readpassword: convert from string to []byte

This will allows us to overwrite the password
with zeros once we are done with it.

https://github.com/rfjakob/gocryptfs/issues/211

7 files changed, 38 insertions, 33 deletions

diff --git a/internal/configfile/config_file.go b/internal/configfile/config_file.go
index 01e3b80..3fd16c7 100644
--- a/internal/configfile/config_file.go
+++ b/internal/configfile/config_file.go
@@ -67,7 +67,7 @@ func randBytesDevRandom(n int) []byte {
 // CreateConfFile - create a new config with a random key encrypted with
 // "password" and write it to "filename".
 // Uses scrypt with cost parameter logN.
-func CreateConfFile(filename string, password string, plaintextNames bool, logN int, creator string, aessiv bool, devrandom bool) error {
+func CreateConfFile(filename string, password []byte, plaintextNames bool, logN int, creator string, aessiv bool, devrandom bool) error {
 	var cf ConfFile
 	cf.filename = filename
 	cf.Creator = creator
@@ -114,7 +114,7 @@ func CreateConfFile(filename string, password string, plaintextNames bool, logN
 //
 // If "password" is empty, the config file is read
 // but the key is not decrypted (returns nil in its place).
-func LoadConfFile(filename string, password string) ([]byte, *ConfFile, error) {
+func LoadConfFile(filename string, password []byte) ([]byte, *ConfFile, error) {
 	var cf ConfFile
 	cf.filename = filename
 
@@ -171,7 +171,7 @@ func LoadConfFile(filename string, password string) ([]byte, *ConfFile, error) {
 
 		return nil, nil, fmt.Errorf("Deprecated filesystem")
 	}
-	if password == "" {
+	if len(password) == 0 {
 		// We have validated the config file, but without a password we cannot
 		// decrypt the master key. Return only the parsed config.
 		return nil, &cf, nil
@@ -199,7 +199,7 @@ func LoadConfFile(filename string, password string) ([]byte, *ConfFile, error) {
 // and store it in cf.EncryptedKey.
 // Uses scrypt with cost parameter logN and stores the scrypt parameters in
 // cf.ScryptObject.
-func (cf *ConfFile) EncryptKey(key []byte, password string, logN int) {
+func (cf *ConfFile) EncryptKey(key []byte, password []byte, logN int) {
 	// Generate scrypt-derived key from password
 	cf.ScryptObject = NewScryptKDF(logN)
 	scryptHash := cf.ScryptObject.DeriveKey(password)
diff --git a/internal/configfile/config_test.go b/internal/configfile/config_test.go
index b984a37..15728c6 100644
--- a/internal/configfile/config_test.go
+++ b/internal/configfile/config_test.go
@@ -8,8 +8,10 @@ import (
 	"github.com/rfjakob/gocryptfs/internal/tlog"
 )
 
+var testPw = []byte("test")
+
 func TestLoadV1(t *testing.T) {
-	_, _, err := LoadConfFile("config_test/v1.conf", "test")
+	_, _, err := LoadConfFile("config_test/v1.conf", testPw)
 	if err == nil {
 		t.Errorf("Outdated v1 config file must fail to load but it didn't")
 	} else if testing.Verbose() {
@@ -22,7 +24,7 @@ func TestLoadV1(t *testing.T) {
 func TestLoadV2(t *testing.T) {
 	t1 := time.Now()
 
-	_, _, err := LoadConfFile("config_test/v2.conf", "test")
+	_, _, err := LoadConfFile("config_test/v2.conf", testPw)
 	if err != nil {
 		t.Errorf("Could not load v2 config file: %v", err)
 	}
@@ -37,21 +39,21 @@ func TestLoadV2PwdError(t *testing.T) {
 	if !testing.Verbose() {
 		tlog.Warn.Enabled = false
 	}
-	_, _, err := LoadConfFile("config_test/v2.conf", "wrongpassword")
+	_, _, err := LoadConfFile("config_test/v2.conf", []byte("wrongpassword"))
 	if err == nil {
 		t.Errorf("Loading with wrong password must fail but it didn't")
 	}
 }
 
 func TestLoadV2Feature(t *testing.T) {
-	_, _, err := LoadConfFile("config_test/PlaintextNames.conf", "test")
+	_, _, err := LoadConfFile("config_test/PlaintextNames.conf", testPw)
 	if err != nil {
 		t.Errorf("Could not load v2 PlaintextNames config file: %v", err)
 	}
 }
 
 func TestLoadV2StrangeFeature(t *testing.T) {
-	_, _, err := LoadConfFile("config_test/StrangeFeature.conf", "test")
+	_, _, err := LoadConfFile("config_test/StrangeFeature.conf", testPw)
 	if err == nil {
 		t.Errorf("Loading unknown feature must fail but it didn't")
 	} else if testing.Verbose() {
@@ -60,11 +62,11 @@ func TestLoadV2StrangeFeature(t *testing.T) {
 }
 
