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package idtools
import (
"bufio"
"fmt"
"os"
"sort"
"strconv"
"strings"
)
// IDMap contains a single entry for user namespace range remapping. An array
// of IDMap entries represents the structure that will be provided to the Linux
// kernel for creating a user namespace.
type IDMap struct {
ContainerID int `json:"container_id"`
HostID int `json:"host_id"`
Size int `json:"size"`
}
type subIDRange struct {
Start int
Length int
}
type ranges []subIDRange
func (e ranges) Len() int { return len(e) }
func (e ranges) Swap(i, j int) { e[i], e[j] = e[j], e[i] }
func (e ranges) Less(i, j int) bool { return e[i].Start < e[j].Start }
const (
subuidFileName string = "/etc/subuid"
subgidFileName string = "/etc/subgid"
)
// MkdirAllAs creates a directory (include any along the path) and then modifies
// ownership to the requested uid/gid. If the directory already exists, this
// function will still change ownership to the requested uid/gid pair.
func MkdirAllAs(path string, mode os.FileMode, ownerUID, ownerGID int) error {
return mkdirAs(path, mode, ownerUID, ownerGID, true, true)
}
// MkdirAllNewAs creates a directory (include any along the path) and then modifies
// ownership ONLY of newly created directories to the requested uid/gid. If the
// directories along the path exist, no change of ownership will be performed
func MkdirAllNewAs(path string, mode os.FileMode, ownerUID, ownerGID int) error {
return mkdirAs(path, mode, ownerUID, ownerGID, true, false)
}
// MkdirAs creates a directory and then modifies ownership to the requested uid/gid.
// If the directory already exists, this function still changes ownership
func MkdirAs(path string, mode os.FileMode, ownerUID, ownerGID int) error {
return mkdirAs(path, mode, ownerUID, ownerGID, false, true)
}
// GetRootUIDGID retrieves the remapped root uid/gid pair from the set of maps.
// If the maps are empty, then the root uid/gid will default to "real" 0/0
func GetRootUIDGID(uidMap, gidMap []IDMap) (int, int, error) {
var uid, gid int
if uidMap != nil {
xUID, err := ToHost(0, uidMap)
if err != nil {
return -1, -1, err
}
uid = xUID
}
if gidMap != nil {
xGID, err := ToHost(0, gidMap)
if err != nil {
return -1, -1, err
}
gid = xGID
}
return uid, gid, nil
}
// ToContainer takes an id mapping, and uses it to translate a
// host ID to the remapped ID. If no map is provided, then the translation
// assumes a 1-to-1 mapping and returns the passed in id
func ToContainer(hostID int, idMap []IDMap) (int, error) {
if idMap == nil {
return hostID, nil
}
for _, m := range idMap {
if (hostID >= m.HostID) && (hostID <= (m.HostID + m.Size - 1)) {
contID := m.ContainerID + (hostID - m.HostID)
return contID, nil
}
}
return -1, fmt.Errorf("Host ID %d cannot be mapped to a container ID", hostID)
}
// ToHost takes an id mapping and a remapped ID, and translates the
// ID to the mapped host ID. If no map is provided, then the translation
// assumes a 1-to-1 mapping and returns the passed in id #
func ToHost(contID int, idMap []IDMap) (int, error) {
if idMap == nil {
return contID, nil
}
for _, m := range idMap {
if (contID >= m.ContainerID) && (contID <= (m.ContainerID + m.Size - 1)) {
hostID := m.HostID + (contID - m.ContainerID)
return hostID, nil
}
}
return -1, fmt.Errorf("Container ID %d cannot be mapped to a host ID", contID)
}
// CreateIDMappings takes a requested user and group name and
// using the data from /etc/sub{uid,gid} ranges, creates the
// proper uid and gid remapping ranges for that user/group pair
func CreateIDMappings(username, groupname string) ([]IDMap, []IDMap, error) {
subuidRanges, err := parseSubuid(username)
if err != nil {
return nil, nil, err
}
subgidRanges, err := parseSubgid(groupname)
if err != nil {
return nil, nil, err
}
if len(subuidRanges) == 0 {
return nil, nil, fmt.Errorf("No subuid ranges found for user %q", username)
}
if len(subgidRanges) == 0 {
return nil, nil, fmt.Errorf("No subgid ranges found for group %q", groupname)
}
return createIDMap(subuidRanges), createIDMap(subgidRanges), nil
}
func createIDMap(subidRanges ranges) []IDMap {
idMap := []IDMap{}
// sort the ranges by lowest ID first
sort.Sort(subidRanges)
containerID := 0
for _, idrange := range subidRanges {
idMap = append(idMap, IDMap{
ContainerID: containerID,
HostID: idrange.Start,
Size: idrange.Length,
})
containerID = containerID + idrange.Length
}
return idMap
}
func parseSubuid(username string) (ranges, error) {
return parseSubidFile(subuidFileName, username)
}
func parseSubgid(username string) (ranges, error) {
return parseSubidFile(subgidFileName, username)
}
func parseSubidFile(path, username string) (ranges, error) {
var rangeList ranges
subidFile, err := os.Open(path)
if err != nil {
return rangeList, err
}
defer subidFile.Close()
s := bufio.NewScanner(subidFile)
for s.Scan() {
if err := s.Err(); err != nil {
return rangeList, err
}
text := strings.TrimSpace(s.Text())
if text == "" {
continue
}
parts := strings.Split(text, ":")
if len(parts) != 3 {
return rangeList, fmt.Errorf("Cannot parse subuid/gid information: Format not correct for %s file", path)
}
if parts[0] == username {
// return the first entry for a user; ignores potential for multiple ranges per user
startid, err := strconv.Atoi(parts[1])
if err != nil {
return rangeList, fmt.Errorf("String to int conversion failed during subuid/gid parsing of %s: %v", path, err)
}
length, err := strconv.Atoi(parts[2])
if err != nil {
return rangeList, fmt.Errorf("String to int conversion failed during subuid/gid parsing of %s: %v", path, err)
}
rangeList = append(rangeList, subIDRange{startid, length})
}
}
return rangeList, nil
}
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