blob: 255080c646eb59c803f4c924bbda51e54d8341c8 [file] [log] [blame]
// +build linux
package selinux
import (
"bufio"
"crypto/rand"
"encoding/binary"
"fmt"
"io"
"os"
"path/filepath"
"regexp"
"strconv"
"strings"
"sync"
"syscall"
"github.com/docker/docker/pkg/mount"
"github.com/opencontainers/runc/libcontainer/system"
)
const (
Enforcing = 1
Permissive = 0
Disabled = -1
selinuxDir = "/etc/selinux/"
selinuxConfig = selinuxDir + "config"
selinuxTypeTag = "SELINUXTYPE"
selinuxTag = "SELINUX"
selinuxPath = "/sys/fs/selinux"
xattrNameSelinux = "security.selinux"
stRdOnly = 0x01
)
var (
assignRegex = regexp.MustCompile(`^([^=]+)=(.*)$`)
mcsList = make(map[string]bool)
mcsLock sync.Mutex
selinuxfs = "unknown"
selinuxEnabled = false // Stores whether selinux is currently enabled
selinuxEnabledChecked = false // Stores whether selinux enablement has been checked or established yet
)
type SELinuxContext map[string]string
// SetDisabled disables selinux support for the package
func SetDisabled() {
selinuxEnabled, selinuxEnabledChecked = false, true
}
// getSelinuxMountPoint returns the path to the mountpoint of an selinuxfs
// filesystem or an empty string if no mountpoint is found. Selinuxfs is
// a proc-like pseudo-filesystem that exposes the selinux policy API to
// processes. The existence of an selinuxfs mount is used to determine
// whether selinux is currently enabled or not.
func getSelinuxMountPoint() string {
if selinuxfs != "unknown" {
return selinuxfs
}
selinuxfs = ""
mounts, err := mount.GetMounts()
if err != nil {
return selinuxfs
}
for _, mount := range mounts {
if mount.Fstype == "selinuxfs" {
selinuxfs = mount.Mountpoint
break
}
}
if selinuxfs != "" {
var buf syscall.Statfs_t
syscall.Statfs(selinuxfs, &buf)
if (buf.Flags & stRdOnly) == 1 {
selinuxfs = ""
}
}
return selinuxfs
}
// SelinuxEnabled returns whether selinux is currently enabled.
func SelinuxEnabled() bool {
if selinuxEnabledChecked {
return selinuxEnabled
}
selinuxEnabledChecked = true
if fs := getSelinuxMountPoint(); fs != "" {
if con, _ := Getcon(); con != "kernel" {
selinuxEnabled = true
}
}
return selinuxEnabled
}
func readConfig(target string) (value string) {
var (
val, key string
bufin *bufio.Reader
)
in, err := os.Open(selinuxConfig)
if err != nil {
return ""
}
defer in.Close()
bufin = bufio.NewReader(in)
for done := false; !done; {
var line string
if line, err = bufin.ReadString('\n'); err != nil {
if err != io.EOF {
return ""
}
done = true
}
line = strings.TrimSpace(line)
if len(line) == 0 {
// Skip blank lines
continue
}
if line[0] == ';' || line[0] == '#' {
// Skip comments
continue
}
if groups := assignRegex.FindStringSubmatch(line); groups != nil {
key, val = strings.TrimSpace(groups[1]), strings.TrimSpace(groups[2])
if key == target {
return strings.Trim(val, "\"")
}
}
}
return ""
}
func getSELinuxPolicyRoot() string {
return selinuxDir + readConfig(selinuxTypeTag)
}
func readCon(name string) (string, error) {
var val string
in, err := os.Open(name)
if err != nil {
return "", err
}
defer in.Close()
_, err = fmt.Fscanf(in, "%s", &val)
return val, err
}
// Setfilecon sets the SELinux label for this path or returns an error.
func Setfilecon(path string, scon string) error {
return system.Lsetxattr(path, xattrNameSelinux, []byte(scon), 0)
}
// Getfilecon returns the SELinux label for this path or returns an error.
