simplesCriptoFile.go

/**
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.##.................##....##..##..##....##......
..######......#######.....##..##..##....######..
.......##...........##....##..##..##....##......
.##....##....##.....##....##..##..##....##......
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*
* S3WF Framework - golang
*
* Framework desenvolvido por @jeffotoni
*
* @package		golang/pkg
* @author		@jeffotoni
* @copyright	Copyright (c) 2007 - 2017
* @license		http://s3wf.com.br/
* @link			http://s3wf.com.br
* @since		Version 1.0
* @filesource
*/
// ---------------------------------------------------------------------
//

package main

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/base32"
	"encoding/base64"
	"errors"
	"fmt"
	"io"
	"os"
)

func check(e error) {
	if e != nil {
		panic(e)
	}
}

func getToken(length int) string {

	randomBytes := make([]byte, 256)
	_, err := rand.Read(randomBytes)
	if err != nil {
		panic(err)
	}

	return base32.StdEncoding.EncodeToString(randomBytes)[:length]
}

func main() {

	///gerando chave dinamicamente de 32 bytes
	tokenKey := getToken(32)
	key := []byte(tokenKey) // 32 bytes

	fmt.Println("chave utilizada para criptografar: ", tokenKey)

	///abrindo arquivo exemplo...
	file, _ := os.Open("jad1.pdf") // For read access.

	///pegando o tamanho em bytes do file..
	fi, _ := file.Stat()
	data := make([]byte, 16*fi.Size())
	count, _ := file.Read(data)

	file_copy, _ := os.Create("jad1-copy.pdf.crypt")
	defer file_copy.Close()

	ciphertext, _ := sCryptAes(key, data[:count])
	//fmt.Println(err_c)

	///gravando arquivo cryptografado
	file_copy.Write(ciphertext)

	fmt.Println("Arquivo [jad1-copy.pdf.crypt] criado e cryptografado")

	file_cry, _ := os.Open("jad1-copy.pdf.crypt") // For read access.

	///pegando o tamanho em bytes do file..
	ficry, _ := file_cry.Stat()

	data_cry := make([]byte, ficry.Size())

	count_cry, _ := file_cry.Read(data_cry)

	file_copy_cry, _ := os.Create("jad1-copy.pdf")

	defer file_copy_cry.Close()

	data_descry, _ := sDesCryptAes(key, data_cry[:count_cry])

	file_copy_cry.Write(data_descry)

	fmt.Println("Arquivo [jad1-copy.pdf] criado e descriptografado")

	//
	/////////FIM
	///
	os.Exit(0)
}

// See alternate IV creation from ciphertext below
//var iv = []byte{35, 46, 57, 24, 85, 35, 24, 74, 87, 35, 88, 98, 66, 32, 14, 05}

func sCryptAes(key, text []byte) ([]byte, error) {

	block, err := aes.NewCipher(key)

	if err != nil {
		return nil, err
	}

	b := base64.StdEncoding.EncodeToString(text)
	ciphertext := make([]byte, aes.BlockSize+len(b))

	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(b))

	return ciphertext, nil
}

func sDesCryptAes(key, text []byte) ([]byte, error) {

	block, err := aes.NewCipher(key)

	if err != nil {
		return nil, err
	}

	if len(text) < aes.BlockSize {
		return nil, errors.New("muito pequena a cifra do texto")
	}
	iv := text[:aes.BlockSize]
	text = text[aes.BlockSize:]

	cfb := cipher.NewCFBDecrypter(block, iv)
	cfb.XORKeyStream(text, text)
	data, err := base64.StdEncoding.DecodeString(string(text))

	if err != nil {
		return nil, err
	}

	return data, nil
}