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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.
//go:build linux
package syscall_test
import (
"bytes"
"flag"
"fmt"
"internal/testenv"
"io"
"os"
"os/exec"
"os/user"
"path"
"path/filepath"
"runtime"
"strconv"
"strings"
"syscall"
"testing"
"unsafe"
)
// whoamiNEWUSER returns a command that runs "whoami" with CLONE_NEWUSER,
// mapping uid and gid 0 to the actual uid and gid of the test.
func whoamiNEWUSER(t *testing.T, uid, gid int, setgroups bool) *exec.Cmd {
t.Helper()
testenv.MustHaveExecPath(t, "whoami")
cmd := testenv.Command(t, "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 TestCloneNEWUSERAndRemap(t *testing.T) {
for _, setgroups := range []bool{false, true} {
setgroups := setgroups
t.Run(fmt.Sprintf("setgroups=%v", setgroups), func(t *testing.T) {
uid := os.Getuid()
gid := os.Getgid()
cmd := whoamiNEWUSER(t, uid, gid, setgroups)
out, err := cmd.CombinedOutput()
t.Logf("%v: %v", cmd, err)
if uid != 0 && setgroups {
t.Logf("as non-root, expected permission error due to unprivileged gid_map")
if !os.IsPermission(err) {
if err == nil {
t.Skipf("unexpected success: probably old kernel without security fix?")
}
if testenv.SyscallIsNotSupported(err) {
t.Skipf("skipping: CLONE_NEWUSER appears to be unsupported")
}
t.Fatalf("got non-permission error") // Already logged above.
}
return
}
if err != nil {
if testenv.SyscallIsNotSupported(err) {
// May be inside a container that disallows CLONE_NEWUSER.
t.Skipf("skipping: CLONE_NEWUSER appears to be unsupported")
}
t.Fatalf("unexpected command failure; output:\n%s", out)
}
sout := strings.TrimSpace(string(out))
want := "root"
if sout != want {
t.Fatalf("whoami = %q; want %q", out, want)
}
})
}
}
func TestEmptyCredGroupsDisableSetgroups(t *testing.T) {
cmd := whoamiNEWUSER(t, os.Getuid(), os.Getgid(), false)
cmd.SysProcAttr.Credential = &syscall.Credential{}
if err := cmd.Run(); err != nil {
if testenv.SyscallIsNotSupported(err) {
t.Skipf("skipping: %v: %v", cmd, err)
}
t.Fatal(err)
}
}
func TestUnshare(t *testing.T) {
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)
}
orig, err := os.ReadFile(path)
if err != nil {
t.Fatal(err)
}
origLines := strings.Split(strings.TrimSpace(string(orig)), "\n")
cmd := testenv.Command(t, "cat", path)
cmd.SysProcAttr = &syscall.SysProcAttr{
Unshareflags: syscall.CLONE_NEWNET,
}
out, err := cmd.CombinedOutput()
if err != nil {
if testenv.SyscallIsNotSupported(err) {
// CLONE_NEWNET does not appear to be supported.
t.Skipf("skipping due to permission error: %v", err)
}
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) {
testenv.MustHaveExecPath(t, "id")
cmd := testenv.Command(t, "id")
cmd.SysProcAttr = &syscall.SysProcAttr{
Credential: &syscall.Credential{
Uid: 0,
Gid: 0,
},
}
out, err := cmd.CombinedOutput()
if err != nil {
if testenv.SyscallIsNotSupported(err) {
t.Skipf("skipping: %v: %v", cmd, err)
}
t.Fatalf("Cmd failed with err %v, output: %s", err, out)
}
strOut := strings.TrimSpace(string(out))
t.Logf("id: %s", strOut)
expected := "uid=0(root) gid=0(root)"
// Just check prefix because some distros reportedly output a
// context parameter; see https://golang.org/issue/16224.
