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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.
package syscall_test
import (
"fmt"
"io"
"io/fs"
"os"
"os/exec"
"path/filepath"
"runtime"
"sort"
"strconv"
"strings"
"sync"
"syscall"
"testing"
"unsafe"
)
// chtmpdir changes the working directory to a new temporary directory and
// provides a cleanup function. Used when PWD is read-only.
func chtmpdir(t *testing.T) func() {
oldwd, err := os.Getwd()
if err != nil {
t.Fatalf("chtmpdir: %v", err)
}
d, err := os.MkdirTemp("", "test")
if err != nil {
t.Fatalf("chtmpdir: %v", err)
}
if err := os.Chdir(d); err != nil {
t.Fatalf("chtmpdir: %v", err)
}
return func() {
if err := os.Chdir(oldwd); err != nil {
t.Fatalf("chtmpdir: %v", err)
}
os.RemoveAll(d)
}
}
func touch(t *testing.T, name string) {
f, err := os.Create(name)
if err != nil {
t.Fatal(err)
}
if err := f.Close(); err != nil {
t.Fatal(err)
}
}
const (
_AT_SYMLINK_NOFOLLOW = 0x100
_AT_FDCWD = -0x64
_AT_EACCESS = 0x200
_F_OK = 0
_R_OK = 4
)
func TestFaccessat(t *testing.T) {
defer chtmpdir(t)()
touch(t, "file1")
err := syscall.Faccessat(_AT_FDCWD, "file1", _R_OK, 0)
if err != nil {
t.Errorf("Faccessat: unexpected error: %v", err)
}
err = syscall.Faccessat(_AT_FDCWD, "file1", _R_OK, 2)
if err != syscall.EINVAL {
t.Errorf("Faccessat: unexpected error: %v, want EINVAL", err)
}
err = syscall.Faccessat(_AT_FDCWD, "file1", _R_OK, _AT_EACCESS)
if err != nil {
t.Errorf("Faccessat: unexpected error: %v", err)
}
err = os.Symlink("file1", "symlink1")
if err != nil {
t.Fatal(err)
}
err = syscall.Faccessat(_AT_FDCWD, "symlink1", _R_OK, _AT_SYMLINK_NOFOLLOW)
if err != nil {
t.Errorf("Faccessat SYMLINK_NOFOLLOW: unexpected error %v", err)
}
// We can't really test _AT_SYMLINK_NOFOLLOW, because there
// doesn't seem to be any way to change the mode of a symlink.
// We don't test _AT_EACCESS because such tests are only
// meaningful if run as root.
err = syscall.Fchmodat(_AT_FDCWD, "file1", 0, 0)
if err != nil {
t.Errorf("Fchmodat: unexpected error %v", err)
}
err = syscall.Faccessat(_AT_FDCWD, "file1", _F_OK, _AT_SYMLINK_NOFOLLOW)
if err != nil {
t.Errorf("Faccessat: unexpected error: %v", err)
}
err = syscall.Faccessat(_AT_FDCWD, "file1", _R_OK, _AT_SYMLINK_NOFOLLOW)
if err != syscall.EACCES {
if syscall.Getuid() != 0 {
t.Errorf("Faccessat: unexpected error: %v, want EACCES", err)
}
}
}
func TestFchmodat(t *testing.T) {
defer chtmpdir(t)()
touch(t, "file1")
os.Symlink("file1", "symlink1")
err := syscall.Fchmodat(_AT_FDCWD, "symlink1", 0444, 0)
if err != nil {
