init: v1.0.0

sm/sm4/mac.go

@@ -0,0 +1,58 @@
+package sm4
+
+import (
+	"crypto/cipher"
+
+	"xdx.jelly/xgcl/gerrors"
+)
+
+// Mac 使用SM4CBC加密计算MAC值。即最后一个分组
+// 多包的话多次调用即可：data = data1 || data2 || ...
+// out = mac(key, iv, data1)
+// out = mac(key, out, data2)
+// ......
+// MAC内不会对输入key, iv, data作任何改动
+func Mac(key, iv, data []byte) ([]byte, error) {
+	if len(data) < 4096 {
+		return mac(key, iv, data)
+	}
+	return macSmallMem(key, iv, data)
+}
+
+// mac make a copy of iv and data, waste a lot of memeory if data is big.
+// A little faster.
+func mac(key, iv, data []byte) ([]byte, error) {
+	dst := make([]byte, len(data)) // dst alloc on stack, for large data
+	iv2 := make([]byte, BlockSize) // iv2 escape, alloc on heap
+	copy(iv2, iv)
+
+	dst, err := EncryptCBC(dst, iv2, key, data) // assume EncryptCBC not change input iv2
+	if err != nil {
+		return []byte{}, nil
+	}
+	copy(iv2, dst[len(dst)-BlockSize:])
+	return iv2, nil
+}
+
+// macSmallMem for small memeory, local var are only two blocks
+func macSmallMem(key, iv, data []byte) ([]byte, error) {
+	block, err := NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	dst := make([]byte, block.BlockSize()) // dst alloc on stack, for large data
+	iv2 := make([]byte, block.BlockSize()) //
+	copy(iv2, iv)
+
+	blockMode := cipher.NewCBCEncrypter(block, iv2)
+	src := data
+	for len(src) >= block.BlockSize() {
+		blockMode.CryptBlocks(dst, src[:BlockSize])
+		src = src[BlockSize:]
+	}
+	if len(src) > 0 {
+		return nil, gerrors.WithAnnotatingf(ErrSM4MacFailed, "padding first, input length must be multiple of %d", BlockSize)
+	}
+	return dst, nil
+
+}