Merge pull request #1395 from restic/small-crypto-improvements

Small improvements

internal/crypto/crypto_int_test.go

@@ -67,21 +67,40 @@ var testValues = []struct {
 	plaintext  []byte
 }{
 	{
-		ekey: EncryptionKey([...]byte{
-			0x30, 0x3e, 0x86, 0x87, 0xb1, 0xd7, 0xdb, 0x18, 0x42, 0x1b, 0xdc, 0x6b, 0xb8, 0x58, 0x8c, 0xca,
-			0xda, 0xc4, 0xd5, 0x9e, 0xe8, 0x7b, 0x8f, 0xf7, 0x0c, 0x44, 0xe6, 0x35, 0x79, 0x0c, 0xaf, 0xef,
-		}),
+		ekey: decodeArray32("303e8687b1d7db18421bdc6bb8588ccadac4d59ee87b8ff70c44e635790cafef"),
 		skey: MACKey{
-			K: [...]byte{0xef, 0x4d, 0x88, 0x24, 0xcb, 0x80, 0xb2, 0xbc, 0xc5, 0xfb, 0xff, 0x8a, 0x9b, 0x12, 0xa4, 0x2c},
-			R: [...]byte{0xcc, 0x8d, 0x4b, 0x94, 0x8e, 0xe0, 0xeb, 0xfe, 0x1d, 0x41, 0x5d, 0xe9, 0x21, 0xd1, 0x03, 0x53},
+			K: decodeArray16("ef4d8824cb80b2bcc5fbff8a9b12a42c"),
+			R: decodeArray16("cc8d4b948ee0ebfe1d415de921d10353"),
 		},
 		ciphertext: decodeHex("69fb41c62d12def4593bd71757138606338f621aeaeb39da0fe4f99233f8037a54ea63338a813bcf3f75d8c3cc75dddf8750"),
 		plaintext:  []byte("Dies ist ein Test!"),
 	},
 }
 
+func decodeArray16(s string) (dst [16]byte) {
+	data := decodeHex(s)
+	if len(data) != 16 {
+		panic("data has wrong length")
+	}
+	copy(dst[:], data)
+	return
+}
+
+func decodeArray32(s string) (dst [32]byte) {
+	data := decodeHex(s)
+	if len(data) != 32 {
+		panic("data has wrong length")
+	}
+	copy(dst[:], data)
+	return
+}
+
+// decodeHex decodes the string s and panics on error.
 func decodeHex(s string) []byte {
-	d, _ := hex.DecodeString(s)
+	d, err := hex.DecodeString(s)
+	if err != nil {
+		panic(err)
+	}
 	return d
 }
 

internal/crypto/kdf.go

@@ -12,22 +12,22 @@ import (
 
 const saltLength = 64
 
-// KDFParams are the default parameters used for the key derivation function KDF().
-type KDFParams struct {
+// Params are the default parameters used for the key derivation function KDF().
+type Params struct {
 	N int
 	R int
 	P int
 }
 
 // DefaultKDFParams are the default parameters used for Calibrate and KDF().
-var DefaultKDFParams = KDFParams{
+var DefaultKDFParams = Params{
 	N: sscrypt.DefaultParams.N,
 	R: sscrypt.DefaultParams.R,
 	P: sscrypt.DefaultParams.P,
 }
 
 // Calibrate determines new KDF parameters for the current hardware.
-func Calibrate(timeout time.Duration, memory int) (KDFParams, error) {
+func Calibrate(timeout time.Duration, memory int) (Params, error) {
 	defaultParams := sscrypt.Params{
 		N:       DefaultKDFParams.N,
 		R:       DefaultKDFParams.R,
@@ -41,7 +41,7 @@ func Calibrate(timeout time.Duration, memory int) (KDFParams, error) {
 		return DefaultKDFParams, errors.Wrap(err, "scrypt.Calibrate")
 	}
 
-	return KDFParams{
+	return Params{
 		N: params.N,
 		R: params.R,
 		P: params.P,
@@ -50,7 +50,7 @@ func Calibrate(timeout time.Duration, memory int) (KDFParams, error) {
 
 // KDF derives encryption and message authentication keys from the password
 // using the supplied parameters N, R and P and the Salt.
-func KDF(p KDFParams, salt []byte, password string) (*Key, error) {
+func KDF(p Params, salt []byte, password string) (*Key, error) {
 	if len(salt) != saltLength {
 		return nil, errors.Errorf("scrypt() called with invalid salt bytes (len %d)", len(salt))
 	}

internal/repository/key.go

@@ -44,9 +44,9 @@ type Key struct {
 	name string
 }
 
-// KDFParams tracks the parameters used for the KDF. If not set, it will be
+// Params tracks the parameters used for the KDF. If not set, it will be
 // calibrated on the first run of AddKey().
-var KDFParams *crypto.KDFParams
+var Params *crypto.Params
 
 var (
 	// KDFTimeout specifies the maximum runtime for the KDF.
@@ -76,7 +76,7 @@ func OpenKey(ctx context.Context, s *Repository, name string, password string) (
 	}
 
 	// derive user key
-	params := crypto.KDFParams{
+	params := crypto.Params{
 		N: k.N,
 		R: k.R,
 		P: k.P,
@@ -166,13 +166,13 @@ func LoadKey(ctx context.Context, s *Repository, name string) (k *Key, err error
 // AddKey adds a new key to an already existing repository.
 func AddKey(ctx context.Context, s *Repository, password string, template *crypto.Key) (*Key, error) {
 	// make sure we have valid KDF parameters
-	if KDFParams == nil {
+	if Params == nil {
 		p, err := crypto.Calibrate(KDFTimeout, KDFMemory)
 		if err != nil {
 			return nil, errors.Wrap(err, "Calibrate")
 		}
 
-		KDFParams = &p
+		Params = &p
 		debug.Log("calibrated KDF parameters are %v", p)
 	}
 
@@ -180,9 +180,9 @@ func AddKey(ctx context.Context, s *Repository, password string, template *crypt
 	newkey := &Key{
 		Created: time.Now(),
 		KDF:     "scrypt",
-		N:       KDFParams.N,
-		R:       KDFParams.R,
-		P:       KDFParams.P,
+		N:       Params.N,
+		R:       Params.R,
+		P:       Params.P,
 	}
 
 	hn, err := os.Hostname()
@@ -202,7 +202,7 @@ func AddKey(ctx context.Context, s *Repository, password string, template *crypt
 	}
 
 	// call KDF to derive user key
-	newkey.user, err = crypto.KDF(*KDFParams, newkey.Salt, password)
+	newkey.user, err = crypto.KDF(*Params, newkey.Salt, password)
 	if err != nil {
 		return nil, err
 	}

internal/repository/testing.go

@@ -15,7 +15,7 @@ import (
 )
 
 // testKDFParams are the parameters for the KDF to be used during testing.
-var testKDFParams = crypto.KDFParams{
+var testKDFParams = crypto.Params{
 	N: 128,
 	R: 1,
 	P: 1,
@@ -28,7 +28,7 @@ type logger interface {
 // TestUseLowSecurityKDFParameters configures low-security KDF parameters for testing.
 func TestUseLowSecurityKDFParameters(t logger) {
 	t.Logf("using low-security KDF parameters for test")
-	KDFParams = &testKDFParams
+	Params = &testKDFParams
 }
 
 // TestBackend returns a fully configured in-memory backend.