 func TestCreateConfDefault(t *testing.T) {
-	err := CreateConfFile("config_test/tmp.conf", "test", false, 10, "test", false, false)
+	err := CreateConfFile("config_test/tmp.conf", testPw, false, 10, "test", false, false)
 	if err != nil {
 		t.Fatal(err)
 	}
-	_, c, err := LoadConfFile("config_test/tmp.conf", "test")
+	_, c, err := LoadConfFile("config_test/tmp.conf", testPw)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -81,18 +83,18 @@ func TestCreateConfDefault(t *testing.T) {
 }
 
 func TestCreateConfDevRandom(t *testing.T) {
-	err := CreateConfFile("config_test/tmp.conf", "test", false, 10, "test", false, true)
+	err := CreateConfFile("config_test/tmp.conf", testPw, false, 10, "test", false, true)
 	if err != nil {
 		t.Fatal(err)
 	}
 }
 
 func TestCreateConfPlaintextnames(t *testing.T) {
-	err := CreateConfFile("config_test/tmp.conf", "test", true, 10, "test", false, false)
+	err := CreateConfFile("config_test/tmp.conf", testPw, true, 10, "test", false, false)
 	if err != nil {
 		t.Fatal(err)
 	}
-	_, c, err := LoadConfFile("config_test/tmp.conf", "test")
+	_, c, err := LoadConfFile("config_test/tmp.conf", testPw)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -109,11 +111,11 @@ func TestCreateConfPlaintextnames(t *testing.T) {
 
 // Reverse mode uses AESSIV
 func TestCreateConfFileAESSIV(t *testing.T) {
-	err := CreateConfFile("config_test/tmp.conf", "test", false, 10, "test", true, false)
+	err := CreateConfFile("config_test/tmp.conf", testPw, false, 10, "test", true, false)
 	if err != nil {
 		t.Fatal(err)
 	}
-	_, c, err := LoadConfFile("config_test/tmp.conf", "test")
+	_, c, err := LoadConfFile("config_test/tmp.conf", testPw)
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/internal/configfile/scrypt.go b/internal/configfile/scrypt.go
index b5a3edb..a1caf06 100644
--- a/internal/configfile/scrypt.go
+++ b/internal/configfile/scrypt.go
@@ -61,10 +61,10 @@ func NewScryptKDF(logN int) ScryptKDF {
 }
 
 // DeriveKey returns a new key from a supplied password.
-func (s *ScryptKDF) DeriveKey(pw string) []byte {
+func (s *ScryptKDF) DeriveKey(pw []byte) []byte {
 	s.validateParams()
 
-	k, err := scrypt.Key([]byte(pw), s.Salt, s.N, s.R, s.P, s.KeyLen)
+	k, err := scrypt.Key(pw, s.Salt, s.N, s.R, s.P, s.KeyLen)
 	if err != nil {
 		log.Panicf("DeriveKey failed: %v", err)
 	}
diff --git a/internal/configfile/scrypt_test.go b/internal/configfile/scrypt_test.go
index c1a656a..8f7a5c8 100644
--- a/internal/configfile/scrypt_test.go
+++ b/internal/configfile/scrypt_test.go
@@ -23,7 +23,7 @@ ok  	github.com/rfjakob/gocryptfs/cryptfs	18.772s
 func benchmarkScryptN(n int, b *testing.B) {
 	kdf := NewScryptKDF(n)
 	for i := 0; i < b.N; i++ {
-		kdf.DeriveKey("test")
+		kdf.DeriveKey(testPw)
 	}
 }
 
diff --git a/internal/readpassword/extpass_test.go b/internal/readpassword/extpass_test.go
index 4af775a..cdfea4e 100644
--- a/internal/readpassword/extpass_test.go
+++ b/internal/readpassword/extpass_test.go
@@ -8,6 +8,8 @@ import (
 	"github.com/rfjakob/gocryptfs/internal/tlog"
 )
 
+var testPw = []byte("test")
+
 func TestMain(m *testing.M) {
 	// Shut up info output
 	tlog.Info.Enabled = false
@@ -16,7 +18,7 @@ func TestMain(m *testing.M) {
 
 func TestExtpass(t *testing.T) {
 	p1 := "ads2q4tw41reg52"
-	p2 := readPasswordExtpass("echo " + p1)
+	p2 := string(readPasswordExtpass("echo " + p1))
 	if p1 != p2 {
 		t.Errorf("p1=%q != p2=%q", p1, p2)
 	}
@@ -24,7 +26,7 @@ func TestExtpass(t *testing.T) {
 
 func TestOnceExtpass(t *testing.T) {
 	p1 := "lkadsf0923rdfi48rqwhdsf"
-	p2 := Once("echo " + p1)
+	p2 := string(Once("echo " + p1))
 	if p1 != p2 {
 		t.Errorf("p1=%q != p2=%q", p1, p2)
 	}
@@ -32,7 +34,7 @@ func TestOnceExtpass(t *testing.T) {
 
