libgocryptfs/tests/matrix/matrix_test.go
Jakob Unterwurzacher b056776a01 tests: adapt dir overwrite test for Go 1.8
In Go 1.8, os.Rename refuses to overwrite an empty directory.
Switch to syscall.Rename, which still does the right thing.
2017-02-20 21:27:37 +01:00

755 lines
20 KiB
Go

// Tests run for (almost all) combinations of openssl, aessiv, plaintextnames.
package matrix
// File reading, writing, modification, truncate
//
// Runs everything four times, for all combinations of
// "-plaintextnames" and "-openssl".
//
// Test Matrix:
// openssl=true openssl=false
// plaintextnames=false X X
// plaintextnames=true X X
import (
"bytes"
"flag"
"fmt"
"io/ioutil"
"os"
"os/exec"
"runtime"
"sync"
"syscall"
"testing"
"github.com/rfjakob/gocryptfs/internal/cryptocore"
"github.com/rfjakob/gocryptfs/internal/nametransform"
"github.com/rfjakob/gocryptfs/internal/syscallcompat"
"github.com/rfjakob/gocryptfs/tests/test_helpers"
)
// Several tests need to be aware if plaintextnames is active or not, so make this
// a global variable
var testcase testcaseMatrix
type testcaseMatrix struct {
plaintextnames bool
openssl string
aessiv bool
raw64 bool
}
var matrix = []testcaseMatrix{
// Normal
{false, "auto", false, false},
{false, "true", false, false},
{false, "false", false, false},
// Plaintextnames
{true, "true", false, false},
{true, "false", false, false},
// AES-SIV (does not use openssl, no need to test permutations)
{false, "auto", true, false},
{true, "auto", true, false},
// Raw64
{false, "auto", false, true},
}
// This is the entry point for the tests
func TestMain(m *testing.M) {
// Make "testing.Verbose()" return the correct value
flag.Parse()
for _, testcase = range matrix {
if !cryptocore.HaveModernGoGCM && testcase.openssl != "true" {
fmt.Printf("Skipping Go GCM variant, Go installation is too old")
continue
}
if testcase.raw64 && !nametransform.HaveRaw64 {
fmt.Printf("Skipping raw64 test, Go installation is too old")
continue
}
if testing.Verbose() {
fmt.Printf("matrix: testcase = %#v\n", testcase)
}
test_helpers.ResetTmpDir(!testcase.plaintextnames)
opts := []string{"-zerokey"}
opts = append(opts, fmt.Sprintf("-openssl=%v", testcase.openssl))
opts = append(opts, fmt.Sprintf("-plaintextnames=%v", testcase.plaintextnames))
opts = append(opts, fmt.Sprintf("-aessiv=%v", testcase.aessiv))
opts = append(opts, fmt.Sprintf("-raw64=%v", testcase.raw64))
test_helpers.MountOrExit(test_helpers.DefaultCipherDir, test_helpers.DefaultPlainDir, opts...)
r := m.Run()
test_helpers.UnmountPanic(test_helpers.DefaultPlainDir)
if r != 0 {
os.Exit(r)
}
}
os.Exit(0)
}
// Write "n" zero bytes to filename "fn", read again, compare hash
func testWriteN(t *testing.T, fn string, n int) string {
file, err := os.Create(test_helpers.DefaultPlainDir + "/" + fn)
if err != nil {
t.Fatal(err)
}
d := make([]byte, n)
written, err := file.Write(d)
if err != nil || written != len(d) {
t.Errorf("err=\"%s\", written=%d", err, written)
}
err = file.Close()
if err != nil {
t.Error(err)
}
test_helpers.VerifySize(t, test_helpers.DefaultPlainDir+"/"+fn, n)
hashWant := test_helpers.Md5hex(d)
hashActual := test_helpers.Md5fn(test_helpers.DefaultPlainDir + "/" + fn)
if hashActual != hashWant {
t.Errorf("Wrong content, hashWant=%s hashActual=%s", hashWant, hashActual)
}
return hashActual
}
func TestWrite10(t *testing.T) {
testWriteN(t, "10", 10)
}
func TestWrite100(t *testing.T) {
testWriteN(t, "100", 100)
}
func TestWrite1M(t *testing.T) {
testWriteN(t, "1M", 1024*1024)
}
func TestWrite100x100(t *testing.T) {
hashWant := testWriteN(t, "100x100", 100)
// Read and check 100 times to catch race conditions
var i int
for i = 0; i < 100; i++ {
hashActual := test_helpers.Md5fn(test_helpers.DefaultPlainDir + "/100")
if hashActual != hashWant {
fmt.Printf("Read corruption in loop #%d\n", i)
t.FailNow()
} else {
//fmt.Print(".")
