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