1 files changed, 38 insertions, 6 deletions
diff --git a/crypto/rand.go b/crypto/rand.go
index 0778ebd..527f841 100644
--- a/crypto/rand.go
+++ b/crypto/rand.go
@@ -30,7 +30,8 @@ import (
 // the operating system has insufficient randomness, the buffer creation will
 // fail. This is an improvement over Go's built-in crypto/rand which will still
 // return bytes if the system has insufficiency entropy.
-// 	See: https://github.com/golang/go/issues/19274
+//
+//	See: https://github.com/golang/go/issues/19274
 //
 // While this syscall was only introduced in Kernel v3.17, it predates the
 // introduction of filesystem encryption, so it introduces no additional
@@ -44,11 +45,43 @@ func NewRandomBuffer(length int) ([]byte, error) {
 }
 
 // NewRandomKey creates a random key of the specified length. This function uses
-// the same random number generation process a NewRandomBuffer.
+// the same random number generation process as NewRandomBuffer.
 func NewRandomKey(length int) (*Key, error) {
 	return NewFixedLengthKeyFromReader(randReader{}, length)
 }
 
+// NewRandomPassphrase creates a random passphrase of the specified length
+// containing random alphabetic characters.
+func NewRandomPassphrase(length int) (*Key, error) {
+	chars := []byte("abcdefghijklmnopqrstuvwxyz")
+	passphrase, err := NewBlankKey(length)
+	if err != nil {
+		return nil, err
+	}
+	for i := 0; i < length; {
+		// Get some random bytes.
+		raw, err := NewRandomKey((length - i) * 2)
+		if err != nil {
+			return nil, err
+		}
+		// Translate the random bytes into random characters.
+		for _, b := range raw.data {
+			if int(b) >= 256-(256%len(chars)) {
+				// Avoid bias towards the first characters in the list.
+				continue
+			}
+			c := chars[int(b)%len(chars)]
+			passphrase.data[i] = c
+			i++
+			if i == length {
+				break
+			}
+		}
+		raw.Wipe()
+	}
+	return passphrase, nil
+}
+
 // randReader just calls into Getrandom, so no internal data is needed.
 type randReader struct{}
 
@@ -58,10 +91,9 @@ func (r randReader) Read(buffer []byte) (int, error) {
 	case nil:
 		return n, nil
 	case unix.EAGAIN:
-		return 0, errors.Wrap(ErrGetrandomFail, "insufficient entropy in pool")
+		err = errors.New("insufficient entropy in pool")
 	case unix.ENOSYS:
-		return 0, errors.Wrap(ErrGetrandomFail, "kernel must be v3.17 or later")
-	default:
-		return 0, errors.Wrap(ErrGetrandomFail, err.Error())
+		err = errors.New("kernel must be v3.17 or later")
 	}
+	return 0, errors.Wrap(err, "getrandom() failed")
 }