Build and install from GOPATH

* Rename 'vendor/src' -> 'vendor'
  * Ignore vendor/ instead of vendor/src/ for lint
* Rename 'cmd/client' -> 'cmd/ocic' to make it 'go install'able
* Rename 'cmd/server' -> 'cmd/ocid' to make it 'go install'able
* Update Makefile to build and install from GOPATH
* Update tests to locate ocid/ocic in GOPATH/bin
* Search for binaries in GOPATH/bin instead of PATH
* Install tools using `go get -u`, so they are updated on each run

Signed-off-by: Jonathan Yu <jawnsy@redhat.com>

vendor/github.com/opencontainers/runc/libcontainer/label/label.go

@@ -0,0 +1,80 @@
+// +build !selinux !linux
+
+package label
+
+// InitLabels returns the process label and file labels to be used within
+// the container.  A list of options can be passed into this function to alter
+// the labels.
+func InitLabels(options []string) (string, string, error) {
+	return "", "", nil
+}
+
+func GenLabels(options string) (string, string, error) {
+	return "", "", nil
+}
+
+func FormatMountLabel(src string, mountLabel string) string {
+	return src
+}
+
+func SetProcessLabel(processLabel string) error {
+	return nil
+}
+
+func GetFileLabel(path string) (string, error) {
+	return "", nil
+}
+
+func SetFileLabel(path string, fileLabel string) error {
+	return nil
+}
+
+func SetFileCreateLabel(fileLabel string) error {
+	return nil
+}
+
+func Relabel(path string, fileLabel string, shared bool) error {
+	return nil
+}
+
+func GetPidLabel(pid int) (string, error) {
+	return "", nil
+}
+
+func Init() {
+}
+
+func ReserveLabel(label string) error {
+	return nil
+}
+
+func UnreserveLabel(label string) error {
+	return nil
+}
+
+// DupSecOpt takes a process label and returns security options that
+// can be used to set duplicate labels on future container processes
+func DupSecOpt(src string) []string {
+	return nil
+}
+
+// DisableSecOpt returns a security opt that can disable labeling
+// support for future container processes
+func DisableSecOpt() []string {
+	return nil
+}
+
+// Validate checks that the label does not include unexpected options
+func Validate(label string) error {
+	return nil
+}
+
+// RelabelNeeded checks whether the user requested a relabel
+func RelabelNeeded(label string) bool {
+	return false
+}
+
+// IsShared checks that the label includes a "shared" mark
+func IsShared(label string) bool {
+	return false
+}

