Cloak/internal/util/obfs.go
2018-10-14 20:32:54 +01:00

71 lines
2.0 KiB
Go

package util
import (
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"encoding/binary"
"io"
mux "github.com/cbeuw/Cloak/internal/multiplex"
)
func AESEncrypt(iv []byte, key []byte, plaintext []byte) []byte {
block, _ := aes.NewCipher(key)
ciphertext := make([]byte, len(plaintext))
stream := cipher.NewCTR(block, iv)
stream.XORKeyStream(ciphertext, plaintext)
return ciphertext
}
func AESDecrypt(iv []byte, key []byte, ciphertext []byte) []byte {
ret := make([]byte, len(ciphertext))
copy(ret, ciphertext) // Because XORKeyStream is inplace, but we don't want the input to be changed
block, _ := aes.NewCipher(key)
stream := cipher.NewCTR(block, iv)
stream.XORKeyStream(ret, ret)
return ret
}
func MakeObfs(key []byte) func(*mux.Frame) []byte {
obfs := func(f *mux.Frame) []byte {
header := make([]byte, 12)
binary.BigEndian.PutUint32(header[0:4], f.StreamID)
binary.BigEndian.PutUint32(header[4:8], f.Seq)
binary.BigEndian.PutUint32(header[8:12], f.ClosingStreamID)
// header: [StreamID 4 bytes][Seq 4 bytes][ClosingStreamID 4 bytes]
iv := make([]byte, 16)
io.ReadFull(rand.Reader, iv)
cipherheader := AESEncrypt(iv, key, header)
obfsed := make([]byte, len(f.Payload)+12+16)
copy(obfsed[0:16], iv)
copy(obfsed[16:28], cipherheader)
copy(obfsed[28:], f.Payload)
// obfsed: [iv 16 bytes][cipherheader 12 bytes][payload]
ret := AddRecordLayer(obfsed, []byte{0x17}, []byte{0x03, 0x03})
return ret
}
return obfs
}
func MakeDeobfs(key []byte) func([]byte) *mux.Frame {
deobfs := func(in []byte) *mux.Frame {
peeled := PeelRecordLayer(in)
header := AESDecrypt(peeled[0:16], key, peeled[16:28])
streamID := binary.BigEndian.Uint32(header[0:4])
seq := binary.BigEndian.Uint32(header[4:8])
closingStreamID := binary.BigEndian.Uint32(header[8:12])
payload := make([]byte, len(peeled)-12-16)
//log.Printf("Payload: %x\n", payload)
copy(payload, peeled[28:])
ret := &mux.Frame{
StreamID: streamID,
Seq: seq,
ClosingStreamID: closingStreamID,
Payload: payload,
}
return ret
}
return deobfs
}