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145 lines
3.3 KiB
Go
145 lines
3.3 KiB
Go
package main
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import (
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"bufio"
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"crypto/aes"
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"crypto/cipher"
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"crypto/rand"
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"encoding/base64"
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"errors"
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"flag"
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"fmt"
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"io"
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"io/ioutil"
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"log"
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"os"
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)
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func check(err error) {
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if err != nil {
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log.Fatal(err)
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}
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}
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const chunkName = "crPt"
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var inputFile string
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var outputFile string
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var imageFile string
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var decryptImage bool
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func main() {
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flag.StringVar(&imageFile, "image", "image.png", "The path of the png file.")
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flag.BoolVar(&decryptImage, "decrypt", false, "If the input image should be decrypted.")
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flag.StringVar(&outputFile, "out", "out.png", "The output file for the encrypted/decrypted data.")
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flag.StringVar(&inputFile, "in", "input.txt","The file with the input data.")
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flag.Parse()
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if decryptImage {
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f, err := os.Open(imageFile)
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check(err)
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defer f.Close()
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check(err)
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fout, err := os.Create(outputFile)
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check(err)
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defer fout.Close()
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DecryptDataPng(f, fout)
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} else {
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f, err := os.Open(imageFile)
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check(err)
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defer f.Close()
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check(err)
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fout, err := os.Create(outputFile)
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check(err)
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defer fout.Close()
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fin, err := os.Open(inputFile)
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check(err)
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defer fin.Close()
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EncryptDataPng(f, fin, fout)
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}
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}
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func EncryptDataPng(f *os.File, fin *os.File, fout *os.File) {
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png := PngData{}
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err := png.Read(f)
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check(err)
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inputData, err := ioutil.ReadAll(fin)
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check(err)
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inputData, err = encryptData(inputData)
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check(err)
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cryptChunk := CreateChunk(inputData, chunkName)
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png.AddMetaChunk(cryptChunk)
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err = png.Write(fout)
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check(err)
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}
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// Decrypts the data from a png file
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func DecryptDataPng(f *os.File, fout *os.File) {
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png := PngData{}
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err := png.Read(f)
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check(err)
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cryptChunk := png.GetChunk(chunkName)
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if cryptChunk != nil {
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data, err := decryptData(cryptChunk.data)
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check(err)
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_, err = fout.Write(data)
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check(err)
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} else {
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log.Fatal("no encrypted data inside the input image")
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}
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}
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// creates an encrypted png chunk
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func encryptData(data []byte) ([]byte, error) {
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reader := bufio.NewReader(os.Stdin)
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fmt.Print("Password: ")
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pw, _ := reader.ReadString('\n')
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key := make([]byte, 32 - len(pw))
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key = append(key, []byte(pw)...)
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return encrypt(key, data)
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}
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func decryptData(data []byte) ([]byte, error) {
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reader := bufio.NewReader(os.Stdin)
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fmt.Print("Password: ")
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pw, _ := reader.ReadString('\n')
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key := make([]byte, 32 - len(pw))
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key = append(key, []byte(pw)...)
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return decrypt(key, data)
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}
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// encrypt and decrypt functions taken from
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// https://stackoverflow.com/questions/18817336/golang-encrypting-a-string-with-aes-and-base64
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func encrypt(key, text []byte) ([]byte, error) {
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block, err := aes.NewCipher(key)
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if err != nil {
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return nil, err
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}
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b := base64.StdEncoding.EncodeToString(text)
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cipherText := make([]byte, aes.BlockSize+len(b))
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iv := cipherText[:aes.BlockSize]
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if _, err := io.ReadFull(rand.Reader, iv); err != nil {
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return nil, err
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}
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cfb := cipher.NewCFBEncrypter(block, iv)
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cfb.XORKeyStream(cipherText[aes.BlockSize:], []byte(b))
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return cipherText, nil
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}
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func decrypt(key, text []byte) ([]byte, error) {
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block, err := aes.NewCipher(key)
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if err != nil {
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return nil, err
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}
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if len(text) < aes.BlockSize {
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return nil, errors.New("ciphertext too short")
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}
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iv := text[:aes.BlockSize]
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text = text[aes.BlockSize:]
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cfb := cipher.NewCFBDecrypter(block, iv)
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cfb.XORKeyStream(text, text)
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data, err := base64.StdEncoding.DecodeString(string(text))
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if err != nil {
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return nil, err
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}
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return data, nil
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} |