vendor/github.com/opencontainers/runc/libcontainer/label/label_selinux.go

@@ -0,0 +1,204 @@
+// +build selinux,linux
+
+package label
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/opencontainers/runc/libcontainer/selinux"
+)
+
+// Valid Label Options
+var validOptions = map[string]bool{
+	"disable": true,
+	"type":    true,
+	"user":    true,
+	"role":    true,
+	"level":   true,
+}
+
+var ErrIncompatibleLabel = fmt.Errorf("Bad SELinux option z and Z can not be used together")
+
+// InitLabels returns the process label and file labels to be used within
+// the container.  A list of options can be passed into this function to alter
+// the labels.  The labels returned will include a random MCS String, that is
+// guaranteed to be unique.
+func InitLabels(options []string) (string, string, error) {
+	if !selinux.SelinuxEnabled() {
+		return "", "", nil
+	}
+	processLabel, mountLabel := selinux.GetLxcContexts()
+	if processLabel != "" {
+		pcon := selinux.NewContext(processLabel)
+		mcon := selinux.NewContext(mountLabel)
+		for _, opt := range options {
+			val := strings.SplitN(opt, "=", 2)
+			if val[0] != "label" {
+				continue
+			}
+			if len(val) < 2 {
+				return "", "", fmt.Errorf("bad label option %q, valid options 'disable' or \n'user, role, level, type' followed by ':' and a value", opt)
+			}
+			if val[1] == "disable" {
+				return "", "", nil
+			}
+			con := strings.SplitN(val[1], ":", 2)
+			if len(con) < 2 || !validOptions[con[0]] {
+				return "", "", fmt.Errorf("bad label option %q, valid options 'disable, user, role, level, type'", con[0])
+
+			}
+			pcon[con[0]] = con[1]
+			if con[0] == "level" || con[0] == "user" {
+				mcon[con[0]] = con[1]
+			}
+		}
+		processLabel = pcon.Get()
+		mountLabel = mcon.Get()
+	}
+	return processLabel, mountLabel, nil
+}
+
+// DEPRECATED: The GenLabels function is only to be used during the transition to the official API.
+func GenLabels(options string) (string, string, error) {
+	return InitLabels(strings.Fields(options))
+}
+
+// FormatMountLabel returns a string to be used by the mount command.
+// The format of this string will be used to alter the labeling of the mountpoint.
+// The string returned is suitable to be used as the options field of the mount command.
+// If you need to have additional mount point options, you can pass them in as
+// the first parameter.  Second parameter is the label that you wish to apply
+// to all content in the mount point.
+func FormatMountLabel(src, mountLabel string) string {
+	if mountLabel != "" {
+		switch src {
+		case "":
+			src = fmt.Sprintf("context=%q", mountLabel)
+		default:
+			src = fmt.Sprintf("%s,context=%q", src, mountLabel)
+		}
+	}
+	return src
+}
+
+// SetProcessLabel takes a process label and tells the kernel to assign the
+// label to the next program executed by the current process.
+func SetProcessLabel(processLabel string) error {
+	if processLabel == "" {
+		return nil
+	}
+	return selinux.Setexeccon(processLabel)
+}
+
+// GetProcessLabel returns the process label that the kernel will assign
+// to the next program executed by the current process.  If "" is returned
+// this indicates that the default labeling will happen for the process.
+func GetProcessLabel() (string, error) {
+	return selinux.Getexeccon()
+}
+
+// GetFileLabel returns the label for specified path
+func GetFileLabel(path string) (string, error) {
+	return selinux.Getfilecon(path)
+}
+
+// SetFileLabel modifies the "path" label to the specified file label
+func SetFileLabel(path string, fileLabel string) error {
+	if selinux.SelinuxEnabled() && fileLabel != "" {
+		return selinux.Setfilecon(path, fileLabel)
+	}
+	return nil
+}
+
+// SetFileCreateLabel tells the kernel the label for all files to be created
+func SetFileCreateLabel(fileLabel string) error {
+	if selinux.SelinuxEnabled() {
+		return selinux.Setfscreatecon(fileLabel)
+	}
+	return nil
+}
+
+// Relabel changes the label of path to the filelabel string.
+// It changes the MCS label to s0 if shared is true.
+// This will allow all containers to share the content.
+func Relabel(path string, fileLabel string, shared bool) error {
+	if !selinux.SelinuxEnabled() {
+		return nil
+	}
+
+	if fileLabel == "" {
+		return nil
+	}
+
+	exclude_paths := map[string]bool{"/": true, "/usr": true, "/etc": true}
+	if exclude_paths[path] {
+		return fmt.Errorf("SELinux relabeling of %s is not allowed", path)
+	}
+
+	if shared {
+		c := selinux.NewContext(fileLabel)
+		c["level"] = "s0"
+		fileLabel = c.Get()
+	}
+	if err := selinux.Chcon(path, fileLabel, true); err != nil {
+		return fmt.Errorf("SELinux relabeling of %s is not allowed: %q", path, err)
+	}
+	return nil
+}
+
+// GetPidLabel will return the label of the process running with the specified pid
+func GetPidLabel(pid int) (string, error) {
+	return selinux.Getpidcon(pid)
+}
+
+// Init initialises the labeling system
+func Init() {
+	selinux.SelinuxEnabled()
+}
+
+// ReserveLabel will record the fact that the MCS label has already been used.
+// This will prevent InitLabels from using the MCS label in a newly created
+// container
+func ReserveLabel(label string) error {
+	selinux.ReserveLabel(label)
+	return nil
+}
+
+// UnreserveLabel will remove the reservation of the MCS label.
+// This will allow InitLabels to use the MCS label in a newly created
+// containers
+func UnreserveLabel(label string) error {
+	selinux.FreeLxcContexts(label)
+	return nil
+}
+
+// DupSecOpt takes an process label and returns security options that
+// can be used to set duplicate labels on future container processes
+func DupSecOpt(src string) []string {
+	return selinux.DupSecOpt(src)
+}
+
+// DisableSecOpt returns a security opt that can disable labeling
+// support for future container processes
+func DisableSecOpt() []string {
+	return selinux.DisableSecOpt()
+}
+
+// Validate checks that the label does not include unexpected options
+func Validate(label string) error {
+	if strings.Contains(label, "z") && strings.Contains(label, "Z") {
+		return ErrIncompatibleLabel
+	}
+	return nil
+}
+
+// RelabelNeeded checks whether the user requested a relabel
+func RelabelNeeded(label string) bool {
+	return strings.Contains(label, "z") || strings.Contains(label, "Z")
+}
+
+// IsShared checks that the label includes a "shared" mark
+func IsShared(label string) bool {
+	return strings.Contains(label, "z")
+}

vendor/github.com/opencontainers/runc/libcontainer/selinux/selinux.go

@@ -0,0 +1,499 @@
+// +build linux
+
+package selinux
+
+import (
+	"bufio"
+	"crypto/rand"
+	"encoding/binary"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strconv"
+	"strings"
+	"sync"
+	"syscall"
+
+	"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 = ""
+
+	f, err := os.Open("/proc/self/mountinfo")
+	if err != nil {
+		return selinuxfs
+	}
+	defer f.Close()
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		txt := scanner.Text()
+		// Safe as mountinfo encodes mountpoints with spaces as \040.
+		sepIdx := strings.Index(txt, " - ")
+		if sepIdx == -1 {
+			continue
+		}
+		if !strings.Contains(txt[sepIdx:], "selinuxfs") {
+			continue
+		}
+		fields := strings.Split(txt, " ")
+		if len(fields) < 5 {
+			continue
+		}
+		selinuxfs = fields[4]
+		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--
+	}
+	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
+}
+
+// Chcon changes 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"}
+}

