cipher: use new functions

cipher/bc.go

@@ -3,6 +3,7 @@
 package cipher
 
 import (
+	"bytes"
 	_cipher "crypto/cipher"
 
 	"github.com/emmansun/gmsm/internal/subtle"
@@ -15,13 +16,11 @@ type bc struct {
 }
 
 func newBC(b _cipher.Block, iv []byte) *bc {
-	c := &bc{
+	return &bc{
 		b:         b,
 		blockSize: b.BlockSize(),
-		iv:        make([]byte, b.BlockSize()),
+		iv:        bytes.Clone(iv),
 	}
-	copy(c.iv, iv)
-	return c
 }
 
 type bcEncrypter bc

cipher/ccm.go

@@ -239,9 +239,7 @@ func (c *ccm) Open(dst, nonce, ciphertext, data []byte) ([]byte, error) {
 		// so overwrites dst in the event of a tag mismatch. That
 		// behavior is mimicked here in order to be consistent across
 		// platforms.
-		for i := range out {
-			out[i] = 0
-		}
+		clear(out)
 		return nil, errOpen
 	}
 	return ret, nil

cipher/ofbnlf.go

@@ -4,6 +4,7 @@
 package cipher
 
 import (
+	"bytes"
 	_cipher "crypto/cipher"
 	"errors"
 )
@@ -28,8 +29,8 @@ func newOFBNLF(cipherFunc CipherCreator, key, iv []byte) (*ofbnlf, error) {
 	if len(iv) != c.blockSize {
 		return nil, errors.New("cipher: IV length must equal block size")
 	}
-	c.iv = make([]byte, c.blockSize)
-	copy(c.iv, iv)
+	c.iv = bytes.Clone(iv)
+	
 	return c, nil
 }
 

cipher/xts_generic.go

@@ -8,7 +8,7 @@ func mul2(tweak *[blockSize]byte, isGB bool) {
 
 func doubleTweaks(tweak *[blockSize]byte, tweaks []byte, isGB bool) {
 	count := len(tweaks) >> 4
-	for i := 0; i < count; i++ {
+	for i := range count {
 		copy(tweaks[blockSize*i:], tweak[:])
 		mul2(tweak, isGB)
 	}