Move KDF() to kdf.go

src/restic/crypto/crypto.go

@@ -9,7 +9,6 @@ import (
 	"fmt"
 
 	"golang.org/x/crypto/poly1305"
-	"golang.org/x/crypto/scrypt"
 )
 
 const (
@@ -315,34 +314,6 @@ func Decrypt(ks *Key, plaintext []byte, ciphertextWithMac []byte) ([]byte, error
 	return plaintext, nil
 }
 
-// KDF derives encryption and message authentication keys from the password
-// using the supplied parameters N, R and P and the Salt.
-func KDF(N, R, P int, salt []byte, password string) (*Key, error) {
-	if len(salt) == 0 {
-		return nil, fmt.Errorf("scrypt() called with empty salt")
-	}
-
-	derKeys := &Key{}
-
-	keybytes := macKeySize + aesKeySize
-	scryptKeys, err := scrypt.Key([]byte(password), salt, N, R, P, keybytes)
-	if err != nil {
-		return nil, fmt.Errorf("error deriving keys from password: %v", err)
-	}
-
-	if len(scryptKeys) != keybytes {
-		return nil, fmt.Errorf("invalid numbers of bytes expanded from scrypt(): %d", len(scryptKeys))
-	}
-
-	// first 32 byte of scrypt output is the encryption key
-	copy(derKeys.Encrypt[:], scryptKeys[:aesKeySize])
-
-	// next 32 byte of scrypt output is the mac key, in the form k||r
-	macKeyFromSlice(&derKeys.MAC, scryptKeys[aesKeySize:])
-
-	return derKeys, nil
-}
-
 // Valid tests if the key is valid.
 func (k *Key) Valid() bool {
 	return k.Encrypt.Valid() && k.MAC.Valid()

src/restic/crypto/kdf.go

@@ -0,0 +1,35 @@
+package crypto
+
+import (
+	"fmt"
+
+	"golang.org/x/crypto/scrypt"
+)
+
+// KDF derives encryption and message authentication keys from the password
+// using the supplied parameters N, R and P and the Salt.
+func KDF(N, R, P int, salt []byte, password string) (*Key, error) {
+	if len(salt) == 0 {
+		return nil, fmt.Errorf("scrypt() called with empty salt")
+	}
+
+	derKeys := &Key{}
+
+	keybytes := macKeySize + aesKeySize
+	scryptKeys, err := scrypt.Key([]byte(password), salt, N, R, P, keybytes)
+	if err != nil {
+		return nil, fmt.Errorf("error deriving keys from password: %v", err)
+	}
+
+	if len(scryptKeys) != keybytes {
+		return nil, fmt.Errorf("invalid numbers of bytes expanded from scrypt(): %d", len(scryptKeys))
+	}
+
+	// first 32 byte of scrypt output is the encryption key
+	copy(derKeys.Encrypt[:], scryptKeys[:aesKeySize])
+
+	// next 32 byte of scrypt output is the mac key, in the form k||r
+	macKeyFromSlice(&derKeys.MAC, scryptKeys[aesKeySize:])
+
+	return derKeys, nil
+}