mirror of
https://github.com/criyle/go-sandbox.git
synced 2025-11-04 14:49:53 +08:00
261 lines
6.2 KiB
Go
261 lines
6.2 KiB
Go
package container
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import (
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"context"
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"fmt"
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"os"
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"sync"
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"syscall"
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"github.com/criyle/go-sandbox/pkg/forkexec"
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"github.com/criyle/go-sandbox/pkg/memfd"
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"github.com/criyle/go-sandbox/pkg/mount"
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"github.com/criyle/go-sandbox/pkg/unixsocket"
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"github.com/criyle/go-sandbox/types"
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"golang.org/x/sys/unix"
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)
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// PathEnv defines path environment variable for the container init process
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const PathEnv = "PATH=/usr/local/bin:/usr/bin:/bin"
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// Builder builds instance of container environment
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type Builder struct {
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// Root is container root mount path, empty uses current work path
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Root string
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// Mounts defines container mount points, empty uses default mounts
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Mounts []mount.SyscallParams
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// Stderr defines whether to dup container stderr to stderr for debug
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Stderr bool
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// ExecFile defines executable that called Init, otherwise defer current
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// executable (/proc/self/exe)
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ExecFile *os.File
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// CredGenerator defines a credential generator used to create new container
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CredGenerator CredGenerator
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}
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// CredGenerator generates uid / gid credential used by container
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// to isolate process and file system access
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type CredGenerator interface {
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Get() syscall.Credential
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}
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// Environment holds single progrem containerized environment
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type Environment interface {
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Ping() error
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Open([]OpenCmd) ([]*os.File, error)
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Delete(p string) error
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Reset() error
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Execve(context.Context, ExecveParam) <-chan types.Result
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Destroy() error
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}
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// container manages single pre-forked container environment
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type container struct {
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pid int // underlying container init pid
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socket *socket // host - container communication
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mu sync.Mutex // lock to avoid race condition
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}
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// Build creates new environment with underlying container
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func (b *Builder) Build() (Environment, error) {
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var (
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err error
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cred syscall.Credential
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uidMap, gidMap []syscall.SysProcIDMap
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)
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// container mount points
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mounts := b.Mounts
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if len(mounts) == 0 {
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if mounts, err = mount.NewDefaultBuilder().
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WithTmpfs("w", ""). // work dir
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WithTmpfs("tmp", ""). // tmp
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Build(true); err != nil {
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return nil, fmt.Errorf("container: failed to build rootfs mount %v", err)
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}
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}
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// container root directory on the host
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root := b.Root
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if root == "" {
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if root, err = os.Getwd(); err != nil {
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return nil, fmt.Errorf("container: failed to get work directory %v", err)
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}
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}
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// prepare stdin / stdout / stderr
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devNull, err := os.OpenFile(os.DevNull, os.O_RDWR, os.ModePerm)
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if err != nil {
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return nil, fmt.Errorf("container: failed to open devNull %v", err)
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}
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defer devNull.Close()
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files := make([]uintptr, 0, 4)
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files = append(files, devNull.Fd(), devNull.Fd())
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if b.Stderr {
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files = append(files, os.Stderr.Fd())
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} else {
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files = append(files, devNull.Fd())
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}
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// prepare container exec file
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execFile, err := b.exec()
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if err != nil {
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return nil, fmt.Errorf("container: prepare exec %v", err)
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}
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defer execFile.Close()
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// prepare host <-> container unix socket
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ins, outs, err := newPassCredSocketPair()
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if err != nil {
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return nil, fmt.Errorf("container: failed to create socket: %v", err)
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}
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defer outs.Close()
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outf, err := outs.File()
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if err != nil {
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ins.Close()
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return nil, fmt.Errorf("container: failed to dup container socket fd %v", err)
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}
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defer outf.Close()
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files = append(files, uintptr(outf.Fd()))
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// prepare container running credential
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if b.CredGenerator != nil {
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cred = b.CredGenerator.Get()
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uidMap, gidMap = getIDMapping(&cred)
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}
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r := &forkexec.Runner{
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Args: []string{os.Args[0], initArg},
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Env: []string{PathEnv},
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ExecFile: execFile.Fd(),
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Files: files,
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WorkDir: containerWD,
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CloneFlags: forkexec.UnshareFlags,
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Mounts: mounts,
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HostName: containerName,
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DomainName: containerName,
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PivotRoot: root,
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UIDMappings: uidMap,
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GIDMappings: gidMap,
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}
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pid, err := r.Start()
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if err != nil {
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ins.Close()
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return nil, fmt.Errorf("container: failed to start container %v", err)
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}
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c := &container{
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pid: pid,
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socket: newSocket(ins),
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}
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// set configuration and check if container creation successful
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if err = c.conf(&containerConfig{
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Cred: b.CredGenerator != nil,
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}); err != nil {
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c.Destroy()
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return nil, err
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}
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return c, nil
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}
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// Destroy kill the container process (with its children)
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// if stderr enabled, collect the output as error
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func (c *container) Destroy() error {
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// close socket (abort any ongoing command)
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c.socket.Close()
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// wait commands terminates
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c.mu.Lock()
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defer c.mu.Unlock()
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// kill process
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var wstatus unix.WaitStatus
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unix.Kill(c.pid, unix.SIGKILL)
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// wait for container process to exit
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_, err := unix.Wait4(c.pid, &wstatus, 0, nil)
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for err == unix.EINTR {
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_, err = unix.Wait4(c.pid, &wstatus, 0, nil)
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}
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return err
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}
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// exec prepares executable
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func (b *Builder) exec() (*os.File, error) {
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if b.ExecFile != nil {
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return b.ExecFile, nil
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}
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return OpenCurrentExec()
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}
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// OpenCurrentExec opens current executable and dup and seal it to memfd
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func OpenCurrentExec() (*os.File, error) {
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self, err := os.Open(currentExec)
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if err != nil {
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return nil, fmt.Errorf("failed to open %v: %v", currentExec, err)
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}
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defer self.Close()
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execFile, err := memfd.DupToMemfd("init", self)
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if err != nil {
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return nil, fmt.Errorf("failed to create memfd: %v", err)
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}
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return execFile, nil
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}
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func newPassCredSocketPair() (*unixsocket.Socket, *unixsocket.Socket, error) {
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ins, outs, err := unixsocket.NewSocketPair()
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if err != nil {
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return nil, nil, err
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}
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if err = ins.SetPassCred(1); err != nil {
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ins.Close()
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outs.Close()
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return nil, nil, err
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}
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if err = outs.SetPassCred(1); err != nil {
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ins.Close()
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outs.Close()
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return nil, nil, err
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}
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return ins, outs, nil
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}
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func getIDMapping(cred *syscall.Credential) ([]syscall.SysProcIDMap, []syscall.SysProcIDMap) {
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uidMap := []syscall.SysProcIDMap{
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{
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ContainerID: 0,
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HostID: os.Geteuid(),
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Size: 1,
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},
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{
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ContainerID: containerUID,
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HostID: int(cred.Uid),
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Size: 1,
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},
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}
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gidMap := []syscall.SysProcIDMap{
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{
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ContainerID: 0,
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HostID: os.Getegid(),
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Size: 1,
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},
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{
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ContainerID: containerGID,
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HostID: int(cred.Gid),
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Size: 1,
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},
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}
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return uidMap, gidMap
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}
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