mirror of
https://github.com/emmansun/gmsm.git
synced 2025-04-24 19:26:18 +08:00
78 lines
1.9 KiB
Go
78 lines
1.9 KiB
Go
//go:build (amd64 && !generic) || (arm64 && !generic)
|
|
// +build amd64,!generic arm64,!generic
|
|
|
|
package sm4
|
|
|
|
import (
|
|
"crypto/cipher"
|
|
|
|
"github.com/emmansun/gmsm/internal/subtle"
|
|
"github.com/emmansun/gmsm/internal/xor"
|
|
)
|
|
|
|
// Assert that sm4CipherAsm implements the cbcDecAble interfaces.
|
|
var _ cbcDecAble = (*sm4CipherAsm)(nil)
|
|
|
|
type cbc struct {
|
|
b *sm4CipherAsm
|
|
iv []byte
|
|
tmp []byte
|
|
}
|
|
|
|
func (b *sm4CipherAsm) NewCBCDecrypter(iv []byte) cipher.BlockMode {
|
|
var c cbc
|
|
c.b = b
|
|
c.iv = make([]byte, BlockSize)
|
|
c.tmp = make([]byte, BlockSize)
|
|
copy(c.iv, iv)
|
|
return &c
|
|
}
|
|
|
|
func (x *cbc) BlockSize() int { return BlockSize }
|
|
|
|
func (x *cbc) CryptBlocks(dst, src []byte) {
|
|
if len(src)%BlockSize != 0 {
|
|
panic("cipher: input not full blocks")
|
|
}
|
|
if len(dst) < len(src) {
|
|
panic("cipher: output smaller than input")
|
|
}
|
|
if subtle.InexactOverlap(dst[:len(src)], src) {
|
|
panic("cipher: invalid buffer overlap")
|
|
}
|
|
if len(src) == 0 {
|
|
return
|
|
}
|
|
end := len(src)
|
|
copy(x.tmp, src[end-BlockSize:end])
|
|
start := end - x.b.blocksSize
|
|
var temp []byte = make([]byte, x.b.blocksSize)
|
|
var batchSrc []byte = make([]byte, x.b.blocksSize)
|
|
for start > 0 {
|
|
x.b.DecryptBlocks(temp, src[start:end])
|
|
for i := 0; i < x.b.batchBlocks; i++ {
|
|
xor.XorBytes(dst[end-(i+1)*BlockSize:end-i*BlockSize], temp[x.b.blocksSize-(i+1)*BlockSize:x.b.blocksSize-i*BlockSize], src[end-(i+2)*BlockSize:end-(i+1)*BlockSize])
|
|
}
|
|
end = start
|
|
start -= x.b.blocksSize
|
|
}
|
|
|
|
copy(batchSrc, src[:end])
|
|
x.b.DecryptBlocks(temp, batchSrc)
|
|
count := end / BlockSize
|
|
for i := count; i > 1; i-- {
|
|
xor.XorBytes(dst[end-BlockSize:end], temp[end-BlockSize:end], src[end-2*BlockSize:end-BlockSize])
|
|
end -= BlockSize
|
|
}
|
|
xor.XorBytes(dst[0:end], temp[0:end], x.iv[:])
|
|
// Set the new iv to the first block we copied earlier.
|
|
x.iv, x.tmp = x.tmp, x.iv
|
|
}
|
|
|
|
func (x *cbc) SetIV(iv []byte) {
|
|
if len(iv) != BlockSize {
|
|
panic("cipher: incorrect length IV")
|
|
}
|
|
copy(x.iv[:], iv)
|
|
}
|