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package inform
import (
"bytes"
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"encoding/hex"
"errors"
)
func Pad(src []byte, blockSize int) []byte {
padLen := blockSize - (len(src) % blockSize)
padText := bytes.Repeat([]byte{byte(padLen)}, padLen)
return append(src, padText...)
}
func Unpad(src []byte, blockSize int) ([]byte, error) {
srcLen := len(src)
paddingLen := int(src[srcLen-1])
if paddingLen >= srcLen || paddingLen > blockSize {
return nil, errors.New("Padding size error")
}
return src[:srcLen-paddingLen], nil
}
func decodeHexKey(key string) (cipher.Block, error) {
decodedKey, err := hex.DecodeString(key)
if err != nil {
return nil, err
}
block, err := aes.NewCipher(decodedKey)
if err != nil {
return nil, err
}
return block, nil
}
func makeAESIV() ([]byte, error) {
iv := make([]byte, 16)
if _, err := rand.Read(iv); err != nil {
return nil, err
}
return iv, nil
}
// Returns ciphertext and IV, does not modify payload
func Encrypt(payload []byte, key string) ([]byte, []byte, error) {
ct := make([]byte, len(payload))
copy(ct, payload)
ct = Pad(ct, aes.BlockSize)
iv, err := makeAESIV()
if err != nil {
return nil, nil, err
}
block, err := decodeHexKey(key)
if err != nil {
return nil, nil, err
}
mode := cipher.NewCBCEncrypter(block, iv)
mode.CryptBlocks(ct, ct)
return ct, iv, nil
}
func Decrypt(payload, iv []byte, key string) ([]byte, error) {
b := make([]byte, len(payload))
block, err := decodeHexKey(key)
if err != nil {
return nil, err
}
mode := cipher.NewCBCDecrypter(block, iv)
mode.CryptBlocks(b, payload)
u, err := Unpad(b, aes.BlockSize)
if err != nil {
return nil, err
}
return u, nil
}
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