// Alpine does not output groups; see https://golang.org/issue/19938.
if !strings.HasPrefix(strOut, expected) {
t.Errorf("expected prefix: %q", expected)
}
}
func TestGroupCleanupUserNamespace(t *testing.T) {
testenv.MustHaveExecPath(t, "id")
cmd := testenv.Command(t, "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 {
if testenv.SyscallIsNotSupported(err) {
t.Skipf("skipping: %v: %v", cmd, err)
}
t.Fatalf("Cmd failed with err %v, output: %s", err, out)
}
strOut := strings.TrimSpace(string(out))
t.Logf("id: %s", strOut)
// As in TestGroupCleanup, just check prefix.
// The actual groups and contexts seem to vary from one distro to the next.
expected := "uid=0(root) gid=0(root) groups=0(root)"
if !strings.HasPrefix(strOut, expected) {
t.Errorf("expected prefix: %q", expected)
}
}
// Test for https://go.dev/issue/19661: unshare fails because systemd
// has forced / to be shared
func TestUnshareMountNameSpace(t *testing.T) {
testenv.MustHaveExec(t)
if os.Getenv("GO_WANT_HELPER_PROCESS") == "1" {
dir := flag.Args()[0]
err := syscall.Mount("none", dir, "proc", 0, "")
if err != nil {
fmt.Fprintf(os.Stderr, "unshare: mount %v failed: %#v", dir, err)
os.Exit(2)
}
os.Exit(0)
}
exe, err := os.Executable()
if err != nil {
t.Fatal(err)
}
d := t.TempDir()
t.Cleanup(func() {
// If the subprocess fails to unshare the parent directory, force-unmount it
// so that the test can clean it up.
if _, err := os.Stat(d); err == nil {
syscall.Unmount(d, syscall.MNT_FORCE)
}
})
cmd := testenv.Command(t, exe, "-test.run=TestUnshareMountNameSpace", d)
cmd.Env = append(cmd.Environ(), "GO_WANT_HELPER_PROCESS=1")
cmd.SysProcAttr = &syscall.SysProcAttr{Unshareflags: syscall.CLONE_NEWNS}
o, err := cmd.CombinedOutput()
if err != nil {
if testenv.SyscallIsNotSupported(err) {
t.Skipf("skipping: could not start process with CLONE_NEWNS: %v", err)
}
t.Fatalf("unshare failed: %v\n%s", err, o)
}
// How do we tell if the namespace was really unshared? It turns out
// to be simple: just try to remove the directory. If it's still mounted
// on the rm will fail with EBUSY.
if err := os.Remove(d); err != nil {
t.Errorf("rmdir failed on %v: %v", d, err)
}
}
// Test for Issue 20103: unshare fails when chroot is used
func TestUnshareMountNameSpaceChroot(t *testing.T) {
if os.Getenv("GO_WANT_HELPER_PROCESS") == "1" {
dir := flag.Args()[0]
err := syscall.Mount("none", dir, "proc", 0, "")
if err != nil {
fmt.Fprintf(os.Stderr, "unshare: mount %v failed: %#v", dir, err)
os.Exit(2)
}
os.Exit(0)
}
d := t.TempDir()
// Since we are doing a chroot, we need the binary there,
// and it must be statically linked.
testenv.MustHaveGoBuild(t)
x := filepath.Join(d, "syscall.test")
t.Cleanup(func() {
// If the subprocess fails to unshare the parent directory, force-unmount it
// so that the test can clean it up.
if _, err := os.Stat(d); err == nil {
syscall.Unmount(d, syscall.MNT_FORCE)
}
})
cmd := testenv.Command(t, testenv.GoToolPath(t), "test", "-c", "-o", x, "syscall")
cmd.Env = append(cmd.Environ(), "CGO_ENABLED=0")
if o, err := cmd.CombinedOutput(); err != nil {
t.Fatalf("Build of syscall in chroot failed, output %v, err %v", o, err)
}
cmd = testenv.Command(t, "/syscall.test", "-test.run=TestUnshareMountNameSpaceChroot", "/")
cmd.Env = append(cmd.Environ(), "GO_WANT_HELPER_PROCESS=1")
cmd.SysProcAttr = &syscall.SysProcAttr{Chroot: d, Unshareflags: syscall.CLONE_NEWNS}
o, err := cmd.CombinedOutput()
if err != nil {
if testenv.SyscallIsNotSupported(err) {
t.Skipf("skipping: could not start process with CLONE_NEWNS and Chroot %q: %v", d, err)
}
t.Fatalf("unshare failed: %v\n%s", err, o)
}
// How do we tell if the namespace was really unshared? It turns out
// to be simple: just try to remove the executable. If it's still mounted
// on, the rm will fail.