}
}
}
// Hint for calculating reference md5sums:
// dd if=/dev/zero count=1 bs=XYZ | md5sum
func TestTruncate(t *testing.T) {
fn := test_helpers.DefaultPlainDir + "/truncate"
file, err := os.Create(fn)
if err != nil {
t.FailNow()
}
// Grow to two blocks
file.Truncate(7000)
test_helpers.VerifySize(t, fn, 7000)
if md5 := test_helpers.Md5fn(fn); md5 != "95d4ec7038e3e4fdbd5f15c34c3f0b34" {
t.Errorf("Wrong md5 %s", md5)
}
// Shrink - needs RMW
file.Truncate(6999)
test_helpers.VerifySize(t, fn, 6999)
if md5 := test_helpers.Md5fn(fn); md5 != "35fd15873ec6c35380064a41b9b9683b" {
t.Errorf("Wrong md5 %s", md5)
}
// Shrink to one partial block
file.Truncate(465)
test_helpers.VerifySize(t, fn, 465)
if md5 := test_helpers.Md5fn(fn); md5 != "a1534d6e98a6b21386456a8f66c55260" {
t.Errorf("Wrong md5 %s", md5)
}
// Grow to exactly one block
file.Truncate(4096)
test_helpers.VerifySize(t, fn, 4096)
if md5 := test_helpers.Md5fn(fn); md5 != "620f0b67a91f7f74151bc5be745b7110" {
t.Errorf("Wrong md5 %s", md5)
}
// Truncate to zero
file.Truncate(0)
test_helpers.VerifySize(t, fn, 0)
// Grow to 10MB (creates file holes)
var sz int
sz = 10 * 1024 * 1024
file.Truncate(int64(sz))
test_helpers.VerifySize(t, fn, sz)
if md5 := test_helpers.Md5fn(fn); md5 != "f1c9645dbc14efddc7d8a322685f26eb" {
t.Errorf("Wrong md5 %s", md5)
}
// Grow to 10MB + 100B (partial block on the end)
sz = 10*1024*1024 + 100
file.Truncate(int64(sz))
test_helpers.VerifySize(t, fn, sz)
if md5 := test_helpers.Md5fn(fn); md5 != "c23ea79b857b91a7ff07c6ecf185f1ca" {
t.Errorf("Wrong md5 %s", md5)
}
// Grow to 20MB (creates file holes, partial block on the front)
sz = 20 * 1024 * 1024
file.Truncate(int64(sz))
test_helpers.VerifySize(t, fn, sz)
if md5 := test_helpers.Md5fn(fn); md5 != "8f4e33f3dc3e414ff94e5fb6905cba8c" {
t.Errorf("Wrong md5 %s", md5)
}
}
const (
// From man statfs
TMPFS_MAGIC = 0x01021994
EXT4_SUPER_MAGIC = 0xef53
)
// isWellKnownFS decides if the backing filesystem is well-known.
// The expected allocated sizes are only valid on tmpfs and ext4. btrfs
// gives different results, but that's not an error.
func isWellKnownFS(fn string) bool {
var fs syscall.Statfs_t
err := syscall.Statfs(fn, &fs)
if err != nil {
panic(err)
}
if fs.Type == EXT4_SUPER_MAGIC || fs.Type == TMPFS_MAGIC {
return true
}
return false
}
const FALLOC_DEFAULT = 0x00
const FALLOC_FL_KEEP_SIZE = 0x01
func TestFallocate(t *testing.T) {
if runtime.GOOS == "darwin" {
t.Skipf("OSX does not support fallocate")
}
fn := test_helpers.DefaultPlainDir + "/fallocate"
file, err := os.Create(fn)
if err != nil {
t.FailNow()
}
wellKnown := isWellKnownFS(test_helpers.DefaultCipherDir)
fd := int(file.Fd())
nBytes := test_helpers.Du(t, fd)
if nBytes != 0 {
t.Fatalf("Empty file has %d bytes", nBytes)
}
// Allocate 30 bytes, keep size
// gocryptfs || (0 blocks)
// ext4 | d | (1 block)
err = syscallcompat.Fallocate(fd, FALLOC_FL_KEEP_SIZE, 0, 30)
if err != nil {
t.Error(err)
}
var want int64
nBytes = test_helpers.Du(t, fd)
want = 4096
if nBytes != want {
t.Errorf("Expected %d allocated bytes, have %d", want, nBytes)
}
test_helpers.VerifySize(t, fn, 0)
// Three ciphertext blocks. The middle one should be a file hole.