t.Fatalf("Fchmodat: unexpected error: %v", err)
}
fi, err := os.Stat("file1")
if err != nil {
t.Fatal(err)
}
if fi.Mode() != 0444 {
t.Errorf("Fchmodat: failed to change mode: expected %v, got %v", 0444, fi.Mode())
}
err = syscall.Fchmodat(_AT_FDCWD, "symlink1", 0444, _AT_SYMLINK_NOFOLLOW)
if err != syscall.EOPNOTSUPP {
t.Fatalf("Fchmodat: unexpected error: %v, expected EOPNOTSUPP", err)
}
}
func TestMain(m *testing.M) {
if os.Getenv("GO_DEATHSIG_PARENT") == "1" {
deathSignalParent()
} else if os.Getenv("GO_DEATHSIG_CHILD") == "1" {
deathSignalChild()
} else if os.Getenv("GO_SYSCALL_NOERROR") == "1" {
syscallNoError()
}
os.Exit(m.Run())
}
func TestParseNetlinkMessage(t *testing.T) {
for i, b := range [][]byte{
{103, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 2, 11, 0, 1, 0, 0, 0, 0, 5, 8, 0, 3,
0, 8, 0, 6, 0, 0, 0, 0, 1, 63, 0, 10, 0, 69, 16, 0, 59, 39, 82, 64, 0, 64, 6, 21, 89, 127, 0, 0,
1, 127, 0, 0, 1, 230, 228, 31, 144, 32, 186, 155, 211, 185, 151, 209, 179, 128, 24, 1, 86,
53, 119, 0, 0, 1, 1, 8, 10, 0, 17, 234, 12, 0, 17, 189, 126, 107, 106, 108, 107, 106, 13, 10,
},
{106, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 2, 11, 0, 1, 0, 0, 0, 0, 3, 8, 0, 3,
0, 8, 0, 6, 0, 0, 0, 0, 1, 66, 0, 10, 0, 69, 0, 0, 62, 230, 255, 64, 0, 64, 6, 85, 184, 127, 0, 0,
1, 127, 0, 0, 1, 237, 206, 31, 144, 73, 197, 128, 65, 250, 60, 192, 97, 128, 24, 1, 86, 253, 21, 0,
0, 1, 1, 8, 10, 0, 51, 106, 89, 0, 51, 102, 198, 108, 104, 106, 108, 107, 104, 108, 107, 104, 10,
},
{102, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 2, 11, 0, 1, 0, 0, 0, 0, 1, 8, 0, 3, 0,
8, 0, 6, 0, 0, 0, 0, 1, 62, 0, 10, 0, 69, 0, 0, 58, 231, 2, 64, 0, 64, 6, 85, 185, 127, 0, 0, 1, 127,
0, 0, 1, 237, 206, 31, 144, 73, 197, 128, 86, 250, 60, 192, 97, 128, 24, 1, 86, 104, 64, 0, 0, 1, 1, 8,
10, 0, 52, 198, 200, 0, 51, 135, 232, 101, 115, 97, 103, 103, 10,
},
} {
m, err := syscall.ParseNetlinkMessage(b)
if err != syscall.EINVAL {
t.Errorf("#%d: got %v; want EINVAL", i, err)
}
if m != nil {
t.Errorf("#%d: got %v; want nil", i, m)
}
}
}
func TestSyscallNoError(t *testing.T) {
// On Linux there are currently no syscalls which don't fail and return
// a value larger than 0xfffffffffffff001 so we could test RawSyscall
// vs. RawSyscallNoError on 64bit architectures.
if unsafe.Sizeof(uintptr(0)) != 4 {
t.Skip("skipping on non-32bit architecture")
}
// See https://golang.org/issue/35422
// On MIPS, Linux returns whether the syscall had an error in a separate
// register (R7), not using a negative return value as on other
// architectures.