vendor/github.com/opencontainers/runc/libcontainer/system/linux.go

@@ -0,0 +1,143 @@
+// +build linux
+
+package system
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"os/exec"
+	"syscall"
+	"unsafe"
+)
+
+// If arg2 is nonzero, set the "child subreaper" attribute of the
+// calling process; if arg2 is zero, unset the attribute.  When a
+// process is marked as a child subreaper, all of the children
+// that it creates, and their descendants, will be marked as
+// having a subreaper.  In effect, a subreaper fulfills the role
+// of init(1) for its descendant processes.  Upon termination of
+// a process that is orphaned (i.e., its immediate parent has
+// already terminated) and marked as having a subreaper, the
+// nearest still living ancestor subreaper will receive a SIGCHLD
+// signal and be able to wait(2) on the process to discover its
+// termination status.
+const PR_SET_CHILD_SUBREAPER = 36
+
+type ParentDeathSignal int
+
+func (p ParentDeathSignal) Restore() error {
+	if p == 0 {
+		return nil
+	}
+	current, err := GetParentDeathSignal()
+	if err != nil {
+		return err
+	}
+	if p == current {
+		return nil
+	}
+	return p.Set()
+}
+
+func (p ParentDeathSignal) Set() error {
+	return SetParentDeathSignal(uintptr(p))
+}
+
+func Execv(cmd string, args []string, env []string) error {
+	name, err := exec.LookPath(cmd)
+	if err != nil {
+		return err
+	}
+
+	return syscall.Exec(name, args, env)
+}
+
+func Prlimit(pid, resource int, limit syscall.Rlimit) error {
+	_, _, err := syscall.RawSyscall6(syscall.SYS_PRLIMIT64, uintptr(pid), uintptr(resource), uintptr(unsafe.Pointer(&limit)), uintptr(unsafe.Pointer(&limit)), 0, 0)
+	if err != 0 {
+		return err
+	}
+	return nil
+}
+
+func SetParentDeathSignal(sig uintptr) error {
+	if _, _, err := syscall.RawSyscall(syscall.SYS_PRCTL, syscall.PR_SET_PDEATHSIG, sig, 0); err != 0 {
+		return err
+	}
+	return nil
+}
+
+func GetParentDeathSignal() (ParentDeathSignal, error) {
+	var sig int
+	_, _, err := syscall.RawSyscall(syscall.SYS_PRCTL, syscall.PR_GET_PDEATHSIG, uintptr(unsafe.Pointer(&sig)), 0)
+	if err != 0 {
+		return -1, err
+	}
+	return ParentDeathSignal(sig), nil
+}
+
+func SetKeepCaps() error {
+	if _, _, err := syscall.RawSyscall(syscall.SYS_PRCTL, syscall.PR_SET_KEEPCAPS, 1, 0); err != 0 {
+		return err
+	}
+
+	return nil
+}
+
+func ClearKeepCaps() error {
+	if _, _, err := syscall.RawSyscall(syscall.SYS_PRCTL, syscall.PR_SET_KEEPCAPS, 0, 0); err != 0 {
+		return err
+	}
+
+	return nil
+}
+
+func Setctty() error {
+	if _, _, err := syscall.RawSyscall(syscall.SYS_IOCTL, 0, uintptr(syscall.TIOCSCTTY), 0); err != 0 {
+		return err
+	}
+	return nil
+}
+
+// RunningInUserNS detects whether we are currently running in a user namespace.
+// Copied from github.com/lxc/lxd/shared/util.go
+func RunningInUserNS() bool {
+	file, err := os.Open("/proc/self/uid_map")
+	if err != nil {
+		// This kernel-provided file only exists if user namespaces are supported
+		return false
+	}
+	defer file.Close()
+
+	buf := bufio.NewReader(file)
+	l, _, err := buf.ReadLine()
+	if err != nil {
+		return false
+	}
+
+	line := string(l)
+	var a, b, c int64
+	fmt.Sscanf(line, "%d %d %d", &a, &b, &c)
+	/*
+	 * We assume we are in the initial user namespace if we have a full
+	 * range - 4294967295 uids starting at uid 0.
+	 */
+	if a == 0 && b == 0 && c == 4294967295 {
+		return false
+	}
+	return true
+}
+
+// SetSubreaper sets the value i as the subreaper setting for the calling process
+func SetSubreaper(i int) error {
+	return Prctl(PR_SET_CHILD_SUBREAPER, uintptr(i), 0, 0, 0)
+}
+
+func Prctl(option int, arg2, arg3, arg4, arg5 uintptr) (err error) {
+	_, _, e1 := syscall.Syscall6(syscall.SYS_PRCTL, uintptr(option), arg2, arg3, arg4, arg5, 0)
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}

vendor/github.com/opencontainers/runc/libcontainer/system/proc.go

@@ -0,0 +1,27 @@
+package system
+
+import (
+	"io/ioutil"
+	"path/filepath"
+	"strconv"
+	"strings"
+)
+
+// look in /proc to find the process start time so that we can verify
+// that this pid has started after ourself
+func GetProcessStartTime(pid int) (string, error) {
+	data, err := ioutil.ReadFile(filepath.Join("/proc", strconv.Itoa(pid), "stat"))
+	if err != nil {
+		return "", err
+	}
+
+	parts := strings.Split(string(data), " ")
+	// the starttime is located at pos 22
+	// from the man page
+	//
+	// starttime %llu (was %lu before Linux 2.6)
+	// (22)  The  time the process started after system boot.  In kernels before Linux 2.6, this
+	// value was expressed in jiffies.  Since Linux 2.6, the value is expressed in  clock  ticks
+	// (divide by sysconf(_SC_CLK_TCK)).
+	return parts[22-1], nil // starts at 1
+}