// gocryptfs | h | h | d| (1 block)
// ext4 | d | h | d | (2 blocks)
// (Note that gocryptfs blocks are slightly bigger than the ext4 blocks,
// but the last one is partial)
err = file.Truncate(9000)
if err != nil {
t.Fatal(err)
}
nBytes = test_helpers.Du(t, fd)
want = 2 * 4096
if wellKnown && nBytes != want {
t.Errorf("Expected %d allocated bytes, have %d", want, nBytes)
}
if md5 := test_helpers.Md5fn(fn); md5 != "5420afa22f6423a9f59e669540656bb4" {
t.Errorf("Wrong md5 %s", md5)
}
// Allocate the whole file space
// gocryptfs | h | h | d| (1 block)
// ext4 | d | d | d | (3 blocks
err = syscallcompat.Fallocate(fd, FALLOC_DEFAULT, 0, 9000)
if err != nil {
t.Fatal(err)
}
nBytes = test_helpers.Du(t, fd)
want = 3 * 4096
if nBytes != want {
t.Errorf("Expected %d allocated bytes, have %d", want, nBytes)
}
// Neither apparent size nor content should have changed
test_helpers.VerifySize(t, fn, 9000)
if md5 := test_helpers.Md5fn(fn); md5 != "5420afa22f6423a9f59e669540656bb4" {
t.Errorf("Wrong md5 %s", md5)
}
// Partial block on the end. The first ext4 block is dirtied by the header.
// gocryptfs | h | h | d| (1 block)
// ext4 | d | h | d | (2 blocks)
file.Truncate(0)
file.Truncate(9000)
nBytes = test_helpers.Du(t, fd)
want = 2 * 4096
if wellKnown && nBytes != want {
t.Errorf("Expected %d allocated bytes, have %d", want, nBytes)
}
// Allocate 10 bytes in the second block
// gocryptfs | h | h | d| (1 block)
// ext4 | d | d | d | (3 blocks)
syscallcompat.Fallocate(fd, FALLOC_DEFAULT, 5000, 10)
nBytes = test_helpers.Du(t, fd)
want = 3 * 4096
if wellKnown && nBytes != want {
t.Errorf("Expected %d allocated bytes, have %d", want, nBytes)
}
// Neither apparent size nor content should have changed
test_helpers.VerifySize(t, fn, 9000)
if md5 := test_helpers.Md5fn(fn); md5 != "5420afa22f6423a9f59e669540656bb4" {
t.Errorf("Wrong md5 %s", md5)
}
// Grow the file to 4 blocks
// gocryptfs | h | h | d |d| (2 blocks)
// ext4 | d | d | d | d | (4 blocks)
syscallcompat.Fallocate(fd, FALLOC_DEFAULT, 15000, 10)
nBytes = test_helpers.Du(t, fd)
want = 4 * 4096
if wellKnown && nBytes != want {
t.Errorf("Expected %d allocated bytes, have %d", want, nBytes)
}
test_helpers.VerifySize(t, fn, 15010)
if md5 := test_helpers.Md5fn(fn); md5 != "c4c44c7a41ab7798a79d093eb44f99fc" {
t.Errorf("Wrong md5 %s", md5)
}
// Shrinking a file using fallocate should have no effect
for _, off := range []int64{0, 10, 2000, 5000} {
for _, sz := range []int64{0, 1, 42, 6000} {
syscallcompat.Fallocate(fd, FALLOC_DEFAULT, off, sz)
test_helpers.VerifySize(t, fn, 15010)
if md5 := test_helpers.Md5fn(fn); md5 != "c4c44c7a41ab7798a79d093eb44f99fc" {
t.Errorf("Wrong md5 %s", md5)
}
}
}
// Cleanup
file.Close()
syscall.Unlink(fn)
if !wellKnown {
// Even though most tests have been executed still, inform the user
// that some were disabled
t.Skipf("backing fs is not ext4 or tmpfs, skipped some disk-usage checks\n")
}
}
func TestAppend(t *testing.T) {
fn := test_helpers.DefaultPlainDir + "/append"
file, err := os.Create(fn)
if err != nil {
t.FailNow()
}
data := []byte("testdata123456789") // length 17
var buf bytes.Buffer
var hashWant string
for i := 0; i <= 500; i++ {
file.Write(data)
buf.Write(data)
hashWant = test_helpers.Md5hex(buf.Bytes())
hashActual := test_helpers.Md5fn(fn)
if hashWant != hashActual {
t.FailNow()
}
}
// Overwrite with the same data
// Hash must stay the same
file.Seek(0, 0)
for i := 0; i <= 500; i++ {
file.Write(data)
hashActual := test_helpers.Md5fn(fn)
if hashWant != hashActual {
t.FailNow()
}
}
}
// Create a file with holes by writing to offset 0 (block #0) and
// offset 4096 (block #1).