if runtime.GOARCH == "mips" || runtime.GOARCH == "mipsle" {
t.Skipf("skipping on %s", runtime.GOARCH)
}
if os.Getuid() != 0 {
t.Skip("skipping root only test")
}
if runtime.GOOS == "android" {
t.Skip("skipping on rooted android, see issue 27364")
}
// Copy the test binary to a location that a non-root user can read/execute
// after we drop privileges
tempDir, err := os.MkdirTemp("", "TestSyscallNoError")
if err != nil {
t.Fatalf("cannot create temporary directory: %v", err)
}
defer os.RemoveAll(tempDir)
os.Chmod(tempDir, 0755)
tmpBinary := filepath.Join(tempDir, filepath.Base(os.Args[0]))
src, err := os.Open(os.Args[0])
if err != nil {
t.Fatalf("cannot open binary %q, %v", os.Args[0], err)
}
defer src.Close()
dst, err := os.OpenFile(tmpBinary, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0755)
if err != nil {
t.Fatalf("cannot create temporary binary %q, %v", tmpBinary, err)
}
if _, err := io.Copy(dst, src); err != nil {
t.Fatalf("failed to copy test binary to %q, %v", tmpBinary, err)
}
err = dst.Close()
if err != nil {
t.Fatalf("failed to close test binary %q, %v", tmpBinary, err)
}
uid := uint32(0xfffffffe)
err = os.Chown(tmpBinary, int(uid), -1)
if err != nil {
t.Fatalf("failed to chown test binary %q, %v", tmpBinary, err)
}
err = os.Chmod(tmpBinary, 0755|fs.ModeSetuid)
if err != nil {
t.Fatalf("failed to set setuid bit on test binary %q, %v", tmpBinary, err)
}
cmd := exec.Command(tmpBinary)
cmd.Env = append(os.Environ(), "GO_SYSCALL_NOERROR=1")
out, err := cmd.CombinedOutput()
if err != nil {
t.Fatalf("failed to start first child process: %v", err)
}
got := strings.TrimSpace(string(out))
want := strconv.FormatUint(uint64(uid)+1, 10) + " / " +
strconv.FormatUint(uint64(-uid), 10) + " / " +
strconv.FormatUint(uint64(uid), 10)
if got != want {
if filesystemIsNoSUID(tmpBinary) {
t.Skip("skipping test when temp dir is mounted nosuid")
}
// formatted so the values are aligned for easier comparison
t.Errorf("expected %s,\ngot %s", want, got)
}
}
// filesystemIsNoSUID reports whether the filesystem for the given
// path is mounted nosuid.
func filesystemIsNoSUID(path string) bool {
var st syscall.Statfs_t
if syscall.Statfs(path, &st) != nil {
return false
}
return st.Flags&syscall.MS_NOSUID != 0
}
func syscallNoError() {
// Test that the return value from SYS_GETEUID32 (which cannot fail)
// doesn't get treated as an error (see https://golang.org/issue/22924)
euid1, _, e := syscall.RawSyscall(syscall.Sys_GETEUID, 0, 0, 0)
euid2, _ := syscall.RawSyscallNoError(syscall.Sys_GETEUID, 0, 0, 0)
fmt.Println(uintptr(euid1), "/", int(e), "/", uintptr(euid2))
os.Exit(0)
}
// reference uapi/linux/prctl.h
const (
PR_GET_KEEPCAPS uintptr = 7
PR_SET_KEEPCAPS = 8
)
// TestAllThreadsSyscall tests that the go runtime can perform
// syscalls that execute on all OSThreads - with which to support
// POSIX semantics for security state changes.
func TestAllThreadsSyscall(t *testing.T) {
if _, _, err := syscall.AllThreadsSyscall(syscall.SYS_PRCTL, PR_SET_KEEPCAPS, 0, 0); err == syscall.ENOTSUP {
t.Skip("AllThreadsSyscall disabled with cgo")
}
fns := []struct {
label string
fn func(uintptr) error
}{
{
label: "prctl<3-args>",
fn: func(v uintptr) error {
_, _, e := syscall.AllThreadsSyscall(syscall.SYS_PRCTL, PR_SET_KEEPCAPS, v, 0)
if e != 0 {
return e
}
return nil
},
},
{
label: "prctl<6-args>",
fn: func(v uintptr) error {
_, _, e := syscall.AllThreadsSyscall6(syscall.SYS_PRCTL, PR_SET_KEEPCAPS, v, 0, 0, 0, 0)
if e != 0 {
return e
}
return nil
},
},
}
waiter := func(q <-chan uintptr, r chan<- uintptr, once bool) {
for x := range q {
runtime.LockOSThread()
v, _, e := syscall.Syscall(syscall.SYS_PRCTL, PR_GET_KEEPCAPS, 0, 0)
if e != 0 {
t.Errorf("tid=%d prctl(PR_GET_KEEPCAPS) failed: %v", syscall.Gettid(), e)
} else if x != v {
t.Errorf("tid=%d prctl(PR_GET_KEEPCAPS) mismatch: got=%d want=%d", syscall.Gettid(), v, x)
}
r <- v
if once {
break
}
runtime.UnlockOSThread()
}
}
// launches per fns member.