vendor/github.com/opencontainers/runc/libcontainer/system/setns_linux.go

@@ -0,0 +1,40 @@
+package system
+
+import (
+	"fmt"
+	"runtime"
+	"syscall"
+)
+
+// Via http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=7b21fddd087678a70ad64afc0f632e0f1071b092
+//
+// We need different setns values for the different platforms and arch
+// We are declaring the macro here because the SETNS syscall does not exist in th stdlib
+var setNsMap = map[string]uintptr{
+	"linux/386":     346,
+	"linux/arm64":   268,
+	"linux/amd64":   308,
+	"linux/arm":     375,
+	"linux/ppc":     350,
+	"linux/ppc64":   350,
+	"linux/ppc64le": 350,
+	"linux/s390x":   339,
+}
+
+var sysSetns = setNsMap[fmt.Sprintf("%s/%s", runtime.GOOS, runtime.GOARCH)]
+
+func SysSetns() uint32 {
+	return uint32(sysSetns)
+}
+
+func Setns(fd uintptr, flags uintptr) error {
+	ns, exists := setNsMap[fmt.Sprintf("%s/%s", runtime.GOOS, runtime.GOARCH)]
+	if !exists {
+		return fmt.Errorf("unsupported platform %s/%s", runtime.GOOS, runtime.GOARCH)
+	}
+	_, _, err := syscall.RawSyscall(ns, fd, flags, 0)
+	if err != 0 {
+		return err
+	}
+	return nil
+}

vendor/github.com/opencontainers/runc/libcontainer/system/syscall_linux_386.go

@@ -0,0 +1,25 @@
+// +build linux,386
+
+package system
+
+import (
+	"syscall"
+)
+
+// Setuid sets the uid of the calling thread to the specified uid.
+func Setuid(uid int) (err error) {
+	_, _, e1 := syscall.RawSyscall(syscall.SYS_SETUID32, uintptr(uid), 0, 0)
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}
+
+// Setgid sets the gid of the calling thread to the specified gid.
+func Setgid(gid int) (err error) {
+	_, _, e1 := syscall.RawSyscall(syscall.SYS_SETGID32, uintptr(gid), 0, 0)
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}

vendor/github.com/opencontainers/runc/libcontainer/system/syscall_linux_64.go

@@ -0,0 +1,25 @@
+// +build linux,arm64 linux,amd64 linux,ppc linux,ppc64 linux,ppc64le linux,s390x
+
+package system
+
+import (
+	"syscall"
+)
+
+// Setuid sets the uid of the calling thread to the specified uid.
+func Setuid(uid int) (err error) {
+	_, _, e1 := syscall.RawSyscall(syscall.SYS_SETUID, uintptr(uid), 0, 0)
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}
+
+// Setgid sets the gid of the calling thread to the specified gid.
+func Setgid(gid int) (err error) {
+	_, _, e1 := syscall.RawSyscall(syscall.SYS_SETGID, uintptr(gid), 0, 0)
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}

vendor/github.com/opencontainers/runc/libcontainer/system/syscall_linux_arm.go

@@ -0,0 +1,25 @@
+// +build linux,arm
+
+package system
+
+import (
+	"syscall"
+)
+
+// Setuid sets the uid of the calling thread to the specified uid.
+func Setuid(uid int) (err error) {
+	_, _, e1 := syscall.RawSyscall(syscall.SYS_SETUID32, uintptr(uid), 0, 0)
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}
+
+// Setgid sets the gid of the calling thread to the specified gid.
+func Setgid(gid int) (err error) {
+	_, _, e1 := syscall.RawSyscall(syscall.SYS_SETGID32, uintptr(gid), 0, 0)
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}

vendor/github.com/opencontainers/runc/libcontainer/system/sysconfig.go

@@ -0,0 +1,12 @@
+// +build cgo,linux cgo,freebsd
+
+package system
+
+/*
+#include <unistd.h>
+*/
+import "C"
+
+func GetClockTicks() int {
+	return int(C.sysconf(C._SC_CLK_TCK))
+}

vendor/github.com/opencontainers/runc/libcontainer/system/sysconfig_notcgo.go

@@ -0,0 +1,15 @@
+// +build !cgo windows
+
+package system
+
+func GetClockTicks() int {
+	// TODO figure out a better alternative for platforms where we're missing cgo
+	//
+	// TODO Windows. This could be implemented using Win32 QueryPerformanceFrequency().
+	// https://msdn.microsoft.com/en-us/library/windows/desktop/ms644905(v=vs.85).aspx
+	//
+	// An example of its usage can be found here.
+	// https://msdn.microsoft.com/en-us/library/windows/desktop/dn553408(v=vs.85).aspx
+
+	return 100
+}

vendor/github.com/opencontainers/runc/libcontainer/system/unsupported.go

@@ -0,0 +1,9 @@
+// +build !linux
+
+package system
+
+// RunningInUserNS is a stub for non-Linux systems
+// Always returns false
+func RunningInUserNS() bool {
+	return false
+}

