Golang StreamReader Sample

cipher.streamreader.go

package main

import (
	"bytes"
	"crypto/aes"
	"crypto/cipher"
	"fmt"
	"io"
	"math"
)

var (
	AESKEY = []byte{
		0xE6, 0x9A, 0xB4, 0xE9, 0x9B, 0xAA, 0xE5, 0x98,
		0x89, 0xE5, 0xB9, 0xB4, 0xE5, 0x8D, 0x8E, 0x81,
	}
	AesBlockCipher, _ = aes.NewCipher(AESKEY)
)

func main() {
	var res string = `{ "ret": 0, "msg": "", "content": { "dcdn_switch": "1" } }`

	dst := make([]byte, 16)
	AesBlockCipher.Encrypt(dst, []byte(res))
	fmt.Printf("First block enc: %x\n", dst)

	numBlocks := int(math.Ceil(float64(len(res)) / aes.BlockSize))
	obf := bytes.NewBuffer(make([]byte, 0, numBlocks*aes.BlockSize))
	obf.WriteString(res)
	obf.Write(make([]byte, numBlocks*aes.BlockSize-obf.Len()))

	fmt.Printf("origin: %x\n", obf.Bytes())
	input := obf
	var iv [aes.BlockSize]byte
	stream := cipher.NewOFB(AesBlockCipher, iv[:])

	// encryptedBytes := make([]byte, 0, numBlocks*aes.BlockSize)
	// of, _ := os.OpenFile("encrypted-file", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
	// defer of.Close()
	output := bytes.NewBuffer(nil)
	streamWriter := &cipher.StreamWriter{S: stream, W: output}
	io.Copy(streamWriter, input)
	fmt.Printf("enc: %x\n len = %d\n", output.Bytes(), len(output.Bytes()))

	d_input := bytes.NewReader(output.Bytes())
	d_stream := cipher.NewOFB(AesBlockCipher, iv[:])
	d_output := bytes.NewBuffer(nil)
	streamReader := &cipher.StreamReader{S: d_stream, R: d_input}
	io.Copy(d_output, streamReader)
	fmt.Printf("dec: %x\n len = %d\n", d_output.Bytes(), len(d_output.Bytes()))
	fmt.Printf("plain: %s\n", d_output.Bytes())
}