aes wrap

main.go

package main

import (
	"bytes"
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/base64"
	"fmt"
)

// Appends padding.
func pkcs7Pad(data []byte, blocklen int) ([]byte, error) {
	if blocklen <= 0 {
		return nil, fmt.Errorf("invalid blocklen %d", blocklen)
	}
	padlen := 1
	for ((len(data) + padlen) % blocklen) != 0 {
		padlen = padlen + 1
	}

	pad := bytes.Repeat([]byte{byte(padlen)}, padlen)
	return append(data, pad...), nil
}

func main() {
	key := []byte("cfcfcfcfcfcfcfcfcfcfcfcfcfcfcfcf")
	originalText := []byte("{\"token\":\"Token\",\"limit\":\"1000\"}")

	data, err := GenerateRandomBytes(8)
	if err != nil {
		fmt.Println(err)
	}
	data = append(data, originalText...)

	block, err := aes.NewCipher(key)
	if err != nil {
		panic(err)
	}

	padded, err := pkcs7Pad(data, block.BlockSize())

	encrypted := make([]byte, len(padded))

	iv := padded[:block.BlockSize()] // const BlockSize = 8

	mode := cipher.NewCBCEncrypter(block, iv)
	mode.CryptBlocks(encrypted, padded)

	fmt.Println(base64.RawStdEncoding.EncodeToString(encrypted))

}

// GenerateRandomBytes returns securely generated random bytes.
// It will return an error if the system's secure random
// number generator fails to function correctly, in which
// case the caller should not continue.
func GenerateRandomBytes(n int) ([]byte, error) {
	b := make([]byte, n)
	_, err := rand.Read(b)
	// Note that err == nil only if we read len(b) bytes.
	if err != nil {
		return nil, err
	}

	return b, nil
}