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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build linux
package syscall_test
import (
"io/ioutil"
"os"
"os/exec"
"strings"
"syscall"
"testing"
)
// Check if we are in a chroot by checking if the inode of / is
// different from 2 (there is no better test available to non-root on
// linux).
func isChrooted(t *testing.T) bool {
root, err := os.Stat("/")
if err != nil {
t.Fatalf("cannot stat /: %v", err)
}
return root.Sys().(*syscall.Stat_t).Ino != 2
}
func checkUserNS(t *testing.T) {
if _, err := os.Stat("/proc/self/ns/user"); err != nil {
if os.IsNotExist(err) {
t.Skip("kernel doesn't support user namespaces")
}
if os.IsPermission(err) {
t.Skip("unable to test user namespaces due to permissions")
}
t.Fatalf("Failed to stat /proc/self/ns/user: %v", err)
}
if isChrooted(t) {
// create_user_ns in the kernel (see
// https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/kernel/user_namespace.c)
// forbids the creation of user namespaces when chrooted.
t.Skip("cannot create user namespaces when chrooted")
}
// On some systems, there is a sysctl setting.
if os.Getuid() != 0 {
data, errRead := ioutil.ReadFile("/proc/sys/kernel/unprivileged_userns_clone")
if errRead == nil && data[0] == '0' {
t.Skip("kernel prohibits user namespace in unprivileged process")
}
}
// When running under the Go continuous build, skip tests for
// now when under Kubernetes. (where things are root but not quite)
// Both of these are our own environment variables.
// See Issue 12815.
if os.Getenv("GO_BUILDER_NAME") != "" && os.Getenv("IN_KUBERNETES") == "1" {
t.Skip("skipping test on Kubernetes-based builders; see Issue 12815")
}
}
func whoamiCmd(t *testing.T, uid, gid int, setgroups bool) *exec.Cmd {
checkUserNS(t)
cmd := exec.Command("whoami")
cmd.SysProcAttr = &syscall.SysProcAttr{
Cloneflags: syscall.CLONE_NEWUSER,
UidMappings: []syscall.SysProcIDMap{
{ContainerID: 0, HostID: uid, Size: 1},
},
GidMappings: []syscall.SysProcIDMap{
{ContainerID: 0, HostID: gid, Size: 1},
},
GidMappingsEnableSetgroups: setgroups,
}
return cmd
}
func testNEWUSERRemap(t *testing.T, uid, gid int, setgroups bool) {
cmd := whoamiCmd(t, uid, gid, setgroups)
out, err := cmd.CombinedOutput()
if err != nil {
t.Fatalf("Cmd failed with err %v, output: %s", err, out)
}
sout := strings.TrimSpace(string(out))
want := "root"
if sout != want {
t.Fatalf("whoami = %q; want %q", out, want)
}
}
func TestCloneNEWUSERAndRemapRootDisableSetgroups(t *testing.T) {
if os.Getuid() != 0 {
t.Skip("skipping root only test")
}
testNEWUSERRemap(t, 0, 0, false)
}
func TestCloneNEWUSERAndRemapRootEnableSetgroups(t *testing.T) {
if os.Getuid() != 0 {
t.Skip("skipping root only test")
}
testNEWUSERRemap(t, 0, 0, false)
}
func TestCloneNEWUSERAndRemapNoRootDisableSetgroups(t *testing.T) {
if os.Getuid() == 0 {
t.Skip("skipping unprivileged user only test")
}
testNEWUSERRemap(t, os.Getuid(), os.Getgid(), false)
}
func TestCloneNEWUSERAndRemapNoRootSetgroupsEnableSetgroups(t *testing.T) {
if os.Getuid() == 0 {
t.Skip("skipping unprivileged user only test")
}
cmd := whoamiCmd(t, os.Getuid(), os.Getgid(), true)
err := cmd.Run()
if err == nil {
t.Skip("probably old kernel without security fix")
}
if !os.IsPermission(err) {
t.Fatalf("Unprivileged gid_map rewriting with GidMappingsEnableSetgroups must fail")
}
}
func TestEmptyCredGroupsDisableSetgroups(t *testing.T) {
cmd := whoamiCmd(t, os.Getuid(), os.Getgid(), false)
cmd.SysProcAttr.Credential = &syscall.Credential{}
if err := cmd.Run(); err != nil {
t.Fatal(err)
}
}
func TestUnshare(t *testing.T) {
// Make sure we are running as root so we have permissions to use unshare
// and create a network namespace.
if os.Getuid() != 0 {
t.Skip("kernel prohibits unshare in unprivileged process, unless using user namespace")
}
// When running under the Go continuous build, skip tests for
// now when under Kubernetes. (where things are root but not quite)
// Both of these are our own environment variables.
