Support default dc idx from configs

wrappers/mtproto_cipher.go

@@ -4,8 +4,8 @@ import (
 	"bytes"
 	"crypto/aes"
 	"crypto/cipher"
-	"crypto/md5" // nolint: gas
-	"crypto/sha1"
+	"crypto/md5"  // nolint: gas
+	"crypto/sha1" // nolint: gosec
 	"encoding/binary"
 	"net"
 
@@ -41,9 +41,9 @@ func NewMiddleProxyCipher(conn StreamReadWriteCloser,
 func deriveKeys(purpose cipherPurpose, req *rpc.NonceRequest, resp *rpc.NonceResponse,
 	client, remote *net.TCPAddr, secret []byte) ([]byte, []byte) {
 	message := bytes.Buffer{}
-	message.Write(resp.Nonce)
-	message.Write(req.Nonce)
-	message.Write(req.CryptoTS)
+	message.Write(resp.Nonce)   // nolint: gosec
+	message.Write(req.Nonce)    // nolint: gosec
+	message.Write(req.CryptoTS) // nolint: gosec
 
 	clientIPv4 := emptyIP[:]
 	serverIPv4 := emptyIP[:]
@@ -51,36 +51,36 @@ func deriveKeys(purpose cipherPurpose, req *rpc.NonceRequest, resp *rpc.NonceRes
 		clientIPv4 = utils.ReverseBytes(client.IP.To4())
 		serverIPv4 = utils.ReverseBytes(remote.IP.To4())
 	}
-	message.Write(serverIPv4)
+	message.Write(serverIPv4) // nolint: gosec
 
 	var port [2]byte
 	binary.LittleEndian.PutUint16(port[:], uint16(client.Port))
-	message.Write(port[:])
+	message.Write(port[:]) // nolint: gosec
 
 	switch purpose {
 	case cipherPurposeClient:
-		message.WriteString("CLIENT")
+		message.WriteString("CLIENT") // nolint: gosec
 	case cipherPurposeServer:
-		message.WriteString("SERVER")
+		message.WriteString("SERVER") // nolint: gosec
 	default:
 		panic("Unexpected cipher purpose")
 	}
 
-	message.Write(clientIPv4)
+	message.Write(clientIPv4) // nolint: gosec
 	binary.LittleEndian.PutUint16(port[:], uint16(remote.Port))
-	message.Write(port[:])
-	message.Write(secret)
-	message.Write(resp.Nonce)
+	message.Write(port[:])    // nolint: gosec
+	message.Write(secret)     // nolint: gosec
+	message.Write(resp.Nonce) // nolint: gosec
 
 	if client.IP.To4() == nil {
-		message.Write(client.IP.To16())
-		message.Write(remote.IP.To16())
+		message.Write(client.IP.To16()) // nolint: gosec
+		message.Write(remote.IP.To16()) // nolint: gosec
 	}
-	message.Write(req.Nonce)
+	message.Write(req.Nonce) // nolint: gosec
 
 	data := message.Bytes()
 	md5sum := md5.Sum(data[1:]) // nolint: gas
-	sha1sum := sha1.Sum(data)
+	sha1sum := sha1.Sum(data)   // nolint: gosec
 
 	key := append(md5sum[:12], sha1sum[:]...)
 	iv := md5.Sum(data[2:]) // nolint: gas