vendor/github.com/opencontainers/runc/libcontainer/system/xattrs_linux.go

@@ -0,0 +1,99 @@
+package system
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+var _zero uintptr
+
+// Returns the size of xattrs and nil error
+// Requires path, takes allocated []byte or nil as last argument
+func Llistxattr(path string, dest []byte) (size int, err error) {
+	pathBytes, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return -1, err
+	}
+	var newpathBytes unsafe.Pointer
+	if len(dest) > 0 {
+		newpathBytes = unsafe.Pointer(&dest[0])
+	} else {
+		newpathBytes = unsafe.Pointer(&_zero)
+	}
+
+	_size, _, errno := syscall.Syscall6(syscall.SYS_LLISTXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(newpathBytes), uintptr(len(dest)), 0, 0, 0)
+	size = int(_size)
+	if errno != 0 {
+		return -1, errno
+	}
+
+	return size, nil
+}
+
+// Returns a []byte slice if the xattr is set and nil otherwise
+// Requires path and its attribute as arguments
+func Lgetxattr(path string, attr string) ([]byte, error) {
+	var sz int
+	pathBytes, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return nil, err
+	}
+	attrBytes, err := syscall.BytePtrFromString(attr)
+	if err != nil {
+		return nil, err
+	}
+
+	// Start with a 128 length byte array
+	sz = 128
+	dest := make([]byte, sz)
+	destBytes := unsafe.Pointer(&dest[0])
+	_sz, _, errno := syscall.Syscall6(syscall.SYS_LGETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(destBytes), uintptr(len(dest)), 0, 0)
+
+	switch {
+	case errno == syscall.ENODATA:
+		return nil, errno
+	case errno == syscall.ENOTSUP:
+		return nil, errno
+	case errno == syscall.ERANGE:
+		// 128 byte array might just not be good enough,
+		// A dummy buffer is used ``uintptr(0)`` to get real size
+		// of the xattrs on disk
+		_sz, _, errno = syscall.Syscall6(syscall.SYS_LGETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(unsafe.Pointer(nil)), uintptr(0), 0, 0)
+		sz = int(_sz)
+		if sz < 0 {
+			return nil, errno
+		}
+		dest = make([]byte, sz)
+		destBytes := unsafe.Pointer(&dest[0])
+		_sz, _, errno = syscall.Syscall6(syscall.SYS_LGETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(destBytes), uintptr(len(dest)), 0, 0)
+		if errno != 0 {
+			return nil, errno
+		}
+	case errno != 0:
+		return nil, errno
+	}
+	sz = int(_sz)
+	return dest[:sz], nil
+}
+
+func Lsetxattr(path string, attr string, data []byte, flags int) error {
+	pathBytes, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return err
+	}
+	attrBytes, err := syscall.BytePtrFromString(attr)
+	if err != nil {
+		return err
+	}
+	var dataBytes unsafe.Pointer
+	if len(data) > 0 {
+		dataBytes = unsafe.Pointer(&data[0])
+	} else {
+		dataBytes = unsafe.Pointer(&_zero)
+	}
+	_, _, errno := syscall.Syscall6(syscall.SYS_LSETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(dataBytes), uintptr(len(data)), uintptr(flags), 0)
+	if errno != 0 {
+		return errno
+	}
+	return nil
+}

vendor/github.com/opencontainers/runc/libcontainer/user/MAINTAINERS

@@ -0,0 +1,2 @@
+Tianon Gravi <admwiggin@gmail.com> (@tianon)
+Aleksa Sarai <cyphar@cyphar.com> (@cyphar)

vendor/github.com/opencontainers/runc/libcontainer/user/lookup.go

@@ -0,0 +1,110 @@
+package user
+
+import (
+	"errors"
+	"syscall"
+)
+
+var (
+	// The current operating system does not provide the required data for user lookups.
+	ErrUnsupported = errors.New("user lookup: operating system does not provide passwd-formatted data")
+	// No matching entries found in file.
+	ErrNoPasswdEntries = errors.New("no matching entries in passwd file")
+	ErrNoGroupEntries  = errors.New("no matching entries in group file")
+)
+
+func lookupUser(filter func(u User) bool) (User, error) {
+	// Get operating system-specific passwd reader-closer.
+	passwd, err := GetPasswd()
+	if err != nil {
+		return User{}, err
+	}
+	defer passwd.Close()
+
+	// Get the users.
+	users, err := ParsePasswdFilter(passwd, filter)
+	if err != nil {
+		return User{}, err
+	}
+
+	// No user entries found.
+	if len(users) == 0 {
+		return User{}, ErrNoPasswdEntries
+	}
+
+	// Assume the first entry is the "correct" one.
+	return users[0], nil
+}
+
+// CurrentUser looks up the current user by their user id in /etc/passwd. If the
+// user cannot be found (or there is no /etc/passwd file on the filesystem),
+// then CurrentUser returns an error.
+func CurrentUser() (User, error) {
+	return LookupUid(syscall.Getuid())
+}
+
+// LookupUser looks up a user by their username in /etc/passwd. If the user
+// cannot be found (or there is no /etc/passwd file on the filesystem), then
+// LookupUser returns an error.
+func LookupUser(username string) (User, error) {
+	return lookupUser(func(u User) bool {
+		return u.Name == username
+	})
+}
+
+// LookupUid looks up a user by their user id in /etc/passwd. If the user cannot
+// be found (or there is no /etc/passwd file on the filesystem), then LookupId
+// returns an error.
+func LookupUid(uid int) (User, error) {
+	return lookupUser(func(u User) bool {
+		return u.Uid == uid
+	})
+}
+
+func lookupGroup(filter func(g Group) bool) (Group, error) {
+	// Get operating system-specific group reader-closer.
+	group, err := GetGroup()
+	if err != nil {
+		return Group{}, err
+	}
+	defer group.Close()
+
+	// Get the users.
+	groups, err := ParseGroupFilter(group, filter)
+	if err != nil {
+		return Group{}, err
+	}
+
+	// No user entries found.
+	if len(groups) == 0 {
+		return Group{}, ErrNoGroupEntries
+	}
+
+	// Assume the first entry is the "correct" one.
+	return groups[0], nil
+}
+
+// CurrentGroup looks up the current user's group by their primary group id's
+// entry in /etc/passwd. If the group cannot be found (or there is no
+// /etc/group file on the filesystem), then CurrentGroup returns an error.
+func CurrentGroup() (Group, error) {
+	return LookupGid(syscall.Getgid())
+}
+
+// LookupGroup looks up a group by its name in /etc/group. If the group cannot
+// be found (or there is no /etc/group file on the filesystem), then LookupGroup
+// returns an error.
+func LookupGroup(groupname string) (Group, error) {
+	return lookupGroup(func(g Group) bool {
+		return g.Name == groupname
+	})
+}
+
+// LookupGid looks up a group by its group id in /etc/group. If the group cannot
+// be found (or there is no /etc/group file on the filesystem), then LookupGid
+// returns an error.
+func LookupGid(gid int) (Group, error) {
+	return lookupGroup(func(g Group) bool {
+		return g.Gid == gid
+	})
+}

