package main

import (
	"bytes"
	"crypto/aes"
	"crypto/cipher"
	"encoding/hex"
	"fmt"
)

func main() {
	var key = "1234567887654321"
	var vector = "8765432112345678"
	var info = "AES in CFB mode"

	Enc_str := EncryptAES_CFB(info, key, vector)
	fmt.Println(Enc_str)
	Dec_str := DecryptAES_CFB(Enc_str, key, vector)
	fmt.Println(Dec_str)
}

func EncryptAES_CFB(src, key, vector string) string {
	data := []byte(src)
	iv := []byte(vector)
	keyByte := []byte(key)
	block, err := aes.NewCipher(keyByte)
	if err != nil {
		panic(err)
	}
	data = PKCS5Padding(data, block.BlockSize())
	ciphertext := make([]byte, len(data))
	mode := cipher.NewCFBEncrypter(block, iv)
	mode.XORKeyStream(ciphertext, data)
	return fmt.Sprintf("%X", ciphertext)
}

func DecryptAES_CFB(src, key, vector string) string {
	keyByte := []byte(key)
	iv := []byte(vector)
	data, err := hex.DecodeString(src)
	if err != nil {
		panic(err)
	}
	block, err := aes.NewCipher(keyByte)
	if err != nil {
		panic(err)
	}
	plaintext := make([]byte, len(data))
	mode := cipher.NewCFBDecrypter(block, iv)
	mode.XORKeyStream(plaintext, data)
	plaintext = PKCS5UnPadding(plaintext)
	return string(plaintext)
}

func PKCS5Padding(ciphertext []byte, blockSize int) []byte {
	padding := blockSize - len(ciphertext)%blockSize
	padtext := bytes.Repeat([]byte{byte(padding)}, padding)
	return append(ciphertext, padtext...)
}
func PKCS5UnPadding(origData []byte) []byte {
	length := len(origData)
	unpadding := int(origData[length-1])
	return origData[:(length - unpadding)]
}