const launches = 11
question := make(chan uintptr)
response := make(chan uintptr)
defer close(question)
routines := 0
for i, v := range fns {
for j := 0; j < launches; j++ {
// Add another goroutine - the closest thing
// we can do to encourage more OS thread
// creation - while the test is running. The
// actual thread creation may or may not be
// needed, based on the number of available
// unlocked OS threads at the time waiter
// calls runtime.LockOSThread(), but the goal
// of doing this every time through the loop
// is to race thread creation with v.fn(want)
// being executed. Via the once boolean we
// also encourage one in 5 waiters to return
// locked after participating in only one
// question response sequence. This allows the
// test to race thread destruction too.
once := routines%5 == 4
go waiter(question, response, once)
// Keep a count of how many goroutines are
// going to participate in the
// question/response test. This will count up
// towards 2*launches minus the count of
// routines that have been invoked with
// once=true.
routines++
// Decide what value we want to set the
// process-shared KEEPCAPS. Note, there is
// an explicit repeat of 0 when we change the
// variant of the syscall being used.
want := uintptr(j & 1)
// Invoke the AllThreadsSyscall* variant.
if err := v.fn(want); err != nil {
t.Errorf("[%d,%d] %s(PR_SET_KEEPCAPS, %d, ...): %v", i, j, v.label, j&1, err)
}
// At this point, we want all launched Go
// routines to confirm that they see the
// wanted value for KEEPCAPS.
for k := 0; k < routines; k++ {
question <- want
}
// At this point, we should have a large
// number of locked OS threads all wanting to
// reply.
for k := 0; k < routines; k++ {
if got := <-response; got != want {
t.Errorf("[%d,%d,%d] waiter result got=%d, want=%d", i, j, k, got, want)
}
}
// Provide an explicit opportunity for this Go
// routine to change Ms.
runtime.Gosched()
if once {
// One waiter routine will have exited.
routines--
}
// Whatever M we are now running on, confirm
// we see the wanted value too.
if v, _, e := syscall.Syscall(syscall.SYS_PRCTL, PR_GET_KEEPCAPS, 0, 0); e != 0 {
t.Errorf("[%d,%d] prctl(PR_GET_KEEPCAPS) failed: %v", i, j, e)
} else if v != want {
t.Errorf("[%d,%d] prctl(PR_GET_KEEPCAPS) gave wrong value: got=%v, want=1", i, j, v)
}
}
}
}
// compareStatus is used to confirm the contents of the thread
// specific status files match expectations.
func compareStatus(filter, expect string) error {
expected := filter + expect
pid := syscall.Getpid()
fs, err := os.ReadDir(fmt.Sprintf("/proc/%d/task", pid))
if err != nil {
return fmt.Errorf("unable to find %d tasks: %v", pid, err)
}
expectedProc := fmt.Sprintf("Pid:\t%d", pid)
foundAThread := false
for _, f := range fs {
tf := fmt.Sprintf("/proc/%s/status", f.Name())
d, err := os.ReadFile(tf)
if err != nil {
// There are a surprising number of ways this
// can error out on linux. We've seen all of
// the following, so treat any error here as
// equivalent to the "process is gone":
// os.IsNotExist(err),
// "... : no such process",
// "... : bad file descriptor.
continue
}
lines := strings.Split(string(d), "\n")
for _, line := range lines {
// Different kernel vintages pad differently.
line = strings.TrimSpace(line)
if strings.HasPrefix(line, "Pid:\t") {
// On loaded systems, it is possible
// for a TID to be reused really
// quickly. As such, we need to
// validate that the thread status
// info we just read is a task of the
// same process PID as we are
// currently running, and not a
// recently terminated thread
// resurfaced in a different process.
if line != expectedProc {
break
}
// Fall through in the unlikely case
// that filter at some point is
// "Pid:\t".
