FileEncryptor.go

package main

/*
Copyright 2018 TheRedSpy15

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
limitations under the License.
*/

// TODO: document
// Code copied from (will be changing to be in my own code!) :
// https://www.thepolyglotdeveloper.com/2018/02/encrypt-decrypt-data-golang-application-crypto-packages/

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/md5"
	"crypto/rand"
	"encoding/hex"
	"io"
	"io/ioutil"
	"os"

	"github.com/daviddengcn/go-colortext"
)

func createHash(key string) string {
	hasher := md5.New()
	hasher.Write([]byte(key))
	return hex.EncodeToString(hasher.Sum(nil))
}

func encrypt(data []byte, passphrase string) []byte {
	block, _ := aes.NewCipher([]byte(createHash(passphrase)))
	gcm, err := cipher.NewGCM(block)
	if err != nil {
		ct.Foreground(ct.Red, true)
		panic(err.Error())
	}
	nonce := make([]byte, gcm.NonceSize())
	if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
		ct.Foreground(ct.Red, true)
		panic(err.Error())
	}
	ciphertext := gcm.Seal(nonce, nonce, data, nil)
	return ciphertext
}

func encryptFile(filename string, data []byte, passphrase string) {
	f, err := os.Create(filename)
	if err != nil {
		ct.Foreground(ct.Red, true)
		panic(err.Error())
	}
	defer f.Close()
	f.Write(encrypt(data, passphrase))
}

func decrypt(data []byte, passphrase string) []byte {
	key := []byte(createHash(passphrase))
	block, err := aes.NewCipher(key)
	if err != nil {
		ct.Foreground(ct.Red, true)
		panic(err.Error())
	}
	gcm, err := cipher.NewGCM(block)
	if err != nil {
		ct.Foreground(ct.Red, true)
		panic(err.Error())
	}
	nonceSize := gcm.NonceSize()
	nonce, ciphertext := data[:nonceSize], data[nonceSize:]
	plaintext, err := gcm.Open(nil, nonce, ciphertext, nil)
	if err != nil {
		ct.Foreground(ct.Red, true)
		panic(err.Error())
	}
	return plaintext
}

func decryptFile(filename string, passphrase string) []byte {
	data, err := ioutil.ReadFile(filename)
	if err != nil {
		ct.Foreground(ct.Red, true)
		panic(err.Error())
	}

	return decrypt(data, passphrase)
}