From fdcc36dd8d9cb7b3569a3814f70dad5e3671aa35 Mon Sep 17 00:00:00 2001
From: akallabeth <akallabeth@posteo.net>
Date: Fri, 28 Apr 2023 08:23:52 +0200
Subject: [PATCH] [core,connection] relax state machine

contrary to '[MS-RDPBCGR] 1.3.9 Connect-Time and Continuous Network
Characteristics Detection' we have seen autodetection reqeusts mixed in
between licensing messages. This relaxes the state machine and allows
handling.
---
 libfreerdp/core/connection.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/libfreerdp/core/connection.c b/libfreerdp/core/connection.c
index 2eb2ef11a..ca11ef174 100644
--- a/libfreerdp/core/connection.c
+++ b/libfreerdp/core/connection.c
@@ -1109,10 +1109,6 @@ BOOL rdp_client_connect_mcs_channel_join_confirm(rdpRdp* rdp, wStream* s)
 
 BOOL rdp_client_connect_auto_detect(rdpRdp* rdp, wStream* s)
 {
-	size_t pos;
-	UINT16 length;
-	UINT16 channelId;
-
 	WINPR_ASSERT(rdp);
 	WINPR_ASSERT(rdp->mcs);
 
@@ -1121,7 +1117,9 @@ BOOL rdp_client_connect_auto_detect(rdpRdp* rdp, wStream* s)
 	if (messageChannelId != 0)
 	{
 		/* Process any MCS message channel PDUs. */
-		pos = Stream_GetPosition(s);
+		const size_t pos = Stream_GetPosition(s);
+		UINT16 length = 0;
+		UINT16 channelId = 0;
 
 		if (rdp_read_header(rdp, s, &length, &channelId))
 		{
@@ -1172,6 +1170,15 @@ state_run_t rdp_client_connect_license(rdpRdp* rdp, wStream* s)
 			return STATE_RUN_FAILED;
 	}
 
+	/* there might be autodetect messages mixed in between licensing messages.
+	 * that has been observed with 2k12 R2 and 2k19
+	 */
+	const UINT16 messageChannelId = rdp->mcs->messageChannelId;
+	if (channelId == messageChannelId)
+	{
+		return rdp_recv_message_channel_pdu(rdp, s, securityFlags);
+	}
+
 	if ((securityFlags & SEC_LICENSE_PKT) == 0)
 	{
 		char buffer[512] = { 0 };