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|
package validate
import (
"fmt"
"os"
"reflect"
"strings"
"github.com/opencontainers/runc/libcontainer/configs"
)
var (
geteuid = os.Geteuid
getegid = os.Getegid
)
func (v *ConfigValidator) rootless(config *configs.Config) error {
if err := rootlessMappings(config); err != nil {
return err
}
if err := rootlessMount(config); err != nil {
return err
}
// XXX: We currently can't verify the user config at all, because
// configs.Config doesn't store the user-related configs. So this
// has to be verified by setupUser() in init_linux.go.
return nil
}
func hasIDMapping(id int, mappings []configs.IDMap) bool {
for _, m := range mappings {
if id >= m.ContainerID && id < m.ContainerID+m.Size {
return true
}
}
return false
}
func rootlessMappings(config *configs.Config) error {
if euid := geteuid(); euid != 0 {
if !config.Namespaces.Contains(configs.NEWUSER) {
return fmt.Errorf("rootless containers require user namespaces")
}
}
if len(config.UidMappings) == 0 {
return fmt.Errorf("rootless containers requires at least one UID mapping")
}
if len(config.GidMappings) == 0 {
return fmt.Errorf("rootless containers requires at least one UID mapping")
}
return nil
}
// cgroup verifies that the user isn't trying to set any cgroup limits or paths.
func rootlessCgroup(config *configs.Config) error {
// Nothing set at all.
if config.Cgroups == nil || config.Cgroups.Resources == nil {
return nil
}
// Used for comparing to the zero value.
left := reflect.ValueOf(*config.Cgroups.Resources)
right := reflect.Zero(left.Type())
// This is all we need to do, since specconv won't add cgroup options in
// rootless mode.
if !reflect.DeepEqual(left.Interface(), right.Interface()) {
return fmt.Errorf("cannot specify resource limits in rootless container")
}
return nil
}
// mount verifies that the user isn't trying to set up any mounts they don't have
// the rights to do. In addition, it makes sure that no mount has a `uid=` or
// `gid=` option that doesn't resolve to root.
func rootlessMount(config *configs.Config) error {
// XXX: We could whitelist allowed devices at this point, but I'm not
// convinced that's a good idea. The kernel is the best arbiter of
// access control.
for _, mount := range config.Mounts {
// Check that the options list doesn't contain any uid= or gid= entries
// that don't resolve to root.
for _, opt := range strings.Split(mount.Data, ",") {
if strings.HasPrefix(opt, "uid=") {
var uid int
n, err := fmt.Sscanf(opt, "uid=%d", &uid)
if n != 1 || err != nil {
// Ignore unknown mount options.
continue
}
if !hasIDMapping(uid, config.UidMappings) {
return fmt.Errorf("cannot specify uid= mount options for unmapped uid in rootless containers")
}
}
if strings.HasPrefix(opt, "gid=") {
var gid int
n, err := fmt.Sscanf(opt, "gid=%d", &gid)
if n != 1 || err != nil {
// Ignore unknown mount options.
continue
}
if !hasIDMapping(gid, config.GidMappings) {
return fmt.Errorf("cannot specify gid= mount options for unmapped gid in rootless containers")
}
}
}
}
return nil
}
|
