Big rewrite tutk proto support

pkg/xiaomi/crypto/crypto.go

@@ -0,0 +1,68 @@
+package crypto
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+
+	"golang.org/x/crypto/chacha20"
+	"golang.org/x/crypto/nacl/box"
+)
+
+func GenerateKey() ([]byte, []byte, error) {
+	public, private, err := box.GenerateKey(rand.Reader)
+	if err != nil {
+		return nil, nil, err
+	}
+	return public[:], private[:], err
+}
+
+func CalcSharedKey(devicePublicB64, clientPrivateB64 string) ([]byte, error) {
+	var sharedKey, publicKey, privateKey [32]byte
+	if _, err := hex.Decode(publicKey[:], []byte(devicePublicB64)); err != nil {
+		return nil, err
+	}
+	if _, err := hex.Decode(privateKey[:], []byte(clientPrivateB64)); err != nil {
+		return nil, err
+	}
+	box.Precompute(&sharedKey, &publicKey, &privateKey)
+	return sharedKey[:], nil
+}
+
+func Encode(src, key32 []byte) ([]byte, error) {
+	dst := make([]byte, len(src)+8)
+
+	if _, err := rand.Read(dst[:8]); err != nil {
+		return nil, err
+	}
+
+	nonce12 := make([]byte, 12)
+	copy(nonce12[4:], dst[:8])
+
+	c, err := chacha20.NewUnauthenticatedCipher(key32, nonce12)
+	if err != nil {
+		return nil, err
+	}
+
+	c.XORKeyStream(dst[8:], src)
+
+	return dst, nil
+}
+
+func Decode(src, key32 []byte) ([]byte, error) {
+	return DecodeNonce(src[8:], src[:8], key32)
+}
+
+func DecodeNonce(src, nonce8, key32 []byte) ([]byte, error) {
+	nonce12 := make([]byte, 12)
+	copy(nonce12[4:], nonce8)
+
+	c, err := chacha20.NewUnauthenticatedCipher(key32, nonce12)
+	if err != nil {
+		return nil, err
+	}
+
+	dst := make([]byte, len(src))
+	c.XORKeyStream(dst, src)
+
+	return dst, nil
+}