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// Copyright 2018 Google Inc.
//
// 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 specutils
import (
"fmt"
"os"
"os/exec"
"path/filepath"
"runtime"
"syscall"
specs "github.com/opencontainers/runtime-spec/specs-go"
"golang.org/x/sys/unix"
"gvisor.googlesource.com/gvisor/pkg/log"
)
// nsCloneFlag returns the clone flag that can be used to set a namespace of
// the given type.
func nsCloneFlag(nst specs.LinuxNamespaceType) uintptr {
switch nst {
case specs.IPCNamespace:
return syscall.CLONE_NEWIPC
case specs.MountNamespace:
return syscall.CLONE_NEWNS
case specs.NetworkNamespace:
return syscall.CLONE_NEWNET
case specs.PIDNamespace:
return syscall.CLONE_NEWPID
case specs.UTSNamespace:
return syscall.CLONE_NEWUTS
case specs.UserNamespace:
return syscall.CLONE_NEWUSER
case specs.CgroupNamespace:
panic("cgroup namespace has no associated clone flag")
default:
panic(fmt.Sprintf("unknown namespace %v", nst))
}
}
// nsPath returns the path of the namespace for the current process and the
// given namespace.
func nsPath(nst specs.LinuxNamespaceType) string {
base := "/proc/self/ns"
switch nst {
case specs.CgroupNamespace:
return filepath.Join(base, "cgroup")
case specs.IPCNamespace:
return filepath.Join(base, "ipc")
case specs.MountNamespace:
return filepath.Join(base, "mnt")
case specs.NetworkNamespace:
return filepath.Join(base, "net")
case specs.PIDNamespace:
return filepath.Join(base, "pid")
case specs.UserNamespace:
return filepath.Join(base, "user")
case specs.UTSNamespace:
return filepath.Join(base, "uts")
default:
panic(fmt.Sprintf("unknown namespace %v", nst))
}
}
// GetNS returns true and the namespace with the given type from the slice of
// namespaces in the spec. It returns false if the slice does not contain a
// namespace with the type.
func GetNS(nst specs.LinuxNamespaceType, s *specs.Spec) (specs.LinuxNamespace, bool) {
if s.Linux == nil {
return specs.LinuxNamespace{}, false
}
for _, ns := range s.Linux.Namespaces {
if ns.Type == nst {
return ns, true
}
}
return specs.LinuxNamespace{}, false
}
// FilterNS returns a slice of namespaces from the spec with types that match
// those in the `filter` slice.
func FilterNS(filter []specs.LinuxNamespaceType, s *specs.Spec) []specs.LinuxNamespace {
if s.Linux == nil {
return nil
}
var out []specs.LinuxNamespace
for _, nst := range filter {
if ns, ok := GetNS(nst, s); ok {
out = append(out, ns)
}
}
return out
}
// SetNS sets the namespace of the given type. It must be called with
// OSThreadLocked.
func SetNS(fd, nsType uintptr) error {
if _, _, err := syscall.RawSyscall(unix.SYS_SETNS, fd, nsType, 0); err != 0 {
return err
}
return nil
}
// ApplyNS applies the namespace on the current thread and returns a function
// that will restore the namespace to the original value.
//
// Preconditions: Must be called with os thread locked.
func ApplyNS(ns specs.LinuxNamespace) (func(), error) {
log.Infof("applying namespace %v at path %q", ns.Type, ns.Path)
newNS, err := os.Open(ns.Path)
if err != nil {
return nil, fmt.Errorf("error opening %q: %v", ns.Path, err)
}
defer newNS.Close()
// Store current netns to restore back after child is started.
curPath := nsPath(ns.Type)
oldNS, err := os.Open(curPath)
if err != nil {
return nil, fmt.Errorf("error opening %q: %v", curPath, err)
}
// Set netns to the one requested and setup function to restore it back.
flag := nsCloneFlag(ns.Type)
if err := SetNS(newNS.Fd(), flag); err != nil {
oldNS.Close()
return nil, fmt.Errorf("error setting namespace of type %v and path %q: %v", ns.Type, ns.Path, err)
}
return func() {
log.Infof("restoring namespace %v", ns.Type)
defer oldNS.Close()
if err := SetNS(oldNS.Fd(), flag); err != nil {
panic(fmt.Sprintf("error restoring namespace: of type %v: %v", ns.Type, err))
}
}, nil
}
// StartInNS joins or creates the given namespaces and calls cmd.Start before
// restoring the namespaces to the original values.
func StartInNS(cmd *exec.Cmd, nss []specs.LinuxNamespace) error {
// We are about to setup namespaces, which requires the os thread being
// locked so that Go doesn't change the thread out from under us.
runtime.LockOSThread()
defer runtime.UnlockOSThread()
if cmd.SysProcAttr == nil {
cmd.SysProcAttr = &syscall.SysProcAttr{}
}
for _, ns := range nss {
if ns.Path == "" {
// No path. Just set a flag to create a new namespace.
cmd.SysProcAttr.Cloneflags |= nsCloneFlag(ns.Type)
continue
}
// Join the given namespace, and restore the current namespace
// before exiting.
restoreNS, err := ApplyNS(ns)
if err != nil {
return err
}
defer restoreNS()
}
return cmd.Start()
}
// SetUIDGIDMappings sets the given uid/gid mappings from the spec on the cmd.
func SetUIDGIDMappings(cmd *exec.Cmd, s *specs.Spec) {
if s.Linux == nil {
return
}
if cmd.SysProcAttr == nil {
cmd.SysProcAttr = &syscall.SysProcAttr{}
}
for _, idMap := range s.Linux.UIDMappings {
log.Infof("Mapping host uid %d to container uid %d (size=%d)", idMap.HostID, idMap.ContainerID, idMap.Size)
cmd.SysProcAttr.UidMappings = append(cmd.SysProcAttr.UidMappings, syscall.SysProcIDMap{
ContainerID: int(idMap.ContainerID),
HostID: int(idMap.HostID),
Size: int(idMap.Size),
})
}
for _, idMap := range s.Linux.GIDMappings {
log.Infof("Mapping host gid %d to container gid %d (size=%d)", idMap.HostID, idMap.ContainerID, idMap.Size)
cmd.SysProcAttr.GidMappings = append(cmd.SysProcAttr.GidMappings, syscall.SysProcIDMap{
ContainerID: int(idMap.ContainerID),
HostID: int(idMap.HostID),
Size: int(idMap.Size),
})
}
}
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