// See Issue 12815.
if os.Getenv("GO_BUILDER_NAME") != "" && os.Getenv("IN_KUBERNETES") == "1" {
t.Skip("skipping test on Kubernetes-based builders; see Issue 12815")
}
path := "/proc/net/dev"
if _, err := os.Stat(path); err != nil {
if os.IsNotExist(err) {
t.Skip("kernel doesn't support proc filesystem")
}
if os.IsPermission(err) {
t.Skip("unable to test proc filesystem due to permissions")
}
t.Fatal(err)
}
if _, err := os.Stat("/proc/self/ns/net"); err != nil {
if os.IsNotExist(err) {
t.Skip("kernel doesn't support net namespace")
}
t.Fatal(err)
}
orig, err := ioutil.ReadFile(path)
if err != nil {
t.Fatal(err)
}
origLines := strings.Split(strings.TrimSpace(string(orig)), "\n")
cmd := exec.Command("cat", path)
cmd.SysProcAttr = &syscall.SysProcAttr{
Unshareflags: syscall.CLONE_NEWNET,
}
out, err := cmd.CombinedOutput()
if err != nil {
t.Fatalf("Cmd failed with err %v, output: %s", err, out)
}
// Check there is only the local network interface
sout := strings.TrimSpace(string(out))
if !strings.Contains(sout, "lo:") {
t.Fatalf("Expected lo network interface to exist, got %s", sout)
}
lines := strings.Split(sout, "\n")
if len(lines) >= len(origLines) {
t.Fatalf("Got %d lines of output, want <%d", len(lines), len(origLines))
}
}
func TestGroupCleanup(t *testing.T) {
if os.Getuid() != 0 {
t.Skip("we need root for credential")
}
cmd := exec.Command("id")
cmd.SysProcAttr = &syscall.SysProcAttr{
Credential: &syscall.Credential{
Uid: 0,
Gid: 0,
},
}
out, err := cmd.CombinedOutput()
if err != nil {
t.Fatalf("Cmd failed with err %v, output: %s", err, out)
}
strOut := strings.TrimSpace(string(out))
expected := "uid=0(root) gid=0(root) groups=0(root)"
// Just check prefix because some distros reportedly output a
// context parameter; see https://golang.org/issue/16224.
if !strings.HasPrefix(strOut, expected) {
t.Errorf("id command output: %q, expected prefix: %q", strOut, expected)
}
}
func TestGroupCleanupUserNamespace(t *testing.T) {
if os.Getuid() != 0 {
t.Skip("we need root for credential")
}
checkUserNS(t)
cmd := exec.Command("id")
uid, gid := os.Getuid(), os.Getgid()
cmd.SysProcAttr = &syscall.SysProcAttr{
Cloneflags: syscall.CLONE_NEWUSER,
Credential: &syscall.Credential{
Uid: uint32(uid),
Gid: uint32(gid),
},
UidMappings: []syscall.SysProcIDMap{
{ContainerID: 0, HostID: uid, Size: 1},
},
GidMappings: []syscall.SysProcIDMap{
{ContainerID: 0, HostID: gid, Size: 1},
},
}
out, err := cmd.CombinedOutput()
if err != nil {
t.Fatalf("Cmd failed with err %v, output: %s", err, out)
}
strOut := strings.TrimSpace(string(out))
// Strings we've seen in the wild.
expected := []string{
"uid=0(root) gid=0(root) groups=0(root)",
"uid=0(root) gid=0(root) groups=0(root),65534(nobody)",
"uid=0(root) gid=0(root) groups=0(root),65534(nogroup)",
"uid=0(root) gid=0(root) groups=0(root),65534",
}
for _, e := range expected {
if strOut == e {
return
}
}
t.Errorf("id command output: %q, expected one of %q", strOut, expected)
}
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