if err := os.Remove(x); err != nil {
t.Errorf("rm failed on %v: %v", x, err)
}
if err := os.Remove(d); err != nil {
t.Errorf("rmdir failed on %v: %v", d, err)
}
}
// Test for Issue 29789: unshare fails when uid/gid mapping is specified
func TestUnshareUidGidMapping(t *testing.T) {
if os.Getenv("GO_WANT_HELPER_PROCESS") == "1" {
defer os.Exit(0)
if err := syscall.Chroot(os.TempDir()); err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(2)
}
}
if os.Getuid() == 0 {
t.Skip("test exercises unprivileged user namespace, fails with privileges")
}
testenv.MustHaveExec(t)
exe, err := os.Executable()
if err != nil {
t.Fatal(err)
}
cmd := testenv.Command(t, exe, "-test.run=TestUnshareUidGidMapping")
cmd.Env = append(cmd.Environ(), "GO_WANT_HELPER_PROCESS=1")
cmd.SysProcAttr = &syscall.SysProcAttr{
Unshareflags: syscall.CLONE_NEWNS | syscall.CLONE_NEWUSER,
GidMappingsEnableSetgroups: false,
UidMappings: []syscall.SysProcIDMap{
{
ContainerID: 0,
HostID: syscall.Getuid(),
Size: 1,
},
},
GidMappings: []syscall.SysProcIDMap{
{
ContainerID: 0,
HostID: syscall.Getgid(),
Size: 1,
},
},
}
out, err := cmd.CombinedOutput()
if err != nil {
if testenv.SyscallIsNotSupported(err) {
t.Skipf("skipping: could not start process with CLONE_NEWNS and CLONE_NEWUSER: %v", err)
}
t.Fatalf("Cmd failed with err %v, output: %s", err, out)
}
}
func prepareCgroupFD(t *testing.T) (int, string) {
t.Helper()
const O_PATH = 0x200000 // Same for all architectures, but for some reason not defined in syscall for 386||amd64.
// Requires cgroup v2.
const prefix = "/sys/fs/cgroup"
selfCg, err := os.ReadFile("/proc/self/cgroup")
if err != nil {
if os.IsNotExist(err) || os.IsPermission(err) {
t.Skip(err)
}
t.Fatal(err)
}
// Expect a single line like this:
// 0::/user.slice/user-1000.slice/user@1000.service/app.slice/vte-spawn-891992a2-efbb-4f28-aedb-b24f9e706770.scope
// Otherwise it's either cgroup v1 or a hybrid hierarchy.
if bytes.Count(selfCg, []byte("\n")) > 1 {
t.Skip("cgroup v2 not available")
}
cg := bytes.TrimPrefix(selfCg, []byte("0::"))
if len(cg) == len(selfCg) { // No prefix found.
t.Skipf("cgroup v2 not available (/proc/self/cgroup contents: %q)", selfCg)
}
// Need clone3 with CLONE_INTO_CGROUP support.
_, err = syscall.ForkExec("non-existent binary", nil, &syscall.ProcAttr{
Sys: &syscall.SysProcAttr{
UseCgroupFD: true,
CgroupFD: -1,
},
})
if testenv.SyscallIsNotSupported(err) {
t.Skipf("clone3 with CLONE_INTO_CGROUP not available: %v", err)
}
// Need an ability to create a sub-cgroup.
subCgroup, err := os.MkdirTemp(prefix+string(bytes.TrimSpace(cg)), "subcg-")
if err != nil {
// ErrPermission or EROFS (#57262) when running in an unprivileged container.