}
if strings.HasPrefix(line, filter) {
if line == expected {
foundAThread = true
break
}
if filter == "Groups:" && strings.HasPrefix(line, "Groups:\t") {
// https://github.com/golang/go/issues/46145
// Containers don't reliably output this line in sorted order so manually sort and compare that.
a := strings.Split(line[8:], " ")
sort.Strings(a)
got := strings.Join(a, " ")
if got == expected[8:] {
foundAThread = true
break
}
}
return fmt.Errorf("%q got:%q want:%q (bad) [pid=%d file:'%s' %v]\n", tf, line, expected, pid, string(d), expectedProc)
}
}
}
if !foundAThread {
return fmt.Errorf("found no thread /proc/<TID>/status files for process %q", expectedProc)
}
return nil
}
// killAThread locks the goroutine to an OS thread and exits; this
// causes an OS thread to terminate.
func killAThread(c <-chan struct{}) {
runtime.LockOSThread()
<-c
return
}
// TestSetuidEtc performs tests on all of the wrapped system calls
// that mirror to the 9 glibc syscalls with POSIX semantics. The test
// here is considered authoritative and should compile and run
// CGO_ENABLED=0 or 1. Note, there is an extended copy of this same
// test in ../../misc/cgo/test/issue1435.go which requires
// CGO_ENABLED=1 and launches pthreads from C that run concurrently
// with the Go code of the test - and the test validates that these
// pthreads are also kept in sync with the security state changed with
// the syscalls. Care should be taken to mirror any enhancements to
// this test here in that file too.
func TestSetuidEtc(t *testing.T) {
if syscall.Getuid() != 0 {
t.Skip("skipping root only test")
}
if _, err := os.Stat("/etc/alpine-release"); err == nil {
t.Skip("skipping glibc test on alpine - go.dev/issue/19938")
}
vs := []struct {
call string
fn func() error
filter, expect string
}{
{call: "Setegid(1)", fn: func() error { return syscall.Setegid(1) }, filter: "Gid:", expect: "\t0\t1\t0\t1"},
{call: "Setegid(0)", fn: func() error { return syscall.Setegid(0) }, filter: "Gid:", expect: "\t0\t0\t0\t0"},
{call: "Seteuid(1)", fn: func() error { return syscall.Seteuid(1) }, filter: "Uid:", expect: "\t0\t1\t0\t1"},
{call: "Setuid(0)", fn: func() error { return syscall.Setuid(0) }, filter: "Uid:", expect: "\t0\t0\t0\t0"},
{call: "Setgid(1)", fn: func() error { return syscall.Setgid(1) }, filter: "Gid:", expect: "\t1\t1\t1\t1"},
{call: "Setgid(0)", fn: func() error { return syscall.Setgid(0) }, filter: "Gid:", expect: "\t0\t0\t0\t0"},
{call: "Setgroups([]int{0,1,2,3})", fn: func() error { return syscall.Setgroups([]int{0, 1, 2, 3}) }, filter: "Groups:", expect: "\t0 1 2 3"},
{call: "Setgroups(nil)", fn: func() error { return syscall.Setgroups(nil) }, filter: "Groups:", expect: ""},
{call: "Setgroups([]int{0})", fn: func() error { return syscall.Setgroups([]int{0}) }, filter: "Groups:", expect: "\t0"},
{call: "Setregid(101,0)", fn: func() error { return syscall.Setregid(101, 0) }, filter: "Gid:", expect: "\t101\t0\t0\t0"},
{call: "Setregid(0,102)", fn: func() error { return syscall.Setregid(0, 102) }, filter: "Gid:", expect: "\t0\t102\t102\t102"},
{call: "Setregid(0,0)", fn: func() error { return syscall.Setregid(0, 0) }, filter: "Gid:", expect: "\t0\t0\t0\t0"},
{call: "Setreuid(1,0)", fn: func() error { return syscall.Setreuid(1, 0) }, filter: "Uid:", expect: "\t1\t0\t0\t0"},
{call: "Setreuid(0,2)", fn: func() error { return syscall.Setreuid(0, 2) }, filter: "Uid:", expect: "\t0\t2\t2\t2"},
{call: "Setreuid(0,0)", fn: func() error { return syscall.Setreuid(0, 0) }, filter: "Uid:", expect: "\t0\t0\t0\t0"},
{call: "Setresgid(101,0,102)", fn: func() error { return syscall.Setresgid(101, 0, 102) }, filter: "Gid:", expect: "\t101\t0\t102\t0"},
{call: "Setresgid(0,102,101)", fn: func() error { return syscall.Setresgid(0, 102, 101) }, filter: "Gid:", expect: "\t0\t102\t101\t102"},
{call: "Setresgid(0,0,0)", fn: func() error { return syscall.Setresgid(0, 0, 0) }, filter: "Gid:", expect: "\t0\t0\t0\t0"},
{call: "Setresuid(1,0,2)", fn: func() error { return syscall.Setresuid(1, 0, 2) }, filter: "Uid:", expect: "\t1\t0\t2\t0"},
{call: "Setresuid(0,2,1)", fn: func() error { return syscall.Setresuid(0, 2, 1) }, filter: "Uid:", expect: "\t0\t2\t1\t2"},
{call: "Setresuid(0,0,0)", fn: func() error { return syscall.Setresuid(0, 0, 0) }, filter: "Uid:", expect: "\t0\t0\t0\t0"},
}
for i, v := range vs {
// Generate some thread churn as we execute the tests.
