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util.go
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util.go
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package crypto
import (
"bytes"
"crypto/cipher"
"crypto/rand"
"errors"
"io"
"strings"
)
var badCiphertextError error = errors.New("bad ciphertext")
var illegalArgumentError error = errors.New("Illegal Argument")
var notMultipleBlockError error = errors.New("ciphertext is not a multiple of the block size")
var badKeySizeError error = errors.New("error key size")
func srcPadding(name string, src []byte, blockSize int) []byte {
padLen := blockSize
if len(src)%blockSize != 0 {
padLen = blockSize - len(src)%blockSize
}
return append(src, appPadding(name, padLen)...)
}
// 补位算法
// name 算法,len 补位长度
func appPadding(name string, l int) []byte {
switch strings.ToLower(name) {
case "pkcs5", "pkcs7", "pkcs5padding", "pkcs7padding":
return bytes.Repeat([]byte{byte(l)}, l)
case "iso10126", "iso10126padding":
return func() []byte {
rb := make([]byte, l)
rand.Read(rb)
rb[l-1] = byte(l)
return rb
}()
case "ansix923":
return func() []byte {
rb := make([]byte, l)
rb[l-1] = byte(l)
return rb
}()
case "zeros", "zerospadding":
return make([]byte, l)
}
return nil
}
// 移除补位
func unPadding(name string, src []byte) ([]byte, error) {
switch strings.ToLower(name) {
case "pkcs5", "pkcs7", "pkcs5padding", "pkcs7padding", "iso10126", "iso10126padding", "ansix923":
return func() ([]byte, error) {
l := len(src)
last := int(src[l-1])
if last > l {
return nil, errors.New("padding error")
}
return src[:(l - last)], nil
}()
case "zeros", "zerospadding":
return func() ([]byte, error) {
for {
if src[len(src)-1] != 0 {
break
}
src = src[:len(src)-1]
}
return src, nil
}()
}
return nil, errors.New("unsupport padding")
}
func genIV(s int) ([]byte, error) {
iv := make([]byte, s)
if _, err := io.ReadFull(rand.Reader, iv); err != nil {
return nil, err
}
return iv, nil
}
func ecbEnc(block cipher.Block, key, src []byte, padding string) ([]byte, error) {
src = srcPadding(padding, src, block.BlockSize())
dst := make([]byte, 0)
tmp := make([]byte, block.BlockSize())
for len(src) > 0 {
block.Encrypt(tmp, src[:block.BlockSize()])
src = src[block.BlockSize():]
dst = append(dst, tmp...)
}
return dst, nil
}
func ecbDec(block cipher.Block, key, src []byte, padding string) ([]byte, error) {
if len(src)%block.BlockSize() != 0 {
return nil, notMultipleBlockError
}
// if len(src) <= block.BlockSize() {
// return nil, badCiphertextError
// }
dst := make([]byte, 0)
tmp := make([]byte, block.BlockSize())
for len(src) > 0 {
block.Decrypt(tmp, src[:block.BlockSize()])
src = src[block.BlockSize():]
dst = append(dst, tmp...)
}
return unPadding(padding, dst)
}
// cfb 加密
func cfbEnc(block cipher.Block, key, iv, src []byte, padding string) ([]byte, error) {
src = srcPadding(padding, src, block.BlockSize())
dst := make([]byte, len(src))
cipher.NewCFBEncrypter(block, iv).XORKeyStream(dst, src)
return dst, nil
}
// cfb 解密
func cfbDec(block cipher.Block, key, iv, src []byte, padding string) ([]byte, error) {
dst := make([]byte, len(src))
cipher.NewCFBDecrypter(block, iv).XORKeyStream(dst, src)
return dst, nil
}
// cbc 加密需要补位
func cbcEnc(block cipher.Block, key, iv, src []byte, padding string) ([]byte, error) {
src = srcPadding(padding, src, block.BlockSize())
dst := make([]byte, len(src))
cipher.NewCBCEncrypter(block, iv).CryptBlocks(dst, src)
return dst, nil
}
// cbc 解密后需要去掉补位
func cbcDec(block cipher.Block, key, iv, src []byte, padding string) ([]byte, error) {
if len(src)%block.BlockSize() != 0 {
return nil, notMultipleBlockError
}
dst := make([]byte, len(src))
cipher.NewCBCDecrypter(block, iv).CryptBlocks(dst, src)
return unPadding(padding, dst)
}
func ctrEnc(block cipher.Block, key, iv, src []byte) ([]byte, error) {
dst := make([]byte, len(src))
cipher.NewCTR(block, iv).XORKeyStream(dst, src)
return dst, nil
}
func ctrDec(block cipher.Block, key, iv, src []byte) ([]byte, error) {
return ctrEnc(block, key, iv, src)
}
func ofbEnc(block cipher.Block, key, iv, src []byte, padding string) ([]byte, error) {
src = srcPadding(padding, src, block.BlockSize())
dst := make([]byte, len(src))
cipher.NewOFB(block, iv).XORKeyStream(dst, src)
return dst, nil
}
func ofbDec(block cipher.Block, key, iv, src []byte, padding string) ([]byte, error) {
return ofbEnc(block, key, iv, src, "nopadding")
}
func MakeRandByte(l int) []byte {
b := make([]byte, l)
rand.Read(b)
return b
}