// ErrNotExist when cgroupfs is not mounted in chroot/schroot.
if os.IsNotExist(err) || testenv.SyscallIsNotSupported(err) {
t.Skipf("skipping: %v", err)
}
t.Fatal(err)
}
t.Cleanup(func() { syscall.Rmdir(subCgroup) })
cgroupFD, err := syscall.Open(subCgroup, O_PATH, 0)
if err != nil {
t.Fatal(&os.PathError{Op: "open", Path: subCgroup, Err: err})
}
t.Cleanup(func() { syscall.Close(cgroupFD) })
return cgroupFD, "/" + path.Base(subCgroup)
}
func TestUseCgroupFD(t *testing.T) {
testenv.MustHaveExec(t)
exe, err := os.Executable()
if err != nil {
t.Fatal(err)
}
fd, suffix := prepareCgroupFD(t)
cmd := testenv.Command(t, exe, "-test.run=TestUseCgroupFDHelper")
cmd.Env = append(cmd.Environ(), "GO_WANT_HELPER_PROCESS=1")
cmd.SysProcAttr = &syscall.SysProcAttr{
UseCgroupFD: true,
CgroupFD: fd,
}
out, err := cmd.CombinedOutput()
if err != nil {
t.Fatalf("Cmd failed with err %v, output: %s", err, out)
}
// NB: this wouldn't work with cgroupns.
if !bytes.HasSuffix(bytes.TrimSpace(out), []byte(suffix)) {
t.Fatalf("got: %q, want: a line that ends with %q", out, suffix)
}
}
func TestUseCgroupFDHelper(*testing.T) {
if os.Getenv("GO_WANT_HELPER_PROCESS") != "1" {
return
}
defer os.Exit(0)
// Read and print own cgroup path.
selfCg, err := os.ReadFile("/proc/self/cgroup")
if err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(2)
}
fmt.Print(string(selfCg))
}
func TestCloneTimeNamespace(t *testing.T) {
testenv.MustHaveExec(t)
if os.Getenv("GO_WANT_HELPER_PROCESS") == "1" {
timens, err := os.Readlink("/proc/self/ns/time")
if err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(2)
}
fmt.Print(string(timens))
os.Exit(0)
}
exe, err := os.Executable()
if err != nil {
t.Fatal(err)
}
cmd := testenv.Command(t, exe, "-test.run=TestCloneTimeNamespace")
cmd.Env = append(cmd.Environ(), "GO_WANT_HELPER_PROCESS=1")
cmd.SysProcAttr = &syscall.SysProcAttr{
Cloneflags: syscall.CLONE_NEWTIME,
}
out, err := cmd.CombinedOutput()
if err != nil {
if testenv.SyscallIsNotSupported(err) {
// CLONE_NEWTIME does not appear to be supported.
t.Skipf("skipping, CLONE_NEWTIME not supported: %v", err)
}
t.Fatalf("Cmd failed with err %v, output: %s", err, out)
}
// Inode number of the time namespaces should be different.
