data.go

/*
This file is part of Assemble Web Chat.

Assemble Web Chat is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Assemble Web Chat is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Assemble Web Chat.  If not, see <http://www.gnu.org/licenses/>.
*/
package utils

import (
	"bytes"
	"compress/zlib"
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/base64"
	"errors"
	"io"
)

func Encrypt(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 Decrypt(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("ciphertext too short")
	}
	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
}

func Compress(data []byte) bytes.Buffer {
	var b bytes.Buffer
	w := zlib.NewWriter(&b)
	w.Write(data)
	w.Close()
	return b
}

func Uncompress(data []byte) (bytes.Buffer, error) {
	var buf bytes.Buffer
	buf.Write(data)

	var unb bytes.Buffer
	r, err := zlib.NewReader(&buf)
	if err != nil {
		return unb, err
	}
	io.Copy(&unb, r)
	r.Close()
	return unb, nil
}