aes.go

package aes

import (
	"bytes"
	"crypto/aes"
	"crypto/cipher"
)

func CBCEncrypt(origData, key, iv []byte) ([]byte, error) {
	if len(iv) == 0 {
		iv = key
	}
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}
	blockSize := block.BlockSize()
	origData = Pkcs7Padding(origData, blockSize)
	blockMode := cipher.NewCBCEncrypter(block, iv[:blockSize])
	crypted := make([]byte, len(origData))
	blockMode.CryptBlocks(crypted, origData)
	return crypted, nil
}

func CBCDecrypt(crypted, key, iv []byte) ([]byte, error) {
	if len(iv) == 0 {
		iv = key
	}

	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}
	blockSize := block.BlockSize()
	blockMode := cipher.NewCBCDecrypter(block, iv[:blockSize])
	origData := make([]byte, len(crypted))
	blockMode.CryptBlocks(origData, crypted)
	origData = UnPadding(origData)
	return origData, nil
}

func Pkcs7Padding(cipherText []byte, blockSize int) []byte {
	padding := blockSize - len(cipherText)%blockSize
	padText := bytes.Repeat([]byte{byte(padding)}, padding)
	return append(cipherText, padText...)
}

func UnPadding(origData []byte) []byte {
	length := len(origData)
	if length == 0 {
		return origData
	}
	// 去掉最后一个字节 unpadding 次
	unPadding := int(origData[length-1])
	//解密去补码时需取最后一个字节，值为m，则从数据尾部删除m个字节，剩余数据即为加密前的原文
	return origData[:(length - unPadding)]
}

func Pkcs5Padding(cipherText []byte, blockSize int) []byte {
	return Pkcs7Padding(cipherText, 8)
}

func ECBEncrypt(data, key []byte) ([]byte, error) {
	cipher, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}
	blockSize := cipher.BlockSize()
	origData := Pkcs7Padding(data, blockSize)
	ecb := NewECBEncrypter(cipher)
	crypted := make([]byte, len(origData))
	ecb.CryptBlocks(crypted, origData)
	return crypted, nil
}

func ECBDecrypt(crypted, key []byte) ([]byte, error) {
	cipher, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}
	blockMode := NewECBDecrypter(cipher)
	origData := make([]byte, len(crypted)-len(crypted)%cipher.BlockSize())
	blockMode.CryptBlocks(origData, crypted)
	origData = UnPadding(origData)
	return origData, nil
}

type ecb struct {
	b         cipher.Block
	blockSize int
}

func newECB(b cipher.Block) *ecb {
	return &ecb{
		b:         b,
		blockSize: b.BlockSize(),
	}
}

type ecbEncrypter ecb

// NewECBEncrypter returns a BlockMode which encrypts in electronic code book
// mode, using the given Block.
func NewECBEncrypter(b cipher.Block) cipher.BlockMode {
	return (*ecbEncrypter)(newECB(b))
}
func (x *ecbEncrypter) BlockSize() int { return x.blockSize }
func (x *ecbEncrypter) CryptBlocks(dst, src []byte) {
	if len(src)%x.blockSize != 0 {
		panic("crypto/cipher: input not full blocks")
	}
	if len(dst) < len(src) {
		panic("crypto/cipher: output smaller than input")
	}
	for len(src) > 0 {
		x.b.Encrypt(dst, src[:x.blockSize])
		src = src[x.blockSize:]
		dst = dst[x.blockSize:]
	}
}

type ecbDecrypter ecb

// NewECBDecrypter returns a BlockMode which decrypts in electronic code book
// mode, using the given Block
func NewECBDecrypter(b cipher.Block) cipher.BlockMode {
	return (*ecbDecrypter)(newECB(b))
}
func (x *ecbDecrypter) BlockSize() int { return x.blockSize }
func (x *ecbDecrypter) CryptBlocks(dst, src []byte) {
	/*	if len(src)%x.blockSize != 0 {
			panic("crypto/cipher: input not full blocks")
		}
		if len(dst) < len(src) {
			panic("crypto/cipher: output smaller than input")
		}*/
	for len(src) >= x.blockSize {
		x.b.Decrypt(dst, src[:x.blockSize])
		src = src[x.blockSize:]
		dst = dst[x.blockSize:]
	}
}