readpassword: delete CheckTrailingGarbage

CheckTrailingGarbage was called even when "-passfile" was
used, which is stupid, and causes false positives:

https://github.com/rfjakob/gocryptfs/issues/391
(false error "Received trailing garbage after the password"
when using -passfile in .bash_profile)

Instead of trying to improve the logic to handle that case
and make everything even more complicated, delete the function.

It is unclear if actually helps in some cases, and it definitely
harms as shown by the above bug report.

init_dir.go

@@ -81,7 +81,6 @@ func initDir(args *argContainer) {
 		} else {
 			// Normal password entry
 			password = readpassword.Twice([]string(args.extpass), args.passfile)
-			readpassword.CheckTrailingGarbage()
 		}
 		creator := tlog.ProgramName + " " + GitVersion
 		err = configfile.Create(args.config, password, args.plaintextnames,

internal/fusefrontend_reverse/reverse_longnames.go

@@ -105,7 +105,7 @@ func (rfs *ReverseFS) findLongnameParent(dir string, dirIV []byte, longname stri
 }
 
 func (rfs *ReverseFS) newNameFile(relPath string) (nodefs.File, fuse.Status) {
-	dotName := filepath.Base(relPath)                                    // gocryptfs.longname.XYZ.name
+	dotName := filepath.Base(relPath)                       // gocryptfs.longname.XYZ.name
 	longname := nametransform.RemoveLongNameSuffix(dotName) // gocryptfs.longname.XYZ
 	// cipher directory
 	cDir := nametransform.Dir(relPath)

internal/readpassword/read.go

@@ -8,8 +8,6 @@ import (
 	"os"
 	"os/exec"
 	"strings"
-	"sync"
-	"time"
 
 	"golang.org/x/crypto/ssh/terminal"
 
@@ -159,33 +157,3 @@ func readLineUnbuffered(r io.Reader) (l []byte) {
 		l = append(l, b...)
 	}
 }
-
-// CheckTrailingGarbage tries to read one byte from stdin and exits with a
-// fatal error if the read returns any data.
-// This is meant to be called after reading the password, when there is no more
-// data expected. This helps to catch problems with third-party tools that
-// interface with gocryptfs.
-//
-// This is tested via TestInitTrailingGarbage() in tests/cli/cli_test.go.
-func CheckTrailingGarbage() {
-	if terminal.IsTerminal(int(os.Stdin.Fd())) {
-		// Be lenient when interacting with a human.
-		return
-	}
-	var wg sync.WaitGroup
-	wg.Add(1)
-	go func() {
-		b := make([]byte, 1)
-		wg.Done()
-		n, _ := os.Stdin.Read(b)
-		if n > 0 {
-			tlog.Fatal.Printf("Received trailing garbage after the password")
-			os.Exit(exitcodes.ReadPassword)
-		}
-	}()
-	// Wait for the goroutine to start up plus one millisecond for the read to
-	// return. If there is data available, this SHOULD be plenty of time to
-	// read one byte. However, I don't see a way to be sure.
-	wg.Wait()
-	time.Sleep(1 * time.Millisecond)
-}

main.go

@@ -94,7 +94,6 @@ func changePassword(args *argContainer) {
 		}
 		tlog.Info.Println("Please enter your new password.")
 		newPw := readpassword.Twice([]string(args.extpass), args.passfile)
-		readpassword.CheckTrailingGarbage()
 		confFile.EncryptKey(masterkey, newPw, confFile.ScryptObject.LogN())
 		for i := range newPw {
 			newPw[i] = 0

masterkey.go

@@ -69,8 +69,5 @@ func getMasterKey(args *argContainer) (masterkey []byte, confFile *configfile.Co
 		}
 		exitcodes.Exit(err)
 	}
-	if !args.trezor {
-		readpassword.CheckTrailingGarbage()
-	}
 	return masterkey, confFile
 }

tests/cli/cli_test.go

@@ -317,50 +317,6 @@ func TestShadows(t *testing.T) {
 	}
 }
 
-// TestInitTrailingGarbage verfies that gocryptfs exits with an error if we
-// pass additional data after the password.
-func TestInitTrailingGarbage(t *testing.T) {
-	table := []struct {
-		pw            string
-		closeStdin    bool
-		expectSuccess bool
-	}{
-		{"foo\n", false, true},
-		{"foo", true, true},
-		{"foo\n", true, true},
-		{"foo\n\n", false, false},
-		{"foo\nbar", false, false},
-		{"foo\n\n", true, false},
-		{"foo\nbar", true, false},
-	}
-	for _, row := range table {
-		dir, err := ioutil.TempDir(test_helpers.TmpDir, "")
-		if err != nil {
-			t.Fatal(err)
-		}
-		cmd := exec.Command(test_helpers.GocryptfsBinary, "-q", "-init", "-scryptn=10", dir)
-		childStdin, err := cmd.StdinPipe()
-		if err != nil {
-			t.Fatal(err)
-		}
-		err = cmd.Start()
-		if err != nil {
-			t.Fatal(err)
-		}
-		childStdin.Write([]byte(row.pw))
-		if row.closeStdin {
-			childStdin.Close()
-		}
-		err = cmd.Wait()
-		success := (err == nil)
-		if success == true && row.expectSuccess == false {
-			t.Errorf("pw=%q should have failed, but succeeded", row.pw)
-		} else if success == false && row.expectSuccess == true {
-			t.Errorf("pw=%q should have succeeded, but failed", row.pw)
-		}
-	}
-}
-
 // TestMountPasswordIncorrect makes sure the correct exit code is used when the password
 // was incorrect while mounting
 func TestMountPasswordIncorrect(t *testing.T) {