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89 lines
3.4 KiB
Go
89 lines
3.4 KiB
Go
// +build experimental
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package daemon
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import (
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"fmt"
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"os"
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"path/filepath"
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"runtime"
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"github.com/Sirupsen/logrus"
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"github.com/docker/docker/pkg/idtools"
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"github.com/docker/engine-api/types/container"
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)
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func setupRemappedRoot(config *Config) ([]idtools.IDMap, []idtools.IDMap, error) {
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if runtime.GOOS != "linux" && config.RemappedRoot != "" {
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return nil, nil, fmt.Errorf("User namespaces are only supported on Linux")
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}
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// if the daemon was started with remapped root option, parse
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// the config option to the int uid,gid values
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var (
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uidMaps, gidMaps []idtools.IDMap
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)
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if config.RemappedRoot != "" {
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username, groupname, err := parseRemappedRoot(config.RemappedRoot)
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if err != nil {
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return nil, nil, err
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}
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if username == "root" {
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// Cannot setup user namespaces with a 1-to-1 mapping; "--root=0:0" is a no-op
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// effectively
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logrus.Warnf("User namespaces: root cannot be remapped with itself; user namespaces are OFF")
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return uidMaps, gidMaps, nil
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}
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logrus.Infof("User namespaces: ID ranges will be mapped to subuid/subgid ranges of: %s:%s", username, groupname)
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// update remapped root setting now that we have resolved them to actual names
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config.RemappedRoot = fmt.Sprintf("%s:%s", username, groupname)
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uidMaps, gidMaps, err = idtools.CreateIDMappings(username, groupname)
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if err != nil {
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return nil, nil, fmt.Errorf("Can't create ID mappings: %v", err)
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}
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}
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return uidMaps, gidMaps, nil
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}
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func setupDaemonRoot(config *Config, rootDir string, rootUID, rootGID int) error {
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config.Root = rootDir
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// the docker root metadata directory needs to have execute permissions for all users (o+x)
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// so that syscalls executing as non-root, operating on subdirectories of the graph root
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// (e.g. mounted layers of a container) can traverse this path.
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// The user namespace support will create subdirectories for the remapped root host uid:gid
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// pair owned by that same uid:gid pair for proper write access to those needed metadata and
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// layer content subtrees.
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if _, err := os.Stat(rootDir); err == nil {
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// root current exists; verify the access bits are correct by setting them
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if err = os.Chmod(rootDir, 0701); err != nil {
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return err
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}
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} else if os.IsNotExist(err) {
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// no root exists yet, create it 0701 with root:root ownership
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if err := os.MkdirAll(rootDir, 0701); err != nil {
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return err
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}
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}
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// if user namespaces are enabled we will create a subtree underneath the specified root
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// with any/all specified remapped root uid/gid options on the daemon creating
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// a new subdirectory with ownership set to the remapped uid/gid (so as to allow
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// `chdir()` to work for containers namespaced to that uid/gid)
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if config.RemappedRoot != "" {
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config.Root = filepath.Join(rootDir, fmt.Sprintf("%d.%d", rootUID, rootGID))
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logrus.Debugf("Creating user namespaced daemon root: %s", config.Root)
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// Create the root directory if it doesn't exists
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if err := idtools.MkdirAllAs(config.Root, 0700, rootUID, rootGID); err != nil {
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return fmt.Errorf("Cannot create daemon root: %s: %v", config.Root, err)
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}
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}
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return nil
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}
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func (daemon *Daemon) verifyExperimentalContainerSettings(hostConfig *container.HostConfig, config *container.Config) ([]string, error) {
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if hostConfig.Privileged && daemon.configStore.RemappedRoot != "" {
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return nil, fmt.Errorf("Privileged mode is incompatible with user namespace mappings")
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}
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return nil, nil
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}
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