.Infof("Setting up sandbox chroot in %q", chroot)
-
- // Mount /proc.
- if err := mountInChroot(chroot, "proc", "/proc", "proc", syscall.MS_NOSUID|syscall.MS_NODEV|syscall.MS_NOEXEC); err != nil {
- return "", fmt.Errorf("error mounting proc in chroot: %v", err)
- }
-
- // Mount runsc at /runsc in the chroot.
- binPath, err := specutils.BinPath()
- if err != nil {
- return "", err
- }
- if err := mountInChroot(chroot, binPath, chrootBinPath, "bind", syscall.MS_BIND|syscall.MS_RDONLY); err != nil {
- return "", fmt.Errorf("error mounting runsc in chroot: %v", err)
- }
-
- return chroot, nil
-}
-
-// tearDownChroot unmounts /proc and /runsc from the chroot before deleting the
-// directory.
-func tearDownChroot(chroot string) error {
- log.Debugf("Removing chroot mounts %q", chroot)
-
- // Unmount /proc.
- proc := filepath.Join(chroot, "proc")
- if err := syscall.Unmount(proc, 0); err != nil {
- return fmt.Errorf("error unmounting %q: %v", proc, err)
- }
-
- // Unmount /runsc.
- exe := filepath.Join(chroot, chrootBinPath)
- if err := syscall.Unmount(exe, 0); err != nil {
- return fmt.Errorf("error unmounting %q: %v", exe, err)
- }
-
- // Remove chroot directory.
- if err := os.RemoveAll(chroot); err != nil {
- return fmt.Errorf("error removing %q: %v", chroot, err)
- }
-
- return nil
-}
diff --git a/runsc/sandbox/sandbox.go b/runsc/sandbox/sandbox.go
index fe55ddab8..411200793 100644
--- a/runsc/sandbox/sandbox.go
+++ b/runsc/sandbox/sandbox.go
@@ -56,10 +56,6 @@ type Sandbox struct {
// is not running.
Pid int `json:"pid"`
- // Chroot is the path to the chroot directory that the sandbox process
- // is running in.
- Chroot string `json:"chroot"`
-
// Cgroup has the cgroup configuration for the sandbox.
Cgroup *cgroup.Cgroup `json:"cgroup"`
@@ -491,6 +487,17 @@ func (s *Sandbox) createSandboxProcess(spec *specs.Spec, conf *boot.Config, bund
// rules.
cmd.Args = append(cmd.Args, "--apply-caps=true")
+ // If we have CAP_SYS_ADMIN, we can create an empty chroot and
+ // bind-mount the executable inside it.
+ if conf.TestOnlyAllowRunAsCurrentUserWithoutChroot {
+ log.Warningf("Running sandbox in test mode without chroot. This is only safe in tests!")
+
+ } else if specutils.HasCapabilities(capability.CAP_SYS_ADMIN) {
+ log.Infof("Sandbox will be started in minimal chroot")
+ cmd.Args = append(cmd.Args, "--setup-root")
+ } else {
+ return fmt.Errorf("can't run sandbox process in minimal chroot since we don't have CAP_SYS_ADMIN")
+ }
} else {
log.Infof("Sandbox will be started in new user namespace")
nss = append(nss, specs.LinuxNamespace{Type: specs.UserNamespace})
@@ -499,50 +506,53 @@ func (s *Sandbox) createSandboxProcess(spec *specs.Spec, conf *boot.Config, bund
// as user nobody.
if conf.TestOnlyAllowRunAsCurrentUserWithoutChroot {
log.Warningf("Running sandbox in test mode as current user (uid=%d gid=%d). This is only safe in tests!", os.Getuid(), os.Getgid())
+ log.Warningf("Running sandbox in test mode without chroot. This is only safe in tests!")
} else if specutils.HasCapabilities(capability.CAP_SETUID, capability.CAP_SETGID) {
// Map nobody in the new namespace to nobody in the parent namespace.
+ //
+ // A sandbox process will construct an empty
+ // root for itself, so it has to have the CAP_SYS_ADMIN
+ // capability.