c := make(chan struct{})
go killAThread(c)
close(c)
if err := v.fn(); err != nil {
t.Errorf("[%d] %q failed: %v", i, v.call, err)
continue
}
if err := compareStatus(v.filter, v.expect); err != nil {
t.Errorf("[%d] %q comparison: %v", i, v.call, err)
}
}
}
// TestAllThreadsSyscallError verifies that errors are properly returned when
// the syscall fails on the original thread.
func TestAllThreadsSyscallError(t *testing.T) {
// SYS_CAPGET takes pointers as the first two arguments. Since we pass
// 0, we expect to get EFAULT back.
r1, r2, err := syscall.AllThreadsSyscall(syscall.SYS_CAPGET, 0, 0, 0)
if err == syscall.ENOTSUP {
t.Skip("AllThreadsSyscall disabled with cgo")
}
if err != syscall.EFAULT {
t.Errorf("AllThreadSyscall(SYS_CAPGET) got %d, %d, %v, want err %v", r1, r2, err, syscall.EFAULT)
}
}
// TestAllThreadsSyscallBlockedSyscall confirms that AllThreadsSyscall
// can interrupt threads in long-running system calls. This test will
// deadlock if this doesn't work correctly.
func TestAllThreadsSyscallBlockedSyscall(t *testing.T) {
if _, _, err := syscall.AllThreadsSyscall(syscall.SYS_PRCTL, PR_SET_KEEPCAPS, 0, 0); err == syscall.ENOTSUP {
t.Skip("AllThreadsSyscall disabled with cgo")
}
rd, wr, err := os.Pipe()
if err != nil {
t.Fatalf("unable to obtain a pipe: %v", err)
}
// Perform a blocking read on the pipe.
var wg sync.WaitGroup
ready := make(chan bool)
wg.Add(1)
go func() {
data := make([]byte, 1)
// To narrow the window we have to wait for this
// goroutine to block in read, synchronize just before
// calling read.
ready <- true
// We use syscall.Read directly to avoid the poller.
// This will return when the write side is closed.
n, err := syscall.Read(int(rd.Fd()), data)
if !(n == 0 && err == nil) {
t.Errorf("expected read to return 0, got %d, %s", n, err)
}
// Clean up rd and also ensure rd stays reachable so
// it doesn't get closed by GC.
rd.Close()
wg.Done()
}()
<-ready
// Loop here to give the goroutine more time to block in read.
// Generally this will trigger on the first iteration anyway.
pid := syscall.Getpid()
for i := 0; i < 100; i++ {
if id, _, e := syscall.AllThreadsSyscall(syscall.SYS_GETPID, 0, 0, 0); e != 0 {
t.Errorf("[%d] getpid failed: %v", i, e)
} else if int(id) != pid {
t.Errorf("[%d] getpid got=%d, want=%d", i, id, pid)
}
// Provide an explicit opportunity for this goroutine
// to change Ms.
runtime.Gosched()
}
wr.Close()
wg.Wait()
}