vendor/github.com/opencontainers/runc/libcontainer/user/lookup_unix.go

@@ -0,0 +1,30 @@
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris
+
+package user
+
+import (
+	"io"
+	"os"
+)
+
+// Unix-specific path to the passwd and group formatted files.
+const (
+	unixPasswdPath = "/etc/passwd"
+	unixGroupPath  = "/etc/group"
+)
+
+func GetPasswdPath() (string, error) {
+	return unixPasswdPath, nil
+}
+
+func GetPasswd() (io.ReadCloser, error) {
+	return os.Open(unixPasswdPath)
+}
+
+func GetGroupPath() (string, error) {
+	return unixGroupPath, nil
+}
+
+func GetGroup() (io.ReadCloser, error) {
+	return os.Open(unixGroupPath)
+}

vendor/github.com/opencontainers/runc/libcontainer/user/lookup_unsupported.go

@@ -0,0 +1,21 @@
+// +build !darwin,!dragonfly,!freebsd,!linux,!netbsd,!openbsd,!solaris
+
+package user
+
+import "io"
+
+func GetPasswdPath() (string, error) {
+	return "", ErrUnsupported
+}
+
+func GetPasswd() (io.ReadCloser, error) {
+	return nil, ErrUnsupported
+}
+
+func GetGroupPath() (string, error) {
+	return "", ErrUnsupported
+}
+
+func GetGroup() (io.ReadCloser, error) {
+	return nil, ErrUnsupported
+}

