Cloak/internal/util/util.go
2019-06-10 00:03:28 +10:00

103 lines
2.5 KiB
Go

package util
import (
"crypto/aes"
"crypto/cipher"
"encoding/binary"
"errors"
"io"
prand "math/rand"
"net"
"strconv"
)
func AESGCMEncrypt(nonce []byte, key []byte, plaintext []byte) ([]byte, error) {
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
aesgcm, err := cipher.NewGCM(block)
if err != nil {
return nil, err
}
return aesgcm.Seal(nil, nonce, plaintext, nil), nil
}
func AESGCMDecrypt(nonce []byte, key []byte, ciphertext []byte) ([]byte, error) {
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
aesgcm, err := cipher.NewGCM(block)
if err != nil {
return nil, err
}
plain, err := aesgcm.Open(nil, nonce, ciphertext, nil)
if err != nil {
return nil, err
}
return plain, nil
}
// PsudoRandBytes returns a byte slice filled with psudorandom bytes generated by the seed
func PsudoRandBytes(length int, seed int64) []byte {
r := prand.New(prand.NewSource(seed))
ret := make([]byte, length)
r.Read(ret)
return ret
}
// ReadTLS reads TLS data according to its record layer
func ReadTLS(conn net.Conn, buffer []byte) (n int, err error) {
// TCP is a stream. Multiple TLS messages can arrive at the same time,
// a single message can also be segmented due to MTU of the IP layer.
// This function guareentees a single TLS message to be read and everything
// else is left in the buffer.
i, err := io.ReadFull(conn, buffer[:5])
if err != nil {
return
}
dataLength := int(binary.BigEndian.Uint16(buffer[3:5]))
if dataLength > len(buffer) {
err = errors.New("Reading TLS message: message size greater than buffer. message size: " + strconv.Itoa(dataLength))
return
}
left := dataLength
readPtr := 5
for left != 0 {
// If left > buffer size (i.e. our message got segmented), the entire MTU is read
// if left = buffer size, the entire buffer is all there left to read
// if left < buffer size (i.e. multiple messages came together),
// only the message we want is read
i, err = io.ReadFull(conn, buffer[readPtr:readPtr+left])
if err != nil {
return
}
left -= i
readPtr += i
}
n = 5 + dataLength
return
}
// AddRecordLayer adds record layer to data
func AddRecordLayer(input []byte, typ []byte, ver []byte) []byte {
length := make([]byte, 2)
binary.BigEndian.PutUint16(length, uint16(len(input)))
ret := make([]byte, 5+len(input))
copy(ret[0:1], typ)
copy(ret[1:3], ver)
copy(ret[3:5], length)
copy(ret[5:], input)
return ret
}
// PeelRecordLayer peels off the record layer
func PeelRecordLayer(data []byte) []byte {
ret := data[5:]
return ret
}