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runc: add support for rootless containers

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This enables the support for the rootless container mode. There are many
restrictions on what rootless containers can do, so many different runC
commands have been disabled:

* runc checkpoint
* runc events
* runc pause
* runc ps
* runc restore
* runc resume
* runc update

The following commands work:

* runc create
* runc delete
* runc exec
* runc kill
* runc list
* runc run
* runc spec
* runc state

In addition, any specification options that imply joining cgroups have
also been disabled. This is due to support for unprivileged subtree
management not being available from Linux upstream.

Signed-off-by: Aleksa Sarai <asarai@suse.de>
This commit is contained in:
Aleksa Sarai
2016-04-23 23:39:42 +10:00
parent 6bd4bd9030
commit d2f49696b0
21 changed files with 742 additions and 193 deletions
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libcontainer/init_linux.go
+36 -5
View File
@@ -58,6 +58,7 @@ type initConfig struct {
ContainerId string `json:"containerid"`
Rlimits []configs.Rlimit `json:"rlimits"`
CreateConsole bool `json:"create_console"`
Rootless bool `json:"rootless"`
}
type initer interface {
@@ -229,18 +230,21 @@ func syncParentHooks(pipe io.ReadWriter) error {
func setupUser(config *initConfig) error {
// Set up defaults.
defaultExecUser := user.ExecUser{
Uid: syscall.Getuid(),
Gid: syscall.Getgid(),
Uid: 0,
Gid: 0,
Home: "/",
}
passwdPath, err := user.GetPasswdPath()
if err != nil {
return err
}
groupPath, err := user.GetGroupPath()
if err != nil {
return err
}
execUser, err := user.GetExecUserPath(config.User, &defaultExecUser, passwdPath, groupPath)
if err != nil {
return err
@@ -253,22 +257,49 @@ func setupUser(config *initConfig) error {
return err
}
}
if config.Rootless {
if execUser.Uid != 0 {
return fmt.Errorf("cannot run as a non-root user in a rootless container")
}
if execUser.Gid != 0 {
return fmt.Errorf("cannot run as a non-root group in a rootless container")
}
// We cannot set any additional groups in a rootless container and thus we
// bail if the user asked us to do so. TODO: We currently can't do this
// earlier, but if libcontainer.Process.User was typesafe this might work.
if len(addGroups) > 0 {
return fmt.Errorf("cannot set any additional groups in a rootless container")
}
}
// before we change to the container's user make sure that the processes STDIO
// is correctly owned by the user that we are switching to.
if err := fixStdioPermissions(execUser); err != nil {
return err
}
suppGroups := append(execUser.Sgids, addGroups...)
if err := syscall.Setgroups(suppGroups); err != nil {
return err
// This isn't allowed in an unprivileged user namespace since Linux 3.19.
// There's nothing we can do about /etc/group entries, so we silently
// ignore setting groups here (since the user didn't explicitly ask us to
// set the group).
if !config.Rootless {
suppGroups := append(execUser.Sgids, addGroups...)
if err := syscall.Setgroups(suppGroups); err != nil {
return err
}
}
if err := system.Setgid(execUser.Gid); err != nil {
return err
}
if err := system.Setuid(execUser.Uid); err != nil {
return err
}
// if we didn't get HOME already, set it based on the user's HOME
if envHome := os.Getenv("HOME"); envHome == "" {
if err := os.Setenv("HOME", execUser.Home); err != nil {