Web VPN - RDP Connection Closed to Linux server

[jjasoncool]

I use Fortigate web VPN to connect to my Linux host via RDP. My Linux host runs xRDP and utilizes any-vnc to forward the x11vnc screen. I can successfully connect and operate using the SSL VPN tunnel and the Windows RDP tool. However, when using Fortigate's web VPN tool, it forces the connection to close. I have already searched on Google and reviewed previous cases, adjusting encryption methods, but the results remain the same.

My Fortigate: 60E

FortiOS: 7.4.0

Browsers: Chrome, Firefox

Please provide assistance. Additionally, I would like to mention that after updating to FortiOS 7.4.0, the resolution does not automatically adjust. Although there are solutions available on Reddit, I still hope that the official support team can address our issue.

[AEK]

I didn't check the know issues of your 7.4.0 version but at first look I'd recommend to update it to the latest patch.

[jjasoncool]

I have checked the know issues, this issue is not list in.

I've update to latest version. There's no newer patch.

[parteeksharma]

Dear jjasoncool,
Hope you are doing good.
Kindly share the below logs from fortigate cli and then replicate the issue and share us the logs:

diag vpn ssl debug-filter src-addr4 < x.x.x.x > -----> Where x.x.x.x is the user public IP address
diagnose debug application sslvpn -1
diagnose debug enable

* Connect to the VPN SSL
To stop the capture:
diagnose debug disable
diagnose debug reset

Regards,
Parteek

[jjasoncool]

I don't know how to use fortigate cli.

Can you have photos to step by step?

Thank you.

[jjasoncool]

I have try this, but no any output in console.

[AEK]

Try removing app control, IPS, cert inspection and other profiles from the related policy then give it a try.

[jjasoncool]

it's normal to connect to windows server, only linux server has this issue(using packages XRDP and though vnc), I don't think this is policy cause.

And I have no policy to restrict RDP service. Including app control, IPS, cert inspection, it's all by default values.

So, conclusion is:

1. using windows RDP client connect to both Windows/Linux server though ssl-vpn tunnel is OK.

2. using fortigate web ssl-vpn RDP client to Linux server cause connection closed, but it's normal to connect to Windows server.