func TestFileHoles(t *testing.T) {
fn := test_helpers.DefaultPlainDir + "/fileholes"
file, err := os.Create(fn)
if err != nil {
t.Errorf("file create failed")
}
foo := []byte("foo")
file.Write(foo)
file.WriteAt(foo, 4096)
_, err = ioutil.ReadFile(fn)
if err != nil {
t.Error(err)
}
}
// sContains - does the slice of strings "haystack" contain "needle"?
func sContains(haystack []string, needle string) bool {
for _, element := range haystack {
if element == needle {
return true
}
}
return false
}
func TestRmwRace(t *testing.T) {
runtime.GOMAXPROCS(10)
fn := test_helpers.DefaultPlainDir + "/rmwrace"
f1, err := os.Create(fn)
if err != nil {
t.Fatalf("file create failed")
}
f2, err := os.Create(fn)
if err != nil {
t.Fatalf("file create failed")
}
oldBlock := bytes.Repeat([]byte("o"), 4096)
newBlock := bytes.Repeat([]byte("n"), 4096)
shortBlock := bytes.Repeat([]byte("s"), 16)
mergedBlock := make([]byte, 4096)
copy(mergedBlock, newBlock)
copy(mergedBlock[4080:], shortBlock)
goodMd5 := make(map[string]int)
for i := 0; i < 1000; i++ {
// Reset to [ooooooooo]
_, err = f1.WriteAt(oldBlock, 0)
if err != nil {
t.Fatalf("Write failed")
}
var wg sync.WaitGroup
wg.Add(2)
// Write to the end of the file, [....ssss]
go func() {
f1.WriteAt(shortBlock, 4080)
wg.Done()
}()
// Overwrite to [nnnnnnn]
go func() {
f2.WriteAt(newBlock, 0)
wg.Done()
}()
wg.Wait()
// The file should be either:
// [nnnnnnnnnn] (md5: 6c1660fdabccd448d1359f27b3db3c99) or
// [nnnnnnssss] (md5: da885006a6a284530a427c73ce1e5c32)
// but it must not be
// [oooooossss]
buf, _ := ioutil.ReadFile(fn)
m := test_helpers.Md5hex(buf)
goodMd5[m] = goodMd5[m] + 1
/*
if m == "6c1660fdabccd448d1359f27b3db3c99" {
fmt.Println(hex.Dump(buf))
t.FailNow()
}
*/
}
}
// With "--plaintextnames", the name "/gocryptfs.conf" is reserved.
// Otherwise there should be no restrictions.