vendor/github.com/opencontainers/runc/libcontainer/user/user.go

@@ -0,0 +1,441 @@
+package user
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+	"strings"
+)
+
+const (
+	minId = 0
+	maxId = 1<<31 - 1 //for 32-bit systems compatibility
+)
+
+var (
+	ErrRange = fmt.Errorf("uids and gids must be in range %d-%d", minId, maxId)
+)
+
+type User struct {
+	Name  string
+	Pass  string
+	Uid   int
+	Gid   int
+	Gecos string
+	Home  string
+	Shell string
+}
+
+type Group struct {
+	Name string
+	Pass string
+	Gid  int
+	List []string
+}
+
+func parseLine(line string, v ...interface{}) {
+	if line == "" {
+		return
+	}
+
+	parts := strings.Split(line, ":")
+	for i, p := range parts {
+		// Ignore cases where we don't have enough fields to populate the arguments.
+		// Some configuration files like to misbehave.
+		if len(v) <= i {
+			break
+		}
+
+		// Use the type of the argument to figure out how to parse it, scanf() style.
+		// This is legit.
+		switch e := v[i].(type) {
+		case *string:
+			*e = p
+		case *int:
+			// "numbers", with conversion errors ignored because of some misbehaving configuration files.
+			*e, _ = strconv.Atoi(p)
+		case *[]string:
+			// Comma-separated lists.
+			if p != "" {
+				*e = strings.Split(p, ",")
+			} else {
+				*e = []string{}
+			}
+		default:
+			// Someone goof'd when writing code using this function. Scream so they can hear us.
+			panic(fmt.Sprintf("parseLine only accepts {*string, *int, *[]string} as arguments! %#v is not a pointer!", e))
+		}
+	}
+}
+
+func ParsePasswdFile(path string) ([]User, error) {
+	passwd, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer passwd.Close()
+	return ParsePasswd(passwd)
+}
+
+func ParsePasswd(passwd io.Reader) ([]User, error) {
+	return ParsePasswdFilter(passwd, nil)
+}
+
+func ParsePasswdFileFilter(path string, filter func(User) bool) ([]User, error) {
+	passwd, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer passwd.Close()
+	return ParsePasswdFilter(passwd, filter)
+}
+
+func ParsePasswdFilter(r io.Reader, filter func(User) bool) ([]User, error) {
+	if r == nil {
+		return nil, fmt.Errorf("nil source for passwd-formatted data")
+	}
+
+	var (
+		s   = bufio.NewScanner(r)
+		out = []User{}
+	)
+
+	for s.Scan() {
+		if err := s.Err(); err != nil {
+			return nil, err
+		}
+
+		line := strings.TrimSpace(s.Text())
+		if line == "" {
+			continue
+		}
+
+		// see: man 5 passwd
+		//  name:password:UID:GID:GECOS:directory:shell
+		// Name:Pass:Uid:Gid:Gecos:Home:Shell
+		//  root:x:0:0:root:/root:/bin/bash
+		//  adm:x:3:4:adm:/var/adm:/bin/false
+		p := User{}
+		parseLine(line, &p.Name, &p.Pass, &p.Uid, &p.Gid, &p.Gecos, &p.Home, &p.Shell)
+
+		if filter == nil || filter(p) {
+			out = append(out, p)
+		}
+	}
+
+	return out, nil
+}
+
+func ParseGroupFile(path string) ([]Group, error) {
+	group, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+
+	defer group.Close()
+	return ParseGroup(group)
+}
+
+func ParseGroup(group io.Reader) ([]Group, error) {
+	return ParseGroupFilter(group, nil)
+}
+
+func ParseGroupFileFilter(path string, filter func(Group) bool) ([]Group, error) {
+	group, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer group.Close()
+	return ParseGroupFilter(group, filter)
+}
+
+func ParseGroupFilter(r io.Reader, filter func(Group) bool) ([]Group, error) {
+	if r == nil {
+		return nil, fmt.Errorf("nil source for group-formatted data")
+	}
+
+	var (
+		s   = bufio.NewScanner(r)
+		out = []Group{}
+	)
+
+	for s.Scan() {
+		if err := s.Err(); err != nil {
+			return nil, err
+		}
+
+		text := s.Text()
+		if text == "" {
+			continue
+		}
+
+		// see: man 5 group
+		//  group_name:password:GID:user_list
+		// Name:Pass:Gid:List
+		//  root:x:0:root
+		//  adm:x:4:root,adm,daemon
+		p := Group{}
+		parseLine(text, &p.Name, &p.Pass, &p.Gid, &p.List)
+
+		if filter == nil || filter(p) {
+			out = append(out, p)
+		}
+	}
+
+	return out, nil
+}
+
+type ExecUser struct {
+	Uid   int
+	Gid   int
+	Sgids []int
+	Home  string
+}
+
+// GetExecUserPath is a wrapper for GetExecUser. It reads data from each of the
+// given file paths and uses that data as the arguments to GetExecUser. If the
+// files cannot be opened for any reason, the error is ignored and a nil
+// io.Reader is passed instead.
+func GetExecUserPath(userSpec string, defaults *ExecUser, passwdPath, groupPath string) (*ExecUser, error) {
+	passwd, err := os.Open(passwdPath)
+	if err != nil {
+		passwd = nil
+	} else {
+		defer passwd.Close()
+	}
+
+	group, err := os.Open(groupPath)
+	if err != nil {
+		group = nil
+	} else {
+		defer group.Close()
+	}
+
+	return GetExecUser(userSpec, defaults, passwd, group)
+}
+
+// GetExecUser parses a user specification string (using the passwd and group
+// readers as sources for /etc/passwd and /etc/group data, respectively). In
+// the case of blank fields or missing data from the sources, the values in
+// defaults is used.
+//
+// GetExecUser will return an error if a user or group literal could not be
+// found in any entry in passwd and group respectively.
+//
+// Examples of valid user specifications are:
+//     * ""
+//     * "user"
+//     * "uid"
+//     * "user:group"
+//     * "uid:gid
+//     * "user:gid"
+//     * "uid:group"
+//
+// It should be noted that if you specify a numeric user or group id, they will
+// not be evaluated as usernames (only the metadata will be filled). So attempting
+// to parse a user with user.Name = "1337" will produce the user with a UID of
+// 1337.
+func GetExecUser(userSpec string, defaults *ExecUser, passwd, group io.Reader) (*ExecUser, error) {
+	if defaults == nil {
+		defaults = new(ExecUser)
+	}
+
+	// Copy over defaults.
+	user := &ExecUser{
+		Uid:   defaults.Uid,
