functions.go

package main

import (
        "crypto/aes"
        "crypto/cipher"
        "crypto/rand"
        "crypto/sha256"
        "encoding/hex"
        "fmt"
        "github.com/gotk3/gotk3/gtk"
        "io"
        "io/ioutil"
        "log"
        "os"
        "os/exec"
        "path/filepath"
        "strings"
)

// Check for errors.
func check(e error) {
        if e != nil {
                log.Fatal(e)
                panic(e)
        }
}

// Handle updating status label.
func updatestatus(statustext string, statuslabel *gtk.Label) {
        statuslabel.SetText(statustext)
        for gtk.EventsPending() {
                gtk.MainIteration()
        }
}

// Handle encrypting files.
func encryptfile(filename string, s string, progressbar *gtk.ProgressBar, statuslabel *gtk.Label, hintlabel *gtk.Label, image *gtk.Image) {
        // Check if user pressed cancel button.
        if filename == "" {
                return
        }

        // Update progress bar.
        progressbar.SetFraction(0.0)
        image.SetFromFile("./Assets/working2.gif")

        // Get basename and remove extension.
        basename := filepath.Base(filename)
        name := strings.TrimSuffix(basename, filepath.Ext(basename))

        // Make a temporary zip file.
        updatestatus("Status: Compressing...", statuslabel)
        fi, err := os.Stat(filename)
        var cmd *exec.Cmd
        check(err)
        switch mode := fi.Mode(); {
        case mode.IsDir():
                cmd = exec.Command("zip", "-j", "-r", "nekotemp.zip", filename)
        case mode.IsRegular():
                cmd = exec.Command("zip", "-j", "nekotemp.zip", filename)
        }
        cmd.Run()

        // Update progress bar.
        progressbar.SetFraction(0.4)

        // Read temporary zip file bytes.
        dat, _ := ioutil.ReadFile("nekotemp.zip")

        // Create key hash from password.
        updatestatus("Status: Generating key hash...", statuslabel)
        h := sha256.New()
        h.Write([]byte(s))

        // Update progress bar.
        progressbar.SetFraction(0.5)

        // Convert key to string.
        key := hex.EncodeToString(h.Sum(nil))

        // Encrypt data.
        updatestatus("Status: Encrypting...", statuslabel)
        encrypted := encrypt(dat, key)

        // Write output data to file.
        updatestatus("Status: Writing output to file...", statuslabel)
        f, err := os.OpenFile(filepath.Dir(filename)+"/"+name+".neko", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
        check(err)
        defer f.Close()
        f.WriteString(encrypted)

        // Delete temporary zip file.
        updatestatus("Status: Cleaning up...", statuslabel)
        os.Remove("nekotemp.zip")

        // Update progress bar.
        progressbar.SetFraction(1.0)
        updatestatus("Status: Done", statuslabel)
        hintlabel.SetText("The file/folder was successfully encrypted.")
        image.SetFromFile("./Assets/success.gif")
}

// Handle decrypting files.
func decryptfile(filename string, s string, progressbar *gtk.ProgressBar, statuslabel *gtk.Label, hintlabel *gtk.Label, image *gtk.Image) {
        // Check if user pressed cancel button.
        if filename == "" {
                return
        }

        // Update progress bar.
        progressbar.SetFraction(0.0)
        image.SetFromFile("./Assets/working2.gif")

        // Read input file bytes.
        updatestatus("Status: Reading file to decrypt...", statuslabel)
        dat, _ := ioutil.ReadFile(filename)

        // Update progress bar.
        progressbar.SetFraction(0.1)

        // Create key hash from password.
        updatestatus("Status: Generating key hash...", statuslabel)
        h := sha256.New()
        h.Write([]byte(s))

        // Update progress bar.
        progressbar.SetFraction(0.4)

        // Convert key to string.
        key := hex.EncodeToString(h.Sum(nil))

        // Decrypt data.
        updatestatus("Status: Decrypting...", statuslabel)
        decrypted := decrypt(dat, key)

        // Write data to temporary zip file.
        updatestatus("Status: Writing output to temporary file...", statuslabel)
        f, err := os.OpenFile("nekotemp.zip", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
        check(err)
        defer f.Close()
        f.WriteString(decrypted)

        // Update progress bar.
        progressbar.SetFraction(0.5)

        // Unzip temporary zip file into directory of input file.
        updatestatus("Status: Decompressing...", statuslabel)
        cmd := exec.Command("unzip", "nekotemp.zip", "-d", filepath.Dir(filename))
        cmd.Run()

        // Delete temporary zip file.
        updatestatus("Status: Cleaning up...", statuslabel)
        os.Remove("nekotemp.zip")

        // Update progress bar.
        progressbar.SetFraction(1.0)
        updatestatus("Status: Done", statuslabel)
        hintlabel.SetText("The file/folder was successfully decrypted.")
        image.SetFromFile("./Assets/success.gif")
}

// Handle encrypting data.
func encrypt(plaintext []byte, keyString string) (encryptedString string) {

        //Since the key is in string, we need to convert decode it to bytes
        key, _ := hex.DecodeString(keyString)

        //Create a new Cipher Block from the key
        block, err := aes.NewCipher(key)
        check(err)

        //Create a new GCM - https://en.wikipedia.org/wiki/Galois/Counter_Mode
        //https://golang.org/pkg/crypto/cipher/#NewGCM
        aesGCM, err := cipher.NewGCM(block)
        check(err)

        //Create a nonce. Nonce should be from GCM
        nonce := make([]byte, aesGCM.NonceSize())
        if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
                panic(err.Error())
        }

        //Encrypt the data using aesGCM.Seal
        //Since we don't want to save the nonce somewhere else in this case, we add it as a prefix to the encrypted data. The first nonce argument in Seal is the prefix.
        ciphertext := aesGCM.Seal(nonce, nonce, plaintext, nil)
        return fmt.Sprintf("%s", ciphertext)
}

// Handle decrypting data.
func decrypt(enc []byte, keyString string) (decryptedString string) {

        key, _ := hex.DecodeString(keyString)

        //Create a new Cipher Block from the key
        block, err := aes.NewCipher(key)
        check(err)

        //Create a new GCM
        aesGCM, err := cipher.NewGCM(block)
        check(err)

        //Get the nonce size
        nonceSize := aesGCM.NonceSize()

        //Extract the nonce from the encrypted data
        nonce, ciphertext := enc[:nonceSize], enc[nonceSize:]

        //Decrypt the data
        plaintext, err := aesGCM.Open(nil, nonce, ciphertext, nil)
        check(err)

        return fmt.Sprintf("%s", plaintext)
}