func TestFiltered(t *testing.T) {
filteredFile := test_helpers.DefaultPlainDir + "/gocryptfs.conf"
file, err := os.Create(filteredFile)
if testcase.plaintextnames && err == nil {
t.Errorf("should have failed but didn't")
} else if !testcase.plaintextnames && err != nil {
t.Error(err)
}
file.Close()
err = os.Remove(filteredFile)
if testcase.plaintextnames && err == nil {
t.Errorf("should have failed but didn't")
} else if !testcase.plaintextnames && err != nil {
t.Error(err)
}
}
func TestFilenameEncryption(t *testing.T) {
file, err := os.Create(test_helpers.DefaultPlainDir + "/TestFilenameEncryption.txt")
file.Close()
if err != nil {
t.Fatal(err)
}
_, err = os.Stat(test_helpers.DefaultCipherDir + "/TestFilenameEncryption.txt")
if testcase.plaintextnames && err != nil {
t.Errorf("plaintextnames not working: %v", err)
} else if !testcase.plaintextnames && err == nil {
t.Errorf("file name encryption not working")
}
}
// Test Mkdir and Rmdir
func testMkdirRmdir(t *testing.T) {
test_helpers.TestMkdirRmdir(t, test_helpers.DefaultPlainDir)
}
// Test Rename
func testRename(t *testing.T) {
test_helpers.TestRename(t, test_helpers.DefaultPlainDir)
}
// Overwrite an empty directory with another directory
func TestDirOverwrite(t *testing.T) {
dir1 := test_helpers.DefaultPlainDir + "/DirOverwrite1"
dir2 := test_helpers.DefaultPlainDir + "/DirOverwrite2"
err := os.Mkdir(dir1, 0777)
if err != nil {
t.Fatal(err)
}
err = os.Mkdir(dir2, 0777)
if err != nil {
t.Fatal(err)
}
err = syscall.Rename(dir1, dir2)
if err != nil {
t.Fatal(err)
}
}
func TestLongNames(t *testing.T) {
fi, err := ioutil.ReadDir(test_helpers.DefaultCipherDir)
if err != nil {
t.Fatal(err)
}
cnt1 := len(fi)
wd := test_helpers.DefaultPlainDir + "/"
// Create file with long name
n255x := string(bytes.Repeat([]byte("x"), 255))
f, err := os.Create(wd + n255x)
if err != nil {
t.Fatalf("Could not create n255x: %v", err)
}
f.Close()
if !test_helpers.VerifyExistence(wd + n255x) {
t.Errorf("n255x is not in directory listing")
}
// Rename long to long
n255y := string(bytes.Repeat([]byte("y"), 255))
err = os.Rename(wd+n255x, wd+n255y)
if err != nil {
t.Fatalf("Could not rename n255x to n255y: %v", err)
}
if !test_helpers.VerifyExistence(wd + n255y) {
t.Errorf("n255y is not in directory listing")
}
// Rename long to short
err = os.Rename(wd+n255y, wd+"short")
if err != nil {
t.Fatalf("Could not rename n255y to short: %v", err)
}
if !test_helpers.VerifyExistence(wd + "short") {
t.Errorf("short is not in directory listing")
}
// Rename short to long
err = os.Rename(wd+"short", wd+n255x)
if err != nil {
t.Fatalf("Could not rename short to n255x: %v", err)
}
if !test_helpers.VerifyExistence(wd + n255x) {
t.Errorf("255x is not in directory listing II")
}
// Unlink
err = syscall.Unlink(wd + n255x)
if err != nil {
t.Fatalf("Could not unlink n255x: %v", err)
}
if test_helpers.VerifyExistence(wd + n255x) {
t.Errorf("n255x still there after unlink")
}
// Long symlink
n255s := string(bytes.Repeat([]byte("s"), 255))
err = os.Symlink("/", wd+n255s)
if err != nil {
t.Fatal(err)
}
if !test_helpers.VerifyExistence(wd + n255s) {
t.Errorf("n255s is not in directory listing")
}
err = syscall.Unlink(wd + n255s)
if err != nil {
t.Error(err)
}
// Long dir
n255d := string(bytes.Repeat([]byte("d"), 255))
err = os.Mkdir(wd+n255d, 0777)
if err != nil {
t.Fatal(err)
}
err = syscall.Rmdir(wd + n255d)
if err != nil {
t.Error(err)
}
// Check for orphaned files
fi, err = ioutil.ReadDir(test_helpers.DefaultCipherDir)
if err != nil {
t.Fatal(err)
}
cnt2 := len(fi)
if cnt1 != cnt2 {
t.Errorf("Leftover files, cnt1=%d cnt2=%d", cnt1, cnt2)
}
}
// Create hard link with long name.