func Getfilecon(path string) (string, error) {
con, err := system.Lgetxattr(path, xattrNameSelinux)
if err != nil {
return "", err
}
// Trim the NUL byte at the end of the byte buffer, if present.
if len(con) > 0 && con[len(con)-1] == '\x00' {
con = con[:len(con)-1]
}
return string(con), nil
}
func Setfscreatecon(scon string) error {
return writeCon(fmt.Sprintf("/proc/self/task/%d/attr/fscreate", syscall.Gettid()), scon)
}
func Getfscreatecon() (string, error) {
return readCon(fmt.Sprintf("/proc/self/task/%d/attr/fscreate", syscall.Gettid()))
}
// Getcon returns the SELinux label of the current process thread, or an error.
func Getcon() (string, error) {
return readCon(fmt.Sprintf("/proc/self/task/%d/attr/current", syscall.Gettid()))
}
// Getpidcon returns the SELinux label of the given pid, or an error.
func Getpidcon(pid int) (string, error) {
return readCon(fmt.Sprintf("/proc/%d/attr/current", pid))
}
func Getexeccon() (string, error) {
return readCon(fmt.Sprintf("/proc/self/task/%d/attr/exec", syscall.Gettid()))
}
func writeCon(name string, val string) error {
out, err := os.OpenFile(name, os.O_WRONLY, 0)
if err != nil {
return err
}
defer out.Close()
if val != "" {
_, err = out.Write([]byte(val))
} else {
_, err = out.Write(nil)
}
return err
}
func Setexeccon(scon string) error {
return writeCon(fmt.Sprintf("/proc/self/task/%d/attr/exec", syscall.Gettid()), scon)
}
func (c SELinuxContext) Get() string {
return fmt.Sprintf("%s:%s:%s:%s", c["user"], c["role"], c["type"], c["level"])
}
func NewContext(scon string) SELinuxContext {
c := make(SELinuxContext)
if len(scon) != 0 {
con := strings.SplitN(scon, ":", 4)
c["user"] = con[0]
c["role"] = con[1]
c["type"] = con[2]
c["level"] = con[3]
}
return c
}
func ReserveLabel(scon string) {
if len(scon) != 0 {
con := strings.SplitN(scon, ":", 4)
mcsAdd(con[3])
}
}
func selinuxEnforcePath() string {
return fmt.Sprintf("%s/enforce", selinuxPath)
}
func SelinuxGetEnforce() int {
var enforce int
enforceS, err := readCon(selinuxEnforcePath())
if err != nil {
return -1
}
enforce, err = strconv.Atoi(string(enforceS))
if err != nil {
return -1
}
return enforce
}
func SelinuxSetEnforce(mode int) error {
return writeCon(selinuxEnforcePath(), fmt.Sprintf("%d", mode))
}
func SelinuxGetEnforceMode() int {
switch readConfig(selinuxTag) {
case "enforcing":
return Enforcing
case "permissive":
return Permissive
}
return Disabled
}
func mcsAdd(mcs string) error {
mcsLock.Lock()
defer mcsLock.Unlock()
if mcsList[mcs] {
return fmt.Errorf("MCS Label already exists")
}
mcsList[mcs] = true
return nil
}
func mcsDelete(mcs string) {
mcsLock.Lock()
mcsList[mcs] = false
mcsLock.Unlock()
}
func IntToMcs(id int, catRange uint32) string {
var (
SETSIZE = int(catRange)
TIER = SETSIZE
ORD = id
)
if id < 1 || id > 523776 {
return ""
}
for ORD > TIER {
ORD = ORD - TIER
TIER -= 1
}
TIER = SETSIZE - TIER
ORD = ORD + TIER
return fmt.Sprintf("s0:c%d,c%d", TIER, ORD)
}
func uniqMcs(catRange uint32) string {
var (
n uint32
c1, c2 uint32
mcs string
)
for {
binary.Read(rand.Reader, binary.LittleEndian, &n)
c1 = n % catRange
binary.Read(rand.Reader, binary.LittleEndian, &n)
c2 = n % catRange
if c1 == c2 {
continue
} else {
if c1 > c2 {
t := c1
c1 = c2
c2 = t
}
}
mcs = fmt.Sprintf("s0:c%d,c%d", c1, c2)
if err := mcsAdd(mcs); err != nil {