 func TestTwiceExtpass(t *testing.T) {
 	p1 := "w5w44t3wfe45srz434"
-	p2 := Once("echo " + p1)
+	p2 := string(Once("echo " + p1))
 	if p1 != p2 {
 		t.Errorf("p1=%q != p2=%q", p1, p2)
 	}
diff --git a/internal/readpassword/read.go b/internal/readpassword/read.go
index 481911b..047eba9 100644
--- a/internal/readpassword/read.go
+++ b/internal/readpassword/read.go
@@ -2,6 +2,7 @@
 package readpassword
 
 import (
+	"bytes"
 	"fmt"
 	"io"
 	"os"
@@ -23,7 +24,7 @@ const (
 
 // Once tries to get a password from the user, either from the terminal, extpass
 // or stdin.
-func Once(extpass string) string {
+func Once(extpass string) []byte {
 	if extpass != "" {
 		return readPasswordExtpass(extpass)
 	}
@@ -35,7 +36,7 @@ func Once(extpass string) string {
 
 // Twice is the same as Once but will prompt twice if we get the password from
 // the terminal.
-func Twice(extpass string) string {
+func Twice(extpass string) []byte {
 	if extpass != "" {
 		return readPasswordExtpass(extpass)
 	}
@@ -44,7 +45,7 @@ func Twice(extpass string) string {
 	}
 	p1 := readPasswordTerminal("Password: ")
 	p2 := readPasswordTerminal("Repeat: ")
-	if p1 != p2 {
+	if !bytes.Equal(p1, p2) {
 		tlog.Fatal.Println("Passwords do not match")
 		os.Exit(exitcodes.ReadPassword)
 	}
@@ -53,7 +54,7 @@ func Twice(extpass string) string {
 
 // readPasswordTerminal reads a line from the terminal.
 // Exits on read error or empty result.
-func readPasswordTerminal(prompt string) string {
+func readPasswordTerminal(prompt string) []byte {
 	fd := int(os.Stdin.Fd())
 	fmt.Fprintf(os.Stderr, prompt)
 	// terminal.ReadPassword removes the trailing newline
@@ -67,12 +68,12 @@ func readPasswordTerminal(prompt string) string {
 		tlog.Fatal.Println("Password is empty")
 		os.Exit(exitcodes.PasswordEmpty)
 	}
-	return string(p)
+	return p
 }
 
 // readPasswordStdin reads a line from stdin.
 // It exits with a fatal error on read error or empty result.
-func readPasswordStdin() string {
+func readPasswordStdin() []byte {
 	tlog.Info.Println("Reading password from stdin")
 	p := readLineUnbuffered(os.Stdin)
 	if len(p) == 0 {
@@ -85,7 +86,7 @@ func readPasswordStdin() string {
 // readPasswordExtpass executes the "extpass" program and returns the first line
 // of the output.
 // Exits on read error or empty result.
-func readPasswordExtpass(extpass string) string {
+func readPasswordExtpass(extpass string) []byte {
 	tlog.Info.Println("Reading password from extpass program")
 	var parts []string
 	// The option "-passfile=FILE" gets transformed to
@@ -125,7 +126,7 @@ func readPasswordExtpass(extpass string) string {
 
 // readLineUnbuffered reads single bytes from "r" util it gets "\n" or EOF.
 // The returned string does NOT contain the trailing "\n".
-func readLineUnbuffered(r io.Reader) (l string) {
+func readLineUnbuffered(r io.Reader) (l []byte) {
 	b := make([]byte, 1)
 	for {
 		if len(l) > maxPasswordLen {
@@ -146,7 +147,7 @@ func readLineUnbuffered(r io.Reader) (l string) {
 		if b[0] == '\n' {
 			return l
 		}
-		l = l + string(b)
+		l = append(l, b...)
 	}
 }
 
diff --git a/internal/readpassword/stdin_test.go b/internal/readpassword/stdin_test.go
index 2d9f93f..8cf9954 100644
--- a/internal/readpassword/stdin_test.go
+++ b/internal/readpassword/stdin_test.go
@@ -11,7 +11,7 @@ import (
 func TestStdin(t *testing.T) {
 	p1 := "g55434t55wef"
 	if os.Getenv("TEST_SLAVE") == "1" {
-		p2 := readPasswordStdin()
+		p2 := string(readPasswordStdin())
 		if p1 != p2 {
 			fmt.Fprintf(os.Stderr, "%q != %q", p1, p2)
 			os.Exit(1)
@@ -44,7 +44,7 @@ func TestStdin(t *testing.T) {
 func TestStdinEof(t *testing.T) {
 	p1 := "asd45as5f4a36"
 	if os.Getenv("TEST_SLAVE") == "1" {
-		p2 := readPasswordStdin()
+		p2 := string(readPasswordStdin())
 		if p1 != p2 {
 			fmt.Fprintf(os.Stderr, "%q != %q", p1, p2)
 			os.Exit(1)