Golang - Drag and Drop AES Encryption and Decryption

drop_encrypt.go

package main

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"
)

func decrypt(cipherstring string, keystring string) string {
	// Byte array of the string
	ciphertext := []byte(cipherstring)

	// Key
	key := []byte(keystring)

	// Create the AES cipher
	block, err := aes.NewCipher(key)
	if err != nil {
		panic(err)
	}

	// Before even testing the decryption,
	// if the text is too small, then it is incorrect
	if len(ciphertext) < aes.BlockSize {
		panic("Text is too short")
	}

	// Get the 16 byte IV
	iv := ciphertext[:aes.BlockSize]

	// Remove the IV from the ciphertext
	ciphertext = ciphertext[aes.BlockSize:]

	// Return a decrypted stream
	stream := cipher.NewCFBDecrypter(block, iv)

	// Decrypt bytes from ciphertext
	stream.XORKeyStream(ciphertext, ciphertext)

	return string(ciphertext)
}

func encrypt(plainstring, keystring string) string {
	// Byte array of the string
	plaintext := []byte(plainstring)

	// Key
	key := []byte(keystring)

	// Create the AES cipher
	block, err := aes.NewCipher(key)
	if err != nil {
		panic(err)
	}

	// Empty array of 16 + plaintext length
	// Include the IV at the beginning
	ciphertext := make([]byte, aes.BlockSize+len(plaintext))

	// Slice of first 16 bytes
	iv := ciphertext[:aes.BlockSize]

	// Write 16 rand bytes to fill iv
	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		panic(err)
	}

	// Return an encrypted stream
	stream := cipher.NewCFBEncrypter(block, iv)

	// Encrypt bytes from plaintext to ciphertext
	stream.XORKeyStream(ciphertext[aes.BlockSize:], plaintext)

	return string(ciphertext)
}

func writeToFile(data, file string) {
	ioutil.WriteFile(file, []byte(data), 777)
}

func readFromFile(file string) ([]byte, error) {
	data, err := ioutil.ReadFile(file)
	return data, err
}

func waitForKey() {
	fmt.Print("\nPlease Enter to continue...")
	var buf [1]byte
	os.Stdin.Read(buf[:])
}

func isFile(file string) bool {
	if s, err := os.Stat(file); s.IsDir() || err != nil {
		return false
	}

	return true
}

func main() {

	if len(os.Args) != 2 {
		fmt.Println("You must drag and drop a file!")
		waitForKey()
		os.Exit(1)
	} else if !isFile(os.Args[1]) {
		fmt.Println("File does not exist!")
		waitForKey()
		os.Exit(1)
	}

	file := os.Args[1]
	key := "testtesttesttest"

	if strings.ToLower(filepath.Ext(file)) != ".enc" {
		content, err := readFromFile(file)
		if err != nil {
			fmt.Println(err)
			waitForKey()
			os.Exit(1)
		}
		encrypted := encrypt(string(content), key)
		writeToFile(encrypted, file+".enc")
	} else {
		content, err := readFromFile(file)
		if err != nil {
			fmt.Println(err)
			waitForKey()
			os.Exit(1)
		}
		decrypted := decrypt(string(content), key)
		writeToFile(decrypted, file[:len(file)-4])
	}
}

Hi Joseph,
I'm working on a project that use AES to encrypt strings for network communication.
Following Google, I found your code (encrypt and decrypt function for more specific) above, and it work like a charm :)
But, as there is no license attached, I want to make sure I can actually use it on my project (planned for BSD License).
Could you make the License information more clear please?

Whoops, sorry, just saw this. Feel free to use it without a license.

I keep getting an exit status 1 after dropping a file and pressing enter how do I avoid this.