continue
}
break
}
return mcs
}
func FreeLxcContexts(scon string) {
if len(scon) != 0 {
con := strings.SplitN(scon, ":", 4)
mcsDelete(con[3])
}
}
func GetLxcContexts() (processLabel string, fileLabel string) {
var (
val, key string
bufin *bufio.Reader
)
if !SelinuxEnabled() {
return "", ""
}
lxcPath := fmt.Sprintf("%s/contexts/lxc_contexts", getSELinuxPolicyRoot())
in, err := os.Open(lxcPath)
if err != nil {
return "", ""
}
defer in.Close()
bufin = bufio.NewReader(in)
for done := false; !done; {
var line string
if line, err = bufin.ReadString('\n'); err != nil {
if err == io.EOF {
done = true
} else {
goto exit
}
}
line = strings.TrimSpace(line)
if len(line) == 0 {
// Skip blank lines
continue
}
if line[0] == ';' || line[0] == '#' {
// Skip comments
continue
}
if groups := assignRegex.FindStringSubmatch(line); groups != nil {
key, val = strings.TrimSpace(groups[1]), strings.TrimSpace(groups[2])
if key == "process" {
processLabel = strings.Trim(val, "\"")
}
if key == "file" {
fileLabel = strings.Trim(val, "\"")
}
}
}
if processLabel == "" || fileLabel == "" {
return "", ""
}
exit:
// mcs := IntToMcs(os.Getpid(), 1024)
mcs := uniqMcs(1024)
scon := NewContext(processLabel)
scon["level"] = mcs
processLabel = scon.Get()
scon = NewContext(fileLabel)
scon["level"] = mcs
fileLabel = scon.Get()
return processLabel, fileLabel
}
func SecurityCheckContext(val string) error {
return writeCon(fmt.Sprintf("%s.context", selinuxPath), val)
}
func CopyLevel(src, dest string) (string, error) {
if src == "" {
return "", nil
}
if err := SecurityCheckContext(src); err != nil {
return "", err
}
if err := SecurityCheckContext(dest); err != nil {
return "", err
}
scon := NewContext(src)
tcon := NewContext(dest)
mcsDelete(tcon["level"])
mcsAdd(scon["level"])
tcon["level"] = scon["level"]
return tcon.Get(), nil
}
// Prevent users from relabing system files
func badPrefix(fpath string) error {
var badprefixes = []string{"/usr"}
for _, prefix := range badprefixes {
if fpath == prefix || strings.HasPrefix(fpath, fmt.Sprintf("%s/", prefix)) {
return fmt.Errorf("Relabeling content in %s is not allowed.", prefix)
}
}
return nil
}
// Change the fpath file object to the SELinux label scon.
// If the fpath is a directory and recurse is true Chcon will walk the
// directory tree setting the label
func Chcon(fpath string, scon string, recurse bool) error {
if scon == "" {
return nil
}
if err := badPrefix(fpath); err != nil {
return err
}
callback := func(p string, info os.FileInfo, err error) error {
return Setfilecon(p, scon)
}
if recurse {
return filepath.Walk(fpath, callback)
}
return Setfilecon(fpath, scon)
}
// DupSecOpt takes an SELinux process label and returns security options that
// can will set the SELinux Type and Level for future container processes
func DupSecOpt(src string) []string {
if src == "" {
return nil
}
con := NewContext(src)
if con["user"] == "" ||
con["role"] == "" ||
con["type"] == "" ||
con["level"] == "" {
return nil
}
return []string{"label:user:" + con["user"],
"label:role:" + con["role"],
"label:type:" + con["type"],
"label:level:" + con["level"]}
}
// DisableSecOpt returns a security opt that can be used to disabling SELinux
// labeling support for future container processes
func DisableSecOpt() []string {
return []string{"label:disable"}
}