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// Copyright 2019 syncd Author. All Rights Reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.
// license at https://github.com/snail007/goproxy/blob/master/LICENSE
package goaes
import (
"bytes"
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"errors"
"io"
)
func Encrypt(key []byte, text []byte) ([]byte, error) {
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
msg := pad(text)
ciphertext := make([]byte, aes.BlockSize+len(msg))
iv := ciphertext[:aes.BlockSize]
if _, err := io.ReadFull(rand.Reader, iv); err != nil {
return nil, err
}
cfb := cipher.NewCFBEncrypter(block, iv)
cfb.XORKeyStream(ciphertext[aes.BlockSize:], []byte(msg))
return ciphertext, nil
}
func Decrypt(key []byte, text []byte) ([]byte, error) {
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
if (len(text) % aes.BlockSize) != 0 {
return nil, errors.New("blocksize must be multipe of decoded message length")
}
iv := text[:aes.BlockSize]
msg := text[aes.BlockSize:]
cfb := cipher.NewCFBDecrypter(block, iv)
cfb.XORKeyStream(msg, msg)
unpadMsg, err := unpad(msg)
if err != nil {
return nil, err
}
return unpadMsg, nil
}
func pad(src []byte) []byte {
padding := aes.BlockSize - len(src)%aes.BlockSize
padtext := bytes.Repeat([]byte{byte(padding)}, padding)
return append(src, padtext...)
}
func unpad(src []byte) ([]byte, error) {
length := len(src)
unpadding := int(src[length-1])
if unpadding > length {
return nil, errors.New("unpad error. This could happen when incorrect encryption key is used")
}
return src[:(length - unpadding)], nil
}
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