+		Gid:   defaults.Gid,
+		Sgids: defaults.Sgids,
+		Home:  defaults.Home,
+	}
+
+	// Sgids slice *cannot* be nil.
+	if user.Sgids == nil {
+		user.Sgids = []int{}
+	}
+
+	// Allow for userArg to have either "user" syntax, or optionally "user:group" syntax
+	var userArg, groupArg string
+	parseLine(userSpec, &userArg, &groupArg)
+
+	// Convert userArg and groupArg to be numeric, so we don't have to execute
+	// Atoi *twice* for each iteration over lines.
+	uidArg, uidErr := strconv.Atoi(userArg)
+	gidArg, gidErr := strconv.Atoi(groupArg)
+
+	// Find the matching user.
+	users, err := ParsePasswdFilter(passwd, func(u User) bool {
+		if userArg == "" {
+			// Default to current state of the user.
+			return u.Uid == user.Uid
+		}
+
+		if uidErr == nil {
+			// If the userArg is numeric, always treat it as a UID.
+			return uidArg == u.Uid
+		}
+
+		return u.Name == userArg
+	})
+
+	// If we can't find the user, we have to bail.
+	if err != nil && passwd != nil {
+		if userArg == "" {
+			userArg = strconv.Itoa(user.Uid)
+		}
+		return nil, fmt.Errorf("unable to find user %s: %v", userArg, err)
+	}
+
+	var matchedUserName string
+	if len(users) > 0 {
+		// First match wins, even if there's more than one matching entry.
+		matchedUserName = users[0].Name
+		user.Uid = users[0].Uid
+		user.Gid = users[0].Gid
+		user.Home = users[0].Home
+	} else if userArg != "" {
+		// If we can't find a user with the given username, the only other valid
+		// option is if it's a numeric username with no associated entry in passwd.
+
+		if uidErr != nil {
+			// Not numeric.
+			return nil, fmt.Errorf("unable to find user %s: %v", userArg, ErrNoPasswdEntries)
+		}
+		user.Uid = uidArg
+
+		// Must be inside valid uid range.
+		if user.Uid < minId || user.Uid > maxId {
+			return nil, ErrRange
+		}
+
+		// Okay, so it's numeric. We can just roll with this.
+	}
+
+	// On to the groups. If we matched a username, we need to do this because of
+	// the supplementary group IDs.
+	if groupArg != "" || matchedUserName != "" {
+		groups, err := ParseGroupFilter(group, func(g Group) bool {
+			// If the group argument isn't explicit, we'll just search for it.
+			if groupArg == "" {
+				// Check if user is a member of this group.
+				for _, u := range g.List {
+					if u == matchedUserName {
+						return true
+					}
+				}
+				return false
+			}
+
+			if gidErr == nil {
+				// If the groupArg is numeric, always treat it as a GID.
+				return gidArg == g.Gid
+			}
+
+			return g.Name == groupArg
+		})
+		if err != nil && group != nil {
+			return nil, fmt.Errorf("unable to find groups for spec %v: %v", matchedUserName, err)
+		}
+
+		// Only start modifying user.Gid if it is in explicit form.
+		if groupArg != "" {
+			if len(groups) > 0 {
+				// First match wins, even if there's more than one matching entry.
+				user.Gid = groups[0].Gid
+			} else if groupArg != "" {
+				// If we can't find a group with the given name, the only other valid
+				// option is if it's a numeric group name with no associated entry in group.
+
+				if gidErr != nil {
+					// Not numeric.
+					return nil, fmt.Errorf("unable to find group %s: %v", groupArg, ErrNoGroupEntries)
+				}
+				user.Gid = gidArg
+
+				// Must be inside valid gid range.
+				if user.Gid < minId || user.Gid > maxId {
+					return nil, ErrRange
+				}
+
+				// Okay, so it's numeric. We can just roll with this.
+			}
+		} else if len(groups) > 0 {
+			// Supplementary group ids only make sense if in the implicit form.
+			user.Sgids = make([]int, len(groups))
+			for i, group := range groups {
+				user.Sgids[i] = group.Gid
+			}
+		}
+	}
+
+	return user, nil
+}
+
+// GetAdditionalGroups looks up a list of groups by name or group id
+// against the given /etc/group formatted data. If a group name cannot
+// be found, an error will be returned. If a group id cannot be found,
+// or the given group data is nil, the id will be returned as-is
+// provided it is in the legal range.
+func GetAdditionalGroups(additionalGroups []string, group io.Reader) ([]int, error) {
+	var groups = []Group{}
+	if group != nil {
+		var err error
+		groups, err = ParseGroupFilter(group, func(g Group) bool {
+			for _, ag := range additionalGroups {
+				if g.Name == ag || strconv.Itoa(g.Gid) == ag {
+					return true
+				}
+			}
+			return false
+		})
+		if err != nil {
+			return nil, fmt.Errorf("Unable to find additional groups %v: %v", additionalGroups, err)
+		}
+	}
+
+	gidMap := make(map[int]struct{})
+	for _, ag := range additionalGroups {
+		var found bool
+		for _, g := range groups {
+			// if we found a matched group either by name or gid, take the
+			// first matched as correct
+			if g.Name == ag || strconv.Itoa(g.Gid) == ag {
+				if _, ok := gidMap[g.Gid]; !ok {
+					gidMap[g.Gid] = struct{}{}
+					found = true
+					break
+				}
+			}
+		}
+		// we asked for a group but didn't find it. let's check to see
+		// if we wanted a numeric group
+		if !found {
+			gid, err := strconv.Atoi(ag)
+			if err != nil {
+				return nil, fmt.Errorf("Unable to find group %s", ag)
+			}
+			// Ensure gid is inside gid range.
+			if gid < minId || gid > maxId {
+				return nil, ErrRange
+			}
+			gidMap[gid] = struct{}{}
+		}
+	}
+	gids := []int{}
+	for gid := range gidMap {
+		gids = append(gids, gid)
+	}
+	return gids, nil
+}
+
+// GetAdditionalGroupsPath is a wrapper around GetAdditionalGroups
+// that opens the groupPath given and gives it as an argument to
+// GetAdditionalGroups.
+func GetAdditionalGroupsPath(additionalGroups []string, groupPath string) ([]int, error) {
+	group, err := os.Open(groupPath)
+	if err == nil {
+		defer group.Close()
+	}
+	return GetAdditionalGroups(additionalGroups, group)
+}