+ //
+ // FIXME: The current implementations of
+ // os/exec doesn't allow to set ambient capabilities if
+ // a process is started in a new user namespace. As a
+ // workaround, we start the sandbox process with the 0
+ // UID and then it constructs a chroot and sets UID to
+ // nobody. https://github.com/golang/go/issues/2315
const nobody = 65534
- cmd.SysProcAttr.UidMappings = []syscall.SysProcIDMap{{
- ContainerID: int(nobody),
- HostID: int(nobody),
- Size: int(1),
- }}
- cmd.SysProcAttr.GidMappings = []syscall.SysProcIDMap{{
- ContainerID: int(nobody),
- HostID: int(nobody),
- Size: int(1),
- }}
+ cmd.SysProcAttr.UidMappings = []syscall.SysProcIDMap{
+ {
+ ContainerID: int(0),
+ HostID: int(nobody - 1),
+ Size: int(1),
+ },
+ {
+ ContainerID: int(nobody),
+ HostID: int(nobody),
+ Size: int(1),
+ },
+ }
+ cmd.SysProcAttr.GidMappings = []syscall.SysProcIDMap{
+ {
+ ContainerID: int(nobody),
+ HostID: int(nobody),
+ Size: int(1),
+ },
+ }
// Set credentials to run as user and group nobody.
cmd.SysProcAttr.Credential = &syscall.Credential{
- Uid: nobody,
+ Uid: 0,
Gid: nobody,
}
+ cmd.Args = append(cmd.Args, "--setup-root")
} else {
return fmt.Errorf("can't run sandbox process as user nobody since we don't have CAP_SETUID or CAP_SETGID")
}
}
- // If we have CAP_SYS_ADMIN, we can create an empty chroot and
- // bind-mount the executable inside it.
- if conf.TestOnlyAllowRunAsCurrentUserWithoutChroot {
- log.Warningf("Running sandbox in test mode without chroot. This is only safe in tests!")
-
- } else if specutils.HasCapabilities(capability.CAP_SYS_ADMIN, capability.CAP_SYS_CHROOT) {
- log.Infof("Sandbox will be started in minimal chroot")
- chroot, err := setUpChroot()
- if err != nil {
- return fmt.Errorf("error setting up chroot: %v", err)
- }
- s.Chroot = chroot // Remember path so it can cleaned up.
- cmd.SysProcAttr.Chroot = chroot
- cmd.Dir = "/"
- cmd.Args[0] = "/runsc"
- cmd.Path = "/runsc"
-
- } else {
- return fmt.Errorf("can't run sandbox process in minimal chroot since we don't have CAP_SYS_ADMIN and CAP_SYS_CHROOT")
- }
+ cmd.Args[0] = "runsc-sandbox"
if s.Cgroup != nil {
cpuNum, err := s.Cgroup.NumCPU()
@@ -676,12 +686,6 @@ func (s *Sandbox) destroy() error {
}
}
- if s.Chroot != "" {
- if err := tearDownChroot(s.Chroot); err != nil {
- return err
- }
- }
-
return nil
}
diff --git a/runsc/test/root/chroot_test.go b/runsc/test/root/chroot_test.go
index 9f705c860..04124703d 100644
--- a/runsc/test/root/chroot_test.go
+++ b/runsc/test/root/chroot_test.go
@@ -52,12 +52,13 @@ func TestChroot(t *testing.T) {
}
// Check that sandbox is chroot'ed.
- chroot, err := filepath.EvalSymlinks(filepath.Join("/proc", strconv.Itoa(pid), "root"))
+ procRoot := filepath.Join("/proc", strconv.Itoa(pid), "root")
+ chroot, err := filepath.EvalSymlinks(procRoot)
if err != nil {
t.Fatalf("error resolving /proc/<pid>/root symlink: %v", err)
}
- if want := "/tmp/runsc-sandbox-chroot-"; !strings.HasPrefix(chroot, want) {
- t.Errorf("sandbox is not chroot'd, it should be inside: %q, got: %q", want, chroot)
+ if chroot != "/" {
+ t.Errorf("sandbox is not chroot'd, it should be inside: /, got: %q", chroot)
}
path, err := filepath.EvalSymlinks(filepath.Join("/proc", strconv.Itoa(pid), "cwd"))
@@ -68,12 +69,12 @@ func TestChroot(t *testing.T) {
t.Errorf("sandbox current dir is wrong, want: %q, got: %q", chroot, path)
}
- fi, err := ioutil.ReadDir(chroot)
+ fi, err := ioutil.ReadDir(procRoot)
if err != nil {
t.Fatalf("error listing %q: %v", chroot, err)
}
if want, got := 2, len(fi); want != got {
- t.Fatalf("chroot dir got %d entries, want %d", want, got)
+ t.Fatalf("chroot dir got %d entries, want %d", got, want)
}
// chroot dir is prepared by runsc and should contains only the executable
@@ -85,11 +86,6 @@ func TestChroot(t *testing.T) {
}
d.CleanUp()
-
- // Check that chroot directory was cleaned up.
- if _, err := os.Stat(chroot); err == nil || !os.IsNotExist(err) {
- t.Errorf("chroot directory %q was not deleted: %v", chroot, err)
- }
}
func TestChrootGofer(t *testing.T) {
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-27 17:49:46 +0000