From 117de1fd3c2703c0c85705e47dc7e93716e97c79 Mon Sep 17 00:00:00 2001
From: RPRX <63339210+RPRX@users.noreply.github.com>
Date: Fri, 7 Feb 2025 08:15:40 +0000
Subject: [PATCH] MITM freedom RAW TLS: Report website with unexpected
 Negotiated Protocol / invalid Domain Fronting certificate

https://github.com/XTLS/Xray-core/issues/4348#issuecomment-2639965524

Needs `"alpn": ["fromMitm"]` / `"verifyPeerCertInNames": ["fromMitm", ...]`.
---
 proxy/dokodemo/dokodemo.go       |  2 +-
 transport/internet/tcp/dialer.go | 42 +++++++++++++++++++-------------
 2 files changed, 26 insertions(+), 18 deletions(-)

diff --git a/proxy/dokodemo/dokodemo.go b/proxy/dokodemo/dokodemo.go
index c16135f5..4fb431f4 100644
--- a/proxy/dokodemo/dokodemo.go
+++ b/proxy/dokodemo/dokodemo.go
@@ -89,7 +89,7 @@ func (d *DokodemoDoor) Process(ctx context.Context, network net.Network, conn st
 				destinationOverridden = true
 				ctx = session.ContextWithMitmServerName(ctx, serverName)
 			}
-			if tlsConn.NegotiatedProtocol() == "http/1.1" {
+			if tlsConn.NegotiatedProtocol() != "h2" {
 				ctx = session.ContextWithMitmAlpn11(ctx, true)
 			}
 		}
diff --git a/transport/internet/tcp/dialer.go b/transport/internet/tcp/dialer.go
index 8d9bbf78..d9fb4aab 100644
--- a/transport/internet/tcp/dialer.go
+++ b/transport/internet/tcp/dialer.go
@@ -33,7 +33,9 @@ func Dial(ctx context.Context, dest net.Destination, streamSettings *internet.Me
 		if IsFromMitm(tlsConfig.ServerName) {
 			tlsConfig.ServerName = mitmServerName
 		}
-		if r, ok := tlsConfig.Rand.(*tls.RandCarrier); ok && len(r.VerifyPeerCertInNames) > 0 && IsFromMitm(r.VerifyPeerCertInNames[0]) {
+		r, ok := tlsConfig.Rand.(*tls.RandCarrier)
+		isFromMitmVerify := ok && len(r.VerifyPeerCertInNames) > 0 && IsFromMitm(r.VerifyPeerCertInNames[0])
+		if isFromMitmVerify {
 			r.VerifyPeerCertInNames = r.VerifyPeerCertInNames[1:]
 			after := mitmServerName
 			for {
@@ -46,29 +48,35 @@ func Dial(ctx context.Context, dest net.Destination, streamSettings *internet.Me
 				}
 			}
 		}
+		isFromMitmAlpn := len(tlsConfig.NextProtos) == 1 && IsFromMitm(tlsConfig.NextProtos[0])
+		if isFromMitmAlpn {
+			if mitmAlpn11 {
+				tlsConfig.NextProtos[0] = "http/1.1"
+			} else {
+				tlsConfig.NextProtos = []string{"h2", "http/1.1"}
+			}
+		}
 		if fingerprint := tls.GetFingerprint(config.Fingerprint); fingerprint != nil {
 			conn = tls.UClient(conn, tlsConfig, fingerprint)
-			if len(tlsConfig.NextProtos) == 1 && (tlsConfig.NextProtos[0] == "http/1.1" || (IsFromMitm(tlsConfig.NextProtos[0]) && mitmAlpn11)) {
-				if err := conn.(*tls.UConn).WebsocketHandshakeContext(ctx); err != nil {
-					return nil, err
-				}
+			if len(tlsConfig.NextProtos) == 1 && tlsConfig.NextProtos[0] == "http/1.1" { // allow manually specify
+				err = conn.(*tls.UConn).WebsocketHandshakeContext(ctx)
 			} else {
-				if err := conn.(*tls.UConn).HandshakeContext(ctx); err != nil {
-					return nil, err
-				}
+				err = conn.(*tls.UConn).HandshakeContext(ctx)
 			}
 		} else {
-			if len(tlsConfig.NextProtos) == 1 && IsFromMitm(tlsConfig.NextProtos[0]) {
-				if mitmAlpn11 {
-					tlsConfig.NextProtos[0] = "http/1.1"
-				} else {
-					tlsConfig.NextProtos = nil
-				}
-			}
 			conn = tls.Client(conn, tlsConfig)
-			if err := conn.(*tls.Conn).HandshakeContext(ctx); err != nil {
-				return nil, err
+			err = conn.(*tls.Conn).HandshakeContext(ctx)
+		}
+		if err != nil {
+			if isFromMitmVerify {
+				return nil, errors.New("MITM freedom RAW TLS: failed to verify Domain Fronting certificate from " + mitmServerName).Base(err).AtWarning()
 			}
+			return nil, err
+		}
+		negotiatedProtocol := conn.(tls.Interface).NegotiatedProtocol()
+		if isFromMitmAlpn && !mitmAlpn11 && negotiatedProtocol != "h2" {
+			conn.Close()
+			return nil, errors.New("MITM freedom RAW TLS: unexpected Negotiated Protocol (" + negotiatedProtocol + ") with " + mitmServerName).AtWarning()
 		}
 	} else if config := reality.ConfigFromStreamSettings(streamSettings); config != nil {
 		if conn, err = reality.UClient(conn, config, ctx, dest); err != nil {