// This was broken up to v1.2.
func TestLongLink(t *testing.T) {
wd := test_helpers.DefaultPlainDir + "/"
target := wd + "TestLongLink.target"
f, err := os.Create(target)
if err != nil {
t.Fatalf("%v", err)
}
f.Close()
l255 := string(bytes.Repeat([]byte("l"), 255))
err = os.Link(target, wd+l255)
if err != nil {
t.Error(err)
}
}
func TestLchown(t *testing.T) {
name := test_helpers.DefaultPlainDir + "/symlink"
err := os.Symlink("/target/does/not/exist", name)
if err != nil {
t.Fatal(err)
}
err = os.Chown(name, os.Getuid(), os.Getgid())
if err == nil {
t.Error("Chown on dangling symlink should fail")
}
err = os.Lchown(name, os.Getuid(), os.Getgid())
if err != nil {
t.Error(err)
}
}
// Set nanoseconds by path, symlink
func TestUtimesNanoSymlink(t *testing.T) {
path := test_helpers.DefaultPlainDir + "/utimesnano_symlink"
err := os.Symlink("/some/nonexisting/file", path)
if err != nil {
t.Fatal(err)
}
// syscall.UtimesNano does not provide a way to pass AT_SYMLINK_NOFOLLOW,
// so we call the external utility "touch", which does.
cmd := exec.Command("touch", "--no-dereference", path)
cmd.Stderr = os.Stderr
cmd.Stdout = os.Stdout
err = cmd.Run()
if err != nil {
t.Error(err)
}
}
type utimesTestcaseStruct struct {
// Input atime and mtime
in [2]syscall.Timespec
// Expected output atime and mtime
out [2]syscall.Timespec
}
func compareUtimes(want [2]syscall.Timespec, actual [2]syscall.Timespec) error {
tsNames := []string{"atime", "mtime"}
for i := range want {
if want[i].Sec != actual[i].Sec {
return fmt.Errorf("Wrong %s seconds: want=%d actual=%d", tsNames[i], want[i].Sec, actual[i].Sec)
}
if want[i].Nsec != actual[i].Nsec {
return fmt.Errorf("Wrong %s nanoseconds: want=%d actual=%d", tsNames[i], want[i].Nsec, actual[i].Nsec)
}
}
return nil
}
const _UTIME_OMIT = ((1 << 30) - 2)
// doTestUtimesNano verifies that setting nanosecond-precision times on "path"
// works correctly. Pass "/proc/self/fd/N" to test a file descriptor.
func doTestUtimesNano(t *testing.T, path string) {
utimeTestcases := []utimesTestcaseStruct{
{
in: [2]syscall.Timespec{{Sec: 50, Nsec: 0}, {Sec: 50, Nsec: 0}},
out: [2]syscall.Timespec{{Sec: 50, Nsec: 0}, {Sec: 50, Nsec: 0}},
},
{
in: [2]syscall.Timespec{{Sec: 1, Nsec: 2}, {Sec: 3, Nsec: 4}},
out: [2]syscall.Timespec{{Sec: 1, Nsec: 2}, {Sec: 3, Nsec: 4}},
},
{
in: [2]syscall.Timespec{{Sec: 7, Nsec: 8}, {Sec: 99, Nsec: _UTIME_OMIT}},
out: [2]syscall.Timespec{{Sec: 7, Nsec: 8}, {Sec: 3, Nsec: 4}},
},
{
in: [2]syscall.Timespec{{Sec: 99, Nsec: _UTIME_OMIT}, {Sec: 5, Nsec: 6}},
out: [2]syscall.Timespec{{Sec: 7, Nsec: 8}, {Sec: 5, Nsec: 6}},
},
}
for i, tc := range utimeTestcases {
err := syscall.UtimesNano(path, tc.in[:])
if err != nil {
t.Fatal(err)
}
var st syscall.Stat_t
err = syscall.Stat(path, &st)
if err != nil {
t.Fatal(err)
}
err = compareUtimes(tc.out, extractAtimeMtime(st))
if err != nil {
t.Errorf("Testcase %d: %v", i, err)
}
}
}
// Set nanoseconds by path, normal file
func TestUtimesNano(t *testing.T) {
path := test_helpers.DefaultPlainDir + "/utimesnano"
err := ioutil.WriteFile(path, []byte("foobar"), 0600)
if err != nil {
t.Fatal(err)
}
doTestUtimesNano(t, path)
}
// Set nanoseconds by fd
func TestUtimesNanoFd(t *testing.T) {
path := test_helpers.DefaultPlainDir + "/utimesnanofd"
f, err := os.Create(path)
if err != nil {
t.Fatal(err)
}
procPath := fmt.Sprintf("/proc/self/fd/%d", f.Fd())
doTestUtimesNano(t, procPath)
}