// Based on https://man7.org/linux/man-pages/man7/time_namespaces.7.html#EXAMPLES
timens, err := os.Readlink("/proc/self/ns/time")
if err != nil {
t.Fatal(err)
}
parentTimeNS := string(timens)
childTimeNS := string(out)
if childTimeNS == parentTimeNS {
t.Fatalf("expected child time namespace to be different from parent time namespace: %s", parentTimeNS)
}
}
type capHeader struct {
version uint32
pid int32
}
type capData struct {
effective uint32
permitted uint32
inheritable uint32
}
const CAP_SYS_TIME = 25
const CAP_SYSLOG = 34
type caps struct {
hdr capHeader
data [2]capData
}
func getCaps() (caps, error) {
var c caps
// Get capability version
if _, _, errno := syscall.Syscall(syscall.SYS_CAPGET, uintptr(unsafe.Pointer(&c.hdr)), uintptr(unsafe.Pointer(nil)), 0); errno != 0 {
return c, fmt.Errorf("SYS_CAPGET: %v", errno)
}
// Get current capabilities
if _, _, errno := syscall.Syscall(syscall.SYS_CAPGET, uintptr(unsafe.Pointer(&c.hdr)), uintptr(unsafe.Pointer(&c.data[0])), 0); errno != 0 {
return c, fmt.Errorf("SYS_CAPGET: %v", errno)
}
return c, nil
}
func TestAmbientCaps(t *testing.T) {
testAmbientCaps(t, false)
}
func TestAmbientCapsUserns(t *testing.T) {
testAmbientCaps(t, true)
}
func testAmbientCaps(t *testing.T, userns bool) {
if os.Getenv("GO_WANT_HELPER_PROCESS") == "1" {
caps, err := getCaps()
if err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(2)
}
if caps.data[0].effective&(1<<uint(CAP_SYS_TIME)) == 0 {
fmt.Fprintln(os.Stderr, "CAP_SYS_TIME unexpectedly not in the effective capability mask")
os.Exit(2)
}
if caps.data[1].effective&(1<<uint(CAP_SYSLOG&31)) == 0 {
fmt.Fprintln(os.Stderr, "CAP_SYSLOG unexpectedly not in the effective capability mask")
os.Exit(2)
}
os.Exit(0)
}
// skip on android, due to lack of lookup support
if runtime.GOOS == "android" {
t.Skip("skipping test on android; see Issue 27327")
}
u, err := user.Lookup("nobody")
if err != nil {
t.Fatal(err)
}
uid, err := strconv.ParseInt(u.Uid, 0, 32)
if err != nil {
t.Fatal(err)
}
gid, err := strconv.ParseInt(u.Gid, 0, 32)
if err != nil {
t.Fatal(err)
}
// Copy the test binary to a temporary location which is readable by nobody.
f, err := os.CreateTemp("", "gotest")
if err != nil {
t.Fatal(err)
}
t.Cleanup(func() {
f.Close()
os.Remove(f.Name())
})
testenv.MustHaveExec(t)
exe, err := os.Executable()
if err != nil {
t.Fatal(err)
}
e, err := os.Open(exe)
if err != nil {
t.Fatal(err)
}
defer e.Close()
if _, err := io.Copy(f, e); err != nil {
t.Fatal(err)
}
if err := f.Chmod(0755); err != nil {
t.Fatal(err)
}
if err := f.Close(); err != nil {
t.Fatal(err)
}
cmd := testenv.Command(t, f.Name(), "-test.run="+t.Name())
cmd.Env = append(cmd.Environ(), "GO_WANT_HELPER_PROCESS=1")
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
cmd.SysProcAttr = &syscall.SysProcAttr{
Credential: &syscall.Credential{
Uid: uint32(uid),
Gid: uint32(gid),
},
AmbientCaps: []uintptr{CAP_SYS_TIME, CAP_SYSLOG},
}
if userns {
cmd.SysProcAttr.Cloneflags = syscall.CLONE_NEWUSER
const nobody = 65534
uid := os.Getuid()
gid := os.Getgid()
cmd.SysProcAttr.UidMappings = []syscall.SysProcIDMap{{
ContainerID: int(nobody),
HostID: int(uid),
Size: int(1),
}}
cmd.SysProcAttr.GidMappings = []syscall.SysProcIDMap{{
ContainerID: int(nobody),
HostID: int(gid),
Size: int(1),
}}
// Set credentials to run as user and group nobody.
cmd.SysProcAttr.Credential = &syscall.Credential{
Uid: nobody,
Gid: nobody,
}
}
if err := cmd.Run(); err != nil {
if testenv.SyscallIsNotSupported(err) {
t.Skipf("skipping: %v: %v", cmd, err)
}
t.Fatal(err.Error())
}
}