func read_stego(img io.Reader, secret string, out io.Writer) {
// see if encryption is used or not
var encrypt bool = false
var crypt *rc4.Cipher
if secret != "" {
encrypt = true
var err error
crypt, err = rc4.NewCipher([]byte(secret))
if err != nil {
panic(err)
}
// when the function is finished, zero the keyspace
defer crypt.Reset()
}
// get a buffer to read data from the image
buf := make([]byte, 128)
// create the stego img reader to read the data
stegoReader, err := stegoimg.NewStegoImgReader(img)
if err != nil {
panic(err)
}
// read and decrypt the data
for {
// read the new data block
n, err := stegoReader.Read(buf)
if err != nil && err != io.EOF {
panic(err)
}
// break if no data was read
if n == 0 {
break
}
// optionally decrypt
if encrypt {
crypt.XORKeyStream(buf[:n], buf[:n])
}
// write to the stego writer
_, writeErr := out.Write(buf[:n])
if writeErr != nil {
panic(writeErr)
}
// break if that's the end of the data
if err == io.EOF {
break
}
}
return
}
func (p *protectType) uValueGen() (v []byte) {
var c *rc4.Cipher
c, _ = rc4.NewCipher(p.encryptionKey)
cap := len(p.padding)
v = make([]byte, cap, cap)
c.XORKeyStream(v, p.padding)
return
}
func oValueGen(userPass, ownerPass []byte) (v []byte) {
var c *rc4.Cipher
tmp := md5.Sum(ownerPass)
c, _ = rc4.NewCipher(tmp[0:5])
cap := len(userPass)
v = make([]byte, cap, cap)
c.XORKeyStream(v, userPass)
return
}
func rc4(cipher *rc4P.Cipher, ciphertext []byte) []byte {
result := make([]byte, len(ciphertext))
cipher.XORKeyStream(result, ciphertext)
return result
}
func write_stego(img, data io.Reader, secret string, out io.Writer) {
// see if encryption is used or not
var encrypt bool = false
var crypt *rc4.Cipher
if secret != "" {
encrypt = true
var err error
crypt, err = rc4.NewCipher([]byte(secret))
if err != nil {
panic(err)
}
// when the function is finished, zero the keyspace
defer crypt.Reset()
}
// get a buffer to read data from the data
buf := make([]byte, 128)
// create the new stego img writer to encode the data
stegoWriter, err := stegoimg.NewStegoImgWriter(img, out)
if err != nil {
panic(err)
}
defer stegoWriter.Close()
// read and encode the data
for {
// read the new data block
n, err := data.Read(buf)
if err != nil && err != io.EOF {
panic(err)
}
// break if no data was read
if n == 0 {
break
}
// optionally encrypt
if encrypt {
crypt.XORKeyStream(buf[:n], buf[:n])
}
// write to the stego writer
_, writeErr := stegoWriter.Write(buf[:n])
// check if the image filled up
if writeErr == stegoimg.ImageFullError && err != io.EOF {
fmt.Println("Image full before data finished")
break
}
// break if that's the end of the data
if err == io.EOF {
break
}
}
// finished creating the image
return
}
func makeSeedMessage(maxPadding int, seed []byte, clientToServerCipher *rc4.Cipher) ([]byte, error) {
// paddingLength is integer in range [0, maxPadding]
paddingLength, err := MakeSecureRandomInt(maxPadding + 1)
if err != nil {
return nil, ContextError(err)
}
padding, err := MakeSecureRandomBytes(paddingLength)
if err != nil {
return nil, ContextError(err)
}
buffer := new(bytes.Buffer)
err = binary.Write(buffer, binary.BigEndian, seed)
if err != nil {
return nil, ContextError(err)
}
err = binary.Write(buffer, binary.BigEndian, uint32(OBFUSCATE_MAGIC_VALUE))
if err != nil {
return nil, ContextError(err)
}
err = binary.Write(buffer, binary.BigEndian, uint32(paddingLength))
if err != nil {
return nil, ContextError(err)
}
err = binary.Write(buffer, binary.BigEndian, padding)
if err != nil {
return nil, ContextError(err)
}
seedMessage := buffer.Bytes()
clientToServerCipher.XORKeyStream(seedMessage[len(seed):], seedMessage[len(seed):])
return seedMessage, nil
}