From 518098ac2b27401c63a6b54bf3f2983b44bdf8ff Mon Sep 17 00:00:00 2001
From: Vladislav Yarmak <vladislav-ex-src@vm-0.com>
Date: Fri, 28 Jul 2023 01:15:48 +0300
Subject: [PATCH] option to disable SNI hide

---
 holaapi.go   |  2 +-
 main.go      |  6 ++++--
 plaintext.go | 10 ++++++++--
 upstream.go  | 12 +++++++++---
 4 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/holaapi.go b/holaapi.go
index 5a19a3d..00e5333 100644
--- a/holaapi.go
+++ b/holaapi.go
@@ -398,7 +398,7 @@ func httpClientWithProxy(agent *FallbackAgent) *http.Client {
 		rootCAs = tlsConfig.RootCAs
 	}
 	if agent != nil {
-		dialer = NewProxyDialer(agent.NetAddr(), agent.Hostname(), rootCAs, nil, dialer)
+		dialer = NewProxyDialer(agent.NetAddr(), agent.Hostname(), rootCAs, nil, true, dialer)
 	}
 	t.DialContext = dialer.DialContext
 	return &http.Client{
diff --git a/main.go b/main.go
index fafc3a6..e97e164 100644
--- a/main.go
+++ b/main.go
@@ -64,6 +64,7 @@ type CLIArgs struct {
 	maxPause                                time.Duration
 	backoffInitial                          time.Duration
 	backoffDeadline                         time.Duration
+	hideSNI                                 bool
 }
 
 func parse_args() CLIArgs {
@@ -93,6 +94,7 @@ func parse_args() CLIArgs {
 		"Format: <http|https|socks5|socks5h>://[login:password@]host[:port] "+
 		"Examples: http://user:password@192.168.1.1:3128, socks5://10.0.0.1:1080")
 	flag.StringVar(&args.caFile, "cafile", "", "use custom CA certificate bundle file")
+	flag.BoolVar(&args.hideSNI, "hide-SNI", true, "hide SNI in TLS sessions with proxy server")
 	flag.Parse()
 	if args.country == "" {
 		arg_fail("Country can't be empty string.")
@@ -215,8 +217,8 @@ func run() int {
 		mainLogger.Critical("Unable to determine proxy endpoint: %v", err)
 		return 5
 	}
-	handlerDialer := NewProxyDialer(endpoint.NetAddr(), endpoint.TLSName, caPool, auth, dialer)
-	requestDialer := NewPlaintextDialer(endpoint.NetAddr(), endpoint.TLSName, caPool, dialer)
+	handlerDialer := NewProxyDialer(endpoint.NetAddr(), endpoint.TLSName, caPool, auth, args.hideSNI, dialer)
+	requestDialer := NewPlaintextDialer(endpoint.NetAddr(), endpoint.TLSName, caPool, args.hideSNI, dialer)
 	mainLogger.Info("Endpoint: %s", endpoint.URL().String())
 	mainLogger.Info("Starting proxy server...")
 	handler := NewProxyHandler(handlerDialer, requestDialer, auth, resolver, proxyLogger)
diff --git a/plaintext.go b/plaintext.go
index 2296322..c186d6c 100644
--- a/plaintext.go
+++ b/plaintext.go
@@ -13,14 +13,16 @@ type PlaintextDialer struct {
 	tlsServerName string
 	next          ContextDialer
 	caPool        *x509.CertPool
+	hideSNI       bool
 }
 
-func NewPlaintextDialer(address, tlsServerName string, caPool *x509.CertPool, next ContextDialer) *PlaintextDialer {
+func NewPlaintextDialer(address, tlsServerName string, caPool *x509.CertPool, hideSNI bool, next ContextDialer) *PlaintextDialer {
 	return &PlaintextDialer{
 		fixedAddress:  address,
 		tlsServerName: tlsServerName,
 		next:          next,
 		caPool:        caPool,
+		hideSNI:       hideSNI,
 	}
 }
 
@@ -40,8 +42,12 @@ func (d *PlaintextDialer) DialContext(ctx context.Context, network, address stri
 		// Custom cert verification logic:
 		// DO NOT send SNI extension of TLS ClientHello
 		// DO peer certificate verification against specified servername
+		sni := d.tlsServerName
+		if d.hideSNI {
+			sni = ""
+		}
 		conn = tls.Client(conn, &tls.Config{
-			ServerName:         "",
+			ServerName:         sni,
 			InsecureSkipVerify: true,
 			VerifyConnection: func(cs tls.ConnectionState) error {
 				opts := x509.VerifyOptions{
diff --git a/upstream.go b/upstream.go
index ca7bebe..eb3b6f2 100644
--- a/upstream.go
+++ b/upstream.go
@@ -39,15 +39,17 @@ type ProxyDialer struct {
 	auth          AuthProvider
 	next          ContextDialer
 	caPool        *x509.CertPool
+	hideSNI       bool
 }
 
-func NewProxyDialer(address, tlsServerName string, caPool *x509.CertPool, auth AuthProvider, nextDialer ContextDialer) *ProxyDialer {
+func NewProxyDialer(address, tlsServerName string, caPool *x509.CertPool, auth AuthProvider, hideSNI bool, nextDialer ContextDialer) *ProxyDialer {
 	return &ProxyDialer{
 		address:       address,
 		tlsServerName: tlsServerName,
 		auth:          auth,
 		next:          nextDialer,
 		caPool:        caPool,
+		hideSNI:       hideSNI,
 	}
 }
 
@@ -81,7 +83,7 @@ func ProxyDialerFromURL(u *url.URL, caPool *x509.CertPool, next ContextDialer) (
 			return authHeader
 		}
 	}
-	return NewProxyDialer(address, tlsServerName, caPool, auth, next), nil
+	return NewProxyDialer(address, tlsServerName, caPool, auth, false, next), nil
 }
 
 func (d *ProxyDialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
@@ -100,8 +102,12 @@ func (d *ProxyDialer) DialContext(ctx context.Context, network, address string)
 		// Custom cert verification logic:
 		// DO NOT send SNI extension of TLS ClientHello
 		// DO peer certificate verification against specified servername
+		sni := d.tlsServerName
+		if d.hideSNI {
+			sni = ""
+		}
 		conn = tls.Client(conn, &tls.Config{
-			ServerName:         "",
+			ServerName:         sni,
 			InsecureSkipVerify: true,
 			VerifyConnection: func(cs tls.ConnectionState) error {
 				opts := x509.VerifyOptions{